11da177e4SLinus Torvalds /* 21da177e4SLinus Torvalds * linux/fs/namespace.c 31da177e4SLinus Torvalds * 41da177e4SLinus Torvalds * (C) Copyright Al Viro 2000, 2001 51da177e4SLinus Torvalds * Released under GPL v2. 61da177e4SLinus Torvalds * 71da177e4SLinus Torvalds * Based on code from fs/super.c, copyright Linus Torvalds and others. 81da177e4SLinus Torvalds * Heavily rewritten. 91da177e4SLinus Torvalds */ 101da177e4SLinus Torvalds 111da177e4SLinus Torvalds #include <linux/syscalls.h> 12d10577a8SAl Viro #include <linux/export.h> 1316f7e0feSRandy Dunlap #include <linux/capability.h> 146b3286edSKirill Korotaev #include <linux/mnt_namespace.h> 15771b1371SEric W. Biederman #include <linux/user_namespace.h> 161da177e4SLinus Torvalds #include <linux/namei.h> 171da177e4SLinus Torvalds #include <linux/security.h> 185b825c3aSIngo Molnar #include <linux/cred.h> 1973cd49ecSMiklos Szeredi #include <linux/idr.h> 2057f150a5SRob Landley #include <linux/init.h> /* init_rootfs */ 21d10577a8SAl Viro #include <linux/fs_struct.h> /* get_fs_root et.al. */ 22d10577a8SAl Viro #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */ 23d10577a8SAl Viro #include <linux/uaccess.h> 240bb80f24SDavid Howells #include <linux/proc_ns.h> 2520b4fb48SLinus Torvalds #include <linux/magic.h> 260818bf27SAl Viro #include <linux/bootmem.h> 279ea459e1SAl Viro #include <linux/task_work.h> 289164bb4aSIngo Molnar #include <linux/sched/task.h> 299164bb4aSIngo Molnar 3007b20889SRam Pai #include "pnode.h" 31948730b0SAdrian Bunk #include "internal.h" 321da177e4SLinus Torvalds 33d2921684SEric W. Biederman /* Maximum number of mounts in a mount namespace */ 34d2921684SEric W. Biederman unsigned int sysctl_mount_max __read_mostly = 100000; 35d2921684SEric W. Biederman 360818bf27SAl Viro static unsigned int m_hash_mask __read_mostly; 370818bf27SAl Viro static unsigned int m_hash_shift __read_mostly; 380818bf27SAl Viro static unsigned int mp_hash_mask __read_mostly; 390818bf27SAl Viro static unsigned int mp_hash_shift __read_mostly; 400818bf27SAl Viro 410818bf27SAl Viro static __initdata unsigned long mhash_entries; 420818bf27SAl Viro static int __init set_mhash_entries(char *str) 430818bf27SAl Viro { 440818bf27SAl Viro if (!str) 450818bf27SAl Viro return 0; 460818bf27SAl Viro mhash_entries = simple_strtoul(str, &str, 0); 470818bf27SAl Viro return 1; 480818bf27SAl Viro } 490818bf27SAl Viro __setup("mhash_entries=", set_mhash_entries); 500818bf27SAl Viro 510818bf27SAl Viro static __initdata unsigned long mphash_entries; 520818bf27SAl Viro static int __init set_mphash_entries(char *str) 530818bf27SAl Viro { 540818bf27SAl Viro if (!str) 550818bf27SAl Viro return 0; 560818bf27SAl Viro mphash_entries = simple_strtoul(str, &str, 0); 570818bf27SAl Viro return 1; 580818bf27SAl Viro } 590818bf27SAl Viro __setup("mphash_entries=", set_mphash_entries); 6013f14b4dSEric Dumazet 61c7999c36SAl Viro static u64 event; 6273cd49ecSMiklos Szeredi static DEFINE_IDA(mnt_id_ida); 63719f5d7fSMiklos Szeredi static DEFINE_IDA(mnt_group_ida); 6499b7db7bSNick Piggin static DEFINE_SPINLOCK(mnt_id_lock); 65f21f6220SAl Viro static int mnt_id_start = 0; 66f21f6220SAl Viro static int mnt_group_start = 1; 675addc5ddSAl Viro 6838129a13SAl Viro static struct hlist_head *mount_hashtable __read_mostly; 690818bf27SAl Viro static struct hlist_head *mountpoint_hashtable __read_mostly; 70e18b890bSChristoph Lameter static struct kmem_cache *mnt_cache __read_mostly; 7159aa0da8SAl Viro static DECLARE_RWSEM(namespace_sem); 721da177e4SLinus Torvalds 73f87fd4c2SMiklos Szeredi /* /sys/fs */ 7400d26666SGreg Kroah-Hartman struct kobject *fs_kobj; 7500d26666SGreg Kroah-Hartman EXPORT_SYMBOL_GPL(fs_kobj); 76f87fd4c2SMiklos Szeredi 7799b7db7bSNick Piggin /* 7899b7db7bSNick Piggin * vfsmount lock may be taken for read to prevent changes to the 7999b7db7bSNick Piggin * vfsmount hash, ie. during mountpoint lookups or walking back 8099b7db7bSNick Piggin * up the tree. 8199b7db7bSNick Piggin * 8299b7db7bSNick Piggin * It should be taken for write in all cases where the vfsmount 8399b7db7bSNick Piggin * tree or hash is modified or when a vfsmount structure is modified. 8499b7db7bSNick Piggin */ 8548a066e7SAl Viro __cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock); 8699b7db7bSNick Piggin 8738129a13SAl Viro static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry) 881da177e4SLinus Torvalds { 891da177e4SLinus Torvalds unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); 901da177e4SLinus Torvalds tmp += ((unsigned long)dentry / L1_CACHE_BYTES); 910818bf27SAl Viro tmp = tmp + (tmp >> m_hash_shift); 920818bf27SAl Viro return &mount_hashtable[tmp & m_hash_mask]; 930818bf27SAl Viro } 940818bf27SAl Viro 950818bf27SAl Viro static inline struct hlist_head *mp_hash(struct dentry *dentry) 960818bf27SAl Viro { 970818bf27SAl Viro unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES); 980818bf27SAl Viro tmp = tmp + (tmp >> mp_hash_shift); 990818bf27SAl Viro return &mountpoint_hashtable[tmp & mp_hash_mask]; 1001da177e4SLinus Torvalds } 1011da177e4SLinus Torvalds 102b105e270SAl Viro static int mnt_alloc_id(struct mount *mnt) 10373cd49ecSMiklos Szeredi { 10473cd49ecSMiklos Szeredi int res; 10573cd49ecSMiklos Szeredi 10673cd49ecSMiklos Szeredi retry: 10773cd49ecSMiklos Szeredi ida_pre_get(&mnt_id_ida, GFP_KERNEL); 10899b7db7bSNick Piggin spin_lock(&mnt_id_lock); 10915169fe7SAl Viro res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id); 110f21f6220SAl Viro if (!res) 11115169fe7SAl Viro mnt_id_start = mnt->mnt_id + 1; 11299b7db7bSNick Piggin spin_unlock(&mnt_id_lock); 11373cd49ecSMiklos Szeredi if (res == -EAGAIN) 11473cd49ecSMiklos Szeredi goto retry; 11573cd49ecSMiklos Szeredi 11673cd49ecSMiklos Szeredi return res; 11773cd49ecSMiklos Szeredi } 11873cd49ecSMiklos Szeredi 119b105e270SAl Viro static void mnt_free_id(struct mount *mnt) 12073cd49ecSMiklos Szeredi { 12115169fe7SAl Viro int id = mnt->mnt_id; 12299b7db7bSNick Piggin spin_lock(&mnt_id_lock); 123f21f6220SAl Viro ida_remove(&mnt_id_ida, id); 124f21f6220SAl Viro if (mnt_id_start > id) 125f21f6220SAl Viro mnt_id_start = id; 12699b7db7bSNick Piggin spin_unlock(&mnt_id_lock); 12773cd49ecSMiklos Szeredi } 12873cd49ecSMiklos Szeredi 129719f5d7fSMiklos Szeredi /* 130719f5d7fSMiklos Szeredi * Allocate a new peer group ID 131719f5d7fSMiklos Szeredi * 132719f5d7fSMiklos Szeredi * mnt_group_ida is protected by namespace_sem 133719f5d7fSMiklos Szeredi */ 1344b8b21f4SAl Viro static int mnt_alloc_group_id(struct mount *mnt) 135719f5d7fSMiklos Szeredi { 136f21f6220SAl Viro int res; 137f21f6220SAl Viro 138719f5d7fSMiklos Szeredi if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL)) 139719f5d7fSMiklos Szeredi return -ENOMEM; 140719f5d7fSMiklos Szeredi 141f21f6220SAl Viro res = ida_get_new_above(&mnt_group_ida, 142f21f6220SAl Viro mnt_group_start, 14315169fe7SAl Viro &mnt->mnt_group_id); 144f21f6220SAl Viro if (!res) 14515169fe7SAl Viro mnt_group_start = mnt->mnt_group_id + 1; 146f21f6220SAl Viro 147f21f6220SAl Viro return res; 148719f5d7fSMiklos Szeredi } 149719f5d7fSMiklos Szeredi 150719f5d7fSMiklos Szeredi /* 151719f5d7fSMiklos Szeredi * Release a peer group ID 152719f5d7fSMiklos Szeredi */ 1534b8b21f4SAl Viro void mnt_release_group_id(struct mount *mnt) 154719f5d7fSMiklos Szeredi { 15515169fe7SAl Viro int id = mnt->mnt_group_id; 156f21f6220SAl Viro ida_remove(&mnt_group_ida, id); 157f21f6220SAl Viro if (mnt_group_start > id) 158f21f6220SAl Viro mnt_group_start = id; 15915169fe7SAl Viro mnt->mnt_group_id = 0; 160719f5d7fSMiklos Szeredi } 161719f5d7fSMiklos Szeredi 162b3e19d92SNick Piggin /* 163b3e19d92SNick Piggin * vfsmount lock must be held for read 164b3e19d92SNick Piggin */ 16583adc753SAl Viro static inline void mnt_add_count(struct mount *mnt, int n) 166b3e19d92SNick Piggin { 167b3e19d92SNick Piggin #ifdef CONFIG_SMP 16868e8a9feSAl Viro this_cpu_add(mnt->mnt_pcp->mnt_count, n); 169b3e19d92SNick Piggin #else 170b3e19d92SNick Piggin preempt_disable(); 17168e8a9feSAl Viro mnt->mnt_count += n; 172b3e19d92SNick Piggin preempt_enable(); 173b3e19d92SNick Piggin #endif 174b3e19d92SNick Piggin } 175b3e19d92SNick Piggin 176b3e19d92SNick Piggin /* 177b3e19d92SNick Piggin * vfsmount lock must be held for write 178b3e19d92SNick Piggin */ 17983adc753SAl Viro unsigned int mnt_get_count(struct mount *mnt) 180b3e19d92SNick Piggin { 181b3e19d92SNick Piggin #ifdef CONFIG_SMP 182f03c6599SAl Viro unsigned int count = 0; 183b3e19d92SNick Piggin int cpu; 184b3e19d92SNick Piggin 185b3e19d92SNick Piggin for_each_possible_cpu(cpu) { 18668e8a9feSAl Viro count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count; 187b3e19d92SNick Piggin } 188b3e19d92SNick Piggin 189b3e19d92SNick Piggin return count; 190b3e19d92SNick Piggin #else 19168e8a9feSAl Viro return mnt->mnt_count; 192b3e19d92SNick Piggin #endif 193b3e19d92SNick Piggin } 194b3e19d92SNick Piggin 19587b95ce0SAl Viro static void drop_mountpoint(struct fs_pin *p) 19687b95ce0SAl Viro { 19787b95ce0SAl Viro struct mount *m = container_of(p, struct mount, mnt_umount); 19887b95ce0SAl Viro dput(m->mnt_ex_mountpoint); 19987b95ce0SAl Viro pin_remove(p); 20087b95ce0SAl Viro mntput(&m->mnt); 20187b95ce0SAl Viro } 20287b95ce0SAl Viro 203b105e270SAl Viro static struct mount *alloc_vfsmnt(const char *name) 2041da177e4SLinus Torvalds { 205c63181e6SAl Viro struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); 206c63181e6SAl Viro if (mnt) { 20773cd49ecSMiklos Szeredi int err; 20873cd49ecSMiklos Szeredi 209c63181e6SAl Viro err = mnt_alloc_id(mnt); 21088b38782SLi Zefan if (err) 21188b38782SLi Zefan goto out_free_cache; 21288b38782SLi Zefan 21388b38782SLi Zefan if (name) { 214fcc139aeSAndrzej Hajda mnt->mnt_devname = kstrdup_const(name, GFP_KERNEL); 215c63181e6SAl Viro if (!mnt->mnt_devname) 21688b38782SLi Zefan goto out_free_id; 21773cd49ecSMiklos Szeredi } 21873cd49ecSMiklos Szeredi 219b3e19d92SNick Piggin #ifdef CONFIG_SMP 220c63181e6SAl Viro mnt->mnt_pcp = alloc_percpu(struct mnt_pcp); 221c63181e6SAl Viro if (!mnt->mnt_pcp) 222b3e19d92SNick Piggin goto out_free_devname; 223b3e19d92SNick Piggin 224c63181e6SAl Viro this_cpu_add(mnt->mnt_pcp->mnt_count, 1); 225b3e19d92SNick Piggin #else 226c63181e6SAl Viro mnt->mnt_count = 1; 227c63181e6SAl Viro mnt->mnt_writers = 0; 228b3e19d92SNick Piggin #endif 229b3e19d92SNick Piggin 23038129a13SAl Viro INIT_HLIST_NODE(&mnt->mnt_hash); 231c63181e6SAl Viro INIT_LIST_HEAD(&mnt->mnt_child); 232c63181e6SAl Viro INIT_LIST_HEAD(&mnt->mnt_mounts); 233c63181e6SAl Viro INIT_LIST_HEAD(&mnt->mnt_list); 234c63181e6SAl Viro INIT_LIST_HEAD(&mnt->mnt_expire); 235c63181e6SAl Viro INIT_LIST_HEAD(&mnt->mnt_share); 236c63181e6SAl Viro INIT_LIST_HEAD(&mnt->mnt_slave_list); 237c63181e6SAl Viro INIT_LIST_HEAD(&mnt->mnt_slave); 2380a5eb7c8SEric W. Biederman INIT_HLIST_NODE(&mnt->mnt_mp_list); 23999b19d16SEric W. Biederman INIT_LIST_HEAD(&mnt->mnt_umounting); 24087b95ce0SAl Viro init_fs_pin(&mnt->mnt_umount, drop_mountpoint); 2411da177e4SLinus Torvalds } 242c63181e6SAl Viro return mnt; 24388b38782SLi Zefan 244d3ef3d73Snpiggin@suse.de #ifdef CONFIG_SMP 245d3ef3d73Snpiggin@suse.de out_free_devname: 246fcc139aeSAndrzej Hajda kfree_const(mnt->mnt_devname); 247d3ef3d73Snpiggin@suse.de #endif 24888b38782SLi Zefan out_free_id: 249c63181e6SAl Viro mnt_free_id(mnt); 25088b38782SLi Zefan out_free_cache: 251c63181e6SAl Viro kmem_cache_free(mnt_cache, mnt); 25288b38782SLi Zefan return NULL; 2531da177e4SLinus Torvalds } 2541da177e4SLinus Torvalds 2558366025eSDave Hansen /* 2568366025eSDave Hansen * Most r/o checks on a fs are for operations that take 2578366025eSDave Hansen * discrete amounts of time, like a write() or unlink(). 2588366025eSDave Hansen * We must keep track of when those operations start 2598366025eSDave Hansen * (for permission checks) and when they end, so that 2608366025eSDave Hansen * we can determine when writes are able to occur to 2618366025eSDave Hansen * a filesystem. 2628366025eSDave Hansen */ 2633d733633SDave Hansen /* 2643d733633SDave Hansen * __mnt_is_readonly: check whether a mount is read-only 2653d733633SDave Hansen * @mnt: the mount to check for its write status 2663d733633SDave Hansen * 2673d733633SDave Hansen * This shouldn't be used directly ouside of the VFS. 2683d733633SDave Hansen * It does not guarantee that the filesystem will stay 2693d733633SDave Hansen * r/w, just that it is right *now*. This can not and 2703d733633SDave Hansen * should not be used in place of IS_RDONLY(inode). 2713d733633SDave Hansen * mnt_want/drop_write() will _keep_ the filesystem 2723d733633SDave Hansen * r/w. 2733d733633SDave Hansen */ 2743d733633SDave Hansen int __mnt_is_readonly(struct vfsmount *mnt) 2753d733633SDave Hansen { 2762e4b7fcdSDave Hansen if (mnt->mnt_flags & MNT_READONLY) 2772e4b7fcdSDave Hansen return 1; 278bc98a42cSDavid Howells if (sb_rdonly(mnt->mnt_sb)) 2792e4b7fcdSDave Hansen return 1; 2802e4b7fcdSDave Hansen return 0; 2813d733633SDave Hansen } 2823d733633SDave Hansen EXPORT_SYMBOL_GPL(__mnt_is_readonly); 2833d733633SDave Hansen 28483adc753SAl Viro static inline void mnt_inc_writers(struct mount *mnt) 2853d733633SDave Hansen { 286d3ef3d73Snpiggin@suse.de #ifdef CONFIG_SMP 28768e8a9feSAl Viro this_cpu_inc(mnt->mnt_pcp->mnt_writers); 288d3ef3d73Snpiggin@suse.de #else 28968e8a9feSAl Viro mnt->mnt_writers++; 290d3ef3d73Snpiggin@suse.de #endif 2913d733633SDave Hansen } 2923d733633SDave Hansen 29383adc753SAl Viro static inline void mnt_dec_writers(struct mount *mnt) 2943d733633SDave Hansen { 295d3ef3d73Snpiggin@suse.de #ifdef CONFIG_SMP 29668e8a9feSAl Viro this_cpu_dec(mnt->mnt_pcp->mnt_writers); 297d3ef3d73Snpiggin@suse.de #else 29868e8a9feSAl Viro mnt->mnt_writers--; 299d3ef3d73Snpiggin@suse.de #endif 300d3ef3d73Snpiggin@suse.de } 301d3ef3d73Snpiggin@suse.de 30283adc753SAl Viro static unsigned int mnt_get_writers(struct mount *mnt) 303d3ef3d73Snpiggin@suse.de { 304d3ef3d73Snpiggin@suse.de #ifdef CONFIG_SMP 305d3ef3d73Snpiggin@suse.de unsigned int count = 0; 3063d733633SDave Hansen int cpu; 3073d733633SDave Hansen 3083d733633SDave Hansen for_each_possible_cpu(cpu) { 30968e8a9feSAl Viro count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers; 3103d733633SDave Hansen } 3113d733633SDave Hansen 312d3ef3d73Snpiggin@suse.de return count; 313d3ef3d73Snpiggin@suse.de #else 314d3ef3d73Snpiggin@suse.de return mnt->mnt_writers; 315d3ef3d73Snpiggin@suse.de #endif 3163d733633SDave Hansen } 3173d733633SDave Hansen 3184ed5e82fSMiklos Szeredi static int mnt_is_readonly(struct vfsmount *mnt) 3194ed5e82fSMiklos Szeredi { 3204ed5e82fSMiklos Szeredi if (mnt->mnt_sb->s_readonly_remount) 3214ed5e82fSMiklos Szeredi return 1; 3224ed5e82fSMiklos Szeredi /* Order wrt setting s_flags/s_readonly_remount in do_remount() */ 3234ed5e82fSMiklos Szeredi smp_rmb(); 3244ed5e82fSMiklos Szeredi return __mnt_is_readonly(mnt); 3254ed5e82fSMiklos Szeredi } 3264ed5e82fSMiklos Szeredi 3273d733633SDave Hansen /* 328eb04c282SJan Kara * Most r/o & frozen checks on a fs are for operations that take discrete 329eb04c282SJan Kara * amounts of time, like a write() or unlink(). We must keep track of when 330eb04c282SJan Kara * those operations start (for permission checks) and when they end, so that we 331eb04c282SJan Kara * can determine when writes are able to occur to a filesystem. 3323d733633SDave Hansen */ 3338366025eSDave Hansen /** 334eb04c282SJan Kara * __mnt_want_write - get write access to a mount without freeze protection 33583adc753SAl Viro * @m: the mount on which to take a write 3368366025eSDave Hansen * 337eb04c282SJan Kara * This tells the low-level filesystem that a write is about to be performed to 338eb04c282SJan Kara * it, and makes sure that writes are allowed (mnt it read-write) before 339eb04c282SJan Kara * returning success. This operation does not protect against filesystem being 340eb04c282SJan Kara * frozen. When the write operation is finished, __mnt_drop_write() must be 341eb04c282SJan Kara * called. This is effectively a refcount. 3428366025eSDave Hansen */ 343eb04c282SJan Kara int __mnt_want_write(struct vfsmount *m) 3448366025eSDave Hansen { 34583adc753SAl Viro struct mount *mnt = real_mount(m); 3463d733633SDave Hansen int ret = 0; 3473d733633SDave Hansen 348d3ef3d73Snpiggin@suse.de preempt_disable(); 349c6653a83SNick Piggin mnt_inc_writers(mnt); 350d3ef3d73Snpiggin@suse.de /* 351c6653a83SNick Piggin * The store to mnt_inc_writers must be visible before we pass 352d3ef3d73Snpiggin@suse.de * MNT_WRITE_HOLD loop below, so that the slowpath can see our 353d3ef3d73Snpiggin@suse.de * incremented count after it has set MNT_WRITE_HOLD. 354d3ef3d73Snpiggin@suse.de */ 355d3ef3d73Snpiggin@suse.de smp_mb(); 3566aa7de05SMark Rutland while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) 357d3ef3d73Snpiggin@suse.de cpu_relax(); 358d3ef3d73Snpiggin@suse.de /* 359d3ef3d73Snpiggin@suse.de * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will 360d3ef3d73Snpiggin@suse.de * be set to match its requirements. So we must not load that until 361d3ef3d73Snpiggin@suse.de * MNT_WRITE_HOLD is cleared. 362d3ef3d73Snpiggin@suse.de */ 363d3ef3d73Snpiggin@suse.de smp_rmb(); 3644ed5e82fSMiklos Szeredi if (mnt_is_readonly(m)) { 365c6653a83SNick Piggin mnt_dec_writers(mnt); 3663d733633SDave Hansen ret = -EROFS; 3673d733633SDave Hansen } 368d3ef3d73Snpiggin@suse.de preempt_enable(); 369eb04c282SJan Kara 370eb04c282SJan Kara return ret; 371eb04c282SJan Kara } 372eb04c282SJan Kara 373eb04c282SJan Kara /** 374eb04c282SJan Kara * mnt_want_write - get write access to a mount 375eb04c282SJan Kara * @m: the mount on which to take a write 376eb04c282SJan Kara * 377eb04c282SJan Kara * This tells the low-level filesystem that a write is about to be performed to 378eb04c282SJan Kara * it, and makes sure that writes are allowed (mount is read-write, filesystem 379eb04c282SJan Kara * is not frozen) before returning success. When the write operation is 380eb04c282SJan Kara * finished, mnt_drop_write() must be called. This is effectively a refcount. 381eb04c282SJan Kara */ 382eb04c282SJan Kara int mnt_want_write(struct vfsmount *m) 383eb04c282SJan Kara { 384eb04c282SJan Kara int ret; 385eb04c282SJan Kara 386eb04c282SJan Kara sb_start_write(m->mnt_sb); 387eb04c282SJan Kara ret = __mnt_want_write(m); 388eb04c282SJan Kara if (ret) 389eb04c282SJan Kara sb_end_write(m->mnt_sb); 3903d733633SDave Hansen return ret; 3918366025eSDave Hansen } 3928366025eSDave Hansen EXPORT_SYMBOL_GPL(mnt_want_write); 3938366025eSDave Hansen 3948366025eSDave Hansen /** 39596029c4eSnpiggin@suse.de * mnt_clone_write - get write access to a mount 39696029c4eSnpiggin@suse.de * @mnt: the mount on which to take a write 39796029c4eSnpiggin@suse.de * 39896029c4eSnpiggin@suse.de * This is effectively like mnt_want_write, except 39996029c4eSnpiggin@suse.de * it must only be used to take an extra write reference 40096029c4eSnpiggin@suse.de * on a mountpoint that we already know has a write reference 40196029c4eSnpiggin@suse.de * on it. This allows some optimisation. 40296029c4eSnpiggin@suse.de * 40396029c4eSnpiggin@suse.de * After finished, mnt_drop_write must be called as usual to 40496029c4eSnpiggin@suse.de * drop the reference. 40596029c4eSnpiggin@suse.de */ 40696029c4eSnpiggin@suse.de int mnt_clone_write(struct vfsmount *mnt) 40796029c4eSnpiggin@suse.de { 40896029c4eSnpiggin@suse.de /* superblock may be r/o */ 40996029c4eSnpiggin@suse.de if (__mnt_is_readonly(mnt)) 41096029c4eSnpiggin@suse.de return -EROFS; 41196029c4eSnpiggin@suse.de preempt_disable(); 41283adc753SAl Viro mnt_inc_writers(real_mount(mnt)); 41396029c4eSnpiggin@suse.de preempt_enable(); 41496029c4eSnpiggin@suse.de return 0; 41596029c4eSnpiggin@suse.de } 41696029c4eSnpiggin@suse.de EXPORT_SYMBOL_GPL(mnt_clone_write); 41796029c4eSnpiggin@suse.de 41896029c4eSnpiggin@suse.de /** 419eb04c282SJan Kara * __mnt_want_write_file - get write access to a file's mount 420eb04c282SJan Kara * @file: the file who's mount on which to take a write 421eb04c282SJan Kara * 422eb04c282SJan Kara * This is like __mnt_want_write, but it takes a file and can 423eb04c282SJan Kara * do some optimisations if the file is open for write already 424eb04c282SJan Kara */ 425eb04c282SJan Kara int __mnt_want_write_file(struct file *file) 426eb04c282SJan Kara { 42783f936c7SAl Viro if (!(file->f_mode & FMODE_WRITER)) 428eb04c282SJan Kara return __mnt_want_write(file->f_path.mnt); 429eb04c282SJan Kara else 430eb04c282SJan Kara return mnt_clone_write(file->f_path.mnt); 431eb04c282SJan Kara } 432eb04c282SJan Kara 433eb04c282SJan Kara /** 4347c6893e3SMiklos Szeredi * mnt_want_write_file_path - get write access to a file's mount 43596029c4eSnpiggin@suse.de * @file: the file who's mount on which to take a write 43696029c4eSnpiggin@suse.de * 43796029c4eSnpiggin@suse.de * This is like mnt_want_write, but it takes a file and can 43896029c4eSnpiggin@suse.de * do some optimisations if the file is open for write already 4397c6893e3SMiklos Szeredi * 4407c6893e3SMiklos Szeredi * Called by the vfs for cases when we have an open file at hand, but will do an 4417c6893e3SMiklos Szeredi * inode operation on it (important distinction for files opened on overlayfs, 4427c6893e3SMiklos Szeredi * since the file operations will come from the real underlying file, while 4437c6893e3SMiklos Szeredi * inode operations come from the overlay). 44496029c4eSnpiggin@suse.de */ 4457c6893e3SMiklos Szeredi int mnt_want_write_file_path(struct file *file) 44696029c4eSnpiggin@suse.de { 447eb04c282SJan Kara int ret; 448eb04c282SJan Kara 449eb04c282SJan Kara sb_start_write(file->f_path.mnt->mnt_sb); 450eb04c282SJan Kara ret = __mnt_want_write_file(file); 451eb04c282SJan Kara if (ret) 452eb04c282SJan Kara sb_end_write(file->f_path.mnt->mnt_sb); 453eb04c282SJan Kara return ret; 45496029c4eSnpiggin@suse.de } 4557c6893e3SMiklos Szeredi 4567c6893e3SMiklos Szeredi static inline int may_write_real(struct file *file) 4577c6893e3SMiklos Szeredi { 4587c6893e3SMiklos Szeredi struct dentry *dentry = file->f_path.dentry; 4597c6893e3SMiklos Szeredi struct dentry *upperdentry; 4607c6893e3SMiklos Szeredi 4617c6893e3SMiklos Szeredi /* Writable file? */ 4627c6893e3SMiklos Szeredi if (file->f_mode & FMODE_WRITER) 4637c6893e3SMiklos Szeredi return 0; 4647c6893e3SMiklos Szeredi 4657c6893e3SMiklos Szeredi /* Not overlayfs? */ 4667c6893e3SMiklos Szeredi if (likely(!(dentry->d_flags & DCACHE_OP_REAL))) 4677c6893e3SMiklos Szeredi return 0; 4687c6893e3SMiklos Szeredi 4697c6893e3SMiklos Szeredi /* File refers to upper, writable layer? */ 4707c6893e3SMiklos Szeredi upperdentry = d_real(dentry, NULL, 0, D_REAL_UPPER); 471954c736fSAmir Goldstein if (upperdentry && 472954c736fSAmir Goldstein (file_inode(file) == d_inode(upperdentry) || 473954c736fSAmir Goldstein file_inode(file) == d_inode(dentry))) 4747c6893e3SMiklos Szeredi return 0; 4757c6893e3SMiklos Szeredi 4767c6893e3SMiklos Szeredi /* Lower layer: can't write to real file, sorry... */ 4777c6893e3SMiklos Szeredi return -EPERM; 4787c6893e3SMiklos Szeredi } 4797c6893e3SMiklos Szeredi 4807c6893e3SMiklos Szeredi /** 4817c6893e3SMiklos Szeredi * mnt_want_write_file - get write access to a file's mount 4827c6893e3SMiklos Szeredi * @file: the file who's mount on which to take a write 4837c6893e3SMiklos Szeredi * 4847c6893e3SMiklos Szeredi * This is like mnt_want_write, but it takes a file and can 4857c6893e3SMiklos Szeredi * do some optimisations if the file is open for write already 4867c6893e3SMiklos Szeredi * 4877c6893e3SMiklos Szeredi * Mostly called by filesystems from their ioctl operation before performing 4887c6893e3SMiklos Szeredi * modification. On overlayfs this needs to check if the file is on a read-only 4897c6893e3SMiklos Szeredi * lower layer and deny access in that case. 4907c6893e3SMiklos Szeredi */ 4917c6893e3SMiklos Szeredi int mnt_want_write_file(struct file *file) 4927c6893e3SMiklos Szeredi { 4937c6893e3SMiklos Szeredi int ret; 4947c6893e3SMiklos Szeredi 4957c6893e3SMiklos Szeredi ret = may_write_real(file); 4967c6893e3SMiklos Szeredi if (!ret) { 4977c6893e3SMiklos Szeredi sb_start_write(file_inode(file)->i_sb); 4987c6893e3SMiklos Szeredi ret = __mnt_want_write_file(file); 4997c6893e3SMiklos Szeredi if (ret) 5007c6893e3SMiklos Szeredi sb_end_write(file_inode(file)->i_sb); 5017c6893e3SMiklos Szeredi } 5027c6893e3SMiklos Szeredi return ret; 5037c6893e3SMiklos Szeredi } 50496029c4eSnpiggin@suse.de EXPORT_SYMBOL_GPL(mnt_want_write_file); 50596029c4eSnpiggin@suse.de 50696029c4eSnpiggin@suse.de /** 507eb04c282SJan Kara * __mnt_drop_write - give up write access to a mount 5088366025eSDave Hansen * @mnt: the mount on which to give up write access 5098366025eSDave Hansen * 5108366025eSDave Hansen * Tells the low-level filesystem that we are done 5118366025eSDave Hansen * performing writes to it. Must be matched with 512eb04c282SJan Kara * __mnt_want_write() call above. 5138366025eSDave Hansen */ 514eb04c282SJan Kara void __mnt_drop_write(struct vfsmount *mnt) 5158366025eSDave Hansen { 516d3ef3d73Snpiggin@suse.de preempt_disable(); 51783adc753SAl Viro mnt_dec_writers(real_mount(mnt)); 518d3ef3d73Snpiggin@suse.de preempt_enable(); 5198366025eSDave Hansen } 520eb04c282SJan Kara 521eb04c282SJan Kara /** 522eb04c282SJan Kara * mnt_drop_write - give up write access to a mount 523eb04c282SJan Kara * @mnt: the mount on which to give up write access 524eb04c282SJan Kara * 525eb04c282SJan Kara * Tells the low-level filesystem that we are done performing writes to it and 526eb04c282SJan Kara * also allows filesystem to be frozen again. Must be matched with 527eb04c282SJan Kara * mnt_want_write() call above. 528eb04c282SJan Kara */ 529eb04c282SJan Kara void mnt_drop_write(struct vfsmount *mnt) 530eb04c282SJan Kara { 531eb04c282SJan Kara __mnt_drop_write(mnt); 532eb04c282SJan Kara sb_end_write(mnt->mnt_sb); 533eb04c282SJan Kara } 5348366025eSDave Hansen EXPORT_SYMBOL_GPL(mnt_drop_write); 5358366025eSDave Hansen 536eb04c282SJan Kara void __mnt_drop_write_file(struct file *file) 537eb04c282SJan Kara { 538eb04c282SJan Kara __mnt_drop_write(file->f_path.mnt); 539eb04c282SJan Kara } 540eb04c282SJan Kara 5417c6893e3SMiklos Szeredi void mnt_drop_write_file_path(struct file *file) 5422a79f17eSAl Viro { 5432a79f17eSAl Viro mnt_drop_write(file->f_path.mnt); 5442a79f17eSAl Viro } 5457c6893e3SMiklos Szeredi 5467c6893e3SMiklos Szeredi void mnt_drop_write_file(struct file *file) 5477c6893e3SMiklos Szeredi { 5487c6893e3SMiklos Szeredi __mnt_drop_write(file->f_path.mnt); 5497c6893e3SMiklos Szeredi sb_end_write(file_inode(file)->i_sb); 5507c6893e3SMiklos Szeredi } 5512a79f17eSAl Viro EXPORT_SYMBOL(mnt_drop_write_file); 5522a79f17eSAl Viro 55383adc753SAl Viro static int mnt_make_readonly(struct mount *mnt) 5548366025eSDave Hansen { 5553d733633SDave Hansen int ret = 0; 5563d733633SDave Hansen 557719ea2fbSAl Viro lock_mount_hash(); 55883adc753SAl Viro mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; 559d3ef3d73Snpiggin@suse.de /* 560d3ef3d73Snpiggin@suse.de * After storing MNT_WRITE_HOLD, we'll read the counters. This store 561d3ef3d73Snpiggin@suse.de * should be visible before we do. 562d3ef3d73Snpiggin@suse.de */ 563d3ef3d73Snpiggin@suse.de smp_mb(); 564d3ef3d73Snpiggin@suse.de 565d3ef3d73Snpiggin@suse.de /* 566d3ef3d73Snpiggin@suse.de * With writers on hold, if this value is zero, then there are 567d3ef3d73Snpiggin@suse.de * definitely no active writers (although held writers may subsequently 568d3ef3d73Snpiggin@suse.de * increment the count, they'll have to wait, and decrement it after 569d3ef3d73Snpiggin@suse.de * seeing MNT_READONLY). 570d3ef3d73Snpiggin@suse.de * 571d3ef3d73Snpiggin@suse.de * It is OK to have counter incremented on one CPU and decremented on 572d3ef3d73Snpiggin@suse.de * another: the sum will add up correctly. The danger would be when we 573d3ef3d73Snpiggin@suse.de * sum up each counter, if we read a counter before it is incremented, 574d3ef3d73Snpiggin@suse.de * but then read another CPU's count which it has been subsequently 575d3ef3d73Snpiggin@suse.de * decremented from -- we would see more decrements than we should. 576d3ef3d73Snpiggin@suse.de * MNT_WRITE_HOLD protects against this scenario, because 577d3ef3d73Snpiggin@suse.de * mnt_want_write first increments count, then smp_mb, then spins on 578d3ef3d73Snpiggin@suse.de * MNT_WRITE_HOLD, so it can't be decremented by another CPU while 579d3ef3d73Snpiggin@suse.de * we're counting up here. 580d3ef3d73Snpiggin@suse.de */ 581c6653a83SNick Piggin if (mnt_get_writers(mnt) > 0) 582d3ef3d73Snpiggin@suse.de ret = -EBUSY; 583d3ef3d73Snpiggin@suse.de else 58483adc753SAl Viro mnt->mnt.mnt_flags |= MNT_READONLY; 585d3ef3d73Snpiggin@suse.de /* 586d3ef3d73Snpiggin@suse.de * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers 587d3ef3d73Snpiggin@suse.de * that become unheld will see MNT_READONLY. 588d3ef3d73Snpiggin@suse.de */ 589d3ef3d73Snpiggin@suse.de smp_wmb(); 59083adc753SAl Viro mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; 591719ea2fbSAl Viro unlock_mount_hash(); 5923d733633SDave Hansen return ret; 5933d733633SDave Hansen } 5948366025eSDave Hansen 59583adc753SAl Viro static void __mnt_unmake_readonly(struct mount *mnt) 5962e4b7fcdSDave Hansen { 597719ea2fbSAl Viro lock_mount_hash(); 59883adc753SAl Viro mnt->mnt.mnt_flags &= ~MNT_READONLY; 599719ea2fbSAl Viro unlock_mount_hash(); 6002e4b7fcdSDave Hansen } 6012e4b7fcdSDave Hansen 6024ed5e82fSMiklos Szeredi int sb_prepare_remount_readonly(struct super_block *sb) 6034ed5e82fSMiklos Szeredi { 6044ed5e82fSMiklos Szeredi struct mount *mnt; 6054ed5e82fSMiklos Szeredi int err = 0; 6064ed5e82fSMiklos Szeredi 6078e8b8796SMiklos Szeredi /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */ 6088e8b8796SMiklos Szeredi if (atomic_long_read(&sb->s_remove_count)) 6098e8b8796SMiklos Szeredi return -EBUSY; 6108e8b8796SMiklos Szeredi 611719ea2fbSAl Viro lock_mount_hash(); 6124ed5e82fSMiklos Szeredi list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { 6134ed5e82fSMiklos Szeredi if (!(mnt->mnt.mnt_flags & MNT_READONLY)) { 6144ed5e82fSMiklos Szeredi mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; 6154ed5e82fSMiklos Szeredi smp_mb(); 6164ed5e82fSMiklos Szeredi if (mnt_get_writers(mnt) > 0) { 6174ed5e82fSMiklos Szeredi err = -EBUSY; 6184ed5e82fSMiklos Szeredi break; 6194ed5e82fSMiklos Szeredi } 6204ed5e82fSMiklos Szeredi } 6214ed5e82fSMiklos Szeredi } 6228e8b8796SMiklos Szeredi if (!err && atomic_long_read(&sb->s_remove_count)) 6238e8b8796SMiklos Szeredi err = -EBUSY; 6248e8b8796SMiklos Szeredi 6254ed5e82fSMiklos Szeredi if (!err) { 6264ed5e82fSMiklos Szeredi sb->s_readonly_remount = 1; 6274ed5e82fSMiklos Szeredi smp_wmb(); 6284ed5e82fSMiklos Szeredi } 6294ed5e82fSMiklos Szeredi list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { 6304ed5e82fSMiklos Szeredi if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD) 6314ed5e82fSMiklos Szeredi mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; 6324ed5e82fSMiklos Szeredi } 633719ea2fbSAl Viro unlock_mount_hash(); 6344ed5e82fSMiklos Szeredi 6354ed5e82fSMiklos Szeredi return err; 6364ed5e82fSMiklos Szeredi } 6374ed5e82fSMiklos Szeredi 638b105e270SAl Viro static void free_vfsmnt(struct mount *mnt) 6391da177e4SLinus Torvalds { 640fcc139aeSAndrzej Hajda kfree_const(mnt->mnt_devname); 641d3ef3d73Snpiggin@suse.de #ifdef CONFIG_SMP 64268e8a9feSAl Viro free_percpu(mnt->mnt_pcp); 643d3ef3d73Snpiggin@suse.de #endif 644b105e270SAl Viro kmem_cache_free(mnt_cache, mnt); 6451da177e4SLinus Torvalds } 6461da177e4SLinus Torvalds 6478ffcb32eSDavid Howells static void delayed_free_vfsmnt(struct rcu_head *head) 6488ffcb32eSDavid Howells { 6498ffcb32eSDavid Howells free_vfsmnt(container_of(head, struct mount, mnt_rcu)); 6508ffcb32eSDavid Howells } 6518ffcb32eSDavid Howells 65248a066e7SAl Viro /* call under rcu_read_lock */ 653294d71ffSAl Viro int __legitimize_mnt(struct vfsmount *bastard, unsigned seq) 65448a066e7SAl Viro { 65548a066e7SAl Viro struct mount *mnt; 65648a066e7SAl Viro if (read_seqretry(&mount_lock, seq)) 657294d71ffSAl Viro return 1; 65848a066e7SAl Viro if (bastard == NULL) 659294d71ffSAl Viro return 0; 66048a066e7SAl Viro mnt = real_mount(bastard); 66148a066e7SAl Viro mnt_add_count(mnt, 1); 66248a066e7SAl Viro if (likely(!read_seqretry(&mount_lock, seq))) 663294d71ffSAl Viro return 0; 66448a066e7SAl Viro if (bastard->mnt_flags & MNT_SYNC_UMOUNT) { 66548a066e7SAl Viro mnt_add_count(mnt, -1); 666294d71ffSAl Viro return 1; 66748a066e7SAl Viro } 668294d71ffSAl Viro return -1; 669294d71ffSAl Viro } 670294d71ffSAl Viro 671294d71ffSAl Viro /* call under rcu_read_lock */ 672294d71ffSAl Viro bool legitimize_mnt(struct vfsmount *bastard, unsigned seq) 673294d71ffSAl Viro { 674294d71ffSAl Viro int res = __legitimize_mnt(bastard, seq); 675294d71ffSAl Viro if (likely(!res)) 676294d71ffSAl Viro return true; 677294d71ffSAl Viro if (unlikely(res < 0)) { 67848a066e7SAl Viro rcu_read_unlock(); 67948a066e7SAl Viro mntput(bastard); 68048a066e7SAl Viro rcu_read_lock(); 681294d71ffSAl Viro } 68248a066e7SAl Viro return false; 68348a066e7SAl Viro } 68448a066e7SAl Viro 6851da177e4SLinus Torvalds /* 686474279dcSAl Viro * find the first mount at @dentry on vfsmount @mnt. 68748a066e7SAl Viro * call under rcu_read_lock() 6881da177e4SLinus Torvalds */ 689474279dcSAl Viro struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry) 6901da177e4SLinus Torvalds { 69138129a13SAl Viro struct hlist_head *head = m_hash(mnt, dentry); 692474279dcSAl Viro struct mount *p; 6931da177e4SLinus Torvalds 69438129a13SAl Viro hlist_for_each_entry_rcu(p, head, mnt_hash) 695474279dcSAl Viro if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) 696474279dcSAl Viro return p; 697474279dcSAl Viro return NULL; 6981da177e4SLinus Torvalds } 699474279dcSAl Viro 700474279dcSAl Viro /* 701f015f126SDavid Howells * lookup_mnt - Return the first child mount mounted at path 702f015f126SDavid Howells * 703f015f126SDavid Howells * "First" means first mounted chronologically. If you create the 704f015f126SDavid Howells * following mounts: 705f015f126SDavid Howells * 706f015f126SDavid Howells * mount /dev/sda1 /mnt 707f015f126SDavid Howells * mount /dev/sda2 /mnt 708f015f126SDavid Howells * mount /dev/sda3 /mnt 709f015f126SDavid Howells * 710f015f126SDavid Howells * Then lookup_mnt() on the base /mnt dentry in the root mount will 711f015f126SDavid Howells * return successively the root dentry and vfsmount of /dev/sda1, then 712f015f126SDavid Howells * /dev/sda2, then /dev/sda3, then NULL. 713f015f126SDavid Howells * 714f015f126SDavid Howells * lookup_mnt takes a reference to the found vfsmount. 715a05964f3SRam Pai */ 716ca71cf71SAl Viro struct vfsmount *lookup_mnt(const struct path *path) 717a05964f3SRam Pai { 718c7105365SAl Viro struct mount *child_mnt; 71948a066e7SAl Viro struct vfsmount *m; 72048a066e7SAl Viro unsigned seq; 72199b7db7bSNick Piggin 72248a066e7SAl Viro rcu_read_lock(); 72348a066e7SAl Viro do { 72448a066e7SAl Viro seq = read_seqbegin(&mount_lock); 725474279dcSAl Viro child_mnt = __lookup_mnt(path->mnt, path->dentry); 72648a066e7SAl Viro m = child_mnt ? &child_mnt->mnt : NULL; 72748a066e7SAl Viro } while (!legitimize_mnt(m, seq)); 72848a066e7SAl Viro rcu_read_unlock(); 72948a066e7SAl Viro return m; 730a05964f3SRam Pai } 731a05964f3SRam Pai 7327af1364fSEric W. Biederman /* 7337af1364fSEric W. Biederman * __is_local_mountpoint - Test to see if dentry is a mountpoint in the 7347af1364fSEric W. Biederman * current mount namespace. 7357af1364fSEric W. Biederman * 7367af1364fSEric W. Biederman * The common case is dentries are not mountpoints at all and that 7377af1364fSEric W. Biederman * test is handled inline. For the slow case when we are actually 7387af1364fSEric W. Biederman * dealing with a mountpoint of some kind, walk through all of the 7397af1364fSEric W. Biederman * mounts in the current mount namespace and test to see if the dentry 7407af1364fSEric W. Biederman * is a mountpoint. 7417af1364fSEric W. Biederman * 7427af1364fSEric W. Biederman * The mount_hashtable is not usable in the context because we 7437af1364fSEric W. Biederman * need to identify all mounts that may be in the current mount 7447af1364fSEric W. Biederman * namespace not just a mount that happens to have some specified 7457af1364fSEric W. Biederman * parent mount. 7467af1364fSEric W. Biederman */ 7477af1364fSEric W. Biederman bool __is_local_mountpoint(struct dentry *dentry) 7487af1364fSEric W. Biederman { 7497af1364fSEric W. Biederman struct mnt_namespace *ns = current->nsproxy->mnt_ns; 7507af1364fSEric W. Biederman struct mount *mnt; 7517af1364fSEric W. Biederman bool is_covered = false; 7527af1364fSEric W. Biederman 7537af1364fSEric W. Biederman if (!d_mountpoint(dentry)) 7547af1364fSEric W. Biederman goto out; 7557af1364fSEric W. Biederman 7567af1364fSEric W. Biederman down_read(&namespace_sem); 7577af1364fSEric W. Biederman list_for_each_entry(mnt, &ns->list, mnt_list) { 7587af1364fSEric W. Biederman is_covered = (mnt->mnt_mountpoint == dentry); 7597af1364fSEric W. Biederman if (is_covered) 7607af1364fSEric W. Biederman break; 7617af1364fSEric W. Biederman } 7627af1364fSEric W. Biederman up_read(&namespace_sem); 7637af1364fSEric W. Biederman out: 7647af1364fSEric W. Biederman return is_covered; 7657af1364fSEric W. Biederman } 7667af1364fSEric W. Biederman 767e2dfa935SEric W. Biederman static struct mountpoint *lookup_mountpoint(struct dentry *dentry) 76884d17192SAl Viro { 7690818bf27SAl Viro struct hlist_head *chain = mp_hash(dentry); 77084d17192SAl Viro struct mountpoint *mp; 77184d17192SAl Viro 7720818bf27SAl Viro hlist_for_each_entry(mp, chain, m_hash) { 77384d17192SAl Viro if (mp->m_dentry == dentry) { 77484d17192SAl Viro /* might be worth a WARN_ON() */ 77584d17192SAl Viro if (d_unlinked(dentry)) 77684d17192SAl Viro return ERR_PTR(-ENOENT); 77784d17192SAl Viro mp->m_count++; 77884d17192SAl Viro return mp; 77984d17192SAl Viro } 78084d17192SAl Viro } 781e2dfa935SEric W. Biederman return NULL; 782e2dfa935SEric W. Biederman } 783e2dfa935SEric W. Biederman 7843895dbf8SEric W. Biederman static struct mountpoint *get_mountpoint(struct dentry *dentry) 785e2dfa935SEric W. Biederman { 7863895dbf8SEric W. Biederman struct mountpoint *mp, *new = NULL; 787e2dfa935SEric W. Biederman int ret; 78884d17192SAl Viro 7893895dbf8SEric W. Biederman if (d_mountpoint(dentry)) { 7903895dbf8SEric W. Biederman mountpoint: 7913895dbf8SEric W. Biederman read_seqlock_excl(&mount_lock); 7923895dbf8SEric W. Biederman mp = lookup_mountpoint(dentry); 7933895dbf8SEric W. Biederman read_sequnlock_excl(&mount_lock); 7943895dbf8SEric W. Biederman if (mp) 7953895dbf8SEric W. Biederman goto done; 79684d17192SAl Viro } 797eed81007SMiklos Szeredi 7983895dbf8SEric W. Biederman if (!new) 7993895dbf8SEric W. Biederman new = kmalloc(sizeof(struct mountpoint), GFP_KERNEL); 8003895dbf8SEric W. Biederman if (!new) 8013895dbf8SEric W. Biederman return ERR_PTR(-ENOMEM); 8023895dbf8SEric W. Biederman 8033895dbf8SEric W. Biederman 8043895dbf8SEric W. Biederman /* Exactly one processes may set d_mounted */ 8053895dbf8SEric W. Biederman ret = d_set_mounted(dentry); 8063895dbf8SEric W. Biederman 8073895dbf8SEric W. Biederman /* Someone else set d_mounted? */ 8083895dbf8SEric W. Biederman if (ret == -EBUSY) 8093895dbf8SEric W. Biederman goto mountpoint; 8103895dbf8SEric W. Biederman 8113895dbf8SEric W. Biederman /* The dentry is not available as a mountpoint? */ 8123895dbf8SEric W. Biederman mp = ERR_PTR(ret); 8133895dbf8SEric W. Biederman if (ret) 8143895dbf8SEric W. Biederman goto done; 8153895dbf8SEric W. Biederman 8163895dbf8SEric W. Biederman /* Add the new mountpoint to the hash table */ 8173895dbf8SEric W. Biederman read_seqlock_excl(&mount_lock); 8183895dbf8SEric W. Biederman new->m_dentry = dentry; 8193895dbf8SEric W. Biederman new->m_count = 1; 8203895dbf8SEric W. Biederman hlist_add_head(&new->m_hash, mp_hash(dentry)); 8213895dbf8SEric W. Biederman INIT_HLIST_HEAD(&new->m_list); 8223895dbf8SEric W. Biederman read_sequnlock_excl(&mount_lock); 8233895dbf8SEric W. Biederman 8243895dbf8SEric W. Biederman mp = new; 8253895dbf8SEric W. Biederman new = NULL; 8263895dbf8SEric W. Biederman done: 8273895dbf8SEric W. Biederman kfree(new); 82884d17192SAl Viro return mp; 82984d17192SAl Viro } 83084d17192SAl Viro 83184d17192SAl Viro static void put_mountpoint(struct mountpoint *mp) 83284d17192SAl Viro { 83384d17192SAl Viro if (!--mp->m_count) { 83484d17192SAl Viro struct dentry *dentry = mp->m_dentry; 8350a5eb7c8SEric W. Biederman BUG_ON(!hlist_empty(&mp->m_list)); 83684d17192SAl Viro spin_lock(&dentry->d_lock); 83784d17192SAl Viro dentry->d_flags &= ~DCACHE_MOUNTED; 83884d17192SAl Viro spin_unlock(&dentry->d_lock); 8390818bf27SAl Viro hlist_del(&mp->m_hash); 84084d17192SAl Viro kfree(mp); 84184d17192SAl Viro } 84284d17192SAl Viro } 84384d17192SAl Viro 844143c8c91SAl Viro static inline int check_mnt(struct mount *mnt) 8451da177e4SLinus Torvalds { 8466b3286edSKirill Korotaev return mnt->mnt_ns == current->nsproxy->mnt_ns; 8471da177e4SLinus Torvalds } 8481da177e4SLinus Torvalds 84999b7db7bSNick Piggin /* 85099b7db7bSNick Piggin * vfsmount lock must be held for write 85199b7db7bSNick Piggin */ 8526b3286edSKirill Korotaev static void touch_mnt_namespace(struct mnt_namespace *ns) 8535addc5ddSAl Viro { 8545addc5ddSAl Viro if (ns) { 8555addc5ddSAl Viro ns->event = ++event; 8565addc5ddSAl Viro wake_up_interruptible(&ns->poll); 8575addc5ddSAl Viro } 8585addc5ddSAl Viro } 8595addc5ddSAl Viro 86099b7db7bSNick Piggin /* 86199b7db7bSNick Piggin * vfsmount lock must be held for write 86299b7db7bSNick Piggin */ 8636b3286edSKirill Korotaev static void __touch_mnt_namespace(struct mnt_namespace *ns) 8645addc5ddSAl Viro { 8655addc5ddSAl Viro if (ns && ns->event != event) { 8665addc5ddSAl Viro ns->event = event; 8675addc5ddSAl Viro wake_up_interruptible(&ns->poll); 8685addc5ddSAl Viro } 8695addc5ddSAl Viro } 8705addc5ddSAl Viro 87199b7db7bSNick Piggin /* 87299b7db7bSNick Piggin * vfsmount lock must be held for write 87399b7db7bSNick Piggin */ 8747bdb11deSEric W. Biederman static void unhash_mnt(struct mount *mnt) 8751da177e4SLinus Torvalds { 8760714a533SAl Viro mnt->mnt_parent = mnt; 877a73324daSAl Viro mnt->mnt_mountpoint = mnt->mnt.mnt_root; 8786b41d536SAl Viro list_del_init(&mnt->mnt_child); 87938129a13SAl Viro hlist_del_init_rcu(&mnt->mnt_hash); 8800a5eb7c8SEric W. Biederman hlist_del_init(&mnt->mnt_mp_list); 88184d17192SAl Viro put_mountpoint(mnt->mnt_mp); 88284d17192SAl Viro mnt->mnt_mp = NULL; 8831da177e4SLinus Torvalds } 8841da177e4SLinus Torvalds 88599b7db7bSNick Piggin /* 88699b7db7bSNick Piggin * vfsmount lock must be held for write 88799b7db7bSNick Piggin */ 8887bdb11deSEric W. Biederman static void detach_mnt(struct mount *mnt, struct path *old_path) 8897bdb11deSEric W. Biederman { 8907bdb11deSEric W. Biederman old_path->dentry = mnt->mnt_mountpoint; 8917bdb11deSEric W. Biederman old_path->mnt = &mnt->mnt_parent->mnt; 8927bdb11deSEric W. Biederman unhash_mnt(mnt); 8937bdb11deSEric W. Biederman } 8947bdb11deSEric W. Biederman 8957bdb11deSEric W. Biederman /* 8967bdb11deSEric W. Biederman * vfsmount lock must be held for write 8977bdb11deSEric W. Biederman */ 8986a46c573SEric W. Biederman static void umount_mnt(struct mount *mnt) 8996a46c573SEric W. Biederman { 9006a46c573SEric W. Biederman /* old mountpoint will be dropped when we can do that */ 9016a46c573SEric W. Biederman mnt->mnt_ex_mountpoint = mnt->mnt_mountpoint; 9026a46c573SEric W. Biederman unhash_mnt(mnt); 9036a46c573SEric W. Biederman } 9046a46c573SEric W. Biederman 9056a46c573SEric W. Biederman /* 9066a46c573SEric W. Biederman * vfsmount lock must be held for write 9076a46c573SEric W. Biederman */ 90884d17192SAl Viro void mnt_set_mountpoint(struct mount *mnt, 90984d17192SAl Viro struct mountpoint *mp, 91044d964d6SAl Viro struct mount *child_mnt) 911b90fa9aeSRam Pai { 91284d17192SAl Viro mp->m_count++; 9133a2393d7SAl Viro mnt_add_count(mnt, 1); /* essentially, that's mntget */ 91484d17192SAl Viro child_mnt->mnt_mountpoint = dget(mp->m_dentry); 9153a2393d7SAl Viro child_mnt->mnt_parent = mnt; 91684d17192SAl Viro child_mnt->mnt_mp = mp; 9170a5eb7c8SEric W. Biederman hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list); 918b90fa9aeSRam Pai } 919b90fa9aeSRam Pai 9201064f874SEric W. Biederman static void __attach_mnt(struct mount *mnt, struct mount *parent) 9211064f874SEric W. Biederman { 9221064f874SEric W. Biederman hlist_add_head_rcu(&mnt->mnt_hash, 9231064f874SEric W. Biederman m_hash(&parent->mnt, mnt->mnt_mountpoint)); 9241064f874SEric W. Biederman list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); 9251064f874SEric W. Biederman } 9261064f874SEric W. Biederman 92799b7db7bSNick Piggin /* 92899b7db7bSNick Piggin * vfsmount lock must be held for write 92999b7db7bSNick Piggin */ 93084d17192SAl Viro static void attach_mnt(struct mount *mnt, 93184d17192SAl Viro struct mount *parent, 93284d17192SAl Viro struct mountpoint *mp) 9331da177e4SLinus Torvalds { 93484d17192SAl Viro mnt_set_mountpoint(parent, mp, mnt); 9351064f874SEric W. Biederman __attach_mnt(mnt, parent); 936b90fa9aeSRam Pai } 937b90fa9aeSRam Pai 9381064f874SEric W. Biederman void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp, struct mount *mnt) 93912a5b529SAl Viro { 9401064f874SEric W. Biederman struct mountpoint *old_mp = mnt->mnt_mp; 9411064f874SEric W. Biederman struct dentry *old_mountpoint = mnt->mnt_mountpoint; 9421064f874SEric W. Biederman struct mount *old_parent = mnt->mnt_parent; 9431064f874SEric W. Biederman 9441064f874SEric W. Biederman list_del_init(&mnt->mnt_child); 9451064f874SEric W. Biederman hlist_del_init(&mnt->mnt_mp_list); 9461064f874SEric W. Biederman hlist_del_init_rcu(&mnt->mnt_hash); 9471064f874SEric W. Biederman 9481064f874SEric W. Biederman attach_mnt(mnt, parent, mp); 9491064f874SEric W. Biederman 9501064f874SEric W. Biederman put_mountpoint(old_mp); 9511064f874SEric W. Biederman 9521064f874SEric W. Biederman /* 9531064f874SEric W. Biederman * Safely avoid even the suggestion this code might sleep or 9541064f874SEric W. Biederman * lock the mount hash by taking advantage of the knowledge that 9551064f874SEric W. Biederman * mnt_change_mountpoint will not release the final reference 9561064f874SEric W. Biederman * to a mountpoint. 9571064f874SEric W. Biederman * 9581064f874SEric W. Biederman * During mounting, the mount passed in as the parent mount will 9591064f874SEric W. Biederman * continue to use the old mountpoint and during unmounting, the 9601064f874SEric W. Biederman * old mountpoint will continue to exist until namespace_unlock, 9611064f874SEric W. Biederman * which happens well after mnt_change_mountpoint. 9621064f874SEric W. Biederman */ 9631064f874SEric W. Biederman spin_lock(&old_mountpoint->d_lock); 9641064f874SEric W. Biederman old_mountpoint->d_lockref.count--; 9651064f874SEric W. Biederman spin_unlock(&old_mountpoint->d_lock); 9661064f874SEric W. Biederman 9671064f874SEric W. Biederman mnt_add_count(old_parent, -1); 96812a5b529SAl Viro } 96912a5b529SAl Viro 970b90fa9aeSRam Pai /* 97199b7db7bSNick Piggin * vfsmount lock must be held for write 972b90fa9aeSRam Pai */ 9731064f874SEric W. Biederman static void commit_tree(struct mount *mnt) 974b90fa9aeSRam Pai { 9750714a533SAl Viro struct mount *parent = mnt->mnt_parent; 97683adc753SAl Viro struct mount *m; 977b90fa9aeSRam Pai LIST_HEAD(head); 978143c8c91SAl Viro struct mnt_namespace *n = parent->mnt_ns; 979b90fa9aeSRam Pai 9800714a533SAl Viro BUG_ON(parent == mnt); 981b90fa9aeSRam Pai 9821a4eeaf2SAl Viro list_add_tail(&head, &mnt->mnt_list); 983f7a99c5bSAl Viro list_for_each_entry(m, &head, mnt_list) 984143c8c91SAl Viro m->mnt_ns = n; 985f03c6599SAl Viro 986b90fa9aeSRam Pai list_splice(&head, n->list.prev); 987b90fa9aeSRam Pai 988d2921684SEric W. Biederman n->mounts += n->pending_mounts; 989d2921684SEric W. Biederman n->pending_mounts = 0; 990d2921684SEric W. Biederman 9911064f874SEric W. Biederman __attach_mnt(mnt, parent); 9926b3286edSKirill Korotaev touch_mnt_namespace(n); 9931da177e4SLinus Torvalds } 9941da177e4SLinus Torvalds 995909b0a88SAl Viro static struct mount *next_mnt(struct mount *p, struct mount *root) 9961da177e4SLinus Torvalds { 9976b41d536SAl Viro struct list_head *next = p->mnt_mounts.next; 9986b41d536SAl Viro if (next == &p->mnt_mounts) { 9991da177e4SLinus Torvalds while (1) { 1000909b0a88SAl Viro if (p == root) 10011da177e4SLinus Torvalds return NULL; 10026b41d536SAl Viro next = p->mnt_child.next; 10036b41d536SAl Viro if (next != &p->mnt_parent->mnt_mounts) 10041da177e4SLinus Torvalds break; 10050714a533SAl Viro p = p->mnt_parent; 10061da177e4SLinus Torvalds } 10071da177e4SLinus Torvalds } 10086b41d536SAl Viro return list_entry(next, struct mount, mnt_child); 10091da177e4SLinus Torvalds } 10101da177e4SLinus Torvalds 1011315fc83eSAl Viro static struct mount *skip_mnt_tree(struct mount *p) 10129676f0c6SRam Pai { 10136b41d536SAl Viro struct list_head *prev = p->mnt_mounts.prev; 10146b41d536SAl Viro while (prev != &p->mnt_mounts) { 10156b41d536SAl Viro p = list_entry(prev, struct mount, mnt_child); 10166b41d536SAl Viro prev = p->mnt_mounts.prev; 10179676f0c6SRam Pai } 10189676f0c6SRam Pai return p; 10199676f0c6SRam Pai } 10209676f0c6SRam Pai 10219d412a43SAl Viro struct vfsmount * 10229d412a43SAl Viro vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data) 10239d412a43SAl Viro { 1024b105e270SAl Viro struct mount *mnt; 10259d412a43SAl Viro struct dentry *root; 10269d412a43SAl Viro 10279d412a43SAl Viro if (!type) 10289d412a43SAl Viro return ERR_PTR(-ENODEV); 10299d412a43SAl Viro 10309d412a43SAl Viro mnt = alloc_vfsmnt(name); 10319d412a43SAl Viro if (!mnt) 10329d412a43SAl Viro return ERR_PTR(-ENOMEM); 10339d412a43SAl Viro 1034e462ec50SDavid Howells if (flags & SB_KERNMOUNT) 1035b105e270SAl Viro mnt->mnt.mnt_flags = MNT_INTERNAL; 10369d412a43SAl Viro 10379d412a43SAl Viro root = mount_fs(type, flags, name, data); 10389d412a43SAl Viro if (IS_ERR(root)) { 10398ffcb32eSDavid Howells mnt_free_id(mnt); 10409d412a43SAl Viro free_vfsmnt(mnt); 10419d412a43SAl Viro return ERR_CAST(root); 10429d412a43SAl Viro } 10439d412a43SAl Viro 1044b105e270SAl Viro mnt->mnt.mnt_root = root; 1045b105e270SAl Viro mnt->mnt.mnt_sb = root->d_sb; 1046a73324daSAl Viro mnt->mnt_mountpoint = mnt->mnt.mnt_root; 10470714a533SAl Viro mnt->mnt_parent = mnt; 1048719ea2fbSAl Viro lock_mount_hash(); 104939f7c4dbSMiklos Szeredi list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts); 1050719ea2fbSAl Viro unlock_mount_hash(); 1051b105e270SAl Viro return &mnt->mnt; 10529d412a43SAl Viro } 10539d412a43SAl Viro EXPORT_SYMBOL_GPL(vfs_kern_mount); 10549d412a43SAl Viro 105593faccbbSEric W. Biederman struct vfsmount * 105693faccbbSEric W. Biederman vfs_submount(const struct dentry *mountpoint, struct file_system_type *type, 105793faccbbSEric W. Biederman const char *name, void *data) 105893faccbbSEric W. Biederman { 105993faccbbSEric W. Biederman /* Until it is worked out how to pass the user namespace 106093faccbbSEric W. Biederman * through from the parent mount to the submount don't support 106193faccbbSEric W. Biederman * unprivileged mounts with submounts. 106293faccbbSEric W. Biederman */ 106393faccbbSEric W. Biederman if (mountpoint->d_sb->s_user_ns != &init_user_ns) 106493faccbbSEric W. Biederman return ERR_PTR(-EPERM); 106593faccbbSEric W. Biederman 1066e462ec50SDavid Howells return vfs_kern_mount(type, SB_SUBMOUNT, name, data); 106793faccbbSEric W. Biederman } 106893faccbbSEric W. Biederman EXPORT_SYMBOL_GPL(vfs_submount); 106993faccbbSEric W. Biederman 107087129cc0SAl Viro static struct mount *clone_mnt(struct mount *old, struct dentry *root, 107136341f64SRam Pai int flag) 10721da177e4SLinus Torvalds { 107387129cc0SAl Viro struct super_block *sb = old->mnt.mnt_sb; 1074be34d1a3SDavid Howells struct mount *mnt; 1075be34d1a3SDavid Howells int err; 10761da177e4SLinus Torvalds 1077be34d1a3SDavid Howells mnt = alloc_vfsmnt(old->mnt_devname); 1078be34d1a3SDavid Howells if (!mnt) 1079be34d1a3SDavid Howells return ERR_PTR(-ENOMEM); 1080be34d1a3SDavid Howells 10817a472ef4SEric W. Biederman if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE)) 108215169fe7SAl Viro mnt->mnt_group_id = 0; /* not a peer of original */ 1083719f5d7fSMiklos Szeredi else 108415169fe7SAl Viro mnt->mnt_group_id = old->mnt_group_id; 1085719f5d7fSMiklos Szeredi 108615169fe7SAl Viro if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { 1087be34d1a3SDavid Howells err = mnt_alloc_group_id(mnt); 1088719f5d7fSMiklos Szeredi if (err) 1089719f5d7fSMiklos Szeredi goto out_free; 1090719f5d7fSMiklos Szeredi } 1091719f5d7fSMiklos Szeredi 109216a34adbSAl Viro mnt->mnt.mnt_flags = old->mnt.mnt_flags; 109316a34adbSAl Viro mnt->mnt.mnt_flags &= ~(MNT_WRITE_HOLD|MNT_MARKED|MNT_INTERNAL); 1094132c94e3SEric W. Biederman /* Don't allow unprivileged users to change mount flags */ 10959566d674SEric W. Biederman if (flag & CL_UNPRIVILEGED) { 10969566d674SEric W. Biederman mnt->mnt.mnt_flags |= MNT_LOCK_ATIME; 10979566d674SEric W. Biederman 10989566d674SEric W. Biederman if (mnt->mnt.mnt_flags & MNT_READONLY) 1099132c94e3SEric W. Biederman mnt->mnt.mnt_flags |= MNT_LOCK_READONLY; 1100132c94e3SEric W. Biederman 11019566d674SEric W. Biederman if (mnt->mnt.mnt_flags & MNT_NODEV) 11029566d674SEric W. Biederman mnt->mnt.mnt_flags |= MNT_LOCK_NODEV; 11039566d674SEric W. Biederman 11049566d674SEric W. Biederman if (mnt->mnt.mnt_flags & MNT_NOSUID) 11059566d674SEric W. Biederman mnt->mnt.mnt_flags |= MNT_LOCK_NOSUID; 11069566d674SEric W. Biederman 11079566d674SEric W. Biederman if (mnt->mnt.mnt_flags & MNT_NOEXEC) 11089566d674SEric W. Biederman mnt->mnt.mnt_flags |= MNT_LOCK_NOEXEC; 11099566d674SEric W. Biederman } 11109566d674SEric W. Biederman 11115ff9d8a6SEric W. Biederman /* Don't allow unprivileged users to reveal what is under a mount */ 1112381cacb1SEric W. Biederman if ((flag & CL_UNPRIVILEGED) && 1113381cacb1SEric W. Biederman (!(flag & CL_EXPIRE) || list_empty(&old->mnt_expire))) 11145ff9d8a6SEric W. Biederman mnt->mnt.mnt_flags |= MNT_LOCKED; 11155ff9d8a6SEric W. Biederman 11161da177e4SLinus Torvalds atomic_inc(&sb->s_active); 1117b105e270SAl Viro mnt->mnt.mnt_sb = sb; 1118b105e270SAl Viro mnt->mnt.mnt_root = dget(root); 1119a73324daSAl Viro mnt->mnt_mountpoint = mnt->mnt.mnt_root; 11200714a533SAl Viro mnt->mnt_parent = mnt; 1121719ea2fbSAl Viro lock_mount_hash(); 112239f7c4dbSMiklos Szeredi list_add_tail(&mnt->mnt_instance, &sb->s_mounts); 1123719ea2fbSAl Viro unlock_mount_hash(); 1124b90fa9aeSRam Pai 11257a472ef4SEric W. Biederman if ((flag & CL_SLAVE) || 11267a472ef4SEric W. Biederman ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) { 11276776db3dSAl Viro list_add(&mnt->mnt_slave, &old->mnt_slave_list); 112832301920SAl Viro mnt->mnt_master = old; 1129fc7be130SAl Viro CLEAR_MNT_SHARED(mnt); 11308aec0809SAl Viro } else if (!(flag & CL_PRIVATE)) { 1131fc7be130SAl Viro if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old)) 11326776db3dSAl Viro list_add(&mnt->mnt_share, &old->mnt_share); 1133d10e8defSAl Viro if (IS_MNT_SLAVE(old)) 11346776db3dSAl Viro list_add(&mnt->mnt_slave, &old->mnt_slave); 1135d10e8defSAl Viro mnt->mnt_master = old->mnt_master; 11365235d448SAl Viro } else { 11375235d448SAl Viro CLEAR_MNT_SHARED(mnt); 11385afe0022SRam Pai } 1139b90fa9aeSRam Pai if (flag & CL_MAKE_SHARED) 11400f0afb1dSAl Viro set_mnt_shared(mnt); 11411da177e4SLinus Torvalds 11421da177e4SLinus Torvalds /* stick the duplicate mount on the same expiry list 11431da177e4SLinus Torvalds * as the original if that was on one */ 114436341f64SRam Pai if (flag & CL_EXPIRE) { 11456776db3dSAl Viro if (!list_empty(&old->mnt_expire)) 11466776db3dSAl Viro list_add(&mnt->mnt_expire, &old->mnt_expire); 11471da177e4SLinus Torvalds } 1148be34d1a3SDavid Howells 1149cb338d06SAl Viro return mnt; 1150719f5d7fSMiklos Szeredi 1151719f5d7fSMiklos Szeredi out_free: 11528ffcb32eSDavid Howells mnt_free_id(mnt); 1153719f5d7fSMiklos Szeredi free_vfsmnt(mnt); 1154be34d1a3SDavid Howells return ERR_PTR(err); 11551da177e4SLinus Torvalds } 11561da177e4SLinus Torvalds 11579ea459e1SAl Viro static void cleanup_mnt(struct mount *mnt) 11589ea459e1SAl Viro { 11599ea459e1SAl Viro /* 11609ea459e1SAl Viro * This probably indicates that somebody messed 11619ea459e1SAl Viro * up a mnt_want/drop_write() pair. If this 11629ea459e1SAl Viro * happens, the filesystem was probably unable 11639ea459e1SAl Viro * to make r/w->r/o transitions. 11649ea459e1SAl Viro */ 11659ea459e1SAl Viro /* 11669ea459e1SAl Viro * The locking used to deal with mnt_count decrement provides barriers, 11679ea459e1SAl Viro * so mnt_get_writers() below is safe. 11689ea459e1SAl Viro */ 11699ea459e1SAl Viro WARN_ON(mnt_get_writers(mnt)); 11709ea459e1SAl Viro if (unlikely(mnt->mnt_pins.first)) 11719ea459e1SAl Viro mnt_pin_kill(mnt); 11729ea459e1SAl Viro fsnotify_vfsmount_delete(&mnt->mnt); 11739ea459e1SAl Viro dput(mnt->mnt.mnt_root); 11749ea459e1SAl Viro deactivate_super(mnt->mnt.mnt_sb); 11759ea459e1SAl Viro mnt_free_id(mnt); 11769ea459e1SAl Viro call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt); 11779ea459e1SAl Viro } 11789ea459e1SAl Viro 11799ea459e1SAl Viro static void __cleanup_mnt(struct rcu_head *head) 11809ea459e1SAl Viro { 11819ea459e1SAl Viro cleanup_mnt(container_of(head, struct mount, mnt_rcu)); 11829ea459e1SAl Viro } 11839ea459e1SAl Viro 11849ea459e1SAl Viro static LLIST_HEAD(delayed_mntput_list); 11859ea459e1SAl Viro static void delayed_mntput(struct work_struct *unused) 11869ea459e1SAl Viro { 11879ea459e1SAl Viro struct llist_node *node = llist_del_all(&delayed_mntput_list); 118829785735SByungchul Park struct mount *m, *t; 11899ea459e1SAl Viro 119029785735SByungchul Park llist_for_each_entry_safe(m, t, node, mnt_llist) 119129785735SByungchul Park cleanup_mnt(m); 11929ea459e1SAl Viro } 11939ea459e1SAl Viro static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput); 11949ea459e1SAl Viro 1195900148dcSAl Viro static void mntput_no_expire(struct mount *mnt) 11967b7b1aceSAl Viro { 119748a066e7SAl Viro rcu_read_lock(); 1198aa9c0e07SAl Viro mnt_add_count(mnt, -1); 119948a066e7SAl Viro if (likely(mnt->mnt_ns)) { /* shouldn't be the last one */ 120048a066e7SAl Viro rcu_read_unlock(); 120199b7db7bSNick Piggin return; 1202b3e19d92SNick Piggin } 1203719ea2fbSAl Viro lock_mount_hash(); 1204b3e19d92SNick Piggin if (mnt_get_count(mnt)) { 120548a066e7SAl Viro rcu_read_unlock(); 1206719ea2fbSAl Viro unlock_mount_hash(); 120799b7db7bSNick Piggin return; 120899b7db7bSNick Piggin } 120948a066e7SAl Viro if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) { 121048a066e7SAl Viro rcu_read_unlock(); 121148a066e7SAl Viro unlock_mount_hash(); 121248a066e7SAl Viro return; 121348a066e7SAl Viro } 121448a066e7SAl Viro mnt->mnt.mnt_flags |= MNT_DOOMED; 121548a066e7SAl Viro rcu_read_unlock(); 1216962830dfSAndi Kleen 121739f7c4dbSMiklos Szeredi list_del(&mnt->mnt_instance); 1218ce07d891SEric W. Biederman 1219ce07d891SEric W. Biederman if (unlikely(!list_empty(&mnt->mnt_mounts))) { 1220ce07d891SEric W. Biederman struct mount *p, *tmp; 1221ce07d891SEric W. Biederman list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) { 1222ce07d891SEric W. Biederman umount_mnt(p); 1223ce07d891SEric W. Biederman } 1224ce07d891SEric W. Biederman } 1225719ea2fbSAl Viro unlock_mount_hash(); 1226649a795aSAl Viro 12279ea459e1SAl Viro if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) { 12289ea459e1SAl Viro struct task_struct *task = current; 12299ea459e1SAl Viro if (likely(!(task->flags & PF_KTHREAD))) { 12309ea459e1SAl Viro init_task_work(&mnt->mnt_rcu, __cleanup_mnt); 12319ea459e1SAl Viro if (!task_work_add(task, &mnt->mnt_rcu, true)) 12329ea459e1SAl Viro return; 12339ea459e1SAl Viro } 12349ea459e1SAl Viro if (llist_add(&mnt->mnt_llist, &delayed_mntput_list)) 12359ea459e1SAl Viro schedule_delayed_work(&delayed_mntput_work, 1); 12369ea459e1SAl Viro return; 12379ea459e1SAl Viro } 12389ea459e1SAl Viro cleanup_mnt(mnt); 1239b3e19d92SNick Piggin } 1240b3e19d92SNick Piggin 1241b3e19d92SNick Piggin void mntput(struct vfsmount *mnt) 1242b3e19d92SNick Piggin { 1243b3e19d92SNick Piggin if (mnt) { 1244863d684fSAl Viro struct mount *m = real_mount(mnt); 1245b3e19d92SNick Piggin /* avoid cacheline pingpong, hope gcc doesn't get "smart" */ 1246863d684fSAl Viro if (unlikely(m->mnt_expiry_mark)) 1247863d684fSAl Viro m->mnt_expiry_mark = 0; 1248863d684fSAl Viro mntput_no_expire(m); 1249b3e19d92SNick Piggin } 1250b3e19d92SNick Piggin } 1251b3e19d92SNick Piggin EXPORT_SYMBOL(mntput); 1252b3e19d92SNick Piggin 1253b3e19d92SNick Piggin struct vfsmount *mntget(struct vfsmount *mnt) 1254b3e19d92SNick Piggin { 1255b3e19d92SNick Piggin if (mnt) 125683adc753SAl Viro mnt_add_count(real_mount(mnt), 1); 1257b3e19d92SNick Piggin return mnt; 1258b3e19d92SNick Piggin } 1259b3e19d92SNick Piggin EXPORT_SYMBOL(mntget); 1260b3e19d92SNick Piggin 1261c6609c0aSIan Kent /* path_is_mountpoint() - Check if path is a mount in the current 1262c6609c0aSIan Kent * namespace. 1263c6609c0aSIan Kent * 1264c6609c0aSIan Kent * d_mountpoint() can only be used reliably to establish if a dentry is 1265c6609c0aSIan Kent * not mounted in any namespace and that common case is handled inline. 1266c6609c0aSIan Kent * d_mountpoint() isn't aware of the possibility there may be multiple 1267c6609c0aSIan Kent * mounts using a given dentry in a different namespace. This function 1268c6609c0aSIan Kent * checks if the passed in path is a mountpoint rather than the dentry 1269c6609c0aSIan Kent * alone. 1270c6609c0aSIan Kent */ 1271c6609c0aSIan Kent bool path_is_mountpoint(const struct path *path) 1272c6609c0aSIan Kent { 1273c6609c0aSIan Kent unsigned seq; 1274c6609c0aSIan Kent bool res; 1275c6609c0aSIan Kent 1276c6609c0aSIan Kent if (!d_mountpoint(path->dentry)) 1277c6609c0aSIan Kent return false; 1278c6609c0aSIan Kent 1279c6609c0aSIan Kent rcu_read_lock(); 1280c6609c0aSIan Kent do { 1281c6609c0aSIan Kent seq = read_seqbegin(&mount_lock); 1282c6609c0aSIan Kent res = __path_is_mountpoint(path); 1283c6609c0aSIan Kent } while (read_seqretry(&mount_lock, seq)); 1284c6609c0aSIan Kent rcu_read_unlock(); 1285c6609c0aSIan Kent 1286c6609c0aSIan Kent return res; 1287c6609c0aSIan Kent } 1288c6609c0aSIan Kent EXPORT_SYMBOL(path_is_mountpoint); 1289c6609c0aSIan Kent 1290ca71cf71SAl Viro struct vfsmount *mnt_clone_internal(const struct path *path) 12917b7b1aceSAl Viro { 12923064c356SAl Viro struct mount *p; 12933064c356SAl Viro p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE); 12943064c356SAl Viro if (IS_ERR(p)) 12953064c356SAl Viro return ERR_CAST(p); 12963064c356SAl Viro p->mnt.mnt_flags |= MNT_INTERNAL; 12973064c356SAl Viro return &p->mnt; 12987b7b1aceSAl Viro } 12991da177e4SLinus Torvalds 1300a1a2c409SMiklos Szeredi #ifdef CONFIG_PROC_FS 13010226f492SAl Viro /* iterator; we want it to have access to namespace_sem, thus here... */ 13021da177e4SLinus Torvalds static void *m_start(struct seq_file *m, loff_t *pos) 13031da177e4SLinus Torvalds { 1304ede1bf0dSYann Droneaud struct proc_mounts *p = m->private; 13051da177e4SLinus Torvalds 1306390c6843SRam Pai down_read(&namespace_sem); 1307c7999c36SAl Viro if (p->cached_event == p->ns->event) { 1308c7999c36SAl Viro void *v = p->cached_mount; 1309c7999c36SAl Viro if (*pos == p->cached_index) 1310c7999c36SAl Viro return v; 1311c7999c36SAl Viro if (*pos == p->cached_index + 1) { 1312c7999c36SAl Viro v = seq_list_next(v, &p->ns->list, &p->cached_index); 1313c7999c36SAl Viro return p->cached_mount = v; 1314c7999c36SAl Viro } 1315c7999c36SAl Viro } 1316c7999c36SAl Viro 1317c7999c36SAl Viro p->cached_event = p->ns->event; 1318c7999c36SAl Viro p->cached_mount = seq_list_start(&p->ns->list, *pos); 1319c7999c36SAl Viro p->cached_index = *pos; 1320c7999c36SAl Viro return p->cached_mount; 13211da177e4SLinus Torvalds } 13221da177e4SLinus Torvalds 13231da177e4SLinus Torvalds static void *m_next(struct seq_file *m, void *v, loff_t *pos) 13241da177e4SLinus Torvalds { 1325ede1bf0dSYann Droneaud struct proc_mounts *p = m->private; 1326b0765fb8SPavel Emelianov 1327c7999c36SAl Viro p->cached_mount = seq_list_next(v, &p->ns->list, pos); 1328c7999c36SAl Viro p->cached_index = *pos; 1329c7999c36SAl Viro return p->cached_mount; 13301da177e4SLinus Torvalds } 13311da177e4SLinus Torvalds 13321da177e4SLinus Torvalds static void m_stop(struct seq_file *m, void *v) 13331da177e4SLinus Torvalds { 1334390c6843SRam Pai up_read(&namespace_sem); 13351da177e4SLinus Torvalds } 13361da177e4SLinus Torvalds 13370226f492SAl Viro static int m_show(struct seq_file *m, void *v) 13389f5596afSAl Viro { 1339ede1bf0dSYann Droneaud struct proc_mounts *p = m->private; 13401a4eeaf2SAl Viro struct mount *r = list_entry(v, struct mount, mnt_list); 13410226f492SAl Viro return p->show(m, &r->mnt); 13421da177e4SLinus Torvalds } 13431da177e4SLinus Torvalds 1344a1a2c409SMiklos Szeredi const struct seq_operations mounts_op = { 13451da177e4SLinus Torvalds .start = m_start, 13461da177e4SLinus Torvalds .next = m_next, 13471da177e4SLinus Torvalds .stop = m_stop, 13480226f492SAl Viro .show = m_show, 1349b4629fe2SChuck Lever }; 1350a1a2c409SMiklos Szeredi #endif /* CONFIG_PROC_FS */ 1351b4629fe2SChuck Lever 13521da177e4SLinus Torvalds /** 13531da177e4SLinus Torvalds * may_umount_tree - check if a mount tree is busy 13541da177e4SLinus Torvalds * @mnt: root of mount tree 13551da177e4SLinus Torvalds * 13561da177e4SLinus Torvalds * This is called to check if a tree of mounts has any 13571da177e4SLinus Torvalds * open files, pwds, chroots or sub mounts that are 13581da177e4SLinus Torvalds * busy. 13591da177e4SLinus Torvalds */ 1360909b0a88SAl Viro int may_umount_tree(struct vfsmount *m) 13611da177e4SLinus Torvalds { 1362909b0a88SAl Viro struct mount *mnt = real_mount(m); 136336341f64SRam Pai int actual_refs = 0; 136436341f64SRam Pai int minimum_refs = 0; 1365315fc83eSAl Viro struct mount *p; 1366909b0a88SAl Viro BUG_ON(!m); 13671da177e4SLinus Torvalds 1368b3e19d92SNick Piggin /* write lock needed for mnt_get_count */ 1369719ea2fbSAl Viro lock_mount_hash(); 1370909b0a88SAl Viro for (p = mnt; p; p = next_mnt(p, mnt)) { 137183adc753SAl Viro actual_refs += mnt_get_count(p); 13721da177e4SLinus Torvalds minimum_refs += 2; 13731da177e4SLinus Torvalds } 1374719ea2fbSAl Viro unlock_mount_hash(); 13751da177e4SLinus Torvalds 13761da177e4SLinus Torvalds if (actual_refs > minimum_refs) 13771da177e4SLinus Torvalds return 0; 1378e3474a8eSIan Kent 1379e3474a8eSIan Kent return 1; 13801da177e4SLinus Torvalds } 13811da177e4SLinus Torvalds 13821da177e4SLinus Torvalds EXPORT_SYMBOL(may_umount_tree); 13831da177e4SLinus Torvalds 13841da177e4SLinus Torvalds /** 13851da177e4SLinus Torvalds * may_umount - check if a mount point is busy 13861da177e4SLinus Torvalds * @mnt: root of mount 13871da177e4SLinus Torvalds * 13881da177e4SLinus Torvalds * This is called to check if a mount point has any 13891da177e4SLinus Torvalds * open files, pwds, chroots or sub mounts. If the 13901da177e4SLinus Torvalds * mount has sub mounts this will return busy 13911da177e4SLinus Torvalds * regardless of whether the sub mounts are busy. 13921da177e4SLinus Torvalds * 13931da177e4SLinus Torvalds * Doesn't take quota and stuff into account. IOW, in some cases it will 13941da177e4SLinus Torvalds * give false negatives. The main reason why it's here is that we need 13951da177e4SLinus Torvalds * a non-destructive way to look for easily umountable filesystems. 13961da177e4SLinus Torvalds */ 13971da177e4SLinus Torvalds int may_umount(struct vfsmount *mnt) 13981da177e4SLinus Torvalds { 1399e3474a8eSIan Kent int ret = 1; 14008ad08d8aSAl Viro down_read(&namespace_sem); 1401719ea2fbSAl Viro lock_mount_hash(); 14021ab59738SAl Viro if (propagate_mount_busy(real_mount(mnt), 2)) 1403e3474a8eSIan Kent ret = 0; 1404719ea2fbSAl Viro unlock_mount_hash(); 14058ad08d8aSAl Viro up_read(&namespace_sem); 1406a05964f3SRam Pai return ret; 14071da177e4SLinus Torvalds } 14081da177e4SLinus Torvalds 14091da177e4SLinus Torvalds EXPORT_SYMBOL(may_umount); 14101da177e4SLinus Torvalds 141138129a13SAl Viro static HLIST_HEAD(unmounted); /* protected by namespace_sem */ 1412e3197d83SAl Viro 141397216be0SAl Viro static void namespace_unlock(void) 14141da177e4SLinus Torvalds { 1415a3b3c562SEric W. Biederman struct hlist_head head; 141697216be0SAl Viro 1417a3b3c562SEric W. Biederman hlist_move_list(&unmounted, &head); 1418a3b3c562SEric W. Biederman 141997216be0SAl Viro up_write(&namespace_sem); 1420a3b3c562SEric W. Biederman 1421a3b3c562SEric W. Biederman if (likely(hlist_empty(&head))) 142297216be0SAl Viro return; 142397216be0SAl Viro 142448a066e7SAl Viro synchronize_rcu(); 142548a066e7SAl Viro 142687b95ce0SAl Viro group_pin_kill(&head); 142770fbcdf4SRam Pai } 142870fbcdf4SRam Pai 142997216be0SAl Viro static inline void namespace_lock(void) 1430e3197d83SAl Viro { 143197216be0SAl Viro down_write(&namespace_sem); 1432e3197d83SAl Viro } 1433e3197d83SAl Viro 1434e819f152SEric W. Biederman enum umount_tree_flags { 1435e819f152SEric W. Biederman UMOUNT_SYNC = 1, 1436e819f152SEric W. Biederman UMOUNT_PROPAGATE = 2, 1437e0c9c0afSEric W. Biederman UMOUNT_CONNECTED = 4, 1438e819f152SEric W. Biederman }; 1439f2d0a123SEric W. Biederman 1440f2d0a123SEric W. Biederman static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how) 1441f2d0a123SEric W. Biederman { 1442f2d0a123SEric W. Biederman /* Leaving mounts connected is only valid for lazy umounts */ 1443f2d0a123SEric W. Biederman if (how & UMOUNT_SYNC) 1444f2d0a123SEric W. Biederman return true; 1445f2d0a123SEric W. Biederman 1446f2d0a123SEric W. Biederman /* A mount without a parent has nothing to be connected to */ 1447f2d0a123SEric W. Biederman if (!mnt_has_parent(mnt)) 1448f2d0a123SEric W. Biederman return true; 1449f2d0a123SEric W. Biederman 1450f2d0a123SEric W. Biederman /* Because the reference counting rules change when mounts are 1451f2d0a123SEric W. Biederman * unmounted and connected, umounted mounts may not be 1452f2d0a123SEric W. Biederman * connected to mounted mounts. 1453f2d0a123SEric W. Biederman */ 1454f2d0a123SEric W. Biederman if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT)) 1455f2d0a123SEric W. Biederman return true; 1456f2d0a123SEric W. Biederman 1457f2d0a123SEric W. Biederman /* Has it been requested that the mount remain connected? */ 1458f2d0a123SEric W. Biederman if (how & UMOUNT_CONNECTED) 1459f2d0a123SEric W. Biederman return false; 1460f2d0a123SEric W. Biederman 1461f2d0a123SEric W. Biederman /* Is the mount locked such that it needs to remain connected? */ 1462f2d0a123SEric W. Biederman if (IS_MNT_LOCKED(mnt)) 1463f2d0a123SEric W. Biederman return false; 1464f2d0a123SEric W. Biederman 1465f2d0a123SEric W. Biederman /* By default disconnect the mount */ 1466f2d0a123SEric W. Biederman return true; 1467f2d0a123SEric W. Biederman } 1468f2d0a123SEric W. Biederman 146999b7db7bSNick Piggin /* 147048a066e7SAl Viro * mount_lock must be held 147199b7db7bSNick Piggin * namespace_sem must be held for write 147299b7db7bSNick Piggin */ 1473e819f152SEric W. Biederman static void umount_tree(struct mount *mnt, enum umount_tree_flags how) 147470fbcdf4SRam Pai { 1475c003b26fSEric W. Biederman LIST_HEAD(tmp_list); 1476315fc83eSAl Viro struct mount *p; 147770fbcdf4SRam Pai 14785d88457eSEric W. Biederman if (how & UMOUNT_PROPAGATE) 14795d88457eSEric W. Biederman propagate_mount_unlock(mnt); 14805d88457eSEric W. Biederman 1481c003b26fSEric W. Biederman /* Gather the mounts to umount */ 1482590ce4bcSEric W. Biederman for (p = mnt; p; p = next_mnt(p, mnt)) { 1483590ce4bcSEric W. Biederman p->mnt.mnt_flags |= MNT_UMOUNT; 1484c003b26fSEric W. Biederman list_move(&p->mnt_list, &tmp_list); 1485590ce4bcSEric W. Biederman } 1486c003b26fSEric W. Biederman 1487411a938bSEric W. Biederman /* Hide the mounts from mnt_mounts */ 1488c003b26fSEric W. Biederman list_for_each_entry(p, &tmp_list, mnt_list) { 1489c003b26fSEric W. Biederman list_del_init(&p->mnt_child); 149038129a13SAl Viro } 149170fbcdf4SRam Pai 1492c003b26fSEric W. Biederman /* Add propogated mounts to the tmp_list */ 1493e819f152SEric W. Biederman if (how & UMOUNT_PROPAGATE) 14947b8a53fdSAl Viro propagate_umount(&tmp_list); 1495a05964f3SRam Pai 1496c003b26fSEric W. Biederman while (!list_empty(&tmp_list)) { 1497d2921684SEric W. Biederman struct mnt_namespace *ns; 1498ce07d891SEric W. Biederman bool disconnect; 1499c003b26fSEric W. Biederman p = list_first_entry(&tmp_list, struct mount, mnt_list); 15006776db3dSAl Viro list_del_init(&p->mnt_expire); 15011a4eeaf2SAl Viro list_del_init(&p->mnt_list); 1502d2921684SEric W. Biederman ns = p->mnt_ns; 1503d2921684SEric W. Biederman if (ns) { 1504d2921684SEric W. Biederman ns->mounts--; 1505d2921684SEric W. Biederman __touch_mnt_namespace(ns); 1506d2921684SEric W. Biederman } 150763d37a84SAl Viro p->mnt_ns = NULL; 1508e819f152SEric W. Biederman if (how & UMOUNT_SYNC) 150948a066e7SAl Viro p->mnt.mnt_flags |= MNT_SYNC_UMOUNT; 151087b95ce0SAl Viro 1511f2d0a123SEric W. Biederman disconnect = disconnect_mount(p, how); 1512ce07d891SEric W. Biederman 1513ce07d891SEric W. Biederman pin_insert_group(&p->mnt_umount, &p->mnt_parent->mnt, 1514ce07d891SEric W. Biederman disconnect ? &unmounted : NULL); 1515676da58dSAl Viro if (mnt_has_parent(p)) { 151681b6b061SAl Viro mnt_add_count(p->mnt_parent, -1); 1517ce07d891SEric W. Biederman if (!disconnect) { 1518ce07d891SEric W. Biederman /* Don't forget about p */ 1519ce07d891SEric W. Biederman list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts); 1520ce07d891SEric W. Biederman } else { 15216a46c573SEric W. Biederman umount_mnt(p); 15227c4b93d8SAl Viro } 1523ce07d891SEric W. Biederman } 15240f0afb1dSAl Viro change_mnt_propagation(p, MS_PRIVATE); 152538129a13SAl Viro } 15261da177e4SLinus Torvalds } 15271da177e4SLinus Torvalds 1528b54b9be7SAl Viro static void shrink_submounts(struct mount *mnt); 1529c35038beSAl Viro 15301ab59738SAl Viro static int do_umount(struct mount *mnt, int flags) 15311da177e4SLinus Torvalds { 15321ab59738SAl Viro struct super_block *sb = mnt->mnt.mnt_sb; 15331da177e4SLinus Torvalds int retval; 15341da177e4SLinus Torvalds 15351ab59738SAl Viro retval = security_sb_umount(&mnt->mnt, flags); 15361da177e4SLinus Torvalds if (retval) 15371da177e4SLinus Torvalds return retval; 15381da177e4SLinus Torvalds 15391da177e4SLinus Torvalds /* 15401da177e4SLinus Torvalds * Allow userspace to request a mountpoint be expired rather than 15411da177e4SLinus Torvalds * unmounting unconditionally. Unmount only happens if: 15421da177e4SLinus Torvalds * (1) the mark is already set (the mark is cleared by mntput()) 15431da177e4SLinus Torvalds * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] 15441da177e4SLinus Torvalds */ 15451da177e4SLinus Torvalds if (flags & MNT_EXPIRE) { 15461ab59738SAl Viro if (&mnt->mnt == current->fs->root.mnt || 15471da177e4SLinus Torvalds flags & (MNT_FORCE | MNT_DETACH)) 15481da177e4SLinus Torvalds return -EINVAL; 15491da177e4SLinus Torvalds 1550b3e19d92SNick Piggin /* 1551b3e19d92SNick Piggin * probably don't strictly need the lock here if we examined 1552b3e19d92SNick Piggin * all race cases, but it's a slowpath. 1553b3e19d92SNick Piggin */ 1554719ea2fbSAl Viro lock_mount_hash(); 155583adc753SAl Viro if (mnt_get_count(mnt) != 2) { 1556719ea2fbSAl Viro unlock_mount_hash(); 15571da177e4SLinus Torvalds return -EBUSY; 1558b3e19d92SNick Piggin } 1559719ea2fbSAl Viro unlock_mount_hash(); 15601da177e4SLinus Torvalds 1561863d684fSAl Viro if (!xchg(&mnt->mnt_expiry_mark, 1)) 15621da177e4SLinus Torvalds return -EAGAIN; 15631da177e4SLinus Torvalds } 15641da177e4SLinus Torvalds 15651da177e4SLinus Torvalds /* 15661da177e4SLinus Torvalds * If we may have to abort operations to get out of this 15671da177e4SLinus Torvalds * mount, and they will themselves hold resources we must 15681da177e4SLinus Torvalds * allow the fs to do things. In the Unix tradition of 15691da177e4SLinus Torvalds * 'Gee thats tricky lets do it in userspace' the umount_begin 15701da177e4SLinus Torvalds * might fail to complete on the first run through as other tasks 15711da177e4SLinus Torvalds * must return, and the like. Thats for the mount program to worry 15721da177e4SLinus Torvalds * about for the moment. 15731da177e4SLinus Torvalds */ 15741da177e4SLinus Torvalds 157542faad99SAl Viro if (flags & MNT_FORCE && sb->s_op->umount_begin) { 157642faad99SAl Viro sb->s_op->umount_begin(sb); 157742faad99SAl Viro } 15781da177e4SLinus Torvalds 15791da177e4SLinus Torvalds /* 15801da177e4SLinus Torvalds * No sense to grab the lock for this test, but test itself looks 15811da177e4SLinus Torvalds * somewhat bogus. Suggestions for better replacement? 15821da177e4SLinus Torvalds * Ho-hum... In principle, we might treat that as umount + switch 15831da177e4SLinus Torvalds * to rootfs. GC would eventually take care of the old vfsmount. 15841da177e4SLinus Torvalds * Actually it makes sense, especially if rootfs would contain a 15851da177e4SLinus Torvalds * /reboot - static binary that would close all descriptors and 15861da177e4SLinus Torvalds * call reboot(9). Then init(8) could umount root and exec /reboot. 15871da177e4SLinus Torvalds */ 15881ab59738SAl Viro if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { 15891da177e4SLinus Torvalds /* 15901da177e4SLinus Torvalds * Special case for "unmounting" root ... 15911da177e4SLinus Torvalds * we just try to remount it readonly. 15921da177e4SLinus Torvalds */ 1593bc6155d1SEric W. Biederman if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) 1594a1480dccSAndy Lutomirski return -EPERM; 15951da177e4SLinus Torvalds down_write(&sb->s_umount); 1596bc98a42cSDavid Howells if (!sb_rdonly(sb)) 1597e462ec50SDavid Howells retval = do_remount_sb(sb, SB_RDONLY, NULL, 0); 15981da177e4SLinus Torvalds up_write(&sb->s_umount); 15991da177e4SLinus Torvalds return retval; 16001da177e4SLinus Torvalds } 16011da177e4SLinus Torvalds 160297216be0SAl Viro namespace_lock(); 1603719ea2fbSAl Viro lock_mount_hash(); 16045addc5ddSAl Viro event++; 16051da177e4SLinus Torvalds 160648a066e7SAl Viro if (flags & MNT_DETACH) { 160748a066e7SAl Viro if (!list_empty(&mnt->mnt_list)) 1608e819f152SEric W. Biederman umount_tree(mnt, UMOUNT_PROPAGATE); 160948a066e7SAl Viro retval = 0; 161048a066e7SAl Viro } else { 1611b54b9be7SAl Viro shrink_submounts(mnt); 16121da177e4SLinus Torvalds retval = -EBUSY; 161348a066e7SAl Viro if (!propagate_mount_busy(mnt, 2)) { 16141a4eeaf2SAl Viro if (!list_empty(&mnt->mnt_list)) 1615e819f152SEric W. Biederman umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC); 16161da177e4SLinus Torvalds retval = 0; 16171da177e4SLinus Torvalds } 161848a066e7SAl Viro } 1619719ea2fbSAl Viro unlock_mount_hash(); 1620e3197d83SAl Viro namespace_unlock(); 16211da177e4SLinus Torvalds return retval; 16221da177e4SLinus Torvalds } 16231da177e4SLinus Torvalds 16241da177e4SLinus Torvalds /* 162580b5dce8SEric W. Biederman * __detach_mounts - lazily unmount all mounts on the specified dentry 162680b5dce8SEric W. Biederman * 162780b5dce8SEric W. Biederman * During unlink, rmdir, and d_drop it is possible to loose the path 162880b5dce8SEric W. Biederman * to an existing mountpoint, and wind up leaking the mount. 162980b5dce8SEric W. Biederman * detach_mounts allows lazily unmounting those mounts instead of 163080b5dce8SEric W. Biederman * leaking them. 163180b5dce8SEric W. Biederman * 163280b5dce8SEric W. Biederman * The caller may hold dentry->d_inode->i_mutex. 163380b5dce8SEric W. Biederman */ 163480b5dce8SEric W. Biederman void __detach_mounts(struct dentry *dentry) 163580b5dce8SEric W. Biederman { 163680b5dce8SEric W. Biederman struct mountpoint *mp; 163780b5dce8SEric W. Biederman struct mount *mnt; 163880b5dce8SEric W. Biederman 163980b5dce8SEric W. Biederman namespace_lock(); 16403895dbf8SEric W. Biederman lock_mount_hash(); 164180b5dce8SEric W. Biederman mp = lookup_mountpoint(dentry); 1642f53e5797SEric W. Biederman if (IS_ERR_OR_NULL(mp)) 164380b5dce8SEric W. Biederman goto out_unlock; 164480b5dce8SEric W. Biederman 1645e06b933eSAndrey Ulanov event++; 164680b5dce8SEric W. Biederman while (!hlist_empty(&mp->m_list)) { 164780b5dce8SEric W. Biederman mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list); 1648ce07d891SEric W. Biederman if (mnt->mnt.mnt_flags & MNT_UMOUNT) { 1649fe78fcc8SEric W. Biederman hlist_add_head(&mnt->mnt_umount.s_list, &unmounted); 1650fe78fcc8SEric W. Biederman umount_mnt(mnt); 1651ce07d891SEric W. Biederman } 1652e0c9c0afSEric W. Biederman else umount_tree(mnt, UMOUNT_CONNECTED); 165380b5dce8SEric W. Biederman } 165480b5dce8SEric W. Biederman put_mountpoint(mp); 165580b5dce8SEric W. Biederman out_unlock: 16563895dbf8SEric W. Biederman unlock_mount_hash(); 165780b5dce8SEric W. Biederman namespace_unlock(); 165880b5dce8SEric W. Biederman } 165980b5dce8SEric W. Biederman 166080b5dce8SEric W. Biederman /* 16619b40bc90SAl Viro * Is the caller allowed to modify his namespace? 16629b40bc90SAl Viro */ 16639b40bc90SAl Viro static inline bool may_mount(void) 16649b40bc90SAl Viro { 16659b40bc90SAl Viro return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN); 16669b40bc90SAl Viro } 16679b40bc90SAl Viro 16689e8925b6SJeff Layton static inline bool may_mandlock(void) 16699e8925b6SJeff Layton { 16709e8925b6SJeff Layton #ifndef CONFIG_MANDATORY_FILE_LOCKING 16719e8925b6SJeff Layton return false; 16729e8925b6SJeff Layton #endif 167395ace754SEric W. Biederman return capable(CAP_SYS_ADMIN); 16749e8925b6SJeff Layton } 16759e8925b6SJeff Layton 16769b40bc90SAl Viro /* 16771da177e4SLinus Torvalds * Now umount can handle mount points as well as block devices. 16781da177e4SLinus Torvalds * This is important for filesystems which use unnamed block devices. 16791da177e4SLinus Torvalds * 16801da177e4SLinus Torvalds * We now support a flag for forced unmount like the other 'big iron' 16811da177e4SLinus Torvalds * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD 16821da177e4SLinus Torvalds */ 16831da177e4SLinus Torvalds 16843a18ef5cSDominik Brodowski int ksys_umount(char __user *name, int flags) 16851da177e4SLinus Torvalds { 16862d8f3038SAl Viro struct path path; 1687900148dcSAl Viro struct mount *mnt; 16881da177e4SLinus Torvalds int retval; 1689db1f05bbSMiklos Szeredi int lookup_flags = 0; 16901da177e4SLinus Torvalds 1691db1f05bbSMiklos Szeredi if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) 1692db1f05bbSMiklos Szeredi return -EINVAL; 1693db1f05bbSMiklos Szeredi 16949b40bc90SAl Viro if (!may_mount()) 16959b40bc90SAl Viro return -EPERM; 16969b40bc90SAl Viro 1697db1f05bbSMiklos Szeredi if (!(flags & UMOUNT_NOFOLLOW)) 1698db1f05bbSMiklos Szeredi lookup_flags |= LOOKUP_FOLLOW; 1699db1f05bbSMiklos Szeredi 1700197df04cSAl Viro retval = user_path_mountpoint_at(AT_FDCWD, name, lookup_flags, &path); 17011da177e4SLinus Torvalds if (retval) 17021da177e4SLinus Torvalds goto out; 1703900148dcSAl Viro mnt = real_mount(path.mnt); 17041da177e4SLinus Torvalds retval = -EINVAL; 17052d8f3038SAl Viro if (path.dentry != path.mnt->mnt_root) 17061da177e4SLinus Torvalds goto dput_and_out; 1707143c8c91SAl Viro if (!check_mnt(mnt)) 17081da177e4SLinus Torvalds goto dput_and_out; 17095ff9d8a6SEric W. Biederman if (mnt->mnt.mnt_flags & MNT_LOCKED) 17105ff9d8a6SEric W. Biederman goto dput_and_out; 1711b2f5d4dcSEric W. Biederman retval = -EPERM; 1712b2f5d4dcSEric W. Biederman if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN)) 1713b2f5d4dcSEric W. Biederman goto dput_and_out; 17141da177e4SLinus Torvalds 1715900148dcSAl Viro retval = do_umount(mnt, flags); 17161da177e4SLinus Torvalds dput_and_out: 1717429731b1SJan Blunck /* we mustn't call path_put() as that would clear mnt_expiry_mark */ 17182d8f3038SAl Viro dput(path.dentry); 1719900148dcSAl Viro mntput_no_expire(mnt); 17201da177e4SLinus Torvalds out: 17211da177e4SLinus Torvalds return retval; 17221da177e4SLinus Torvalds } 17231da177e4SLinus Torvalds 17243a18ef5cSDominik Brodowski SYSCALL_DEFINE2(umount, char __user *, name, int, flags) 17253a18ef5cSDominik Brodowski { 17263a18ef5cSDominik Brodowski return ksys_umount(name, flags); 17273a18ef5cSDominik Brodowski } 17283a18ef5cSDominik Brodowski 17291da177e4SLinus Torvalds #ifdef __ARCH_WANT_SYS_OLDUMOUNT 17301da177e4SLinus Torvalds 17311da177e4SLinus Torvalds /* 17321da177e4SLinus Torvalds * The 2.0 compatible umount. No flags. 17331da177e4SLinus Torvalds */ 1734bdc480e3SHeiko Carstens SYSCALL_DEFINE1(oldumount, char __user *, name) 17351da177e4SLinus Torvalds { 17363a18ef5cSDominik Brodowski return ksys_umount(name, 0); 17371da177e4SLinus Torvalds } 17381da177e4SLinus Torvalds 17391da177e4SLinus Torvalds #endif 17401da177e4SLinus Torvalds 17414ce5d2b1SEric W. Biederman static bool is_mnt_ns_file(struct dentry *dentry) 17428823c079SEric W. Biederman { 17434ce5d2b1SEric W. Biederman /* Is this a proxy for a mount namespace? */ 1744e149ed2bSAl Viro return dentry->d_op == &ns_dentry_operations && 1745e149ed2bSAl Viro dentry->d_fsdata == &mntns_operations; 17464ce5d2b1SEric W. Biederman } 17474ce5d2b1SEric W. Biederman 174858be2825SAl Viro struct mnt_namespace *to_mnt_ns(struct ns_common *ns) 174958be2825SAl Viro { 175058be2825SAl Viro return container_of(ns, struct mnt_namespace, ns); 175158be2825SAl Viro } 175258be2825SAl Viro 17534ce5d2b1SEric W. Biederman static bool mnt_ns_loop(struct dentry *dentry) 17544ce5d2b1SEric W. Biederman { 17554ce5d2b1SEric W. Biederman /* Could bind mounting the mount namespace inode cause a 17564ce5d2b1SEric W. Biederman * mount namespace loop? 17574ce5d2b1SEric W. Biederman */ 17584ce5d2b1SEric W. Biederman struct mnt_namespace *mnt_ns; 17594ce5d2b1SEric W. Biederman if (!is_mnt_ns_file(dentry)) 17604ce5d2b1SEric W. Biederman return false; 17614ce5d2b1SEric W. Biederman 1762f77c8014SAl Viro mnt_ns = to_mnt_ns(get_proc_ns(dentry->d_inode)); 17638823c079SEric W. Biederman return current->nsproxy->mnt_ns->seq >= mnt_ns->seq; 17648823c079SEric W. Biederman } 17658823c079SEric W. Biederman 176687129cc0SAl Viro struct mount *copy_tree(struct mount *mnt, struct dentry *dentry, 176736341f64SRam Pai int flag) 17681da177e4SLinus Torvalds { 176984d17192SAl Viro struct mount *res, *p, *q, *r, *parent; 17701da177e4SLinus Torvalds 17714ce5d2b1SEric W. Biederman if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt)) 17724ce5d2b1SEric W. Biederman return ERR_PTR(-EINVAL); 17734ce5d2b1SEric W. Biederman 17744ce5d2b1SEric W. Biederman if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry)) 1775be34d1a3SDavid Howells return ERR_PTR(-EINVAL); 17769676f0c6SRam Pai 177736341f64SRam Pai res = q = clone_mnt(mnt, dentry, flag); 1778be34d1a3SDavid Howells if (IS_ERR(q)) 1779be34d1a3SDavid Howells return q; 1780be34d1a3SDavid Howells 1781a73324daSAl Viro q->mnt_mountpoint = mnt->mnt_mountpoint; 17821da177e4SLinus Torvalds 17831da177e4SLinus Torvalds p = mnt; 17846b41d536SAl Viro list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { 1785315fc83eSAl Viro struct mount *s; 17867ec02ef1SJan Blunck if (!is_subdir(r->mnt_mountpoint, dentry)) 17871da177e4SLinus Torvalds continue; 17881da177e4SLinus Torvalds 1789909b0a88SAl Viro for (s = r; s; s = next_mnt(s, r)) { 17904ce5d2b1SEric W. Biederman if (!(flag & CL_COPY_UNBINDABLE) && 17914ce5d2b1SEric W. Biederman IS_MNT_UNBINDABLE(s)) { 17924ce5d2b1SEric W. Biederman s = skip_mnt_tree(s); 17934ce5d2b1SEric W. Biederman continue; 17944ce5d2b1SEric W. Biederman } 17954ce5d2b1SEric W. Biederman if (!(flag & CL_COPY_MNT_NS_FILE) && 17964ce5d2b1SEric W. Biederman is_mnt_ns_file(s->mnt.mnt_root)) { 17979676f0c6SRam Pai s = skip_mnt_tree(s); 17989676f0c6SRam Pai continue; 17999676f0c6SRam Pai } 18000714a533SAl Viro while (p != s->mnt_parent) { 18010714a533SAl Viro p = p->mnt_parent; 18020714a533SAl Viro q = q->mnt_parent; 18031da177e4SLinus Torvalds } 180487129cc0SAl Viro p = s; 180584d17192SAl Viro parent = q; 180687129cc0SAl Viro q = clone_mnt(p, p->mnt.mnt_root, flag); 1807be34d1a3SDavid Howells if (IS_ERR(q)) 1808be34d1a3SDavid Howells goto out; 1809719ea2fbSAl Viro lock_mount_hash(); 18101a4eeaf2SAl Viro list_add_tail(&q->mnt_list, &res->mnt_list); 18111064f874SEric W. Biederman attach_mnt(q, parent, p->mnt_mp); 1812719ea2fbSAl Viro unlock_mount_hash(); 18131da177e4SLinus Torvalds } 18141da177e4SLinus Torvalds } 18151da177e4SLinus Torvalds return res; 1816be34d1a3SDavid Howells out: 18171da177e4SLinus Torvalds if (res) { 1818719ea2fbSAl Viro lock_mount_hash(); 1819e819f152SEric W. Biederman umount_tree(res, UMOUNT_SYNC); 1820719ea2fbSAl Viro unlock_mount_hash(); 18211da177e4SLinus Torvalds } 1822be34d1a3SDavid Howells return q; 18231da177e4SLinus Torvalds } 18241da177e4SLinus Torvalds 1825be34d1a3SDavid Howells /* Caller should check returned pointer for errors */ 1826be34d1a3SDavid Howells 1827ca71cf71SAl Viro struct vfsmount *collect_mounts(const struct path *path) 18288aec0809SAl Viro { 1829cb338d06SAl Viro struct mount *tree; 183097216be0SAl Viro namespace_lock(); 1831cd4a4017SEric W. Biederman if (!check_mnt(real_mount(path->mnt))) 1832cd4a4017SEric W. Biederman tree = ERR_PTR(-EINVAL); 1833cd4a4017SEric W. Biederman else 183487129cc0SAl Viro tree = copy_tree(real_mount(path->mnt), path->dentry, 183587129cc0SAl Viro CL_COPY_ALL | CL_PRIVATE); 1836328e6d90SAl Viro namespace_unlock(); 1837be34d1a3SDavid Howells if (IS_ERR(tree)) 183852e220d3SDan Carpenter return ERR_CAST(tree); 1839be34d1a3SDavid Howells return &tree->mnt; 18408aec0809SAl Viro } 18418aec0809SAl Viro 18428aec0809SAl Viro void drop_collected_mounts(struct vfsmount *mnt) 18438aec0809SAl Viro { 184497216be0SAl Viro namespace_lock(); 1845719ea2fbSAl Viro lock_mount_hash(); 1846e819f152SEric W. Biederman umount_tree(real_mount(mnt), UMOUNT_SYNC); 1847719ea2fbSAl Viro unlock_mount_hash(); 18483ab6abeeSAl Viro namespace_unlock(); 18498aec0809SAl Viro } 18508aec0809SAl Viro 1851c771d683SMiklos Szeredi /** 1852c771d683SMiklos Szeredi * clone_private_mount - create a private clone of a path 1853c771d683SMiklos Szeredi * 1854c771d683SMiklos Szeredi * This creates a new vfsmount, which will be the clone of @path. The new will 1855c771d683SMiklos Szeredi * not be attached anywhere in the namespace and will be private (i.e. changes 1856c771d683SMiklos Szeredi * to the originating mount won't be propagated into this). 1857c771d683SMiklos Szeredi * 1858c771d683SMiklos Szeredi * Release with mntput(). 1859c771d683SMiklos Szeredi */ 1860ca71cf71SAl Viro struct vfsmount *clone_private_mount(const struct path *path) 1861c771d683SMiklos Szeredi { 1862c771d683SMiklos Szeredi struct mount *old_mnt = real_mount(path->mnt); 1863c771d683SMiklos Szeredi struct mount *new_mnt; 1864c771d683SMiklos Szeredi 1865c771d683SMiklos Szeredi if (IS_MNT_UNBINDABLE(old_mnt)) 1866c771d683SMiklos Szeredi return ERR_PTR(-EINVAL); 1867c771d683SMiklos Szeredi 1868c771d683SMiklos Szeredi new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE); 1869c771d683SMiklos Szeredi if (IS_ERR(new_mnt)) 1870c771d683SMiklos Szeredi return ERR_CAST(new_mnt); 1871c771d683SMiklos Szeredi 1872c771d683SMiklos Szeredi return &new_mnt->mnt; 1873c771d683SMiklos Szeredi } 1874c771d683SMiklos Szeredi EXPORT_SYMBOL_GPL(clone_private_mount); 1875c771d683SMiklos Szeredi 18761f707137SAl Viro int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, 18771f707137SAl Viro struct vfsmount *root) 18781f707137SAl Viro { 18791a4eeaf2SAl Viro struct mount *mnt; 18801f707137SAl Viro int res = f(root, arg); 18811f707137SAl Viro if (res) 18821f707137SAl Viro return res; 18831a4eeaf2SAl Viro list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) { 18841a4eeaf2SAl Viro res = f(&mnt->mnt, arg); 18851f707137SAl Viro if (res) 18861f707137SAl Viro return res; 18871f707137SAl Viro } 18881f707137SAl Viro return 0; 18891f707137SAl Viro } 18901f707137SAl Viro 18914b8b21f4SAl Viro static void cleanup_group_ids(struct mount *mnt, struct mount *end) 1892719f5d7fSMiklos Szeredi { 1893315fc83eSAl Viro struct mount *p; 1894719f5d7fSMiklos Szeredi 1895909b0a88SAl Viro for (p = mnt; p != end; p = next_mnt(p, mnt)) { 1896fc7be130SAl Viro if (p->mnt_group_id && !IS_MNT_SHARED(p)) 18974b8b21f4SAl Viro mnt_release_group_id(p); 1898719f5d7fSMiklos Szeredi } 1899719f5d7fSMiklos Szeredi } 1900719f5d7fSMiklos Szeredi 19014b8b21f4SAl Viro static int invent_group_ids(struct mount *mnt, bool recurse) 1902719f5d7fSMiklos Szeredi { 1903315fc83eSAl Viro struct mount *p; 1904719f5d7fSMiklos Szeredi 1905909b0a88SAl Viro for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { 1906fc7be130SAl Viro if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { 19074b8b21f4SAl Viro int err = mnt_alloc_group_id(p); 1908719f5d7fSMiklos Szeredi if (err) { 19094b8b21f4SAl Viro cleanup_group_ids(mnt, p); 1910719f5d7fSMiklos Szeredi return err; 1911719f5d7fSMiklos Szeredi } 1912719f5d7fSMiklos Szeredi } 1913719f5d7fSMiklos Szeredi } 1914719f5d7fSMiklos Szeredi 1915719f5d7fSMiklos Szeredi return 0; 1916719f5d7fSMiklos Szeredi } 1917719f5d7fSMiklos Szeredi 1918d2921684SEric W. Biederman int count_mounts(struct mnt_namespace *ns, struct mount *mnt) 1919d2921684SEric W. Biederman { 1920d2921684SEric W. Biederman unsigned int max = READ_ONCE(sysctl_mount_max); 1921d2921684SEric W. Biederman unsigned int mounts = 0, old, pending, sum; 1922d2921684SEric W. Biederman struct mount *p; 1923d2921684SEric W. Biederman 1924d2921684SEric W. Biederman for (p = mnt; p; p = next_mnt(p, mnt)) 1925d2921684SEric W. Biederman mounts++; 1926d2921684SEric W. Biederman 1927d2921684SEric W. Biederman old = ns->mounts; 1928d2921684SEric W. Biederman pending = ns->pending_mounts; 1929d2921684SEric W. Biederman sum = old + pending; 1930d2921684SEric W. Biederman if ((old > sum) || 1931d2921684SEric W. Biederman (pending > sum) || 1932d2921684SEric W. Biederman (max < sum) || 1933d2921684SEric W. Biederman (mounts > (max - sum))) 1934d2921684SEric W. Biederman return -ENOSPC; 1935d2921684SEric W. Biederman 1936d2921684SEric W. Biederman ns->pending_mounts = pending + mounts; 1937d2921684SEric W. Biederman return 0; 1938d2921684SEric W. Biederman } 1939d2921684SEric W. Biederman 1940b90fa9aeSRam Pai /* 1941b90fa9aeSRam Pai * @source_mnt : mount tree to be attached 1942b90fa9aeSRam Pai * @nd : place the mount tree @source_mnt is attached 194321444403SRam Pai * @parent_nd : if non-null, detach the source_mnt from its parent and 194421444403SRam Pai * store the parent mount and mountpoint dentry. 194521444403SRam Pai * (done when source_mnt is moved) 1946b90fa9aeSRam Pai * 1947b90fa9aeSRam Pai * NOTE: in the table below explains the semantics when a source mount 1948b90fa9aeSRam Pai * of a given type is attached to a destination mount of a given type. 19499676f0c6SRam Pai * --------------------------------------------------------------------------- 1950b90fa9aeSRam Pai * | BIND MOUNT OPERATION | 19519676f0c6SRam Pai * |************************************************************************** 19529676f0c6SRam Pai * | source-->| shared | private | slave | unbindable | 19539676f0c6SRam Pai * | dest | | | | | 19549676f0c6SRam Pai * | | | | | | | 19559676f0c6SRam Pai * | v | | | | | 19569676f0c6SRam Pai * |************************************************************************** 19579676f0c6SRam Pai * | shared | shared (++) | shared (+) | shared(+++)| invalid | 19585afe0022SRam Pai * | | | | | | 19599676f0c6SRam Pai * |non-shared| shared (+) | private | slave (*) | invalid | 19609676f0c6SRam Pai * *************************************************************************** 1961b90fa9aeSRam Pai * A bind operation clones the source mount and mounts the clone on the 1962b90fa9aeSRam Pai * destination mount. 1963b90fa9aeSRam Pai * 1964b90fa9aeSRam Pai * (++) the cloned mount is propagated to all the mounts in the propagation 1965b90fa9aeSRam Pai * tree of the destination mount and the cloned mount is added to 1966b90fa9aeSRam Pai * the peer group of the source mount. 1967b90fa9aeSRam Pai * (+) the cloned mount is created under the destination mount and is marked 1968b90fa9aeSRam Pai * as shared. The cloned mount is added to the peer group of the source 1969b90fa9aeSRam Pai * mount. 19705afe0022SRam Pai * (+++) the mount is propagated to all the mounts in the propagation tree 19715afe0022SRam Pai * of the destination mount and the cloned mount is made slave 19725afe0022SRam Pai * of the same master as that of the source mount. The cloned mount 19735afe0022SRam Pai * is marked as 'shared and slave'. 19745afe0022SRam Pai * (*) the cloned mount is made a slave of the same master as that of the 19755afe0022SRam Pai * source mount. 19765afe0022SRam Pai * 19779676f0c6SRam Pai * --------------------------------------------------------------------------- 197821444403SRam Pai * | MOVE MOUNT OPERATION | 19799676f0c6SRam Pai * |************************************************************************** 19809676f0c6SRam Pai * | source-->| shared | private | slave | unbindable | 19819676f0c6SRam Pai * | dest | | | | | 19829676f0c6SRam Pai * | | | | | | | 19839676f0c6SRam Pai * | v | | | | | 19849676f0c6SRam Pai * |************************************************************************** 19859676f0c6SRam Pai * | shared | shared (+) | shared (+) | shared(+++) | invalid | 19865afe0022SRam Pai * | | | | | | 19879676f0c6SRam Pai * |non-shared| shared (+*) | private | slave (*) | unbindable | 19889676f0c6SRam Pai * *************************************************************************** 19895afe0022SRam Pai * 19905afe0022SRam Pai * (+) the mount is moved to the destination. And is then propagated to 19915afe0022SRam Pai * all the mounts in the propagation tree of the destination mount. 199221444403SRam Pai * (+*) the mount is moved to the destination. 19935afe0022SRam Pai * (+++) the mount is moved to the destination and is then propagated to 19945afe0022SRam Pai * all the mounts belonging to the destination mount's propagation tree. 19955afe0022SRam Pai * the mount is marked as 'shared and slave'. 19965afe0022SRam Pai * (*) the mount continues to be a slave at the new location. 1997b90fa9aeSRam Pai * 1998b90fa9aeSRam Pai * if the source mount is a tree, the operations explained above is 1999b90fa9aeSRam Pai * applied to each mount in the tree. 2000b90fa9aeSRam Pai * Must be called without spinlocks held, since this function can sleep 2001b90fa9aeSRam Pai * in allocations. 2002b90fa9aeSRam Pai */ 20030fb54e50SAl Viro static int attach_recursive_mnt(struct mount *source_mnt, 200484d17192SAl Viro struct mount *dest_mnt, 200584d17192SAl Viro struct mountpoint *dest_mp, 200684d17192SAl Viro struct path *parent_path) 2007b90fa9aeSRam Pai { 200838129a13SAl Viro HLIST_HEAD(tree_list); 2009d2921684SEric W. Biederman struct mnt_namespace *ns = dest_mnt->mnt_ns; 20101064f874SEric W. Biederman struct mountpoint *smp; 2011315fc83eSAl Viro struct mount *child, *p; 201238129a13SAl Viro struct hlist_node *n; 2013719f5d7fSMiklos Szeredi int err; 2014b90fa9aeSRam Pai 20151064f874SEric W. Biederman /* Preallocate a mountpoint in case the new mounts need 20161064f874SEric W. Biederman * to be tucked under other mounts. 20171064f874SEric W. Biederman */ 20181064f874SEric W. Biederman smp = get_mountpoint(source_mnt->mnt.mnt_root); 20191064f874SEric W. Biederman if (IS_ERR(smp)) 20201064f874SEric W. Biederman return PTR_ERR(smp); 20211064f874SEric W. Biederman 2022d2921684SEric W. Biederman /* Is there space to add these mounts to the mount namespace? */ 2023d2921684SEric W. Biederman if (!parent_path) { 2024d2921684SEric W. Biederman err = count_mounts(ns, source_mnt); 2025d2921684SEric W. Biederman if (err) 2026d2921684SEric W. Biederman goto out; 2027d2921684SEric W. Biederman } 2028d2921684SEric W. Biederman 2029fc7be130SAl Viro if (IS_MNT_SHARED(dest_mnt)) { 20300fb54e50SAl Viro err = invent_group_ids(source_mnt, true); 2031719f5d7fSMiklos Szeredi if (err) 2032719f5d7fSMiklos Szeredi goto out; 203384d17192SAl Viro err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list); 2034f2ebb3a9SAl Viro lock_mount_hash(); 2035719f5d7fSMiklos Szeredi if (err) 2036719f5d7fSMiklos Szeredi goto out_cleanup_ids; 2037909b0a88SAl Viro for (p = source_mnt; p; p = next_mnt(p, source_mnt)) 20380f0afb1dSAl Viro set_mnt_shared(p); 20390b1b901bSAl Viro } else { 20400b1b901bSAl Viro lock_mount_hash(); 2041b90fa9aeSRam Pai } 20421a390689SAl Viro if (parent_path) { 20430fb54e50SAl Viro detach_mnt(source_mnt, parent_path); 204484d17192SAl Viro attach_mnt(source_mnt, dest_mnt, dest_mp); 2045143c8c91SAl Viro touch_mnt_namespace(source_mnt->mnt_ns); 204621444403SRam Pai } else { 204784d17192SAl Viro mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt); 20481064f874SEric W. Biederman commit_tree(source_mnt); 204921444403SRam Pai } 2050b90fa9aeSRam Pai 205138129a13SAl Viro hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) { 20521d6a32acSAl Viro struct mount *q; 205338129a13SAl Viro hlist_del_init(&child->mnt_hash); 20541064f874SEric W. Biederman q = __lookup_mnt(&child->mnt_parent->mnt, 20551d6a32acSAl Viro child->mnt_mountpoint); 20561064f874SEric W. Biederman if (q) 20571064f874SEric W. Biederman mnt_change_mountpoint(child, smp, q); 20581064f874SEric W. Biederman commit_tree(child); 2059b90fa9aeSRam Pai } 20601064f874SEric W. Biederman put_mountpoint(smp); 2061719ea2fbSAl Viro unlock_mount_hash(); 206299b7db7bSNick Piggin 2063b90fa9aeSRam Pai return 0; 2064719f5d7fSMiklos Szeredi 2065719f5d7fSMiklos Szeredi out_cleanup_ids: 2066f2ebb3a9SAl Viro while (!hlist_empty(&tree_list)) { 2067f2ebb3a9SAl Viro child = hlist_entry(tree_list.first, struct mount, mnt_hash); 2068d2921684SEric W. Biederman child->mnt_parent->mnt_ns->pending_mounts = 0; 2069e819f152SEric W. Biederman umount_tree(child, UMOUNT_SYNC); 2070f2ebb3a9SAl Viro } 2071f2ebb3a9SAl Viro unlock_mount_hash(); 20720fb54e50SAl Viro cleanup_group_ids(source_mnt, NULL); 2073719f5d7fSMiklos Szeredi out: 2074d2921684SEric W. Biederman ns->pending_mounts = 0; 20751064f874SEric W. Biederman 20761064f874SEric W. Biederman read_seqlock_excl(&mount_lock); 20771064f874SEric W. Biederman put_mountpoint(smp); 20781064f874SEric W. Biederman read_sequnlock_excl(&mount_lock); 20791064f874SEric W. Biederman 2080719f5d7fSMiklos Szeredi return err; 2081b90fa9aeSRam Pai } 2082b90fa9aeSRam Pai 208384d17192SAl Viro static struct mountpoint *lock_mount(struct path *path) 2084b12cea91SAl Viro { 2085b12cea91SAl Viro struct vfsmount *mnt; 208684d17192SAl Viro struct dentry *dentry = path->dentry; 2087b12cea91SAl Viro retry: 20885955102cSAl Viro inode_lock(dentry->d_inode); 208984d17192SAl Viro if (unlikely(cant_mount(dentry))) { 20905955102cSAl Viro inode_unlock(dentry->d_inode); 209184d17192SAl Viro return ERR_PTR(-ENOENT); 2092b12cea91SAl Viro } 209397216be0SAl Viro namespace_lock(); 2094b12cea91SAl Viro mnt = lookup_mnt(path); 209584d17192SAl Viro if (likely(!mnt)) { 20963895dbf8SEric W. Biederman struct mountpoint *mp = get_mountpoint(dentry); 209784d17192SAl Viro if (IS_ERR(mp)) { 209897216be0SAl Viro namespace_unlock(); 20995955102cSAl Viro inode_unlock(dentry->d_inode); 210084d17192SAl Viro return mp; 210184d17192SAl Viro } 210284d17192SAl Viro return mp; 210384d17192SAl Viro } 210497216be0SAl Viro namespace_unlock(); 21055955102cSAl Viro inode_unlock(path->dentry->d_inode); 2106b12cea91SAl Viro path_put(path); 2107b12cea91SAl Viro path->mnt = mnt; 210884d17192SAl Viro dentry = path->dentry = dget(mnt->mnt_root); 2109b12cea91SAl Viro goto retry; 2110b12cea91SAl Viro } 2111b12cea91SAl Viro 211284d17192SAl Viro static void unlock_mount(struct mountpoint *where) 2113b12cea91SAl Viro { 211484d17192SAl Viro struct dentry *dentry = where->m_dentry; 21153895dbf8SEric W. Biederman 21163895dbf8SEric W. Biederman read_seqlock_excl(&mount_lock); 211784d17192SAl Viro put_mountpoint(where); 21183895dbf8SEric W. Biederman read_sequnlock_excl(&mount_lock); 21193895dbf8SEric W. Biederman 2120328e6d90SAl Viro namespace_unlock(); 21215955102cSAl Viro inode_unlock(dentry->d_inode); 2122b12cea91SAl Viro } 2123b12cea91SAl Viro 212484d17192SAl Viro static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp) 21251da177e4SLinus Torvalds { 2126e462ec50SDavid Howells if (mnt->mnt.mnt_sb->s_flags & SB_NOUSER) 21271da177e4SLinus Torvalds return -EINVAL; 21281da177e4SLinus Torvalds 2129e36cb0b8SDavid Howells if (d_is_dir(mp->m_dentry) != 2130e36cb0b8SDavid Howells d_is_dir(mnt->mnt.mnt_root)) 21311da177e4SLinus Torvalds return -ENOTDIR; 21321da177e4SLinus Torvalds 213384d17192SAl Viro return attach_recursive_mnt(mnt, p, mp, NULL); 21341da177e4SLinus Torvalds } 21351da177e4SLinus Torvalds 21361da177e4SLinus Torvalds /* 21377a2e8a8fSValerie Aurora * Sanity check the flags to change_mnt_propagation. 21387a2e8a8fSValerie Aurora */ 21397a2e8a8fSValerie Aurora 2140e462ec50SDavid Howells static int flags_to_propagation_type(int ms_flags) 21417a2e8a8fSValerie Aurora { 2142e462ec50SDavid Howells int type = ms_flags & ~(MS_REC | MS_SILENT); 21437a2e8a8fSValerie Aurora 21447a2e8a8fSValerie Aurora /* Fail if any non-propagation flags are set */ 21457a2e8a8fSValerie Aurora if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) 21467a2e8a8fSValerie Aurora return 0; 21477a2e8a8fSValerie Aurora /* Only one propagation flag should be set */ 21487a2e8a8fSValerie Aurora if (!is_power_of_2(type)) 21497a2e8a8fSValerie Aurora return 0; 21507a2e8a8fSValerie Aurora return type; 21517a2e8a8fSValerie Aurora } 21527a2e8a8fSValerie Aurora 21537a2e8a8fSValerie Aurora /* 215407b20889SRam Pai * recursively change the type of the mountpoint. 215507b20889SRam Pai */ 2156e462ec50SDavid Howells static int do_change_type(struct path *path, int ms_flags) 215707b20889SRam Pai { 2158315fc83eSAl Viro struct mount *m; 21594b8b21f4SAl Viro struct mount *mnt = real_mount(path->mnt); 2160e462ec50SDavid Howells int recurse = ms_flags & MS_REC; 21617a2e8a8fSValerie Aurora int type; 2162719f5d7fSMiklos Szeredi int err = 0; 216307b20889SRam Pai 21642d92ab3cSAl Viro if (path->dentry != path->mnt->mnt_root) 216507b20889SRam Pai return -EINVAL; 216607b20889SRam Pai 2167e462ec50SDavid Howells type = flags_to_propagation_type(ms_flags); 21687a2e8a8fSValerie Aurora if (!type) 21697a2e8a8fSValerie Aurora return -EINVAL; 21707a2e8a8fSValerie Aurora 217197216be0SAl Viro namespace_lock(); 2172719f5d7fSMiklos Szeredi if (type == MS_SHARED) { 2173719f5d7fSMiklos Szeredi err = invent_group_ids(mnt, recurse); 2174719f5d7fSMiklos Szeredi if (err) 2175719f5d7fSMiklos Szeredi goto out_unlock; 2176719f5d7fSMiklos Szeredi } 2177719f5d7fSMiklos Szeredi 2178719ea2fbSAl Viro lock_mount_hash(); 2179909b0a88SAl Viro for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) 21800f0afb1dSAl Viro change_mnt_propagation(m, type); 2181719ea2fbSAl Viro unlock_mount_hash(); 2182719f5d7fSMiklos Szeredi 2183719f5d7fSMiklos Szeredi out_unlock: 218497216be0SAl Viro namespace_unlock(); 2185719f5d7fSMiklos Szeredi return err; 218607b20889SRam Pai } 218707b20889SRam Pai 21885ff9d8a6SEric W. Biederman static bool has_locked_children(struct mount *mnt, struct dentry *dentry) 21895ff9d8a6SEric W. Biederman { 21905ff9d8a6SEric W. Biederman struct mount *child; 21915ff9d8a6SEric W. Biederman list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { 21925ff9d8a6SEric W. Biederman if (!is_subdir(child->mnt_mountpoint, dentry)) 21935ff9d8a6SEric W. Biederman continue; 21945ff9d8a6SEric W. Biederman 21955ff9d8a6SEric W. Biederman if (child->mnt.mnt_flags & MNT_LOCKED) 21965ff9d8a6SEric W. Biederman return true; 21975ff9d8a6SEric W. Biederman } 21985ff9d8a6SEric W. Biederman return false; 21995ff9d8a6SEric W. Biederman } 22005ff9d8a6SEric W. Biederman 220107b20889SRam Pai /* 22021da177e4SLinus Torvalds * do loopback mount. 22031da177e4SLinus Torvalds */ 2204808d4e3cSAl Viro static int do_loopback(struct path *path, const char *old_name, 22052dafe1c4SEric Sandeen int recurse) 22061da177e4SLinus Torvalds { 22072d92ab3cSAl Viro struct path old_path; 220884d17192SAl Viro struct mount *mnt = NULL, *old, *parent; 220984d17192SAl Viro struct mountpoint *mp; 221057eccb83SAl Viro int err; 22111da177e4SLinus Torvalds if (!old_name || !*old_name) 22121da177e4SLinus Torvalds return -EINVAL; 2213815d405cSTrond Myklebust err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); 22141da177e4SLinus Torvalds if (err) 22151da177e4SLinus Torvalds return err; 22161da177e4SLinus Torvalds 22178823c079SEric W. Biederman err = -EINVAL; 22184ce5d2b1SEric W. Biederman if (mnt_ns_loop(old_path.dentry)) 22198823c079SEric W. Biederman goto out; 22208823c079SEric W. Biederman 222184d17192SAl Viro mp = lock_mount(path); 222284d17192SAl Viro err = PTR_ERR(mp); 222384d17192SAl Viro if (IS_ERR(mp)) 22249676f0c6SRam Pai goto out; 22259676f0c6SRam Pai 222687129cc0SAl Viro old = real_mount(old_path.mnt); 222784d17192SAl Viro parent = real_mount(path->mnt); 222887129cc0SAl Viro 2229b12cea91SAl Viro err = -EINVAL; 2230fc7be130SAl Viro if (IS_MNT_UNBINDABLE(old)) 2231b12cea91SAl Viro goto out2; 2232b12cea91SAl Viro 2233e149ed2bSAl Viro if (!check_mnt(parent)) 2234e149ed2bSAl Viro goto out2; 2235e149ed2bSAl Viro 2236e149ed2bSAl Viro if (!check_mnt(old) && old_path.dentry->d_op != &ns_dentry_operations) 2237b12cea91SAl Viro goto out2; 2238ccd48bc7SAl Viro 22395ff9d8a6SEric W. Biederman if (!recurse && has_locked_children(old, old_path.dentry)) 22405ff9d8a6SEric W. Biederman goto out2; 22415ff9d8a6SEric W. Biederman 22421da177e4SLinus Torvalds if (recurse) 22434ce5d2b1SEric W. Biederman mnt = copy_tree(old, old_path.dentry, CL_COPY_MNT_NS_FILE); 22441da177e4SLinus Torvalds else 224587129cc0SAl Viro mnt = clone_mnt(old, old_path.dentry, 0); 22461da177e4SLinus Torvalds 2247be34d1a3SDavid Howells if (IS_ERR(mnt)) { 2248be34d1a3SDavid Howells err = PTR_ERR(mnt); 2249e9c5d8a5SAndrey Vagin goto out2; 2250be34d1a3SDavid Howells } 2251ccd48bc7SAl Viro 22525ff9d8a6SEric W. Biederman mnt->mnt.mnt_flags &= ~MNT_LOCKED; 22535ff9d8a6SEric W. Biederman 225484d17192SAl Viro err = graft_tree(mnt, parent, mp); 22551da177e4SLinus Torvalds if (err) { 2256719ea2fbSAl Viro lock_mount_hash(); 2257e819f152SEric W. Biederman umount_tree(mnt, UMOUNT_SYNC); 2258719ea2fbSAl Viro unlock_mount_hash(); 22595b83d2c5SRam Pai } 2260b12cea91SAl Viro out2: 226184d17192SAl Viro unlock_mount(mp); 2262ccd48bc7SAl Viro out: 22632d92ab3cSAl Viro path_put(&old_path); 22641da177e4SLinus Torvalds return err; 22651da177e4SLinus Torvalds } 22661da177e4SLinus Torvalds 22672e4b7fcdSDave Hansen static int change_mount_flags(struct vfsmount *mnt, int ms_flags) 22682e4b7fcdSDave Hansen { 22692e4b7fcdSDave Hansen int error = 0; 22702e4b7fcdSDave Hansen int readonly_request = 0; 22712e4b7fcdSDave Hansen 22722e4b7fcdSDave Hansen if (ms_flags & MS_RDONLY) 22732e4b7fcdSDave Hansen readonly_request = 1; 22742e4b7fcdSDave Hansen if (readonly_request == __mnt_is_readonly(mnt)) 22752e4b7fcdSDave Hansen return 0; 22762e4b7fcdSDave Hansen 22772e4b7fcdSDave Hansen if (readonly_request) 227883adc753SAl Viro error = mnt_make_readonly(real_mount(mnt)); 22792e4b7fcdSDave Hansen else 228083adc753SAl Viro __mnt_unmake_readonly(real_mount(mnt)); 22812e4b7fcdSDave Hansen return error; 22822e4b7fcdSDave Hansen } 22832e4b7fcdSDave Hansen 22841da177e4SLinus Torvalds /* 22851da177e4SLinus Torvalds * change filesystem flags. dir should be a physical root of filesystem. 22861da177e4SLinus Torvalds * If you've mounted a non-root directory somewhere and want to do remount 22871da177e4SLinus Torvalds * on it - tough luck. 22881da177e4SLinus Torvalds */ 2289e462ec50SDavid Howells static int do_remount(struct path *path, int ms_flags, int sb_flags, 2290e462ec50SDavid Howells int mnt_flags, void *data) 22911da177e4SLinus Torvalds { 22921da177e4SLinus Torvalds int err; 22932d92ab3cSAl Viro struct super_block *sb = path->mnt->mnt_sb; 2294143c8c91SAl Viro struct mount *mnt = real_mount(path->mnt); 22951da177e4SLinus Torvalds 2296143c8c91SAl Viro if (!check_mnt(mnt)) 22971da177e4SLinus Torvalds return -EINVAL; 22981da177e4SLinus Torvalds 22992d92ab3cSAl Viro if (path->dentry != path->mnt->mnt_root) 23001da177e4SLinus Torvalds return -EINVAL; 23011da177e4SLinus Torvalds 230207b64558SEric W. Biederman /* Don't allow changing of locked mnt flags. 230307b64558SEric W. Biederman * 230407b64558SEric W. Biederman * No locks need to be held here while testing the various 230507b64558SEric W. Biederman * MNT_LOCK flags because those flags can never be cleared 230607b64558SEric W. Biederman * once they are set. 230707b64558SEric W. Biederman */ 230807b64558SEric W. Biederman if ((mnt->mnt.mnt_flags & MNT_LOCK_READONLY) && 230907b64558SEric W. Biederman !(mnt_flags & MNT_READONLY)) { 231007b64558SEric W. Biederman return -EPERM; 231107b64558SEric W. Biederman } 23129566d674SEric W. Biederman if ((mnt->mnt.mnt_flags & MNT_LOCK_NODEV) && 23139566d674SEric W. Biederman !(mnt_flags & MNT_NODEV)) { 23149566d674SEric W. Biederman return -EPERM; 23159566d674SEric W. Biederman } 23169566d674SEric W. Biederman if ((mnt->mnt.mnt_flags & MNT_LOCK_NOSUID) && 23179566d674SEric W. Biederman !(mnt_flags & MNT_NOSUID)) { 23189566d674SEric W. Biederman return -EPERM; 23199566d674SEric W. Biederman } 23209566d674SEric W. Biederman if ((mnt->mnt.mnt_flags & MNT_LOCK_NOEXEC) && 23219566d674SEric W. Biederman !(mnt_flags & MNT_NOEXEC)) { 23229566d674SEric W. Biederman return -EPERM; 23239566d674SEric W. Biederman } 23249566d674SEric W. Biederman if ((mnt->mnt.mnt_flags & MNT_LOCK_ATIME) && 23259566d674SEric W. Biederman ((mnt->mnt.mnt_flags & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK))) { 23269566d674SEric W. Biederman return -EPERM; 23279566d674SEric W. Biederman } 23289566d674SEric W. Biederman 2329ff36fe2cSEric Paris err = security_sb_remount(sb, data); 2330ff36fe2cSEric Paris if (err) 2331ff36fe2cSEric Paris return err; 2332ff36fe2cSEric Paris 23331da177e4SLinus Torvalds down_write(&sb->s_umount); 2334e462ec50SDavid Howells if (ms_flags & MS_BIND) 2335e462ec50SDavid Howells err = change_mount_flags(path->mnt, ms_flags); 2336bc6155d1SEric W. Biederman else if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) 233757eccb83SAl Viro err = -EPERM; 23384aa98cf7SAl Viro else 2339e462ec50SDavid Howells err = do_remount_sb(sb, sb_flags, data, 0); 23407b43a79fSAl Viro if (!err) { 2341719ea2fbSAl Viro lock_mount_hash(); 2342a6138db8SEric W. Biederman mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK; 2343143c8c91SAl Viro mnt->mnt.mnt_flags = mnt_flags; 2344143c8c91SAl Viro touch_mnt_namespace(mnt->mnt_ns); 2345719ea2fbSAl Viro unlock_mount_hash(); 23460e55a7ccSDan Williams } 23476339dab8SAl Viro up_write(&sb->s_umount); 23481da177e4SLinus Torvalds return err; 23491da177e4SLinus Torvalds } 23501da177e4SLinus Torvalds 2351cbbe362cSAl Viro static inline int tree_contains_unbindable(struct mount *mnt) 23529676f0c6SRam Pai { 2353315fc83eSAl Viro struct mount *p; 2354909b0a88SAl Viro for (p = mnt; p; p = next_mnt(p, mnt)) { 2355fc7be130SAl Viro if (IS_MNT_UNBINDABLE(p)) 23569676f0c6SRam Pai return 1; 23579676f0c6SRam Pai } 23589676f0c6SRam Pai return 0; 23599676f0c6SRam Pai } 23609676f0c6SRam Pai 2361808d4e3cSAl Viro static int do_move_mount(struct path *path, const char *old_name) 23621da177e4SLinus Torvalds { 23632d92ab3cSAl Viro struct path old_path, parent_path; 2364676da58dSAl Viro struct mount *p; 23650fb54e50SAl Viro struct mount *old; 236684d17192SAl Viro struct mountpoint *mp; 236757eccb83SAl Viro int err; 23681da177e4SLinus Torvalds if (!old_name || !*old_name) 23691da177e4SLinus Torvalds return -EINVAL; 23702d92ab3cSAl Viro err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); 23711da177e4SLinus Torvalds if (err) 23721da177e4SLinus Torvalds return err; 23731da177e4SLinus Torvalds 237484d17192SAl Viro mp = lock_mount(path); 237584d17192SAl Viro err = PTR_ERR(mp); 237684d17192SAl Viro if (IS_ERR(mp)) 2377cc53ce53SDavid Howells goto out; 2378cc53ce53SDavid Howells 2379143c8c91SAl Viro old = real_mount(old_path.mnt); 2380fc7be130SAl Viro p = real_mount(path->mnt); 2381143c8c91SAl Viro 23821da177e4SLinus Torvalds err = -EINVAL; 2383fc7be130SAl Viro if (!check_mnt(p) || !check_mnt(old)) 23841da177e4SLinus Torvalds goto out1; 23851da177e4SLinus Torvalds 23865ff9d8a6SEric W. Biederman if (old->mnt.mnt_flags & MNT_LOCKED) 23875ff9d8a6SEric W. Biederman goto out1; 23885ff9d8a6SEric W. Biederman 23891da177e4SLinus Torvalds err = -EINVAL; 23902d92ab3cSAl Viro if (old_path.dentry != old_path.mnt->mnt_root) 239121444403SRam Pai goto out1; 23921da177e4SLinus Torvalds 2393676da58dSAl Viro if (!mnt_has_parent(old)) 239421444403SRam Pai goto out1; 23951da177e4SLinus Torvalds 2396e36cb0b8SDavid Howells if (d_is_dir(path->dentry) != 2397e36cb0b8SDavid Howells d_is_dir(old_path.dentry)) 239821444403SRam Pai goto out1; 239921444403SRam Pai /* 240021444403SRam Pai * Don't move a mount residing in a shared parent. 240121444403SRam Pai */ 2402fc7be130SAl Viro if (IS_MNT_SHARED(old->mnt_parent)) 240321444403SRam Pai goto out1; 24049676f0c6SRam Pai /* 24059676f0c6SRam Pai * Don't move a mount tree containing unbindable mounts to a destination 24069676f0c6SRam Pai * mount which is shared. 24079676f0c6SRam Pai */ 2408fc7be130SAl Viro if (IS_MNT_SHARED(p) && tree_contains_unbindable(old)) 24099676f0c6SRam Pai goto out1; 24101da177e4SLinus Torvalds err = -ELOOP; 2411fc7be130SAl Viro for (; mnt_has_parent(p); p = p->mnt_parent) 2412676da58dSAl Viro if (p == old) 241321444403SRam Pai goto out1; 24141da177e4SLinus Torvalds 241584d17192SAl Viro err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path); 24164ac91378SJan Blunck if (err) 241721444403SRam Pai goto out1; 24181da177e4SLinus Torvalds 24191da177e4SLinus Torvalds /* if the mount is moved, it should no longer be expire 24201da177e4SLinus Torvalds * automatically */ 24216776db3dSAl Viro list_del_init(&old->mnt_expire); 24221da177e4SLinus Torvalds out1: 242384d17192SAl Viro unlock_mount(mp); 24241da177e4SLinus Torvalds out: 24251da177e4SLinus Torvalds if (!err) 24261a390689SAl Viro path_put(&parent_path); 24272d92ab3cSAl Viro path_put(&old_path); 24281da177e4SLinus Torvalds return err; 24291da177e4SLinus Torvalds } 24301da177e4SLinus Torvalds 24319d412a43SAl Viro static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype) 24329d412a43SAl Viro { 24339d412a43SAl Viro int err; 24349d412a43SAl Viro const char *subtype = strchr(fstype, '.'); 24359d412a43SAl Viro if (subtype) { 24369d412a43SAl Viro subtype++; 24379d412a43SAl Viro err = -EINVAL; 24389d412a43SAl Viro if (!subtype[0]) 24399d412a43SAl Viro goto err; 24409d412a43SAl Viro } else 24419d412a43SAl Viro subtype = ""; 24429d412a43SAl Viro 24439d412a43SAl Viro mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL); 24449d412a43SAl Viro err = -ENOMEM; 24459d412a43SAl Viro if (!mnt->mnt_sb->s_subtype) 24469d412a43SAl Viro goto err; 24479d412a43SAl Viro return mnt; 24489d412a43SAl Viro 24499d412a43SAl Viro err: 24509d412a43SAl Viro mntput(mnt); 24519d412a43SAl Viro return ERR_PTR(err); 24529d412a43SAl Viro } 24539d412a43SAl Viro 24549d412a43SAl Viro /* 24559d412a43SAl Viro * add a mount into a namespace's mount tree 24569d412a43SAl Viro */ 245795bc5f25SAl Viro static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags) 24589d412a43SAl Viro { 245984d17192SAl Viro struct mountpoint *mp; 246084d17192SAl Viro struct mount *parent; 24619d412a43SAl Viro int err; 24629d412a43SAl Viro 2463f2ebb3a9SAl Viro mnt_flags &= ~MNT_INTERNAL_FLAGS; 24649d412a43SAl Viro 246584d17192SAl Viro mp = lock_mount(path); 246684d17192SAl Viro if (IS_ERR(mp)) 246784d17192SAl Viro return PTR_ERR(mp); 24689d412a43SAl Viro 246984d17192SAl Viro parent = real_mount(path->mnt); 24709d412a43SAl Viro err = -EINVAL; 247184d17192SAl Viro if (unlikely(!check_mnt(parent))) { 2472156cacb1SAl Viro /* that's acceptable only for automounts done in private ns */ 2473156cacb1SAl Viro if (!(mnt_flags & MNT_SHRINKABLE)) 24749d412a43SAl Viro goto unlock; 2475156cacb1SAl Viro /* ... and for those we'd better have mountpoint still alive */ 247684d17192SAl Viro if (!parent->mnt_ns) 2477156cacb1SAl Viro goto unlock; 2478156cacb1SAl Viro } 24799d412a43SAl Viro 24809d412a43SAl Viro /* Refuse the same filesystem on the same mount point */ 24819d412a43SAl Viro err = -EBUSY; 248295bc5f25SAl Viro if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && 24839d412a43SAl Viro path->mnt->mnt_root == path->dentry) 24849d412a43SAl Viro goto unlock; 24859d412a43SAl Viro 24869d412a43SAl Viro err = -EINVAL; 2487e36cb0b8SDavid Howells if (d_is_symlink(newmnt->mnt.mnt_root)) 24889d412a43SAl Viro goto unlock; 24899d412a43SAl Viro 249095bc5f25SAl Viro newmnt->mnt.mnt_flags = mnt_flags; 249184d17192SAl Viro err = graft_tree(newmnt, parent, mp); 24929d412a43SAl Viro 24939d412a43SAl Viro unlock: 249484d17192SAl Viro unlock_mount(mp); 24959d412a43SAl Viro return err; 24969d412a43SAl Viro } 2497b1e75df4SAl Viro 24988654df4eSEric W. Biederman static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags); 24991b852bceSEric W. Biederman 25001da177e4SLinus Torvalds /* 25011da177e4SLinus Torvalds * create a new mount for userspace and request it to be added into the 25021da177e4SLinus Torvalds * namespace's tree 25031da177e4SLinus Torvalds */ 2504e462ec50SDavid Howells static int do_new_mount(struct path *path, const char *fstype, int sb_flags, 2505808d4e3cSAl Viro int mnt_flags, const char *name, void *data) 25061da177e4SLinus Torvalds { 25070c55cfc4SEric W. Biederman struct file_system_type *type; 25081da177e4SLinus Torvalds struct vfsmount *mnt; 250915f9a3f3SAl Viro int err; 25101da177e4SLinus Torvalds 25110c55cfc4SEric W. Biederman if (!fstype) 25121da177e4SLinus Torvalds return -EINVAL; 25131da177e4SLinus Torvalds 25140c55cfc4SEric W. Biederman type = get_fs_type(fstype); 25150c55cfc4SEric W. Biederman if (!type) 25160c55cfc4SEric W. Biederman return -ENODEV; 25170c55cfc4SEric W. Biederman 2518e462ec50SDavid Howells mnt = vfs_kern_mount(type, sb_flags, name, data); 25190c55cfc4SEric W. Biederman if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && 25200c55cfc4SEric W. Biederman !mnt->mnt_sb->s_subtype) 25210c55cfc4SEric W. Biederman mnt = fs_set_subtype(mnt, fstype); 25220c55cfc4SEric W. Biederman 25230c55cfc4SEric W. Biederman put_filesystem(type); 25241da177e4SLinus Torvalds if (IS_ERR(mnt)) 25251da177e4SLinus Torvalds return PTR_ERR(mnt); 25261da177e4SLinus Torvalds 25278654df4eSEric W. Biederman if (mount_too_revealing(mnt, &mnt_flags)) { 25288654df4eSEric W. Biederman mntput(mnt); 25298654df4eSEric W. Biederman return -EPERM; 25308654df4eSEric W. Biederman } 25318654df4eSEric W. Biederman 253295bc5f25SAl Viro err = do_add_mount(real_mount(mnt), path, mnt_flags); 253315f9a3f3SAl Viro if (err) 253415f9a3f3SAl Viro mntput(mnt); 253515f9a3f3SAl Viro return err; 25361da177e4SLinus Torvalds } 25371da177e4SLinus Torvalds 253819a167afSAl Viro int finish_automount(struct vfsmount *m, struct path *path) 253919a167afSAl Viro { 25406776db3dSAl Viro struct mount *mnt = real_mount(m); 254119a167afSAl Viro int err; 254219a167afSAl Viro /* The new mount record should have at least 2 refs to prevent it being 254319a167afSAl Viro * expired before we get a chance to add it 254419a167afSAl Viro */ 25456776db3dSAl Viro BUG_ON(mnt_get_count(mnt) < 2); 254619a167afSAl Viro 254719a167afSAl Viro if (m->mnt_sb == path->mnt->mnt_sb && 254819a167afSAl Viro m->mnt_root == path->dentry) { 2549b1e75df4SAl Viro err = -ELOOP; 2550b1e75df4SAl Viro goto fail; 255119a167afSAl Viro } 255219a167afSAl Viro 255395bc5f25SAl Viro err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE); 2554b1e75df4SAl Viro if (!err) 2555b1e75df4SAl Viro return 0; 2556b1e75df4SAl Viro fail: 2557b1e75df4SAl Viro /* remove m from any expiration list it may be on */ 25586776db3dSAl Viro if (!list_empty(&mnt->mnt_expire)) { 255997216be0SAl Viro namespace_lock(); 25606776db3dSAl Viro list_del_init(&mnt->mnt_expire); 256197216be0SAl Viro namespace_unlock(); 256219a167afSAl Viro } 2563b1e75df4SAl Viro mntput(m); 2564b1e75df4SAl Viro mntput(m); 256519a167afSAl Viro return err; 256619a167afSAl Viro } 256719a167afSAl Viro 2568ea5b778aSDavid Howells /** 2569ea5b778aSDavid Howells * mnt_set_expiry - Put a mount on an expiration list 2570ea5b778aSDavid Howells * @mnt: The mount to list. 2571ea5b778aSDavid Howells * @expiry_list: The list to add the mount to. 2572ea5b778aSDavid Howells */ 2573ea5b778aSDavid Howells void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list) 2574ea5b778aSDavid Howells { 257597216be0SAl Viro namespace_lock(); 2576ea5b778aSDavid Howells 25776776db3dSAl Viro list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list); 2578ea5b778aSDavid Howells 257997216be0SAl Viro namespace_unlock(); 2580ea5b778aSDavid Howells } 2581ea5b778aSDavid Howells EXPORT_SYMBOL(mnt_set_expiry); 2582ea5b778aSDavid Howells 2583ea5b778aSDavid Howells /* 25841da177e4SLinus Torvalds * process a list of expirable mountpoints with the intent of discarding any 25851da177e4SLinus Torvalds * mountpoints that aren't in use and haven't been touched since last we came 25861da177e4SLinus Torvalds * here 25871da177e4SLinus Torvalds */ 25881da177e4SLinus Torvalds void mark_mounts_for_expiry(struct list_head *mounts) 25891da177e4SLinus Torvalds { 2590761d5c38SAl Viro struct mount *mnt, *next; 25911da177e4SLinus Torvalds LIST_HEAD(graveyard); 25921da177e4SLinus Torvalds 25931da177e4SLinus Torvalds if (list_empty(mounts)) 25941da177e4SLinus Torvalds return; 25951da177e4SLinus Torvalds 259697216be0SAl Viro namespace_lock(); 2597719ea2fbSAl Viro lock_mount_hash(); 25981da177e4SLinus Torvalds 25991da177e4SLinus Torvalds /* extract from the expiration list every vfsmount that matches the 26001da177e4SLinus Torvalds * following criteria: 26011da177e4SLinus Torvalds * - only referenced by its parent vfsmount 26021da177e4SLinus Torvalds * - still marked for expiry (marked on the last call here; marks are 26031da177e4SLinus Torvalds * cleared by mntput()) 26041da177e4SLinus Torvalds */ 26056776db3dSAl Viro list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { 2606863d684fSAl Viro if (!xchg(&mnt->mnt_expiry_mark, 1) || 26071ab59738SAl Viro propagate_mount_busy(mnt, 1)) 26081da177e4SLinus Torvalds continue; 26096776db3dSAl Viro list_move(&mnt->mnt_expire, &graveyard); 26101da177e4SLinus Torvalds } 2611bcc5c7d2SAl Viro while (!list_empty(&graveyard)) { 26126776db3dSAl Viro mnt = list_first_entry(&graveyard, struct mount, mnt_expire); 2613143c8c91SAl Viro touch_mnt_namespace(mnt->mnt_ns); 2614e819f152SEric W. Biederman umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC); 2615bcc5c7d2SAl Viro } 2616719ea2fbSAl Viro unlock_mount_hash(); 26173ab6abeeSAl Viro namespace_unlock(); 26181da177e4SLinus Torvalds } 26191da177e4SLinus Torvalds 26201da177e4SLinus Torvalds EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); 26211da177e4SLinus Torvalds 26221da177e4SLinus Torvalds /* 26235528f911STrond Myklebust * Ripoff of 'select_parent()' 26245528f911STrond Myklebust * 26255528f911STrond Myklebust * search the list of submounts for a given mountpoint, and move any 26265528f911STrond Myklebust * shrinkable submounts to the 'graveyard' list. 26275528f911STrond Myklebust */ 2628692afc31SAl Viro static int select_submounts(struct mount *parent, struct list_head *graveyard) 26295528f911STrond Myklebust { 2630692afc31SAl Viro struct mount *this_parent = parent; 26315528f911STrond Myklebust struct list_head *next; 26325528f911STrond Myklebust int found = 0; 26335528f911STrond Myklebust 26345528f911STrond Myklebust repeat: 26356b41d536SAl Viro next = this_parent->mnt_mounts.next; 26365528f911STrond Myklebust resume: 26376b41d536SAl Viro while (next != &this_parent->mnt_mounts) { 26385528f911STrond Myklebust struct list_head *tmp = next; 26396b41d536SAl Viro struct mount *mnt = list_entry(tmp, struct mount, mnt_child); 26405528f911STrond Myklebust 26415528f911STrond Myklebust next = tmp->next; 2642692afc31SAl Viro if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE)) 26435528f911STrond Myklebust continue; 26445528f911STrond Myklebust /* 26455528f911STrond Myklebust * Descend a level if the d_mounts list is non-empty. 26465528f911STrond Myklebust */ 26476b41d536SAl Viro if (!list_empty(&mnt->mnt_mounts)) { 26485528f911STrond Myklebust this_parent = mnt; 26495528f911STrond Myklebust goto repeat; 26505528f911STrond Myklebust } 26515528f911STrond Myklebust 26521ab59738SAl Viro if (!propagate_mount_busy(mnt, 1)) { 26536776db3dSAl Viro list_move_tail(&mnt->mnt_expire, graveyard); 26545528f911STrond Myklebust found++; 26555528f911STrond Myklebust } 26565528f911STrond Myklebust } 26575528f911STrond Myklebust /* 26585528f911STrond Myklebust * All done at this level ... ascend and resume the search 26595528f911STrond Myklebust */ 26605528f911STrond Myklebust if (this_parent != parent) { 26616b41d536SAl Viro next = this_parent->mnt_child.next; 26620714a533SAl Viro this_parent = this_parent->mnt_parent; 26635528f911STrond Myklebust goto resume; 26645528f911STrond Myklebust } 26655528f911STrond Myklebust return found; 26665528f911STrond Myklebust } 26675528f911STrond Myklebust 26685528f911STrond Myklebust /* 26695528f911STrond Myklebust * process a list of expirable mountpoints with the intent of discarding any 26705528f911STrond Myklebust * submounts of a specific parent mountpoint 267199b7db7bSNick Piggin * 267248a066e7SAl Viro * mount_lock must be held for write 26735528f911STrond Myklebust */ 2674b54b9be7SAl Viro static void shrink_submounts(struct mount *mnt) 26755528f911STrond Myklebust { 26765528f911STrond Myklebust LIST_HEAD(graveyard); 2677761d5c38SAl Viro struct mount *m; 26785528f911STrond Myklebust 26795528f911STrond Myklebust /* extract submounts of 'mountpoint' from the expiration list */ 2680c35038beSAl Viro while (select_submounts(mnt, &graveyard)) { 2681bcc5c7d2SAl Viro while (!list_empty(&graveyard)) { 2682761d5c38SAl Viro m = list_first_entry(&graveyard, struct mount, 26836776db3dSAl Viro mnt_expire); 2684143c8c91SAl Viro touch_mnt_namespace(m->mnt_ns); 2685e819f152SEric W. Biederman umount_tree(m, UMOUNT_PROPAGATE|UMOUNT_SYNC); 2686bcc5c7d2SAl Viro } 2687bcc5c7d2SAl Viro } 26885528f911STrond Myklebust } 26895528f911STrond Myklebust 26905528f911STrond Myklebust /* 26911da177e4SLinus Torvalds * Some copy_from_user() implementations do not return the exact number of 26921da177e4SLinus Torvalds * bytes remaining to copy on a fault. But copy_mount_options() requires that. 26931da177e4SLinus Torvalds * Note that this function differs from copy_from_user() in that it will oops 26941da177e4SLinus Torvalds * on bad values of `to', rather than returning a short copy. 26951da177e4SLinus Torvalds */ 2696b58fed8bSRam Pai static long exact_copy_from_user(void *to, const void __user * from, 2697b58fed8bSRam Pai unsigned long n) 26981da177e4SLinus Torvalds { 26991da177e4SLinus Torvalds char *t = to; 27001da177e4SLinus Torvalds const char __user *f = from; 27011da177e4SLinus Torvalds char c; 27021da177e4SLinus Torvalds 27031da177e4SLinus Torvalds if (!access_ok(VERIFY_READ, from, n)) 27041da177e4SLinus Torvalds return n; 27051da177e4SLinus Torvalds 27061da177e4SLinus Torvalds while (n) { 27071da177e4SLinus Torvalds if (__get_user(c, f)) { 27081da177e4SLinus Torvalds memset(t, 0, n); 27091da177e4SLinus Torvalds break; 27101da177e4SLinus Torvalds } 27111da177e4SLinus Torvalds *t++ = c; 27121da177e4SLinus Torvalds f++; 27131da177e4SLinus Torvalds n--; 27141da177e4SLinus Torvalds } 27151da177e4SLinus Torvalds return n; 27161da177e4SLinus Torvalds } 27171da177e4SLinus Torvalds 2718b40ef869SAl Viro void *copy_mount_options(const void __user * data) 27191da177e4SLinus Torvalds { 27201da177e4SLinus Torvalds int i; 27211da177e4SLinus Torvalds unsigned long size; 2722b40ef869SAl Viro char *copy; 27231da177e4SLinus Torvalds 27241da177e4SLinus Torvalds if (!data) 2725b40ef869SAl Viro return NULL; 27261da177e4SLinus Torvalds 2727b40ef869SAl Viro copy = kmalloc(PAGE_SIZE, GFP_KERNEL); 2728b40ef869SAl Viro if (!copy) 2729b40ef869SAl Viro return ERR_PTR(-ENOMEM); 27301da177e4SLinus Torvalds 27311da177e4SLinus Torvalds /* We only care that *some* data at the address the user 27321da177e4SLinus Torvalds * gave us is valid. Just in case, we'll zero 27331da177e4SLinus Torvalds * the remainder of the page. 27341da177e4SLinus Torvalds */ 27351da177e4SLinus Torvalds /* copy_from_user cannot cross TASK_SIZE ! */ 27361da177e4SLinus Torvalds size = TASK_SIZE - (unsigned long)data; 27371da177e4SLinus Torvalds if (size > PAGE_SIZE) 27381da177e4SLinus Torvalds size = PAGE_SIZE; 27391da177e4SLinus Torvalds 2740b40ef869SAl Viro i = size - exact_copy_from_user(copy, data, size); 27411da177e4SLinus Torvalds if (!i) { 2742b40ef869SAl Viro kfree(copy); 2743b40ef869SAl Viro return ERR_PTR(-EFAULT); 27441da177e4SLinus Torvalds } 27451da177e4SLinus Torvalds if (i != PAGE_SIZE) 2746b40ef869SAl Viro memset(copy + i, 0, PAGE_SIZE - i); 2747b40ef869SAl Viro return copy; 27481da177e4SLinus Torvalds } 27491da177e4SLinus Torvalds 2750b8850d1fSTim Gardner char *copy_mount_string(const void __user *data) 2751eca6f534SVegard Nossum { 2752b8850d1fSTim Gardner return data ? strndup_user(data, PAGE_SIZE) : NULL; 2753eca6f534SVegard Nossum } 2754eca6f534SVegard Nossum 27551da177e4SLinus Torvalds /* 27561da177e4SLinus Torvalds * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to 27571da177e4SLinus Torvalds * be given to the mount() call (ie: read-only, no-dev, no-suid etc). 27581da177e4SLinus Torvalds * 27591da177e4SLinus Torvalds * data is a (void *) that can point to any structure up to 27601da177e4SLinus Torvalds * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent 27611da177e4SLinus Torvalds * information (or be NULL). 27621da177e4SLinus Torvalds * 27631da177e4SLinus Torvalds * Pre-0.97 versions of mount() didn't have a flags word. 27641da177e4SLinus Torvalds * When the flags word was introduced its top half was required 27651da177e4SLinus Torvalds * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. 27661da177e4SLinus Torvalds * Therefore, if this magic number is present, it carries no information 27671da177e4SLinus Torvalds * and must be discarded. 27681da177e4SLinus Torvalds */ 27695e6123f3SSeunghun Lee long do_mount(const char *dev_name, const char __user *dir_name, 2770808d4e3cSAl Viro const char *type_page, unsigned long flags, void *data_page) 27711da177e4SLinus Torvalds { 27722d92ab3cSAl Viro struct path path; 2773e462ec50SDavid Howells unsigned int mnt_flags = 0, sb_flags; 27741da177e4SLinus Torvalds int retval = 0; 27751da177e4SLinus Torvalds 27761da177e4SLinus Torvalds /* Discard magic */ 27771da177e4SLinus Torvalds if ((flags & MS_MGC_MSK) == MS_MGC_VAL) 27781da177e4SLinus Torvalds flags &= ~MS_MGC_MSK; 27791da177e4SLinus Torvalds 27801da177e4SLinus Torvalds /* Basic sanity checks */ 27811da177e4SLinus Torvalds if (data_page) 27821da177e4SLinus Torvalds ((char *)data_page)[PAGE_SIZE - 1] = 0; 27831da177e4SLinus Torvalds 2784e462ec50SDavid Howells if (flags & MS_NOUSER) 2785e462ec50SDavid Howells return -EINVAL; 2786e462ec50SDavid Howells 2787a27ab9f2STetsuo Handa /* ... and get the mountpoint */ 27885e6123f3SSeunghun Lee retval = user_path(dir_name, &path); 2789a27ab9f2STetsuo Handa if (retval) 2790a27ab9f2STetsuo Handa return retval; 2791a27ab9f2STetsuo Handa 2792a27ab9f2STetsuo Handa retval = security_sb_mount(dev_name, &path, 2793a27ab9f2STetsuo Handa type_page, flags, data_page); 27940d5cadb8SAl Viro if (!retval && !may_mount()) 27950d5cadb8SAl Viro retval = -EPERM; 2796e462ec50SDavid Howells if (!retval && (flags & SB_MANDLOCK) && !may_mandlock()) 27979e8925b6SJeff Layton retval = -EPERM; 2798a27ab9f2STetsuo Handa if (retval) 2799a27ab9f2STetsuo Handa goto dput_out; 2800a27ab9f2STetsuo Handa 2801613cbe3dSAndi Kleen /* Default to relatime unless overriden */ 2802613cbe3dSAndi Kleen if (!(flags & MS_NOATIME)) 28030a1c01c9SMatthew Garrett mnt_flags |= MNT_RELATIME; 28040a1c01c9SMatthew Garrett 28051da177e4SLinus Torvalds /* Separate the per-mountpoint flags */ 28061da177e4SLinus Torvalds if (flags & MS_NOSUID) 28071da177e4SLinus Torvalds mnt_flags |= MNT_NOSUID; 28081da177e4SLinus Torvalds if (flags & MS_NODEV) 28091da177e4SLinus Torvalds mnt_flags |= MNT_NODEV; 28101da177e4SLinus Torvalds if (flags & MS_NOEXEC) 28111da177e4SLinus Torvalds mnt_flags |= MNT_NOEXEC; 2812fc33a7bbSChristoph Hellwig if (flags & MS_NOATIME) 2813fc33a7bbSChristoph Hellwig mnt_flags |= MNT_NOATIME; 2814fc33a7bbSChristoph Hellwig if (flags & MS_NODIRATIME) 2815fc33a7bbSChristoph Hellwig mnt_flags |= MNT_NODIRATIME; 2816d0adde57SMatthew Garrett if (flags & MS_STRICTATIME) 2817d0adde57SMatthew Garrett mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); 2818a9e5b732SDavid Howells if (flags & MS_RDONLY) 28192e4b7fcdSDave Hansen mnt_flags |= MNT_READONLY; 2820fc33a7bbSChristoph Hellwig 2821ffbc6f0eSEric W. Biederman /* The default atime for remount is preservation */ 2822ffbc6f0eSEric W. Biederman if ((flags & MS_REMOUNT) && 2823ffbc6f0eSEric W. Biederman ((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME | 2824ffbc6f0eSEric W. Biederman MS_STRICTATIME)) == 0)) { 2825ffbc6f0eSEric W. Biederman mnt_flags &= ~MNT_ATIME_MASK; 2826ffbc6f0eSEric W. Biederman mnt_flags |= path.mnt->mnt_flags & MNT_ATIME_MASK; 2827ffbc6f0eSEric W. Biederman } 2828ffbc6f0eSEric W. Biederman 2829e462ec50SDavid Howells sb_flags = flags & (SB_RDONLY | 2830e462ec50SDavid Howells SB_SYNCHRONOUS | 2831e462ec50SDavid Howells SB_MANDLOCK | 2832e462ec50SDavid Howells SB_DIRSYNC | 2833e462ec50SDavid Howells SB_SILENT | 2834917086ffSMimi Zohar SB_POSIXACL | 2835d7ee9469SMarkus Trippelsdorf SB_LAZYTIME | 2836917086ffSMimi Zohar SB_I_VERSION); 28371da177e4SLinus Torvalds 28381da177e4SLinus Torvalds if (flags & MS_REMOUNT) 2839e462ec50SDavid Howells retval = do_remount(&path, flags, sb_flags, mnt_flags, 28401da177e4SLinus Torvalds data_page); 28411da177e4SLinus Torvalds else if (flags & MS_BIND) 28422d92ab3cSAl Viro retval = do_loopback(&path, dev_name, flags & MS_REC); 28439676f0c6SRam Pai else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) 28442d92ab3cSAl Viro retval = do_change_type(&path, flags); 28451da177e4SLinus Torvalds else if (flags & MS_MOVE) 28462d92ab3cSAl Viro retval = do_move_mount(&path, dev_name); 28471da177e4SLinus Torvalds else 2848e462ec50SDavid Howells retval = do_new_mount(&path, type_page, sb_flags, mnt_flags, 28491da177e4SLinus Torvalds dev_name, data_page); 28501da177e4SLinus Torvalds dput_out: 28512d92ab3cSAl Viro path_put(&path); 28521da177e4SLinus Torvalds return retval; 28531da177e4SLinus Torvalds } 28541da177e4SLinus Torvalds 2855537f7ccbSEric W. Biederman static struct ucounts *inc_mnt_namespaces(struct user_namespace *ns) 2856537f7ccbSEric W. Biederman { 2857537f7ccbSEric W. Biederman return inc_ucount(ns, current_euid(), UCOUNT_MNT_NAMESPACES); 2858537f7ccbSEric W. Biederman } 2859537f7ccbSEric W. Biederman 2860537f7ccbSEric W. Biederman static void dec_mnt_namespaces(struct ucounts *ucounts) 2861537f7ccbSEric W. Biederman { 2862537f7ccbSEric W. Biederman dec_ucount(ucounts, UCOUNT_MNT_NAMESPACES); 2863537f7ccbSEric W. Biederman } 2864537f7ccbSEric W. Biederman 2865771b1371SEric W. Biederman static void free_mnt_ns(struct mnt_namespace *ns) 2866771b1371SEric W. Biederman { 28676344c433SAl Viro ns_free_inum(&ns->ns); 2868537f7ccbSEric W. Biederman dec_mnt_namespaces(ns->ucounts); 2869771b1371SEric W. Biederman put_user_ns(ns->user_ns); 2870771b1371SEric W. Biederman kfree(ns); 2871771b1371SEric W. Biederman } 2872771b1371SEric W. Biederman 28738823c079SEric W. Biederman /* 28748823c079SEric W. Biederman * Assign a sequence number so we can detect when we attempt to bind 28758823c079SEric W. Biederman * mount a reference to an older mount namespace into the current 28768823c079SEric W. Biederman * mount namespace, preventing reference counting loops. A 64bit 28778823c079SEric W. Biederman * number incrementing at 10Ghz will take 12,427 years to wrap which 28788823c079SEric W. Biederman * is effectively never, so we can ignore the possibility. 28798823c079SEric W. Biederman */ 28808823c079SEric W. Biederman static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1); 28818823c079SEric W. Biederman 2882771b1371SEric W. Biederman static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns) 2883cf8d2c11STrond Myklebust { 2884cf8d2c11STrond Myklebust struct mnt_namespace *new_ns; 2885537f7ccbSEric W. Biederman struct ucounts *ucounts; 288698f842e6SEric W. Biederman int ret; 2887cf8d2c11STrond Myklebust 2888537f7ccbSEric W. Biederman ucounts = inc_mnt_namespaces(user_ns); 2889537f7ccbSEric W. Biederman if (!ucounts) 2890df75e774SEric W. Biederman return ERR_PTR(-ENOSPC); 2891537f7ccbSEric W. Biederman 2892cf8d2c11STrond Myklebust new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); 2893537f7ccbSEric W. Biederman if (!new_ns) { 2894537f7ccbSEric W. Biederman dec_mnt_namespaces(ucounts); 2895cf8d2c11STrond Myklebust return ERR_PTR(-ENOMEM); 2896537f7ccbSEric W. Biederman } 28976344c433SAl Viro ret = ns_alloc_inum(&new_ns->ns); 289898f842e6SEric W. Biederman if (ret) { 289998f842e6SEric W. Biederman kfree(new_ns); 2900537f7ccbSEric W. Biederman dec_mnt_namespaces(ucounts); 290198f842e6SEric W. Biederman return ERR_PTR(ret); 290298f842e6SEric W. Biederman } 290333c42940SAl Viro new_ns->ns.ops = &mntns_operations; 29048823c079SEric W. Biederman new_ns->seq = atomic64_add_return(1, &mnt_ns_seq); 2905cf8d2c11STrond Myklebust atomic_set(&new_ns->count, 1); 2906cf8d2c11STrond Myklebust new_ns->root = NULL; 2907cf8d2c11STrond Myklebust INIT_LIST_HEAD(&new_ns->list); 2908cf8d2c11STrond Myklebust init_waitqueue_head(&new_ns->poll); 2909cf8d2c11STrond Myklebust new_ns->event = 0; 2910771b1371SEric W. Biederman new_ns->user_ns = get_user_ns(user_ns); 2911537f7ccbSEric W. Biederman new_ns->ucounts = ucounts; 2912d2921684SEric W. Biederman new_ns->mounts = 0; 2913d2921684SEric W. Biederman new_ns->pending_mounts = 0; 2914cf8d2c11STrond Myklebust return new_ns; 2915cf8d2c11STrond Myklebust } 2916cf8d2c11STrond Myklebust 29170766f788SEmese Revfy __latent_entropy 29189559f689SAl Viro struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, 29199559f689SAl Viro struct user_namespace *user_ns, struct fs_struct *new_fs) 29201da177e4SLinus Torvalds { 29216b3286edSKirill Korotaev struct mnt_namespace *new_ns; 29227f2da1e7SAl Viro struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; 2923315fc83eSAl Viro struct mount *p, *q; 29249559f689SAl Viro struct mount *old; 2925cb338d06SAl Viro struct mount *new; 29267a472ef4SEric W. Biederman int copy_flags; 29271da177e4SLinus Torvalds 29289559f689SAl Viro BUG_ON(!ns); 29299559f689SAl Viro 29309559f689SAl Viro if (likely(!(flags & CLONE_NEWNS))) { 29319559f689SAl Viro get_mnt_ns(ns); 29329559f689SAl Viro return ns; 29339559f689SAl Viro } 29349559f689SAl Viro 29359559f689SAl Viro old = ns->root; 29369559f689SAl Viro 2937771b1371SEric W. Biederman new_ns = alloc_mnt_ns(user_ns); 2938cf8d2c11STrond Myklebust if (IS_ERR(new_ns)) 2939cf8d2c11STrond Myklebust return new_ns; 29401da177e4SLinus Torvalds 294197216be0SAl Viro namespace_lock(); 29421da177e4SLinus Torvalds /* First pass: copy the tree topology */ 29434ce5d2b1SEric W. Biederman copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE; 29449559f689SAl Viro if (user_ns != ns->user_ns) 2945132c94e3SEric W. Biederman copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED; 29467a472ef4SEric W. Biederman new = copy_tree(old, old->mnt.mnt_root, copy_flags); 2947be34d1a3SDavid Howells if (IS_ERR(new)) { 2948328e6d90SAl Viro namespace_unlock(); 2949771b1371SEric W. Biederman free_mnt_ns(new_ns); 2950be34d1a3SDavid Howells return ERR_CAST(new); 29511da177e4SLinus Torvalds } 2952be08d6d2SAl Viro new_ns->root = new; 29531a4eeaf2SAl Viro list_add_tail(&new_ns->list, &new->mnt_list); 29541da177e4SLinus Torvalds 29551da177e4SLinus Torvalds /* 29561da177e4SLinus Torvalds * Second pass: switch the tsk->fs->* elements and mark new vfsmounts 29571da177e4SLinus Torvalds * as belonging to new namespace. We have already acquired a private 29581da177e4SLinus Torvalds * fs_struct, so tsk->fs->lock is not needed. 29591da177e4SLinus Torvalds */ 2960909b0a88SAl Viro p = old; 2961cb338d06SAl Viro q = new; 29621da177e4SLinus Torvalds while (p) { 2963143c8c91SAl Viro q->mnt_ns = new_ns; 2964d2921684SEric W. Biederman new_ns->mounts++; 29659559f689SAl Viro if (new_fs) { 29669559f689SAl Viro if (&p->mnt == new_fs->root.mnt) { 29679559f689SAl Viro new_fs->root.mnt = mntget(&q->mnt); 2968315fc83eSAl Viro rootmnt = &p->mnt; 29691da177e4SLinus Torvalds } 29709559f689SAl Viro if (&p->mnt == new_fs->pwd.mnt) { 29719559f689SAl Viro new_fs->pwd.mnt = mntget(&q->mnt); 2972315fc83eSAl Viro pwdmnt = &p->mnt; 29731da177e4SLinus Torvalds } 29741da177e4SLinus Torvalds } 2975909b0a88SAl Viro p = next_mnt(p, old); 2976909b0a88SAl Viro q = next_mnt(q, new); 29774ce5d2b1SEric W. Biederman if (!q) 29784ce5d2b1SEric W. Biederman break; 29794ce5d2b1SEric W. Biederman while (p->mnt.mnt_root != q->mnt.mnt_root) 29804ce5d2b1SEric W. Biederman p = next_mnt(p, old); 29811da177e4SLinus Torvalds } 2982328e6d90SAl Viro namespace_unlock(); 29831da177e4SLinus Torvalds 29841da177e4SLinus Torvalds if (rootmnt) 2985f03c6599SAl Viro mntput(rootmnt); 29861da177e4SLinus Torvalds if (pwdmnt) 2987f03c6599SAl Viro mntput(pwdmnt); 29881da177e4SLinus Torvalds 2989741a2951SJANAK DESAI return new_ns; 2990741a2951SJANAK DESAI } 2991741a2951SJANAK DESAI 2992cf8d2c11STrond Myklebust /** 2993cf8d2c11STrond Myklebust * create_mnt_ns - creates a private namespace and adds a root filesystem 2994cf8d2c11STrond Myklebust * @mnt: pointer to the new root filesystem mountpoint 2995cf8d2c11STrond Myklebust */ 29961a4eeaf2SAl Viro static struct mnt_namespace *create_mnt_ns(struct vfsmount *m) 2997cf8d2c11STrond Myklebust { 2998771b1371SEric W. Biederman struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns); 2999cf8d2c11STrond Myklebust if (!IS_ERR(new_ns)) { 30001a4eeaf2SAl Viro struct mount *mnt = real_mount(m); 30011a4eeaf2SAl Viro mnt->mnt_ns = new_ns; 3002be08d6d2SAl Viro new_ns->root = mnt; 3003d2921684SEric W. Biederman new_ns->mounts++; 3004b1983cd8SAl Viro list_add(&mnt->mnt_list, &new_ns->list); 3005c1334495SAl Viro } else { 30061a4eeaf2SAl Viro mntput(m); 3007cf8d2c11STrond Myklebust } 3008cf8d2c11STrond Myklebust return new_ns; 3009cf8d2c11STrond Myklebust } 3010cf8d2c11STrond Myklebust 3011ea441d11SAl Viro struct dentry *mount_subtree(struct vfsmount *mnt, const char *name) 3012ea441d11SAl Viro { 3013ea441d11SAl Viro struct mnt_namespace *ns; 3014d31da0f0SAl Viro struct super_block *s; 3015ea441d11SAl Viro struct path path; 3016ea441d11SAl Viro int err; 3017ea441d11SAl Viro 3018ea441d11SAl Viro ns = create_mnt_ns(mnt); 3019ea441d11SAl Viro if (IS_ERR(ns)) 3020ea441d11SAl Viro return ERR_CAST(ns); 3021ea441d11SAl Viro 3022ea441d11SAl Viro err = vfs_path_lookup(mnt->mnt_root, mnt, 3023ea441d11SAl Viro name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); 3024ea441d11SAl Viro 3025ea441d11SAl Viro put_mnt_ns(ns); 3026ea441d11SAl Viro 3027ea441d11SAl Viro if (err) 3028ea441d11SAl Viro return ERR_PTR(err); 3029ea441d11SAl Viro 3030ea441d11SAl Viro /* trade a vfsmount reference for active sb one */ 3031d31da0f0SAl Viro s = path.mnt->mnt_sb; 3032d31da0f0SAl Viro atomic_inc(&s->s_active); 3033ea441d11SAl Viro mntput(path.mnt); 3034ea441d11SAl Viro /* lock the sucker */ 3035d31da0f0SAl Viro down_write(&s->s_umount); 3036ea441d11SAl Viro /* ... and return the root of (sub)tree on it */ 3037ea441d11SAl Viro return path.dentry; 3038ea441d11SAl Viro } 3039ea441d11SAl Viro EXPORT_SYMBOL(mount_subtree); 3040ea441d11SAl Viro 3041312db1aaSDominik Brodowski int ksys_mount(char __user *dev_name, char __user *dir_name, char __user *type, 3042312db1aaSDominik Brodowski unsigned long flags, void __user *data) 30431da177e4SLinus Torvalds { 3044eca6f534SVegard Nossum int ret; 3045eca6f534SVegard Nossum char *kernel_type; 3046eca6f534SVegard Nossum char *kernel_dev; 3047b40ef869SAl Viro void *options; 30481da177e4SLinus Torvalds 3049b8850d1fSTim Gardner kernel_type = copy_mount_string(type); 3050b8850d1fSTim Gardner ret = PTR_ERR(kernel_type); 3051b8850d1fSTim Gardner if (IS_ERR(kernel_type)) 3052eca6f534SVegard Nossum goto out_type; 30531da177e4SLinus Torvalds 3054b8850d1fSTim Gardner kernel_dev = copy_mount_string(dev_name); 3055b8850d1fSTim Gardner ret = PTR_ERR(kernel_dev); 3056b8850d1fSTim Gardner if (IS_ERR(kernel_dev)) 3057eca6f534SVegard Nossum goto out_dev; 30581da177e4SLinus Torvalds 3059b40ef869SAl Viro options = copy_mount_options(data); 3060b40ef869SAl Viro ret = PTR_ERR(options); 3061b40ef869SAl Viro if (IS_ERR(options)) 3062eca6f534SVegard Nossum goto out_data; 30631da177e4SLinus Torvalds 3064b40ef869SAl Viro ret = do_mount(kernel_dev, dir_name, kernel_type, flags, options); 3065eca6f534SVegard Nossum 3066b40ef869SAl Viro kfree(options); 3067eca6f534SVegard Nossum out_data: 3068eca6f534SVegard Nossum kfree(kernel_dev); 3069eca6f534SVegard Nossum out_dev: 3070eca6f534SVegard Nossum kfree(kernel_type); 3071eca6f534SVegard Nossum out_type: 3072eca6f534SVegard Nossum return ret; 30731da177e4SLinus Torvalds } 30741da177e4SLinus Torvalds 3075312db1aaSDominik Brodowski SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, 3076312db1aaSDominik Brodowski char __user *, type, unsigned long, flags, void __user *, data) 3077312db1aaSDominik Brodowski { 3078312db1aaSDominik Brodowski return ksys_mount(dev_name, dir_name, type, flags, data); 3079312db1aaSDominik Brodowski } 3080312db1aaSDominik Brodowski 30811da177e4SLinus Torvalds /* 3082afac7cbaSAl Viro * Return true if path is reachable from root 3083afac7cbaSAl Viro * 308448a066e7SAl Viro * namespace_sem or mount_lock is held 3085afac7cbaSAl Viro */ 3086643822b4SAl Viro bool is_path_reachable(struct mount *mnt, struct dentry *dentry, 3087afac7cbaSAl Viro const struct path *root) 3088afac7cbaSAl Viro { 3089643822b4SAl Viro while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) { 3090a73324daSAl Viro dentry = mnt->mnt_mountpoint; 30910714a533SAl Viro mnt = mnt->mnt_parent; 3092afac7cbaSAl Viro } 3093643822b4SAl Viro return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry); 3094afac7cbaSAl Viro } 3095afac7cbaSAl Viro 3096640eb7e7SMickaël Salaün bool path_is_under(const struct path *path1, const struct path *path2) 3097afac7cbaSAl Viro { 309825ab4c9bSYaowei Bai bool res; 309948a066e7SAl Viro read_seqlock_excl(&mount_lock); 3100643822b4SAl Viro res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2); 310148a066e7SAl Viro read_sequnlock_excl(&mount_lock); 3102afac7cbaSAl Viro return res; 3103afac7cbaSAl Viro } 3104afac7cbaSAl Viro EXPORT_SYMBOL(path_is_under); 3105afac7cbaSAl Viro 3106afac7cbaSAl Viro /* 31071da177e4SLinus Torvalds * pivot_root Semantics: 31081da177e4SLinus Torvalds * Moves the root file system of the current process to the directory put_old, 31091da177e4SLinus Torvalds * makes new_root as the new root file system of the current process, and sets 31101da177e4SLinus Torvalds * root/cwd of all processes which had them on the current root to new_root. 31111da177e4SLinus Torvalds * 31121da177e4SLinus Torvalds * Restrictions: 31131da177e4SLinus Torvalds * The new_root and put_old must be directories, and must not be on the 31141da177e4SLinus Torvalds * same file system as the current process root. The put_old must be 31151da177e4SLinus Torvalds * underneath new_root, i.e. adding a non-zero number of /.. to the string 31161da177e4SLinus Torvalds * pointed to by put_old must yield the same directory as new_root. No other 31171da177e4SLinus Torvalds * file system may be mounted on put_old. After all, new_root is a mountpoint. 31181da177e4SLinus Torvalds * 31194a0d11faSNeil Brown * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. 31204a0d11faSNeil Brown * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives 31214a0d11faSNeil Brown * in this situation. 31224a0d11faSNeil Brown * 31231da177e4SLinus Torvalds * Notes: 31241da177e4SLinus Torvalds * - we don't move root/cwd if they are not at the root (reason: if something 31251da177e4SLinus Torvalds * cared enough to change them, it's probably wrong to force them elsewhere) 31261da177e4SLinus Torvalds * - it's okay to pick a root that isn't the root of a file system, e.g. 31271da177e4SLinus Torvalds * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, 31281da177e4SLinus Torvalds * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root 31291da177e4SLinus Torvalds * first. 31301da177e4SLinus Torvalds */ 31313480b257SHeiko Carstens SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, 31323480b257SHeiko Carstens const char __user *, put_old) 31331da177e4SLinus Torvalds { 31342d8f3038SAl Viro struct path new, old, parent_path, root_parent, root; 313584d17192SAl Viro struct mount *new_mnt, *root_mnt, *old_mnt; 313684d17192SAl Viro struct mountpoint *old_mp, *root_mp; 31371da177e4SLinus Torvalds int error; 31381da177e4SLinus Torvalds 31399b40bc90SAl Viro if (!may_mount()) 31401da177e4SLinus Torvalds return -EPERM; 31411da177e4SLinus Torvalds 31422d8f3038SAl Viro error = user_path_dir(new_root, &new); 31431da177e4SLinus Torvalds if (error) 31441da177e4SLinus Torvalds goto out0; 31451da177e4SLinus Torvalds 31462d8f3038SAl Viro error = user_path_dir(put_old, &old); 31471da177e4SLinus Torvalds if (error) 31481da177e4SLinus Torvalds goto out1; 31491da177e4SLinus Torvalds 31502d8f3038SAl Viro error = security_sb_pivotroot(&old, &new); 3151b12cea91SAl Viro if (error) 3152b12cea91SAl Viro goto out2; 31531da177e4SLinus Torvalds 3154f7ad3c6bSMiklos Szeredi get_fs_root(current->fs, &root); 315584d17192SAl Viro old_mp = lock_mount(&old); 315684d17192SAl Viro error = PTR_ERR(old_mp); 315784d17192SAl Viro if (IS_ERR(old_mp)) 3158b12cea91SAl Viro goto out3; 3159b12cea91SAl Viro 31601da177e4SLinus Torvalds error = -EINVAL; 3161419148daSAl Viro new_mnt = real_mount(new.mnt); 3162419148daSAl Viro root_mnt = real_mount(root.mnt); 316384d17192SAl Viro old_mnt = real_mount(old.mnt); 316484d17192SAl Viro if (IS_MNT_SHARED(old_mnt) || 3165fc7be130SAl Viro IS_MNT_SHARED(new_mnt->mnt_parent) || 3166fc7be130SAl Viro IS_MNT_SHARED(root_mnt->mnt_parent)) 3167b12cea91SAl Viro goto out4; 3168143c8c91SAl Viro if (!check_mnt(root_mnt) || !check_mnt(new_mnt)) 3169b12cea91SAl Viro goto out4; 31705ff9d8a6SEric W. Biederman if (new_mnt->mnt.mnt_flags & MNT_LOCKED) 31715ff9d8a6SEric W. Biederman goto out4; 31721da177e4SLinus Torvalds error = -ENOENT; 3173f3da392eSAlexey Dobriyan if (d_unlinked(new.dentry)) 3174b12cea91SAl Viro goto out4; 31751da177e4SLinus Torvalds error = -EBUSY; 317684d17192SAl Viro if (new_mnt == root_mnt || old_mnt == root_mnt) 3177b12cea91SAl Viro goto out4; /* loop, on the same file system */ 31781da177e4SLinus Torvalds error = -EINVAL; 31798c3ee42eSAl Viro if (root.mnt->mnt_root != root.dentry) 3180b12cea91SAl Viro goto out4; /* not a mountpoint */ 3181676da58dSAl Viro if (!mnt_has_parent(root_mnt)) 3182b12cea91SAl Viro goto out4; /* not attached */ 318384d17192SAl Viro root_mp = root_mnt->mnt_mp; 31842d8f3038SAl Viro if (new.mnt->mnt_root != new.dentry) 3185b12cea91SAl Viro goto out4; /* not a mountpoint */ 3186676da58dSAl Viro if (!mnt_has_parent(new_mnt)) 3187b12cea91SAl Viro goto out4; /* not attached */ 31884ac91378SJan Blunck /* make sure we can reach put_old from new_root */ 318984d17192SAl Viro if (!is_path_reachable(old_mnt, old.dentry, &new)) 3190b12cea91SAl Viro goto out4; 31910d082601SEric W. Biederman /* make certain new is below the root */ 31920d082601SEric W. Biederman if (!is_path_reachable(new_mnt, new.dentry, &root)) 31930d082601SEric W. Biederman goto out4; 319484d17192SAl Viro root_mp->m_count++; /* pin it so it won't go away */ 3195719ea2fbSAl Viro lock_mount_hash(); 3196419148daSAl Viro detach_mnt(new_mnt, &parent_path); 3197419148daSAl Viro detach_mnt(root_mnt, &root_parent); 31985ff9d8a6SEric W. Biederman if (root_mnt->mnt.mnt_flags & MNT_LOCKED) { 31995ff9d8a6SEric W. Biederman new_mnt->mnt.mnt_flags |= MNT_LOCKED; 32005ff9d8a6SEric W. Biederman root_mnt->mnt.mnt_flags &= ~MNT_LOCKED; 32015ff9d8a6SEric W. Biederman } 32024ac91378SJan Blunck /* mount old root on put_old */ 320384d17192SAl Viro attach_mnt(root_mnt, old_mnt, old_mp); 32044ac91378SJan Blunck /* mount new_root on / */ 320584d17192SAl Viro attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp); 32066b3286edSKirill Korotaev touch_mnt_namespace(current->nsproxy->mnt_ns); 32074fed655cSEric W. Biederman /* A moved mount should not expire automatically */ 32084fed655cSEric W. Biederman list_del_init(&new_mnt->mnt_expire); 32093895dbf8SEric W. Biederman put_mountpoint(root_mp); 3210719ea2fbSAl Viro unlock_mount_hash(); 32112d8f3038SAl Viro chroot_fs_refs(&root, &new); 32121da177e4SLinus Torvalds error = 0; 3213b12cea91SAl Viro out4: 321484d17192SAl Viro unlock_mount(old_mp); 3215b12cea91SAl Viro if (!error) { 32161a390689SAl Viro path_put(&root_parent); 32171a390689SAl Viro path_put(&parent_path); 3218b12cea91SAl Viro } 3219b12cea91SAl Viro out3: 32208c3ee42eSAl Viro path_put(&root); 3221b12cea91SAl Viro out2: 32222d8f3038SAl Viro path_put(&old); 32231da177e4SLinus Torvalds out1: 32242d8f3038SAl Viro path_put(&new); 32251da177e4SLinus Torvalds out0: 32261da177e4SLinus Torvalds return error; 32271da177e4SLinus Torvalds } 32281da177e4SLinus Torvalds 32291da177e4SLinus Torvalds static void __init init_mount_tree(void) 32301da177e4SLinus Torvalds { 32311da177e4SLinus Torvalds struct vfsmount *mnt; 32326b3286edSKirill Korotaev struct mnt_namespace *ns; 3233ac748a09SJan Blunck struct path root; 32340c55cfc4SEric W. Biederman struct file_system_type *type; 32351da177e4SLinus Torvalds 32360c55cfc4SEric W. Biederman type = get_fs_type("rootfs"); 32370c55cfc4SEric W. Biederman if (!type) 32380c55cfc4SEric W. Biederman panic("Can't find rootfs type"); 32390c55cfc4SEric W. Biederman mnt = vfs_kern_mount(type, 0, "rootfs", NULL); 32400c55cfc4SEric W. Biederman put_filesystem(type); 32411da177e4SLinus Torvalds if (IS_ERR(mnt)) 32421da177e4SLinus Torvalds panic("Can't create rootfs"); 3243b3e19d92SNick Piggin 32443b22edc5STrond Myklebust ns = create_mnt_ns(mnt); 32453b22edc5STrond Myklebust if (IS_ERR(ns)) 32461da177e4SLinus Torvalds panic("Can't allocate initial namespace"); 32471da177e4SLinus Torvalds 32486b3286edSKirill Korotaev init_task.nsproxy->mnt_ns = ns; 32496b3286edSKirill Korotaev get_mnt_ns(ns); 32501da177e4SLinus Torvalds 3251be08d6d2SAl Viro root.mnt = mnt; 3252be08d6d2SAl Viro root.dentry = mnt->mnt_root; 3253da362b09SEric W. Biederman mnt->mnt_flags |= MNT_LOCKED; 3254ac748a09SJan Blunck 3255ac748a09SJan Blunck set_fs_pwd(current->fs, &root); 3256ac748a09SJan Blunck set_fs_root(current->fs, &root); 32571da177e4SLinus Torvalds } 32581da177e4SLinus Torvalds 325974bf17cfSDenis Cheng void __init mnt_init(void) 32601da177e4SLinus Torvalds { 326115a67dd8SRandy Dunlap int err; 32621da177e4SLinus Torvalds 32637d6fec45SAl Viro mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount), 326420c2df83SPaul Mundt 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); 32651da177e4SLinus Torvalds 32660818bf27SAl Viro mount_hashtable = alloc_large_system_hash("Mount-cache", 326738129a13SAl Viro sizeof(struct hlist_head), 32680818bf27SAl Viro mhash_entries, 19, 32693d375d78SPavel Tatashin HASH_ZERO, 32700818bf27SAl Viro &m_hash_shift, &m_hash_mask, 0, 0); 32710818bf27SAl Viro mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache", 32720818bf27SAl Viro sizeof(struct hlist_head), 32730818bf27SAl Viro mphash_entries, 19, 32743d375d78SPavel Tatashin HASH_ZERO, 32750818bf27SAl Viro &mp_hash_shift, &mp_hash_mask, 0, 0); 32761da177e4SLinus Torvalds 327784d17192SAl Viro if (!mount_hashtable || !mountpoint_hashtable) 32781da177e4SLinus Torvalds panic("Failed to allocate mount hash table\n"); 32791da177e4SLinus Torvalds 32804b93dc9bSTejun Heo kernfs_init(); 32814b93dc9bSTejun Heo 328215a67dd8SRandy Dunlap err = sysfs_init(); 328315a67dd8SRandy Dunlap if (err) 328415a67dd8SRandy Dunlap printk(KERN_WARNING "%s: sysfs_init error: %d\n", 32858e24eea7SHarvey Harrison __func__, err); 328600d26666SGreg Kroah-Hartman fs_kobj = kobject_create_and_add("fs", NULL); 328700d26666SGreg Kroah-Hartman if (!fs_kobj) 32888e24eea7SHarvey Harrison printk(KERN_WARNING "%s: kobj create error\n", __func__); 32891da177e4SLinus Torvalds init_rootfs(); 32901da177e4SLinus Torvalds init_mount_tree(); 32911da177e4SLinus Torvalds } 32921da177e4SLinus Torvalds 3293616511d0STrond Myklebust void put_mnt_ns(struct mnt_namespace *ns) 32941da177e4SLinus Torvalds { 3295d498b25aSAl Viro if (!atomic_dec_and_test(&ns->count)) 3296616511d0STrond Myklebust return; 32977b00ed6fSAl Viro drop_collected_mounts(&ns->root->mnt); 3298771b1371SEric W. Biederman free_mnt_ns(ns); 32991da177e4SLinus Torvalds } 33009d412a43SAl Viro 33019d412a43SAl Viro struct vfsmount *kern_mount_data(struct file_system_type *type, void *data) 33029d412a43SAl Viro { 3303423e0ab0STim Chen struct vfsmount *mnt; 3304e462ec50SDavid Howells mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, data); 3305423e0ab0STim Chen if (!IS_ERR(mnt)) { 3306423e0ab0STim Chen /* 3307423e0ab0STim Chen * it is a longterm mount, don't release mnt until 3308423e0ab0STim Chen * we unmount before file sys is unregistered 3309423e0ab0STim Chen */ 3310f7a99c5bSAl Viro real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL; 3311423e0ab0STim Chen } 3312423e0ab0STim Chen return mnt; 33139d412a43SAl Viro } 33149d412a43SAl Viro EXPORT_SYMBOL_GPL(kern_mount_data); 3315423e0ab0STim Chen 3316423e0ab0STim Chen void kern_unmount(struct vfsmount *mnt) 3317423e0ab0STim Chen { 3318423e0ab0STim Chen /* release long term mount so mount point can be released */ 3319423e0ab0STim Chen if (!IS_ERR_OR_NULL(mnt)) { 3320f7a99c5bSAl Viro real_mount(mnt)->mnt_ns = NULL; 332148a066e7SAl Viro synchronize_rcu(); /* yecchhh... */ 3322423e0ab0STim Chen mntput(mnt); 3323423e0ab0STim Chen } 3324423e0ab0STim Chen } 3325423e0ab0STim Chen EXPORT_SYMBOL(kern_unmount); 332602125a82SAl Viro 332702125a82SAl Viro bool our_mnt(struct vfsmount *mnt) 332802125a82SAl Viro { 3329143c8c91SAl Viro return check_mnt(real_mount(mnt)); 333002125a82SAl Viro } 33318823c079SEric W. Biederman 33323151527eSEric W. Biederman bool current_chrooted(void) 33333151527eSEric W. Biederman { 33343151527eSEric W. Biederman /* Does the current process have a non-standard root */ 33353151527eSEric W. Biederman struct path ns_root; 33363151527eSEric W. Biederman struct path fs_root; 33373151527eSEric W. Biederman bool chrooted; 33383151527eSEric W. Biederman 33393151527eSEric W. Biederman /* Find the namespace root */ 33403151527eSEric W. Biederman ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt; 33413151527eSEric W. Biederman ns_root.dentry = ns_root.mnt->mnt_root; 33423151527eSEric W. Biederman path_get(&ns_root); 33433151527eSEric W. Biederman while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root)) 33443151527eSEric W. Biederman ; 33453151527eSEric W. Biederman 33463151527eSEric W. Biederman get_fs_root(current->fs, &fs_root); 33473151527eSEric W. Biederman 33483151527eSEric W. Biederman chrooted = !path_equal(&fs_root, &ns_root); 33493151527eSEric W. Biederman 33503151527eSEric W. Biederman path_put(&fs_root); 33513151527eSEric W. Biederman path_put(&ns_root); 33523151527eSEric W. Biederman 33533151527eSEric W. Biederman return chrooted; 33543151527eSEric W. Biederman } 33553151527eSEric W. Biederman 33568654df4eSEric W. Biederman static bool mnt_already_visible(struct mnt_namespace *ns, struct vfsmount *new, 33578654df4eSEric W. Biederman int *new_mnt_flags) 335887a8ebd6SEric W. Biederman { 33598c6cf9ccSEric W. Biederman int new_flags = *new_mnt_flags; 336087a8ebd6SEric W. Biederman struct mount *mnt; 3361e51db735SEric W. Biederman bool visible = false; 336287a8ebd6SEric W. Biederman 336344bb4385SAl Viro down_read(&namespace_sem); 336487a8ebd6SEric W. Biederman list_for_each_entry(mnt, &ns->list, mnt_list) { 3365e51db735SEric W. Biederman struct mount *child; 336677b1a97dSEric W. Biederman int mnt_flags; 336777b1a97dSEric W. Biederman 33688654df4eSEric W. Biederman if (mnt->mnt.mnt_sb->s_type != new->mnt_sb->s_type) 3369e51db735SEric W. Biederman continue; 3370e51db735SEric W. Biederman 33717e96c1b0SEric W. Biederman /* This mount is not fully visible if it's root directory 33727e96c1b0SEric W. Biederman * is not the root directory of the filesystem. 33737e96c1b0SEric W. Biederman */ 33747e96c1b0SEric W. Biederman if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root) 33757e96c1b0SEric W. Biederman continue; 33767e96c1b0SEric W. Biederman 3377a1935c17SEric W. Biederman /* A local view of the mount flags */ 337877b1a97dSEric W. Biederman mnt_flags = mnt->mnt.mnt_flags; 337977b1a97dSEric W. Biederman 3380695e9df0SEric W. Biederman /* Don't miss readonly hidden in the superblock flags */ 3381bc98a42cSDavid Howells if (sb_rdonly(mnt->mnt.mnt_sb)) 3382695e9df0SEric W. Biederman mnt_flags |= MNT_LOCK_READONLY; 3383695e9df0SEric W. Biederman 33848c6cf9ccSEric W. Biederman /* Verify the mount flags are equal to or more permissive 33858c6cf9ccSEric W. Biederman * than the proposed new mount. 33868c6cf9ccSEric W. Biederman */ 338777b1a97dSEric W. Biederman if ((mnt_flags & MNT_LOCK_READONLY) && 33888c6cf9ccSEric W. Biederman !(new_flags & MNT_READONLY)) 33898c6cf9ccSEric W. Biederman continue; 339077b1a97dSEric W. Biederman if ((mnt_flags & MNT_LOCK_ATIME) && 339177b1a97dSEric W. Biederman ((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK))) 33928c6cf9ccSEric W. Biederman continue; 33938c6cf9ccSEric W. Biederman 3394ceeb0e5dSEric W. Biederman /* This mount is not fully visible if there are any 3395ceeb0e5dSEric W. Biederman * locked child mounts that cover anything except for 3396ceeb0e5dSEric W. Biederman * empty directories. 3397e51db735SEric W. Biederman */ 3398e51db735SEric W. Biederman list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { 3399e51db735SEric W. Biederman struct inode *inode = child->mnt_mountpoint->d_inode; 3400ceeb0e5dSEric W. Biederman /* Only worry about locked mounts */ 3401d71ed6c9SEric W. Biederman if (!(child->mnt.mnt_flags & MNT_LOCKED)) 3402ceeb0e5dSEric W. Biederman continue; 34037236c85eSEric W. Biederman /* Is the directory permanetly empty? */ 34047236c85eSEric W. Biederman if (!is_empty_dir_inode(inode)) 3405e51db735SEric W. Biederman goto next; 340687a8ebd6SEric W. Biederman } 34078c6cf9ccSEric W. Biederman /* Preserve the locked attributes */ 340877b1a97dSEric W. Biederman *new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \ 34098c6cf9ccSEric W. Biederman MNT_LOCK_ATIME); 3410e51db735SEric W. Biederman visible = true; 3411e51db735SEric W. Biederman goto found; 3412e51db735SEric W. Biederman next: ; 341387a8ebd6SEric W. Biederman } 3414e51db735SEric W. Biederman found: 341544bb4385SAl Viro up_read(&namespace_sem); 3416e51db735SEric W. Biederman return visible; 341787a8ebd6SEric W. Biederman } 341887a8ebd6SEric W. Biederman 34198654df4eSEric W. Biederman static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags) 34208654df4eSEric W. Biederman { 3421a1935c17SEric W. Biederman const unsigned long required_iflags = SB_I_NOEXEC | SB_I_NODEV; 34228654df4eSEric W. Biederman struct mnt_namespace *ns = current->nsproxy->mnt_ns; 34238654df4eSEric W. Biederman unsigned long s_iflags; 34248654df4eSEric W. Biederman 34258654df4eSEric W. Biederman if (ns->user_ns == &init_user_ns) 34268654df4eSEric W. Biederman return false; 34278654df4eSEric W. Biederman 34288654df4eSEric W. Biederman /* Can this filesystem be too revealing? */ 34298654df4eSEric W. Biederman s_iflags = mnt->mnt_sb->s_iflags; 34308654df4eSEric W. Biederman if (!(s_iflags & SB_I_USERNS_VISIBLE)) 34318654df4eSEric W. Biederman return false; 34328654df4eSEric W. Biederman 3433a1935c17SEric W. Biederman if ((s_iflags & required_iflags) != required_iflags) { 3434a1935c17SEric W. Biederman WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n", 3435a1935c17SEric W. Biederman required_iflags); 3436a1935c17SEric W. Biederman return true; 3437a1935c17SEric W. Biederman } 3438a1935c17SEric W. Biederman 34398654df4eSEric W. Biederman return !mnt_already_visible(ns, mnt, new_mnt_flags); 34408654df4eSEric W. Biederman } 34418654df4eSEric W. Biederman 3442380cf5baSAndy Lutomirski bool mnt_may_suid(struct vfsmount *mnt) 3443380cf5baSAndy Lutomirski { 3444380cf5baSAndy Lutomirski /* 3445380cf5baSAndy Lutomirski * Foreign mounts (accessed via fchdir or through /proc 3446380cf5baSAndy Lutomirski * symlinks) are always treated as if they are nosuid. This 3447380cf5baSAndy Lutomirski * prevents namespaces from trusting potentially unsafe 3448380cf5baSAndy Lutomirski * suid/sgid bits, file caps, or security labels that originate 3449380cf5baSAndy Lutomirski * in other namespaces. 3450380cf5baSAndy Lutomirski */ 3451380cf5baSAndy Lutomirski return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) && 3452380cf5baSAndy Lutomirski current_in_userns(mnt->mnt_sb->s_user_ns); 3453380cf5baSAndy Lutomirski } 3454380cf5baSAndy Lutomirski 345564964528SAl Viro static struct ns_common *mntns_get(struct task_struct *task) 34568823c079SEric W. Biederman { 345758be2825SAl Viro struct ns_common *ns = NULL; 34588823c079SEric W. Biederman struct nsproxy *nsproxy; 34598823c079SEric W. Biederman 3460728dba3aSEric W. Biederman task_lock(task); 3461728dba3aSEric W. Biederman nsproxy = task->nsproxy; 34628823c079SEric W. Biederman if (nsproxy) { 346358be2825SAl Viro ns = &nsproxy->mnt_ns->ns; 346458be2825SAl Viro get_mnt_ns(to_mnt_ns(ns)); 34658823c079SEric W. Biederman } 3466728dba3aSEric W. Biederman task_unlock(task); 34678823c079SEric W. Biederman 34688823c079SEric W. Biederman return ns; 34698823c079SEric W. Biederman } 34708823c079SEric W. Biederman 347164964528SAl Viro static void mntns_put(struct ns_common *ns) 34728823c079SEric W. Biederman { 347358be2825SAl Viro put_mnt_ns(to_mnt_ns(ns)); 34748823c079SEric W. Biederman } 34758823c079SEric W. Biederman 347664964528SAl Viro static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns) 34778823c079SEric W. Biederman { 34788823c079SEric W. Biederman struct fs_struct *fs = current->fs; 34794f757f3cSAl Viro struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns; 34808823c079SEric W. Biederman struct path root; 34814f757f3cSAl Viro int err; 34828823c079SEric W. Biederman 34830c55cfc4SEric W. Biederman if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) || 3484c7b96acfSEric W. Biederman !ns_capable(current_user_ns(), CAP_SYS_CHROOT) || 3485c7b96acfSEric W. Biederman !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) 3486ae11e0f1SZhao Hongjiang return -EPERM; 34878823c079SEric W. Biederman 34888823c079SEric W. Biederman if (fs->users != 1) 34898823c079SEric W. Biederman return -EINVAL; 34908823c079SEric W. Biederman 34918823c079SEric W. Biederman get_mnt_ns(mnt_ns); 34924f757f3cSAl Viro old_mnt_ns = nsproxy->mnt_ns; 34938823c079SEric W. Biederman nsproxy->mnt_ns = mnt_ns; 34948823c079SEric W. Biederman 34958823c079SEric W. Biederman /* Find the root */ 34964f757f3cSAl Viro err = vfs_path_lookup(mnt_ns->root->mnt.mnt_root, &mnt_ns->root->mnt, 34974f757f3cSAl Viro "/", LOOKUP_DOWN, &root); 34984f757f3cSAl Viro if (err) { 34994f757f3cSAl Viro /* revert to old namespace */ 35004f757f3cSAl Viro nsproxy->mnt_ns = old_mnt_ns; 35014f757f3cSAl Viro put_mnt_ns(mnt_ns); 35024f757f3cSAl Viro return err; 35034f757f3cSAl Viro } 35048823c079SEric W. Biederman 35054068367cSAndrei Vagin put_mnt_ns(old_mnt_ns); 35064068367cSAndrei Vagin 35078823c079SEric W. Biederman /* Update the pwd and root */ 35088823c079SEric W. Biederman set_fs_pwd(fs, &root); 35098823c079SEric W. Biederman set_fs_root(fs, &root); 35108823c079SEric W. Biederman 35118823c079SEric W. Biederman path_put(&root); 35128823c079SEric W. Biederman return 0; 35138823c079SEric W. Biederman } 35148823c079SEric W. Biederman 3515bcac25a5SAndrey Vagin static struct user_namespace *mntns_owner(struct ns_common *ns) 3516bcac25a5SAndrey Vagin { 3517bcac25a5SAndrey Vagin return to_mnt_ns(ns)->user_ns; 3518bcac25a5SAndrey Vagin } 3519bcac25a5SAndrey Vagin 35208823c079SEric W. Biederman const struct proc_ns_operations mntns_operations = { 35218823c079SEric W. Biederman .name = "mnt", 35228823c079SEric W. Biederman .type = CLONE_NEWNS, 35238823c079SEric W. Biederman .get = mntns_get, 35248823c079SEric W. Biederman .put = mntns_put, 35258823c079SEric W. Biederman .install = mntns_install, 3526bcac25a5SAndrey Vagin .owner = mntns_owner, 35278823c079SEric W. Biederman }; 3528