1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * linux/fs/namespace.c 4 * 5 * (C) Copyright Al Viro 2000, 2001 6 * 7 * Based on code from fs/super.c, copyright Linus Torvalds and others. 8 * Heavily rewritten. 9 */ 10 11 #include <linux/syscalls.h> 12 #include <linux/export.h> 13 #include <linux/capability.h> 14 #include <linux/mnt_namespace.h> 15 #include <linux/user_namespace.h> 16 #include <linux/namei.h> 17 #include <linux/security.h> 18 #include <linux/cred.h> 19 #include <linux/idr.h> 20 #include <linux/init.h> /* init_rootfs */ 21 #include <linux/fs_struct.h> /* get_fs_root et.al. */ 22 #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */ 23 #include <linux/file.h> 24 #include <linux/uaccess.h> 25 #include <linux/proc_ns.h> 26 #include <linux/magic.h> 27 #include <linux/memblock.h> 28 #include <linux/proc_fs.h> 29 #include <linux/task_work.h> 30 #include <linux/sched/task.h> 31 #include <uapi/linux/mount.h> 32 #include <linux/fs_context.h> 33 #include <linux/shmem_fs.h> 34 35 #include "pnode.h" 36 #include "internal.h" 37 38 /* Maximum number of mounts in a mount namespace */ 39 unsigned int sysctl_mount_max __read_mostly = 100000; 40 41 static unsigned int m_hash_mask __read_mostly; 42 static unsigned int m_hash_shift __read_mostly; 43 static unsigned int mp_hash_mask __read_mostly; 44 static unsigned int mp_hash_shift __read_mostly; 45 46 static __initdata unsigned long mhash_entries; 47 static int __init set_mhash_entries(char *str) 48 { 49 if (!str) 50 return 0; 51 mhash_entries = simple_strtoul(str, &str, 0); 52 return 1; 53 } 54 __setup("mhash_entries=", set_mhash_entries); 55 56 static __initdata unsigned long mphash_entries; 57 static int __init set_mphash_entries(char *str) 58 { 59 if (!str) 60 return 0; 61 mphash_entries = simple_strtoul(str, &str, 0); 62 return 1; 63 } 64 __setup("mphash_entries=", set_mphash_entries); 65 66 static u64 event; 67 static DEFINE_IDA(mnt_id_ida); 68 static DEFINE_IDA(mnt_group_ida); 69 70 static struct hlist_head *mount_hashtable __read_mostly; 71 static struct hlist_head *mountpoint_hashtable __read_mostly; 72 static struct kmem_cache *mnt_cache __read_mostly; 73 static DECLARE_RWSEM(namespace_sem); 74 static HLIST_HEAD(unmounted); /* protected by namespace_sem */ 75 static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */ 76 77 struct mount_kattr { 78 unsigned int attr_set; 79 unsigned int attr_clr; 80 unsigned int propagation; 81 unsigned int lookup_flags; 82 bool recurse; 83 struct user_namespace *mnt_userns; 84 }; 85 86 /* /sys/fs */ 87 struct kobject *fs_kobj; 88 EXPORT_SYMBOL_GPL(fs_kobj); 89 90 /* 91 * vfsmount lock may be taken for read to prevent changes to the 92 * vfsmount hash, ie. during mountpoint lookups or walking back 93 * up the tree. 94 * 95 * It should be taken for write in all cases where the vfsmount 96 * tree or hash is modified or when a vfsmount structure is modified. 97 */ 98 __cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock); 99 100 static inline void lock_mount_hash(void) 101 { 102 write_seqlock(&mount_lock); 103 } 104 105 static inline void unlock_mount_hash(void) 106 { 107 write_sequnlock(&mount_lock); 108 } 109 110 static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry) 111 { 112 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); 113 tmp += ((unsigned long)dentry / L1_CACHE_BYTES); 114 tmp = tmp + (tmp >> m_hash_shift); 115 return &mount_hashtable[tmp & m_hash_mask]; 116 } 117 118 static inline struct hlist_head *mp_hash(struct dentry *dentry) 119 { 120 unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES); 121 tmp = tmp + (tmp >> mp_hash_shift); 122 return &mountpoint_hashtable[tmp & mp_hash_mask]; 123 } 124 125 static int mnt_alloc_id(struct mount *mnt) 126 { 127 int res = ida_alloc(&mnt_id_ida, GFP_KERNEL); 128 129 if (res < 0) 130 return res; 131 mnt->mnt_id = res; 132 return 0; 133 } 134 135 static void mnt_free_id(struct mount *mnt) 136 { 137 ida_free(&mnt_id_ida, mnt->mnt_id); 138 } 139 140 /* 141 * Allocate a new peer group ID 142 */ 143 static int mnt_alloc_group_id(struct mount *mnt) 144 { 145 int res = ida_alloc_min(&mnt_group_ida, 1, GFP_KERNEL); 146 147 if (res < 0) 148 return res; 149 mnt->mnt_group_id = res; 150 return 0; 151 } 152 153 /* 154 * Release a peer group ID 155 */ 156 void mnt_release_group_id(struct mount *mnt) 157 { 158 ida_free(&mnt_group_ida, mnt->mnt_group_id); 159 mnt->mnt_group_id = 0; 160 } 161 162 /* 163 * vfsmount lock must be held for read 164 */ 165 static inline void mnt_add_count(struct mount *mnt, int n) 166 { 167 #ifdef CONFIG_SMP 168 this_cpu_add(mnt->mnt_pcp->mnt_count, n); 169 #else 170 preempt_disable(); 171 mnt->mnt_count += n; 172 preempt_enable(); 173 #endif 174 } 175 176 /* 177 * vfsmount lock must be held for write 178 */ 179 int mnt_get_count(struct mount *mnt) 180 { 181 #ifdef CONFIG_SMP 182 int count = 0; 183 int cpu; 184 185 for_each_possible_cpu(cpu) { 186 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count; 187 } 188 189 return count; 190 #else 191 return mnt->mnt_count; 192 #endif 193 } 194 195 static struct mount *alloc_vfsmnt(const char *name) 196 { 197 struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); 198 if (mnt) { 199 int err; 200 201 err = mnt_alloc_id(mnt); 202 if (err) 203 goto out_free_cache; 204 205 if (name) { 206 mnt->mnt_devname = kstrdup_const(name, GFP_KERNEL); 207 if (!mnt->mnt_devname) 208 goto out_free_id; 209 } 210 211 #ifdef CONFIG_SMP 212 mnt->mnt_pcp = alloc_percpu(struct mnt_pcp); 213 if (!mnt->mnt_pcp) 214 goto out_free_devname; 215 216 this_cpu_add(mnt->mnt_pcp->mnt_count, 1); 217 #else 218 mnt->mnt_count = 1; 219 mnt->mnt_writers = 0; 220 #endif 221 222 INIT_HLIST_NODE(&mnt->mnt_hash); 223 INIT_LIST_HEAD(&mnt->mnt_child); 224 INIT_LIST_HEAD(&mnt->mnt_mounts); 225 INIT_LIST_HEAD(&mnt->mnt_list); 226 INIT_LIST_HEAD(&mnt->mnt_expire); 227 INIT_LIST_HEAD(&mnt->mnt_share); 228 INIT_LIST_HEAD(&mnt->mnt_slave_list); 229 INIT_LIST_HEAD(&mnt->mnt_slave); 230 INIT_HLIST_NODE(&mnt->mnt_mp_list); 231 INIT_LIST_HEAD(&mnt->mnt_umounting); 232 INIT_HLIST_HEAD(&mnt->mnt_stuck_children); 233 mnt->mnt.mnt_userns = &init_user_ns; 234 } 235 return mnt; 236 237 #ifdef CONFIG_SMP 238 out_free_devname: 239 kfree_const(mnt->mnt_devname); 240 #endif 241 out_free_id: 242 mnt_free_id(mnt); 243 out_free_cache: 244 kmem_cache_free(mnt_cache, mnt); 245 return NULL; 246 } 247 248 /* 249 * Most r/o checks on a fs are for operations that take 250 * discrete amounts of time, like a write() or unlink(). 251 * We must keep track of when those operations start 252 * (for permission checks) and when they end, so that 253 * we can determine when writes are able to occur to 254 * a filesystem. 255 */ 256 /* 257 * __mnt_is_readonly: check whether a mount is read-only 258 * @mnt: the mount to check for its write status 259 * 260 * This shouldn't be used directly ouside of the VFS. 261 * It does not guarantee that the filesystem will stay 262 * r/w, just that it is right *now*. This can not and 263 * should not be used in place of IS_RDONLY(inode). 264 * mnt_want/drop_write() will _keep_ the filesystem 265 * r/w. 266 */ 267 bool __mnt_is_readonly(struct vfsmount *mnt) 268 { 269 return (mnt->mnt_flags & MNT_READONLY) || sb_rdonly(mnt->mnt_sb); 270 } 271 EXPORT_SYMBOL_GPL(__mnt_is_readonly); 272 273 static inline void mnt_inc_writers(struct mount *mnt) 274 { 275 #ifdef CONFIG_SMP 276 this_cpu_inc(mnt->mnt_pcp->mnt_writers); 277 #else 278 mnt->mnt_writers++; 279 #endif 280 } 281 282 static inline void mnt_dec_writers(struct mount *mnt) 283 { 284 #ifdef CONFIG_SMP 285 this_cpu_dec(mnt->mnt_pcp->mnt_writers); 286 #else 287 mnt->mnt_writers--; 288 #endif 289 } 290 291 static unsigned int mnt_get_writers(struct mount *mnt) 292 { 293 #ifdef CONFIG_SMP 294 unsigned int count = 0; 295 int cpu; 296 297 for_each_possible_cpu(cpu) { 298 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers; 299 } 300 301 return count; 302 #else 303 return mnt->mnt_writers; 304 #endif 305 } 306 307 static int mnt_is_readonly(struct vfsmount *mnt) 308 { 309 if (mnt->mnt_sb->s_readonly_remount) 310 return 1; 311 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */ 312 smp_rmb(); 313 return __mnt_is_readonly(mnt); 314 } 315 316 /* 317 * Most r/o & frozen checks on a fs are for operations that take discrete 318 * amounts of time, like a write() or unlink(). We must keep track of when 319 * those operations start (for permission checks) and when they end, so that we 320 * can determine when writes are able to occur to a filesystem. 321 */ 322 /** 323 * __mnt_want_write - get write access to a mount without freeze protection 324 * @m: the mount on which to take a write 325 * 326 * This tells the low-level filesystem that a write is about to be performed to 327 * it, and makes sure that writes are allowed (mnt it read-write) before 328 * returning success. This operation does not protect against filesystem being 329 * frozen. When the write operation is finished, __mnt_drop_write() must be 330 * called. This is effectively a refcount. 331 */ 332 int __mnt_want_write(struct vfsmount *m) 333 { 334 struct mount *mnt = real_mount(m); 335 int ret = 0; 336 337 preempt_disable(); 338 mnt_inc_writers(mnt); 339 /* 340 * The store to mnt_inc_writers must be visible before we pass 341 * MNT_WRITE_HOLD loop below, so that the slowpath can see our 342 * incremented count after it has set MNT_WRITE_HOLD. 343 */ 344 smp_mb(); 345 while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) 346 cpu_relax(); 347 /* 348 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will 349 * be set to match its requirements. So we must not load that until 350 * MNT_WRITE_HOLD is cleared. 351 */ 352 smp_rmb(); 353 if (mnt_is_readonly(m)) { 354 mnt_dec_writers(mnt); 355 ret = -EROFS; 356 } 357 preempt_enable(); 358 359 return ret; 360 } 361 362 /** 363 * mnt_want_write - get write access to a mount 364 * @m: the mount on which to take a write 365 * 366 * This tells the low-level filesystem that a write is about to be performed to 367 * it, and makes sure that writes are allowed (mount is read-write, filesystem 368 * is not frozen) before returning success. When the write operation is 369 * finished, mnt_drop_write() must be called. This is effectively a refcount. 370 */ 371 int mnt_want_write(struct vfsmount *m) 372 { 373 int ret; 374 375 sb_start_write(m->mnt_sb); 376 ret = __mnt_want_write(m); 377 if (ret) 378 sb_end_write(m->mnt_sb); 379 return ret; 380 } 381 EXPORT_SYMBOL_GPL(mnt_want_write); 382 383 /** 384 * __mnt_want_write_file - get write access to a file's mount 385 * @file: the file who's mount on which to take a write 386 * 387 * This is like __mnt_want_write, but if the file is already open for writing it 388 * skips incrementing mnt_writers (since the open file already has a reference) 389 * and instead only does the check for emergency r/o remounts. This must be 390 * paired with __mnt_drop_write_file. 391 */ 392 int __mnt_want_write_file(struct file *file) 393 { 394 if (file->f_mode & FMODE_WRITER) { 395 /* 396 * Superblock may have become readonly while there are still 397 * writable fd's, e.g. due to a fs error with errors=remount-ro 398 */ 399 if (__mnt_is_readonly(file->f_path.mnt)) 400 return -EROFS; 401 return 0; 402 } 403 return __mnt_want_write(file->f_path.mnt); 404 } 405 406 /** 407 * mnt_want_write_file - get write access to a file's mount 408 * @file: the file who's mount on which to take a write 409 * 410 * This is like mnt_want_write, but if the file is already open for writing it 411 * skips incrementing mnt_writers (since the open file already has a reference) 412 * and instead only does the freeze protection and the check for emergency r/o 413 * remounts. This must be paired with mnt_drop_write_file. 414 */ 415 int mnt_want_write_file(struct file *file) 416 { 417 int ret; 418 419 sb_start_write(file_inode(file)->i_sb); 420 ret = __mnt_want_write_file(file); 421 if (ret) 422 sb_end_write(file_inode(file)->i_sb); 423 return ret; 424 } 425 EXPORT_SYMBOL_GPL(mnt_want_write_file); 426 427 /** 428 * __mnt_drop_write - give up write access to a mount 429 * @mnt: the mount on which to give up write access 430 * 431 * Tells the low-level filesystem that we are done 432 * performing writes to it. Must be matched with 433 * __mnt_want_write() call above. 434 */ 435 void __mnt_drop_write(struct vfsmount *mnt) 436 { 437 preempt_disable(); 438 mnt_dec_writers(real_mount(mnt)); 439 preempt_enable(); 440 } 441 442 /** 443 * mnt_drop_write - give up write access to a mount 444 * @mnt: the mount on which to give up write access 445 * 446 * Tells the low-level filesystem that we are done performing writes to it and 447 * also allows filesystem to be frozen again. Must be matched with 448 * mnt_want_write() call above. 449 */ 450 void mnt_drop_write(struct vfsmount *mnt) 451 { 452 __mnt_drop_write(mnt); 453 sb_end_write(mnt->mnt_sb); 454 } 455 EXPORT_SYMBOL_GPL(mnt_drop_write); 456 457 void __mnt_drop_write_file(struct file *file) 458 { 459 if (!(file->f_mode & FMODE_WRITER)) 460 __mnt_drop_write(file->f_path.mnt); 461 } 462 463 void mnt_drop_write_file(struct file *file) 464 { 465 __mnt_drop_write_file(file); 466 sb_end_write(file_inode(file)->i_sb); 467 } 468 EXPORT_SYMBOL(mnt_drop_write_file); 469 470 static inline int mnt_hold_writers(struct mount *mnt) 471 { 472 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; 473 /* 474 * After storing MNT_WRITE_HOLD, we'll read the counters. This store 475 * should be visible before we do. 476 */ 477 smp_mb(); 478 479 /* 480 * With writers on hold, if this value is zero, then there are 481 * definitely no active writers (although held writers may subsequently 482 * increment the count, they'll have to wait, and decrement it after 483 * seeing MNT_READONLY). 484 * 485 * It is OK to have counter incremented on one CPU and decremented on 486 * another: the sum will add up correctly. The danger would be when we 487 * sum up each counter, if we read a counter before it is incremented, 488 * but then read another CPU's count which it has been subsequently 489 * decremented from -- we would see more decrements than we should. 490 * MNT_WRITE_HOLD protects against this scenario, because 491 * mnt_want_write first increments count, then smp_mb, then spins on 492 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while 493 * we're counting up here. 494 */ 495 if (mnt_get_writers(mnt) > 0) 496 return -EBUSY; 497 498 return 0; 499 } 500 501 static inline void mnt_unhold_writers(struct mount *mnt) 502 { 503 /* 504 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers 505 * that become unheld will see MNT_READONLY. 506 */ 507 smp_wmb(); 508 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; 509 } 510 511 static int mnt_make_readonly(struct mount *mnt) 512 { 513 int ret; 514 515 ret = mnt_hold_writers(mnt); 516 if (!ret) 517 mnt->mnt.mnt_flags |= MNT_READONLY; 518 mnt_unhold_writers(mnt); 519 return ret; 520 } 521 522 int sb_prepare_remount_readonly(struct super_block *sb) 523 { 524 struct mount *mnt; 525 int err = 0; 526 527 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */ 528 if (atomic_long_read(&sb->s_remove_count)) 529 return -EBUSY; 530 531 lock_mount_hash(); 532 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { 533 if (!(mnt->mnt.mnt_flags & MNT_READONLY)) { 534 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; 535 smp_mb(); 536 if (mnt_get_writers(mnt) > 0) { 537 err = -EBUSY; 538 break; 539 } 540 } 541 } 542 if (!err && atomic_long_read(&sb->s_remove_count)) 543 err = -EBUSY; 544 545 if (!err) { 546 sb->s_readonly_remount = 1; 547 smp_wmb(); 548 } 549 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { 550 if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD) 551 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; 552 } 553 unlock_mount_hash(); 554 555 return err; 556 } 557 558 static void free_vfsmnt(struct mount *mnt) 559 { 560 struct user_namespace *mnt_userns; 561 562 mnt_userns = mnt_user_ns(&mnt->mnt); 563 if (mnt_userns != &init_user_ns) 564 put_user_ns(mnt_userns); 565 kfree_const(mnt->mnt_devname); 566 #ifdef CONFIG_SMP 567 free_percpu(mnt->mnt_pcp); 568 #endif 569 kmem_cache_free(mnt_cache, mnt); 570 } 571 572 static void delayed_free_vfsmnt(struct rcu_head *head) 573 { 574 free_vfsmnt(container_of(head, struct mount, mnt_rcu)); 575 } 576 577 /* call under rcu_read_lock */ 578 int __legitimize_mnt(struct vfsmount *bastard, unsigned seq) 579 { 580 struct mount *mnt; 581 if (read_seqretry(&mount_lock, seq)) 582 return 1; 583 if (bastard == NULL) 584 return 0; 585 mnt = real_mount(bastard); 586 mnt_add_count(mnt, 1); 587 smp_mb(); // see mntput_no_expire() 588 if (likely(!read_seqretry(&mount_lock, seq))) 589 return 0; 590 if (bastard->mnt_flags & MNT_SYNC_UMOUNT) { 591 mnt_add_count(mnt, -1); 592 return 1; 593 } 594 lock_mount_hash(); 595 if (unlikely(bastard->mnt_flags & MNT_DOOMED)) { 596 mnt_add_count(mnt, -1); 597 unlock_mount_hash(); 598 return 1; 599 } 600 unlock_mount_hash(); 601 /* caller will mntput() */ 602 return -1; 603 } 604 605 /* call under rcu_read_lock */ 606 bool legitimize_mnt(struct vfsmount *bastard, unsigned seq) 607 { 608 int res = __legitimize_mnt(bastard, seq); 609 if (likely(!res)) 610 return true; 611 if (unlikely(res < 0)) { 612 rcu_read_unlock(); 613 mntput(bastard); 614 rcu_read_lock(); 615 } 616 return false; 617 } 618 619 /* 620 * find the first mount at @dentry on vfsmount @mnt. 621 * call under rcu_read_lock() 622 */ 623 struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry) 624 { 625 struct hlist_head *head = m_hash(mnt, dentry); 626 struct mount *p; 627 628 hlist_for_each_entry_rcu(p, head, mnt_hash) 629 if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) 630 return p; 631 return NULL; 632 } 633 634 /* 635 * lookup_mnt - Return the first child mount mounted at path 636 * 637 * "First" means first mounted chronologically. If you create the 638 * following mounts: 639 * 640 * mount /dev/sda1 /mnt 641 * mount /dev/sda2 /mnt 642 * mount /dev/sda3 /mnt 643 * 644 * Then lookup_mnt() on the base /mnt dentry in the root mount will 645 * return successively the root dentry and vfsmount of /dev/sda1, then 646 * /dev/sda2, then /dev/sda3, then NULL. 647 * 648 * lookup_mnt takes a reference to the found vfsmount. 649 */ 650 struct vfsmount *lookup_mnt(const struct path *path) 651 { 652 struct mount *child_mnt; 653 struct vfsmount *m; 654 unsigned seq; 655 656 rcu_read_lock(); 657 do { 658 seq = read_seqbegin(&mount_lock); 659 child_mnt = __lookup_mnt(path->mnt, path->dentry); 660 m = child_mnt ? &child_mnt->mnt : NULL; 661 } while (!legitimize_mnt(m, seq)); 662 rcu_read_unlock(); 663 return m; 664 } 665 666 static inline void lock_ns_list(struct mnt_namespace *ns) 667 { 668 spin_lock(&ns->ns_lock); 669 } 670 671 static inline void unlock_ns_list(struct mnt_namespace *ns) 672 { 673 spin_unlock(&ns->ns_lock); 674 } 675 676 static inline bool mnt_is_cursor(struct mount *mnt) 677 { 678 return mnt->mnt.mnt_flags & MNT_CURSOR; 679 } 680 681 /* 682 * __is_local_mountpoint - Test to see if dentry is a mountpoint in the 683 * current mount namespace. 684 * 685 * The common case is dentries are not mountpoints at all and that 686 * test is handled inline. For the slow case when we are actually 687 * dealing with a mountpoint of some kind, walk through all of the 688 * mounts in the current mount namespace and test to see if the dentry 689 * is a mountpoint. 690 * 691 * The mount_hashtable is not usable in the context because we 692 * need to identify all mounts that may be in the current mount 693 * namespace not just a mount that happens to have some specified 694 * parent mount. 695 */ 696 bool __is_local_mountpoint(struct dentry *dentry) 697 { 698 struct mnt_namespace *ns = current->nsproxy->mnt_ns; 699 struct mount *mnt; 700 bool is_covered = false; 701 702 down_read(&namespace_sem); 703 lock_ns_list(ns); 704 list_for_each_entry(mnt, &ns->list, mnt_list) { 705 if (mnt_is_cursor(mnt)) 706 continue; 707 is_covered = (mnt->mnt_mountpoint == dentry); 708 if (is_covered) 709 break; 710 } 711 unlock_ns_list(ns); 712 up_read(&namespace_sem); 713 714 return is_covered; 715 } 716 717 static struct mountpoint *lookup_mountpoint(struct dentry *dentry) 718 { 719 struct hlist_head *chain = mp_hash(dentry); 720 struct mountpoint *mp; 721 722 hlist_for_each_entry(mp, chain, m_hash) { 723 if (mp->m_dentry == dentry) { 724 mp->m_count++; 725 return mp; 726 } 727 } 728 return NULL; 729 } 730 731 static struct mountpoint *get_mountpoint(struct dentry *dentry) 732 { 733 struct mountpoint *mp, *new = NULL; 734 int ret; 735 736 if (d_mountpoint(dentry)) { 737 /* might be worth a WARN_ON() */ 738 if (d_unlinked(dentry)) 739 return ERR_PTR(-ENOENT); 740 mountpoint: 741 read_seqlock_excl(&mount_lock); 742 mp = lookup_mountpoint(dentry); 743 read_sequnlock_excl(&mount_lock); 744 if (mp) 745 goto done; 746 } 747 748 if (!new) 749 new = kmalloc(sizeof(struct mountpoint), GFP_KERNEL); 750 if (!new) 751 return ERR_PTR(-ENOMEM); 752 753 754 /* Exactly one processes may set d_mounted */ 755 ret = d_set_mounted(dentry); 756 757 /* Someone else set d_mounted? */ 758 if (ret == -EBUSY) 759 goto mountpoint; 760 761 /* The dentry is not available as a mountpoint? */ 762 mp = ERR_PTR(ret); 763 if (ret) 764 goto done; 765 766 /* Add the new mountpoint to the hash table */ 767 read_seqlock_excl(&mount_lock); 768 new->m_dentry = dget(dentry); 769 new->m_count = 1; 770 hlist_add_head(&new->m_hash, mp_hash(dentry)); 771 INIT_HLIST_HEAD(&new->m_list); 772 read_sequnlock_excl(&mount_lock); 773 774 mp = new; 775 new = NULL; 776 done: 777 kfree(new); 778 return mp; 779 } 780 781 /* 782 * vfsmount lock must be held. Additionally, the caller is responsible 783 * for serializing calls for given disposal list. 784 */ 785 static void __put_mountpoint(struct mountpoint *mp, struct list_head *list) 786 { 787 if (!--mp->m_count) { 788 struct dentry *dentry = mp->m_dentry; 789 BUG_ON(!hlist_empty(&mp->m_list)); 790 spin_lock(&dentry->d_lock); 791 dentry->d_flags &= ~DCACHE_MOUNTED; 792 spin_unlock(&dentry->d_lock); 793 dput_to_list(dentry, list); 794 hlist_del(&mp->m_hash); 795 kfree(mp); 796 } 797 } 798 799 /* called with namespace_lock and vfsmount lock */ 800 static void put_mountpoint(struct mountpoint *mp) 801 { 802 __put_mountpoint(mp, &ex_mountpoints); 803 } 804 805 static inline int check_mnt(struct mount *mnt) 806 { 807 return mnt->mnt_ns == current->nsproxy->mnt_ns; 808 } 809 810 /* 811 * vfsmount lock must be held for write 812 */ 813 static void touch_mnt_namespace(struct mnt_namespace *ns) 814 { 815 if (ns) { 816 ns->event = ++event; 817 wake_up_interruptible(&ns->poll); 818 } 819 } 820 821 /* 822 * vfsmount lock must be held for write 823 */ 824 static void __touch_mnt_namespace(struct mnt_namespace *ns) 825 { 826 if (ns && ns->event != event) { 827 ns->event = event; 828 wake_up_interruptible(&ns->poll); 829 } 830 } 831 832 /* 833 * vfsmount lock must be held for write 834 */ 835 static struct mountpoint *unhash_mnt(struct mount *mnt) 836 { 837 struct mountpoint *mp; 838 mnt->mnt_parent = mnt; 839 mnt->mnt_mountpoint = mnt->mnt.mnt_root; 840 list_del_init(&mnt->mnt_child); 841 hlist_del_init_rcu(&mnt->mnt_hash); 842 hlist_del_init(&mnt->mnt_mp_list); 843 mp = mnt->mnt_mp; 844 mnt->mnt_mp = NULL; 845 return mp; 846 } 847 848 /* 849 * vfsmount lock must be held for write 850 */ 851 static void umount_mnt(struct mount *mnt) 852 { 853 put_mountpoint(unhash_mnt(mnt)); 854 } 855 856 /* 857 * vfsmount lock must be held for write 858 */ 859 void mnt_set_mountpoint(struct mount *mnt, 860 struct mountpoint *mp, 861 struct mount *child_mnt) 862 { 863 mp->m_count++; 864 mnt_add_count(mnt, 1); /* essentially, that's mntget */ 865 child_mnt->mnt_mountpoint = mp->m_dentry; 866 child_mnt->mnt_parent = mnt; 867 child_mnt->mnt_mp = mp; 868 hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list); 869 } 870 871 static void __attach_mnt(struct mount *mnt, struct mount *parent) 872 { 873 hlist_add_head_rcu(&mnt->mnt_hash, 874 m_hash(&parent->mnt, mnt->mnt_mountpoint)); 875 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); 876 } 877 878 /* 879 * vfsmount lock must be held for write 880 */ 881 static void attach_mnt(struct mount *mnt, 882 struct mount *parent, 883 struct mountpoint *mp) 884 { 885 mnt_set_mountpoint(parent, mp, mnt); 886 __attach_mnt(mnt, parent); 887 } 888 889 void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp, struct mount *mnt) 890 { 891 struct mountpoint *old_mp = mnt->mnt_mp; 892 struct mount *old_parent = mnt->mnt_parent; 893 894 list_del_init(&mnt->mnt_child); 895 hlist_del_init(&mnt->mnt_mp_list); 896 hlist_del_init_rcu(&mnt->mnt_hash); 897 898 attach_mnt(mnt, parent, mp); 899 900 put_mountpoint(old_mp); 901 mnt_add_count(old_parent, -1); 902 } 903 904 /* 905 * vfsmount lock must be held for write 906 */ 907 static void commit_tree(struct mount *mnt) 908 { 909 struct mount *parent = mnt->mnt_parent; 910 struct mount *m; 911 LIST_HEAD(head); 912 struct mnt_namespace *n = parent->mnt_ns; 913 914 BUG_ON(parent == mnt); 915 916 list_add_tail(&head, &mnt->mnt_list); 917 list_for_each_entry(m, &head, mnt_list) 918 m->mnt_ns = n; 919 920 list_splice(&head, n->list.prev); 921 922 n->mounts += n->pending_mounts; 923 n->pending_mounts = 0; 924 925 __attach_mnt(mnt, parent); 926 touch_mnt_namespace(n); 927 } 928 929 static struct mount *next_mnt(struct mount *p, struct mount *root) 930 { 931 struct list_head *next = p->mnt_mounts.next; 932 if (next == &p->mnt_mounts) { 933 while (1) { 934 if (p == root) 935 return NULL; 936 next = p->mnt_child.next; 937 if (next != &p->mnt_parent->mnt_mounts) 938 break; 939 p = p->mnt_parent; 940 } 941 } 942 return list_entry(next, struct mount, mnt_child); 943 } 944 945 static struct mount *skip_mnt_tree(struct mount *p) 946 { 947 struct list_head *prev = p->mnt_mounts.prev; 948 while (prev != &p->mnt_mounts) { 949 p = list_entry(prev, struct mount, mnt_child); 950 prev = p->mnt_mounts.prev; 951 } 952 return p; 953 } 954 955 /** 956 * vfs_create_mount - Create a mount for a configured superblock 957 * @fc: The configuration context with the superblock attached 958 * 959 * Create a mount to an already configured superblock. If necessary, the 960 * caller should invoke vfs_get_tree() before calling this. 961 * 962 * Note that this does not attach the mount to anything. 963 */ 964 struct vfsmount *vfs_create_mount(struct fs_context *fc) 965 { 966 struct mount *mnt; 967 968 if (!fc->root) 969 return ERR_PTR(-EINVAL); 970 971 mnt = alloc_vfsmnt(fc->source ?: "none"); 972 if (!mnt) 973 return ERR_PTR(-ENOMEM); 974 975 if (fc->sb_flags & SB_KERNMOUNT) 976 mnt->mnt.mnt_flags = MNT_INTERNAL; 977 978 atomic_inc(&fc->root->d_sb->s_active); 979 mnt->mnt.mnt_sb = fc->root->d_sb; 980 mnt->mnt.mnt_root = dget(fc->root); 981 mnt->mnt_mountpoint = mnt->mnt.mnt_root; 982 mnt->mnt_parent = mnt; 983 984 lock_mount_hash(); 985 list_add_tail(&mnt->mnt_instance, &mnt->mnt.mnt_sb->s_mounts); 986 unlock_mount_hash(); 987 return &mnt->mnt; 988 } 989 EXPORT_SYMBOL(vfs_create_mount); 990 991 struct vfsmount *fc_mount(struct fs_context *fc) 992 { 993 int err = vfs_get_tree(fc); 994 if (!err) { 995 up_write(&fc->root->d_sb->s_umount); 996 return vfs_create_mount(fc); 997 } 998 return ERR_PTR(err); 999 } 1000 EXPORT_SYMBOL(fc_mount); 1001 1002 struct vfsmount *vfs_kern_mount(struct file_system_type *type, 1003 int flags, const char *name, 1004 void *data) 1005 { 1006 struct fs_context *fc; 1007 struct vfsmount *mnt; 1008 int ret = 0; 1009 1010 if (!type) 1011 return ERR_PTR(-EINVAL); 1012 1013 fc = fs_context_for_mount(type, flags); 1014 if (IS_ERR(fc)) 1015 return ERR_CAST(fc); 1016 1017 if (name) 1018 ret = vfs_parse_fs_string(fc, "source", 1019 name, strlen(name)); 1020 if (!ret) 1021 ret = parse_monolithic_mount_data(fc, data); 1022 if (!ret) 1023 mnt = fc_mount(fc); 1024 else 1025 mnt = ERR_PTR(ret); 1026 1027 put_fs_context(fc); 1028 return mnt; 1029 } 1030 EXPORT_SYMBOL_GPL(vfs_kern_mount); 1031 1032 struct vfsmount * 1033 vfs_submount(const struct dentry *mountpoint, struct file_system_type *type, 1034 const char *name, void *data) 1035 { 1036 /* Until it is worked out how to pass the user namespace 1037 * through from the parent mount to the submount don't support 1038 * unprivileged mounts with submounts. 1039 */ 1040 if (mountpoint->d_sb->s_user_ns != &init_user_ns) 1041 return ERR_PTR(-EPERM); 1042 1043 return vfs_kern_mount(type, SB_SUBMOUNT, name, data); 1044 } 1045 EXPORT_SYMBOL_GPL(vfs_submount); 1046 1047 static struct mount *clone_mnt(struct mount *old, struct dentry *root, 1048 int flag) 1049 { 1050 struct super_block *sb = old->mnt.mnt_sb; 1051 struct mount *mnt; 1052 int err; 1053 1054 mnt = alloc_vfsmnt(old->mnt_devname); 1055 if (!mnt) 1056 return ERR_PTR(-ENOMEM); 1057 1058 if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE)) 1059 mnt->mnt_group_id = 0; /* not a peer of original */ 1060 else 1061 mnt->mnt_group_id = old->mnt_group_id; 1062 1063 if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { 1064 err = mnt_alloc_group_id(mnt); 1065 if (err) 1066 goto out_free; 1067 } 1068 1069 mnt->mnt.mnt_flags = old->mnt.mnt_flags; 1070 mnt->mnt.mnt_flags &= ~(MNT_WRITE_HOLD|MNT_MARKED|MNT_INTERNAL); 1071 1072 atomic_inc(&sb->s_active); 1073 mnt->mnt.mnt_userns = mnt_user_ns(&old->mnt); 1074 if (mnt->mnt.mnt_userns != &init_user_ns) 1075 mnt->mnt.mnt_userns = get_user_ns(mnt->mnt.mnt_userns); 1076 mnt->mnt.mnt_sb = sb; 1077 mnt->mnt.mnt_root = dget(root); 1078 mnt->mnt_mountpoint = mnt->mnt.mnt_root; 1079 mnt->mnt_parent = mnt; 1080 lock_mount_hash(); 1081 list_add_tail(&mnt->mnt_instance, &sb->s_mounts); 1082 unlock_mount_hash(); 1083 1084 if ((flag & CL_SLAVE) || 1085 ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) { 1086 list_add(&mnt->mnt_slave, &old->mnt_slave_list); 1087 mnt->mnt_master = old; 1088 CLEAR_MNT_SHARED(mnt); 1089 } else if (!(flag & CL_PRIVATE)) { 1090 if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old)) 1091 list_add(&mnt->mnt_share, &old->mnt_share); 1092 if (IS_MNT_SLAVE(old)) 1093 list_add(&mnt->mnt_slave, &old->mnt_slave); 1094 mnt->mnt_master = old->mnt_master; 1095 } else { 1096 CLEAR_MNT_SHARED(mnt); 1097 } 1098 if (flag & CL_MAKE_SHARED) 1099 set_mnt_shared(mnt); 1100 1101 /* stick the duplicate mount on the same expiry list 1102 * as the original if that was on one */ 1103 if (flag & CL_EXPIRE) { 1104 if (!list_empty(&old->mnt_expire)) 1105 list_add(&mnt->mnt_expire, &old->mnt_expire); 1106 } 1107 1108 return mnt; 1109 1110 out_free: 1111 mnt_free_id(mnt); 1112 free_vfsmnt(mnt); 1113 return ERR_PTR(err); 1114 } 1115 1116 static void cleanup_mnt(struct mount *mnt) 1117 { 1118 struct hlist_node *p; 1119 struct mount *m; 1120 /* 1121 * The warning here probably indicates that somebody messed 1122 * up a mnt_want/drop_write() pair. If this happens, the 1123 * filesystem was probably unable to make r/w->r/o transitions. 1124 * The locking used to deal with mnt_count decrement provides barriers, 1125 * so mnt_get_writers() below is safe. 1126 */ 1127 WARN_ON(mnt_get_writers(mnt)); 1128 if (unlikely(mnt->mnt_pins.first)) 1129 mnt_pin_kill(mnt); 1130 hlist_for_each_entry_safe(m, p, &mnt->mnt_stuck_children, mnt_umount) { 1131 hlist_del(&m->mnt_umount); 1132 mntput(&m->mnt); 1133 } 1134 fsnotify_vfsmount_delete(&mnt->mnt); 1135 dput(mnt->mnt.mnt_root); 1136 deactivate_super(mnt->mnt.mnt_sb); 1137 mnt_free_id(mnt); 1138 call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt); 1139 } 1140 1141 static void __cleanup_mnt(struct rcu_head *head) 1142 { 1143 cleanup_mnt(container_of(head, struct mount, mnt_rcu)); 1144 } 1145 1146 static LLIST_HEAD(delayed_mntput_list); 1147 static void delayed_mntput(struct work_struct *unused) 1148 { 1149 struct llist_node *node = llist_del_all(&delayed_mntput_list); 1150 struct mount *m, *t; 1151 1152 llist_for_each_entry_safe(m, t, node, mnt_llist) 1153 cleanup_mnt(m); 1154 } 1155 static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput); 1156 1157 static void mntput_no_expire(struct mount *mnt) 1158 { 1159 LIST_HEAD(list); 1160 int count; 1161 1162 rcu_read_lock(); 1163 if (likely(READ_ONCE(mnt->mnt_ns))) { 1164 /* 1165 * Since we don't do lock_mount_hash() here, 1166 * ->mnt_ns can change under us. However, if it's 1167 * non-NULL, then there's a reference that won't 1168 * be dropped until after an RCU delay done after 1169 * turning ->mnt_ns NULL. So if we observe it 1170 * non-NULL under rcu_read_lock(), the reference 1171 * we are dropping is not the final one. 1172 */ 1173 mnt_add_count(mnt, -1); 1174 rcu_read_unlock(); 1175 return; 1176 } 1177 lock_mount_hash(); 1178 /* 1179 * make sure that if __legitimize_mnt() has not seen us grab 1180 * mount_lock, we'll see their refcount increment here. 1181 */ 1182 smp_mb(); 1183 mnt_add_count(mnt, -1); 1184 count = mnt_get_count(mnt); 1185 if (count != 0) { 1186 WARN_ON(count < 0); 1187 rcu_read_unlock(); 1188 unlock_mount_hash(); 1189 return; 1190 } 1191 if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) { 1192 rcu_read_unlock(); 1193 unlock_mount_hash(); 1194 return; 1195 } 1196 mnt->mnt.mnt_flags |= MNT_DOOMED; 1197 rcu_read_unlock(); 1198 1199 list_del(&mnt->mnt_instance); 1200 1201 if (unlikely(!list_empty(&mnt->mnt_mounts))) { 1202 struct mount *p, *tmp; 1203 list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) { 1204 __put_mountpoint(unhash_mnt(p), &list); 1205 hlist_add_head(&p->mnt_umount, &mnt->mnt_stuck_children); 1206 } 1207 } 1208 unlock_mount_hash(); 1209 shrink_dentry_list(&list); 1210 1211 if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) { 1212 struct task_struct *task = current; 1213 if (likely(!(task->flags & PF_KTHREAD))) { 1214 init_task_work(&mnt->mnt_rcu, __cleanup_mnt); 1215 if (!task_work_add(task, &mnt->mnt_rcu, TWA_RESUME)) 1216 return; 1217 } 1218 if (llist_add(&mnt->mnt_llist, &delayed_mntput_list)) 1219 schedule_delayed_work(&delayed_mntput_work, 1); 1220 return; 1221 } 1222 cleanup_mnt(mnt); 1223 } 1224 1225 void mntput(struct vfsmount *mnt) 1226 { 1227 if (mnt) { 1228 struct mount *m = real_mount(mnt); 1229 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */ 1230 if (unlikely(m->mnt_expiry_mark)) 1231 m->mnt_expiry_mark = 0; 1232 mntput_no_expire(m); 1233 } 1234 } 1235 EXPORT_SYMBOL(mntput); 1236 1237 struct vfsmount *mntget(struct vfsmount *mnt) 1238 { 1239 if (mnt) 1240 mnt_add_count(real_mount(mnt), 1); 1241 return mnt; 1242 } 1243 EXPORT_SYMBOL(mntget); 1244 1245 /** 1246 * path_is_mountpoint() - Check if path is a mount in the current namespace. 1247 * @path: path to check 1248 * 1249 * d_mountpoint() can only be used reliably to establish if a dentry is 1250 * not mounted in any namespace and that common case is handled inline. 1251 * d_mountpoint() isn't aware of the possibility there may be multiple 1252 * mounts using a given dentry in a different namespace. This function 1253 * checks if the passed in path is a mountpoint rather than the dentry 1254 * alone. 1255 */ 1256 bool path_is_mountpoint(const struct path *path) 1257 { 1258 unsigned seq; 1259 bool res; 1260 1261 if (!d_mountpoint(path->dentry)) 1262 return false; 1263 1264 rcu_read_lock(); 1265 do { 1266 seq = read_seqbegin(&mount_lock); 1267 res = __path_is_mountpoint(path); 1268 } while (read_seqretry(&mount_lock, seq)); 1269 rcu_read_unlock(); 1270 1271 return res; 1272 } 1273 EXPORT_SYMBOL(path_is_mountpoint); 1274 1275 struct vfsmount *mnt_clone_internal(const struct path *path) 1276 { 1277 struct mount *p; 1278 p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE); 1279 if (IS_ERR(p)) 1280 return ERR_CAST(p); 1281 p->mnt.mnt_flags |= MNT_INTERNAL; 1282 return &p->mnt; 1283 } 1284 1285 #ifdef CONFIG_PROC_FS 1286 static struct mount *mnt_list_next(struct mnt_namespace *ns, 1287 struct list_head *p) 1288 { 1289 struct mount *mnt, *ret = NULL; 1290 1291 lock_ns_list(ns); 1292 list_for_each_continue(p, &ns->list) { 1293 mnt = list_entry(p, typeof(*mnt), mnt_list); 1294 if (!mnt_is_cursor(mnt)) { 1295 ret = mnt; 1296 break; 1297 } 1298 } 1299 unlock_ns_list(ns); 1300 1301 return ret; 1302 } 1303 1304 /* iterator; we want it to have access to namespace_sem, thus here... */ 1305 static void *m_start(struct seq_file *m, loff_t *pos) 1306 { 1307 struct proc_mounts *p = m->private; 1308 struct list_head *prev; 1309 1310 down_read(&namespace_sem); 1311 if (!*pos) { 1312 prev = &p->ns->list; 1313 } else { 1314 prev = &p->cursor.mnt_list; 1315 1316 /* Read after we'd reached the end? */ 1317 if (list_empty(prev)) 1318 return NULL; 1319 } 1320 1321 return mnt_list_next(p->ns, prev); 1322 } 1323 1324 static void *m_next(struct seq_file *m, void *v, loff_t *pos) 1325 { 1326 struct proc_mounts *p = m->private; 1327 struct mount *mnt = v; 1328 1329 ++*pos; 1330 return mnt_list_next(p->ns, &mnt->mnt_list); 1331 } 1332 1333 static void m_stop(struct seq_file *m, void *v) 1334 { 1335 struct proc_mounts *p = m->private; 1336 struct mount *mnt = v; 1337 1338 lock_ns_list(p->ns); 1339 if (mnt) 1340 list_move_tail(&p->cursor.mnt_list, &mnt->mnt_list); 1341 else 1342 list_del_init(&p->cursor.mnt_list); 1343 unlock_ns_list(p->ns); 1344 up_read(&namespace_sem); 1345 } 1346 1347 static int m_show(struct seq_file *m, void *v) 1348 { 1349 struct proc_mounts *p = m->private; 1350 struct mount *r = v; 1351 return p->show(m, &r->mnt); 1352 } 1353 1354 const struct seq_operations mounts_op = { 1355 .start = m_start, 1356 .next = m_next, 1357 .stop = m_stop, 1358 .show = m_show, 1359 }; 1360 1361 void mnt_cursor_del(struct mnt_namespace *ns, struct mount *cursor) 1362 { 1363 down_read(&namespace_sem); 1364 lock_ns_list(ns); 1365 list_del(&cursor->mnt_list); 1366 unlock_ns_list(ns); 1367 up_read(&namespace_sem); 1368 } 1369 #endif /* CONFIG_PROC_FS */ 1370 1371 /** 1372 * may_umount_tree - check if a mount tree is busy 1373 * @m: root of mount tree 1374 * 1375 * This is called to check if a tree of mounts has any 1376 * open files, pwds, chroots or sub mounts that are 1377 * busy. 1378 */ 1379 int may_umount_tree(struct vfsmount *m) 1380 { 1381 struct mount *mnt = real_mount(m); 1382 int actual_refs = 0; 1383 int minimum_refs = 0; 1384 struct mount *p; 1385 BUG_ON(!m); 1386 1387 /* write lock needed for mnt_get_count */ 1388 lock_mount_hash(); 1389 for (p = mnt; p; p = next_mnt(p, mnt)) { 1390 actual_refs += mnt_get_count(p); 1391 minimum_refs += 2; 1392 } 1393 unlock_mount_hash(); 1394 1395 if (actual_refs > minimum_refs) 1396 return 0; 1397 1398 return 1; 1399 } 1400 1401 EXPORT_SYMBOL(may_umount_tree); 1402 1403 /** 1404 * may_umount - check if a mount point is busy 1405 * @mnt: root of mount 1406 * 1407 * This is called to check if a mount point has any 1408 * open files, pwds, chroots or sub mounts. If the 1409 * mount has sub mounts this will return busy 1410 * regardless of whether the sub mounts are busy. 1411 * 1412 * Doesn't take quota and stuff into account. IOW, in some cases it will 1413 * give false negatives. The main reason why it's here is that we need 1414 * a non-destructive way to look for easily umountable filesystems. 1415 */ 1416 int may_umount(struct vfsmount *mnt) 1417 { 1418 int ret = 1; 1419 down_read(&namespace_sem); 1420 lock_mount_hash(); 1421 if (propagate_mount_busy(real_mount(mnt), 2)) 1422 ret = 0; 1423 unlock_mount_hash(); 1424 up_read(&namespace_sem); 1425 return ret; 1426 } 1427 1428 EXPORT_SYMBOL(may_umount); 1429 1430 static void namespace_unlock(void) 1431 { 1432 struct hlist_head head; 1433 struct hlist_node *p; 1434 struct mount *m; 1435 LIST_HEAD(list); 1436 1437 hlist_move_list(&unmounted, &head); 1438 list_splice_init(&ex_mountpoints, &list); 1439 1440 up_write(&namespace_sem); 1441 1442 shrink_dentry_list(&list); 1443 1444 if (likely(hlist_empty(&head))) 1445 return; 1446 1447 synchronize_rcu_expedited(); 1448 1449 hlist_for_each_entry_safe(m, p, &head, mnt_umount) { 1450 hlist_del(&m->mnt_umount); 1451 mntput(&m->mnt); 1452 } 1453 } 1454 1455 static inline void namespace_lock(void) 1456 { 1457 down_write(&namespace_sem); 1458 } 1459 1460 enum umount_tree_flags { 1461 UMOUNT_SYNC = 1, 1462 UMOUNT_PROPAGATE = 2, 1463 UMOUNT_CONNECTED = 4, 1464 }; 1465 1466 static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how) 1467 { 1468 /* Leaving mounts connected is only valid for lazy umounts */ 1469 if (how & UMOUNT_SYNC) 1470 return true; 1471 1472 /* A mount without a parent has nothing to be connected to */ 1473 if (!mnt_has_parent(mnt)) 1474 return true; 1475 1476 /* Because the reference counting rules change when mounts are 1477 * unmounted and connected, umounted mounts may not be 1478 * connected to mounted mounts. 1479 */ 1480 if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT)) 1481 return true; 1482 1483 /* Has it been requested that the mount remain connected? */ 1484 if (how & UMOUNT_CONNECTED) 1485 return false; 1486 1487 /* Is the mount locked such that it needs to remain connected? */ 1488 if (IS_MNT_LOCKED(mnt)) 1489 return false; 1490 1491 /* By default disconnect the mount */ 1492 return true; 1493 } 1494 1495 /* 1496 * mount_lock must be held 1497 * namespace_sem must be held for write 1498 */ 1499 static void umount_tree(struct mount *mnt, enum umount_tree_flags how) 1500 { 1501 LIST_HEAD(tmp_list); 1502 struct mount *p; 1503 1504 if (how & UMOUNT_PROPAGATE) 1505 propagate_mount_unlock(mnt); 1506 1507 /* Gather the mounts to umount */ 1508 for (p = mnt; p; p = next_mnt(p, mnt)) { 1509 p->mnt.mnt_flags |= MNT_UMOUNT; 1510 list_move(&p->mnt_list, &tmp_list); 1511 } 1512 1513 /* Hide the mounts from mnt_mounts */ 1514 list_for_each_entry(p, &tmp_list, mnt_list) { 1515 list_del_init(&p->mnt_child); 1516 } 1517 1518 /* Add propogated mounts to the tmp_list */ 1519 if (how & UMOUNT_PROPAGATE) 1520 propagate_umount(&tmp_list); 1521 1522 while (!list_empty(&tmp_list)) { 1523 struct mnt_namespace *ns; 1524 bool disconnect; 1525 p = list_first_entry(&tmp_list, struct mount, mnt_list); 1526 list_del_init(&p->mnt_expire); 1527 list_del_init(&p->mnt_list); 1528 ns = p->mnt_ns; 1529 if (ns) { 1530 ns->mounts--; 1531 __touch_mnt_namespace(ns); 1532 } 1533 p->mnt_ns = NULL; 1534 if (how & UMOUNT_SYNC) 1535 p->mnt.mnt_flags |= MNT_SYNC_UMOUNT; 1536 1537 disconnect = disconnect_mount(p, how); 1538 if (mnt_has_parent(p)) { 1539 mnt_add_count(p->mnt_parent, -1); 1540 if (!disconnect) { 1541 /* Don't forget about p */ 1542 list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts); 1543 } else { 1544 umount_mnt(p); 1545 } 1546 } 1547 change_mnt_propagation(p, MS_PRIVATE); 1548 if (disconnect) 1549 hlist_add_head(&p->mnt_umount, &unmounted); 1550 } 1551 } 1552 1553 static void shrink_submounts(struct mount *mnt); 1554 1555 static int do_umount_root(struct super_block *sb) 1556 { 1557 int ret = 0; 1558 1559 down_write(&sb->s_umount); 1560 if (!sb_rdonly(sb)) { 1561 struct fs_context *fc; 1562 1563 fc = fs_context_for_reconfigure(sb->s_root, SB_RDONLY, 1564 SB_RDONLY); 1565 if (IS_ERR(fc)) { 1566 ret = PTR_ERR(fc); 1567 } else { 1568 ret = parse_monolithic_mount_data(fc, NULL); 1569 if (!ret) 1570 ret = reconfigure_super(fc); 1571 put_fs_context(fc); 1572 } 1573 } 1574 up_write(&sb->s_umount); 1575 return ret; 1576 } 1577 1578 static int do_umount(struct mount *mnt, int flags) 1579 { 1580 struct super_block *sb = mnt->mnt.mnt_sb; 1581 int retval; 1582 1583 retval = security_sb_umount(&mnt->mnt, flags); 1584 if (retval) 1585 return retval; 1586 1587 /* 1588 * Allow userspace to request a mountpoint be expired rather than 1589 * unmounting unconditionally. Unmount only happens if: 1590 * (1) the mark is already set (the mark is cleared by mntput()) 1591 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] 1592 */ 1593 if (flags & MNT_EXPIRE) { 1594 if (&mnt->mnt == current->fs->root.mnt || 1595 flags & (MNT_FORCE | MNT_DETACH)) 1596 return -EINVAL; 1597 1598 /* 1599 * probably don't strictly need the lock here if we examined 1600 * all race cases, but it's a slowpath. 1601 */ 1602 lock_mount_hash(); 1603 if (mnt_get_count(mnt) != 2) { 1604 unlock_mount_hash(); 1605 return -EBUSY; 1606 } 1607 unlock_mount_hash(); 1608 1609 if (!xchg(&mnt->mnt_expiry_mark, 1)) 1610 return -EAGAIN; 1611 } 1612 1613 /* 1614 * If we may have to abort operations to get out of this 1615 * mount, and they will themselves hold resources we must 1616 * allow the fs to do things. In the Unix tradition of 1617 * 'Gee thats tricky lets do it in userspace' the umount_begin 1618 * might fail to complete on the first run through as other tasks 1619 * must return, and the like. Thats for the mount program to worry 1620 * about for the moment. 1621 */ 1622 1623 if (flags & MNT_FORCE && sb->s_op->umount_begin) { 1624 sb->s_op->umount_begin(sb); 1625 } 1626 1627 /* 1628 * No sense to grab the lock for this test, but test itself looks 1629 * somewhat bogus. Suggestions for better replacement? 1630 * Ho-hum... In principle, we might treat that as umount + switch 1631 * to rootfs. GC would eventually take care of the old vfsmount. 1632 * Actually it makes sense, especially if rootfs would contain a 1633 * /reboot - static binary that would close all descriptors and 1634 * call reboot(9). Then init(8) could umount root and exec /reboot. 1635 */ 1636 if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { 1637 /* 1638 * Special case for "unmounting" root ... 1639 * we just try to remount it readonly. 1640 */ 1641 if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) 1642 return -EPERM; 1643 return do_umount_root(sb); 1644 } 1645 1646 namespace_lock(); 1647 lock_mount_hash(); 1648 1649 /* Recheck MNT_LOCKED with the locks held */ 1650 retval = -EINVAL; 1651 if (mnt->mnt.mnt_flags & MNT_LOCKED) 1652 goto out; 1653 1654 event++; 1655 if (flags & MNT_DETACH) { 1656 if (!list_empty(&mnt->mnt_list)) 1657 umount_tree(mnt, UMOUNT_PROPAGATE); 1658 retval = 0; 1659 } else { 1660 shrink_submounts(mnt); 1661 retval = -EBUSY; 1662 if (!propagate_mount_busy(mnt, 2)) { 1663 if (!list_empty(&mnt->mnt_list)) 1664 umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC); 1665 retval = 0; 1666 } 1667 } 1668 out: 1669 unlock_mount_hash(); 1670 namespace_unlock(); 1671 return retval; 1672 } 1673 1674 /* 1675 * __detach_mounts - lazily unmount all mounts on the specified dentry 1676 * 1677 * During unlink, rmdir, and d_drop it is possible to loose the path 1678 * to an existing mountpoint, and wind up leaking the mount. 1679 * detach_mounts allows lazily unmounting those mounts instead of 1680 * leaking them. 1681 * 1682 * The caller may hold dentry->d_inode->i_mutex. 1683 */ 1684 void __detach_mounts(struct dentry *dentry) 1685 { 1686 struct mountpoint *mp; 1687 struct mount *mnt; 1688 1689 namespace_lock(); 1690 lock_mount_hash(); 1691 mp = lookup_mountpoint(dentry); 1692 if (!mp) 1693 goto out_unlock; 1694 1695 event++; 1696 while (!hlist_empty(&mp->m_list)) { 1697 mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list); 1698 if (mnt->mnt.mnt_flags & MNT_UMOUNT) { 1699 umount_mnt(mnt); 1700 hlist_add_head(&mnt->mnt_umount, &unmounted); 1701 } 1702 else umount_tree(mnt, UMOUNT_CONNECTED); 1703 } 1704 put_mountpoint(mp); 1705 out_unlock: 1706 unlock_mount_hash(); 1707 namespace_unlock(); 1708 } 1709 1710 /* 1711 * Is the caller allowed to modify his namespace? 1712 */ 1713 static inline bool may_mount(void) 1714 { 1715 return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN); 1716 } 1717 1718 #ifdef CONFIG_MANDATORY_FILE_LOCKING 1719 static inline bool may_mandlock(void) 1720 { 1721 return capable(CAP_SYS_ADMIN); 1722 } 1723 #else 1724 static inline bool may_mandlock(void) 1725 { 1726 pr_warn("VFS: \"mand\" mount option not supported"); 1727 return false; 1728 } 1729 #endif 1730 1731 static int can_umount(const struct path *path, int flags) 1732 { 1733 struct mount *mnt = real_mount(path->mnt); 1734 1735 if (!may_mount()) 1736 return -EPERM; 1737 if (path->dentry != path->mnt->mnt_root) 1738 return -EINVAL; 1739 if (!check_mnt(mnt)) 1740 return -EINVAL; 1741 if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */ 1742 return -EINVAL; 1743 if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN)) 1744 return -EPERM; 1745 return 0; 1746 } 1747 1748 // caller is responsible for flags being sane 1749 int path_umount(struct path *path, int flags) 1750 { 1751 struct mount *mnt = real_mount(path->mnt); 1752 int ret; 1753 1754 ret = can_umount(path, flags); 1755 if (!ret) 1756 ret = do_umount(mnt, flags); 1757 1758 /* we mustn't call path_put() as that would clear mnt_expiry_mark */ 1759 dput(path->dentry); 1760 mntput_no_expire(mnt); 1761 return ret; 1762 } 1763 1764 static int ksys_umount(char __user *name, int flags) 1765 { 1766 int lookup_flags = LOOKUP_MOUNTPOINT; 1767 struct path path; 1768 int ret; 1769 1770 // basic validity checks done first 1771 if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) 1772 return -EINVAL; 1773 1774 if (!(flags & UMOUNT_NOFOLLOW)) 1775 lookup_flags |= LOOKUP_FOLLOW; 1776 ret = user_path_at(AT_FDCWD, name, lookup_flags, &path); 1777 if (ret) 1778 return ret; 1779 return path_umount(&path, flags); 1780 } 1781 1782 SYSCALL_DEFINE2(umount, char __user *, name, int, flags) 1783 { 1784 return ksys_umount(name, flags); 1785 } 1786 1787 #ifdef __ARCH_WANT_SYS_OLDUMOUNT 1788 1789 /* 1790 * The 2.0 compatible umount. No flags. 1791 */ 1792 SYSCALL_DEFINE1(oldumount, char __user *, name) 1793 { 1794 return ksys_umount(name, 0); 1795 } 1796 1797 #endif 1798 1799 static bool is_mnt_ns_file(struct dentry *dentry) 1800 { 1801 /* Is this a proxy for a mount namespace? */ 1802 return dentry->d_op == &ns_dentry_operations && 1803 dentry->d_fsdata == &mntns_operations; 1804 } 1805 1806 static struct mnt_namespace *to_mnt_ns(struct ns_common *ns) 1807 { 1808 return container_of(ns, struct mnt_namespace, ns); 1809 } 1810 1811 struct ns_common *from_mnt_ns(struct mnt_namespace *mnt) 1812 { 1813 return &mnt->ns; 1814 } 1815 1816 static bool mnt_ns_loop(struct dentry *dentry) 1817 { 1818 /* Could bind mounting the mount namespace inode cause a 1819 * mount namespace loop? 1820 */ 1821 struct mnt_namespace *mnt_ns; 1822 if (!is_mnt_ns_file(dentry)) 1823 return false; 1824 1825 mnt_ns = to_mnt_ns(get_proc_ns(dentry->d_inode)); 1826 return current->nsproxy->mnt_ns->seq >= mnt_ns->seq; 1827 } 1828 1829 struct mount *copy_tree(struct mount *mnt, struct dentry *dentry, 1830 int flag) 1831 { 1832 struct mount *res, *p, *q, *r, *parent; 1833 1834 if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt)) 1835 return ERR_PTR(-EINVAL); 1836 1837 if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry)) 1838 return ERR_PTR(-EINVAL); 1839 1840 res = q = clone_mnt(mnt, dentry, flag); 1841 if (IS_ERR(q)) 1842 return q; 1843 1844 q->mnt_mountpoint = mnt->mnt_mountpoint; 1845 1846 p = mnt; 1847 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { 1848 struct mount *s; 1849 if (!is_subdir(r->mnt_mountpoint, dentry)) 1850 continue; 1851 1852 for (s = r; s; s = next_mnt(s, r)) { 1853 if (!(flag & CL_COPY_UNBINDABLE) && 1854 IS_MNT_UNBINDABLE(s)) { 1855 if (s->mnt.mnt_flags & MNT_LOCKED) { 1856 /* Both unbindable and locked. */ 1857 q = ERR_PTR(-EPERM); 1858 goto out; 1859 } else { 1860 s = skip_mnt_tree(s); 1861 continue; 1862 } 1863 } 1864 if (!(flag & CL_COPY_MNT_NS_FILE) && 1865 is_mnt_ns_file(s->mnt.mnt_root)) { 1866 s = skip_mnt_tree(s); 1867 continue; 1868 } 1869 while (p != s->mnt_parent) { 1870 p = p->mnt_parent; 1871 q = q->mnt_parent; 1872 } 1873 p = s; 1874 parent = q; 1875 q = clone_mnt(p, p->mnt.mnt_root, flag); 1876 if (IS_ERR(q)) 1877 goto out; 1878 lock_mount_hash(); 1879 list_add_tail(&q->mnt_list, &res->mnt_list); 1880 attach_mnt(q, parent, p->mnt_mp); 1881 unlock_mount_hash(); 1882 } 1883 } 1884 return res; 1885 out: 1886 if (res) { 1887 lock_mount_hash(); 1888 umount_tree(res, UMOUNT_SYNC); 1889 unlock_mount_hash(); 1890 } 1891 return q; 1892 } 1893 1894 /* Caller should check returned pointer for errors */ 1895 1896 struct vfsmount *collect_mounts(const struct path *path) 1897 { 1898 struct mount *tree; 1899 namespace_lock(); 1900 if (!check_mnt(real_mount(path->mnt))) 1901 tree = ERR_PTR(-EINVAL); 1902 else 1903 tree = copy_tree(real_mount(path->mnt), path->dentry, 1904 CL_COPY_ALL | CL_PRIVATE); 1905 namespace_unlock(); 1906 if (IS_ERR(tree)) 1907 return ERR_CAST(tree); 1908 return &tree->mnt; 1909 } 1910 1911 static void free_mnt_ns(struct mnt_namespace *); 1912 static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *, bool); 1913 1914 void dissolve_on_fput(struct vfsmount *mnt) 1915 { 1916 struct mnt_namespace *ns; 1917 namespace_lock(); 1918 lock_mount_hash(); 1919 ns = real_mount(mnt)->mnt_ns; 1920 if (ns) { 1921 if (is_anon_ns(ns)) 1922 umount_tree(real_mount(mnt), UMOUNT_CONNECTED); 1923 else 1924 ns = NULL; 1925 } 1926 unlock_mount_hash(); 1927 namespace_unlock(); 1928 if (ns) 1929 free_mnt_ns(ns); 1930 } 1931 1932 void drop_collected_mounts(struct vfsmount *mnt) 1933 { 1934 namespace_lock(); 1935 lock_mount_hash(); 1936 umount_tree(real_mount(mnt), 0); 1937 unlock_mount_hash(); 1938 namespace_unlock(); 1939 } 1940 1941 static bool has_locked_children(struct mount *mnt, struct dentry *dentry) 1942 { 1943 struct mount *child; 1944 1945 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { 1946 if (!is_subdir(child->mnt_mountpoint, dentry)) 1947 continue; 1948 1949 if (child->mnt.mnt_flags & MNT_LOCKED) 1950 return true; 1951 } 1952 return false; 1953 } 1954 1955 /** 1956 * clone_private_mount - create a private clone of a path 1957 * @path: path to clone 1958 * 1959 * This creates a new vfsmount, which will be the clone of @path. The new mount 1960 * will not be attached anywhere in the namespace and will be private (i.e. 1961 * changes to the originating mount won't be propagated into this). 1962 * 1963 * Release with mntput(). 1964 */ 1965 struct vfsmount *clone_private_mount(const struct path *path) 1966 { 1967 struct mount *old_mnt = real_mount(path->mnt); 1968 struct mount *new_mnt; 1969 1970 down_read(&namespace_sem); 1971 if (IS_MNT_UNBINDABLE(old_mnt)) 1972 goto invalid; 1973 1974 if (!check_mnt(old_mnt)) 1975 goto invalid; 1976 1977 if (has_locked_children(old_mnt, path->dentry)) 1978 goto invalid; 1979 1980 new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE); 1981 up_read(&namespace_sem); 1982 1983 if (IS_ERR(new_mnt)) 1984 return ERR_CAST(new_mnt); 1985 1986 /* Longterm mount to be removed by kern_unmount*() */ 1987 new_mnt->mnt_ns = MNT_NS_INTERNAL; 1988 1989 return &new_mnt->mnt; 1990 1991 invalid: 1992 up_read(&namespace_sem); 1993 return ERR_PTR(-EINVAL); 1994 } 1995 EXPORT_SYMBOL_GPL(clone_private_mount); 1996 1997 int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, 1998 struct vfsmount *root) 1999 { 2000 struct mount *mnt; 2001 int res = f(root, arg); 2002 if (res) 2003 return res; 2004 list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) { 2005 res = f(&mnt->mnt, arg); 2006 if (res) 2007 return res; 2008 } 2009 return 0; 2010 } 2011 2012 static void lock_mnt_tree(struct mount *mnt) 2013 { 2014 struct mount *p; 2015 2016 for (p = mnt; p; p = next_mnt(p, mnt)) { 2017 int flags = p->mnt.mnt_flags; 2018 /* Don't allow unprivileged users to change mount flags */ 2019 flags |= MNT_LOCK_ATIME; 2020 2021 if (flags & MNT_READONLY) 2022 flags |= MNT_LOCK_READONLY; 2023 2024 if (flags & MNT_NODEV) 2025 flags |= MNT_LOCK_NODEV; 2026 2027 if (flags & MNT_NOSUID) 2028 flags |= MNT_LOCK_NOSUID; 2029 2030 if (flags & MNT_NOEXEC) 2031 flags |= MNT_LOCK_NOEXEC; 2032 /* Don't allow unprivileged users to reveal what is under a mount */ 2033 if (list_empty(&p->mnt_expire)) 2034 flags |= MNT_LOCKED; 2035 p->mnt.mnt_flags = flags; 2036 } 2037 } 2038 2039 static void cleanup_group_ids(struct mount *mnt, struct mount *end) 2040 { 2041 struct mount *p; 2042 2043 for (p = mnt; p != end; p = next_mnt(p, mnt)) { 2044 if (p->mnt_group_id && !IS_MNT_SHARED(p)) 2045 mnt_release_group_id(p); 2046 } 2047 } 2048 2049 static int invent_group_ids(struct mount *mnt, bool recurse) 2050 { 2051 struct mount *p; 2052 2053 for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { 2054 if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { 2055 int err = mnt_alloc_group_id(p); 2056 if (err) { 2057 cleanup_group_ids(mnt, p); 2058 return err; 2059 } 2060 } 2061 } 2062 2063 return 0; 2064 } 2065 2066 int count_mounts(struct mnt_namespace *ns, struct mount *mnt) 2067 { 2068 unsigned int max = READ_ONCE(sysctl_mount_max); 2069 unsigned int mounts = 0, old, pending, sum; 2070 struct mount *p; 2071 2072 for (p = mnt; p; p = next_mnt(p, mnt)) 2073 mounts++; 2074 2075 old = ns->mounts; 2076 pending = ns->pending_mounts; 2077 sum = old + pending; 2078 if ((old > sum) || 2079 (pending > sum) || 2080 (max < sum) || 2081 (mounts > (max - sum))) 2082 return -ENOSPC; 2083 2084 ns->pending_mounts = pending + mounts; 2085 return 0; 2086 } 2087 2088 /* 2089 * @source_mnt : mount tree to be attached 2090 * @nd : place the mount tree @source_mnt is attached 2091 * @parent_nd : if non-null, detach the source_mnt from its parent and 2092 * store the parent mount and mountpoint dentry. 2093 * (done when source_mnt is moved) 2094 * 2095 * NOTE: in the table below explains the semantics when a source mount 2096 * of a given type is attached to a destination mount of a given type. 2097 * --------------------------------------------------------------------------- 2098 * | BIND MOUNT OPERATION | 2099 * |************************************************************************** 2100 * | source-->| shared | private | slave | unbindable | 2101 * | dest | | | | | 2102 * | | | | | | | 2103 * | v | | | | | 2104 * |************************************************************************** 2105 * | shared | shared (++) | shared (+) | shared(+++)| invalid | 2106 * | | | | | | 2107 * |non-shared| shared (+) | private | slave (*) | invalid | 2108 * *************************************************************************** 2109 * A bind operation clones the source mount and mounts the clone on the 2110 * destination mount. 2111 * 2112 * (++) the cloned mount is propagated to all the mounts in the propagation 2113 * tree of the destination mount and the cloned mount is added to 2114 * the peer group of the source mount. 2115 * (+) the cloned mount is created under the destination mount and is marked 2116 * as shared. The cloned mount is added to the peer group of the source 2117 * mount. 2118 * (+++) the mount is propagated to all the mounts in the propagation tree 2119 * of the destination mount and the cloned mount is made slave 2120 * of the same master as that of the source mount. The cloned mount 2121 * is marked as 'shared and slave'. 2122 * (*) the cloned mount is made a slave of the same master as that of the 2123 * source mount. 2124 * 2125 * --------------------------------------------------------------------------- 2126 * | MOVE MOUNT OPERATION | 2127 * |************************************************************************** 2128 * | source-->| shared | private | slave | unbindable | 2129 * | dest | | | | | 2130 * | | | | | | | 2131 * | v | | | | | 2132 * |************************************************************************** 2133 * | shared | shared (+) | shared (+) | shared(+++) | invalid | 2134 * | | | | | | 2135 * |non-shared| shared (+*) | private | slave (*) | unbindable | 2136 * *************************************************************************** 2137 * 2138 * (+) the mount is moved to the destination. And is then propagated to 2139 * all the mounts in the propagation tree of the destination mount. 2140 * (+*) the mount is moved to the destination. 2141 * (+++) the mount is moved to the destination and is then propagated to 2142 * all the mounts belonging to the destination mount's propagation tree. 2143 * the mount is marked as 'shared and slave'. 2144 * (*) the mount continues to be a slave at the new location. 2145 * 2146 * if the source mount is a tree, the operations explained above is 2147 * applied to each mount in the tree. 2148 * Must be called without spinlocks held, since this function can sleep 2149 * in allocations. 2150 */ 2151 static int attach_recursive_mnt(struct mount *source_mnt, 2152 struct mount *dest_mnt, 2153 struct mountpoint *dest_mp, 2154 bool moving) 2155 { 2156 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; 2157 HLIST_HEAD(tree_list); 2158 struct mnt_namespace *ns = dest_mnt->mnt_ns; 2159 struct mountpoint *smp; 2160 struct mount *child, *p; 2161 struct hlist_node *n; 2162 int err; 2163 2164 /* Preallocate a mountpoint in case the new mounts need 2165 * to be tucked under other mounts. 2166 */ 2167 smp = get_mountpoint(source_mnt->mnt.mnt_root); 2168 if (IS_ERR(smp)) 2169 return PTR_ERR(smp); 2170 2171 /* Is there space to add these mounts to the mount namespace? */ 2172 if (!moving) { 2173 err = count_mounts(ns, source_mnt); 2174 if (err) 2175 goto out; 2176 } 2177 2178 if (IS_MNT_SHARED(dest_mnt)) { 2179 err = invent_group_ids(source_mnt, true); 2180 if (err) 2181 goto out; 2182 err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list); 2183 lock_mount_hash(); 2184 if (err) 2185 goto out_cleanup_ids; 2186 for (p = source_mnt; p; p = next_mnt(p, source_mnt)) 2187 set_mnt_shared(p); 2188 } else { 2189 lock_mount_hash(); 2190 } 2191 if (moving) { 2192 unhash_mnt(source_mnt); 2193 attach_mnt(source_mnt, dest_mnt, dest_mp); 2194 touch_mnt_namespace(source_mnt->mnt_ns); 2195 } else { 2196 if (source_mnt->mnt_ns) { 2197 /* move from anon - the caller will destroy */ 2198 list_del_init(&source_mnt->mnt_ns->list); 2199 } 2200 mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt); 2201 commit_tree(source_mnt); 2202 } 2203 2204 hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) { 2205 struct mount *q; 2206 hlist_del_init(&child->mnt_hash); 2207 q = __lookup_mnt(&child->mnt_parent->mnt, 2208 child->mnt_mountpoint); 2209 if (q) 2210 mnt_change_mountpoint(child, smp, q); 2211 /* Notice when we are propagating across user namespaces */ 2212 if (child->mnt_parent->mnt_ns->user_ns != user_ns) 2213 lock_mnt_tree(child); 2214 child->mnt.mnt_flags &= ~MNT_LOCKED; 2215 commit_tree(child); 2216 } 2217 put_mountpoint(smp); 2218 unlock_mount_hash(); 2219 2220 return 0; 2221 2222 out_cleanup_ids: 2223 while (!hlist_empty(&tree_list)) { 2224 child = hlist_entry(tree_list.first, struct mount, mnt_hash); 2225 child->mnt_parent->mnt_ns->pending_mounts = 0; 2226 umount_tree(child, UMOUNT_SYNC); 2227 } 2228 unlock_mount_hash(); 2229 cleanup_group_ids(source_mnt, NULL); 2230 out: 2231 ns->pending_mounts = 0; 2232 2233 read_seqlock_excl(&mount_lock); 2234 put_mountpoint(smp); 2235 read_sequnlock_excl(&mount_lock); 2236 2237 return err; 2238 } 2239 2240 static struct mountpoint *lock_mount(struct path *path) 2241 { 2242 struct vfsmount *mnt; 2243 struct dentry *dentry = path->dentry; 2244 retry: 2245 inode_lock(dentry->d_inode); 2246 if (unlikely(cant_mount(dentry))) { 2247 inode_unlock(dentry->d_inode); 2248 return ERR_PTR(-ENOENT); 2249 } 2250 namespace_lock(); 2251 mnt = lookup_mnt(path); 2252 if (likely(!mnt)) { 2253 struct mountpoint *mp = get_mountpoint(dentry); 2254 if (IS_ERR(mp)) { 2255 namespace_unlock(); 2256 inode_unlock(dentry->d_inode); 2257 return mp; 2258 } 2259 return mp; 2260 } 2261 namespace_unlock(); 2262 inode_unlock(path->dentry->d_inode); 2263 path_put(path); 2264 path->mnt = mnt; 2265 dentry = path->dentry = dget(mnt->mnt_root); 2266 goto retry; 2267 } 2268 2269 static void unlock_mount(struct mountpoint *where) 2270 { 2271 struct dentry *dentry = where->m_dentry; 2272 2273 read_seqlock_excl(&mount_lock); 2274 put_mountpoint(where); 2275 read_sequnlock_excl(&mount_lock); 2276 2277 namespace_unlock(); 2278 inode_unlock(dentry->d_inode); 2279 } 2280 2281 static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp) 2282 { 2283 if (mnt->mnt.mnt_sb->s_flags & SB_NOUSER) 2284 return -EINVAL; 2285 2286 if (d_is_dir(mp->m_dentry) != 2287 d_is_dir(mnt->mnt.mnt_root)) 2288 return -ENOTDIR; 2289 2290 return attach_recursive_mnt(mnt, p, mp, false); 2291 } 2292 2293 /* 2294 * Sanity check the flags to change_mnt_propagation. 2295 */ 2296 2297 static int flags_to_propagation_type(int ms_flags) 2298 { 2299 int type = ms_flags & ~(MS_REC | MS_SILENT); 2300 2301 /* Fail if any non-propagation flags are set */ 2302 if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) 2303 return 0; 2304 /* Only one propagation flag should be set */ 2305 if (!is_power_of_2(type)) 2306 return 0; 2307 return type; 2308 } 2309 2310 /* 2311 * recursively change the type of the mountpoint. 2312 */ 2313 static int do_change_type(struct path *path, int ms_flags) 2314 { 2315 struct mount *m; 2316 struct mount *mnt = real_mount(path->mnt); 2317 int recurse = ms_flags & MS_REC; 2318 int type; 2319 int err = 0; 2320 2321 if (path->dentry != path->mnt->mnt_root) 2322 return -EINVAL; 2323 2324 type = flags_to_propagation_type(ms_flags); 2325 if (!type) 2326 return -EINVAL; 2327 2328 namespace_lock(); 2329 if (type == MS_SHARED) { 2330 err = invent_group_ids(mnt, recurse); 2331 if (err) 2332 goto out_unlock; 2333 } 2334 2335 lock_mount_hash(); 2336 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) 2337 change_mnt_propagation(m, type); 2338 unlock_mount_hash(); 2339 2340 out_unlock: 2341 namespace_unlock(); 2342 return err; 2343 } 2344 2345 static struct mount *__do_loopback(struct path *old_path, int recurse) 2346 { 2347 struct mount *mnt = ERR_PTR(-EINVAL), *old = real_mount(old_path->mnt); 2348 2349 if (IS_MNT_UNBINDABLE(old)) 2350 return mnt; 2351 2352 if (!check_mnt(old) && old_path->dentry->d_op != &ns_dentry_operations) 2353 return mnt; 2354 2355 if (!recurse && has_locked_children(old, old_path->dentry)) 2356 return mnt; 2357 2358 if (recurse) 2359 mnt = copy_tree(old, old_path->dentry, CL_COPY_MNT_NS_FILE); 2360 else 2361 mnt = clone_mnt(old, old_path->dentry, 0); 2362 2363 if (!IS_ERR(mnt)) 2364 mnt->mnt.mnt_flags &= ~MNT_LOCKED; 2365 2366 return mnt; 2367 } 2368 2369 /* 2370 * do loopback mount. 2371 */ 2372 static int do_loopback(struct path *path, const char *old_name, 2373 int recurse) 2374 { 2375 struct path old_path; 2376 struct mount *mnt = NULL, *parent; 2377 struct mountpoint *mp; 2378 int err; 2379 if (!old_name || !*old_name) 2380 return -EINVAL; 2381 err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); 2382 if (err) 2383 return err; 2384 2385 err = -EINVAL; 2386 if (mnt_ns_loop(old_path.dentry)) 2387 goto out; 2388 2389 mp = lock_mount(path); 2390 if (IS_ERR(mp)) { 2391 err = PTR_ERR(mp); 2392 goto out; 2393 } 2394 2395 parent = real_mount(path->mnt); 2396 if (!check_mnt(parent)) 2397 goto out2; 2398 2399 mnt = __do_loopback(&old_path, recurse); 2400 if (IS_ERR(mnt)) { 2401 err = PTR_ERR(mnt); 2402 goto out2; 2403 } 2404 2405 err = graft_tree(mnt, parent, mp); 2406 if (err) { 2407 lock_mount_hash(); 2408 umount_tree(mnt, UMOUNT_SYNC); 2409 unlock_mount_hash(); 2410 } 2411 out2: 2412 unlock_mount(mp); 2413 out: 2414 path_put(&old_path); 2415 return err; 2416 } 2417 2418 static struct file *open_detached_copy(struct path *path, bool recursive) 2419 { 2420 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; 2421 struct mnt_namespace *ns = alloc_mnt_ns(user_ns, true); 2422 struct mount *mnt, *p; 2423 struct file *file; 2424 2425 if (IS_ERR(ns)) 2426 return ERR_CAST(ns); 2427 2428 namespace_lock(); 2429 mnt = __do_loopback(path, recursive); 2430 if (IS_ERR(mnt)) { 2431 namespace_unlock(); 2432 free_mnt_ns(ns); 2433 return ERR_CAST(mnt); 2434 } 2435 2436 lock_mount_hash(); 2437 for (p = mnt; p; p = next_mnt(p, mnt)) { 2438 p->mnt_ns = ns; 2439 ns->mounts++; 2440 } 2441 ns->root = mnt; 2442 list_add_tail(&ns->list, &mnt->mnt_list); 2443 mntget(&mnt->mnt); 2444 unlock_mount_hash(); 2445 namespace_unlock(); 2446 2447 mntput(path->mnt); 2448 path->mnt = &mnt->mnt; 2449 file = dentry_open(path, O_PATH, current_cred()); 2450 if (IS_ERR(file)) 2451 dissolve_on_fput(path->mnt); 2452 else 2453 file->f_mode |= FMODE_NEED_UNMOUNT; 2454 return file; 2455 } 2456 2457 SYSCALL_DEFINE3(open_tree, int, dfd, const char __user *, filename, unsigned, flags) 2458 { 2459 struct file *file; 2460 struct path path; 2461 int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW; 2462 bool detached = flags & OPEN_TREE_CLONE; 2463 int error; 2464 int fd; 2465 2466 BUILD_BUG_ON(OPEN_TREE_CLOEXEC != O_CLOEXEC); 2467 2468 if (flags & ~(AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_RECURSIVE | 2469 AT_SYMLINK_NOFOLLOW | OPEN_TREE_CLONE | 2470 OPEN_TREE_CLOEXEC)) 2471 return -EINVAL; 2472 2473 if ((flags & (AT_RECURSIVE | OPEN_TREE_CLONE)) == AT_RECURSIVE) 2474 return -EINVAL; 2475 2476 if (flags & AT_NO_AUTOMOUNT) 2477 lookup_flags &= ~LOOKUP_AUTOMOUNT; 2478 if (flags & AT_SYMLINK_NOFOLLOW) 2479 lookup_flags &= ~LOOKUP_FOLLOW; 2480 if (flags & AT_EMPTY_PATH) 2481 lookup_flags |= LOOKUP_EMPTY; 2482 2483 if (detached && !may_mount()) 2484 return -EPERM; 2485 2486 fd = get_unused_fd_flags(flags & O_CLOEXEC); 2487 if (fd < 0) 2488 return fd; 2489 2490 error = user_path_at(dfd, filename, lookup_flags, &path); 2491 if (unlikely(error)) { 2492 file = ERR_PTR(error); 2493 } else { 2494 if (detached) 2495 file = open_detached_copy(&path, flags & AT_RECURSIVE); 2496 else 2497 file = dentry_open(&path, O_PATH, current_cred()); 2498 path_put(&path); 2499 } 2500 if (IS_ERR(file)) { 2501 put_unused_fd(fd); 2502 return PTR_ERR(file); 2503 } 2504 fd_install(fd, file); 2505 return fd; 2506 } 2507 2508 /* 2509 * Don't allow locked mount flags to be cleared. 2510 * 2511 * No locks need to be held here while testing the various MNT_LOCK 2512 * flags because those flags can never be cleared once they are set. 2513 */ 2514 static bool can_change_locked_flags(struct mount *mnt, unsigned int mnt_flags) 2515 { 2516 unsigned int fl = mnt->mnt.mnt_flags; 2517 2518 if ((fl & MNT_LOCK_READONLY) && 2519 !(mnt_flags & MNT_READONLY)) 2520 return false; 2521 2522 if ((fl & MNT_LOCK_NODEV) && 2523 !(mnt_flags & MNT_NODEV)) 2524 return false; 2525 2526 if ((fl & MNT_LOCK_NOSUID) && 2527 !(mnt_flags & MNT_NOSUID)) 2528 return false; 2529 2530 if ((fl & MNT_LOCK_NOEXEC) && 2531 !(mnt_flags & MNT_NOEXEC)) 2532 return false; 2533 2534 if ((fl & MNT_LOCK_ATIME) && 2535 ((fl & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK))) 2536 return false; 2537 2538 return true; 2539 } 2540 2541 static int change_mount_ro_state(struct mount *mnt, unsigned int mnt_flags) 2542 { 2543 bool readonly_request = (mnt_flags & MNT_READONLY); 2544 2545 if (readonly_request == __mnt_is_readonly(&mnt->mnt)) 2546 return 0; 2547 2548 if (readonly_request) 2549 return mnt_make_readonly(mnt); 2550 2551 mnt->mnt.mnt_flags &= ~MNT_READONLY; 2552 return 0; 2553 } 2554 2555 static void set_mount_attributes(struct mount *mnt, unsigned int mnt_flags) 2556 { 2557 mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK; 2558 mnt->mnt.mnt_flags = mnt_flags; 2559 touch_mnt_namespace(mnt->mnt_ns); 2560 } 2561 2562 static void mnt_warn_timestamp_expiry(struct path *mountpoint, struct vfsmount *mnt) 2563 { 2564 struct super_block *sb = mnt->mnt_sb; 2565 2566 if (!__mnt_is_readonly(mnt) && 2567 (ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX > sb->s_time_max)) { 2568 char *buf = (char *)__get_free_page(GFP_KERNEL); 2569 char *mntpath = buf ? d_path(mountpoint, buf, PAGE_SIZE) : ERR_PTR(-ENOMEM); 2570 struct tm tm; 2571 2572 time64_to_tm(sb->s_time_max, 0, &tm); 2573 2574 pr_warn("%s filesystem being %s at %s supports timestamps until %04ld (0x%llx)\n", 2575 sb->s_type->name, 2576 is_mounted(mnt) ? "remounted" : "mounted", 2577 mntpath, 2578 tm.tm_year+1900, (unsigned long long)sb->s_time_max); 2579 2580 free_page((unsigned long)buf); 2581 } 2582 } 2583 2584 /* 2585 * Handle reconfiguration of the mountpoint only without alteration of the 2586 * superblock it refers to. This is triggered by specifying MS_REMOUNT|MS_BIND 2587 * to mount(2). 2588 */ 2589 static int do_reconfigure_mnt(struct path *path, unsigned int mnt_flags) 2590 { 2591 struct super_block *sb = path->mnt->mnt_sb; 2592 struct mount *mnt = real_mount(path->mnt); 2593 int ret; 2594 2595 if (!check_mnt(mnt)) 2596 return -EINVAL; 2597 2598 if (path->dentry != mnt->mnt.mnt_root) 2599 return -EINVAL; 2600 2601 if (!can_change_locked_flags(mnt, mnt_flags)) 2602 return -EPERM; 2603 2604 /* 2605 * We're only checking whether the superblock is read-only not 2606 * changing it, so only take down_read(&sb->s_umount). 2607 */ 2608 down_read(&sb->s_umount); 2609 lock_mount_hash(); 2610 ret = change_mount_ro_state(mnt, mnt_flags); 2611 if (ret == 0) 2612 set_mount_attributes(mnt, mnt_flags); 2613 unlock_mount_hash(); 2614 up_read(&sb->s_umount); 2615 2616 mnt_warn_timestamp_expiry(path, &mnt->mnt); 2617 2618 return ret; 2619 } 2620 2621 /* 2622 * change filesystem flags. dir should be a physical root of filesystem. 2623 * If you've mounted a non-root directory somewhere and want to do remount 2624 * on it - tough luck. 2625 */ 2626 static int do_remount(struct path *path, int ms_flags, int sb_flags, 2627 int mnt_flags, void *data) 2628 { 2629 int err; 2630 struct super_block *sb = path->mnt->mnt_sb; 2631 struct mount *mnt = real_mount(path->mnt); 2632 struct fs_context *fc; 2633 2634 if (!check_mnt(mnt)) 2635 return -EINVAL; 2636 2637 if (path->dentry != path->mnt->mnt_root) 2638 return -EINVAL; 2639 2640 if (!can_change_locked_flags(mnt, mnt_flags)) 2641 return -EPERM; 2642 2643 fc = fs_context_for_reconfigure(path->dentry, sb_flags, MS_RMT_MASK); 2644 if (IS_ERR(fc)) 2645 return PTR_ERR(fc); 2646 2647 fc->oldapi = true; 2648 err = parse_monolithic_mount_data(fc, data); 2649 if (!err) { 2650 down_write(&sb->s_umount); 2651 err = -EPERM; 2652 if (ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) { 2653 err = reconfigure_super(fc); 2654 if (!err) { 2655 lock_mount_hash(); 2656 set_mount_attributes(mnt, mnt_flags); 2657 unlock_mount_hash(); 2658 } 2659 } 2660 up_write(&sb->s_umount); 2661 } 2662 2663 mnt_warn_timestamp_expiry(path, &mnt->mnt); 2664 2665 put_fs_context(fc); 2666 return err; 2667 } 2668 2669 static inline int tree_contains_unbindable(struct mount *mnt) 2670 { 2671 struct mount *p; 2672 for (p = mnt; p; p = next_mnt(p, mnt)) { 2673 if (IS_MNT_UNBINDABLE(p)) 2674 return 1; 2675 } 2676 return 0; 2677 } 2678 2679 /* 2680 * Check that there aren't references to earlier/same mount namespaces in the 2681 * specified subtree. Such references can act as pins for mount namespaces 2682 * that aren't checked by the mount-cycle checking code, thereby allowing 2683 * cycles to be made. 2684 */ 2685 static bool check_for_nsfs_mounts(struct mount *subtree) 2686 { 2687 struct mount *p; 2688 bool ret = false; 2689 2690 lock_mount_hash(); 2691 for (p = subtree; p; p = next_mnt(p, subtree)) 2692 if (mnt_ns_loop(p->mnt.mnt_root)) 2693 goto out; 2694 2695 ret = true; 2696 out: 2697 unlock_mount_hash(); 2698 return ret; 2699 } 2700 2701 static int do_move_mount(struct path *old_path, struct path *new_path) 2702 { 2703 struct mnt_namespace *ns; 2704 struct mount *p; 2705 struct mount *old; 2706 struct mount *parent; 2707 struct mountpoint *mp, *old_mp; 2708 int err; 2709 bool attached; 2710 2711 mp = lock_mount(new_path); 2712 if (IS_ERR(mp)) 2713 return PTR_ERR(mp); 2714 2715 old = real_mount(old_path->mnt); 2716 p = real_mount(new_path->mnt); 2717 parent = old->mnt_parent; 2718 attached = mnt_has_parent(old); 2719 old_mp = old->mnt_mp; 2720 ns = old->mnt_ns; 2721 2722 err = -EINVAL; 2723 /* The mountpoint must be in our namespace. */ 2724 if (!check_mnt(p)) 2725 goto out; 2726 2727 /* The thing moved must be mounted... */ 2728 if (!is_mounted(&old->mnt)) 2729 goto out; 2730 2731 /* ... and either ours or the root of anon namespace */ 2732 if (!(attached ? check_mnt(old) : is_anon_ns(ns))) 2733 goto out; 2734 2735 if (old->mnt.mnt_flags & MNT_LOCKED) 2736 goto out; 2737 2738 if (old_path->dentry != old_path->mnt->mnt_root) 2739 goto out; 2740 2741 if (d_is_dir(new_path->dentry) != 2742 d_is_dir(old_path->dentry)) 2743 goto out; 2744 /* 2745 * Don't move a mount residing in a shared parent. 2746 */ 2747 if (attached && IS_MNT_SHARED(parent)) 2748 goto out; 2749 /* 2750 * Don't move a mount tree containing unbindable mounts to a destination 2751 * mount which is shared. 2752 */ 2753 if (IS_MNT_SHARED(p) && tree_contains_unbindable(old)) 2754 goto out; 2755 err = -ELOOP; 2756 if (!check_for_nsfs_mounts(old)) 2757 goto out; 2758 for (; mnt_has_parent(p); p = p->mnt_parent) 2759 if (p == old) 2760 goto out; 2761 2762 err = attach_recursive_mnt(old, real_mount(new_path->mnt), mp, 2763 attached); 2764 if (err) 2765 goto out; 2766 2767 /* if the mount is moved, it should no longer be expire 2768 * automatically */ 2769 list_del_init(&old->mnt_expire); 2770 if (attached) 2771 put_mountpoint(old_mp); 2772 out: 2773 unlock_mount(mp); 2774 if (!err) { 2775 if (attached) 2776 mntput_no_expire(parent); 2777 else 2778 free_mnt_ns(ns); 2779 } 2780 return err; 2781 } 2782 2783 static int do_move_mount_old(struct path *path, const char *old_name) 2784 { 2785 struct path old_path; 2786 int err; 2787 2788 if (!old_name || !*old_name) 2789 return -EINVAL; 2790 2791 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); 2792 if (err) 2793 return err; 2794 2795 err = do_move_mount(&old_path, path); 2796 path_put(&old_path); 2797 return err; 2798 } 2799 2800 /* 2801 * add a mount into a namespace's mount tree 2802 */ 2803 static int do_add_mount(struct mount *newmnt, struct mountpoint *mp, 2804 struct path *path, int mnt_flags) 2805 { 2806 struct mount *parent = real_mount(path->mnt); 2807 2808 mnt_flags &= ~MNT_INTERNAL_FLAGS; 2809 2810 if (unlikely(!check_mnt(parent))) { 2811 /* that's acceptable only for automounts done in private ns */ 2812 if (!(mnt_flags & MNT_SHRINKABLE)) 2813 return -EINVAL; 2814 /* ... and for those we'd better have mountpoint still alive */ 2815 if (!parent->mnt_ns) 2816 return -EINVAL; 2817 } 2818 2819 /* Refuse the same filesystem on the same mount point */ 2820 if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && 2821 path->mnt->mnt_root == path->dentry) 2822 return -EBUSY; 2823 2824 if (d_is_symlink(newmnt->mnt.mnt_root)) 2825 return -EINVAL; 2826 2827 newmnt->mnt.mnt_flags = mnt_flags; 2828 return graft_tree(newmnt, parent, mp); 2829 } 2830 2831 static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags); 2832 2833 /* 2834 * Create a new mount using a superblock configuration and request it 2835 * be added to the namespace tree. 2836 */ 2837 static int do_new_mount_fc(struct fs_context *fc, struct path *mountpoint, 2838 unsigned int mnt_flags) 2839 { 2840 struct vfsmount *mnt; 2841 struct mountpoint *mp; 2842 struct super_block *sb = fc->root->d_sb; 2843 int error; 2844 2845 error = security_sb_kern_mount(sb); 2846 if (!error && mount_too_revealing(sb, &mnt_flags)) 2847 error = -EPERM; 2848 2849 if (unlikely(error)) { 2850 fc_drop_locked(fc); 2851 return error; 2852 } 2853 2854 up_write(&sb->s_umount); 2855 2856 mnt = vfs_create_mount(fc); 2857 if (IS_ERR(mnt)) 2858 return PTR_ERR(mnt); 2859 2860 mnt_warn_timestamp_expiry(mountpoint, mnt); 2861 2862 mp = lock_mount(mountpoint); 2863 if (IS_ERR(mp)) { 2864 mntput(mnt); 2865 return PTR_ERR(mp); 2866 } 2867 error = do_add_mount(real_mount(mnt), mp, mountpoint, mnt_flags); 2868 unlock_mount(mp); 2869 if (error < 0) 2870 mntput(mnt); 2871 return error; 2872 } 2873 2874 /* 2875 * create a new mount for userspace and request it to be added into the 2876 * namespace's tree 2877 */ 2878 static int do_new_mount(struct path *path, const char *fstype, int sb_flags, 2879 int mnt_flags, const char *name, void *data) 2880 { 2881 struct file_system_type *type; 2882 struct fs_context *fc; 2883 const char *subtype = NULL; 2884 int err = 0; 2885 2886 if (!fstype) 2887 return -EINVAL; 2888 2889 type = get_fs_type(fstype); 2890 if (!type) 2891 return -ENODEV; 2892 2893 if (type->fs_flags & FS_HAS_SUBTYPE) { 2894 subtype = strchr(fstype, '.'); 2895 if (subtype) { 2896 subtype++; 2897 if (!*subtype) { 2898 put_filesystem(type); 2899 return -EINVAL; 2900 } 2901 } 2902 } 2903 2904 fc = fs_context_for_mount(type, sb_flags); 2905 put_filesystem(type); 2906 if (IS_ERR(fc)) 2907 return PTR_ERR(fc); 2908 2909 if (subtype) 2910 err = vfs_parse_fs_string(fc, "subtype", 2911 subtype, strlen(subtype)); 2912 if (!err && name) 2913 err = vfs_parse_fs_string(fc, "source", name, strlen(name)); 2914 if (!err) 2915 err = parse_monolithic_mount_data(fc, data); 2916 if (!err && !mount_capable(fc)) 2917 err = -EPERM; 2918 if (!err) 2919 err = vfs_get_tree(fc); 2920 if (!err) 2921 err = do_new_mount_fc(fc, path, mnt_flags); 2922 2923 put_fs_context(fc); 2924 return err; 2925 } 2926 2927 int finish_automount(struct vfsmount *m, struct path *path) 2928 { 2929 struct dentry *dentry = path->dentry; 2930 struct mountpoint *mp; 2931 struct mount *mnt; 2932 int err; 2933 2934 if (!m) 2935 return 0; 2936 if (IS_ERR(m)) 2937 return PTR_ERR(m); 2938 2939 mnt = real_mount(m); 2940 /* The new mount record should have at least 2 refs to prevent it being 2941 * expired before we get a chance to add it 2942 */ 2943 BUG_ON(mnt_get_count(mnt) < 2); 2944 2945 if (m->mnt_sb == path->mnt->mnt_sb && 2946 m->mnt_root == dentry) { 2947 err = -ELOOP; 2948 goto discard; 2949 } 2950 2951 /* 2952 * we don't want to use lock_mount() - in this case finding something 2953 * that overmounts our mountpoint to be means "quitely drop what we've 2954 * got", not "try to mount it on top". 2955 */ 2956 inode_lock(dentry->d_inode); 2957 namespace_lock(); 2958 if (unlikely(cant_mount(dentry))) { 2959 err = -ENOENT; 2960 goto discard_locked; 2961 } 2962 rcu_read_lock(); 2963 if (unlikely(__lookup_mnt(path->mnt, dentry))) { 2964 rcu_read_unlock(); 2965 err = 0; 2966 goto discard_locked; 2967 } 2968 rcu_read_unlock(); 2969 mp = get_mountpoint(dentry); 2970 if (IS_ERR(mp)) { 2971 err = PTR_ERR(mp); 2972 goto discard_locked; 2973 } 2974 2975 err = do_add_mount(mnt, mp, path, path->mnt->mnt_flags | MNT_SHRINKABLE); 2976 unlock_mount(mp); 2977 if (unlikely(err)) 2978 goto discard; 2979 mntput(m); 2980 return 0; 2981 2982 discard_locked: 2983 namespace_unlock(); 2984 inode_unlock(dentry->d_inode); 2985 discard: 2986 /* remove m from any expiration list it may be on */ 2987 if (!list_empty(&mnt->mnt_expire)) { 2988 namespace_lock(); 2989 list_del_init(&mnt->mnt_expire); 2990 namespace_unlock(); 2991 } 2992 mntput(m); 2993 mntput(m); 2994 return err; 2995 } 2996 2997 /** 2998 * mnt_set_expiry - Put a mount on an expiration list 2999 * @mnt: The mount to list. 3000 * @expiry_list: The list to add the mount to. 3001 */ 3002 void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list) 3003 { 3004 namespace_lock(); 3005 3006 list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list); 3007 3008 namespace_unlock(); 3009 } 3010 EXPORT_SYMBOL(mnt_set_expiry); 3011 3012 /* 3013 * process a list of expirable mountpoints with the intent of discarding any 3014 * mountpoints that aren't in use and haven't been touched since last we came 3015 * here 3016 */ 3017 void mark_mounts_for_expiry(struct list_head *mounts) 3018 { 3019 struct mount *mnt, *next; 3020 LIST_HEAD(graveyard); 3021 3022 if (list_empty(mounts)) 3023 return; 3024 3025 namespace_lock(); 3026 lock_mount_hash(); 3027 3028 /* extract from the expiration list every vfsmount that matches the 3029 * following criteria: 3030 * - only referenced by its parent vfsmount 3031 * - still marked for expiry (marked on the last call here; marks are 3032 * cleared by mntput()) 3033 */ 3034 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { 3035 if (!xchg(&mnt->mnt_expiry_mark, 1) || 3036 propagate_mount_busy(mnt, 1)) 3037 continue; 3038 list_move(&mnt->mnt_expire, &graveyard); 3039 } 3040 while (!list_empty(&graveyard)) { 3041 mnt = list_first_entry(&graveyard, struct mount, mnt_expire); 3042 touch_mnt_namespace(mnt->mnt_ns); 3043 umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC); 3044 } 3045 unlock_mount_hash(); 3046 namespace_unlock(); 3047 } 3048 3049 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); 3050 3051 /* 3052 * Ripoff of 'select_parent()' 3053 * 3054 * search the list of submounts for a given mountpoint, and move any 3055 * shrinkable submounts to the 'graveyard' list. 3056 */ 3057 static int select_submounts(struct mount *parent, struct list_head *graveyard) 3058 { 3059 struct mount *this_parent = parent; 3060 struct list_head *next; 3061 int found = 0; 3062 3063 repeat: 3064 next = this_parent->mnt_mounts.next; 3065 resume: 3066 while (next != &this_parent->mnt_mounts) { 3067 struct list_head *tmp = next; 3068 struct mount *mnt = list_entry(tmp, struct mount, mnt_child); 3069 3070 next = tmp->next; 3071 if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE)) 3072 continue; 3073 /* 3074 * Descend a level if the d_mounts list is non-empty. 3075 */ 3076 if (!list_empty(&mnt->mnt_mounts)) { 3077 this_parent = mnt; 3078 goto repeat; 3079 } 3080 3081 if (!propagate_mount_busy(mnt, 1)) { 3082 list_move_tail(&mnt->mnt_expire, graveyard); 3083 found++; 3084 } 3085 } 3086 /* 3087 * All done at this level ... ascend and resume the search 3088 */ 3089 if (this_parent != parent) { 3090 next = this_parent->mnt_child.next; 3091 this_parent = this_parent->mnt_parent; 3092 goto resume; 3093 } 3094 return found; 3095 } 3096 3097 /* 3098 * process a list of expirable mountpoints with the intent of discarding any 3099 * submounts of a specific parent mountpoint 3100 * 3101 * mount_lock must be held for write 3102 */ 3103 static void shrink_submounts(struct mount *mnt) 3104 { 3105 LIST_HEAD(graveyard); 3106 struct mount *m; 3107 3108 /* extract submounts of 'mountpoint' from the expiration list */ 3109 while (select_submounts(mnt, &graveyard)) { 3110 while (!list_empty(&graveyard)) { 3111 m = list_first_entry(&graveyard, struct mount, 3112 mnt_expire); 3113 touch_mnt_namespace(m->mnt_ns); 3114 umount_tree(m, UMOUNT_PROPAGATE|UMOUNT_SYNC); 3115 } 3116 } 3117 } 3118 3119 static void *copy_mount_options(const void __user * data) 3120 { 3121 char *copy; 3122 unsigned left, offset; 3123 3124 if (!data) 3125 return NULL; 3126 3127 copy = kmalloc(PAGE_SIZE, GFP_KERNEL); 3128 if (!copy) 3129 return ERR_PTR(-ENOMEM); 3130 3131 left = copy_from_user(copy, data, PAGE_SIZE); 3132 3133 /* 3134 * Not all architectures have an exact copy_from_user(). Resort to 3135 * byte at a time. 3136 */ 3137 offset = PAGE_SIZE - left; 3138 while (left) { 3139 char c; 3140 if (get_user(c, (const char __user *)data + offset)) 3141 break; 3142 copy[offset] = c; 3143 left--; 3144 offset++; 3145 } 3146 3147 if (left == PAGE_SIZE) { 3148 kfree(copy); 3149 return ERR_PTR(-EFAULT); 3150 } 3151 3152 return copy; 3153 } 3154 3155 static char *copy_mount_string(const void __user *data) 3156 { 3157 return data ? strndup_user(data, PATH_MAX) : NULL; 3158 } 3159 3160 /* 3161 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to 3162 * be given to the mount() call (ie: read-only, no-dev, no-suid etc). 3163 * 3164 * data is a (void *) that can point to any structure up to 3165 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent 3166 * information (or be NULL). 3167 * 3168 * Pre-0.97 versions of mount() didn't have a flags word. 3169 * When the flags word was introduced its top half was required 3170 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. 3171 * Therefore, if this magic number is present, it carries no information 3172 * and must be discarded. 3173 */ 3174 int path_mount(const char *dev_name, struct path *path, 3175 const char *type_page, unsigned long flags, void *data_page) 3176 { 3177 unsigned int mnt_flags = 0, sb_flags; 3178 int ret; 3179 3180 /* Discard magic */ 3181 if ((flags & MS_MGC_MSK) == MS_MGC_VAL) 3182 flags &= ~MS_MGC_MSK; 3183 3184 /* Basic sanity checks */ 3185 if (data_page) 3186 ((char *)data_page)[PAGE_SIZE - 1] = 0; 3187 3188 if (flags & MS_NOUSER) 3189 return -EINVAL; 3190 3191 ret = security_sb_mount(dev_name, path, type_page, flags, data_page); 3192 if (ret) 3193 return ret; 3194 if (!may_mount()) 3195 return -EPERM; 3196 if ((flags & SB_MANDLOCK) && !may_mandlock()) 3197 return -EPERM; 3198 3199 /* Default to relatime unless overriden */ 3200 if (!(flags & MS_NOATIME)) 3201 mnt_flags |= MNT_RELATIME; 3202 3203 /* Separate the per-mountpoint flags */ 3204 if (flags & MS_NOSUID) 3205 mnt_flags |= MNT_NOSUID; 3206 if (flags & MS_NODEV) 3207 mnt_flags |= MNT_NODEV; 3208 if (flags & MS_NOEXEC) 3209 mnt_flags |= MNT_NOEXEC; 3210 if (flags & MS_NOATIME) 3211 mnt_flags |= MNT_NOATIME; 3212 if (flags & MS_NODIRATIME) 3213 mnt_flags |= MNT_NODIRATIME; 3214 if (flags & MS_STRICTATIME) 3215 mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); 3216 if (flags & MS_RDONLY) 3217 mnt_flags |= MNT_READONLY; 3218 if (flags & MS_NOSYMFOLLOW) 3219 mnt_flags |= MNT_NOSYMFOLLOW; 3220 3221 /* The default atime for remount is preservation */ 3222 if ((flags & MS_REMOUNT) && 3223 ((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME | 3224 MS_STRICTATIME)) == 0)) { 3225 mnt_flags &= ~MNT_ATIME_MASK; 3226 mnt_flags |= path->mnt->mnt_flags & MNT_ATIME_MASK; 3227 } 3228 3229 sb_flags = flags & (SB_RDONLY | 3230 SB_SYNCHRONOUS | 3231 SB_MANDLOCK | 3232 SB_DIRSYNC | 3233 SB_SILENT | 3234 SB_POSIXACL | 3235 SB_LAZYTIME | 3236 SB_I_VERSION); 3237 3238 if ((flags & (MS_REMOUNT | MS_BIND)) == (MS_REMOUNT | MS_BIND)) 3239 return do_reconfigure_mnt(path, mnt_flags); 3240 if (flags & MS_REMOUNT) 3241 return do_remount(path, flags, sb_flags, mnt_flags, data_page); 3242 if (flags & MS_BIND) 3243 return do_loopback(path, dev_name, flags & MS_REC); 3244 if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) 3245 return do_change_type(path, flags); 3246 if (flags & MS_MOVE) 3247 return do_move_mount_old(path, dev_name); 3248 3249 return do_new_mount(path, type_page, sb_flags, mnt_flags, dev_name, 3250 data_page); 3251 } 3252 3253 long do_mount(const char *dev_name, const char __user *dir_name, 3254 const char *type_page, unsigned long flags, void *data_page) 3255 { 3256 struct path path; 3257 int ret; 3258 3259 ret = user_path_at(AT_FDCWD, dir_name, LOOKUP_FOLLOW, &path); 3260 if (ret) 3261 return ret; 3262 ret = path_mount(dev_name, &path, type_page, flags, data_page); 3263 path_put(&path); 3264 return ret; 3265 } 3266 3267 static struct ucounts *inc_mnt_namespaces(struct user_namespace *ns) 3268 { 3269 return inc_ucount(ns, current_euid(), UCOUNT_MNT_NAMESPACES); 3270 } 3271 3272 static void dec_mnt_namespaces(struct ucounts *ucounts) 3273 { 3274 dec_ucount(ucounts, UCOUNT_MNT_NAMESPACES); 3275 } 3276 3277 static void free_mnt_ns(struct mnt_namespace *ns) 3278 { 3279 if (!is_anon_ns(ns)) 3280 ns_free_inum(&ns->ns); 3281 dec_mnt_namespaces(ns->ucounts); 3282 put_user_ns(ns->user_ns); 3283 kfree(ns); 3284 } 3285 3286 /* 3287 * Assign a sequence number so we can detect when we attempt to bind 3288 * mount a reference to an older mount namespace into the current 3289 * mount namespace, preventing reference counting loops. A 64bit 3290 * number incrementing at 10Ghz will take 12,427 years to wrap which 3291 * is effectively never, so we can ignore the possibility. 3292 */ 3293 static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1); 3294 3295 static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool anon) 3296 { 3297 struct mnt_namespace *new_ns; 3298 struct ucounts *ucounts; 3299 int ret; 3300 3301 ucounts = inc_mnt_namespaces(user_ns); 3302 if (!ucounts) 3303 return ERR_PTR(-ENOSPC); 3304 3305 new_ns = kzalloc(sizeof(struct mnt_namespace), GFP_KERNEL); 3306 if (!new_ns) { 3307 dec_mnt_namespaces(ucounts); 3308 return ERR_PTR(-ENOMEM); 3309 } 3310 if (!anon) { 3311 ret = ns_alloc_inum(&new_ns->ns); 3312 if (ret) { 3313 kfree(new_ns); 3314 dec_mnt_namespaces(ucounts); 3315 return ERR_PTR(ret); 3316 } 3317 } 3318 new_ns->ns.ops = &mntns_operations; 3319 if (!anon) 3320 new_ns->seq = atomic64_add_return(1, &mnt_ns_seq); 3321 refcount_set(&new_ns->ns.count, 1); 3322 INIT_LIST_HEAD(&new_ns->list); 3323 init_waitqueue_head(&new_ns->poll); 3324 spin_lock_init(&new_ns->ns_lock); 3325 new_ns->user_ns = get_user_ns(user_ns); 3326 new_ns->ucounts = ucounts; 3327 return new_ns; 3328 } 3329 3330 __latent_entropy 3331 struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, 3332 struct user_namespace *user_ns, struct fs_struct *new_fs) 3333 { 3334 struct mnt_namespace *new_ns; 3335 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; 3336 struct mount *p, *q; 3337 struct mount *old; 3338 struct mount *new; 3339 int copy_flags; 3340 3341 BUG_ON(!ns); 3342 3343 if (likely(!(flags & CLONE_NEWNS))) { 3344 get_mnt_ns(ns); 3345 return ns; 3346 } 3347 3348 old = ns->root; 3349 3350 new_ns = alloc_mnt_ns(user_ns, false); 3351 if (IS_ERR(new_ns)) 3352 return new_ns; 3353 3354 namespace_lock(); 3355 /* First pass: copy the tree topology */ 3356 copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE; 3357 if (user_ns != ns->user_ns) 3358 copy_flags |= CL_SHARED_TO_SLAVE; 3359 new = copy_tree(old, old->mnt.mnt_root, copy_flags); 3360 if (IS_ERR(new)) { 3361 namespace_unlock(); 3362 free_mnt_ns(new_ns); 3363 return ERR_CAST(new); 3364 } 3365 if (user_ns != ns->user_ns) { 3366 lock_mount_hash(); 3367 lock_mnt_tree(new); 3368 unlock_mount_hash(); 3369 } 3370 new_ns->root = new; 3371 list_add_tail(&new_ns->list, &new->mnt_list); 3372 3373 /* 3374 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts 3375 * as belonging to new namespace. We have already acquired a private 3376 * fs_struct, so tsk->fs->lock is not needed. 3377 */ 3378 p = old; 3379 q = new; 3380 while (p) { 3381 q->mnt_ns = new_ns; 3382 new_ns->mounts++; 3383 if (new_fs) { 3384 if (&p->mnt == new_fs->root.mnt) { 3385 new_fs->root.mnt = mntget(&q->mnt); 3386 rootmnt = &p->mnt; 3387 } 3388 if (&p->mnt == new_fs->pwd.mnt) { 3389 new_fs->pwd.mnt = mntget(&q->mnt); 3390 pwdmnt = &p->mnt; 3391 } 3392 } 3393 p = next_mnt(p, old); 3394 q = next_mnt(q, new); 3395 if (!q) 3396 break; 3397 while (p->mnt.mnt_root != q->mnt.mnt_root) 3398 p = next_mnt(p, old); 3399 } 3400 namespace_unlock(); 3401 3402 if (rootmnt) 3403 mntput(rootmnt); 3404 if (pwdmnt) 3405 mntput(pwdmnt); 3406 3407 return new_ns; 3408 } 3409 3410 struct dentry *mount_subtree(struct vfsmount *m, const char *name) 3411 { 3412 struct mount *mnt = real_mount(m); 3413 struct mnt_namespace *ns; 3414 struct super_block *s; 3415 struct path path; 3416 int err; 3417 3418 ns = alloc_mnt_ns(&init_user_ns, true); 3419 if (IS_ERR(ns)) { 3420 mntput(m); 3421 return ERR_CAST(ns); 3422 } 3423 mnt->mnt_ns = ns; 3424 ns->root = mnt; 3425 ns->mounts++; 3426 list_add(&mnt->mnt_list, &ns->list); 3427 3428 err = vfs_path_lookup(m->mnt_root, m, 3429 name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); 3430 3431 put_mnt_ns(ns); 3432 3433 if (err) 3434 return ERR_PTR(err); 3435 3436 /* trade a vfsmount reference for active sb one */ 3437 s = path.mnt->mnt_sb; 3438 atomic_inc(&s->s_active); 3439 mntput(path.mnt); 3440 /* lock the sucker */ 3441 down_write(&s->s_umount); 3442 /* ... and return the root of (sub)tree on it */ 3443 return path.dentry; 3444 } 3445 EXPORT_SYMBOL(mount_subtree); 3446 3447 SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, 3448 char __user *, type, unsigned long, flags, void __user *, data) 3449 { 3450 int ret; 3451 char *kernel_type; 3452 char *kernel_dev; 3453 void *options; 3454 3455 kernel_type = copy_mount_string(type); 3456 ret = PTR_ERR(kernel_type); 3457 if (IS_ERR(kernel_type)) 3458 goto out_type; 3459 3460 kernel_dev = copy_mount_string(dev_name); 3461 ret = PTR_ERR(kernel_dev); 3462 if (IS_ERR(kernel_dev)) 3463 goto out_dev; 3464 3465 options = copy_mount_options(data); 3466 ret = PTR_ERR(options); 3467 if (IS_ERR(options)) 3468 goto out_data; 3469 3470 ret = do_mount(kernel_dev, dir_name, kernel_type, flags, options); 3471 3472 kfree(options); 3473 out_data: 3474 kfree(kernel_dev); 3475 out_dev: 3476 kfree(kernel_type); 3477 out_type: 3478 return ret; 3479 } 3480 3481 #define FSMOUNT_VALID_FLAGS \ 3482 (MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \ 3483 MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME | \ 3484 MOUNT_ATTR_NOSYMFOLLOW) 3485 3486 #define MOUNT_SETATTR_VALID_FLAGS (FSMOUNT_VALID_FLAGS | MOUNT_ATTR_IDMAP) 3487 3488 #define MOUNT_SETATTR_PROPAGATION_FLAGS \ 3489 (MS_UNBINDABLE | MS_PRIVATE | MS_SLAVE | MS_SHARED) 3490 3491 static unsigned int attr_flags_to_mnt_flags(u64 attr_flags) 3492 { 3493 unsigned int mnt_flags = 0; 3494 3495 if (attr_flags & MOUNT_ATTR_RDONLY) 3496 mnt_flags |= MNT_READONLY; 3497 if (attr_flags & MOUNT_ATTR_NOSUID) 3498 mnt_flags |= MNT_NOSUID; 3499 if (attr_flags & MOUNT_ATTR_NODEV) 3500 mnt_flags |= MNT_NODEV; 3501 if (attr_flags & MOUNT_ATTR_NOEXEC) 3502 mnt_flags |= MNT_NOEXEC; 3503 if (attr_flags & MOUNT_ATTR_NODIRATIME) 3504 mnt_flags |= MNT_NODIRATIME; 3505 if (attr_flags & MOUNT_ATTR_NOSYMFOLLOW) 3506 mnt_flags |= MNT_NOSYMFOLLOW; 3507 3508 return mnt_flags; 3509 } 3510 3511 /* 3512 * Create a kernel mount representation for a new, prepared superblock 3513 * (specified by fs_fd) and attach to an open_tree-like file descriptor. 3514 */ 3515 SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags, 3516 unsigned int, attr_flags) 3517 { 3518 struct mnt_namespace *ns; 3519 struct fs_context *fc; 3520 struct file *file; 3521 struct path newmount; 3522 struct mount *mnt; 3523 struct fd f; 3524 unsigned int mnt_flags = 0; 3525 long ret; 3526 3527 if (!may_mount()) 3528 return -EPERM; 3529 3530 if ((flags & ~(FSMOUNT_CLOEXEC)) != 0) 3531 return -EINVAL; 3532 3533 if (attr_flags & ~FSMOUNT_VALID_FLAGS) 3534 return -EINVAL; 3535 3536 mnt_flags = attr_flags_to_mnt_flags(attr_flags); 3537 3538 switch (attr_flags & MOUNT_ATTR__ATIME) { 3539 case MOUNT_ATTR_STRICTATIME: 3540 break; 3541 case MOUNT_ATTR_NOATIME: 3542 mnt_flags |= MNT_NOATIME; 3543 break; 3544 case MOUNT_ATTR_RELATIME: 3545 mnt_flags |= MNT_RELATIME; 3546 break; 3547 default: 3548 return -EINVAL; 3549 } 3550 3551 f = fdget(fs_fd); 3552 if (!f.file) 3553 return -EBADF; 3554 3555 ret = -EINVAL; 3556 if (f.file->f_op != &fscontext_fops) 3557 goto err_fsfd; 3558 3559 fc = f.file->private_data; 3560 3561 ret = mutex_lock_interruptible(&fc->uapi_mutex); 3562 if (ret < 0) 3563 goto err_fsfd; 3564 3565 /* There must be a valid superblock or we can't mount it */ 3566 ret = -EINVAL; 3567 if (!fc->root) 3568 goto err_unlock; 3569 3570 ret = -EPERM; 3571 if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) { 3572 pr_warn("VFS: Mount too revealing\n"); 3573 goto err_unlock; 3574 } 3575 3576 ret = -EBUSY; 3577 if (fc->phase != FS_CONTEXT_AWAITING_MOUNT) 3578 goto err_unlock; 3579 3580 ret = -EPERM; 3581 if ((fc->sb_flags & SB_MANDLOCK) && !may_mandlock()) 3582 goto err_unlock; 3583 3584 newmount.mnt = vfs_create_mount(fc); 3585 if (IS_ERR(newmount.mnt)) { 3586 ret = PTR_ERR(newmount.mnt); 3587 goto err_unlock; 3588 } 3589 newmount.dentry = dget(fc->root); 3590 newmount.mnt->mnt_flags = mnt_flags; 3591 3592 /* We've done the mount bit - now move the file context into more or 3593 * less the same state as if we'd done an fspick(). We don't want to 3594 * do any memory allocation or anything like that at this point as we 3595 * don't want to have to handle any errors incurred. 3596 */ 3597 vfs_clean_context(fc); 3598 3599 ns = alloc_mnt_ns(current->nsproxy->mnt_ns->user_ns, true); 3600 if (IS_ERR(ns)) { 3601 ret = PTR_ERR(ns); 3602 goto err_path; 3603 } 3604 mnt = real_mount(newmount.mnt); 3605 mnt->mnt_ns = ns; 3606 ns->root = mnt; 3607 ns->mounts = 1; 3608 list_add(&mnt->mnt_list, &ns->list); 3609 mntget(newmount.mnt); 3610 3611 /* Attach to an apparent O_PATH fd with a note that we need to unmount 3612 * it, not just simply put it. 3613 */ 3614 file = dentry_open(&newmount, O_PATH, fc->cred); 3615 if (IS_ERR(file)) { 3616 dissolve_on_fput(newmount.mnt); 3617 ret = PTR_ERR(file); 3618 goto err_path; 3619 } 3620 file->f_mode |= FMODE_NEED_UNMOUNT; 3621 3622 ret = get_unused_fd_flags((flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0); 3623 if (ret >= 0) 3624 fd_install(ret, file); 3625 else 3626 fput(file); 3627 3628 err_path: 3629 path_put(&newmount); 3630 err_unlock: 3631 mutex_unlock(&fc->uapi_mutex); 3632 err_fsfd: 3633 fdput(f); 3634 return ret; 3635 } 3636 3637 /* 3638 * Move a mount from one place to another. In combination with 3639 * fsopen()/fsmount() this is used to install a new mount and in combination 3640 * with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy 3641 * a mount subtree. 3642 * 3643 * Note the flags value is a combination of MOVE_MOUNT_* flags. 3644 */ 3645 SYSCALL_DEFINE5(move_mount, 3646 int, from_dfd, const char __user *, from_pathname, 3647 int, to_dfd, const char __user *, to_pathname, 3648 unsigned int, flags) 3649 { 3650 struct path from_path, to_path; 3651 unsigned int lflags; 3652 int ret = 0; 3653 3654 if (!may_mount()) 3655 return -EPERM; 3656 3657 if (flags & ~MOVE_MOUNT__MASK) 3658 return -EINVAL; 3659 3660 /* If someone gives a pathname, they aren't permitted to move 3661 * from an fd that requires unmount as we can't get at the flag 3662 * to clear it afterwards. 3663 */ 3664 lflags = 0; 3665 if (flags & MOVE_MOUNT_F_SYMLINKS) lflags |= LOOKUP_FOLLOW; 3666 if (flags & MOVE_MOUNT_F_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT; 3667 if (flags & MOVE_MOUNT_F_EMPTY_PATH) lflags |= LOOKUP_EMPTY; 3668 3669 ret = user_path_at(from_dfd, from_pathname, lflags, &from_path); 3670 if (ret < 0) 3671 return ret; 3672 3673 lflags = 0; 3674 if (flags & MOVE_MOUNT_T_SYMLINKS) lflags |= LOOKUP_FOLLOW; 3675 if (flags & MOVE_MOUNT_T_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT; 3676 if (flags & MOVE_MOUNT_T_EMPTY_PATH) lflags |= LOOKUP_EMPTY; 3677 3678 ret = user_path_at(to_dfd, to_pathname, lflags, &to_path); 3679 if (ret < 0) 3680 goto out_from; 3681 3682 ret = security_move_mount(&from_path, &to_path); 3683 if (ret < 0) 3684 goto out_to; 3685 3686 ret = do_move_mount(&from_path, &to_path); 3687 3688 out_to: 3689 path_put(&to_path); 3690 out_from: 3691 path_put(&from_path); 3692 return ret; 3693 } 3694 3695 /* 3696 * Return true if path is reachable from root 3697 * 3698 * namespace_sem or mount_lock is held 3699 */ 3700 bool is_path_reachable(struct mount *mnt, struct dentry *dentry, 3701 const struct path *root) 3702 { 3703 while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) { 3704 dentry = mnt->mnt_mountpoint; 3705 mnt = mnt->mnt_parent; 3706 } 3707 return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry); 3708 } 3709 3710 bool path_is_under(const struct path *path1, const struct path *path2) 3711 { 3712 bool res; 3713 read_seqlock_excl(&mount_lock); 3714 res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2); 3715 read_sequnlock_excl(&mount_lock); 3716 return res; 3717 } 3718 EXPORT_SYMBOL(path_is_under); 3719 3720 /* 3721 * pivot_root Semantics: 3722 * Moves the root file system of the current process to the directory put_old, 3723 * makes new_root as the new root file system of the current process, and sets 3724 * root/cwd of all processes which had them on the current root to new_root. 3725 * 3726 * Restrictions: 3727 * The new_root and put_old must be directories, and must not be on the 3728 * same file system as the current process root. The put_old must be 3729 * underneath new_root, i.e. adding a non-zero number of /.. to the string 3730 * pointed to by put_old must yield the same directory as new_root. No other 3731 * file system may be mounted on put_old. After all, new_root is a mountpoint. 3732 * 3733 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. 3734 * See Documentation/filesystems/ramfs-rootfs-initramfs.rst for alternatives 3735 * in this situation. 3736 * 3737 * Notes: 3738 * - we don't move root/cwd if they are not at the root (reason: if something 3739 * cared enough to change them, it's probably wrong to force them elsewhere) 3740 * - it's okay to pick a root that isn't the root of a file system, e.g. 3741 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, 3742 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root 3743 * first. 3744 */ 3745 SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, 3746 const char __user *, put_old) 3747 { 3748 struct path new, old, root; 3749 struct mount *new_mnt, *root_mnt, *old_mnt, *root_parent, *ex_parent; 3750 struct mountpoint *old_mp, *root_mp; 3751 int error; 3752 3753 if (!may_mount()) 3754 return -EPERM; 3755 3756 error = user_path_at(AT_FDCWD, new_root, 3757 LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &new); 3758 if (error) 3759 goto out0; 3760 3761 error = user_path_at(AT_FDCWD, put_old, 3762 LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old); 3763 if (error) 3764 goto out1; 3765 3766 error = security_sb_pivotroot(&old, &new); 3767 if (error) 3768 goto out2; 3769 3770 get_fs_root(current->fs, &root); 3771 old_mp = lock_mount(&old); 3772 error = PTR_ERR(old_mp); 3773 if (IS_ERR(old_mp)) 3774 goto out3; 3775 3776 error = -EINVAL; 3777 new_mnt = real_mount(new.mnt); 3778 root_mnt = real_mount(root.mnt); 3779 old_mnt = real_mount(old.mnt); 3780 ex_parent = new_mnt->mnt_parent; 3781 root_parent = root_mnt->mnt_parent; 3782 if (IS_MNT_SHARED(old_mnt) || 3783 IS_MNT_SHARED(ex_parent) || 3784 IS_MNT_SHARED(root_parent)) 3785 goto out4; 3786 if (!check_mnt(root_mnt) || !check_mnt(new_mnt)) 3787 goto out4; 3788 if (new_mnt->mnt.mnt_flags & MNT_LOCKED) 3789 goto out4; 3790 error = -ENOENT; 3791 if (d_unlinked(new.dentry)) 3792 goto out4; 3793 error = -EBUSY; 3794 if (new_mnt == root_mnt || old_mnt == root_mnt) 3795 goto out4; /* loop, on the same file system */ 3796 error = -EINVAL; 3797 if (root.mnt->mnt_root != root.dentry) 3798 goto out4; /* not a mountpoint */ 3799 if (!mnt_has_parent(root_mnt)) 3800 goto out4; /* not attached */ 3801 if (new.mnt->mnt_root != new.dentry) 3802 goto out4; /* not a mountpoint */ 3803 if (!mnt_has_parent(new_mnt)) 3804 goto out4; /* not attached */ 3805 /* make sure we can reach put_old from new_root */ 3806 if (!is_path_reachable(old_mnt, old.dentry, &new)) 3807 goto out4; 3808 /* make certain new is below the root */ 3809 if (!is_path_reachable(new_mnt, new.dentry, &root)) 3810 goto out4; 3811 lock_mount_hash(); 3812 umount_mnt(new_mnt); 3813 root_mp = unhash_mnt(root_mnt); /* we'll need its mountpoint */ 3814 if (root_mnt->mnt.mnt_flags & MNT_LOCKED) { 3815 new_mnt->mnt.mnt_flags |= MNT_LOCKED; 3816 root_mnt->mnt.mnt_flags &= ~MNT_LOCKED; 3817 } 3818 /* mount old root on put_old */ 3819 attach_mnt(root_mnt, old_mnt, old_mp); 3820 /* mount new_root on / */ 3821 attach_mnt(new_mnt, root_parent, root_mp); 3822 mnt_add_count(root_parent, -1); 3823 touch_mnt_namespace(current->nsproxy->mnt_ns); 3824 /* A moved mount should not expire automatically */ 3825 list_del_init(&new_mnt->mnt_expire); 3826 put_mountpoint(root_mp); 3827 unlock_mount_hash(); 3828 chroot_fs_refs(&root, &new); 3829 error = 0; 3830 out4: 3831 unlock_mount(old_mp); 3832 if (!error) 3833 mntput_no_expire(ex_parent); 3834 out3: 3835 path_put(&root); 3836 out2: 3837 path_put(&old); 3838 out1: 3839 path_put(&new); 3840 out0: 3841 return error; 3842 } 3843 3844 static unsigned int recalc_flags(struct mount_kattr *kattr, struct mount *mnt) 3845 { 3846 unsigned int flags = mnt->mnt.mnt_flags; 3847 3848 /* flags to clear */ 3849 flags &= ~kattr->attr_clr; 3850 /* flags to raise */ 3851 flags |= kattr->attr_set; 3852 3853 return flags; 3854 } 3855 3856 static int can_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt) 3857 { 3858 struct vfsmount *m = &mnt->mnt; 3859 3860 if (!kattr->mnt_userns) 3861 return 0; 3862 3863 /* 3864 * Once a mount has been idmapped we don't allow it to change its 3865 * mapping. It makes things simpler and callers can just create 3866 * another bind-mount they can idmap if they want to. 3867 */ 3868 if (mnt_user_ns(m) != &init_user_ns) 3869 return -EPERM; 3870 3871 /* The underlying filesystem doesn't support idmapped mounts yet. */ 3872 if (!(m->mnt_sb->s_type->fs_flags & FS_ALLOW_IDMAP)) 3873 return -EINVAL; 3874 3875 /* Don't yet support filesystem mountable in user namespaces. */ 3876 if (m->mnt_sb->s_user_ns != &init_user_ns) 3877 return -EINVAL; 3878 3879 /* We're not controlling the superblock. */ 3880 if (!capable(CAP_SYS_ADMIN)) 3881 return -EPERM; 3882 3883 /* Mount has already been visible in the filesystem hierarchy. */ 3884 if (!is_anon_ns(mnt->mnt_ns)) 3885 return -EINVAL; 3886 3887 return 0; 3888 } 3889 3890 static struct mount *mount_setattr_prepare(struct mount_kattr *kattr, 3891 struct mount *mnt, int *err) 3892 { 3893 struct mount *m = mnt, *last = NULL; 3894 3895 if (!is_mounted(&m->mnt)) { 3896 *err = -EINVAL; 3897 goto out; 3898 } 3899 3900 if (!(mnt_has_parent(m) ? check_mnt(m) : is_anon_ns(m->mnt_ns))) { 3901 *err = -EINVAL; 3902 goto out; 3903 } 3904 3905 do { 3906 unsigned int flags; 3907 3908 flags = recalc_flags(kattr, m); 3909 if (!can_change_locked_flags(m, flags)) { 3910 *err = -EPERM; 3911 goto out; 3912 } 3913 3914 *err = can_idmap_mount(kattr, m); 3915 if (*err) 3916 goto out; 3917 3918 last = m; 3919 3920 if ((kattr->attr_set & MNT_READONLY) && 3921 !(m->mnt.mnt_flags & MNT_READONLY)) { 3922 *err = mnt_hold_writers(m); 3923 if (*err) 3924 goto out; 3925 } 3926 } while (kattr->recurse && (m = next_mnt(m, mnt))); 3927 3928 out: 3929 return last; 3930 } 3931 3932 static void do_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt) 3933 { 3934 struct user_namespace *mnt_userns; 3935 3936 if (!kattr->mnt_userns) 3937 return; 3938 3939 mnt_userns = get_user_ns(kattr->mnt_userns); 3940 /* Pairs with smp_load_acquire() in mnt_user_ns(). */ 3941 smp_store_release(&mnt->mnt.mnt_userns, mnt_userns); 3942 } 3943 3944 static void mount_setattr_commit(struct mount_kattr *kattr, 3945 struct mount *mnt, struct mount *last, 3946 int err) 3947 { 3948 struct mount *m = mnt; 3949 3950 do { 3951 if (!err) { 3952 unsigned int flags; 3953 3954 do_idmap_mount(kattr, m); 3955 flags = recalc_flags(kattr, m); 3956 WRITE_ONCE(m->mnt.mnt_flags, flags); 3957 } 3958 3959 /* 3960 * We either set MNT_READONLY above so make it visible 3961 * before ~MNT_WRITE_HOLD or we failed to recursively 3962 * apply mount options. 3963 */ 3964 if ((kattr->attr_set & MNT_READONLY) && 3965 (m->mnt.mnt_flags & MNT_WRITE_HOLD)) 3966 mnt_unhold_writers(m); 3967 3968 if (!err && kattr->propagation) 3969 change_mnt_propagation(m, kattr->propagation); 3970 3971 /* 3972 * On failure, only cleanup until we found the first mount 3973 * we failed to handle. 3974 */ 3975 if (err && m == last) 3976 break; 3977 } while (kattr->recurse && (m = next_mnt(m, mnt))); 3978 3979 if (!err) 3980 touch_mnt_namespace(mnt->mnt_ns); 3981 } 3982 3983 static int do_mount_setattr(struct path *path, struct mount_kattr *kattr) 3984 { 3985 struct mount *mnt = real_mount(path->mnt), *last = NULL; 3986 int err = 0; 3987 3988 if (path->dentry != mnt->mnt.mnt_root) 3989 return -EINVAL; 3990 3991 if (kattr->propagation) { 3992 /* 3993 * Only take namespace_lock() if we're actually changing 3994 * propagation. 3995 */ 3996 namespace_lock(); 3997 if (kattr->propagation == MS_SHARED) { 3998 err = invent_group_ids(mnt, kattr->recurse); 3999 if (err) { 4000 namespace_unlock(); 4001 return err; 4002 } 4003 } 4004 } 4005 4006 lock_mount_hash(); 4007 4008 /* 4009 * Get the mount tree in a shape where we can change mount 4010 * properties without failure. 4011 */ 4012 last = mount_setattr_prepare(kattr, mnt, &err); 4013 if (last) /* Commit all changes or revert to the old state. */ 4014 mount_setattr_commit(kattr, mnt, last, err); 4015 4016 unlock_mount_hash(); 4017 4018 if (kattr->propagation) { 4019 namespace_unlock(); 4020 if (err) 4021 cleanup_group_ids(mnt, NULL); 4022 } 4023 4024 return err; 4025 } 4026 4027 static int build_mount_idmapped(const struct mount_attr *attr, size_t usize, 4028 struct mount_kattr *kattr, unsigned int flags) 4029 { 4030 int err = 0; 4031 struct ns_common *ns; 4032 struct user_namespace *mnt_userns; 4033 struct file *file; 4034 4035 if (!((attr->attr_set | attr->attr_clr) & MOUNT_ATTR_IDMAP)) 4036 return 0; 4037 4038 /* 4039 * We currently do not support clearing an idmapped mount. If this ever 4040 * is a use-case we can revisit this but for now let's keep it simple 4041 * and not allow it. 4042 */ 4043 if (attr->attr_clr & MOUNT_ATTR_IDMAP) 4044 return -EINVAL; 4045 4046 if (attr->userns_fd > INT_MAX) 4047 return -EINVAL; 4048 4049 file = fget(attr->userns_fd); 4050 if (!file) 4051 return -EBADF; 4052 4053 if (!proc_ns_file(file)) { 4054 err = -EINVAL; 4055 goto out_fput; 4056 } 4057 4058 ns = get_proc_ns(file_inode(file)); 4059 if (ns->ops->type != CLONE_NEWUSER) { 4060 err = -EINVAL; 4061 goto out_fput; 4062 } 4063 4064 /* 4065 * The init_user_ns is used to indicate that a vfsmount is not idmapped. 4066 * This is simpler than just having to treat NULL as unmapped. Users 4067 * wanting to idmap a mount to init_user_ns can just use a namespace 4068 * with an identity mapping. 4069 */ 4070 mnt_userns = container_of(ns, struct user_namespace, ns); 4071 if (mnt_userns == &init_user_ns) { 4072 err = -EPERM; 4073 goto out_fput; 4074 } 4075 kattr->mnt_userns = get_user_ns(mnt_userns); 4076 4077 out_fput: 4078 fput(file); 4079 return err; 4080 } 4081 4082 static int build_mount_kattr(const struct mount_attr *attr, size_t usize, 4083 struct mount_kattr *kattr, unsigned int flags) 4084 { 4085 unsigned int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW; 4086 4087 if (flags & AT_NO_AUTOMOUNT) 4088 lookup_flags &= ~LOOKUP_AUTOMOUNT; 4089 if (flags & AT_SYMLINK_NOFOLLOW) 4090 lookup_flags &= ~LOOKUP_FOLLOW; 4091 if (flags & AT_EMPTY_PATH) 4092 lookup_flags |= LOOKUP_EMPTY; 4093 4094 *kattr = (struct mount_kattr) { 4095 .lookup_flags = lookup_flags, 4096 .recurse = !!(flags & AT_RECURSIVE), 4097 }; 4098 4099 if (attr->propagation & ~MOUNT_SETATTR_PROPAGATION_FLAGS) 4100 return -EINVAL; 4101 if (hweight32(attr->propagation & MOUNT_SETATTR_PROPAGATION_FLAGS) > 1) 4102 return -EINVAL; 4103 kattr->propagation = attr->propagation; 4104 4105 if ((attr->attr_set | attr->attr_clr) & ~MOUNT_SETATTR_VALID_FLAGS) 4106 return -EINVAL; 4107 4108 kattr->attr_set = attr_flags_to_mnt_flags(attr->attr_set); 4109 kattr->attr_clr = attr_flags_to_mnt_flags(attr->attr_clr); 4110 4111 /* 4112 * Since the MOUNT_ATTR_<atime> values are an enum, not a bitmap, 4113 * users wanting to transition to a different atime setting cannot 4114 * simply specify the atime setting in @attr_set, but must also 4115 * specify MOUNT_ATTR__ATIME in the @attr_clr field. 4116 * So ensure that MOUNT_ATTR__ATIME can't be partially set in 4117 * @attr_clr and that @attr_set can't have any atime bits set if 4118 * MOUNT_ATTR__ATIME isn't set in @attr_clr. 4119 */ 4120 if (attr->attr_clr & MOUNT_ATTR__ATIME) { 4121 if ((attr->attr_clr & MOUNT_ATTR__ATIME) != MOUNT_ATTR__ATIME) 4122 return -EINVAL; 4123 4124 /* 4125 * Clear all previous time settings as they are mutually 4126 * exclusive. 4127 */ 4128 kattr->attr_clr |= MNT_RELATIME | MNT_NOATIME; 4129 switch (attr->attr_set & MOUNT_ATTR__ATIME) { 4130 case MOUNT_ATTR_RELATIME: 4131 kattr->attr_set |= MNT_RELATIME; 4132 break; 4133 case MOUNT_ATTR_NOATIME: 4134 kattr->attr_set |= MNT_NOATIME; 4135 break; 4136 case MOUNT_ATTR_STRICTATIME: 4137 break; 4138 default: 4139 return -EINVAL; 4140 } 4141 } else { 4142 if (attr->attr_set & MOUNT_ATTR__ATIME) 4143 return -EINVAL; 4144 } 4145 4146 return build_mount_idmapped(attr, usize, kattr, flags); 4147 } 4148 4149 static void finish_mount_kattr(struct mount_kattr *kattr) 4150 { 4151 put_user_ns(kattr->mnt_userns); 4152 kattr->mnt_userns = NULL; 4153 } 4154 4155 SYSCALL_DEFINE5(mount_setattr, int, dfd, const char __user *, path, 4156 unsigned int, flags, struct mount_attr __user *, uattr, 4157 size_t, usize) 4158 { 4159 int err; 4160 struct path target; 4161 struct mount_attr attr; 4162 struct mount_kattr kattr; 4163 4164 BUILD_BUG_ON(sizeof(struct mount_attr) != MOUNT_ATTR_SIZE_VER0); 4165 4166 if (flags & ~(AT_EMPTY_PATH | 4167 AT_RECURSIVE | 4168 AT_SYMLINK_NOFOLLOW | 4169 AT_NO_AUTOMOUNT)) 4170 return -EINVAL; 4171 4172 if (unlikely(usize > PAGE_SIZE)) 4173 return -E2BIG; 4174 if (unlikely(usize < MOUNT_ATTR_SIZE_VER0)) 4175 return -EINVAL; 4176 4177 if (!may_mount()) 4178 return -EPERM; 4179 4180 err = copy_struct_from_user(&attr, sizeof(attr), uattr, usize); 4181 if (err) 4182 return err; 4183 4184 /* Don't bother walking through the mounts if this is a nop. */ 4185 if (attr.attr_set == 0 && 4186 attr.attr_clr == 0 && 4187 attr.propagation == 0) 4188 return 0; 4189 4190 err = build_mount_kattr(&attr, usize, &kattr, flags); 4191 if (err) 4192 return err; 4193 4194 err = user_path_at(dfd, path, kattr.lookup_flags, &target); 4195 if (err) 4196 return err; 4197 4198 err = do_mount_setattr(&target, &kattr); 4199 finish_mount_kattr(&kattr); 4200 path_put(&target); 4201 return err; 4202 } 4203 4204 static void __init init_mount_tree(void) 4205 { 4206 struct vfsmount *mnt; 4207 struct mount *m; 4208 struct mnt_namespace *ns; 4209 struct path root; 4210 4211 mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", NULL); 4212 if (IS_ERR(mnt)) 4213 panic("Can't create rootfs"); 4214 4215 ns = alloc_mnt_ns(&init_user_ns, false); 4216 if (IS_ERR(ns)) 4217 panic("Can't allocate initial namespace"); 4218 m = real_mount(mnt); 4219 m->mnt_ns = ns; 4220 ns->root = m; 4221 ns->mounts = 1; 4222 list_add(&m->mnt_list, &ns->list); 4223 init_task.nsproxy->mnt_ns = ns; 4224 get_mnt_ns(ns); 4225 4226 root.mnt = mnt; 4227 root.dentry = mnt->mnt_root; 4228 mnt->mnt_flags |= MNT_LOCKED; 4229 4230 set_fs_pwd(current->fs, &root); 4231 set_fs_root(current->fs, &root); 4232 } 4233 4234 void __init mnt_init(void) 4235 { 4236 int err; 4237 4238 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount), 4239 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); 4240 4241 mount_hashtable = alloc_large_system_hash("Mount-cache", 4242 sizeof(struct hlist_head), 4243 mhash_entries, 19, 4244 HASH_ZERO, 4245 &m_hash_shift, &m_hash_mask, 0, 0); 4246 mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache", 4247 sizeof(struct hlist_head), 4248 mphash_entries, 19, 4249 HASH_ZERO, 4250 &mp_hash_shift, &mp_hash_mask, 0, 0); 4251 4252 if (!mount_hashtable || !mountpoint_hashtable) 4253 panic("Failed to allocate mount hash table\n"); 4254 4255 kernfs_init(); 4256 4257 err = sysfs_init(); 4258 if (err) 4259 printk(KERN_WARNING "%s: sysfs_init error: %d\n", 4260 __func__, err); 4261 fs_kobj = kobject_create_and_add("fs", NULL); 4262 if (!fs_kobj) 4263 printk(KERN_WARNING "%s: kobj create error\n", __func__); 4264 shmem_init(); 4265 init_rootfs(); 4266 init_mount_tree(); 4267 } 4268 4269 void put_mnt_ns(struct mnt_namespace *ns) 4270 { 4271 if (!refcount_dec_and_test(&ns->ns.count)) 4272 return; 4273 drop_collected_mounts(&ns->root->mnt); 4274 free_mnt_ns(ns); 4275 } 4276 4277 struct vfsmount *kern_mount(struct file_system_type *type) 4278 { 4279 struct vfsmount *mnt; 4280 mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL); 4281 if (!IS_ERR(mnt)) { 4282 /* 4283 * it is a longterm mount, don't release mnt until 4284 * we unmount before file sys is unregistered 4285 */ 4286 real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL; 4287 } 4288 return mnt; 4289 } 4290 EXPORT_SYMBOL_GPL(kern_mount); 4291 4292 void kern_unmount(struct vfsmount *mnt) 4293 { 4294 /* release long term mount so mount point can be released */ 4295 if (!IS_ERR_OR_NULL(mnt)) { 4296 real_mount(mnt)->mnt_ns = NULL; 4297 synchronize_rcu(); /* yecchhh... */ 4298 mntput(mnt); 4299 } 4300 } 4301 EXPORT_SYMBOL(kern_unmount); 4302 4303 void kern_unmount_array(struct vfsmount *mnt[], unsigned int num) 4304 { 4305 unsigned int i; 4306 4307 for (i = 0; i < num; i++) 4308 if (mnt[i]) 4309 real_mount(mnt[i])->mnt_ns = NULL; 4310 synchronize_rcu_expedited(); 4311 for (i = 0; i < num; i++) 4312 mntput(mnt[i]); 4313 } 4314 EXPORT_SYMBOL(kern_unmount_array); 4315 4316 bool our_mnt(struct vfsmount *mnt) 4317 { 4318 return check_mnt(real_mount(mnt)); 4319 } 4320 4321 bool current_chrooted(void) 4322 { 4323 /* Does the current process have a non-standard root */ 4324 struct path ns_root; 4325 struct path fs_root; 4326 bool chrooted; 4327 4328 /* Find the namespace root */ 4329 ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt; 4330 ns_root.dentry = ns_root.mnt->mnt_root; 4331 path_get(&ns_root); 4332 while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root)) 4333 ; 4334 4335 get_fs_root(current->fs, &fs_root); 4336 4337 chrooted = !path_equal(&fs_root, &ns_root); 4338 4339 path_put(&fs_root); 4340 path_put(&ns_root); 4341 4342 return chrooted; 4343 } 4344 4345 static bool mnt_already_visible(struct mnt_namespace *ns, 4346 const struct super_block *sb, 4347 int *new_mnt_flags) 4348 { 4349 int new_flags = *new_mnt_flags; 4350 struct mount *mnt; 4351 bool visible = false; 4352 4353 down_read(&namespace_sem); 4354 lock_ns_list(ns); 4355 list_for_each_entry(mnt, &ns->list, mnt_list) { 4356 struct mount *child; 4357 int mnt_flags; 4358 4359 if (mnt_is_cursor(mnt)) 4360 continue; 4361 4362 if (mnt->mnt.mnt_sb->s_type != sb->s_type) 4363 continue; 4364 4365 /* This mount is not fully visible if it's root directory 4366 * is not the root directory of the filesystem. 4367 */ 4368 if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root) 4369 continue; 4370 4371 /* A local view of the mount flags */ 4372 mnt_flags = mnt->mnt.mnt_flags; 4373 4374 /* Don't miss readonly hidden in the superblock flags */ 4375 if (sb_rdonly(mnt->mnt.mnt_sb)) 4376 mnt_flags |= MNT_LOCK_READONLY; 4377 4378 /* Verify the mount flags are equal to or more permissive 4379 * than the proposed new mount. 4380 */ 4381 if ((mnt_flags & MNT_LOCK_READONLY) && 4382 !(new_flags & MNT_READONLY)) 4383 continue; 4384 if ((mnt_flags & MNT_LOCK_ATIME) && 4385 ((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK))) 4386 continue; 4387 4388 /* This mount is not fully visible if there are any 4389 * locked child mounts that cover anything except for 4390 * empty directories. 4391 */ 4392 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { 4393 struct inode *inode = child->mnt_mountpoint->d_inode; 4394 /* Only worry about locked mounts */ 4395 if (!(child->mnt.mnt_flags & MNT_LOCKED)) 4396 continue; 4397 /* Is the directory permanetly empty? */ 4398 if (!is_empty_dir_inode(inode)) 4399 goto next; 4400 } 4401 /* Preserve the locked attributes */ 4402 *new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \ 4403 MNT_LOCK_ATIME); 4404 visible = true; 4405 goto found; 4406 next: ; 4407 } 4408 found: 4409 unlock_ns_list(ns); 4410 up_read(&namespace_sem); 4411 return visible; 4412 } 4413 4414 static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags) 4415 { 4416 const unsigned long required_iflags = SB_I_NOEXEC | SB_I_NODEV; 4417 struct mnt_namespace *ns = current->nsproxy->mnt_ns; 4418 unsigned long s_iflags; 4419 4420 if (ns->user_ns == &init_user_ns) 4421 return false; 4422 4423 /* Can this filesystem be too revealing? */ 4424 s_iflags = sb->s_iflags; 4425 if (!(s_iflags & SB_I_USERNS_VISIBLE)) 4426 return false; 4427 4428 if ((s_iflags & required_iflags) != required_iflags) { 4429 WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n", 4430 required_iflags); 4431 return true; 4432 } 4433 4434 return !mnt_already_visible(ns, sb, new_mnt_flags); 4435 } 4436 4437 bool mnt_may_suid(struct vfsmount *mnt) 4438 { 4439 /* 4440 * Foreign mounts (accessed via fchdir or through /proc 4441 * symlinks) are always treated as if they are nosuid. This 4442 * prevents namespaces from trusting potentially unsafe 4443 * suid/sgid bits, file caps, or security labels that originate 4444 * in other namespaces. 4445 */ 4446 return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) && 4447 current_in_userns(mnt->mnt_sb->s_user_ns); 4448 } 4449 4450 static struct ns_common *mntns_get(struct task_struct *task) 4451 { 4452 struct ns_common *ns = NULL; 4453 struct nsproxy *nsproxy; 4454 4455 task_lock(task); 4456 nsproxy = task->nsproxy; 4457 if (nsproxy) { 4458 ns = &nsproxy->mnt_ns->ns; 4459 get_mnt_ns(to_mnt_ns(ns)); 4460 } 4461 task_unlock(task); 4462 4463 return ns; 4464 } 4465 4466 static void mntns_put(struct ns_common *ns) 4467 { 4468 put_mnt_ns(to_mnt_ns(ns)); 4469 } 4470 4471 static int mntns_install(struct nsset *nsset, struct ns_common *ns) 4472 { 4473 struct nsproxy *nsproxy = nsset->nsproxy; 4474 struct fs_struct *fs = nsset->fs; 4475 struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns; 4476 struct user_namespace *user_ns = nsset->cred->user_ns; 4477 struct path root; 4478 int err; 4479 4480 if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) || 4481 !ns_capable(user_ns, CAP_SYS_CHROOT) || 4482 !ns_capable(user_ns, CAP_SYS_ADMIN)) 4483 return -EPERM; 4484 4485 if (is_anon_ns(mnt_ns)) 4486 return -EINVAL; 4487 4488 if (fs->users != 1) 4489 return -EINVAL; 4490 4491 get_mnt_ns(mnt_ns); 4492 old_mnt_ns = nsproxy->mnt_ns; 4493 nsproxy->mnt_ns = mnt_ns; 4494 4495 /* Find the root */ 4496 err = vfs_path_lookup(mnt_ns->root->mnt.mnt_root, &mnt_ns->root->mnt, 4497 "/", LOOKUP_DOWN, &root); 4498 if (err) { 4499 /* revert to old namespace */ 4500 nsproxy->mnt_ns = old_mnt_ns; 4501 put_mnt_ns(mnt_ns); 4502 return err; 4503 } 4504 4505 put_mnt_ns(old_mnt_ns); 4506 4507 /* Update the pwd and root */ 4508 set_fs_pwd(fs, &root); 4509 set_fs_root(fs, &root); 4510 4511 path_put(&root); 4512 return 0; 4513 } 4514 4515 static struct user_namespace *mntns_owner(struct ns_common *ns) 4516 { 4517 return to_mnt_ns(ns)->user_ns; 4518 } 4519 4520 const struct proc_ns_operations mntns_operations = { 4521 .name = "mnt", 4522 .type = CLONE_NEWNS, 4523 .get = mntns_get, 4524 .put = mntns_put, 4525 .install = mntns_install, 4526 .owner = mntns_owner, 4527 }; 4528