1 #include <linux/mount.h> 2 #include <linux/file.h> 3 #include <linux/fs.h> 4 #include <linux/proc_ns.h> 5 #include <linux/magic.h> 6 #include <linux/ktime.h> 7 #include <linux/seq_file.h> 8 #include <linux/user_namespace.h> 9 #include <linux/nsfs.h> 10 #include <linux/uaccess.h> 11 12 static struct vfsmount *nsfs_mnt; 13 14 static long ns_ioctl(struct file *filp, unsigned int ioctl, 15 unsigned long arg); 16 static const struct file_operations ns_file_operations = { 17 .llseek = no_llseek, 18 .unlocked_ioctl = ns_ioctl, 19 }; 20 21 static char *ns_dname(struct dentry *dentry, char *buffer, int buflen) 22 { 23 struct inode *inode = d_inode(dentry); 24 const struct proc_ns_operations *ns_ops = dentry->d_fsdata; 25 26 return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]", 27 ns_ops->name, inode->i_ino); 28 } 29 30 static void ns_prune_dentry(struct dentry *dentry) 31 { 32 struct inode *inode = d_inode(dentry); 33 if (inode) { 34 struct ns_common *ns = inode->i_private; 35 atomic_long_set(&ns->stashed, 0); 36 } 37 } 38 39 const struct dentry_operations ns_dentry_operations = 40 { 41 .d_prune = ns_prune_dentry, 42 .d_delete = always_delete_dentry, 43 .d_dname = ns_dname, 44 }; 45 46 static void nsfs_evict(struct inode *inode) 47 { 48 struct ns_common *ns = inode->i_private; 49 clear_inode(inode); 50 ns->ops->put(ns); 51 } 52 53 static void *__ns_get_path(struct path *path, struct ns_common *ns) 54 { 55 struct vfsmount *mnt = nsfs_mnt; 56 struct dentry *dentry; 57 struct inode *inode; 58 unsigned long d; 59 60 rcu_read_lock(); 61 d = atomic_long_read(&ns->stashed); 62 if (!d) 63 goto slow; 64 dentry = (struct dentry *)d; 65 if (!lockref_get_not_dead(&dentry->d_lockref)) 66 goto slow; 67 rcu_read_unlock(); 68 ns->ops->put(ns); 69 got_it: 70 path->mnt = mntget(mnt); 71 path->dentry = dentry; 72 return NULL; 73 slow: 74 rcu_read_unlock(); 75 inode = new_inode_pseudo(mnt->mnt_sb); 76 if (!inode) { 77 ns->ops->put(ns); 78 return ERR_PTR(-ENOMEM); 79 } 80 inode->i_ino = ns->inum; 81 inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); 82 inode->i_flags |= S_IMMUTABLE; 83 inode->i_mode = S_IFREG | S_IRUGO; 84 inode->i_fop = &ns_file_operations; 85 inode->i_private = ns; 86 87 dentry = d_alloc_pseudo(mnt->mnt_sb, &empty_name); 88 if (!dentry) { 89 iput(inode); 90 return ERR_PTR(-ENOMEM); 91 } 92 d_instantiate(dentry, inode); 93 dentry->d_flags |= DCACHE_RCUACCESS; 94 dentry->d_fsdata = (void *)ns->ops; 95 d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry); 96 if (d) { 97 d_delete(dentry); /* make sure ->d_prune() does nothing */ 98 dput(dentry); 99 cpu_relax(); 100 return ERR_PTR(-EAGAIN); 101 } 102 goto got_it; 103 } 104 105 void *ns_get_path(struct path *path, struct task_struct *task, 106 const struct proc_ns_operations *ns_ops) 107 { 108 struct ns_common *ns; 109 void *ret; 110 111 again: 112 ns = ns_ops->get(task); 113 if (!ns) 114 return ERR_PTR(-ENOENT); 115 116 ret = __ns_get_path(path, ns); 117 if (IS_ERR(ret) && PTR_ERR(ret) == -EAGAIN) 118 goto again; 119 return ret; 120 } 121 122 int open_related_ns(struct ns_common *ns, 123 struct ns_common *(*get_ns)(struct ns_common *ns)) 124 { 125 struct path path = {}; 126 struct file *f; 127 void *err; 128 int fd; 129 130 fd = get_unused_fd_flags(O_CLOEXEC); 131 if (fd < 0) 132 return fd; 133 134 while (1) { 135 struct ns_common *relative; 136 137 relative = get_ns(ns); 138 if (IS_ERR(relative)) { 139 put_unused_fd(fd); 140 return PTR_ERR(relative); 141 } 142 143 err = __ns_get_path(&path, relative); 144 if (IS_ERR(err) && PTR_ERR(err) == -EAGAIN) 145 continue; 146 break; 147 } 148 if (IS_ERR(err)) { 149 put_unused_fd(fd); 150 return PTR_ERR(err); 151 } 152 153 f = dentry_open(&path, O_RDONLY, current_cred()); 154 path_put(&path); 155 if (IS_ERR(f)) { 156 put_unused_fd(fd); 157 fd = PTR_ERR(f); 158 } else 159 fd_install(fd, f); 160 161 return fd; 162 } 163 164 static long ns_ioctl(struct file *filp, unsigned int ioctl, 165 unsigned long arg) 166 { 167 struct user_namespace *user_ns; 168 struct ns_common *ns = get_proc_ns(file_inode(filp)); 169 uid_t __user *argp; 170 uid_t uid; 171 172 switch (ioctl) { 173 case NS_GET_USERNS: 174 return open_related_ns(ns, ns_get_owner); 175 case NS_GET_PARENT: 176 if (!ns->ops->get_parent) 177 return -EINVAL; 178 return open_related_ns(ns, ns->ops->get_parent); 179 case NS_GET_NSTYPE: 180 return ns->ops->type; 181 case NS_GET_OWNER_UID: 182 if (ns->ops->type != CLONE_NEWUSER) 183 return -EINVAL; 184 user_ns = container_of(ns, struct user_namespace, ns); 185 argp = (uid_t __user *) arg; 186 uid = from_kuid_munged(current_user_ns(), user_ns->owner); 187 return put_user(uid, argp); 188 default: 189 return -ENOTTY; 190 } 191 } 192 193 int ns_get_name(char *buf, size_t size, struct task_struct *task, 194 const struct proc_ns_operations *ns_ops) 195 { 196 struct ns_common *ns; 197 int res = -ENOENT; 198 const char *name; 199 ns = ns_ops->get(task); 200 if (ns) { 201 name = ns_ops->real_ns_name ? : ns_ops->name; 202 res = snprintf(buf, size, "%s:[%u]", name, ns->inum); 203 ns_ops->put(ns); 204 } 205 return res; 206 } 207 208 struct file *proc_ns_fget(int fd) 209 { 210 struct file *file; 211 212 file = fget(fd); 213 if (!file) 214 return ERR_PTR(-EBADF); 215 216 if (file->f_op != &ns_file_operations) 217 goto out_invalid; 218 219 return file; 220 221 out_invalid: 222 fput(file); 223 return ERR_PTR(-EINVAL); 224 } 225 226 static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry) 227 { 228 struct inode *inode = d_inode(dentry); 229 const struct proc_ns_operations *ns_ops = dentry->d_fsdata; 230 231 seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino); 232 return 0; 233 } 234 235 static const struct super_operations nsfs_ops = { 236 .statfs = simple_statfs, 237 .evict_inode = nsfs_evict, 238 .show_path = nsfs_show_path, 239 }; 240 static struct dentry *nsfs_mount(struct file_system_type *fs_type, 241 int flags, const char *dev_name, void *data) 242 { 243 return mount_pseudo(fs_type, "nsfs:", &nsfs_ops, 244 &ns_dentry_operations, NSFS_MAGIC); 245 } 246 static struct file_system_type nsfs = { 247 .name = "nsfs", 248 .mount = nsfs_mount, 249 .kill_sb = kill_anon_super, 250 }; 251 252 void __init nsfs_init(void) 253 { 254 nsfs_mnt = kern_mount(&nsfs); 255 if (IS_ERR(nsfs_mnt)) 256 panic("can't set nsfs up\n"); 257 nsfs_mnt->mnt_sb->s_flags &= ~MS_NOUSER; 258 } 259