| 1 | /* |
| 2 | * linux/fs/namespace.c |
| 3 | * |
| 4 | * (C) Copyright Al Viro 2000, 2001 |
| 5 | * Released under GPL v2. |
| 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/idr.h> |
| 19 | #include <linux/acct.h> /* acct_auto_close_mnt */ |
| 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/uaccess.h> |
| 24 | #include <linux/proc_ns.h> |
| 25 | #include <linux/magic.h> |
| 26 | #include "pnode.h" |
| 27 | #include "internal.h" |
| 28 | |
| 29 | #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head)) |
| 30 | #define HASH_SIZE (1UL << HASH_SHIFT) |
| 31 | |
| 32 | static int event; |
| 33 | static DEFINE_IDA(mnt_id_ida); |
| 34 | static DEFINE_IDA(mnt_group_ida); |
| 35 | static DEFINE_SPINLOCK(mnt_id_lock); |
| 36 | static int mnt_id_start = 0; |
| 37 | static int mnt_group_start = 1; |
| 38 | |
| 39 | static struct list_head *mount_hashtable __read_mostly; |
| 40 | static struct list_head *mountpoint_hashtable __read_mostly; |
| 41 | static struct kmem_cache *mnt_cache __read_mostly; |
| 42 | static DECLARE_RWSEM(namespace_sem); |
| 43 | |
| 44 | /* /sys/fs */ |
| 45 | struct kobject *fs_kobj; |
| 46 | EXPORT_SYMBOL_GPL(fs_kobj); |
| 47 | |
| 48 | /* |
| 49 | * vfsmount lock may be taken for read to prevent changes to the |
| 50 | * vfsmount hash, ie. during mountpoint lookups or walking back |
| 51 | * up the tree. |
| 52 | * |
| 53 | * It should be taken for write in all cases where the vfsmount |
| 54 | * tree or hash is modified or when a vfsmount structure is modified. |
| 55 | */ |
| 56 | __cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock); |
| 57 | |
| 58 | static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) |
| 59 | { |
| 60 | unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); |
| 61 | tmp += ((unsigned long)dentry / L1_CACHE_BYTES); |
| 62 | tmp = tmp + (tmp >> HASH_SHIFT); |
| 63 | return tmp & (HASH_SIZE - 1); |
| 64 | } |
| 65 | |
| 66 | /* |
| 67 | * allocation is serialized by namespace_sem, but we need the spinlock to |
| 68 | * serialize with freeing. |
| 69 | */ |
| 70 | static int mnt_alloc_id(struct mount *mnt) |
| 71 | { |
| 72 | int res; |
| 73 | |
| 74 | retry: |
| 75 | ida_pre_get(&mnt_id_ida, GFP_KERNEL); |
| 76 | spin_lock(&mnt_id_lock); |
| 77 | res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id); |
| 78 | if (!res) |
| 79 | mnt_id_start = mnt->mnt_id + 1; |
| 80 | spin_unlock(&mnt_id_lock); |
| 81 | if (res == -EAGAIN) |
| 82 | goto retry; |
| 83 | |
| 84 | return res; |
| 85 | } |
| 86 | |
| 87 | static void mnt_free_id(struct mount *mnt) |
| 88 | { |
| 89 | int id = mnt->mnt_id; |
| 90 | spin_lock(&mnt_id_lock); |
| 91 | ida_remove(&mnt_id_ida, id); |
| 92 | if (mnt_id_start > id) |
| 93 | mnt_id_start = id; |
| 94 | spin_unlock(&mnt_id_lock); |
| 95 | } |
| 96 | |
| 97 | /* |
| 98 | * Allocate a new peer group ID |
| 99 | * |
| 100 | * mnt_group_ida is protected by namespace_sem |
| 101 | */ |
| 102 | static int mnt_alloc_group_id(struct mount *mnt) |
| 103 | { |
| 104 | int res; |
| 105 | |
| 106 | if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL)) |
| 107 | return -ENOMEM; |
| 108 | |
| 109 | res = ida_get_new_above(&mnt_group_ida, |
| 110 | mnt_group_start, |
| 111 | &mnt->mnt_group_id); |
| 112 | if (!res) |
| 113 | mnt_group_start = mnt->mnt_group_id + 1; |
| 114 | |
| 115 | return res; |
| 116 | } |
| 117 | |
| 118 | /* |
| 119 | * Release a peer group ID |
| 120 | */ |
| 121 | void mnt_release_group_id(struct mount *mnt) |
| 122 | { |
| 123 | int id = mnt->mnt_group_id; |
| 124 | ida_remove(&mnt_group_ida, id); |
| 125 | if (mnt_group_start > id) |
| 126 | mnt_group_start = id; |
| 127 | mnt->mnt_group_id = 0; |
| 128 | } |
| 129 | |
| 130 | /* |
| 131 | * vfsmount lock must be held for read |
| 132 | */ |
| 133 | static inline void mnt_add_count(struct mount *mnt, int n) |
| 134 | { |
| 135 | #ifdef CONFIG_SMP |
| 136 | this_cpu_add(mnt->mnt_pcp->mnt_count, n); |
| 137 | #else |
| 138 | preempt_disable(); |
| 139 | mnt->mnt_count += n; |
| 140 | preempt_enable(); |
| 141 | #endif |
| 142 | } |
| 143 | |
| 144 | /* |
| 145 | * vfsmount lock must be held for write |
| 146 | */ |
| 147 | unsigned int mnt_get_count(struct mount *mnt) |
| 148 | { |
| 149 | #ifdef CONFIG_SMP |
| 150 | unsigned int count = 0; |
| 151 | int cpu; |
| 152 | |
| 153 | for_each_possible_cpu(cpu) { |
| 154 | count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count; |
| 155 | } |
| 156 | |
| 157 | return count; |
| 158 | #else |
| 159 | return mnt->mnt_count; |
| 160 | #endif |
| 161 | } |
| 162 | |
| 163 | static struct mount *alloc_vfsmnt(const char *name) |
| 164 | { |
| 165 | struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); |
| 166 | if (mnt) { |
| 167 | int err; |
| 168 | |
| 169 | err = mnt_alloc_id(mnt); |
| 170 | if (err) |
| 171 | goto out_free_cache; |
| 172 | |
| 173 | if (name) { |
| 174 | mnt->mnt_devname = kstrdup(name, GFP_KERNEL); |
| 175 | if (!mnt->mnt_devname) |
| 176 | goto out_free_id; |
| 177 | } |
| 178 | |
| 179 | #ifdef CONFIG_SMP |
| 180 | mnt->mnt_pcp = alloc_percpu(struct mnt_pcp); |
| 181 | if (!mnt->mnt_pcp) |
| 182 | goto out_free_devname; |
| 183 | |
| 184 | this_cpu_add(mnt->mnt_pcp->mnt_count, 1); |
| 185 | #else |
| 186 | mnt->mnt_count = 1; |
| 187 | mnt->mnt_writers = 0; |
| 188 | #endif |
| 189 | |
| 190 | INIT_LIST_HEAD(&mnt->mnt_hash); |
| 191 | INIT_LIST_HEAD(&mnt->mnt_child); |
| 192 | INIT_LIST_HEAD(&mnt->mnt_mounts); |
| 193 | INIT_LIST_HEAD(&mnt->mnt_list); |
| 194 | INIT_LIST_HEAD(&mnt->mnt_expire); |
| 195 | INIT_LIST_HEAD(&mnt->mnt_share); |
| 196 | INIT_LIST_HEAD(&mnt->mnt_slave_list); |
| 197 | INIT_LIST_HEAD(&mnt->mnt_slave); |
| 198 | #ifdef CONFIG_FSNOTIFY |
| 199 | INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks); |
| 200 | #endif |
| 201 | } |
| 202 | return mnt; |
| 203 | |
| 204 | #ifdef CONFIG_SMP |
| 205 | out_free_devname: |
| 206 | kfree(mnt->mnt_devname); |
| 207 | #endif |
| 208 | out_free_id: |
| 209 | mnt_free_id(mnt); |
| 210 | out_free_cache: |
| 211 | kmem_cache_free(mnt_cache, mnt); |
| 212 | return NULL; |
| 213 | } |
| 214 | |
| 215 | /* |
| 216 | * Most r/o checks on a fs are for operations that take |
| 217 | * discrete amounts of time, like a write() or unlink(). |
| 218 | * We must keep track of when those operations start |
| 219 | * (for permission checks) and when they end, so that |
| 220 | * we can determine when writes are able to occur to |
| 221 | * a filesystem. |
| 222 | */ |
| 223 | /* |
| 224 | * __mnt_is_readonly: check whether a mount is read-only |
| 225 | * @mnt: the mount to check for its write status |
| 226 | * |
| 227 | * This shouldn't be used directly ouside of the VFS. |
| 228 | * It does not guarantee that the filesystem will stay |
| 229 | * r/w, just that it is right *now*. This can not and |
| 230 | * should not be used in place of IS_RDONLY(inode). |
| 231 | * mnt_want/drop_write() will _keep_ the filesystem |
| 232 | * r/w. |
| 233 | */ |
| 234 | int __mnt_is_readonly(struct vfsmount *mnt) |
| 235 | { |
| 236 | if (mnt->mnt_flags & MNT_READONLY) |
| 237 | return 1; |
| 238 | if (mnt->mnt_sb->s_flags & MS_RDONLY) |
| 239 | return 1; |
| 240 | return 0; |
| 241 | } |
| 242 | EXPORT_SYMBOL_GPL(__mnt_is_readonly); |
| 243 | |
| 244 | static inline void mnt_inc_writers(struct mount *mnt) |
| 245 | { |
| 246 | #ifdef CONFIG_SMP |
| 247 | this_cpu_inc(mnt->mnt_pcp->mnt_writers); |
| 248 | #else |
| 249 | mnt->mnt_writers++; |
| 250 | #endif |
| 251 | } |
| 252 | |
| 253 | static inline void mnt_dec_writers(struct mount *mnt) |
| 254 | { |
| 255 | #ifdef CONFIG_SMP |
| 256 | this_cpu_dec(mnt->mnt_pcp->mnt_writers); |
| 257 | #else |
| 258 | mnt->mnt_writers--; |
| 259 | #endif |
| 260 | } |
| 261 | |
| 262 | static unsigned int mnt_get_writers(struct mount *mnt) |
| 263 | { |
| 264 | #ifdef CONFIG_SMP |
| 265 | unsigned int count = 0; |
| 266 | int cpu; |
| 267 | |
| 268 | for_each_possible_cpu(cpu) { |
| 269 | count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers; |
| 270 | } |
| 271 | |
| 272 | return count; |
| 273 | #else |
| 274 | return mnt->mnt_writers; |
| 275 | #endif |
| 276 | } |
| 277 | |
| 278 | static int mnt_is_readonly(struct vfsmount *mnt) |
| 279 | { |
| 280 | if (mnt->mnt_sb->s_readonly_remount) |
| 281 | return 1; |
| 282 | /* Order wrt setting s_flags/s_readonly_remount in do_remount() */ |
| 283 | smp_rmb(); |
| 284 | return __mnt_is_readonly(mnt); |
| 285 | } |
| 286 | |
| 287 | /* |
| 288 | * Most r/o & frozen checks on a fs are for operations that take discrete |
| 289 | * amounts of time, like a write() or unlink(). We must keep track of when |
| 290 | * those operations start (for permission checks) and when they end, so that we |
| 291 | * can determine when writes are able to occur to a filesystem. |
| 292 | */ |
| 293 | /** |
| 294 | * __mnt_want_write - get write access to a mount without freeze protection |
| 295 | * @m: the mount on which to take a write |
| 296 | * |
| 297 | * This tells the low-level filesystem that a write is about to be performed to |
| 298 | * it, and makes sure that writes are allowed (mnt it read-write) before |
| 299 | * returning success. This operation does not protect against filesystem being |
| 300 | * frozen. When the write operation is finished, __mnt_drop_write() must be |
| 301 | * called. This is effectively a refcount. |
| 302 | */ |
| 303 | int __mnt_want_write(struct vfsmount *m) |
| 304 | { |
| 305 | struct mount *mnt = real_mount(m); |
| 306 | int ret = 0; |
| 307 | |
| 308 | preempt_disable(); |
| 309 | mnt_inc_writers(mnt); |
| 310 | /* |
| 311 | * The store to mnt_inc_writers must be visible before we pass |
| 312 | * MNT_WRITE_HOLD loop below, so that the slowpath can see our |
| 313 | * incremented count after it has set MNT_WRITE_HOLD. |
| 314 | */ |
| 315 | smp_mb(); |
| 316 | while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) |
| 317 | cpu_relax(); |
| 318 | /* |
| 319 | * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will |
| 320 | * be set to match its requirements. So we must not load that until |
| 321 | * MNT_WRITE_HOLD is cleared. |
| 322 | */ |
| 323 | smp_rmb(); |
| 324 | if (mnt_is_readonly(m)) { |
| 325 | mnt_dec_writers(mnt); |
| 326 | ret = -EROFS; |
| 327 | } |
| 328 | preempt_enable(); |
| 329 | |
| 330 | return ret; |
| 331 | } |
| 332 | |
| 333 | /** |
| 334 | * mnt_want_write - get write access to a mount |
| 335 | * @m: the mount on which to take a write |
| 336 | * |
| 337 | * This tells the low-level filesystem that a write is about to be performed to |
| 338 | * it, and makes sure that writes are allowed (mount is read-write, filesystem |
| 339 | * is not frozen) before returning success. When the write operation is |
| 340 | * finished, mnt_drop_write() must be called. This is effectively a refcount. |
| 341 | */ |
| 342 | int mnt_want_write(struct vfsmount *m) |
| 343 | { |
| 344 | int ret; |
| 345 | |
| 346 | sb_start_write(m->mnt_sb); |
| 347 | ret = __mnt_want_write(m); |
| 348 | if (ret) |
| 349 | sb_end_write(m->mnt_sb); |
| 350 | return ret; |
| 351 | } |
| 352 | EXPORT_SYMBOL_GPL(mnt_want_write); |
| 353 | |
| 354 | /** |
| 355 | * mnt_clone_write - get write access to a mount |
| 356 | * @mnt: the mount on which to take a write |
| 357 | * |
| 358 | * This is effectively like mnt_want_write, except |
| 359 | * it must only be used to take an extra write reference |
| 360 | * on a mountpoint that we already know has a write reference |
| 361 | * on it. This allows some optimisation. |
| 362 | * |
| 363 | * After finished, mnt_drop_write must be called as usual to |
| 364 | * drop the reference. |
| 365 | */ |
| 366 | int mnt_clone_write(struct vfsmount *mnt) |
| 367 | { |
| 368 | /* superblock may be r/o */ |
| 369 | if (__mnt_is_readonly(mnt)) |
| 370 | return -EROFS; |
| 371 | preempt_disable(); |
| 372 | mnt_inc_writers(real_mount(mnt)); |
| 373 | preempt_enable(); |
| 374 | return 0; |
| 375 | } |
| 376 | EXPORT_SYMBOL_GPL(mnt_clone_write); |
| 377 | |
| 378 | /** |
| 379 | * __mnt_want_write_file - get write access to a file's mount |
| 380 | * @file: the file who's mount on which to take a write |
| 381 | * |
| 382 | * This is like __mnt_want_write, but it takes a file and can |
| 383 | * do some optimisations if the file is open for write already |
| 384 | */ |
| 385 | int __mnt_want_write_file(struct file *file) |
| 386 | { |
| 387 | struct inode *inode = file_inode(file); |
| 388 | |
| 389 | if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode)) |
| 390 | return __mnt_want_write(file->f_path.mnt); |
| 391 | else |
| 392 | return mnt_clone_write(file->f_path.mnt); |
| 393 | } |
| 394 | |
| 395 | /** |
| 396 | * mnt_want_write_file - get write access to a file's mount |
| 397 | * @file: the file who's mount on which to take a write |
| 398 | * |
| 399 | * This is like mnt_want_write, but it takes a file and can |
| 400 | * do some optimisations if the file is open for write already |
| 401 | */ |
| 402 | int mnt_want_write_file(struct file *file) |
| 403 | { |
| 404 | int ret; |
| 405 | |
| 406 | sb_start_write(file->f_path.mnt->mnt_sb); |
| 407 | ret = __mnt_want_write_file(file); |
| 408 | if (ret) |
| 409 | sb_end_write(file->f_path.mnt->mnt_sb); |
| 410 | return ret; |
| 411 | } |
| 412 | EXPORT_SYMBOL_GPL(mnt_want_write_file); |
| 413 | |
| 414 | /** |
| 415 | * __mnt_drop_write - give up write access to a mount |
| 416 | * @mnt: the mount on which to give up write access |
| 417 | * |
| 418 | * Tells the low-level filesystem that we are done |
| 419 | * performing writes to it. Must be matched with |
| 420 | * __mnt_want_write() call above. |
| 421 | */ |
| 422 | void __mnt_drop_write(struct vfsmount *mnt) |
| 423 | { |
| 424 | preempt_disable(); |
| 425 | mnt_dec_writers(real_mount(mnt)); |
| 426 | preempt_enable(); |
| 427 | } |
| 428 | |
| 429 | /** |
| 430 | * mnt_drop_write - give up write access to a mount |
| 431 | * @mnt: the mount on which to give up write access |
| 432 | * |
| 433 | * Tells the low-level filesystem that we are done performing writes to it and |
| 434 | * also allows filesystem to be frozen again. Must be matched with |
| 435 | * mnt_want_write() call above. |
| 436 | */ |
| 437 | void mnt_drop_write(struct vfsmount *mnt) |
| 438 | { |
| 439 | __mnt_drop_write(mnt); |
| 440 | sb_end_write(mnt->mnt_sb); |
| 441 | } |
| 442 | EXPORT_SYMBOL_GPL(mnt_drop_write); |
| 443 | |
| 444 | void __mnt_drop_write_file(struct file *file) |
| 445 | { |
| 446 | __mnt_drop_write(file->f_path.mnt); |
| 447 | } |
| 448 | |
| 449 | void mnt_drop_write_file(struct file *file) |
| 450 | { |
| 451 | mnt_drop_write(file->f_path.mnt); |
| 452 | } |
| 453 | EXPORT_SYMBOL(mnt_drop_write_file); |
| 454 | |
| 455 | static int mnt_make_readonly(struct mount *mnt) |
| 456 | { |
| 457 | int ret = 0; |
| 458 | |
| 459 | lock_mount_hash(); |
| 460 | mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; |
| 461 | /* |
| 462 | * After storing MNT_WRITE_HOLD, we'll read the counters. This store |
| 463 | * should be visible before we do. |
| 464 | */ |
| 465 | smp_mb(); |
| 466 | |
| 467 | /* |
| 468 | * With writers on hold, if this value is zero, then there are |
| 469 | * definitely no active writers (although held writers may subsequently |
| 470 | * increment the count, they'll have to wait, and decrement it after |
| 471 | * seeing MNT_READONLY). |
| 472 | * |
| 473 | * It is OK to have counter incremented on one CPU and decremented on |
| 474 | * another: the sum will add up correctly. The danger would be when we |
| 475 | * sum up each counter, if we read a counter before it is incremented, |
| 476 | * but then read another CPU's count which it has been subsequently |
| 477 | * decremented from -- we would see more decrements than we should. |
| 478 | * MNT_WRITE_HOLD protects against this scenario, because |
| 479 | * mnt_want_write first increments count, then smp_mb, then spins on |
| 480 | * MNT_WRITE_HOLD, so it can't be decremented by another CPU while |
| 481 | * we're counting up here. |
| 482 | */ |
| 483 | if (mnt_get_writers(mnt) > 0) |
| 484 | ret = -EBUSY; |
| 485 | else |
| 486 | mnt->mnt.mnt_flags |= MNT_READONLY; |
| 487 | /* |
| 488 | * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers |
| 489 | * that become unheld will see MNT_READONLY. |
| 490 | */ |
| 491 | smp_wmb(); |
| 492 | mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; |
| 493 | unlock_mount_hash(); |
| 494 | return ret; |
| 495 | } |
| 496 | |
| 497 | static void __mnt_unmake_readonly(struct mount *mnt) |
| 498 | { |
| 499 | lock_mount_hash(); |
| 500 | mnt->mnt.mnt_flags &= ~MNT_READONLY; |
| 501 | unlock_mount_hash(); |
| 502 | } |
| 503 | |
| 504 | int sb_prepare_remount_readonly(struct super_block *sb) |
| 505 | { |
| 506 | struct mount *mnt; |
| 507 | int err = 0; |
| 508 | |
| 509 | /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */ |
| 510 | if (atomic_long_read(&sb->s_remove_count)) |
| 511 | return -EBUSY; |
| 512 | |
| 513 | lock_mount_hash(); |
| 514 | list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { |
| 515 | if (!(mnt->mnt.mnt_flags & MNT_READONLY)) { |
| 516 | mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; |
| 517 | smp_mb(); |
| 518 | if (mnt_get_writers(mnt) > 0) { |
| 519 | err = -EBUSY; |
| 520 | break; |
| 521 | } |
| 522 | } |
| 523 | } |
| 524 | if (!err && atomic_long_read(&sb->s_remove_count)) |
| 525 | err = -EBUSY; |
| 526 | |
| 527 | if (!err) { |
| 528 | sb->s_readonly_remount = 1; |
| 529 | smp_wmb(); |
| 530 | } |
| 531 | list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { |
| 532 | if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD) |
| 533 | mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; |
| 534 | } |
| 535 | unlock_mount_hash(); |
| 536 | |
| 537 | return err; |
| 538 | } |
| 539 | |
| 540 | static void free_vfsmnt(struct mount *mnt) |
| 541 | { |
| 542 | kfree(mnt->mnt_devname); |
| 543 | mnt_free_id(mnt); |
| 544 | #ifdef CONFIG_SMP |
| 545 | free_percpu(mnt->mnt_pcp); |
| 546 | #endif |
| 547 | kmem_cache_free(mnt_cache, mnt); |
| 548 | } |
| 549 | |
| 550 | /* call under rcu_read_lock */ |
| 551 | bool legitimize_mnt(struct vfsmount *bastard, unsigned seq) |
| 552 | { |
| 553 | struct mount *mnt; |
| 554 | if (read_seqretry(&mount_lock, seq)) |
| 555 | return false; |
| 556 | if (bastard == NULL) |
| 557 | return true; |
| 558 | mnt = real_mount(bastard); |
| 559 | mnt_add_count(mnt, 1); |
| 560 | if (likely(!read_seqretry(&mount_lock, seq))) |
| 561 | return true; |
| 562 | if (bastard->mnt_flags & MNT_SYNC_UMOUNT) { |
| 563 | mnt_add_count(mnt, -1); |
| 564 | return false; |
| 565 | } |
| 566 | rcu_read_unlock(); |
| 567 | mntput(bastard); |
| 568 | rcu_read_lock(); |
| 569 | return false; |
| 570 | } |
| 571 | |
| 572 | /* |
| 573 | * find the first mount at @dentry on vfsmount @mnt. |
| 574 | * call under rcu_read_lock() |
| 575 | */ |
| 576 | struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry) |
| 577 | { |
| 578 | struct list_head *head = mount_hashtable + hash(mnt, dentry); |
| 579 | struct mount *p; |
| 580 | |
| 581 | list_for_each_entry_rcu(p, head, mnt_hash) |
| 582 | if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) |
| 583 | return p; |
| 584 | return NULL; |
| 585 | } |
| 586 | |
| 587 | /* |
| 588 | * find the last mount at @dentry on vfsmount @mnt. |
| 589 | * mount_lock must be held. |
| 590 | */ |
| 591 | struct mount *__lookup_mnt_last(struct vfsmount *mnt, struct dentry *dentry) |
| 592 | { |
| 593 | struct list_head *head = mount_hashtable + hash(mnt, dentry); |
| 594 | struct mount *p; |
| 595 | |
| 596 | list_for_each_entry_reverse(p, head, mnt_hash) |
| 597 | if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) |
| 598 | return p; |
| 599 | return NULL; |
| 600 | } |
| 601 | |
| 602 | /* |
| 603 | * lookup_mnt - Return the first child mount mounted at path |
| 604 | * |
| 605 | * "First" means first mounted chronologically. If you create the |
| 606 | * following mounts: |
| 607 | * |
| 608 | * mount /dev/sda1 /mnt |
| 609 | * mount /dev/sda2 /mnt |
| 610 | * mount /dev/sda3 /mnt |
| 611 | * |
| 612 | * Then lookup_mnt() on the base /mnt dentry in the root mount will |
| 613 | * return successively the root dentry and vfsmount of /dev/sda1, then |
| 614 | * /dev/sda2, then /dev/sda3, then NULL. |
| 615 | * |
| 616 | * lookup_mnt takes a reference to the found vfsmount. |
| 617 | */ |
| 618 | struct vfsmount *lookup_mnt(struct path *path) |
| 619 | { |
| 620 | struct mount *child_mnt; |
| 621 | struct vfsmount *m; |
| 622 | unsigned seq; |
| 623 | |
| 624 | rcu_read_lock(); |
| 625 | do { |
| 626 | seq = read_seqbegin(&mount_lock); |
| 627 | child_mnt = __lookup_mnt(path->mnt, path->dentry); |
| 628 | m = child_mnt ? &child_mnt->mnt : NULL; |
| 629 | } while (!legitimize_mnt(m, seq)); |
| 630 | rcu_read_unlock(); |
| 631 | return m; |
| 632 | } |
| 633 | |
| 634 | static struct mountpoint *new_mountpoint(struct dentry *dentry) |
| 635 | { |
| 636 | struct list_head *chain = mountpoint_hashtable + hash(NULL, dentry); |
| 637 | struct mountpoint *mp; |
| 638 | int ret; |
| 639 | |
| 640 | list_for_each_entry(mp, chain, m_hash) { |
| 641 | if (mp->m_dentry == dentry) { |
| 642 | /* might be worth a WARN_ON() */ |
| 643 | if (d_unlinked(dentry)) |
| 644 | return ERR_PTR(-ENOENT); |
| 645 | mp->m_count++; |
| 646 | return mp; |
| 647 | } |
| 648 | } |
| 649 | |
| 650 | mp = kmalloc(sizeof(struct mountpoint), GFP_KERNEL); |
| 651 | if (!mp) |
| 652 | return ERR_PTR(-ENOMEM); |
| 653 | |
| 654 | ret = d_set_mounted(dentry); |
| 655 | if (ret) { |
| 656 | kfree(mp); |
| 657 | return ERR_PTR(ret); |
| 658 | } |
| 659 | |
| 660 | mp->m_dentry = dentry; |
| 661 | mp->m_count = 1; |
| 662 | list_add(&mp->m_hash, chain); |
| 663 | return mp; |
| 664 | } |
| 665 | |
| 666 | static void put_mountpoint(struct mountpoint *mp) |
| 667 | { |
| 668 | if (!--mp->m_count) { |
| 669 | struct dentry *dentry = mp->m_dentry; |
| 670 | spin_lock(&dentry->d_lock); |
| 671 | dentry->d_flags &= ~DCACHE_MOUNTED; |
| 672 | spin_unlock(&dentry->d_lock); |
| 673 | list_del(&mp->m_hash); |
| 674 | kfree(mp); |
| 675 | } |
| 676 | } |
| 677 | |
| 678 | static inline int check_mnt(struct mount *mnt) |
| 679 | { |
| 680 | return mnt->mnt_ns == current->nsproxy->mnt_ns; |
| 681 | } |
| 682 | |
| 683 | /* |
| 684 | * vfsmount lock must be held for write |
| 685 | */ |
| 686 | static void touch_mnt_namespace(struct mnt_namespace *ns) |
| 687 | { |
| 688 | if (ns) { |
| 689 | ns->event = ++event; |
| 690 | wake_up_interruptible(&ns->poll); |
| 691 | } |
| 692 | } |
| 693 | |
| 694 | /* |
| 695 | * vfsmount lock must be held for write |
| 696 | */ |
| 697 | static void __touch_mnt_namespace(struct mnt_namespace *ns) |
| 698 | { |
| 699 | if (ns && ns->event != event) { |
| 700 | ns->event = event; |
| 701 | wake_up_interruptible(&ns->poll); |
| 702 | } |
| 703 | } |
| 704 | |
| 705 | /* |
| 706 | * vfsmount lock must be held for write |
| 707 | */ |
| 708 | static void detach_mnt(struct mount *mnt, struct path *old_path) |
| 709 | { |
| 710 | old_path->dentry = mnt->mnt_mountpoint; |
| 711 | old_path->mnt = &mnt->mnt_parent->mnt; |
| 712 | mnt->mnt_parent = mnt; |
| 713 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
| 714 | list_del_init(&mnt->mnt_child); |
| 715 | list_del_init(&mnt->mnt_hash); |
| 716 | put_mountpoint(mnt->mnt_mp); |
| 717 | mnt->mnt_mp = NULL; |
| 718 | } |
| 719 | |
| 720 | /* |
| 721 | * vfsmount lock must be held for write |
| 722 | */ |
| 723 | void mnt_set_mountpoint(struct mount *mnt, |
| 724 | struct mountpoint *mp, |
| 725 | struct mount *child_mnt) |
| 726 | { |
| 727 | mp->m_count++; |
| 728 | mnt_add_count(mnt, 1); /* essentially, that's mntget */ |
| 729 | child_mnt->mnt_mountpoint = dget(mp->m_dentry); |
| 730 | child_mnt->mnt_parent = mnt; |
| 731 | child_mnt->mnt_mp = mp; |
| 732 | } |
| 733 | |
| 734 | /* |
| 735 | * vfsmount lock must be held for write |
| 736 | */ |
| 737 | static void attach_mnt(struct mount *mnt, |
| 738 | struct mount *parent, |
| 739 | struct mountpoint *mp) |
| 740 | { |
| 741 | mnt_set_mountpoint(parent, mp, mnt); |
| 742 | list_add_tail(&mnt->mnt_hash, mount_hashtable + |
| 743 | hash(&parent->mnt, mp->m_dentry)); |
| 744 | list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); |
| 745 | } |
| 746 | |
| 747 | /* |
| 748 | * vfsmount lock must be held for write |
| 749 | */ |
| 750 | static void commit_tree(struct mount *mnt) |
| 751 | { |
| 752 | struct mount *parent = mnt->mnt_parent; |
| 753 | struct mount *m; |
| 754 | LIST_HEAD(head); |
| 755 | struct mnt_namespace *n = parent->mnt_ns; |
| 756 | |
| 757 | BUG_ON(parent == mnt); |
| 758 | |
| 759 | list_add_tail(&head, &mnt->mnt_list); |
| 760 | list_for_each_entry(m, &head, mnt_list) |
| 761 | m->mnt_ns = n; |
| 762 | |
| 763 | list_splice(&head, n->list.prev); |
| 764 | |
| 765 | list_add_tail(&mnt->mnt_hash, mount_hashtable + |
| 766 | hash(&parent->mnt, mnt->mnt_mountpoint)); |
| 767 | list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); |
| 768 | touch_mnt_namespace(n); |
| 769 | } |
| 770 | |
| 771 | static struct mount *next_mnt(struct mount *p, struct mount *root) |
| 772 | { |
| 773 | struct list_head *next = p->mnt_mounts.next; |
| 774 | if (next == &p->mnt_mounts) { |
| 775 | while (1) { |
| 776 | if (p == root) |
| 777 | return NULL; |
| 778 | next = p->mnt_child.next; |
| 779 | if (next != &p->mnt_parent->mnt_mounts) |
| 780 | break; |
| 781 | p = p->mnt_parent; |
| 782 | } |
| 783 | } |
| 784 | return list_entry(next, struct mount, mnt_child); |
| 785 | } |
| 786 | |
| 787 | static struct mount *skip_mnt_tree(struct mount *p) |
| 788 | { |
| 789 | struct list_head *prev = p->mnt_mounts.prev; |
| 790 | while (prev != &p->mnt_mounts) { |
| 791 | p = list_entry(prev, struct mount, mnt_child); |
| 792 | prev = p->mnt_mounts.prev; |
| 793 | } |
| 794 | return p; |
| 795 | } |
| 796 | |
| 797 | struct vfsmount * |
| 798 | vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data) |
| 799 | { |
| 800 | struct mount *mnt; |
| 801 | struct dentry *root; |
| 802 | |
| 803 | if (!type) |
| 804 | return ERR_PTR(-ENODEV); |
| 805 | |
| 806 | mnt = alloc_vfsmnt(name); |
| 807 | if (!mnt) |
| 808 | return ERR_PTR(-ENOMEM); |
| 809 | |
| 810 | if (flags & MS_KERNMOUNT) |
| 811 | mnt->mnt.mnt_flags = MNT_INTERNAL; |
| 812 | |
| 813 | root = mount_fs(type, flags, name, data); |
| 814 | if (IS_ERR(root)) { |
| 815 | free_vfsmnt(mnt); |
| 816 | return ERR_CAST(root); |
| 817 | } |
| 818 | |
| 819 | mnt->mnt.mnt_root = root; |
| 820 | mnt->mnt.mnt_sb = root->d_sb; |
| 821 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
| 822 | mnt->mnt_parent = mnt; |
| 823 | lock_mount_hash(); |
| 824 | list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts); |
| 825 | unlock_mount_hash(); |
| 826 | return &mnt->mnt; |
| 827 | } |
| 828 | EXPORT_SYMBOL_GPL(vfs_kern_mount); |
| 829 | |
| 830 | static struct mount *clone_mnt(struct mount *old, struct dentry *root, |
| 831 | int flag) |
| 832 | { |
| 833 | struct super_block *sb = old->mnt.mnt_sb; |
| 834 | struct mount *mnt; |
| 835 | int err; |
| 836 | |
| 837 | mnt = alloc_vfsmnt(old->mnt_devname); |
| 838 | if (!mnt) |
| 839 | return ERR_PTR(-ENOMEM); |
| 840 | |
| 841 | if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE)) |
| 842 | mnt->mnt_group_id = 0; /* not a peer of original */ |
| 843 | else |
| 844 | mnt->mnt_group_id = old->mnt_group_id; |
| 845 | |
| 846 | if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { |
| 847 | err = mnt_alloc_group_id(mnt); |
| 848 | if (err) |
| 849 | goto out_free; |
| 850 | } |
| 851 | |
| 852 | mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD; |
| 853 | /* Don't allow unprivileged users to change mount flags */ |
| 854 | if ((flag & CL_UNPRIVILEGED) && (mnt->mnt.mnt_flags & MNT_READONLY)) |
| 855 | mnt->mnt.mnt_flags |= MNT_LOCK_READONLY; |
| 856 | |
| 857 | /* Don't allow unprivileged users to reveal what is under a mount */ |
| 858 | if ((flag & CL_UNPRIVILEGED) && list_empty(&old->mnt_expire)) |
| 859 | mnt->mnt.mnt_flags |= MNT_LOCKED; |
| 860 | |
| 861 | atomic_inc(&sb->s_active); |
| 862 | mnt->mnt.mnt_sb = sb; |
| 863 | mnt->mnt.mnt_root = dget(root); |
| 864 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
| 865 | mnt->mnt_parent = mnt; |
| 866 | lock_mount_hash(); |
| 867 | list_add_tail(&mnt->mnt_instance, &sb->s_mounts); |
| 868 | unlock_mount_hash(); |
| 869 | |
| 870 | if ((flag & CL_SLAVE) || |
| 871 | ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) { |
| 872 | list_add(&mnt->mnt_slave, &old->mnt_slave_list); |
| 873 | mnt->mnt_master = old; |
| 874 | CLEAR_MNT_SHARED(mnt); |
| 875 | } else if (!(flag & CL_PRIVATE)) { |
| 876 | if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old)) |
| 877 | list_add(&mnt->mnt_share, &old->mnt_share); |
| 878 | if (IS_MNT_SLAVE(old)) |
| 879 | list_add(&mnt->mnt_slave, &old->mnt_slave); |
| 880 | mnt->mnt_master = old->mnt_master; |
| 881 | } |
| 882 | if (flag & CL_MAKE_SHARED) |
| 883 | set_mnt_shared(mnt); |
| 884 | |
| 885 | /* stick the duplicate mount on the same expiry list |
| 886 | * as the original if that was on one */ |
| 887 | if (flag & CL_EXPIRE) { |
| 888 | if (!list_empty(&old->mnt_expire)) |
| 889 | list_add(&mnt->mnt_expire, &old->mnt_expire); |
| 890 | } |
| 891 | |
| 892 | return mnt; |
| 893 | |
| 894 | out_free: |
| 895 | free_vfsmnt(mnt); |
| 896 | return ERR_PTR(err); |
| 897 | } |
| 898 | |
| 899 | static void delayed_free(struct rcu_head *head) |
| 900 | { |
| 901 | struct mount *mnt = container_of(head, struct mount, mnt_rcu); |
| 902 | kfree(mnt->mnt_devname); |
| 903 | #ifdef CONFIG_SMP |
| 904 | free_percpu(mnt->mnt_pcp); |
| 905 | #endif |
| 906 | kmem_cache_free(mnt_cache, mnt); |
| 907 | } |
| 908 | |
| 909 | static void mntput_no_expire(struct mount *mnt) |
| 910 | { |
| 911 | put_again: |
| 912 | rcu_read_lock(); |
| 913 | mnt_add_count(mnt, -1); |
| 914 | if (likely(mnt->mnt_ns)) { /* shouldn't be the last one */ |
| 915 | rcu_read_unlock(); |
| 916 | return; |
| 917 | } |
| 918 | lock_mount_hash(); |
| 919 | if (mnt_get_count(mnt)) { |
| 920 | rcu_read_unlock(); |
| 921 | unlock_mount_hash(); |
| 922 | return; |
| 923 | } |
| 924 | if (unlikely(mnt->mnt_pinned)) { |
| 925 | mnt_add_count(mnt, mnt->mnt_pinned + 1); |
| 926 | mnt->mnt_pinned = 0; |
| 927 | rcu_read_unlock(); |
| 928 | unlock_mount_hash(); |
| 929 | acct_auto_close_mnt(&mnt->mnt); |
| 930 | goto put_again; |
| 931 | } |
| 932 | if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) { |
| 933 | rcu_read_unlock(); |
| 934 | unlock_mount_hash(); |
| 935 | return; |
| 936 | } |
| 937 | mnt->mnt.mnt_flags |= MNT_DOOMED; |
| 938 | rcu_read_unlock(); |
| 939 | |
| 940 | list_del(&mnt->mnt_instance); |
| 941 | unlock_mount_hash(); |
| 942 | |
| 943 | /* |
| 944 | * This probably indicates that somebody messed |
| 945 | * up a mnt_want/drop_write() pair. If this |
| 946 | * happens, the filesystem was probably unable |
| 947 | * to make r/w->r/o transitions. |
| 948 | */ |
| 949 | /* |
| 950 | * The locking used to deal with mnt_count decrement provides barriers, |
| 951 | * so mnt_get_writers() below is safe. |
| 952 | */ |
| 953 | WARN_ON(mnt_get_writers(mnt)); |
| 954 | fsnotify_vfsmount_delete(&mnt->mnt); |
| 955 | dput(mnt->mnt.mnt_root); |
| 956 | deactivate_super(mnt->mnt.mnt_sb); |
| 957 | mnt_free_id(mnt); |
| 958 | call_rcu(&mnt->mnt_rcu, delayed_free); |
| 959 | } |
| 960 | |
| 961 | void mntput(struct vfsmount *mnt) |
| 962 | { |
| 963 | if (mnt) { |
| 964 | struct mount *m = real_mount(mnt); |
| 965 | /* avoid cacheline pingpong, hope gcc doesn't get "smart" */ |
| 966 | if (unlikely(m->mnt_expiry_mark)) |
| 967 | m->mnt_expiry_mark = 0; |
| 968 | mntput_no_expire(m); |
| 969 | } |
| 970 | } |
| 971 | EXPORT_SYMBOL(mntput); |
| 972 | |
| 973 | struct vfsmount *mntget(struct vfsmount *mnt) |
| 974 | { |
| 975 | if (mnt) |
| 976 | mnt_add_count(real_mount(mnt), 1); |
| 977 | return mnt; |
| 978 | } |
| 979 | EXPORT_SYMBOL(mntget); |
| 980 | |
| 981 | void mnt_pin(struct vfsmount *mnt) |
| 982 | { |
| 983 | lock_mount_hash(); |
| 984 | real_mount(mnt)->mnt_pinned++; |
| 985 | unlock_mount_hash(); |
| 986 | } |
| 987 | EXPORT_SYMBOL(mnt_pin); |
| 988 | |
| 989 | void mnt_unpin(struct vfsmount *m) |
| 990 | { |
| 991 | struct mount *mnt = real_mount(m); |
| 992 | lock_mount_hash(); |
| 993 | if (mnt->mnt_pinned) { |
| 994 | mnt_add_count(mnt, 1); |
| 995 | mnt->mnt_pinned--; |
| 996 | } |
| 997 | unlock_mount_hash(); |
| 998 | } |
| 999 | EXPORT_SYMBOL(mnt_unpin); |
| 1000 | |
| 1001 | static inline void mangle(struct seq_file *m, const char *s) |
| 1002 | { |
| 1003 | seq_escape(m, s, " \t\n\\"); |
| 1004 | } |
| 1005 | |
| 1006 | /* |
| 1007 | * Simple .show_options callback for filesystems which don't want to |
| 1008 | * implement more complex mount option showing. |
| 1009 | * |
| 1010 | * See also save_mount_options(). |
| 1011 | */ |
| 1012 | int generic_show_options(struct seq_file *m, struct dentry *root) |
| 1013 | { |
| 1014 | const char *options; |
| 1015 | |
| 1016 | rcu_read_lock(); |
| 1017 | options = rcu_dereference(root->d_sb->s_options); |
| 1018 | |
| 1019 | if (options != NULL && options[0]) { |
| 1020 | seq_putc(m, ','); |
| 1021 | mangle(m, options); |
| 1022 | } |
| 1023 | rcu_read_unlock(); |
| 1024 | |
| 1025 | return 0; |
| 1026 | } |
| 1027 | EXPORT_SYMBOL(generic_show_options); |
| 1028 | |
| 1029 | /* |
| 1030 | * If filesystem uses generic_show_options(), this function should be |
| 1031 | * called from the fill_super() callback. |
| 1032 | * |
| 1033 | * The .remount_fs callback usually needs to be handled in a special |
| 1034 | * way, to make sure, that previous options are not overwritten if the |
| 1035 | * remount fails. |
| 1036 | * |
| 1037 | * Also note, that if the filesystem's .remount_fs function doesn't |
| 1038 | * reset all options to their default value, but changes only newly |
| 1039 | * given options, then the displayed options will not reflect reality |
| 1040 | * any more. |
| 1041 | */ |
| 1042 | void save_mount_options(struct super_block *sb, char *options) |
| 1043 | { |
| 1044 | BUG_ON(sb->s_options); |
| 1045 | rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL)); |
| 1046 | } |
| 1047 | EXPORT_SYMBOL(save_mount_options); |
| 1048 | |
| 1049 | void replace_mount_options(struct super_block *sb, char *options) |
| 1050 | { |
| 1051 | char *old = sb->s_options; |
| 1052 | rcu_assign_pointer(sb->s_options, options); |
| 1053 | if (old) { |
| 1054 | synchronize_rcu(); |
| 1055 | kfree(old); |
| 1056 | } |
| 1057 | } |
| 1058 | EXPORT_SYMBOL(replace_mount_options); |
| 1059 | |
| 1060 | #ifdef CONFIG_PROC_FS |
| 1061 | /* iterator; we want it to have access to namespace_sem, thus here... */ |
| 1062 | static void *m_start(struct seq_file *m, loff_t *pos) |
| 1063 | { |
| 1064 | struct proc_mounts *p = proc_mounts(m); |
| 1065 | |
| 1066 | down_read(&namespace_sem); |
| 1067 | return seq_list_start(&p->ns->list, *pos); |
| 1068 | } |
| 1069 | |
| 1070 | static void *m_next(struct seq_file *m, void *v, loff_t *pos) |
| 1071 | { |
| 1072 | struct proc_mounts *p = proc_mounts(m); |
| 1073 | |
| 1074 | return seq_list_next(v, &p->ns->list, pos); |
| 1075 | } |
| 1076 | |
| 1077 | static void m_stop(struct seq_file *m, void *v) |
| 1078 | { |
| 1079 | up_read(&namespace_sem); |
| 1080 | } |
| 1081 | |
| 1082 | static int m_show(struct seq_file *m, void *v) |
| 1083 | { |
| 1084 | struct proc_mounts *p = proc_mounts(m); |
| 1085 | struct mount *r = list_entry(v, struct mount, mnt_list); |
| 1086 | return p->show(m, &r->mnt); |
| 1087 | } |
| 1088 | |
| 1089 | const struct seq_operations mounts_op = { |
| 1090 | .start = m_start, |
| 1091 | .next = m_next, |
| 1092 | .stop = m_stop, |
| 1093 | .show = m_show, |
| 1094 | }; |
| 1095 | #endif /* CONFIG_PROC_FS */ |
| 1096 | |
| 1097 | /** |
| 1098 | * may_umount_tree - check if a mount tree is busy |
| 1099 | * @mnt: root of mount tree |
| 1100 | * |
| 1101 | * This is called to check if a tree of mounts has any |
| 1102 | * open files, pwds, chroots or sub mounts that are |
| 1103 | * busy. |
| 1104 | */ |
| 1105 | int may_umount_tree(struct vfsmount *m) |
| 1106 | { |
| 1107 | struct mount *mnt = real_mount(m); |
| 1108 | int actual_refs = 0; |
| 1109 | int minimum_refs = 0; |
| 1110 | struct mount *p; |
| 1111 | BUG_ON(!m); |
| 1112 | |
| 1113 | /* write lock needed for mnt_get_count */ |
| 1114 | lock_mount_hash(); |
| 1115 | for (p = mnt; p; p = next_mnt(p, mnt)) { |
| 1116 | actual_refs += mnt_get_count(p); |
| 1117 | minimum_refs += 2; |
| 1118 | } |
| 1119 | unlock_mount_hash(); |
| 1120 | |
| 1121 | if (actual_refs > minimum_refs) |
| 1122 | return 0; |
| 1123 | |
| 1124 | return 1; |
| 1125 | } |
| 1126 | |
| 1127 | EXPORT_SYMBOL(may_umount_tree); |
| 1128 | |
| 1129 | /** |
| 1130 | * may_umount - check if a mount point is busy |
| 1131 | * @mnt: root of mount |
| 1132 | * |
| 1133 | * This is called to check if a mount point has any |
| 1134 | * open files, pwds, chroots or sub mounts. If the |
| 1135 | * mount has sub mounts this will return busy |
| 1136 | * regardless of whether the sub mounts are busy. |
| 1137 | * |
| 1138 | * Doesn't take quota and stuff into account. IOW, in some cases it will |
| 1139 | * give false negatives. The main reason why it's here is that we need |
| 1140 | * a non-destructive way to look for easily umountable filesystems. |
| 1141 | */ |
| 1142 | int may_umount(struct vfsmount *mnt) |
| 1143 | { |
| 1144 | int ret = 1; |
| 1145 | down_read(&namespace_sem); |
| 1146 | lock_mount_hash(); |
| 1147 | if (propagate_mount_busy(real_mount(mnt), 2)) |
| 1148 | ret = 0; |
| 1149 | unlock_mount_hash(); |
| 1150 | up_read(&namespace_sem); |
| 1151 | return ret; |
| 1152 | } |
| 1153 | |
| 1154 | EXPORT_SYMBOL(may_umount); |
| 1155 | |
| 1156 | static LIST_HEAD(unmounted); /* protected by namespace_sem */ |
| 1157 | |
| 1158 | static void namespace_unlock(void) |
| 1159 | { |
| 1160 | struct mount *mnt; |
| 1161 | LIST_HEAD(head); |
| 1162 | |
| 1163 | if (likely(list_empty(&unmounted))) { |
| 1164 | up_write(&namespace_sem); |
| 1165 | return; |
| 1166 | } |
| 1167 | |
| 1168 | list_splice_init(&unmounted, &head); |
| 1169 | up_write(&namespace_sem); |
| 1170 | |
| 1171 | synchronize_rcu(); |
| 1172 | |
| 1173 | while (!list_empty(&head)) { |
| 1174 | mnt = list_first_entry(&head, struct mount, mnt_hash); |
| 1175 | list_del_init(&mnt->mnt_hash); |
| 1176 | if (mnt->mnt_ex_mountpoint.mnt) |
| 1177 | path_put(&mnt->mnt_ex_mountpoint); |
| 1178 | mntput(&mnt->mnt); |
| 1179 | } |
| 1180 | } |
| 1181 | |
| 1182 | static inline void namespace_lock(void) |
| 1183 | { |
| 1184 | down_write(&namespace_sem); |
| 1185 | } |
| 1186 | |
| 1187 | /* |
| 1188 | * mount_lock must be held |
| 1189 | * namespace_sem must be held for write |
| 1190 | * how = 0 => just this tree, don't propagate |
| 1191 | * how = 1 => propagate; we know that nobody else has reference to any victims |
| 1192 | * how = 2 => lazy umount |
| 1193 | */ |
| 1194 | void umount_tree(struct mount *mnt, int how) |
| 1195 | { |
| 1196 | LIST_HEAD(tmp_list); |
| 1197 | struct mount *p; |
| 1198 | |
| 1199 | for (p = mnt; p; p = next_mnt(p, mnt)) |
| 1200 | list_move(&p->mnt_hash, &tmp_list); |
| 1201 | |
| 1202 | if (how) |
| 1203 | propagate_umount(&tmp_list); |
| 1204 | |
| 1205 | list_for_each_entry(p, &tmp_list, mnt_hash) { |
| 1206 | list_del_init(&p->mnt_expire); |
| 1207 | list_del_init(&p->mnt_list); |
| 1208 | __touch_mnt_namespace(p->mnt_ns); |
| 1209 | p->mnt_ns = NULL; |
| 1210 | if (how < 2) |
| 1211 | p->mnt.mnt_flags |= MNT_SYNC_UMOUNT; |
| 1212 | list_del_init(&p->mnt_child); |
| 1213 | if (mnt_has_parent(p)) { |
| 1214 | put_mountpoint(p->mnt_mp); |
| 1215 | /* move the reference to mountpoint into ->mnt_ex_mountpoint */ |
| 1216 | p->mnt_ex_mountpoint.dentry = p->mnt_mountpoint; |
| 1217 | p->mnt_ex_mountpoint.mnt = &p->mnt_parent->mnt; |
| 1218 | p->mnt_mountpoint = p->mnt.mnt_root; |
| 1219 | p->mnt_parent = p; |
| 1220 | p->mnt_mp = NULL; |
| 1221 | } |
| 1222 | change_mnt_propagation(p, MS_PRIVATE); |
| 1223 | } |
| 1224 | list_splice(&tmp_list, &unmounted); |
| 1225 | } |
| 1226 | |
| 1227 | static void shrink_submounts(struct mount *mnt); |
| 1228 | |
| 1229 | static int do_umount(struct mount *mnt, int flags) |
| 1230 | { |
| 1231 | struct super_block *sb = mnt->mnt.mnt_sb; |
| 1232 | int retval; |
| 1233 | |
| 1234 | retval = security_sb_umount(&mnt->mnt, flags); |
| 1235 | if (retval) |
| 1236 | return retval; |
| 1237 | |
| 1238 | /* |
| 1239 | * Allow userspace to request a mountpoint be expired rather than |
| 1240 | * unmounting unconditionally. Unmount only happens if: |
| 1241 | * (1) the mark is already set (the mark is cleared by mntput()) |
| 1242 | * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] |
| 1243 | */ |
| 1244 | if (flags & MNT_EXPIRE) { |
| 1245 | if (&mnt->mnt == current->fs->root.mnt || |
| 1246 | flags & (MNT_FORCE | MNT_DETACH)) |
| 1247 | return -EINVAL; |
| 1248 | |
| 1249 | /* |
| 1250 | * probably don't strictly need the lock here if we examined |
| 1251 | * all race cases, but it's a slowpath. |
| 1252 | */ |
| 1253 | lock_mount_hash(); |
| 1254 | if (mnt_get_count(mnt) != 2) { |
| 1255 | unlock_mount_hash(); |
| 1256 | return -EBUSY; |
| 1257 | } |
| 1258 | unlock_mount_hash(); |
| 1259 | |
| 1260 | if (!xchg(&mnt->mnt_expiry_mark, 1)) |
| 1261 | return -EAGAIN; |
| 1262 | } |
| 1263 | |
| 1264 | /* |
| 1265 | * If we may have to abort operations to get out of this |
| 1266 | * mount, and they will themselves hold resources we must |
| 1267 | * allow the fs to do things. In the Unix tradition of |
| 1268 | * 'Gee thats tricky lets do it in userspace' the umount_begin |
| 1269 | * might fail to complete on the first run through as other tasks |
| 1270 | * must return, and the like. Thats for the mount program to worry |
| 1271 | * about for the moment. |
| 1272 | */ |
| 1273 | |
| 1274 | if (flags & MNT_FORCE && sb->s_op->umount_begin) { |
| 1275 | sb->s_op->umount_begin(sb); |
| 1276 | } |
| 1277 | |
| 1278 | /* |
| 1279 | * No sense to grab the lock for this test, but test itself looks |
| 1280 | * somewhat bogus. Suggestions for better replacement? |
| 1281 | * Ho-hum... In principle, we might treat that as umount + switch |
| 1282 | * to rootfs. GC would eventually take care of the old vfsmount. |
| 1283 | * Actually it makes sense, especially if rootfs would contain a |
| 1284 | * /reboot - static binary that would close all descriptors and |
| 1285 | * call reboot(9). Then init(8) could umount root and exec /reboot. |
| 1286 | */ |
| 1287 | if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { |
| 1288 | /* |
| 1289 | * Special case for "unmounting" root ... |
| 1290 | * we just try to remount it readonly. |
| 1291 | */ |
| 1292 | down_write(&sb->s_umount); |
| 1293 | if (!(sb->s_flags & MS_RDONLY)) |
| 1294 | retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); |
| 1295 | up_write(&sb->s_umount); |
| 1296 | return retval; |
| 1297 | } |
| 1298 | |
| 1299 | namespace_lock(); |
| 1300 | lock_mount_hash(); |
| 1301 | event++; |
| 1302 | |
| 1303 | if (flags & MNT_DETACH) { |
| 1304 | if (!list_empty(&mnt->mnt_list)) |
| 1305 | umount_tree(mnt, 2); |
| 1306 | retval = 0; |
| 1307 | } else { |
| 1308 | shrink_submounts(mnt); |
| 1309 | retval = -EBUSY; |
| 1310 | if (!propagate_mount_busy(mnt, 2)) { |
| 1311 | if (!list_empty(&mnt->mnt_list)) |
| 1312 | umount_tree(mnt, 1); |
| 1313 | retval = 0; |
| 1314 | } |
| 1315 | } |
| 1316 | unlock_mount_hash(); |
| 1317 | namespace_unlock(); |
| 1318 | return retval; |
| 1319 | } |
| 1320 | |
| 1321 | /* |
| 1322 | * Is the caller allowed to modify his namespace? |
| 1323 | */ |
| 1324 | static inline bool may_mount(void) |
| 1325 | { |
| 1326 | return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN); |
| 1327 | } |
| 1328 | |
| 1329 | /* |
| 1330 | * Now umount can handle mount points as well as block devices. |
| 1331 | * This is important for filesystems which use unnamed block devices. |
| 1332 | * |
| 1333 | * We now support a flag for forced unmount like the other 'big iron' |
| 1334 | * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD |
| 1335 | */ |
| 1336 | |
| 1337 | SYSCALL_DEFINE2(umount, char __user *, name, int, flags) |
| 1338 | { |
| 1339 | struct path path; |
| 1340 | struct mount *mnt; |
| 1341 | int retval; |
| 1342 | int lookup_flags = 0; |
| 1343 | |
| 1344 | if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) |
| 1345 | return -EINVAL; |
| 1346 | |
| 1347 | if (!may_mount()) |
| 1348 | return -EPERM; |
| 1349 | |
| 1350 | if (!(flags & UMOUNT_NOFOLLOW)) |
| 1351 | lookup_flags |= LOOKUP_FOLLOW; |
| 1352 | |
| 1353 | retval = user_path_mountpoint_at(AT_FDCWD, name, lookup_flags, &path); |
| 1354 | if (retval) |
| 1355 | goto out; |
| 1356 | mnt = real_mount(path.mnt); |
| 1357 | retval = -EINVAL; |
| 1358 | if (path.dentry != path.mnt->mnt_root) |
| 1359 | goto dput_and_out; |
| 1360 | if (!check_mnt(mnt)) |
| 1361 | goto dput_and_out; |
| 1362 | if (mnt->mnt.mnt_flags & MNT_LOCKED) |
| 1363 | goto dput_and_out; |
| 1364 | |
| 1365 | retval = do_umount(mnt, flags); |
| 1366 | dput_and_out: |
| 1367 | /* we mustn't call path_put() as that would clear mnt_expiry_mark */ |
| 1368 | dput(path.dentry); |
| 1369 | mntput_no_expire(mnt); |
| 1370 | out: |
| 1371 | return retval; |
| 1372 | } |
| 1373 | |
| 1374 | #ifdef __ARCH_WANT_SYS_OLDUMOUNT |
| 1375 | |
| 1376 | /* |
| 1377 | * The 2.0 compatible umount. No flags. |
| 1378 | */ |
| 1379 | SYSCALL_DEFINE1(oldumount, char __user *, name) |
| 1380 | { |
| 1381 | return sys_umount(name, 0); |
| 1382 | } |
| 1383 | |
| 1384 | #endif |
| 1385 | |
| 1386 | static bool is_mnt_ns_file(struct dentry *dentry) |
| 1387 | { |
| 1388 | /* Is this a proxy for a mount namespace? */ |
| 1389 | struct inode *inode = dentry->d_inode; |
| 1390 | struct proc_ns *ei; |
| 1391 | |
| 1392 | if (!proc_ns_inode(inode)) |
| 1393 | return false; |
| 1394 | |
| 1395 | ei = get_proc_ns(inode); |
| 1396 | if (ei->ns_ops != &mntns_operations) |
| 1397 | return false; |
| 1398 | |
| 1399 | return true; |
| 1400 | } |
| 1401 | |
| 1402 | static bool mnt_ns_loop(struct dentry *dentry) |
| 1403 | { |
| 1404 | /* Could bind mounting the mount namespace inode cause a |
| 1405 | * mount namespace loop? |
| 1406 | */ |
| 1407 | struct mnt_namespace *mnt_ns; |
| 1408 | if (!is_mnt_ns_file(dentry)) |
| 1409 | return false; |
| 1410 | |
| 1411 | mnt_ns = get_proc_ns(dentry->d_inode)->ns; |
| 1412 | return current->nsproxy->mnt_ns->seq >= mnt_ns->seq; |
| 1413 | } |
| 1414 | |
| 1415 | struct mount *copy_tree(struct mount *mnt, struct dentry *dentry, |
| 1416 | int flag) |
| 1417 | { |
| 1418 | struct mount *res, *p, *q, *r, *parent; |
| 1419 | |
| 1420 | if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt)) |
| 1421 | return ERR_PTR(-EINVAL); |
| 1422 | |
| 1423 | if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry)) |
| 1424 | return ERR_PTR(-EINVAL); |
| 1425 | |
| 1426 | res = q = clone_mnt(mnt, dentry, flag); |
| 1427 | if (IS_ERR(q)) |
| 1428 | return q; |
| 1429 | |
| 1430 | q->mnt.mnt_flags &= ~MNT_LOCKED; |
| 1431 | q->mnt_mountpoint = mnt->mnt_mountpoint; |
| 1432 | |
| 1433 | p = mnt; |
| 1434 | list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { |
| 1435 | struct mount *s; |
| 1436 | if (!is_subdir(r->mnt_mountpoint, dentry)) |
| 1437 | continue; |
| 1438 | |
| 1439 | for (s = r; s; s = next_mnt(s, r)) { |
| 1440 | if (!(flag & CL_COPY_UNBINDABLE) && |
| 1441 | IS_MNT_UNBINDABLE(s)) { |
| 1442 | s = skip_mnt_tree(s); |
| 1443 | continue; |
| 1444 | } |
| 1445 | if (!(flag & CL_COPY_MNT_NS_FILE) && |
| 1446 | is_mnt_ns_file(s->mnt.mnt_root)) { |
| 1447 | s = skip_mnt_tree(s); |
| 1448 | continue; |
| 1449 | } |
| 1450 | while (p != s->mnt_parent) { |
| 1451 | p = p->mnt_parent; |
| 1452 | q = q->mnt_parent; |
| 1453 | } |
| 1454 | p = s; |
| 1455 | parent = q; |
| 1456 | q = clone_mnt(p, p->mnt.mnt_root, flag); |
| 1457 | if (IS_ERR(q)) |
| 1458 | goto out; |
| 1459 | lock_mount_hash(); |
| 1460 | list_add_tail(&q->mnt_list, &res->mnt_list); |
| 1461 | attach_mnt(q, parent, p->mnt_mp); |
| 1462 | unlock_mount_hash(); |
| 1463 | } |
| 1464 | } |
| 1465 | return res; |
| 1466 | out: |
| 1467 | if (res) { |
| 1468 | lock_mount_hash(); |
| 1469 | umount_tree(res, 0); |
| 1470 | unlock_mount_hash(); |
| 1471 | } |
| 1472 | return q; |
| 1473 | } |
| 1474 | |
| 1475 | /* Caller should check returned pointer for errors */ |
| 1476 | |
| 1477 | struct vfsmount *collect_mounts(struct path *path) |
| 1478 | { |
| 1479 | struct mount *tree; |
| 1480 | namespace_lock(); |
| 1481 | tree = copy_tree(real_mount(path->mnt), path->dentry, |
| 1482 | CL_COPY_ALL | CL_PRIVATE); |
| 1483 | namespace_unlock(); |
| 1484 | if (IS_ERR(tree)) |
| 1485 | return ERR_CAST(tree); |
| 1486 | return &tree->mnt; |
| 1487 | } |
| 1488 | |
| 1489 | void drop_collected_mounts(struct vfsmount *mnt) |
| 1490 | { |
| 1491 | namespace_lock(); |
| 1492 | lock_mount_hash(); |
| 1493 | umount_tree(real_mount(mnt), 0); |
| 1494 | unlock_mount_hash(); |
| 1495 | namespace_unlock(); |
| 1496 | } |
| 1497 | |
| 1498 | int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, |
| 1499 | struct vfsmount *root) |
| 1500 | { |
| 1501 | struct mount *mnt; |
| 1502 | int res = f(root, arg); |
| 1503 | if (res) |
| 1504 | return res; |
| 1505 | list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) { |
| 1506 | res = f(&mnt->mnt, arg); |
| 1507 | if (res) |
| 1508 | return res; |
| 1509 | } |
| 1510 | return 0; |
| 1511 | } |
| 1512 | |
| 1513 | static void cleanup_group_ids(struct mount *mnt, struct mount *end) |
| 1514 | { |
| 1515 | struct mount *p; |
| 1516 | |
| 1517 | for (p = mnt; p != end; p = next_mnt(p, mnt)) { |
| 1518 | if (p->mnt_group_id && !IS_MNT_SHARED(p)) |
| 1519 | mnt_release_group_id(p); |
| 1520 | } |
| 1521 | } |
| 1522 | |
| 1523 | static int invent_group_ids(struct mount *mnt, bool recurse) |
| 1524 | { |
| 1525 | struct mount *p; |
| 1526 | |
| 1527 | for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { |
| 1528 | if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { |
| 1529 | int err = mnt_alloc_group_id(p); |
| 1530 | if (err) { |
| 1531 | cleanup_group_ids(mnt, p); |
| 1532 | return err; |
| 1533 | } |
| 1534 | } |
| 1535 | } |
| 1536 | |
| 1537 | return 0; |
| 1538 | } |
| 1539 | |
| 1540 | /* |
| 1541 | * @source_mnt : mount tree to be attached |
| 1542 | * @nd : place the mount tree @source_mnt is attached |
| 1543 | * @parent_nd : if non-null, detach the source_mnt from its parent and |
| 1544 | * store the parent mount and mountpoint dentry. |
| 1545 | * (done when source_mnt is moved) |
| 1546 | * |
| 1547 | * NOTE: in the table below explains the semantics when a source mount |
| 1548 | * of a given type is attached to a destination mount of a given type. |
| 1549 | * --------------------------------------------------------------------------- |
| 1550 | * | BIND MOUNT OPERATION | |
| 1551 | * |************************************************************************** |
| 1552 | * | source-->| shared | private | slave | unbindable | |
| 1553 | * | dest | | | | | |
| 1554 | * | | | | | | | |
| 1555 | * | v | | | | | |
| 1556 | * |************************************************************************** |
| 1557 | * | shared | shared (++) | shared (+) | shared(+++)| invalid | |
| 1558 | * | | | | | | |
| 1559 | * |non-shared| shared (+) | private | slave (*) | invalid | |
| 1560 | * *************************************************************************** |
| 1561 | * A bind operation clones the source mount and mounts the clone on the |
| 1562 | * destination mount. |
| 1563 | * |
| 1564 | * (++) the cloned mount is propagated to all the mounts in the propagation |
| 1565 | * tree of the destination mount and the cloned mount is added to |
| 1566 | * the peer group of the source mount. |
| 1567 | * (+) the cloned mount is created under the destination mount and is marked |
| 1568 | * as shared. The cloned mount is added to the peer group of the source |
| 1569 | * mount. |
| 1570 | * (+++) the mount is propagated to all the mounts in the propagation tree |
| 1571 | * of the destination mount and the cloned mount is made slave |
| 1572 | * of the same master as that of the source mount. The cloned mount |
| 1573 | * is marked as 'shared and slave'. |
| 1574 | * (*) the cloned mount is made a slave of the same master as that of the |
| 1575 | * source mount. |
| 1576 | * |
| 1577 | * --------------------------------------------------------------------------- |
| 1578 | * | MOVE MOUNT OPERATION | |
| 1579 | * |************************************************************************** |
| 1580 | * | source-->| shared | private | slave | unbindable | |
| 1581 | * | dest | | | | | |
| 1582 | * | | | | | | | |
| 1583 | * | v | | | | | |
| 1584 | * |************************************************************************** |
| 1585 | * | shared | shared (+) | shared (+) | shared(+++) | invalid | |
| 1586 | * | | | | | | |
| 1587 | * |non-shared| shared (+*) | private | slave (*) | unbindable | |
| 1588 | * *************************************************************************** |
| 1589 | * |
| 1590 | * (+) the mount is moved to the destination. And is then propagated to |
| 1591 | * all the mounts in the propagation tree of the destination mount. |
| 1592 | * (+*) the mount is moved to the destination. |
| 1593 | * (+++) the mount is moved to the destination and is then propagated to |
| 1594 | * all the mounts belonging to the destination mount's propagation tree. |
| 1595 | * the mount is marked as 'shared and slave'. |
| 1596 | * (*) the mount continues to be a slave at the new location. |
| 1597 | * |
| 1598 | * if the source mount is a tree, the operations explained above is |
| 1599 | * applied to each mount in the tree. |
| 1600 | * Must be called without spinlocks held, since this function can sleep |
| 1601 | * in allocations. |
| 1602 | */ |
| 1603 | static int attach_recursive_mnt(struct mount *source_mnt, |
| 1604 | struct mount *dest_mnt, |
| 1605 | struct mountpoint *dest_mp, |
| 1606 | struct path *parent_path) |
| 1607 | { |
| 1608 | LIST_HEAD(tree_list); |
| 1609 | struct mount *child, *p; |
| 1610 | int err; |
| 1611 | |
| 1612 | if (IS_MNT_SHARED(dest_mnt)) { |
| 1613 | err = invent_group_ids(source_mnt, true); |
| 1614 | if (err) |
| 1615 | goto out; |
| 1616 | } |
| 1617 | err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list); |
| 1618 | if (err) |
| 1619 | goto out_cleanup_ids; |
| 1620 | |
| 1621 | lock_mount_hash(); |
| 1622 | |
| 1623 | if (IS_MNT_SHARED(dest_mnt)) { |
| 1624 | for (p = source_mnt; p; p = next_mnt(p, source_mnt)) |
| 1625 | set_mnt_shared(p); |
| 1626 | } |
| 1627 | if (parent_path) { |
| 1628 | detach_mnt(source_mnt, parent_path); |
| 1629 | attach_mnt(source_mnt, dest_mnt, dest_mp); |
| 1630 | touch_mnt_namespace(source_mnt->mnt_ns); |
| 1631 | } else { |
| 1632 | mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt); |
| 1633 | commit_tree(source_mnt); |
| 1634 | } |
| 1635 | |
| 1636 | list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { |
| 1637 | list_del_init(&child->mnt_hash); |
| 1638 | commit_tree(child); |
| 1639 | } |
| 1640 | unlock_mount_hash(); |
| 1641 | |
| 1642 | return 0; |
| 1643 | |
| 1644 | out_cleanup_ids: |
| 1645 | if (IS_MNT_SHARED(dest_mnt)) |
| 1646 | cleanup_group_ids(source_mnt, NULL); |
| 1647 | out: |
| 1648 | return err; |
| 1649 | } |
| 1650 | |
| 1651 | static struct mountpoint *lock_mount(struct path *path) |
| 1652 | { |
| 1653 | struct vfsmount *mnt; |
| 1654 | struct dentry *dentry = path->dentry; |
| 1655 | retry: |
| 1656 | mutex_lock(&dentry->d_inode->i_mutex); |
| 1657 | if (unlikely(cant_mount(dentry))) { |
| 1658 | mutex_unlock(&dentry->d_inode->i_mutex); |
| 1659 | return ERR_PTR(-ENOENT); |
| 1660 | } |
| 1661 | namespace_lock(); |
| 1662 | mnt = lookup_mnt(path); |
| 1663 | if (likely(!mnt)) { |
| 1664 | struct mountpoint *mp = new_mountpoint(dentry); |
| 1665 | if (IS_ERR(mp)) { |
| 1666 | namespace_unlock(); |
| 1667 | mutex_unlock(&dentry->d_inode->i_mutex); |
| 1668 | return mp; |
| 1669 | } |
| 1670 | return mp; |
| 1671 | } |
| 1672 | namespace_unlock(); |
| 1673 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
| 1674 | path_put(path); |
| 1675 | path->mnt = mnt; |
| 1676 | dentry = path->dentry = dget(mnt->mnt_root); |
| 1677 | goto retry; |
| 1678 | } |
| 1679 | |
| 1680 | static void unlock_mount(struct mountpoint *where) |
| 1681 | { |
| 1682 | struct dentry *dentry = where->m_dentry; |
| 1683 | put_mountpoint(where); |
| 1684 | namespace_unlock(); |
| 1685 | mutex_unlock(&dentry->d_inode->i_mutex); |
| 1686 | } |
| 1687 | |
| 1688 | static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp) |
| 1689 | { |
| 1690 | if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER) |
| 1691 | return -EINVAL; |
| 1692 | |
| 1693 | if (S_ISDIR(mp->m_dentry->d_inode->i_mode) != |
| 1694 | S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode)) |
| 1695 | return -ENOTDIR; |
| 1696 | |
| 1697 | return attach_recursive_mnt(mnt, p, mp, NULL); |
| 1698 | } |
| 1699 | |
| 1700 | /* |
| 1701 | * Sanity check the flags to change_mnt_propagation. |
| 1702 | */ |
| 1703 | |
| 1704 | static int flags_to_propagation_type(int flags) |
| 1705 | { |
| 1706 | int type = flags & ~(MS_REC | MS_SILENT); |
| 1707 | |
| 1708 | /* Fail if any non-propagation flags are set */ |
| 1709 | if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
| 1710 | return 0; |
| 1711 | /* Only one propagation flag should be set */ |
| 1712 | if (!is_power_of_2(type)) |
| 1713 | return 0; |
| 1714 | return type; |
| 1715 | } |
| 1716 | |
| 1717 | /* |
| 1718 | * recursively change the type of the mountpoint. |
| 1719 | */ |
| 1720 | static int do_change_type(struct path *path, int flag) |
| 1721 | { |
| 1722 | struct mount *m; |
| 1723 | struct mount *mnt = real_mount(path->mnt); |
| 1724 | int recurse = flag & MS_REC; |
| 1725 | int type; |
| 1726 | int err = 0; |
| 1727 | |
| 1728 | if (path->dentry != path->mnt->mnt_root) |
| 1729 | return -EINVAL; |
| 1730 | |
| 1731 | type = flags_to_propagation_type(flag); |
| 1732 | if (!type) |
| 1733 | return -EINVAL; |
| 1734 | |
| 1735 | namespace_lock(); |
| 1736 | if (type == MS_SHARED) { |
| 1737 | err = invent_group_ids(mnt, recurse); |
| 1738 | if (err) |
| 1739 | goto out_unlock; |
| 1740 | } |
| 1741 | |
| 1742 | lock_mount_hash(); |
| 1743 | for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) |
| 1744 | change_mnt_propagation(m, type); |
| 1745 | unlock_mount_hash(); |
| 1746 | |
| 1747 | out_unlock: |
| 1748 | namespace_unlock(); |
| 1749 | return err; |
| 1750 | } |
| 1751 | |
| 1752 | static bool has_locked_children(struct mount *mnt, struct dentry *dentry) |
| 1753 | { |
| 1754 | struct mount *child; |
| 1755 | list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { |
| 1756 | if (!is_subdir(child->mnt_mountpoint, dentry)) |
| 1757 | continue; |
| 1758 | |
| 1759 | if (child->mnt.mnt_flags & MNT_LOCKED) |
| 1760 | return true; |
| 1761 | } |
| 1762 | return false; |
| 1763 | } |
| 1764 | |
| 1765 | /* |
| 1766 | * do loopback mount. |
| 1767 | */ |
| 1768 | static int do_loopback(struct path *path, const char *old_name, |
| 1769 | int recurse) |
| 1770 | { |
| 1771 | struct path old_path; |
| 1772 | struct mount *mnt = NULL, *old, *parent; |
| 1773 | struct mountpoint *mp; |
| 1774 | int err; |
| 1775 | if (!old_name || !*old_name) |
| 1776 | return -EINVAL; |
| 1777 | err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); |
| 1778 | if (err) |
| 1779 | return err; |
| 1780 | |
| 1781 | err = -EINVAL; |
| 1782 | if (mnt_ns_loop(old_path.dentry)) |
| 1783 | goto out; |
| 1784 | |
| 1785 | mp = lock_mount(path); |
| 1786 | err = PTR_ERR(mp); |
| 1787 | if (IS_ERR(mp)) |
| 1788 | goto out; |
| 1789 | |
| 1790 | old = real_mount(old_path.mnt); |
| 1791 | parent = real_mount(path->mnt); |
| 1792 | |
| 1793 | err = -EINVAL; |
| 1794 | if (IS_MNT_UNBINDABLE(old)) |
| 1795 | goto out2; |
| 1796 | |
| 1797 | if (!check_mnt(parent) || !check_mnt(old)) |
| 1798 | goto out2; |
| 1799 | |
| 1800 | if (!recurse && has_locked_children(old, old_path.dentry)) |
| 1801 | goto out2; |
| 1802 | |
| 1803 | if (recurse) |
| 1804 | mnt = copy_tree(old, old_path.dentry, CL_COPY_MNT_NS_FILE); |
| 1805 | else |
| 1806 | mnt = clone_mnt(old, old_path.dentry, 0); |
| 1807 | |
| 1808 | if (IS_ERR(mnt)) { |
| 1809 | err = PTR_ERR(mnt); |
| 1810 | goto out2; |
| 1811 | } |
| 1812 | |
| 1813 | mnt->mnt.mnt_flags &= ~MNT_LOCKED; |
| 1814 | |
| 1815 | err = graft_tree(mnt, parent, mp); |
| 1816 | if (err) { |
| 1817 | lock_mount_hash(); |
| 1818 | umount_tree(mnt, 0); |
| 1819 | unlock_mount_hash(); |
| 1820 | } |
| 1821 | out2: |
| 1822 | unlock_mount(mp); |
| 1823 | out: |
| 1824 | path_put(&old_path); |
| 1825 | return err; |
| 1826 | } |
| 1827 | |
| 1828 | static int change_mount_flags(struct vfsmount *mnt, int ms_flags) |
| 1829 | { |
| 1830 | int error = 0; |
| 1831 | int readonly_request = 0; |
| 1832 | |
| 1833 | if (ms_flags & MS_RDONLY) |
| 1834 | readonly_request = 1; |
| 1835 | if (readonly_request == __mnt_is_readonly(mnt)) |
| 1836 | return 0; |
| 1837 | |
| 1838 | if (mnt->mnt_flags & MNT_LOCK_READONLY) |
| 1839 | return -EPERM; |
| 1840 | |
| 1841 | if (readonly_request) |
| 1842 | error = mnt_make_readonly(real_mount(mnt)); |
| 1843 | else |
| 1844 | __mnt_unmake_readonly(real_mount(mnt)); |
| 1845 | return error; |
| 1846 | } |
| 1847 | |
| 1848 | /* |
| 1849 | * change filesystem flags. dir should be a physical root of filesystem. |
| 1850 | * If you've mounted a non-root directory somewhere and want to do remount |
| 1851 | * on it - tough luck. |
| 1852 | */ |
| 1853 | static int do_remount(struct path *path, int flags, int mnt_flags, |
| 1854 | void *data) |
| 1855 | { |
| 1856 | int err; |
| 1857 | struct super_block *sb = path->mnt->mnt_sb; |
| 1858 | struct mount *mnt = real_mount(path->mnt); |
| 1859 | |
| 1860 | if (!check_mnt(mnt)) |
| 1861 | return -EINVAL; |
| 1862 | |
| 1863 | if (path->dentry != path->mnt->mnt_root) |
| 1864 | return -EINVAL; |
| 1865 | |
| 1866 | err = security_sb_remount(sb, data); |
| 1867 | if (err) |
| 1868 | return err; |
| 1869 | |
| 1870 | down_write(&sb->s_umount); |
| 1871 | if (flags & MS_BIND) |
| 1872 | err = change_mount_flags(path->mnt, flags); |
| 1873 | else if (!capable(CAP_SYS_ADMIN)) |
| 1874 | err = -EPERM; |
| 1875 | else |
| 1876 | err = do_remount_sb(sb, flags, data, 0); |
| 1877 | if (!err) { |
| 1878 | lock_mount_hash(); |
| 1879 | mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK; |
| 1880 | mnt->mnt.mnt_flags = mnt_flags; |
| 1881 | touch_mnt_namespace(mnt->mnt_ns); |
| 1882 | unlock_mount_hash(); |
| 1883 | } |
| 1884 | up_write(&sb->s_umount); |
| 1885 | return err; |
| 1886 | } |
| 1887 | |
| 1888 | static inline int tree_contains_unbindable(struct mount *mnt) |
| 1889 | { |
| 1890 | struct mount *p; |
| 1891 | for (p = mnt; p; p = next_mnt(p, mnt)) { |
| 1892 | if (IS_MNT_UNBINDABLE(p)) |
| 1893 | return 1; |
| 1894 | } |
| 1895 | return 0; |
| 1896 | } |
| 1897 | |
| 1898 | static int do_move_mount(struct path *path, const char *old_name) |
| 1899 | { |
| 1900 | struct path old_path, parent_path; |
| 1901 | struct mount *p; |
| 1902 | struct mount *old; |
| 1903 | struct mountpoint *mp; |
| 1904 | int err; |
| 1905 | if (!old_name || !*old_name) |
| 1906 | return -EINVAL; |
| 1907 | err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); |
| 1908 | if (err) |
| 1909 | return err; |
| 1910 | |
| 1911 | mp = lock_mount(path); |
| 1912 | err = PTR_ERR(mp); |
| 1913 | if (IS_ERR(mp)) |
| 1914 | goto out; |
| 1915 | |
| 1916 | old = real_mount(old_path.mnt); |
| 1917 | p = real_mount(path->mnt); |
| 1918 | |
| 1919 | err = -EINVAL; |
| 1920 | if (!check_mnt(p) || !check_mnt(old)) |
| 1921 | goto out1; |
| 1922 | |
| 1923 | if (old->mnt.mnt_flags & MNT_LOCKED) |
| 1924 | goto out1; |
| 1925 | |
| 1926 | err = -EINVAL; |
| 1927 | if (old_path.dentry != old_path.mnt->mnt_root) |
| 1928 | goto out1; |
| 1929 | |
| 1930 | if (!mnt_has_parent(old)) |
| 1931 | goto out1; |
| 1932 | |
| 1933 | if (S_ISDIR(path->dentry->d_inode->i_mode) != |
| 1934 | S_ISDIR(old_path.dentry->d_inode->i_mode)) |
| 1935 | goto out1; |
| 1936 | /* |
| 1937 | * Don't move a mount residing in a shared parent. |
| 1938 | */ |
| 1939 | if (IS_MNT_SHARED(old->mnt_parent)) |
| 1940 | goto out1; |
| 1941 | /* |
| 1942 | * Don't move a mount tree containing unbindable mounts to a destination |
| 1943 | * mount which is shared. |
| 1944 | */ |
| 1945 | if (IS_MNT_SHARED(p) && tree_contains_unbindable(old)) |
| 1946 | goto out1; |
| 1947 | err = -ELOOP; |
| 1948 | for (; mnt_has_parent(p); p = p->mnt_parent) |
| 1949 | if (p == old) |
| 1950 | goto out1; |
| 1951 | |
| 1952 | err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path); |
| 1953 | if (err) |
| 1954 | goto out1; |
| 1955 | |
| 1956 | /* if the mount is moved, it should no longer be expire |
| 1957 | * automatically */ |
| 1958 | list_del_init(&old->mnt_expire); |
| 1959 | out1: |
| 1960 | unlock_mount(mp); |
| 1961 | out: |
| 1962 | if (!err) |
| 1963 | path_put(&parent_path); |
| 1964 | path_put(&old_path); |
| 1965 | return err; |
| 1966 | } |
| 1967 | |
| 1968 | static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype) |
| 1969 | { |
| 1970 | int err; |
| 1971 | const char *subtype = strchr(fstype, '.'); |
| 1972 | if (subtype) { |
| 1973 | subtype++; |
| 1974 | err = -EINVAL; |
| 1975 | if (!subtype[0]) |
| 1976 | goto err; |
| 1977 | } else |
| 1978 | subtype = ""; |
| 1979 | |
| 1980 | mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL); |
| 1981 | err = -ENOMEM; |
| 1982 | if (!mnt->mnt_sb->s_subtype) |
| 1983 | goto err; |
| 1984 | return mnt; |
| 1985 | |
| 1986 | err: |
| 1987 | mntput(mnt); |
| 1988 | return ERR_PTR(err); |
| 1989 | } |
| 1990 | |
| 1991 | /* |
| 1992 | * add a mount into a namespace's mount tree |
| 1993 | */ |
| 1994 | static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags) |
| 1995 | { |
| 1996 | struct mountpoint *mp; |
| 1997 | struct mount *parent; |
| 1998 | int err; |
| 1999 | |
| 2000 | mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL | MNT_DOOMED | MNT_SYNC_UMOUNT); |
| 2001 | |
| 2002 | mp = lock_mount(path); |
| 2003 | if (IS_ERR(mp)) |
| 2004 | return PTR_ERR(mp); |
| 2005 | |
| 2006 | parent = real_mount(path->mnt); |
| 2007 | err = -EINVAL; |
| 2008 | if (unlikely(!check_mnt(parent))) { |
| 2009 | /* that's acceptable only for automounts done in private ns */ |
| 2010 | if (!(mnt_flags & MNT_SHRINKABLE)) |
| 2011 | goto unlock; |
| 2012 | /* ... and for those we'd better have mountpoint still alive */ |
| 2013 | if (!parent->mnt_ns) |
| 2014 | goto unlock; |
| 2015 | } |
| 2016 | |
| 2017 | /* Refuse the same filesystem on the same mount point */ |
| 2018 | err = -EBUSY; |
| 2019 | if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && |
| 2020 | path->mnt->mnt_root == path->dentry) |
| 2021 | goto unlock; |
| 2022 | |
| 2023 | err = -EINVAL; |
| 2024 | if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode)) |
| 2025 | goto unlock; |
| 2026 | |
| 2027 | newmnt->mnt.mnt_flags = mnt_flags; |
| 2028 | err = graft_tree(newmnt, parent, mp); |
| 2029 | |
| 2030 | unlock: |
| 2031 | unlock_mount(mp); |
| 2032 | return err; |
| 2033 | } |
| 2034 | |
| 2035 | /* |
| 2036 | * create a new mount for userspace and request it to be added into the |
| 2037 | * namespace's tree |
| 2038 | */ |
| 2039 | static int do_new_mount(struct path *path, const char *fstype, int flags, |
| 2040 | int mnt_flags, const char *name, void *data) |
| 2041 | { |
| 2042 | struct file_system_type *type; |
| 2043 | struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; |
| 2044 | struct vfsmount *mnt; |
| 2045 | int err; |
| 2046 | |
| 2047 | if (!fstype) |
| 2048 | return -EINVAL; |
| 2049 | |
| 2050 | type = get_fs_type(fstype); |
| 2051 | if (!type) |
| 2052 | return -ENODEV; |
| 2053 | |
| 2054 | if (user_ns != &init_user_ns) { |
| 2055 | if (!(type->fs_flags & FS_USERNS_MOUNT)) { |
| 2056 | put_filesystem(type); |
| 2057 | return -EPERM; |
| 2058 | } |
| 2059 | /* Only in special cases allow devices from mounts |
| 2060 | * created outside the initial user namespace. |
| 2061 | */ |
| 2062 | if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) { |
| 2063 | flags |= MS_NODEV; |
| 2064 | mnt_flags |= MNT_NODEV; |
| 2065 | } |
| 2066 | } |
| 2067 | |
| 2068 | mnt = vfs_kern_mount(type, flags, name, data); |
| 2069 | if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && |
| 2070 | !mnt->mnt_sb->s_subtype) |
| 2071 | mnt = fs_set_subtype(mnt, fstype); |
| 2072 | |
| 2073 | put_filesystem(type); |
| 2074 | if (IS_ERR(mnt)) |
| 2075 | return PTR_ERR(mnt); |
| 2076 | |
| 2077 | err = do_add_mount(real_mount(mnt), path, mnt_flags); |
| 2078 | if (err) |
| 2079 | mntput(mnt); |
| 2080 | return err; |
| 2081 | } |
| 2082 | |
| 2083 | int finish_automount(struct vfsmount *m, struct path *path) |
| 2084 | { |
| 2085 | struct mount *mnt = real_mount(m); |
| 2086 | int err; |
| 2087 | /* The new mount record should have at least 2 refs to prevent it being |
| 2088 | * expired before we get a chance to add it |
| 2089 | */ |
| 2090 | BUG_ON(mnt_get_count(mnt) < 2); |
| 2091 | |
| 2092 | if (m->mnt_sb == path->mnt->mnt_sb && |
| 2093 | m->mnt_root == path->dentry) { |
| 2094 | err = -ELOOP; |
| 2095 | goto fail; |
| 2096 | } |
| 2097 | |
| 2098 | err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE); |
| 2099 | if (!err) |
| 2100 | return 0; |
| 2101 | fail: |
| 2102 | /* remove m from any expiration list it may be on */ |
| 2103 | if (!list_empty(&mnt->mnt_expire)) { |
| 2104 | namespace_lock(); |
| 2105 | list_del_init(&mnt->mnt_expire); |
| 2106 | namespace_unlock(); |
| 2107 | } |
| 2108 | mntput(m); |
| 2109 | mntput(m); |
| 2110 | return err; |
| 2111 | } |
| 2112 | |
| 2113 | /** |
| 2114 | * mnt_set_expiry - Put a mount on an expiration list |
| 2115 | * @mnt: The mount to list. |
| 2116 | * @expiry_list: The list to add the mount to. |
| 2117 | */ |
| 2118 | void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list) |
| 2119 | { |
| 2120 | namespace_lock(); |
| 2121 | |
| 2122 | list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list); |
| 2123 | |
| 2124 | namespace_unlock(); |
| 2125 | } |
| 2126 | EXPORT_SYMBOL(mnt_set_expiry); |
| 2127 | |
| 2128 | /* |
| 2129 | * process a list of expirable mountpoints with the intent of discarding any |
| 2130 | * mountpoints that aren't in use and haven't been touched since last we came |
| 2131 | * here |
| 2132 | */ |
| 2133 | void mark_mounts_for_expiry(struct list_head *mounts) |
| 2134 | { |
| 2135 | struct mount *mnt, *next; |
| 2136 | LIST_HEAD(graveyard); |
| 2137 | |
| 2138 | if (list_empty(mounts)) |
| 2139 | return; |
| 2140 | |
| 2141 | namespace_lock(); |
| 2142 | lock_mount_hash(); |
| 2143 | |
| 2144 | /* extract from the expiration list every vfsmount that matches the |
| 2145 | * following criteria: |
| 2146 | * - only referenced by its parent vfsmount |
| 2147 | * - still marked for expiry (marked on the last call here; marks are |
| 2148 | * cleared by mntput()) |
| 2149 | */ |
| 2150 | list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { |
| 2151 | if (!xchg(&mnt->mnt_expiry_mark, 1) || |
| 2152 | propagate_mount_busy(mnt, 1)) |
| 2153 | continue; |
| 2154 | list_move(&mnt->mnt_expire, &graveyard); |
| 2155 | } |
| 2156 | while (!list_empty(&graveyard)) { |
| 2157 | mnt = list_first_entry(&graveyard, struct mount, mnt_expire); |
| 2158 | touch_mnt_namespace(mnt->mnt_ns); |
| 2159 | umount_tree(mnt, 1); |
| 2160 | } |
| 2161 | unlock_mount_hash(); |
| 2162 | namespace_unlock(); |
| 2163 | } |
| 2164 | |
| 2165 | EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); |
| 2166 | |
| 2167 | /* |
| 2168 | * Ripoff of 'select_parent()' |
| 2169 | * |
| 2170 | * search the list of submounts for a given mountpoint, and move any |
| 2171 | * shrinkable submounts to the 'graveyard' list. |
| 2172 | */ |
| 2173 | static int select_submounts(struct mount *parent, struct list_head *graveyard) |
| 2174 | { |
| 2175 | struct mount *this_parent = parent; |
| 2176 | struct list_head *next; |
| 2177 | int found = 0; |
| 2178 | |
| 2179 | repeat: |
| 2180 | next = this_parent->mnt_mounts.next; |
| 2181 | resume: |
| 2182 | while (next != &this_parent->mnt_mounts) { |
| 2183 | struct list_head *tmp = next; |
| 2184 | struct mount *mnt = list_entry(tmp, struct mount, mnt_child); |
| 2185 | |
| 2186 | next = tmp->next; |
| 2187 | if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE)) |
| 2188 | continue; |
| 2189 | /* |
| 2190 | * Descend a level if the d_mounts list is non-empty. |
| 2191 | */ |
| 2192 | if (!list_empty(&mnt->mnt_mounts)) { |
| 2193 | this_parent = mnt; |
| 2194 | goto repeat; |
| 2195 | } |
| 2196 | |
| 2197 | if (!propagate_mount_busy(mnt, 1)) { |
| 2198 | list_move_tail(&mnt->mnt_expire, graveyard); |
| 2199 | found++; |
| 2200 | } |
| 2201 | } |
| 2202 | /* |
| 2203 | * All done at this level ... ascend and resume the search |
| 2204 | */ |
| 2205 | if (this_parent != parent) { |
| 2206 | next = this_parent->mnt_child.next; |
| 2207 | this_parent = this_parent->mnt_parent; |
| 2208 | goto resume; |
| 2209 | } |
| 2210 | return found; |
| 2211 | } |
| 2212 | |
| 2213 | /* |
| 2214 | * process a list of expirable mountpoints with the intent of discarding any |
| 2215 | * submounts of a specific parent mountpoint |
| 2216 | * |
| 2217 | * mount_lock must be held for write |
| 2218 | */ |
| 2219 | static void shrink_submounts(struct mount *mnt) |
| 2220 | { |
| 2221 | LIST_HEAD(graveyard); |
| 2222 | struct mount *m; |
| 2223 | |
| 2224 | /* extract submounts of 'mountpoint' from the expiration list */ |
| 2225 | while (select_submounts(mnt, &graveyard)) { |
| 2226 | while (!list_empty(&graveyard)) { |
| 2227 | m = list_first_entry(&graveyard, struct mount, |
| 2228 | mnt_expire); |
| 2229 | touch_mnt_namespace(m->mnt_ns); |
| 2230 | umount_tree(m, 1); |
| 2231 | } |
| 2232 | } |
| 2233 | } |
| 2234 | |
| 2235 | /* |
| 2236 | * Some copy_from_user() implementations do not return the exact number of |
| 2237 | * bytes remaining to copy on a fault. But copy_mount_options() requires that. |
| 2238 | * Note that this function differs from copy_from_user() in that it will oops |
| 2239 | * on bad values of `to', rather than returning a short copy. |
| 2240 | */ |
| 2241 | static long exact_copy_from_user(void *to, const void __user * from, |
| 2242 | unsigned long n) |
| 2243 | { |
| 2244 | char *t = to; |
| 2245 | const char __user *f = from; |
| 2246 | char c; |
| 2247 | |
| 2248 | if (!access_ok(VERIFY_READ, from, n)) |
| 2249 | return n; |
| 2250 | |
| 2251 | while (n) { |
| 2252 | if (__get_user(c, f)) { |
| 2253 | memset(t, 0, n); |
| 2254 | break; |
| 2255 | } |
| 2256 | *t++ = c; |
| 2257 | f++; |
| 2258 | n--; |
| 2259 | } |
| 2260 | return n; |
| 2261 | } |
| 2262 | |
| 2263 | int copy_mount_options(const void __user * data, unsigned long *where) |
| 2264 | { |
| 2265 | int i; |
| 2266 | unsigned long page; |
| 2267 | unsigned long size; |
| 2268 | |
| 2269 | *where = 0; |
| 2270 | if (!data) |
| 2271 | return 0; |
| 2272 | |
| 2273 | if (!(page = __get_free_page(GFP_KERNEL))) |
| 2274 | return -ENOMEM; |
| 2275 | |
| 2276 | /* We only care that *some* data at the address the user |
| 2277 | * gave us is valid. Just in case, we'll zero |
| 2278 | * the remainder of the page. |
| 2279 | */ |
| 2280 | /* copy_from_user cannot cross TASK_SIZE ! */ |
| 2281 | size = TASK_SIZE - (unsigned long)data; |
| 2282 | if (size > PAGE_SIZE) |
| 2283 | size = PAGE_SIZE; |
| 2284 | |
| 2285 | i = size - exact_copy_from_user((void *)page, data, size); |
| 2286 | if (!i) { |
| 2287 | free_page(page); |
| 2288 | return -EFAULT; |
| 2289 | } |
| 2290 | if (i != PAGE_SIZE) |
| 2291 | memset((char *)page + i, 0, PAGE_SIZE - i); |
| 2292 | *where = page; |
| 2293 | return 0; |
| 2294 | } |
| 2295 | |
| 2296 | int copy_mount_string(const void __user *data, char **where) |
| 2297 | { |
| 2298 | char *tmp; |
| 2299 | |
| 2300 | if (!data) { |
| 2301 | *where = NULL; |
| 2302 | return 0; |
| 2303 | } |
| 2304 | |
| 2305 | tmp = strndup_user(data, PAGE_SIZE); |
| 2306 | if (IS_ERR(tmp)) |
| 2307 | return PTR_ERR(tmp); |
| 2308 | |
| 2309 | *where = tmp; |
| 2310 | return 0; |
| 2311 | } |
| 2312 | |
| 2313 | /* |
| 2314 | * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to |
| 2315 | * be given to the mount() call (ie: read-only, no-dev, no-suid etc). |
| 2316 | * |
| 2317 | * data is a (void *) that can point to any structure up to |
| 2318 | * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent |
| 2319 | * information (or be NULL). |
| 2320 | * |
| 2321 | * Pre-0.97 versions of mount() didn't have a flags word. |
| 2322 | * When the flags word was introduced its top half was required |
| 2323 | * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. |
| 2324 | * Therefore, if this magic number is present, it carries no information |
| 2325 | * and must be discarded. |
| 2326 | */ |
| 2327 | long do_mount(const char *dev_name, const char *dir_name, |
| 2328 | const char *type_page, unsigned long flags, void *data_page) |
| 2329 | { |
| 2330 | struct path path; |
| 2331 | int retval = 0; |
| 2332 | int mnt_flags = 0; |
| 2333 | |
| 2334 | /* Discard magic */ |
| 2335 | if ((flags & MS_MGC_MSK) == MS_MGC_VAL) |
| 2336 | flags &= ~MS_MGC_MSK; |
| 2337 | |
| 2338 | /* Basic sanity checks */ |
| 2339 | |
| 2340 | if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) |
| 2341 | return -EINVAL; |
| 2342 | |
| 2343 | if (data_page) |
| 2344 | ((char *)data_page)[PAGE_SIZE - 1] = 0; |
| 2345 | |
| 2346 | /* ... and get the mountpoint */ |
| 2347 | retval = kern_path(dir_name, LOOKUP_FOLLOW, &path); |
| 2348 | if (retval) |
| 2349 | return retval; |
| 2350 | |
| 2351 | retval = security_sb_mount(dev_name, &path, |
| 2352 | type_page, flags, data_page); |
| 2353 | if (!retval && !may_mount()) |
| 2354 | retval = -EPERM; |
| 2355 | if (retval) |
| 2356 | goto dput_out; |
| 2357 | |
| 2358 | /* Default to relatime unless overriden */ |
| 2359 | if (!(flags & MS_NOATIME)) |
| 2360 | mnt_flags |= MNT_RELATIME; |
| 2361 | |
| 2362 | /* Separate the per-mountpoint flags */ |
| 2363 | if (flags & MS_NOSUID) |
| 2364 | mnt_flags |= MNT_NOSUID; |
| 2365 | if (flags & MS_NODEV) |
| 2366 | mnt_flags |= MNT_NODEV; |
| 2367 | if (flags & MS_NOEXEC) |
| 2368 | mnt_flags |= MNT_NOEXEC; |
| 2369 | if (flags & MS_NOATIME) |
| 2370 | mnt_flags |= MNT_NOATIME; |
| 2371 | if (flags & MS_NODIRATIME) |
| 2372 | mnt_flags |= MNT_NODIRATIME; |
| 2373 | if (flags & MS_STRICTATIME) |
| 2374 | mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); |
| 2375 | if (flags & MS_RDONLY) |
| 2376 | mnt_flags |= MNT_READONLY; |
| 2377 | |
| 2378 | flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN | |
| 2379 | MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT | |
| 2380 | MS_STRICTATIME); |
| 2381 | |
| 2382 | if (flags & MS_REMOUNT) |
| 2383 | retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags, |
| 2384 | data_page); |
| 2385 | else if (flags & MS_BIND) |
| 2386 | retval = do_loopback(&path, dev_name, flags & MS_REC); |
| 2387 | else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
| 2388 | retval = do_change_type(&path, flags); |
| 2389 | else if (flags & MS_MOVE) |
| 2390 | retval = do_move_mount(&path, dev_name); |
| 2391 | else |
| 2392 | retval = do_new_mount(&path, type_page, flags, mnt_flags, |
| 2393 | dev_name, data_page); |
| 2394 | dput_out: |
| 2395 | path_put(&path); |
| 2396 | return retval; |
| 2397 | } |
| 2398 | |
| 2399 | static void free_mnt_ns(struct mnt_namespace *ns) |
| 2400 | { |
| 2401 | proc_free_inum(ns->proc_inum); |
| 2402 | put_user_ns(ns->user_ns); |
| 2403 | kfree(ns); |
| 2404 | } |
| 2405 | |
| 2406 | /* |
| 2407 | * Assign a sequence number so we can detect when we attempt to bind |
| 2408 | * mount a reference to an older mount namespace into the current |
| 2409 | * mount namespace, preventing reference counting loops. A 64bit |
| 2410 | * number incrementing at 10Ghz will take 12,427 years to wrap which |
| 2411 | * is effectively never, so we can ignore the possibility. |
| 2412 | */ |
| 2413 | static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1); |
| 2414 | |
| 2415 | static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns) |
| 2416 | { |
| 2417 | struct mnt_namespace *new_ns; |
| 2418 | int ret; |
| 2419 | |
| 2420 | new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); |
| 2421 | if (!new_ns) |
| 2422 | return ERR_PTR(-ENOMEM); |
| 2423 | ret = proc_alloc_inum(&new_ns->proc_inum); |
| 2424 | if (ret) { |
| 2425 | kfree(new_ns); |
| 2426 | return ERR_PTR(ret); |
| 2427 | } |
| 2428 | new_ns->seq = atomic64_add_return(1, &mnt_ns_seq); |
| 2429 | atomic_set(&new_ns->count, 1); |
| 2430 | new_ns->root = NULL; |
| 2431 | INIT_LIST_HEAD(&new_ns->list); |
| 2432 | init_waitqueue_head(&new_ns->poll); |
| 2433 | new_ns->event = 0; |
| 2434 | new_ns->user_ns = get_user_ns(user_ns); |
| 2435 | return new_ns; |
| 2436 | } |
| 2437 | |
| 2438 | struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, |
| 2439 | struct user_namespace *user_ns, struct fs_struct *new_fs) |
| 2440 | { |
| 2441 | struct mnt_namespace *new_ns; |
| 2442 | struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; |
| 2443 | struct mount *p, *q; |
| 2444 | struct mount *old; |
| 2445 | struct mount *new; |
| 2446 | int copy_flags; |
| 2447 | |
| 2448 | BUG_ON(!ns); |
| 2449 | |
| 2450 | if (likely(!(flags & CLONE_NEWNS))) { |
| 2451 | get_mnt_ns(ns); |
| 2452 | return ns; |
| 2453 | } |
| 2454 | |
| 2455 | old = ns->root; |
| 2456 | |
| 2457 | new_ns = alloc_mnt_ns(user_ns); |
| 2458 | if (IS_ERR(new_ns)) |
| 2459 | return new_ns; |
| 2460 | |
| 2461 | namespace_lock(); |
| 2462 | /* First pass: copy the tree topology */ |
| 2463 | copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE; |
| 2464 | if (user_ns != ns->user_ns) |
| 2465 | copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED; |
| 2466 | new = copy_tree(old, old->mnt.mnt_root, copy_flags); |
| 2467 | if (IS_ERR(new)) { |
| 2468 | namespace_unlock(); |
| 2469 | free_mnt_ns(new_ns); |
| 2470 | return ERR_CAST(new); |
| 2471 | } |
| 2472 | new_ns->root = new; |
| 2473 | list_add_tail(&new_ns->list, &new->mnt_list); |
| 2474 | |
| 2475 | /* |
| 2476 | * Second pass: switch the tsk->fs->* elements and mark new vfsmounts |
| 2477 | * as belonging to new namespace. We have already acquired a private |
| 2478 | * fs_struct, so tsk->fs->lock is not needed. |
| 2479 | */ |
| 2480 | p = old; |
| 2481 | q = new; |
| 2482 | while (p) { |
| 2483 | q->mnt_ns = new_ns; |
| 2484 | if (new_fs) { |
| 2485 | if (&p->mnt == new_fs->root.mnt) { |
| 2486 | new_fs->root.mnt = mntget(&q->mnt); |
| 2487 | rootmnt = &p->mnt; |
| 2488 | } |
| 2489 | if (&p->mnt == new_fs->pwd.mnt) { |
| 2490 | new_fs->pwd.mnt = mntget(&q->mnt); |
| 2491 | pwdmnt = &p->mnt; |
| 2492 | } |
| 2493 | } |
| 2494 | p = next_mnt(p, old); |
| 2495 | q = next_mnt(q, new); |
| 2496 | if (!q) |
| 2497 | break; |
| 2498 | while (p->mnt.mnt_root != q->mnt.mnt_root) |
| 2499 | p = next_mnt(p, old); |
| 2500 | } |
| 2501 | namespace_unlock(); |
| 2502 | |
| 2503 | if (rootmnt) |
| 2504 | mntput(rootmnt); |
| 2505 | if (pwdmnt) |
| 2506 | mntput(pwdmnt); |
| 2507 | |
| 2508 | return new_ns; |
| 2509 | } |
| 2510 | |
| 2511 | /** |
| 2512 | * create_mnt_ns - creates a private namespace and adds a root filesystem |
| 2513 | * @mnt: pointer to the new root filesystem mountpoint |
| 2514 | */ |
| 2515 | static struct mnt_namespace *create_mnt_ns(struct vfsmount *m) |
| 2516 | { |
| 2517 | struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns); |
| 2518 | if (!IS_ERR(new_ns)) { |
| 2519 | struct mount *mnt = real_mount(m); |
| 2520 | mnt->mnt_ns = new_ns; |
| 2521 | new_ns->root = mnt; |
| 2522 | list_add(&mnt->mnt_list, &new_ns->list); |
| 2523 | } else { |
| 2524 | mntput(m); |
| 2525 | } |
| 2526 | return new_ns; |
| 2527 | } |
| 2528 | |
| 2529 | struct dentry *mount_subtree(struct vfsmount *mnt, const char *name) |
| 2530 | { |
| 2531 | struct mnt_namespace *ns; |
| 2532 | struct super_block *s; |
| 2533 | struct path path; |
| 2534 | int err; |
| 2535 | |
| 2536 | ns = create_mnt_ns(mnt); |
| 2537 | if (IS_ERR(ns)) |
| 2538 | return ERR_CAST(ns); |
| 2539 | |
| 2540 | err = vfs_path_lookup(mnt->mnt_root, mnt, |
| 2541 | name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); |
| 2542 | |
| 2543 | put_mnt_ns(ns); |
| 2544 | |
| 2545 | if (err) |
| 2546 | return ERR_PTR(err); |
| 2547 | |
| 2548 | /* trade a vfsmount reference for active sb one */ |
| 2549 | s = path.mnt->mnt_sb; |
| 2550 | atomic_inc(&s->s_active); |
| 2551 | mntput(path.mnt); |
| 2552 | /* lock the sucker */ |
| 2553 | down_write(&s->s_umount); |
| 2554 | /* ... and return the root of (sub)tree on it */ |
| 2555 | return path.dentry; |
| 2556 | } |
| 2557 | EXPORT_SYMBOL(mount_subtree); |
| 2558 | |
| 2559 | SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, |
| 2560 | char __user *, type, unsigned long, flags, void __user *, data) |
| 2561 | { |
| 2562 | int ret; |
| 2563 | char *kernel_type; |
| 2564 | struct filename *kernel_dir; |
| 2565 | char *kernel_dev; |
| 2566 | unsigned long data_page; |
| 2567 | |
| 2568 | ret = copy_mount_string(type, &kernel_type); |
| 2569 | if (ret < 0) |
| 2570 | goto out_type; |
| 2571 | |
| 2572 | kernel_dir = getname(dir_name); |
| 2573 | if (IS_ERR(kernel_dir)) { |
| 2574 | ret = PTR_ERR(kernel_dir); |
| 2575 | goto out_dir; |
| 2576 | } |
| 2577 | |
| 2578 | ret = copy_mount_string(dev_name, &kernel_dev); |
| 2579 | if (ret < 0) |
| 2580 | goto out_dev; |
| 2581 | |
| 2582 | ret = copy_mount_options(data, &data_page); |
| 2583 | if (ret < 0) |
| 2584 | goto out_data; |
| 2585 | |
| 2586 | ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags, |
| 2587 | (void *) data_page); |
| 2588 | |
| 2589 | free_page(data_page); |
| 2590 | out_data: |
| 2591 | kfree(kernel_dev); |
| 2592 | out_dev: |
| 2593 | putname(kernel_dir); |
| 2594 | out_dir: |
| 2595 | kfree(kernel_type); |
| 2596 | out_type: |
| 2597 | return ret; |
| 2598 | } |
| 2599 | |
| 2600 | /* |
| 2601 | * Return true if path is reachable from root |
| 2602 | * |
| 2603 | * namespace_sem or mount_lock is held |
| 2604 | */ |
| 2605 | bool is_path_reachable(struct mount *mnt, struct dentry *dentry, |
| 2606 | const struct path *root) |
| 2607 | { |
| 2608 | while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) { |
| 2609 | dentry = mnt->mnt_mountpoint; |
| 2610 | mnt = mnt->mnt_parent; |
| 2611 | } |
| 2612 | return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry); |
| 2613 | } |
| 2614 | |
| 2615 | int path_is_under(struct path *path1, struct path *path2) |
| 2616 | { |
| 2617 | int res; |
| 2618 | read_seqlock_excl(&mount_lock); |
| 2619 | res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2); |
| 2620 | read_sequnlock_excl(&mount_lock); |
| 2621 | return res; |
| 2622 | } |
| 2623 | EXPORT_SYMBOL(path_is_under); |
| 2624 | |
| 2625 | /* |
| 2626 | * pivot_root Semantics: |
| 2627 | * Moves the root file system of the current process to the directory put_old, |
| 2628 | * makes new_root as the new root file system of the current process, and sets |
| 2629 | * root/cwd of all processes which had them on the current root to new_root. |
| 2630 | * |
| 2631 | * Restrictions: |
| 2632 | * The new_root and put_old must be directories, and must not be on the |
| 2633 | * same file system as the current process root. The put_old must be |
| 2634 | * underneath new_root, i.e. adding a non-zero number of /.. to the string |
| 2635 | * pointed to by put_old must yield the same directory as new_root. No other |
| 2636 | * file system may be mounted on put_old. After all, new_root is a mountpoint. |
| 2637 | * |
| 2638 | * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. |
| 2639 | * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives |
| 2640 | * in this situation. |
| 2641 | * |
| 2642 | * Notes: |
| 2643 | * - we don't move root/cwd if they are not at the root (reason: if something |
| 2644 | * cared enough to change them, it's probably wrong to force them elsewhere) |
| 2645 | * - it's okay to pick a root that isn't the root of a file system, e.g. |
| 2646 | * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, |
| 2647 | * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root |
| 2648 | * first. |
| 2649 | */ |
| 2650 | SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, |
| 2651 | const char __user *, put_old) |
| 2652 | { |
| 2653 | struct path new, old, parent_path, root_parent, root; |
| 2654 | struct mount *new_mnt, *root_mnt, *old_mnt; |
| 2655 | struct mountpoint *old_mp, *root_mp; |
| 2656 | int error; |
| 2657 | |
| 2658 | if (!may_mount()) |
| 2659 | return -EPERM; |
| 2660 | |
| 2661 | error = user_path_dir(new_root, &new); |
| 2662 | if (error) |
| 2663 | goto out0; |
| 2664 | |
| 2665 | error = user_path_dir(put_old, &old); |
| 2666 | if (error) |
| 2667 | goto out1; |
| 2668 | |
| 2669 | error = security_sb_pivotroot(&old, &new); |
| 2670 | if (error) |
| 2671 | goto out2; |
| 2672 | |
| 2673 | get_fs_root(current->fs, &root); |
| 2674 | old_mp = lock_mount(&old); |
| 2675 | error = PTR_ERR(old_mp); |
| 2676 | if (IS_ERR(old_mp)) |
| 2677 | goto out3; |
| 2678 | |
| 2679 | error = -EINVAL; |
| 2680 | new_mnt = real_mount(new.mnt); |
| 2681 | root_mnt = real_mount(root.mnt); |
| 2682 | old_mnt = real_mount(old.mnt); |
| 2683 | if (IS_MNT_SHARED(old_mnt) || |
| 2684 | IS_MNT_SHARED(new_mnt->mnt_parent) || |
| 2685 | IS_MNT_SHARED(root_mnt->mnt_parent)) |
| 2686 | goto out4; |
| 2687 | if (!check_mnt(root_mnt) || !check_mnt(new_mnt)) |
| 2688 | goto out4; |
| 2689 | if (new_mnt->mnt.mnt_flags & MNT_LOCKED) |
| 2690 | goto out4; |
| 2691 | error = -ENOENT; |
| 2692 | if (d_unlinked(new.dentry)) |
| 2693 | goto out4; |
| 2694 | error = -EBUSY; |
| 2695 | if (new_mnt == root_mnt || old_mnt == root_mnt) |
| 2696 | goto out4; /* loop, on the same file system */ |
| 2697 | error = -EINVAL; |
| 2698 | if (root.mnt->mnt_root != root.dentry) |
| 2699 | goto out4; /* not a mountpoint */ |
| 2700 | if (!mnt_has_parent(root_mnt)) |
| 2701 | goto out4; /* not attached */ |
| 2702 | root_mp = root_mnt->mnt_mp; |
| 2703 | if (new.mnt->mnt_root != new.dentry) |
| 2704 | goto out4; /* not a mountpoint */ |
| 2705 | if (!mnt_has_parent(new_mnt)) |
| 2706 | goto out4; /* not attached */ |
| 2707 | /* make sure we can reach put_old from new_root */ |
| 2708 | if (!is_path_reachable(old_mnt, old.dentry, &new)) |
| 2709 | goto out4; |
| 2710 | root_mp->m_count++; /* pin it so it won't go away */ |
| 2711 | lock_mount_hash(); |
| 2712 | detach_mnt(new_mnt, &parent_path); |
| 2713 | detach_mnt(root_mnt, &root_parent); |
| 2714 | if (root_mnt->mnt.mnt_flags & MNT_LOCKED) { |
| 2715 | new_mnt->mnt.mnt_flags |= MNT_LOCKED; |
| 2716 | root_mnt->mnt.mnt_flags &= ~MNT_LOCKED; |
| 2717 | } |
| 2718 | /* mount old root on put_old */ |
| 2719 | attach_mnt(root_mnt, old_mnt, old_mp); |
| 2720 | /* mount new_root on / */ |
| 2721 | attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp); |
| 2722 | touch_mnt_namespace(current->nsproxy->mnt_ns); |
| 2723 | unlock_mount_hash(); |
| 2724 | chroot_fs_refs(&root, &new); |
| 2725 | put_mountpoint(root_mp); |
| 2726 | error = 0; |
| 2727 | out4: |
| 2728 | unlock_mount(old_mp); |
| 2729 | if (!error) { |
| 2730 | path_put(&root_parent); |
| 2731 | path_put(&parent_path); |
| 2732 | } |
| 2733 | out3: |
| 2734 | path_put(&root); |
| 2735 | out2: |
| 2736 | path_put(&old); |
| 2737 | out1: |
| 2738 | path_put(&new); |
| 2739 | out0: |
| 2740 | return error; |
| 2741 | } |
| 2742 | |
| 2743 | static void __init init_mount_tree(void) |
| 2744 | { |
| 2745 | struct vfsmount *mnt; |
| 2746 | struct mnt_namespace *ns; |
| 2747 | struct path root; |
| 2748 | struct file_system_type *type; |
| 2749 | |
| 2750 | type = get_fs_type("rootfs"); |
| 2751 | if (!type) |
| 2752 | panic("Can't find rootfs type"); |
| 2753 | mnt = vfs_kern_mount(type, 0, "rootfs", NULL); |
| 2754 | put_filesystem(type); |
| 2755 | if (IS_ERR(mnt)) |
| 2756 | panic("Can't create rootfs"); |
| 2757 | |
| 2758 | ns = create_mnt_ns(mnt); |
| 2759 | if (IS_ERR(ns)) |
| 2760 | panic("Can't allocate initial namespace"); |
| 2761 | |
| 2762 | init_task.nsproxy->mnt_ns = ns; |
| 2763 | get_mnt_ns(ns); |
| 2764 | |
| 2765 | root.mnt = mnt; |
| 2766 | root.dentry = mnt->mnt_root; |
| 2767 | |
| 2768 | set_fs_pwd(current->fs, &root); |
| 2769 | set_fs_root(current->fs, &root); |
| 2770 | } |
| 2771 | |
| 2772 | void __init mnt_init(void) |
| 2773 | { |
| 2774 | unsigned u; |
| 2775 | int err; |
| 2776 | |
| 2777 | mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount), |
| 2778 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); |
| 2779 | |
| 2780 | mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); |
| 2781 | mountpoint_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); |
| 2782 | |
| 2783 | if (!mount_hashtable || !mountpoint_hashtable) |
| 2784 | panic("Failed to allocate mount hash table\n"); |
| 2785 | |
| 2786 | printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE); |
| 2787 | |
| 2788 | for (u = 0; u < HASH_SIZE; u++) |
| 2789 | INIT_LIST_HEAD(&mount_hashtable[u]); |
| 2790 | for (u = 0; u < HASH_SIZE; u++) |
| 2791 | INIT_LIST_HEAD(&mountpoint_hashtable[u]); |
| 2792 | |
| 2793 | err = sysfs_init(); |
| 2794 | if (err) |
| 2795 | printk(KERN_WARNING "%s: sysfs_init error: %d\n", |
| 2796 | __func__, err); |
| 2797 | fs_kobj = kobject_create_and_add("fs", NULL); |
| 2798 | if (!fs_kobj) |
| 2799 | printk(KERN_WARNING "%s: kobj create error\n", __func__); |
| 2800 | init_rootfs(); |
| 2801 | init_mount_tree(); |
| 2802 | } |
| 2803 | |
| 2804 | void put_mnt_ns(struct mnt_namespace *ns) |
| 2805 | { |
| 2806 | if (!atomic_dec_and_test(&ns->count)) |
| 2807 | return; |
| 2808 | drop_collected_mounts(&ns->root->mnt); |
| 2809 | free_mnt_ns(ns); |
| 2810 | } |
| 2811 | |
| 2812 | struct vfsmount *kern_mount_data(struct file_system_type *type, void *data) |
| 2813 | { |
| 2814 | struct vfsmount *mnt; |
| 2815 | mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data); |
| 2816 | if (!IS_ERR(mnt)) { |
| 2817 | /* |
| 2818 | * it is a longterm mount, don't release mnt until |
| 2819 | * we unmount before file sys is unregistered |
| 2820 | */ |
| 2821 | real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL; |
| 2822 | } |
| 2823 | return mnt; |
| 2824 | } |
| 2825 | EXPORT_SYMBOL_GPL(kern_mount_data); |
| 2826 | |
| 2827 | void kern_unmount(struct vfsmount *mnt) |
| 2828 | { |
| 2829 | /* release long term mount so mount point can be released */ |
| 2830 | if (!IS_ERR_OR_NULL(mnt)) { |
| 2831 | real_mount(mnt)->mnt_ns = NULL; |
| 2832 | synchronize_rcu(); /* yecchhh... */ |
| 2833 | mntput(mnt); |
| 2834 | } |
| 2835 | } |
| 2836 | EXPORT_SYMBOL(kern_unmount); |
| 2837 | |
| 2838 | bool our_mnt(struct vfsmount *mnt) |
| 2839 | { |
| 2840 | return check_mnt(real_mount(mnt)); |
| 2841 | } |
| 2842 | |
| 2843 | bool current_chrooted(void) |
| 2844 | { |
| 2845 | /* Does the current process have a non-standard root */ |
| 2846 | struct path ns_root; |
| 2847 | struct path fs_root; |
| 2848 | bool chrooted; |
| 2849 | |
| 2850 | /* Find the namespace root */ |
| 2851 | ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt; |
| 2852 | ns_root.dentry = ns_root.mnt->mnt_root; |
| 2853 | path_get(&ns_root); |
| 2854 | while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root)) |
| 2855 | ; |
| 2856 | |
| 2857 | get_fs_root(current->fs, &fs_root); |
| 2858 | |
| 2859 | chrooted = !path_equal(&fs_root, &ns_root); |
| 2860 | |
| 2861 | path_put(&fs_root); |
| 2862 | path_put(&ns_root); |
| 2863 | |
| 2864 | return chrooted; |
| 2865 | } |
| 2866 | |
| 2867 | bool fs_fully_visible(struct file_system_type *type) |
| 2868 | { |
| 2869 | struct mnt_namespace *ns = current->nsproxy->mnt_ns; |
| 2870 | struct mount *mnt; |
| 2871 | bool visible = false; |
| 2872 | |
| 2873 | if (unlikely(!ns)) |
| 2874 | return false; |
| 2875 | |
| 2876 | down_read(&namespace_sem); |
| 2877 | list_for_each_entry(mnt, &ns->list, mnt_list) { |
| 2878 | struct mount *child; |
| 2879 | if (mnt->mnt.mnt_sb->s_type != type) |
| 2880 | continue; |
| 2881 | |
| 2882 | /* This mount is not fully visible if there are any child mounts |
| 2883 | * that cover anything except for empty directories. |
| 2884 | */ |
| 2885 | list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { |
| 2886 | struct inode *inode = child->mnt_mountpoint->d_inode; |
| 2887 | if (!S_ISDIR(inode->i_mode)) |
| 2888 | goto next; |
| 2889 | if (inode->i_nlink != 2) |
| 2890 | goto next; |
| 2891 | } |
| 2892 | visible = true; |
| 2893 | goto found; |
| 2894 | next: ; |
| 2895 | } |
| 2896 | found: |
| 2897 | up_read(&namespace_sem); |
| 2898 | return visible; |
| 2899 | } |
| 2900 | |
| 2901 | static void *mntns_get(struct task_struct *task) |
| 2902 | { |
| 2903 | struct mnt_namespace *ns = NULL; |
| 2904 | struct nsproxy *nsproxy; |
| 2905 | |
| 2906 | rcu_read_lock(); |
| 2907 | nsproxy = task_nsproxy(task); |
| 2908 | if (nsproxy) { |
| 2909 | ns = nsproxy->mnt_ns; |
| 2910 | get_mnt_ns(ns); |
| 2911 | } |
| 2912 | rcu_read_unlock(); |
| 2913 | |
| 2914 | return ns; |
| 2915 | } |
| 2916 | |
| 2917 | static void mntns_put(void *ns) |
| 2918 | { |
| 2919 | put_mnt_ns(ns); |
| 2920 | } |
| 2921 | |
| 2922 | static int mntns_install(struct nsproxy *nsproxy, void *ns) |
| 2923 | { |
| 2924 | struct fs_struct *fs = current->fs; |
| 2925 | struct mnt_namespace *mnt_ns = ns; |
| 2926 | struct path root; |
| 2927 | |
| 2928 | if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) || |
| 2929 | !ns_capable(current_user_ns(), CAP_SYS_CHROOT) || |
| 2930 | !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) |
| 2931 | return -EPERM; |
| 2932 | |
| 2933 | if (fs->users != 1) |
| 2934 | return -EINVAL; |
| 2935 | |
| 2936 | get_mnt_ns(mnt_ns); |
| 2937 | put_mnt_ns(nsproxy->mnt_ns); |
| 2938 | nsproxy->mnt_ns = mnt_ns; |
| 2939 | |
| 2940 | /* Find the root */ |
| 2941 | root.mnt = &mnt_ns->root->mnt; |
| 2942 | root.dentry = mnt_ns->root->mnt.mnt_root; |
| 2943 | path_get(&root); |
| 2944 | while(d_mountpoint(root.dentry) && follow_down_one(&root)) |
| 2945 | ; |
| 2946 | |
| 2947 | /* Update the pwd and root */ |
| 2948 | set_fs_pwd(fs, &root); |
| 2949 | set_fs_root(fs, &root); |
| 2950 | |
| 2951 | path_put(&root); |
| 2952 | return 0; |
| 2953 | } |
| 2954 | |
| 2955 | static unsigned int mntns_inum(void *ns) |
| 2956 | { |
| 2957 | struct mnt_namespace *mnt_ns = ns; |
| 2958 | return mnt_ns->proc_inum; |
| 2959 | } |
| 2960 | |
| 2961 | const struct proc_ns_operations mntns_operations = { |
| 2962 | .name = "mnt", |
| 2963 | .type = CLONE_NEWNS, |
| 2964 | .get = mntns_get, |
| 2965 | .put = mntns_put, |
| 2966 | .install = mntns_install, |
| 2967 | .inum = mntns_inum, |
| 2968 | }; |