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Source at commit 2604e7f9a98c27be50a0c3ff7503b6a5ea8f6cfe created 12 years 7 months ago. By Maarten ter Huurne, cpufreq_stats: Support runtime changes to frequency table | |
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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/namei.h> |
16 | #include <linux/security.h> |
17 | #include <linux/idr.h> |
18 | #include <linux/acct.h> /* acct_auto_close_mnt */ |
19 | #include <linux/ramfs.h> /* init_rootfs */ |
20 | #include <linux/fs_struct.h> /* get_fs_root et.al. */ |
21 | #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */ |
22 | #include <linux/uaccess.h> |
23 | #include "pnode.h" |
24 | #include "internal.h" |
25 | |
26 | #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head)) |
27 | #define HASH_SIZE (1UL << HASH_SHIFT) |
28 | |
29 | static int event; |
30 | static DEFINE_IDA(mnt_id_ida); |
31 | static DEFINE_IDA(mnt_group_ida); |
32 | static DEFINE_SPINLOCK(mnt_id_lock); |
33 | static int mnt_id_start = 0; |
34 | static int mnt_group_start = 1; |
35 | |
36 | static struct list_head *mount_hashtable __read_mostly; |
37 | static struct kmem_cache *mnt_cache __read_mostly; |
38 | static struct rw_semaphore namespace_sem; |
39 | |
40 | /* /sys/fs */ |
41 | struct kobject *fs_kobj; |
42 | EXPORT_SYMBOL_GPL(fs_kobj); |
43 | |
44 | /* |
45 | * vfsmount lock may be taken for read to prevent changes to the |
46 | * vfsmount hash, ie. during mountpoint lookups or walking back |
47 | * up the tree. |
48 | * |
49 | * It should be taken for write in all cases where the vfsmount |
50 | * tree or hash is modified or when a vfsmount structure is modified. |
51 | */ |
52 | DEFINE_BRLOCK(vfsmount_lock); |
53 | |
54 | static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) |
55 | { |
56 | unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); |
57 | tmp += ((unsigned long)dentry / L1_CACHE_BYTES); |
58 | tmp = tmp + (tmp >> HASH_SHIFT); |
59 | return tmp & (HASH_SIZE - 1); |
60 | } |
61 | |
62 | #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16) |
63 | |
64 | /* |
65 | * allocation is serialized by namespace_sem, but we need the spinlock to |
66 | * serialize with freeing. |
67 | */ |
68 | static int mnt_alloc_id(struct mount *mnt) |
69 | { |
70 | int res; |
71 | |
72 | retry: |
73 | ida_pre_get(&mnt_id_ida, GFP_KERNEL); |
74 | spin_lock(&mnt_id_lock); |
75 | res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id); |
76 | if (!res) |
77 | mnt_id_start = mnt->mnt_id + 1; |
78 | spin_unlock(&mnt_id_lock); |
79 | if (res == -EAGAIN) |
80 | goto retry; |
81 | |
82 | return res; |
83 | } |
84 | |
85 | static void mnt_free_id(struct mount *mnt) |
86 | { |
87 | int id = mnt->mnt_id; |
88 | spin_lock(&mnt_id_lock); |
89 | ida_remove(&mnt_id_ida, id); |
90 | if (mnt_id_start > id) |
91 | mnt_id_start = id; |
92 | spin_unlock(&mnt_id_lock); |
93 | } |
94 | |
95 | /* |
96 | * Allocate a new peer group ID |
97 | * |
98 | * mnt_group_ida is protected by namespace_sem |
99 | */ |
100 | static int mnt_alloc_group_id(struct mount *mnt) |
101 | { |
102 | int res; |
103 | |
104 | if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL)) |
105 | return -ENOMEM; |
106 | |
107 | res = ida_get_new_above(&mnt_group_ida, |
108 | mnt_group_start, |
109 | &mnt->mnt_group_id); |
110 | if (!res) |
111 | mnt_group_start = mnt->mnt_group_id + 1; |
112 | |
113 | return res; |
114 | } |
115 | |
116 | /* |
117 | * Release a peer group ID |
118 | */ |
119 | void mnt_release_group_id(struct mount *mnt) |
120 | { |
121 | int id = mnt->mnt_group_id; |
122 | ida_remove(&mnt_group_ida, id); |
123 | if (mnt_group_start > id) |
124 | mnt_group_start = id; |
125 | mnt->mnt_group_id = 0; |
126 | } |
127 | |
128 | /* |
129 | * vfsmount lock must be held for read |
130 | */ |
131 | static inline void mnt_add_count(struct mount *mnt, int n) |
132 | { |
133 | #ifdef CONFIG_SMP |
134 | this_cpu_add(mnt->mnt_pcp->mnt_count, n); |
135 | #else |
136 | preempt_disable(); |
137 | mnt->mnt_count += n; |
138 | preempt_enable(); |
139 | #endif |
140 | } |
141 | |
142 | /* |
143 | * vfsmount lock must be held for write |
144 | */ |
145 | unsigned int mnt_get_count(struct mount *mnt) |
146 | { |
147 | #ifdef CONFIG_SMP |
148 | unsigned int count = 0; |
149 | int cpu; |
150 | |
151 | for_each_possible_cpu(cpu) { |
152 | count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count; |
153 | } |
154 | |
155 | return count; |
156 | #else |
157 | return mnt->mnt_count; |
158 | #endif |
159 | } |
160 | |
161 | static struct mount *alloc_vfsmnt(const char *name) |
162 | { |
163 | struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); |
164 | if (mnt) { |
165 | int err; |
166 | |
167 | err = mnt_alloc_id(mnt); |
168 | if (err) |
169 | goto out_free_cache; |
170 | |
171 | if (name) { |
172 | mnt->mnt_devname = kstrdup(name, GFP_KERNEL); |
173 | if (!mnt->mnt_devname) |
174 | goto out_free_id; |
175 | } |
176 | |
177 | #ifdef CONFIG_SMP |
178 | mnt->mnt_pcp = alloc_percpu(struct mnt_pcp); |
179 | if (!mnt->mnt_pcp) |
180 | goto out_free_devname; |
181 | |
182 | this_cpu_add(mnt->mnt_pcp->mnt_count, 1); |
183 | #else |
184 | mnt->mnt_count = 1; |
185 | mnt->mnt_writers = 0; |
186 | #endif |
187 | |
188 | INIT_LIST_HEAD(&mnt->mnt_hash); |
189 | INIT_LIST_HEAD(&mnt->mnt_child); |
190 | INIT_LIST_HEAD(&mnt->mnt_mounts); |
191 | INIT_LIST_HEAD(&mnt->mnt_list); |
192 | INIT_LIST_HEAD(&mnt->mnt_expire); |
193 | INIT_LIST_HEAD(&mnt->mnt_share); |
194 | INIT_LIST_HEAD(&mnt->mnt_slave_list); |
195 | INIT_LIST_HEAD(&mnt->mnt_slave); |
196 | #ifdef CONFIG_FSNOTIFY |
197 | INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks); |
198 | #endif |
199 | } |
200 | return mnt; |
201 | |
202 | #ifdef CONFIG_SMP |
203 | out_free_devname: |
204 | kfree(mnt->mnt_devname); |
205 | #endif |
206 | out_free_id: |
207 | mnt_free_id(mnt); |
208 | out_free_cache: |
209 | kmem_cache_free(mnt_cache, mnt); |
210 | return NULL; |
211 | } |
212 | |
213 | /* |
214 | * Most r/o checks on a fs are for operations that take |
215 | * discrete amounts of time, like a write() or unlink(). |
216 | * We must keep track of when those operations start |
217 | * (for permission checks) and when they end, so that |
218 | * we can determine when writes are able to occur to |
219 | * a filesystem. |
220 | */ |
221 | /* |
222 | * __mnt_is_readonly: check whether a mount is read-only |
223 | * @mnt: the mount to check for its write status |
224 | * |
225 | * This shouldn't be used directly ouside of the VFS. |
226 | * It does not guarantee that the filesystem will stay |
227 | * r/w, just that it is right *now*. This can not and |
228 | * should not be used in place of IS_RDONLY(inode). |
229 | * mnt_want/drop_write() will _keep_ the filesystem |
230 | * r/w. |
231 | */ |
232 | int __mnt_is_readonly(struct vfsmount *mnt) |
233 | { |
234 | if (mnt->mnt_flags & MNT_READONLY) |
235 | return 1; |
236 | if (mnt->mnt_sb->s_flags & MS_RDONLY) |
237 | return 1; |
238 | return 0; |
239 | } |
240 | EXPORT_SYMBOL_GPL(__mnt_is_readonly); |
241 | |
242 | static inline void mnt_inc_writers(struct mount *mnt) |
243 | { |
244 | #ifdef CONFIG_SMP |
245 | this_cpu_inc(mnt->mnt_pcp->mnt_writers); |
246 | #else |
247 | mnt->mnt_writers++; |
248 | #endif |
249 | } |
250 | |
251 | static inline void mnt_dec_writers(struct mount *mnt) |
252 | { |
253 | #ifdef CONFIG_SMP |
254 | this_cpu_dec(mnt->mnt_pcp->mnt_writers); |
255 | #else |
256 | mnt->mnt_writers--; |
257 | #endif |
258 | } |
259 | |
260 | static unsigned int mnt_get_writers(struct mount *mnt) |
261 | { |
262 | #ifdef CONFIG_SMP |
263 | unsigned int count = 0; |
264 | int cpu; |
265 | |
266 | for_each_possible_cpu(cpu) { |
267 | count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers; |
268 | } |
269 | |
270 | return count; |
271 | #else |
272 | return mnt->mnt_writers; |
273 | #endif |
274 | } |
275 | |
276 | static int mnt_is_readonly(struct vfsmount *mnt) |
277 | { |
278 | if (mnt->mnt_sb->s_readonly_remount) |
279 | return 1; |
280 | /* Order wrt setting s_flags/s_readonly_remount in do_remount() */ |
281 | smp_rmb(); |
282 | return __mnt_is_readonly(mnt); |
283 | } |
284 | |
285 | /* |
286 | * Most r/o & frozen checks on a fs are for operations that take discrete |
287 | * amounts of time, like a write() or unlink(). We must keep track of when |
288 | * those operations start (for permission checks) and when they end, so that we |
289 | * can determine when writes are able to occur to a filesystem. |
290 | */ |
291 | /** |
292 | * __mnt_want_write - get write access to a mount without freeze protection |
293 | * @m: the mount on which to take a write |
294 | * |
295 | * This tells the low-level filesystem that a write is about to be performed to |
296 | * it, and makes sure that writes are allowed (mnt it read-write) before |
297 | * returning success. This operation does not protect against filesystem being |
298 | * frozen. When the write operation is finished, __mnt_drop_write() must be |
299 | * called. This is effectively a refcount. |
300 | */ |
301 | int __mnt_want_write(struct vfsmount *m) |
302 | { |
303 | struct mount *mnt = real_mount(m); |
304 | int ret = 0; |
305 | |
306 | preempt_disable(); |
307 | mnt_inc_writers(mnt); |
308 | /* |
309 | * The store to mnt_inc_writers must be visible before we pass |
310 | * MNT_WRITE_HOLD loop below, so that the slowpath can see our |
311 | * incremented count after it has set MNT_WRITE_HOLD. |
312 | */ |
313 | smp_mb(); |
314 | while (mnt->mnt.mnt_flags & MNT_WRITE_HOLD) |
315 | cpu_relax(); |
316 | /* |
317 | * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will |
318 | * be set to match its requirements. So we must not load that until |
319 | * MNT_WRITE_HOLD is cleared. |
320 | */ |
321 | smp_rmb(); |
322 | if (mnt_is_readonly(m)) { |
323 | mnt_dec_writers(mnt); |
324 | ret = -EROFS; |
325 | } |
326 | preempt_enable(); |
327 | |
328 | return ret; |
329 | } |
330 | |
331 | /** |
332 | * mnt_want_write - get write access to a mount |
333 | * @m: the mount on which to take a write |
334 | * |
335 | * This tells the low-level filesystem that a write is about to be performed to |
336 | * it, and makes sure that writes are allowed (mount is read-write, filesystem |
337 | * is not frozen) before returning success. When the write operation is |
338 | * finished, mnt_drop_write() must be called. This is effectively a refcount. |
339 | */ |
340 | int mnt_want_write(struct vfsmount *m) |
341 | { |
342 | int ret; |
343 | |
344 | sb_start_write(m->mnt_sb); |
345 | ret = __mnt_want_write(m); |
346 | if (ret) |
347 | sb_end_write(m->mnt_sb); |
348 | return ret; |
349 | } |
350 | EXPORT_SYMBOL_GPL(mnt_want_write); |
351 | |
352 | /** |
353 | * mnt_clone_write - get write access to a mount |
354 | * @mnt: the mount on which to take a write |
355 | * |
356 | * This is effectively like mnt_want_write, except |
357 | * it must only be used to take an extra write reference |
358 | * on a mountpoint that we already know has a write reference |
359 | * on it. This allows some optimisation. |
360 | * |
361 | * After finished, mnt_drop_write must be called as usual to |
362 | * drop the reference. |
363 | */ |
364 | int mnt_clone_write(struct vfsmount *mnt) |
365 | { |
366 | /* superblock may be r/o */ |
367 | if (__mnt_is_readonly(mnt)) |
368 | return -EROFS; |
369 | preempt_disable(); |
370 | mnt_inc_writers(real_mount(mnt)); |
371 | preempt_enable(); |
372 | return 0; |
373 | } |
374 | EXPORT_SYMBOL_GPL(mnt_clone_write); |
375 | |
376 | /** |
377 | * __mnt_want_write_file - get write access to a file's mount |
378 | * @file: the file who's mount on which to take a write |
379 | * |
380 | * This is like __mnt_want_write, but it takes a file and can |
381 | * do some optimisations if the file is open for write already |
382 | */ |
383 | int __mnt_want_write_file(struct file *file) |
384 | { |
385 | struct inode *inode = file->f_dentry->d_inode; |
386 | |
387 | if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode)) |
388 | return __mnt_want_write(file->f_path.mnt); |
389 | else |
390 | return mnt_clone_write(file->f_path.mnt); |
391 | } |
392 | |
393 | /** |
394 | * mnt_want_write_file - get write access to a file's mount |
395 | * @file: the file who's mount on which to take a write |
396 | * |
397 | * This is like mnt_want_write, but it takes a file and can |
398 | * do some optimisations if the file is open for write already |
399 | */ |
400 | int mnt_want_write_file(struct file *file) |
401 | { |
402 | int ret; |
403 | |
404 | sb_start_write(file->f_path.mnt->mnt_sb); |
405 | ret = __mnt_want_write_file(file); |
406 | if (ret) |
407 | sb_end_write(file->f_path.mnt->mnt_sb); |
408 | return ret; |
409 | } |
410 | EXPORT_SYMBOL_GPL(mnt_want_write_file); |
411 | |
412 | /** |
413 | * __mnt_drop_write - give up write access to a mount |
414 | * @mnt: the mount on which to give up write access |
415 | * |
416 | * Tells the low-level filesystem that we are done |
417 | * performing writes to it. Must be matched with |
418 | * __mnt_want_write() call above. |
419 | */ |
420 | void __mnt_drop_write(struct vfsmount *mnt) |
421 | { |
422 | preempt_disable(); |
423 | mnt_dec_writers(real_mount(mnt)); |
424 | preempt_enable(); |
425 | } |
426 | |
427 | /** |
428 | * mnt_drop_write - give up write access to a mount |
429 | * @mnt: the mount on which to give up write access |
430 | * |
431 | * Tells the low-level filesystem that we are done performing writes to it and |
432 | * also allows filesystem to be frozen again. Must be matched with |
433 | * mnt_want_write() call above. |
434 | */ |
435 | void mnt_drop_write(struct vfsmount *mnt) |
436 | { |
437 | __mnt_drop_write(mnt); |
438 | sb_end_write(mnt->mnt_sb); |
439 | } |
440 | EXPORT_SYMBOL_GPL(mnt_drop_write); |
441 | |
442 | void __mnt_drop_write_file(struct file *file) |
443 | { |
444 | __mnt_drop_write(file->f_path.mnt); |
445 | } |
446 | |
447 | void mnt_drop_write_file(struct file *file) |
448 | { |
449 | mnt_drop_write(file->f_path.mnt); |
450 | } |
451 | EXPORT_SYMBOL(mnt_drop_write_file); |
452 | |
453 | static int mnt_make_readonly(struct mount *mnt) |
454 | { |
455 | int ret = 0; |
456 | |
457 | br_write_lock(&vfsmount_lock); |
458 | mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; |
459 | /* |
460 | * After storing MNT_WRITE_HOLD, we'll read the counters. This store |
461 | * should be visible before we do. |
462 | */ |
463 | smp_mb(); |
464 | |
465 | /* |
466 | * With writers on hold, if this value is zero, then there are |
467 | * definitely no active writers (although held writers may subsequently |
468 | * increment the count, they'll have to wait, and decrement it after |
469 | * seeing MNT_READONLY). |
470 | * |
471 | * It is OK to have counter incremented on one CPU and decremented on |
472 | * another: the sum will add up correctly. The danger would be when we |
473 | * sum up each counter, if we read a counter before it is incremented, |
474 | * but then read another CPU's count which it has been subsequently |
475 | * decremented from -- we would see more decrements than we should. |
476 | * MNT_WRITE_HOLD protects against this scenario, because |
477 | * mnt_want_write first increments count, then smp_mb, then spins on |
478 | * MNT_WRITE_HOLD, so it can't be decremented by another CPU while |
479 | * we're counting up here. |
480 | */ |
481 | if (mnt_get_writers(mnt) > 0) |
482 | ret = -EBUSY; |
483 | else |
484 | mnt->mnt.mnt_flags |= MNT_READONLY; |
485 | /* |
486 | * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers |
487 | * that become unheld will see MNT_READONLY. |
488 | */ |
489 | smp_wmb(); |
490 | mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; |
491 | br_write_unlock(&vfsmount_lock); |
492 | return ret; |
493 | } |
494 | |
495 | static void __mnt_unmake_readonly(struct mount *mnt) |
496 | { |
497 | br_write_lock(&vfsmount_lock); |
498 | mnt->mnt.mnt_flags &= ~MNT_READONLY; |
499 | br_write_unlock(&vfsmount_lock); |
500 | } |
501 | |
502 | int sb_prepare_remount_readonly(struct super_block *sb) |
503 | { |
504 | struct mount *mnt; |
505 | int err = 0; |
506 | |
507 | /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */ |
508 | if (atomic_long_read(&sb->s_remove_count)) |
509 | return -EBUSY; |
510 | |
511 | br_write_lock(&vfsmount_lock); |
512 | list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { |
513 | if (!(mnt->mnt.mnt_flags & MNT_READONLY)) { |
514 | mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; |
515 | smp_mb(); |
516 | if (mnt_get_writers(mnt) > 0) { |
517 | err = -EBUSY; |
518 | break; |
519 | } |
520 | } |
521 | } |
522 | if (!err && atomic_long_read(&sb->s_remove_count)) |
523 | err = -EBUSY; |
524 | |
525 | if (!err) { |
526 | sb->s_readonly_remount = 1; |
527 | smp_wmb(); |
528 | } |
529 | list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { |
530 | if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD) |
531 | mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; |
532 | } |
533 | br_write_unlock(&vfsmount_lock); |
534 | |
535 | return err; |
536 | } |
537 | |
538 | static void free_vfsmnt(struct mount *mnt) |
539 | { |
540 | kfree(mnt->mnt_devname); |
541 | mnt_free_id(mnt); |
542 | #ifdef CONFIG_SMP |
543 | free_percpu(mnt->mnt_pcp); |
544 | #endif |
545 | kmem_cache_free(mnt_cache, mnt); |
546 | } |
547 | |
548 | /* |
549 | * find the first or last mount at @dentry on vfsmount @mnt depending on |
550 | * @dir. If @dir is set return the first mount else return the last mount. |
551 | * vfsmount_lock must be held for read or write. |
552 | */ |
553 | struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry, |
554 | int dir) |
555 | { |
556 | struct list_head *head = mount_hashtable + hash(mnt, dentry); |
557 | struct list_head *tmp = head; |
558 | struct mount *p, *found = NULL; |
559 | |
560 | for (;;) { |
561 | tmp = dir ? tmp->next : tmp->prev; |
562 | p = NULL; |
563 | if (tmp == head) |
564 | break; |
565 | p = list_entry(tmp, struct mount, mnt_hash); |
566 | if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) { |
567 | found = p; |
568 | break; |
569 | } |
570 | } |
571 | return found; |
572 | } |
573 | |
574 | /* |
575 | * lookup_mnt - Return the first child mount mounted at path |
576 | * |
577 | * "First" means first mounted chronologically. If you create the |
578 | * following mounts: |
579 | * |
580 | * mount /dev/sda1 /mnt |
581 | * mount /dev/sda2 /mnt |
582 | * mount /dev/sda3 /mnt |
583 | * |
584 | * Then lookup_mnt() on the base /mnt dentry in the root mount will |
585 | * return successively the root dentry and vfsmount of /dev/sda1, then |
586 | * /dev/sda2, then /dev/sda3, then NULL. |
587 | * |
588 | * lookup_mnt takes a reference to the found vfsmount. |
589 | */ |
590 | struct vfsmount *lookup_mnt(struct path *path) |
591 | { |
592 | struct mount *child_mnt; |
593 | |
594 | br_read_lock(&vfsmount_lock); |
595 | child_mnt = __lookup_mnt(path->mnt, path->dentry, 1); |
596 | if (child_mnt) { |
597 | mnt_add_count(child_mnt, 1); |
598 | br_read_unlock(&vfsmount_lock); |
599 | return &child_mnt->mnt; |
600 | } else { |
601 | br_read_unlock(&vfsmount_lock); |
602 | return NULL; |
603 | } |
604 | } |
605 | |
606 | static inline int check_mnt(struct mount *mnt) |
607 | { |
608 | return mnt->mnt_ns == current->nsproxy->mnt_ns; |
609 | } |
610 | |
611 | /* |
612 | * vfsmount lock must be held for write |
613 | */ |
614 | static void touch_mnt_namespace(struct mnt_namespace *ns) |
615 | { |
616 | if (ns) { |
617 | ns->event = ++event; |
618 | wake_up_interruptible(&ns->poll); |
619 | } |
620 | } |
621 | |
622 | /* |
623 | * vfsmount lock must be held for write |
624 | */ |
625 | static void __touch_mnt_namespace(struct mnt_namespace *ns) |
626 | { |
627 | if (ns && ns->event != event) { |
628 | ns->event = event; |
629 | wake_up_interruptible(&ns->poll); |
630 | } |
631 | } |
632 | |
633 | /* |
634 | * Clear dentry's mounted state if it has no remaining mounts. |
635 | * vfsmount_lock must be held for write. |
636 | */ |
637 | static void dentry_reset_mounted(struct dentry *dentry) |
638 | { |
639 | unsigned u; |
640 | |
641 | for (u = 0; u < HASH_SIZE; u++) { |
642 | struct mount *p; |
643 | |
644 | list_for_each_entry(p, &mount_hashtable[u], mnt_hash) { |
645 | if (p->mnt_mountpoint == dentry) |
646 | return; |
647 | } |
648 | } |
649 | spin_lock(&dentry->d_lock); |
650 | dentry->d_flags &= ~DCACHE_MOUNTED; |
651 | spin_unlock(&dentry->d_lock); |
652 | } |
653 | |
654 | /* |
655 | * vfsmount lock must be held for write |
656 | */ |
657 | static void detach_mnt(struct mount *mnt, struct path *old_path) |
658 | { |
659 | old_path->dentry = mnt->mnt_mountpoint; |
660 | old_path->mnt = &mnt->mnt_parent->mnt; |
661 | mnt->mnt_parent = mnt; |
662 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
663 | list_del_init(&mnt->mnt_child); |
664 | list_del_init(&mnt->mnt_hash); |
665 | dentry_reset_mounted(old_path->dentry); |
666 | } |
667 | |
668 | /* |
669 | * vfsmount lock must be held for write |
670 | */ |
671 | void mnt_set_mountpoint(struct mount *mnt, struct dentry *dentry, |
672 | struct mount *child_mnt) |
673 | { |
674 | mnt_add_count(mnt, 1); /* essentially, that's mntget */ |
675 | child_mnt->mnt_mountpoint = dget(dentry); |
676 | child_mnt->mnt_parent = mnt; |
677 | spin_lock(&dentry->d_lock); |
678 | dentry->d_flags |= DCACHE_MOUNTED; |
679 | spin_unlock(&dentry->d_lock); |
680 | } |
681 | |
682 | /* |
683 | * vfsmount lock must be held for write |
684 | */ |
685 | static void attach_mnt(struct mount *mnt, struct path *path) |
686 | { |
687 | mnt_set_mountpoint(real_mount(path->mnt), path->dentry, mnt); |
688 | list_add_tail(&mnt->mnt_hash, mount_hashtable + |
689 | hash(path->mnt, path->dentry)); |
690 | list_add_tail(&mnt->mnt_child, &real_mount(path->mnt)->mnt_mounts); |
691 | } |
692 | |
693 | /* |
694 | * vfsmount lock must be held for write |
695 | */ |
696 | static void commit_tree(struct mount *mnt) |
697 | { |
698 | struct mount *parent = mnt->mnt_parent; |
699 | struct mount *m; |
700 | LIST_HEAD(head); |
701 | struct mnt_namespace *n = parent->mnt_ns; |
702 | |
703 | BUG_ON(parent == mnt); |
704 | |
705 | list_add_tail(&head, &mnt->mnt_list); |
706 | list_for_each_entry(m, &head, mnt_list) |
707 | m->mnt_ns = n; |
708 | |
709 | list_splice(&head, n->list.prev); |
710 | |
711 | list_add_tail(&mnt->mnt_hash, mount_hashtable + |
712 | hash(&parent->mnt, mnt->mnt_mountpoint)); |
713 | list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); |
714 | touch_mnt_namespace(n); |
715 | } |
716 | |
717 | static struct mount *next_mnt(struct mount *p, struct mount *root) |
718 | { |
719 | struct list_head *next = p->mnt_mounts.next; |
720 | if (next == &p->mnt_mounts) { |
721 | while (1) { |
722 | if (p == root) |
723 | return NULL; |
724 | next = p->mnt_child.next; |
725 | if (next != &p->mnt_parent->mnt_mounts) |
726 | break; |
727 | p = p->mnt_parent; |
728 | } |
729 | } |
730 | return list_entry(next, struct mount, mnt_child); |
731 | } |
732 | |
733 | static struct mount *skip_mnt_tree(struct mount *p) |
734 | { |
735 | struct list_head *prev = p->mnt_mounts.prev; |
736 | while (prev != &p->mnt_mounts) { |
737 | p = list_entry(prev, struct mount, mnt_child); |
738 | prev = p->mnt_mounts.prev; |
739 | } |
740 | return p; |
741 | } |
742 | |
743 | struct vfsmount * |
744 | vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data) |
745 | { |
746 | struct mount *mnt; |
747 | struct dentry *root; |
748 | |
749 | if (!type) |
750 | return ERR_PTR(-ENODEV); |
751 | |
752 | mnt = alloc_vfsmnt(name); |
753 | if (!mnt) |
754 | return ERR_PTR(-ENOMEM); |
755 | |
756 | if (flags & MS_KERNMOUNT) |
757 | mnt->mnt.mnt_flags = MNT_INTERNAL; |
758 | |
759 | root = mount_fs(type, flags, name, data); |
760 | if (IS_ERR(root)) { |
761 | free_vfsmnt(mnt); |
762 | return ERR_CAST(root); |
763 | } |
764 | |
765 | mnt->mnt.mnt_root = root; |
766 | mnt->mnt.mnt_sb = root->d_sb; |
767 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
768 | mnt->mnt_parent = mnt; |
769 | br_write_lock(&vfsmount_lock); |
770 | list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts); |
771 | br_write_unlock(&vfsmount_lock); |
772 | return &mnt->mnt; |
773 | } |
774 | EXPORT_SYMBOL_GPL(vfs_kern_mount); |
775 | |
776 | static struct mount *clone_mnt(struct mount *old, struct dentry *root, |
777 | int flag) |
778 | { |
779 | struct super_block *sb = old->mnt.mnt_sb; |
780 | struct mount *mnt; |
781 | int err; |
782 | |
783 | mnt = alloc_vfsmnt(old->mnt_devname); |
784 | if (!mnt) |
785 | return ERR_PTR(-ENOMEM); |
786 | |
787 | if (flag & (CL_SLAVE | CL_PRIVATE)) |
788 | mnt->mnt_group_id = 0; /* not a peer of original */ |
789 | else |
790 | mnt->mnt_group_id = old->mnt_group_id; |
791 | |
792 | if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { |
793 | err = mnt_alloc_group_id(mnt); |
794 | if (err) |
795 | goto out_free; |
796 | } |
797 | |
798 | mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD; |
799 | atomic_inc(&sb->s_active); |
800 | mnt->mnt.mnt_sb = sb; |
801 | mnt->mnt.mnt_root = dget(root); |
802 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
803 | mnt->mnt_parent = mnt; |
804 | br_write_lock(&vfsmount_lock); |
805 | list_add_tail(&mnt->mnt_instance, &sb->s_mounts); |
806 | br_write_unlock(&vfsmount_lock); |
807 | |
808 | if (flag & CL_SLAVE) { |
809 | list_add(&mnt->mnt_slave, &old->mnt_slave_list); |
810 | mnt->mnt_master = old; |
811 | CLEAR_MNT_SHARED(mnt); |
812 | } else if (!(flag & CL_PRIVATE)) { |
813 | if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old)) |
814 | list_add(&mnt->mnt_share, &old->mnt_share); |
815 | if (IS_MNT_SLAVE(old)) |
816 | list_add(&mnt->mnt_slave, &old->mnt_slave); |
817 | mnt->mnt_master = old->mnt_master; |
818 | } |
819 | if (flag & CL_MAKE_SHARED) |
820 | set_mnt_shared(mnt); |
821 | |
822 | /* stick the duplicate mount on the same expiry list |
823 | * as the original if that was on one */ |
824 | if (flag & CL_EXPIRE) { |
825 | if (!list_empty(&old->mnt_expire)) |
826 | list_add(&mnt->mnt_expire, &old->mnt_expire); |
827 | } |
828 | |
829 | return mnt; |
830 | |
831 | out_free: |
832 | free_vfsmnt(mnt); |
833 | return ERR_PTR(err); |
834 | } |
835 | |
836 | static inline void mntfree(struct mount *mnt) |
837 | { |
838 | struct vfsmount *m = &mnt->mnt; |
839 | struct super_block *sb = m->mnt_sb; |
840 | |
841 | /* |
842 | * This probably indicates that somebody messed |
843 | * up a mnt_want/drop_write() pair. If this |
844 | * happens, the filesystem was probably unable |
845 | * to make r/w->r/o transitions. |
846 | */ |
847 | /* |
848 | * The locking used to deal with mnt_count decrement provides barriers, |
849 | * so mnt_get_writers() below is safe. |
850 | */ |
851 | WARN_ON(mnt_get_writers(mnt)); |
852 | fsnotify_vfsmount_delete(m); |
853 | dput(m->mnt_root); |
854 | free_vfsmnt(mnt); |
855 | deactivate_super(sb); |
856 | } |
857 | |
858 | static void mntput_no_expire(struct mount *mnt) |
859 | { |
860 | put_again: |
861 | #ifdef CONFIG_SMP |
862 | br_read_lock(&vfsmount_lock); |
863 | if (likely(mnt->mnt_ns)) { |
864 | /* shouldn't be the last one */ |
865 | mnt_add_count(mnt, -1); |
866 | br_read_unlock(&vfsmount_lock); |
867 | return; |
868 | } |
869 | br_read_unlock(&vfsmount_lock); |
870 | |
871 | br_write_lock(&vfsmount_lock); |
872 | mnt_add_count(mnt, -1); |
873 | if (mnt_get_count(mnt)) { |
874 | br_write_unlock(&vfsmount_lock); |
875 | return; |
876 | } |
877 | #else |
878 | mnt_add_count(mnt, -1); |
879 | if (likely(mnt_get_count(mnt))) |
880 | return; |
881 | br_write_lock(&vfsmount_lock); |
882 | #endif |
883 | if (unlikely(mnt->mnt_pinned)) { |
884 | mnt_add_count(mnt, mnt->mnt_pinned + 1); |
885 | mnt->mnt_pinned = 0; |
886 | br_write_unlock(&vfsmount_lock); |
887 | acct_auto_close_mnt(&mnt->mnt); |
888 | goto put_again; |
889 | } |
890 | |
891 | list_del(&mnt->mnt_instance); |
892 | br_write_unlock(&vfsmount_lock); |
893 | mntfree(mnt); |
894 | } |
895 | |
896 | void mntput(struct vfsmount *mnt) |
897 | { |
898 | if (mnt) { |
899 | struct mount *m = real_mount(mnt); |
900 | /* avoid cacheline pingpong, hope gcc doesn't get "smart" */ |
901 | if (unlikely(m->mnt_expiry_mark)) |
902 | m->mnt_expiry_mark = 0; |
903 | mntput_no_expire(m); |
904 | } |
905 | } |
906 | EXPORT_SYMBOL(mntput); |
907 | |
908 | struct vfsmount *mntget(struct vfsmount *mnt) |
909 | { |
910 | if (mnt) |
911 | mnt_add_count(real_mount(mnt), 1); |
912 | return mnt; |
913 | } |
914 | EXPORT_SYMBOL(mntget); |
915 | |
916 | void mnt_pin(struct vfsmount *mnt) |
917 | { |
918 | br_write_lock(&vfsmount_lock); |
919 | real_mount(mnt)->mnt_pinned++; |
920 | br_write_unlock(&vfsmount_lock); |
921 | } |
922 | EXPORT_SYMBOL(mnt_pin); |
923 | |
924 | void mnt_unpin(struct vfsmount *m) |
925 | { |
926 | struct mount *mnt = real_mount(m); |
927 | br_write_lock(&vfsmount_lock); |
928 | if (mnt->mnt_pinned) { |
929 | mnt_add_count(mnt, 1); |
930 | mnt->mnt_pinned--; |
931 | } |
932 | br_write_unlock(&vfsmount_lock); |
933 | } |
934 | EXPORT_SYMBOL(mnt_unpin); |
935 | |
936 | static inline void mangle(struct seq_file *m, const char *s) |
937 | { |
938 | seq_escape(m, s, " \t\n\\"); |
939 | } |
940 | |
941 | /* |
942 | * Simple .show_options callback for filesystems which don't want to |
943 | * implement more complex mount option showing. |
944 | * |
945 | * See also save_mount_options(). |
946 | */ |
947 | int generic_show_options(struct seq_file *m, struct dentry *root) |
948 | { |
949 | const char *options; |
950 | |
951 | rcu_read_lock(); |
952 | options = rcu_dereference(root->d_sb->s_options); |
953 | |
954 | if (options != NULL && options[0]) { |
955 | seq_putc(m, ','); |
956 | mangle(m, options); |
957 | } |
958 | rcu_read_unlock(); |
959 | |
960 | return 0; |
961 | } |
962 | EXPORT_SYMBOL(generic_show_options); |
963 | |
964 | /* |
965 | * If filesystem uses generic_show_options(), this function should be |
966 | * called from the fill_super() callback. |
967 | * |
968 | * The .remount_fs callback usually needs to be handled in a special |
969 | * way, to make sure, that previous options are not overwritten if the |
970 | * remount fails. |
971 | * |
972 | * Also note, that if the filesystem's .remount_fs function doesn't |
973 | * reset all options to their default value, but changes only newly |
974 | * given options, then the displayed options will not reflect reality |
975 | * any more. |
976 | */ |
977 | void save_mount_options(struct super_block *sb, char *options) |
978 | { |
979 | BUG_ON(sb->s_options); |
980 | rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL)); |
981 | } |
982 | EXPORT_SYMBOL(save_mount_options); |
983 | |
984 | void replace_mount_options(struct super_block *sb, char *options) |
985 | { |
986 | char *old = sb->s_options; |
987 | rcu_assign_pointer(sb->s_options, options); |
988 | if (old) { |
989 | synchronize_rcu(); |
990 | kfree(old); |
991 | } |
992 | } |
993 | EXPORT_SYMBOL(replace_mount_options); |
994 | |
995 | #ifdef CONFIG_PROC_FS |
996 | /* iterator; we want it to have access to namespace_sem, thus here... */ |
997 | static void *m_start(struct seq_file *m, loff_t *pos) |
998 | { |
999 | struct proc_mounts *p = proc_mounts(m); |
1000 | |
1001 | down_read(&namespace_sem); |
1002 | return seq_list_start(&p->ns->list, *pos); |
1003 | } |
1004 | |
1005 | static void *m_next(struct seq_file *m, void *v, loff_t *pos) |
1006 | { |
1007 | struct proc_mounts *p = proc_mounts(m); |
1008 | |
1009 | return seq_list_next(v, &p->ns->list, pos); |
1010 | } |
1011 | |
1012 | static void m_stop(struct seq_file *m, void *v) |
1013 | { |
1014 | up_read(&namespace_sem); |
1015 | } |
1016 | |
1017 | static int m_show(struct seq_file *m, void *v) |
1018 | { |
1019 | struct proc_mounts *p = proc_mounts(m); |
1020 | struct mount *r = list_entry(v, struct mount, mnt_list); |
1021 | return p->show(m, &r->mnt); |
1022 | } |
1023 | |
1024 | const struct seq_operations mounts_op = { |
1025 | .start = m_start, |
1026 | .next = m_next, |
1027 | .stop = m_stop, |
1028 | .show = m_show, |
1029 | }; |
1030 | #endif /* CONFIG_PROC_FS */ |
1031 | |
1032 | /** |
1033 | * may_umount_tree - check if a mount tree is busy |
1034 | * @mnt: root of mount tree |
1035 | * |
1036 | * This is called to check if a tree of mounts has any |
1037 | * open files, pwds, chroots or sub mounts that are |
1038 | * busy. |
1039 | */ |
1040 | int may_umount_tree(struct vfsmount *m) |
1041 | { |
1042 | struct mount *mnt = real_mount(m); |
1043 | int actual_refs = 0; |
1044 | int minimum_refs = 0; |
1045 | struct mount *p; |
1046 | BUG_ON(!m); |
1047 | |
1048 | /* write lock needed for mnt_get_count */ |
1049 | br_write_lock(&vfsmount_lock); |
1050 | for (p = mnt; p; p = next_mnt(p, mnt)) { |
1051 | actual_refs += mnt_get_count(p); |
1052 | minimum_refs += 2; |
1053 | } |
1054 | br_write_unlock(&vfsmount_lock); |
1055 | |
1056 | if (actual_refs > minimum_refs) |
1057 | return 0; |
1058 | |
1059 | return 1; |
1060 | } |
1061 | |
1062 | EXPORT_SYMBOL(may_umount_tree); |
1063 | |
1064 | /** |
1065 | * may_umount - check if a mount point is busy |
1066 | * @mnt: root of mount |
1067 | * |
1068 | * This is called to check if a mount point has any |
1069 | * open files, pwds, chroots or sub mounts. If the |
1070 | * mount has sub mounts this will return busy |
1071 | * regardless of whether the sub mounts are busy. |
1072 | * |
1073 | * Doesn't take quota and stuff into account. IOW, in some cases it will |
1074 | * give false negatives. The main reason why it's here is that we need |
1075 | * a non-destructive way to look for easily umountable filesystems. |
1076 | */ |
1077 | int may_umount(struct vfsmount *mnt) |
1078 | { |
1079 | int ret = 1; |
1080 | down_read(&namespace_sem); |
1081 | br_write_lock(&vfsmount_lock); |
1082 | if (propagate_mount_busy(real_mount(mnt), 2)) |
1083 | ret = 0; |
1084 | br_write_unlock(&vfsmount_lock); |
1085 | up_read(&namespace_sem); |
1086 | return ret; |
1087 | } |
1088 | |
1089 | EXPORT_SYMBOL(may_umount); |
1090 | |
1091 | void release_mounts(struct list_head *head) |
1092 | { |
1093 | struct mount *mnt; |
1094 | while (!list_empty(head)) { |
1095 | mnt = list_first_entry(head, struct mount, mnt_hash); |
1096 | list_del_init(&mnt->mnt_hash); |
1097 | if (mnt_has_parent(mnt)) { |
1098 | struct dentry *dentry; |
1099 | struct mount *m; |
1100 | |
1101 | br_write_lock(&vfsmount_lock); |
1102 | dentry = mnt->mnt_mountpoint; |
1103 | m = mnt->mnt_parent; |
1104 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
1105 | mnt->mnt_parent = mnt; |
1106 | m->mnt_ghosts--; |
1107 | br_write_unlock(&vfsmount_lock); |
1108 | dput(dentry); |
1109 | mntput(&m->mnt); |
1110 | } |
1111 | mntput(&mnt->mnt); |
1112 | } |
1113 | } |
1114 | |
1115 | /* |
1116 | * vfsmount lock must be held for write |
1117 | * namespace_sem must be held for write |
1118 | */ |
1119 | void umount_tree(struct mount *mnt, int propagate, struct list_head *kill) |
1120 | { |
1121 | LIST_HEAD(tmp_list); |
1122 | struct mount *p; |
1123 | |
1124 | for (p = mnt; p; p = next_mnt(p, mnt)) |
1125 | list_move(&p->mnt_hash, &tmp_list); |
1126 | |
1127 | if (propagate) |
1128 | propagate_umount(&tmp_list); |
1129 | |
1130 | list_for_each_entry(p, &tmp_list, mnt_hash) { |
1131 | list_del_init(&p->mnt_expire); |
1132 | list_del_init(&p->mnt_list); |
1133 | __touch_mnt_namespace(p->mnt_ns); |
1134 | p->mnt_ns = NULL; |
1135 | list_del_init(&p->mnt_child); |
1136 | if (mnt_has_parent(p)) { |
1137 | p->mnt_parent->mnt_ghosts++; |
1138 | dentry_reset_mounted(p->mnt_mountpoint); |
1139 | } |
1140 | change_mnt_propagation(p, MS_PRIVATE); |
1141 | } |
1142 | list_splice(&tmp_list, kill); |
1143 | } |
1144 | |
1145 | static void shrink_submounts(struct mount *mnt, struct list_head *umounts); |
1146 | |
1147 | static int do_umount(struct mount *mnt, int flags) |
1148 | { |
1149 | struct super_block *sb = mnt->mnt.mnt_sb; |
1150 | int retval; |
1151 | LIST_HEAD(umount_list); |
1152 | |
1153 | retval = security_sb_umount(&mnt->mnt, flags); |
1154 | if (retval) |
1155 | return retval; |
1156 | |
1157 | /* |
1158 | * Allow userspace to request a mountpoint be expired rather than |
1159 | * unmounting unconditionally. Unmount only happens if: |
1160 | * (1) the mark is already set (the mark is cleared by mntput()) |
1161 | * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] |
1162 | */ |
1163 | if (flags & MNT_EXPIRE) { |
1164 | if (&mnt->mnt == current->fs->root.mnt || |
1165 | flags & (MNT_FORCE | MNT_DETACH)) |
1166 | return -EINVAL; |
1167 | |
1168 | /* |
1169 | * probably don't strictly need the lock here if we examined |
1170 | * all race cases, but it's a slowpath. |
1171 | */ |
1172 | br_write_lock(&vfsmount_lock); |
1173 | if (mnt_get_count(mnt) != 2) { |
1174 | br_write_unlock(&vfsmount_lock); |
1175 | return -EBUSY; |
1176 | } |
1177 | br_write_unlock(&vfsmount_lock); |
1178 | |
1179 | if (!xchg(&mnt->mnt_expiry_mark, 1)) |
1180 | return -EAGAIN; |
1181 | } |
1182 | |
1183 | /* |
1184 | * If we may have to abort operations to get out of this |
1185 | * mount, and they will themselves hold resources we must |
1186 | * allow the fs to do things. In the Unix tradition of |
1187 | * 'Gee thats tricky lets do it in userspace' the umount_begin |
1188 | * might fail to complete on the first run through as other tasks |
1189 | * must return, and the like. Thats for the mount program to worry |
1190 | * about for the moment. |
1191 | */ |
1192 | |
1193 | if (flags & MNT_FORCE && sb->s_op->umount_begin) { |
1194 | sb->s_op->umount_begin(sb); |
1195 | } |
1196 | |
1197 | /* |
1198 | * No sense to grab the lock for this test, but test itself looks |
1199 | * somewhat bogus. Suggestions for better replacement? |
1200 | * Ho-hum... In principle, we might treat that as umount + switch |
1201 | * to rootfs. GC would eventually take care of the old vfsmount. |
1202 | * Actually it makes sense, especially if rootfs would contain a |
1203 | * /reboot - static binary that would close all descriptors and |
1204 | * call reboot(9). Then init(8) could umount root and exec /reboot. |
1205 | */ |
1206 | if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { |
1207 | /* |
1208 | * Special case for "unmounting" root ... |
1209 | * we just try to remount it readonly. |
1210 | */ |
1211 | down_write(&sb->s_umount); |
1212 | if (!(sb->s_flags & MS_RDONLY)) |
1213 | retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); |
1214 | up_write(&sb->s_umount); |
1215 | return retval; |
1216 | } |
1217 | |
1218 | down_write(&namespace_sem); |
1219 | br_write_lock(&vfsmount_lock); |
1220 | event++; |
1221 | |
1222 | if (!(flags & MNT_DETACH)) |
1223 | shrink_submounts(mnt, &umount_list); |
1224 | |
1225 | retval = -EBUSY; |
1226 | if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) { |
1227 | if (!list_empty(&mnt->mnt_list)) |
1228 | umount_tree(mnt, 1, &umount_list); |
1229 | retval = 0; |
1230 | } |
1231 | br_write_unlock(&vfsmount_lock); |
1232 | up_write(&namespace_sem); |
1233 | release_mounts(&umount_list); |
1234 | return retval; |
1235 | } |
1236 | |
1237 | /* |
1238 | * Now umount can handle mount points as well as block devices. |
1239 | * This is important for filesystems which use unnamed block devices. |
1240 | * |
1241 | * We now support a flag for forced unmount like the other 'big iron' |
1242 | * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD |
1243 | */ |
1244 | |
1245 | SYSCALL_DEFINE2(umount, char __user *, name, int, flags) |
1246 | { |
1247 | struct path path; |
1248 | struct mount *mnt; |
1249 | int retval; |
1250 | int lookup_flags = 0; |
1251 | |
1252 | if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) |
1253 | return -EINVAL; |
1254 | |
1255 | if (!(flags & UMOUNT_NOFOLLOW)) |
1256 | lookup_flags |= LOOKUP_FOLLOW; |
1257 | |
1258 | retval = user_path_at(AT_FDCWD, name, lookup_flags, &path); |
1259 | if (retval) |
1260 | goto out; |
1261 | mnt = real_mount(path.mnt); |
1262 | retval = -EINVAL; |
1263 | if (path.dentry != path.mnt->mnt_root) |
1264 | goto dput_and_out; |
1265 | if (!check_mnt(mnt)) |
1266 | goto dput_and_out; |
1267 | |
1268 | retval = -EPERM; |
1269 | if (!capable(CAP_SYS_ADMIN)) |
1270 | goto dput_and_out; |
1271 | |
1272 | retval = do_umount(mnt, flags); |
1273 | dput_and_out: |
1274 | /* we mustn't call path_put() as that would clear mnt_expiry_mark */ |
1275 | dput(path.dentry); |
1276 | mntput_no_expire(mnt); |
1277 | out: |
1278 | return retval; |
1279 | } |
1280 | |
1281 | #ifdef __ARCH_WANT_SYS_OLDUMOUNT |
1282 | |
1283 | /* |
1284 | * The 2.0 compatible umount. No flags. |
1285 | */ |
1286 | SYSCALL_DEFINE1(oldumount, char __user *, name) |
1287 | { |
1288 | return sys_umount(name, 0); |
1289 | } |
1290 | |
1291 | #endif |
1292 | |
1293 | static int mount_is_safe(struct path *path) |
1294 | { |
1295 | if (capable(CAP_SYS_ADMIN)) |
1296 | return 0; |
1297 | return -EPERM; |
1298 | #ifdef notyet |
1299 | if (S_ISLNK(path->dentry->d_inode->i_mode)) |
1300 | return -EPERM; |
1301 | if (path->dentry->d_inode->i_mode & S_ISVTX) { |
1302 | if (current_uid() != path->dentry->d_inode->i_uid) |
1303 | return -EPERM; |
1304 | } |
1305 | if (inode_permission(path->dentry->d_inode, MAY_WRITE)) |
1306 | return -EPERM; |
1307 | return 0; |
1308 | #endif |
1309 | } |
1310 | |
1311 | struct mount *copy_tree(struct mount *mnt, struct dentry *dentry, |
1312 | int flag) |
1313 | { |
1314 | struct mount *res, *p, *q, *r; |
1315 | struct path path; |
1316 | |
1317 | if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt)) |
1318 | return ERR_PTR(-EINVAL); |
1319 | |
1320 | res = q = clone_mnt(mnt, dentry, flag); |
1321 | if (IS_ERR(q)) |
1322 | return q; |
1323 | |
1324 | q->mnt_mountpoint = mnt->mnt_mountpoint; |
1325 | |
1326 | p = mnt; |
1327 | list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { |
1328 | struct mount *s; |
1329 | if (!is_subdir(r->mnt_mountpoint, dentry)) |
1330 | continue; |
1331 | |
1332 | for (s = r; s; s = next_mnt(s, r)) { |
1333 | if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) { |
1334 | s = skip_mnt_tree(s); |
1335 | continue; |
1336 | } |
1337 | while (p != s->mnt_parent) { |
1338 | p = p->mnt_parent; |
1339 | q = q->mnt_parent; |
1340 | } |
1341 | p = s; |
1342 | path.mnt = &q->mnt; |
1343 | path.dentry = p->mnt_mountpoint; |
1344 | q = clone_mnt(p, p->mnt.mnt_root, flag); |
1345 | if (IS_ERR(q)) |
1346 | goto out; |
1347 | br_write_lock(&vfsmount_lock); |
1348 | list_add_tail(&q->mnt_list, &res->mnt_list); |
1349 | attach_mnt(q, &path); |
1350 | br_write_unlock(&vfsmount_lock); |
1351 | } |
1352 | } |
1353 | return res; |
1354 | out: |
1355 | if (res) { |
1356 | LIST_HEAD(umount_list); |
1357 | br_write_lock(&vfsmount_lock); |
1358 | umount_tree(res, 0, &umount_list); |
1359 | br_write_unlock(&vfsmount_lock); |
1360 | release_mounts(&umount_list); |
1361 | } |
1362 | return q; |
1363 | } |
1364 | |
1365 | /* Caller should check returned pointer for errors */ |
1366 | |
1367 | struct vfsmount *collect_mounts(struct path *path) |
1368 | { |
1369 | struct mount *tree; |
1370 | down_write(&namespace_sem); |
1371 | tree = copy_tree(real_mount(path->mnt), path->dentry, |
1372 | CL_COPY_ALL | CL_PRIVATE); |
1373 | up_write(&namespace_sem); |
1374 | if (IS_ERR(tree)) |
1375 | return NULL; |
1376 | return &tree->mnt; |
1377 | } |
1378 | |
1379 | void drop_collected_mounts(struct vfsmount *mnt) |
1380 | { |
1381 | LIST_HEAD(umount_list); |
1382 | down_write(&namespace_sem); |
1383 | br_write_lock(&vfsmount_lock); |
1384 | umount_tree(real_mount(mnt), 0, &umount_list); |
1385 | br_write_unlock(&vfsmount_lock); |
1386 | up_write(&namespace_sem); |
1387 | release_mounts(&umount_list); |
1388 | } |
1389 | |
1390 | int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, |
1391 | struct vfsmount *root) |
1392 | { |
1393 | struct mount *mnt; |
1394 | int res = f(root, arg); |
1395 | if (res) |
1396 | return res; |
1397 | list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) { |
1398 | res = f(&mnt->mnt, arg); |
1399 | if (res) |
1400 | return res; |
1401 | } |
1402 | return 0; |
1403 | } |
1404 | |
1405 | static void cleanup_group_ids(struct mount *mnt, struct mount *end) |
1406 | { |
1407 | struct mount *p; |
1408 | |
1409 | for (p = mnt; p != end; p = next_mnt(p, mnt)) { |
1410 | if (p->mnt_group_id && !IS_MNT_SHARED(p)) |
1411 | mnt_release_group_id(p); |
1412 | } |
1413 | } |
1414 | |
1415 | static int invent_group_ids(struct mount *mnt, bool recurse) |
1416 | { |
1417 | struct mount *p; |
1418 | |
1419 | for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { |
1420 | if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { |
1421 | int err = mnt_alloc_group_id(p); |
1422 | if (err) { |
1423 | cleanup_group_ids(mnt, p); |
1424 | return err; |
1425 | } |
1426 | } |
1427 | } |
1428 | |
1429 | return 0; |
1430 | } |
1431 | |
1432 | /* |
1433 | * @source_mnt : mount tree to be attached |
1434 | * @nd : place the mount tree @source_mnt is attached |
1435 | * @parent_nd : if non-null, detach the source_mnt from its parent and |
1436 | * store the parent mount and mountpoint dentry. |
1437 | * (done when source_mnt is moved) |
1438 | * |
1439 | * NOTE: in the table below explains the semantics when a source mount |
1440 | * of a given type is attached to a destination mount of a given type. |
1441 | * --------------------------------------------------------------------------- |
1442 | * | BIND MOUNT OPERATION | |
1443 | * |************************************************************************** |
1444 | * | source-->| shared | private | slave | unbindable | |
1445 | * | dest | | | | | |
1446 | * | | | | | | | |
1447 | * | v | | | | | |
1448 | * |************************************************************************** |
1449 | * | shared | shared (++) | shared (+) | shared(+++)| invalid | |
1450 | * | | | | | | |
1451 | * |non-shared| shared (+) | private | slave (*) | invalid | |
1452 | * *************************************************************************** |
1453 | * A bind operation clones the source mount and mounts the clone on the |
1454 | * destination mount. |
1455 | * |
1456 | * (++) the cloned mount is propagated to all the mounts in the propagation |
1457 | * tree of the destination mount and the cloned mount is added to |
1458 | * the peer group of the source mount. |
1459 | * (+) the cloned mount is created under the destination mount and is marked |
1460 | * as shared. The cloned mount is added to the peer group of the source |
1461 | * mount. |
1462 | * (+++) the mount is propagated to all the mounts in the propagation tree |
1463 | * of the destination mount and the cloned mount is made slave |
1464 | * of the same master as that of the source mount. The cloned mount |
1465 | * is marked as 'shared and slave'. |
1466 | * (*) the cloned mount is made a slave of the same master as that of the |
1467 | * source mount. |
1468 | * |
1469 | * --------------------------------------------------------------------------- |
1470 | * | MOVE MOUNT OPERATION | |
1471 | * |************************************************************************** |
1472 | * | source-->| shared | private | slave | unbindable | |
1473 | * | dest | | | | | |
1474 | * | | | | | | | |
1475 | * | v | | | | | |
1476 | * |************************************************************************** |
1477 | * | shared | shared (+) | shared (+) | shared(+++) | invalid | |
1478 | * | | | | | | |
1479 | * |non-shared| shared (+*) | private | slave (*) | unbindable | |
1480 | * *************************************************************************** |
1481 | * |
1482 | * (+) the mount is moved to the destination. And is then propagated to |
1483 | * all the mounts in the propagation tree of the destination mount. |
1484 | * (+*) the mount is moved to the destination. |
1485 | * (+++) the mount is moved to the destination and is then propagated to |
1486 | * all the mounts belonging to the destination mount's propagation tree. |
1487 | * the mount is marked as 'shared and slave'. |
1488 | * (*) the mount continues to be a slave at the new location. |
1489 | * |
1490 | * if the source mount is a tree, the operations explained above is |
1491 | * applied to each mount in the tree. |
1492 | * Must be called without spinlocks held, since this function can sleep |
1493 | * in allocations. |
1494 | */ |
1495 | static int attach_recursive_mnt(struct mount *source_mnt, |
1496 | struct path *path, struct path *parent_path) |
1497 | { |
1498 | LIST_HEAD(tree_list); |
1499 | struct mount *dest_mnt = real_mount(path->mnt); |
1500 | struct dentry *dest_dentry = path->dentry; |
1501 | struct mount *child, *p; |
1502 | int err; |
1503 | |
1504 | if (IS_MNT_SHARED(dest_mnt)) { |
1505 | err = invent_group_ids(source_mnt, true); |
1506 | if (err) |
1507 | goto out; |
1508 | } |
1509 | err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list); |
1510 | if (err) |
1511 | goto out_cleanup_ids; |
1512 | |
1513 | br_write_lock(&vfsmount_lock); |
1514 | |
1515 | if (IS_MNT_SHARED(dest_mnt)) { |
1516 | for (p = source_mnt; p; p = next_mnt(p, source_mnt)) |
1517 | set_mnt_shared(p); |
1518 | } |
1519 | if (parent_path) { |
1520 | detach_mnt(source_mnt, parent_path); |
1521 | attach_mnt(source_mnt, path); |
1522 | touch_mnt_namespace(source_mnt->mnt_ns); |
1523 | } else { |
1524 | mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt); |
1525 | commit_tree(source_mnt); |
1526 | } |
1527 | |
1528 | list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { |
1529 | list_del_init(&child->mnt_hash); |
1530 | commit_tree(child); |
1531 | } |
1532 | br_write_unlock(&vfsmount_lock); |
1533 | |
1534 | return 0; |
1535 | |
1536 | out_cleanup_ids: |
1537 | if (IS_MNT_SHARED(dest_mnt)) |
1538 | cleanup_group_ids(source_mnt, NULL); |
1539 | out: |
1540 | return err; |
1541 | } |
1542 | |
1543 | static int lock_mount(struct path *path) |
1544 | { |
1545 | struct vfsmount *mnt; |
1546 | retry: |
1547 | mutex_lock(&path->dentry->d_inode->i_mutex); |
1548 | if (unlikely(cant_mount(path->dentry))) { |
1549 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
1550 | return -ENOENT; |
1551 | } |
1552 | down_write(&namespace_sem); |
1553 | mnt = lookup_mnt(path); |
1554 | if (likely(!mnt)) |
1555 | return 0; |
1556 | up_write(&namespace_sem); |
1557 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
1558 | path_put(path); |
1559 | path->mnt = mnt; |
1560 | path->dentry = dget(mnt->mnt_root); |
1561 | goto retry; |
1562 | } |
1563 | |
1564 | static void unlock_mount(struct path *path) |
1565 | { |
1566 | up_write(&namespace_sem); |
1567 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
1568 | } |
1569 | |
1570 | static int graft_tree(struct mount *mnt, struct path *path) |
1571 | { |
1572 | if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER) |
1573 | return -EINVAL; |
1574 | |
1575 | if (S_ISDIR(path->dentry->d_inode->i_mode) != |
1576 | S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode)) |
1577 | return -ENOTDIR; |
1578 | |
1579 | if (d_unlinked(path->dentry)) |
1580 | return -ENOENT; |
1581 | |
1582 | return attach_recursive_mnt(mnt, path, NULL); |
1583 | } |
1584 | |
1585 | /* |
1586 | * Sanity check the flags to change_mnt_propagation. |
1587 | */ |
1588 | |
1589 | static int flags_to_propagation_type(int flags) |
1590 | { |
1591 | int type = flags & ~(MS_REC | MS_SILENT); |
1592 | |
1593 | /* Fail if any non-propagation flags are set */ |
1594 | if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
1595 | return 0; |
1596 | /* Only one propagation flag should be set */ |
1597 | if (!is_power_of_2(type)) |
1598 | return 0; |
1599 | return type; |
1600 | } |
1601 | |
1602 | /* |
1603 | * recursively change the type of the mountpoint. |
1604 | */ |
1605 | static int do_change_type(struct path *path, int flag) |
1606 | { |
1607 | struct mount *m; |
1608 | struct mount *mnt = real_mount(path->mnt); |
1609 | int recurse = flag & MS_REC; |
1610 | int type; |
1611 | int err = 0; |
1612 | |
1613 | if (!capable(CAP_SYS_ADMIN)) |
1614 | return -EPERM; |
1615 | |
1616 | if (path->dentry != path->mnt->mnt_root) |
1617 | return -EINVAL; |
1618 | |
1619 | type = flags_to_propagation_type(flag); |
1620 | if (!type) |
1621 | return -EINVAL; |
1622 | |
1623 | down_write(&namespace_sem); |
1624 | if (type == MS_SHARED) { |
1625 | err = invent_group_ids(mnt, recurse); |
1626 | if (err) |
1627 | goto out_unlock; |
1628 | } |
1629 | |
1630 | br_write_lock(&vfsmount_lock); |
1631 | for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) |
1632 | change_mnt_propagation(m, type); |
1633 | br_write_unlock(&vfsmount_lock); |
1634 | |
1635 | out_unlock: |
1636 | up_write(&namespace_sem); |
1637 | return err; |
1638 | } |
1639 | |
1640 | /* |
1641 | * do loopback mount. |
1642 | */ |
1643 | static int do_loopback(struct path *path, char *old_name, |
1644 | int recurse) |
1645 | { |
1646 | LIST_HEAD(umount_list); |
1647 | struct path old_path; |
1648 | struct mount *mnt = NULL, *old; |
1649 | int err = mount_is_safe(path); |
1650 | if (err) |
1651 | return err; |
1652 | if (!old_name || !*old_name) |
1653 | return -EINVAL; |
1654 | err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); |
1655 | if (err) |
1656 | return err; |
1657 | |
1658 | err = lock_mount(path); |
1659 | if (err) |
1660 | goto out; |
1661 | |
1662 | old = real_mount(old_path.mnt); |
1663 | |
1664 | err = -EINVAL; |
1665 | if (IS_MNT_UNBINDABLE(old)) |
1666 | goto out2; |
1667 | |
1668 | if (!check_mnt(real_mount(path->mnt)) || !check_mnt(old)) |
1669 | goto out2; |
1670 | |
1671 | if (recurse) |
1672 | mnt = copy_tree(old, old_path.dentry, 0); |
1673 | else |
1674 | mnt = clone_mnt(old, old_path.dentry, 0); |
1675 | |
1676 | if (IS_ERR(mnt)) { |
1677 | err = PTR_ERR(mnt); |
1678 | goto out; |
1679 | } |
1680 | |
1681 | err = graft_tree(mnt, path); |
1682 | if (err) { |
1683 | br_write_lock(&vfsmount_lock); |
1684 | umount_tree(mnt, 0, &umount_list); |
1685 | br_write_unlock(&vfsmount_lock); |
1686 | } |
1687 | out2: |
1688 | unlock_mount(path); |
1689 | release_mounts(&umount_list); |
1690 | out: |
1691 | path_put(&old_path); |
1692 | return err; |
1693 | } |
1694 | |
1695 | static int change_mount_flags(struct vfsmount *mnt, int ms_flags) |
1696 | { |
1697 | int error = 0; |
1698 | int readonly_request = 0; |
1699 | |
1700 | if (ms_flags & MS_RDONLY) |
1701 | readonly_request = 1; |
1702 | if (readonly_request == __mnt_is_readonly(mnt)) |
1703 | return 0; |
1704 | |
1705 | if (readonly_request) |
1706 | error = mnt_make_readonly(real_mount(mnt)); |
1707 | else |
1708 | __mnt_unmake_readonly(real_mount(mnt)); |
1709 | return error; |
1710 | } |
1711 | |
1712 | /* |
1713 | * change filesystem flags. dir should be a physical root of filesystem. |
1714 | * If you've mounted a non-root directory somewhere and want to do remount |
1715 | * on it - tough luck. |
1716 | */ |
1717 | static int do_remount(struct path *path, int flags, int mnt_flags, |
1718 | void *data) |
1719 | { |
1720 | int err; |
1721 | struct super_block *sb = path->mnt->mnt_sb; |
1722 | struct mount *mnt = real_mount(path->mnt); |
1723 | |
1724 | if (!capable(CAP_SYS_ADMIN)) |
1725 | return -EPERM; |
1726 | |
1727 | if (!check_mnt(mnt)) |
1728 | return -EINVAL; |
1729 | |
1730 | if (path->dentry != path->mnt->mnt_root) |
1731 | return -EINVAL; |
1732 | |
1733 | err = security_sb_remount(sb, data); |
1734 | if (err) |
1735 | return err; |
1736 | |
1737 | down_write(&sb->s_umount); |
1738 | if (flags & MS_BIND) |
1739 | err = change_mount_flags(path->mnt, flags); |
1740 | else |
1741 | err = do_remount_sb(sb, flags, data, 0); |
1742 | if (!err) { |
1743 | br_write_lock(&vfsmount_lock); |
1744 | mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK; |
1745 | mnt->mnt.mnt_flags = mnt_flags; |
1746 | br_write_unlock(&vfsmount_lock); |
1747 | } |
1748 | up_write(&sb->s_umount); |
1749 | if (!err) { |
1750 | br_write_lock(&vfsmount_lock); |
1751 | touch_mnt_namespace(mnt->mnt_ns); |
1752 | br_write_unlock(&vfsmount_lock); |
1753 | } |
1754 | return err; |
1755 | } |
1756 | |
1757 | static inline int tree_contains_unbindable(struct mount *mnt) |
1758 | { |
1759 | struct mount *p; |
1760 | for (p = mnt; p; p = next_mnt(p, mnt)) { |
1761 | if (IS_MNT_UNBINDABLE(p)) |
1762 | return 1; |
1763 | } |
1764 | return 0; |
1765 | } |
1766 | |
1767 | static int do_move_mount(struct path *path, char *old_name) |
1768 | { |
1769 | struct path old_path, parent_path; |
1770 | struct mount *p; |
1771 | struct mount *old; |
1772 | int err = 0; |
1773 | if (!capable(CAP_SYS_ADMIN)) |
1774 | return -EPERM; |
1775 | if (!old_name || !*old_name) |
1776 | return -EINVAL; |
1777 | err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); |
1778 | if (err) |
1779 | return err; |
1780 | |
1781 | err = lock_mount(path); |
1782 | if (err < 0) |
1783 | goto out; |
1784 | |
1785 | old = real_mount(old_path.mnt); |
1786 | p = real_mount(path->mnt); |
1787 | |
1788 | err = -EINVAL; |
1789 | if (!check_mnt(p) || !check_mnt(old)) |
1790 | goto out1; |
1791 | |
1792 | if (d_unlinked(path->dentry)) |
1793 | goto out1; |
1794 | |
1795 | err = -EINVAL; |
1796 | if (old_path.dentry != old_path.mnt->mnt_root) |
1797 | goto out1; |
1798 | |
1799 | if (!mnt_has_parent(old)) |
1800 | goto out1; |
1801 | |
1802 | if (S_ISDIR(path->dentry->d_inode->i_mode) != |
1803 | S_ISDIR(old_path.dentry->d_inode->i_mode)) |
1804 | goto out1; |
1805 | /* |
1806 | * Don't move a mount residing in a shared parent. |
1807 | */ |
1808 | if (IS_MNT_SHARED(old->mnt_parent)) |
1809 | goto out1; |
1810 | /* |
1811 | * Don't move a mount tree containing unbindable mounts to a destination |
1812 | * mount which is shared. |
1813 | */ |
1814 | if (IS_MNT_SHARED(p) && tree_contains_unbindable(old)) |
1815 | goto out1; |
1816 | err = -ELOOP; |
1817 | for (; mnt_has_parent(p); p = p->mnt_parent) |
1818 | if (p == old) |
1819 | goto out1; |
1820 | |
1821 | err = attach_recursive_mnt(old, path, &parent_path); |
1822 | if (err) |
1823 | goto out1; |
1824 | |
1825 | /* if the mount is moved, it should no longer be expire |
1826 | * automatically */ |
1827 | list_del_init(&old->mnt_expire); |
1828 | out1: |
1829 | unlock_mount(path); |
1830 | out: |
1831 | if (!err) |
1832 | path_put(&parent_path); |
1833 | path_put(&old_path); |
1834 | return err; |
1835 | } |
1836 | |
1837 | static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype) |
1838 | { |
1839 | int err; |
1840 | const char *subtype = strchr(fstype, '.'); |
1841 | if (subtype) { |
1842 | subtype++; |
1843 | err = -EINVAL; |
1844 | if (!subtype[0]) |
1845 | goto err; |
1846 | } else |
1847 | subtype = ""; |
1848 | |
1849 | mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL); |
1850 | err = -ENOMEM; |
1851 | if (!mnt->mnt_sb->s_subtype) |
1852 | goto err; |
1853 | return mnt; |
1854 | |
1855 | err: |
1856 | mntput(mnt); |
1857 | return ERR_PTR(err); |
1858 | } |
1859 | |
1860 | static struct vfsmount * |
1861 | do_kern_mount(const char *fstype, int flags, const char *name, void *data) |
1862 | { |
1863 | struct file_system_type *type = get_fs_type(fstype); |
1864 | struct vfsmount *mnt; |
1865 | if (!type) |
1866 | return ERR_PTR(-ENODEV); |
1867 | mnt = vfs_kern_mount(type, flags, name, data); |
1868 | if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && |
1869 | !mnt->mnt_sb->s_subtype) |
1870 | mnt = fs_set_subtype(mnt, fstype); |
1871 | put_filesystem(type); |
1872 | return mnt; |
1873 | } |
1874 | |
1875 | /* |
1876 | * add a mount into a namespace's mount tree |
1877 | */ |
1878 | static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags) |
1879 | { |
1880 | int err; |
1881 | |
1882 | mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL); |
1883 | |
1884 | err = lock_mount(path); |
1885 | if (err) |
1886 | return err; |
1887 | |
1888 | err = -EINVAL; |
1889 | if (unlikely(!check_mnt(real_mount(path->mnt)))) { |
1890 | /* that's acceptable only for automounts done in private ns */ |
1891 | if (!(mnt_flags & MNT_SHRINKABLE)) |
1892 | goto unlock; |
1893 | /* ... and for those we'd better have mountpoint still alive */ |
1894 | if (!real_mount(path->mnt)->mnt_ns) |
1895 | goto unlock; |
1896 | } |
1897 | |
1898 | /* Refuse the same filesystem on the same mount point */ |
1899 | err = -EBUSY; |
1900 | if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && |
1901 | path->mnt->mnt_root == path->dentry) |
1902 | goto unlock; |
1903 | |
1904 | err = -EINVAL; |
1905 | if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode)) |
1906 | goto unlock; |
1907 | |
1908 | newmnt->mnt.mnt_flags = mnt_flags; |
1909 | err = graft_tree(newmnt, path); |
1910 | |
1911 | unlock: |
1912 | unlock_mount(path); |
1913 | return err; |
1914 | } |
1915 | |
1916 | /* |
1917 | * create a new mount for userspace and request it to be added into the |
1918 | * namespace's tree |
1919 | */ |
1920 | static int do_new_mount(struct path *path, char *type, int flags, |
1921 | int mnt_flags, char *name, void *data) |
1922 | { |
1923 | struct vfsmount *mnt; |
1924 | int err; |
1925 | |
1926 | if (!type) |
1927 | return -EINVAL; |
1928 | |
1929 | /* we need capabilities... */ |
1930 | if (!capable(CAP_SYS_ADMIN)) |
1931 | return -EPERM; |
1932 | |
1933 | mnt = do_kern_mount(type, flags, name, data); |
1934 | if (IS_ERR(mnt)) |
1935 | return PTR_ERR(mnt); |
1936 | |
1937 | err = do_add_mount(real_mount(mnt), path, mnt_flags); |
1938 | if (err) |
1939 | mntput(mnt); |
1940 | return err; |
1941 | } |
1942 | |
1943 | int finish_automount(struct vfsmount *m, struct path *path) |
1944 | { |
1945 | struct mount *mnt = real_mount(m); |
1946 | int err; |
1947 | /* The new mount record should have at least 2 refs to prevent it being |
1948 | * expired before we get a chance to add it |
1949 | */ |
1950 | BUG_ON(mnt_get_count(mnt) < 2); |
1951 | |
1952 | if (m->mnt_sb == path->mnt->mnt_sb && |
1953 | m->mnt_root == path->dentry) { |
1954 | err = -ELOOP; |
1955 | goto fail; |
1956 | } |
1957 | |
1958 | err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE); |
1959 | if (!err) |
1960 | return 0; |
1961 | fail: |
1962 | /* remove m from any expiration list it may be on */ |
1963 | if (!list_empty(&mnt->mnt_expire)) { |
1964 | down_write(&namespace_sem); |
1965 | br_write_lock(&vfsmount_lock); |
1966 | list_del_init(&mnt->mnt_expire); |
1967 | br_write_unlock(&vfsmount_lock); |
1968 | up_write(&namespace_sem); |
1969 | } |
1970 | mntput(m); |
1971 | mntput(m); |
1972 | return err; |
1973 | } |
1974 | |
1975 | /** |
1976 | * mnt_set_expiry - Put a mount on an expiration list |
1977 | * @mnt: The mount to list. |
1978 | * @expiry_list: The list to add the mount to. |
1979 | */ |
1980 | void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list) |
1981 | { |
1982 | down_write(&namespace_sem); |
1983 | br_write_lock(&vfsmount_lock); |
1984 | |
1985 | list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list); |
1986 | |
1987 | br_write_unlock(&vfsmount_lock); |
1988 | up_write(&namespace_sem); |
1989 | } |
1990 | EXPORT_SYMBOL(mnt_set_expiry); |
1991 | |
1992 | /* |
1993 | * process a list of expirable mountpoints with the intent of discarding any |
1994 | * mountpoints that aren't in use and haven't been touched since last we came |
1995 | * here |
1996 | */ |
1997 | void mark_mounts_for_expiry(struct list_head *mounts) |
1998 | { |
1999 | struct mount *mnt, *next; |
2000 | LIST_HEAD(graveyard); |
2001 | LIST_HEAD(umounts); |
2002 | |
2003 | if (list_empty(mounts)) |
2004 | return; |
2005 | |
2006 | down_write(&namespace_sem); |
2007 | br_write_lock(&vfsmount_lock); |
2008 | |
2009 | /* extract from the expiration list every vfsmount that matches the |
2010 | * following criteria: |
2011 | * - only referenced by its parent vfsmount |
2012 | * - still marked for expiry (marked on the last call here; marks are |
2013 | * cleared by mntput()) |
2014 | */ |
2015 | list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { |
2016 | if (!xchg(&mnt->mnt_expiry_mark, 1) || |
2017 | propagate_mount_busy(mnt, 1)) |
2018 | continue; |
2019 | list_move(&mnt->mnt_expire, &graveyard); |
2020 | } |
2021 | while (!list_empty(&graveyard)) { |
2022 | mnt = list_first_entry(&graveyard, struct mount, mnt_expire); |
2023 | touch_mnt_namespace(mnt->mnt_ns); |
2024 | umount_tree(mnt, 1, &umounts); |
2025 | } |
2026 | br_write_unlock(&vfsmount_lock); |
2027 | up_write(&namespace_sem); |
2028 | |
2029 | release_mounts(&umounts); |
2030 | } |
2031 | |
2032 | EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); |
2033 | |
2034 | /* |
2035 | * Ripoff of 'select_parent()' |
2036 | * |
2037 | * search the list of submounts for a given mountpoint, and move any |
2038 | * shrinkable submounts to the 'graveyard' list. |
2039 | */ |
2040 | static int select_submounts(struct mount *parent, struct list_head *graveyard) |
2041 | { |
2042 | struct mount *this_parent = parent; |
2043 | struct list_head *next; |
2044 | int found = 0; |
2045 | |
2046 | repeat: |
2047 | next = this_parent->mnt_mounts.next; |
2048 | resume: |
2049 | while (next != &this_parent->mnt_mounts) { |
2050 | struct list_head *tmp = next; |
2051 | struct mount *mnt = list_entry(tmp, struct mount, mnt_child); |
2052 | |
2053 | next = tmp->next; |
2054 | if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE)) |
2055 | continue; |
2056 | /* |
2057 | * Descend a level if the d_mounts list is non-empty. |
2058 | */ |
2059 | if (!list_empty(&mnt->mnt_mounts)) { |
2060 | this_parent = mnt; |
2061 | goto repeat; |
2062 | } |
2063 | |
2064 | if (!propagate_mount_busy(mnt, 1)) { |
2065 | list_move_tail(&mnt->mnt_expire, graveyard); |
2066 | found++; |
2067 | } |
2068 | } |
2069 | /* |
2070 | * All done at this level ... ascend and resume the search |
2071 | */ |
2072 | if (this_parent != parent) { |
2073 | next = this_parent->mnt_child.next; |
2074 | this_parent = this_parent->mnt_parent; |
2075 | goto resume; |
2076 | } |
2077 | return found; |
2078 | } |
2079 | |
2080 | /* |
2081 | * process a list of expirable mountpoints with the intent of discarding any |
2082 | * submounts of a specific parent mountpoint |
2083 | * |
2084 | * vfsmount_lock must be held for write |
2085 | */ |
2086 | static void shrink_submounts(struct mount *mnt, struct list_head *umounts) |
2087 | { |
2088 | LIST_HEAD(graveyard); |
2089 | struct mount *m; |
2090 | |
2091 | /* extract submounts of 'mountpoint' from the expiration list */ |
2092 | while (select_submounts(mnt, &graveyard)) { |
2093 | while (!list_empty(&graveyard)) { |
2094 | m = list_first_entry(&graveyard, struct mount, |
2095 | mnt_expire); |
2096 | touch_mnt_namespace(m->mnt_ns); |
2097 | umount_tree(m, 1, umounts); |
2098 | } |
2099 | } |
2100 | } |
2101 | |
2102 | /* |
2103 | * Some copy_from_user() implementations do not return the exact number of |
2104 | * bytes remaining to copy on a fault. But copy_mount_options() requires that. |
2105 | * Note that this function differs from copy_from_user() in that it will oops |
2106 | * on bad values of `to', rather than returning a short copy. |
2107 | */ |
2108 | static long exact_copy_from_user(void *to, const void __user * from, |
2109 | unsigned long n) |
2110 | { |
2111 | char *t = to; |
2112 | const char __user *f = from; |
2113 | char c; |
2114 | |
2115 | if (!access_ok(VERIFY_READ, from, n)) |
2116 | return n; |
2117 | |
2118 | while (n) { |
2119 | if (__get_user(c, f)) { |
2120 | memset(t, 0, n); |
2121 | break; |
2122 | } |
2123 | *t++ = c; |
2124 | f++; |
2125 | n--; |
2126 | } |
2127 | return n; |
2128 | } |
2129 | |
2130 | int copy_mount_options(const void __user * data, unsigned long *where) |
2131 | { |
2132 | int i; |
2133 | unsigned long page; |
2134 | unsigned long size; |
2135 | |
2136 | *where = 0; |
2137 | if (!data) |
2138 | return 0; |
2139 | |
2140 | if (!(page = __get_free_page(GFP_KERNEL))) |
2141 | return -ENOMEM; |
2142 | |
2143 | /* We only care that *some* data at the address the user |
2144 | * gave us is valid. Just in case, we'll zero |
2145 | * the remainder of the page. |
2146 | */ |
2147 | /* copy_from_user cannot cross TASK_SIZE ! */ |
2148 | size = TASK_SIZE - (unsigned long)data; |
2149 | if (size > PAGE_SIZE) |
2150 | size = PAGE_SIZE; |
2151 | |
2152 | i = size - exact_copy_from_user((void *)page, data, size); |
2153 | if (!i) { |
2154 | free_page(page); |
2155 | return -EFAULT; |
2156 | } |
2157 | if (i != PAGE_SIZE) |
2158 | memset((char *)page + i, 0, PAGE_SIZE - i); |
2159 | *where = page; |
2160 | return 0; |
2161 | } |
2162 | |
2163 | int copy_mount_string(const void __user *data, char **where) |
2164 | { |
2165 | char *tmp; |
2166 | |
2167 | if (!data) { |
2168 | *where = NULL; |
2169 | return 0; |
2170 | } |
2171 | |
2172 | tmp = strndup_user(data, PAGE_SIZE); |
2173 | if (IS_ERR(tmp)) |
2174 | return PTR_ERR(tmp); |
2175 | |
2176 | *where = tmp; |
2177 | return 0; |
2178 | } |
2179 | |
2180 | /* |
2181 | * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to |
2182 | * be given to the mount() call (ie: read-only, no-dev, no-suid etc). |
2183 | * |
2184 | * data is a (void *) that can point to any structure up to |
2185 | * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent |
2186 | * information (or be NULL). |
2187 | * |
2188 | * Pre-0.97 versions of mount() didn't have a flags word. |
2189 | * When the flags word was introduced its top half was required |
2190 | * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. |
2191 | * Therefore, if this magic number is present, it carries no information |
2192 | * and must be discarded. |
2193 | */ |
2194 | long do_mount(char *dev_name, char *dir_name, char *type_page, |
2195 | unsigned long flags, void *data_page) |
2196 | { |
2197 | struct path path; |
2198 | int retval = 0; |
2199 | int mnt_flags = 0; |
2200 | |
2201 | /* Discard magic */ |
2202 | if ((flags & MS_MGC_MSK) == MS_MGC_VAL) |
2203 | flags &= ~MS_MGC_MSK; |
2204 | |
2205 | /* Basic sanity checks */ |
2206 | |
2207 | if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) |
2208 | return -EINVAL; |
2209 | |
2210 | if (data_page) |
2211 | ((char *)data_page)[PAGE_SIZE - 1] = 0; |
2212 | |
2213 | /* ... and get the mountpoint */ |
2214 | retval = kern_path(dir_name, LOOKUP_FOLLOW, &path); |
2215 | if (retval) |
2216 | return retval; |
2217 | |
2218 | retval = security_sb_mount(dev_name, &path, |
2219 | type_page, flags, data_page); |
2220 | if (retval) |
2221 | goto dput_out; |
2222 | |
2223 | /* Default to relatime unless overriden */ |
2224 | if (!(flags & MS_NOATIME)) |
2225 | mnt_flags |= MNT_RELATIME; |
2226 | |
2227 | /* Separate the per-mountpoint flags */ |
2228 | if (flags & MS_NOSUID) |
2229 | mnt_flags |= MNT_NOSUID; |
2230 | if (flags & MS_NODEV) |
2231 | mnt_flags |= MNT_NODEV; |
2232 | if (flags & MS_NOEXEC) |
2233 | mnt_flags |= MNT_NOEXEC; |
2234 | if (flags & MS_NOATIME) |
2235 | mnt_flags |= MNT_NOATIME; |
2236 | if (flags & MS_NODIRATIME) |
2237 | mnt_flags |= MNT_NODIRATIME; |
2238 | if (flags & MS_STRICTATIME) |
2239 | mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); |
2240 | if (flags & MS_RDONLY) |
2241 | mnt_flags |= MNT_READONLY; |
2242 | |
2243 | flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN | |
2244 | MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT | |
2245 | MS_STRICTATIME); |
2246 | |
2247 | if (flags & MS_REMOUNT) |
2248 | retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags, |
2249 | data_page); |
2250 | else if (flags & MS_BIND) |
2251 | retval = do_loopback(&path, dev_name, flags & MS_REC); |
2252 | else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
2253 | retval = do_change_type(&path, flags); |
2254 | else if (flags & MS_MOVE) |
2255 | retval = do_move_mount(&path, dev_name); |
2256 | else |
2257 | retval = do_new_mount(&path, type_page, flags, mnt_flags, |
2258 | dev_name, data_page); |
2259 | dput_out: |
2260 | path_put(&path); |
2261 | return retval; |
2262 | } |
2263 | |
2264 | static struct mnt_namespace *alloc_mnt_ns(void) |
2265 | { |
2266 | struct mnt_namespace *new_ns; |
2267 | |
2268 | new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); |
2269 | if (!new_ns) |
2270 | return ERR_PTR(-ENOMEM); |
2271 | atomic_set(&new_ns->count, 1); |
2272 | new_ns->root = NULL; |
2273 | INIT_LIST_HEAD(&new_ns->list); |
2274 | init_waitqueue_head(&new_ns->poll); |
2275 | new_ns->event = 0; |
2276 | return new_ns; |
2277 | } |
2278 | |
2279 | /* |
2280 | * Allocate a new namespace structure and populate it with contents |
2281 | * copied from the namespace of the passed in task structure. |
2282 | */ |
2283 | static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns, |
2284 | struct fs_struct *fs) |
2285 | { |
2286 | struct mnt_namespace *new_ns; |
2287 | struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; |
2288 | struct mount *p, *q; |
2289 | struct mount *old = mnt_ns->root; |
2290 | struct mount *new; |
2291 | |
2292 | new_ns = alloc_mnt_ns(); |
2293 | if (IS_ERR(new_ns)) |
2294 | return new_ns; |
2295 | |
2296 | down_write(&namespace_sem); |
2297 | /* First pass: copy the tree topology */ |
2298 | new = copy_tree(old, old->mnt.mnt_root, CL_COPY_ALL | CL_EXPIRE); |
2299 | if (IS_ERR(new)) { |
2300 | up_write(&namespace_sem); |
2301 | kfree(new_ns); |
2302 | return ERR_CAST(new); |
2303 | } |
2304 | new_ns->root = new; |
2305 | br_write_lock(&vfsmount_lock); |
2306 | list_add_tail(&new_ns->list, &new->mnt_list); |
2307 | br_write_unlock(&vfsmount_lock); |
2308 | |
2309 | /* |
2310 | * Second pass: switch the tsk->fs->* elements and mark new vfsmounts |
2311 | * as belonging to new namespace. We have already acquired a private |
2312 | * fs_struct, so tsk->fs->lock is not needed. |
2313 | */ |
2314 | p = old; |
2315 | q = new; |
2316 | while (p) { |
2317 | q->mnt_ns = new_ns; |
2318 | if (fs) { |
2319 | if (&p->mnt == fs->root.mnt) { |
2320 | fs->root.mnt = mntget(&q->mnt); |
2321 | rootmnt = &p->mnt; |
2322 | } |
2323 | if (&p->mnt == fs->pwd.mnt) { |
2324 | fs->pwd.mnt = mntget(&q->mnt); |
2325 | pwdmnt = &p->mnt; |
2326 | } |
2327 | } |
2328 | p = next_mnt(p, old); |
2329 | q = next_mnt(q, new); |
2330 | } |
2331 | up_write(&namespace_sem); |
2332 | |
2333 | if (rootmnt) |
2334 | mntput(rootmnt); |
2335 | if (pwdmnt) |
2336 | mntput(pwdmnt); |
2337 | |
2338 | return new_ns; |
2339 | } |
2340 | |
2341 | struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, |
2342 | struct fs_struct *new_fs) |
2343 | { |
2344 | struct mnt_namespace *new_ns; |
2345 | |
2346 | BUG_ON(!ns); |
2347 | get_mnt_ns(ns); |
2348 | |
2349 | if (!(flags & CLONE_NEWNS)) |
2350 | return ns; |
2351 | |
2352 | new_ns = dup_mnt_ns(ns, new_fs); |
2353 | |
2354 | put_mnt_ns(ns); |
2355 | return new_ns; |
2356 | } |
2357 | |
2358 | /** |
2359 | * create_mnt_ns - creates a private namespace and adds a root filesystem |
2360 | * @mnt: pointer to the new root filesystem mountpoint |
2361 | */ |
2362 | static struct mnt_namespace *create_mnt_ns(struct vfsmount *m) |
2363 | { |
2364 | struct mnt_namespace *new_ns = alloc_mnt_ns(); |
2365 | if (!IS_ERR(new_ns)) { |
2366 | struct mount *mnt = real_mount(m); |
2367 | mnt->mnt_ns = new_ns; |
2368 | new_ns->root = mnt; |
2369 | list_add(&new_ns->list, &mnt->mnt_list); |
2370 | } else { |
2371 | mntput(m); |
2372 | } |
2373 | return new_ns; |
2374 | } |
2375 | |
2376 | struct dentry *mount_subtree(struct vfsmount *mnt, const char *name) |
2377 | { |
2378 | struct mnt_namespace *ns; |
2379 | struct super_block *s; |
2380 | struct path path; |
2381 | int err; |
2382 | |
2383 | ns = create_mnt_ns(mnt); |
2384 | if (IS_ERR(ns)) |
2385 | return ERR_CAST(ns); |
2386 | |
2387 | err = vfs_path_lookup(mnt->mnt_root, mnt, |
2388 | name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); |
2389 | |
2390 | put_mnt_ns(ns); |
2391 | |
2392 | if (err) |
2393 | return ERR_PTR(err); |
2394 | |
2395 | /* trade a vfsmount reference for active sb one */ |
2396 | s = path.mnt->mnt_sb; |
2397 | atomic_inc(&s->s_active); |
2398 | mntput(path.mnt); |
2399 | /* lock the sucker */ |
2400 | down_write(&s->s_umount); |
2401 | /* ... and return the root of (sub)tree on it */ |
2402 | return path.dentry; |
2403 | } |
2404 | EXPORT_SYMBOL(mount_subtree); |
2405 | |
2406 | SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, |
2407 | char __user *, type, unsigned long, flags, void __user *, data) |
2408 | { |
2409 | int ret; |
2410 | char *kernel_type; |
2411 | char *kernel_dir; |
2412 | char *kernel_dev; |
2413 | unsigned long data_page; |
2414 | |
2415 | ret = copy_mount_string(type, &kernel_type); |
2416 | if (ret < 0) |
2417 | goto out_type; |
2418 | |
2419 | kernel_dir = getname(dir_name); |
2420 | if (IS_ERR(kernel_dir)) { |
2421 | ret = PTR_ERR(kernel_dir); |
2422 | goto out_dir; |
2423 | } |
2424 | |
2425 | ret = copy_mount_string(dev_name, &kernel_dev); |
2426 | if (ret < 0) |
2427 | goto out_dev; |
2428 | |
2429 | ret = copy_mount_options(data, &data_page); |
2430 | if (ret < 0) |
2431 | goto out_data; |
2432 | |
2433 | ret = do_mount(kernel_dev, kernel_dir, kernel_type, flags, |
2434 | (void *) data_page); |
2435 | |
2436 | free_page(data_page); |
2437 | out_data: |
2438 | kfree(kernel_dev); |
2439 | out_dev: |
2440 | putname(kernel_dir); |
2441 | out_dir: |
2442 | kfree(kernel_type); |
2443 | out_type: |
2444 | return ret; |
2445 | } |
2446 | |
2447 | /* |
2448 | * Return true if path is reachable from root |
2449 | * |
2450 | * namespace_sem or vfsmount_lock is held |
2451 | */ |
2452 | bool is_path_reachable(struct mount *mnt, struct dentry *dentry, |
2453 | const struct path *root) |
2454 | { |
2455 | while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) { |
2456 | dentry = mnt->mnt_mountpoint; |
2457 | mnt = mnt->mnt_parent; |
2458 | } |
2459 | return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry); |
2460 | } |
2461 | |
2462 | int path_is_under(struct path *path1, struct path *path2) |
2463 | { |
2464 | int res; |
2465 | br_read_lock(&vfsmount_lock); |
2466 | res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2); |
2467 | br_read_unlock(&vfsmount_lock); |
2468 | return res; |
2469 | } |
2470 | EXPORT_SYMBOL(path_is_under); |
2471 | |
2472 | /* |
2473 | * pivot_root Semantics: |
2474 | * Moves the root file system of the current process to the directory put_old, |
2475 | * makes new_root as the new root file system of the current process, and sets |
2476 | * root/cwd of all processes which had them on the current root to new_root. |
2477 | * |
2478 | * Restrictions: |
2479 | * The new_root and put_old must be directories, and must not be on the |
2480 | * same file system as the current process root. The put_old must be |
2481 | * underneath new_root, i.e. adding a non-zero number of /.. to the string |
2482 | * pointed to by put_old must yield the same directory as new_root. No other |
2483 | * file system may be mounted on put_old. After all, new_root is a mountpoint. |
2484 | * |
2485 | * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. |
2486 | * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives |
2487 | * in this situation. |
2488 | * |
2489 | * Notes: |
2490 | * - we don't move root/cwd if they are not at the root (reason: if something |
2491 | * cared enough to change them, it's probably wrong to force them elsewhere) |
2492 | * - it's okay to pick a root that isn't the root of a file system, e.g. |
2493 | * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, |
2494 | * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root |
2495 | * first. |
2496 | */ |
2497 | SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, |
2498 | const char __user *, put_old) |
2499 | { |
2500 | struct path new, old, parent_path, root_parent, root; |
2501 | struct mount *new_mnt, *root_mnt; |
2502 | int error; |
2503 | |
2504 | if (!capable(CAP_SYS_ADMIN)) |
2505 | return -EPERM; |
2506 | |
2507 | error = user_path_dir(new_root, &new); |
2508 | if (error) |
2509 | goto out0; |
2510 | |
2511 | error = user_path_dir(put_old, &old); |
2512 | if (error) |
2513 | goto out1; |
2514 | |
2515 | error = security_sb_pivotroot(&old, &new); |
2516 | if (error) |
2517 | goto out2; |
2518 | |
2519 | get_fs_root(current->fs, &root); |
2520 | error = lock_mount(&old); |
2521 | if (error) |
2522 | goto out3; |
2523 | |
2524 | error = -EINVAL; |
2525 | new_mnt = real_mount(new.mnt); |
2526 | root_mnt = real_mount(root.mnt); |
2527 | if (IS_MNT_SHARED(real_mount(old.mnt)) || |
2528 | IS_MNT_SHARED(new_mnt->mnt_parent) || |
2529 | IS_MNT_SHARED(root_mnt->mnt_parent)) |
2530 | goto out4; |
2531 | if (!check_mnt(root_mnt) || !check_mnt(new_mnt)) |
2532 | goto out4; |
2533 | error = -ENOENT; |
2534 | if (d_unlinked(new.dentry)) |
2535 | goto out4; |
2536 | if (d_unlinked(old.dentry)) |
2537 | goto out4; |
2538 | error = -EBUSY; |
2539 | if (new.mnt == root.mnt || |
2540 | old.mnt == root.mnt) |
2541 | goto out4; /* loop, on the same file system */ |
2542 | error = -EINVAL; |
2543 | if (root.mnt->mnt_root != root.dentry) |
2544 | goto out4; /* not a mountpoint */ |
2545 | if (!mnt_has_parent(root_mnt)) |
2546 | goto out4; /* not attached */ |
2547 | if (new.mnt->mnt_root != new.dentry) |
2548 | goto out4; /* not a mountpoint */ |
2549 | if (!mnt_has_parent(new_mnt)) |
2550 | goto out4; /* not attached */ |
2551 | /* make sure we can reach put_old from new_root */ |
2552 | if (!is_path_reachable(real_mount(old.mnt), old.dentry, &new)) |
2553 | goto out4; |
2554 | br_write_lock(&vfsmount_lock); |
2555 | detach_mnt(new_mnt, &parent_path); |
2556 | detach_mnt(root_mnt, &root_parent); |
2557 | /* mount old root on put_old */ |
2558 | attach_mnt(root_mnt, &old); |
2559 | /* mount new_root on / */ |
2560 | attach_mnt(new_mnt, &root_parent); |
2561 | touch_mnt_namespace(current->nsproxy->mnt_ns); |
2562 | br_write_unlock(&vfsmount_lock); |
2563 | chroot_fs_refs(&root, &new); |
2564 | error = 0; |
2565 | out4: |
2566 | unlock_mount(&old); |
2567 | if (!error) { |
2568 | path_put(&root_parent); |
2569 | path_put(&parent_path); |
2570 | } |
2571 | out3: |
2572 | path_put(&root); |
2573 | out2: |
2574 | path_put(&old); |
2575 | out1: |
2576 | path_put(&new); |
2577 | out0: |
2578 | return error; |
2579 | } |
2580 | |
2581 | static void __init init_mount_tree(void) |
2582 | { |
2583 | struct vfsmount *mnt; |
2584 | struct mnt_namespace *ns; |
2585 | struct path root; |
2586 | |
2587 | mnt = do_kern_mount("rootfs", 0, "rootfs", NULL); |
2588 | if (IS_ERR(mnt)) |
2589 | panic("Can't create rootfs"); |
2590 | |
2591 | ns = create_mnt_ns(mnt); |
2592 | if (IS_ERR(ns)) |
2593 | panic("Can't allocate initial namespace"); |
2594 | |
2595 | init_task.nsproxy->mnt_ns = ns; |
2596 | get_mnt_ns(ns); |
2597 | |
2598 | root.mnt = mnt; |
2599 | root.dentry = mnt->mnt_root; |
2600 | |
2601 | set_fs_pwd(current->fs, &root); |
2602 | set_fs_root(current->fs, &root); |
2603 | } |
2604 | |
2605 | void __init mnt_init(void) |
2606 | { |
2607 | unsigned u; |
2608 | int err; |
2609 | |
2610 | init_rwsem(&namespace_sem); |
2611 | |
2612 | mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount), |
2613 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); |
2614 | |
2615 | mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); |
2616 | |
2617 | if (!mount_hashtable) |
2618 | panic("Failed to allocate mount hash table\n"); |
2619 | |
2620 | printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE); |
2621 | |
2622 | for (u = 0; u < HASH_SIZE; u++) |
2623 | INIT_LIST_HEAD(&mount_hashtable[u]); |
2624 | |
2625 | br_lock_init(&vfsmount_lock); |
2626 | |
2627 | err = sysfs_init(); |
2628 | if (err) |
2629 | printk(KERN_WARNING "%s: sysfs_init error: %d\n", |
2630 | __func__, err); |
2631 | fs_kobj = kobject_create_and_add("fs", NULL); |
2632 | if (!fs_kobj) |
2633 | printk(KERN_WARNING "%s: kobj create error\n", __func__); |
2634 | init_rootfs(); |
2635 | init_mount_tree(); |
2636 | } |
2637 | |
2638 | void put_mnt_ns(struct mnt_namespace *ns) |
2639 | { |
2640 | LIST_HEAD(umount_list); |
2641 | |
2642 | if (!atomic_dec_and_test(&ns->count)) |
2643 | return; |
2644 | down_write(&namespace_sem); |
2645 | br_write_lock(&vfsmount_lock); |
2646 | umount_tree(ns->root, 0, &umount_list); |
2647 | br_write_unlock(&vfsmount_lock); |
2648 | up_write(&namespace_sem); |
2649 | release_mounts(&umount_list); |
2650 | kfree(ns); |
2651 | } |
2652 | |
2653 | struct vfsmount *kern_mount_data(struct file_system_type *type, void *data) |
2654 | { |
2655 | struct vfsmount *mnt; |
2656 | mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data); |
2657 | if (!IS_ERR(mnt)) { |
2658 | /* |
2659 | * it is a longterm mount, don't release mnt until |
2660 | * we unmount before file sys is unregistered |
2661 | */ |
2662 | real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL; |
2663 | } |
2664 | return mnt; |
2665 | } |
2666 | EXPORT_SYMBOL_GPL(kern_mount_data); |
2667 | |
2668 | void kern_unmount(struct vfsmount *mnt) |
2669 | { |
2670 | /* release long term mount so mount point can be released */ |
2671 | if (!IS_ERR_OR_NULL(mnt)) { |
2672 | br_write_lock(&vfsmount_lock); |
2673 | real_mount(mnt)->mnt_ns = NULL; |
2674 | br_write_unlock(&vfsmount_lock); |
2675 | mntput(mnt); |
2676 | } |
2677 | } |
2678 | EXPORT_SYMBOL(kern_unmount); |
2679 | |
2680 | bool our_mnt(struct vfsmount *mnt) |
2681 | { |
2682 | return check_mnt(real_mount(mnt)); |
2683 | } |
2684 |
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