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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/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/ramfs.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_fs.h> |
25 | #include "pnode.h" |
26 | #include "internal.h" |
27 | |
28 | #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head)) |
29 | #define HASH_SIZE (1UL << HASH_SHIFT) |
30 | |
31 | static int event; |
32 | static DEFINE_IDA(mnt_id_ida); |
33 | static DEFINE_IDA(mnt_group_ida); |
34 | static DEFINE_SPINLOCK(mnt_id_lock); |
35 | static int mnt_id_start = 0; |
36 | static int mnt_group_start = 1; |
37 | |
38 | static struct list_head *mount_hashtable __read_mostly; |
39 | static struct kmem_cache *mnt_cache __read_mostly; |
40 | static struct rw_semaphore namespace_sem; |
41 | |
42 | /* /sys/fs */ |
43 | struct kobject *fs_kobj; |
44 | EXPORT_SYMBOL_GPL(fs_kobj); |
45 | |
46 | /* |
47 | * vfsmount lock may be taken for read to prevent changes to the |
48 | * vfsmount hash, ie. during mountpoint lookups or walking back |
49 | * up the tree. |
50 | * |
51 | * It should be taken for write in all cases where the vfsmount |
52 | * tree or hash is modified or when a vfsmount structure is modified. |
53 | */ |
54 | DEFINE_BRLOCK(vfsmount_lock); |
55 | |
56 | static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) |
57 | { |
58 | unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); |
59 | tmp += ((unsigned long)dentry / L1_CACHE_BYTES); |
60 | tmp = tmp + (tmp >> HASH_SHIFT); |
61 | return tmp & (HASH_SIZE - 1); |
62 | } |
63 | |
64 | #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16) |
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 | br_write_lock(&vfsmount_lock); |
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 | br_write_unlock(&vfsmount_lock); |
494 | return ret; |
495 | } |
496 | |
497 | static void __mnt_unmake_readonly(struct mount *mnt) |
498 | { |
499 | br_write_lock(&vfsmount_lock); |
500 | mnt->mnt.mnt_flags &= ~MNT_READONLY; |
501 | br_write_unlock(&vfsmount_lock); |
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 | br_write_lock(&vfsmount_lock); |
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 | br_write_unlock(&vfsmount_lock); |
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 | /* |
551 | * find the first or last mount at @dentry on vfsmount @mnt depending on |
552 | * @dir. If @dir is set return the first mount else return the last mount. |
553 | * vfsmount_lock must be held for read or write. |
554 | */ |
555 | struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry, |
556 | int dir) |
557 | { |
558 | struct list_head *head = mount_hashtable + hash(mnt, dentry); |
559 | struct list_head *tmp = head; |
560 | struct mount *p, *found = NULL; |
561 | |
562 | for (;;) { |
563 | tmp = dir ? tmp->next : tmp->prev; |
564 | p = NULL; |
565 | if (tmp == head) |
566 | break; |
567 | p = list_entry(tmp, struct mount, mnt_hash); |
568 | if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) { |
569 | found = p; |
570 | break; |
571 | } |
572 | } |
573 | return found; |
574 | } |
575 | |
576 | /* |
577 | * lookup_mnt - Return the first child mount mounted at path |
578 | * |
579 | * "First" means first mounted chronologically. If you create the |
580 | * following mounts: |
581 | * |
582 | * mount /dev/sda1 /mnt |
583 | * mount /dev/sda2 /mnt |
584 | * mount /dev/sda3 /mnt |
585 | * |
586 | * Then lookup_mnt() on the base /mnt dentry in the root mount will |
587 | * return successively the root dentry and vfsmount of /dev/sda1, then |
588 | * /dev/sda2, then /dev/sda3, then NULL. |
589 | * |
590 | * lookup_mnt takes a reference to the found vfsmount. |
591 | */ |
592 | struct vfsmount *lookup_mnt(struct path *path) |
593 | { |
594 | struct mount *child_mnt; |
595 | |
596 | br_read_lock(&vfsmount_lock); |
597 | child_mnt = __lookup_mnt(path->mnt, path->dentry, 1); |
598 | if (child_mnt) { |
599 | mnt_add_count(child_mnt, 1); |
600 | br_read_unlock(&vfsmount_lock); |
601 | return &child_mnt->mnt; |
602 | } else { |
603 | br_read_unlock(&vfsmount_lock); |
604 | return NULL; |
605 | } |
606 | } |
607 | |
608 | static inline int check_mnt(struct mount *mnt) |
609 | { |
610 | return mnt->mnt_ns == current->nsproxy->mnt_ns; |
611 | } |
612 | |
613 | /* |
614 | * vfsmount lock must be held for write |
615 | */ |
616 | static void touch_mnt_namespace(struct mnt_namespace *ns) |
617 | { |
618 | if (ns) { |
619 | ns->event = ++event; |
620 | wake_up_interruptible(&ns->poll); |
621 | } |
622 | } |
623 | |
624 | /* |
625 | * vfsmount lock must be held for write |
626 | */ |
627 | static void __touch_mnt_namespace(struct mnt_namespace *ns) |
628 | { |
629 | if (ns && ns->event != event) { |
630 | ns->event = event; |
631 | wake_up_interruptible(&ns->poll); |
632 | } |
633 | } |
634 | |
635 | /* |
636 | * Clear dentry's mounted state if it has no remaining mounts. |
637 | * vfsmount_lock must be held for write. |
638 | */ |
639 | static void dentry_reset_mounted(struct dentry *dentry) |
640 | { |
641 | unsigned u; |
642 | |
643 | for (u = 0; u < HASH_SIZE; u++) { |
644 | struct mount *p; |
645 | |
646 | list_for_each_entry(p, &mount_hashtable[u], mnt_hash) { |
647 | if (p->mnt_mountpoint == dentry) |
648 | return; |
649 | } |
650 | } |
651 | spin_lock(&dentry->d_lock); |
652 | dentry->d_flags &= ~DCACHE_MOUNTED; |
653 | spin_unlock(&dentry->d_lock); |
654 | } |
655 | |
656 | /* |
657 | * vfsmount lock must be held for write |
658 | */ |
659 | static void detach_mnt(struct mount *mnt, struct path *old_path) |
660 | { |
661 | old_path->dentry = mnt->mnt_mountpoint; |
662 | old_path->mnt = &mnt->mnt_parent->mnt; |
663 | mnt->mnt_parent = mnt; |
664 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
665 | list_del_init(&mnt->mnt_child); |
666 | list_del_init(&mnt->mnt_hash); |
667 | dentry_reset_mounted(old_path->dentry); |
668 | } |
669 | |
670 | /* |
671 | * vfsmount lock must be held for write |
672 | */ |
673 | void mnt_set_mountpoint(struct mount *mnt, struct dentry *dentry, |
674 | struct mount *child_mnt) |
675 | { |
676 | mnt_add_count(mnt, 1); /* essentially, that's mntget */ |
677 | child_mnt->mnt_mountpoint = dget(dentry); |
678 | child_mnt->mnt_parent = mnt; |
679 | spin_lock(&dentry->d_lock); |
680 | dentry->d_flags |= DCACHE_MOUNTED; |
681 | spin_unlock(&dentry->d_lock); |
682 | } |
683 | |
684 | /* |
685 | * vfsmount lock must be held for write |
686 | */ |
687 | static void attach_mnt(struct mount *mnt, struct path *path) |
688 | { |
689 | mnt_set_mountpoint(real_mount(path->mnt), path->dentry, mnt); |
690 | list_add_tail(&mnt->mnt_hash, mount_hashtable + |
691 | hash(path->mnt, path->dentry)); |
692 | list_add_tail(&mnt->mnt_child, &real_mount(path->mnt)->mnt_mounts); |
693 | } |
694 | |
695 | /* |
696 | * vfsmount lock must be held for write |
697 | */ |
698 | static void commit_tree(struct mount *mnt) |
699 | { |
700 | struct mount *parent = mnt->mnt_parent; |
701 | struct mount *m; |
702 | LIST_HEAD(head); |
703 | struct mnt_namespace *n = parent->mnt_ns; |
704 | |
705 | BUG_ON(parent == mnt); |
706 | |
707 | list_add_tail(&head, &mnt->mnt_list); |
708 | list_for_each_entry(m, &head, mnt_list) |
709 | m->mnt_ns = n; |
710 | |
711 | list_splice(&head, n->list.prev); |
712 | |
713 | list_add_tail(&mnt->mnt_hash, mount_hashtable + |
714 | hash(&parent->mnt, mnt->mnt_mountpoint)); |
715 | list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); |
716 | touch_mnt_namespace(n); |
717 | } |
718 | |
719 | static struct mount *next_mnt(struct mount *p, struct mount *root) |
720 | { |
721 | struct list_head *next = p->mnt_mounts.next; |
722 | if (next == &p->mnt_mounts) { |
723 | while (1) { |
724 | if (p == root) |
725 | return NULL; |
726 | next = p->mnt_child.next; |
727 | if (next != &p->mnt_parent->mnt_mounts) |
728 | break; |
729 | p = p->mnt_parent; |
730 | } |
731 | } |
732 | return list_entry(next, struct mount, mnt_child); |
733 | } |
734 | |
735 | static struct mount *skip_mnt_tree(struct mount *p) |
736 | { |
737 | struct list_head *prev = p->mnt_mounts.prev; |
738 | while (prev != &p->mnt_mounts) { |
739 | p = list_entry(prev, struct mount, mnt_child); |
740 | prev = p->mnt_mounts.prev; |
741 | } |
742 | return p; |
743 | } |
744 | |
745 | struct vfsmount * |
746 | vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data) |
747 | { |
748 | struct mount *mnt; |
749 | struct dentry *root; |
750 | |
751 | if (!type) |
752 | return ERR_PTR(-ENODEV); |
753 | |
754 | mnt = alloc_vfsmnt(name); |
755 | if (!mnt) |
756 | return ERR_PTR(-ENOMEM); |
757 | |
758 | if (flags & MS_KERNMOUNT) |
759 | mnt->mnt.mnt_flags = MNT_INTERNAL; |
760 | |
761 | root = mount_fs(type, flags, name, data); |
762 | if (IS_ERR(root)) { |
763 | free_vfsmnt(mnt); |
764 | return ERR_CAST(root); |
765 | } |
766 | |
767 | mnt->mnt.mnt_root = root; |
768 | mnt->mnt.mnt_sb = root->d_sb; |
769 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
770 | mnt->mnt_parent = mnt; |
771 | br_write_lock(&vfsmount_lock); |
772 | list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts); |
773 | br_write_unlock(&vfsmount_lock); |
774 | return &mnt->mnt; |
775 | } |
776 | EXPORT_SYMBOL_GPL(vfs_kern_mount); |
777 | |
778 | static struct mount *clone_mnt(struct mount *old, struct dentry *root, |
779 | int flag) |
780 | { |
781 | struct super_block *sb = old->mnt.mnt_sb; |
782 | struct mount *mnt; |
783 | int err; |
784 | |
785 | mnt = alloc_vfsmnt(old->mnt_devname); |
786 | if (!mnt) |
787 | return ERR_PTR(-ENOMEM); |
788 | |
789 | if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE)) |
790 | mnt->mnt_group_id = 0; /* not a peer of original */ |
791 | else |
792 | mnt->mnt_group_id = old->mnt_group_id; |
793 | |
794 | if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { |
795 | err = mnt_alloc_group_id(mnt); |
796 | if (err) |
797 | goto out_free; |
798 | } |
799 | |
800 | mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD; |
801 | /* Don't allow unprivileged users to change mount flags */ |
802 | if ((flag & CL_UNPRIVILEGED) && (mnt->mnt.mnt_flags & MNT_READONLY)) |
803 | mnt->mnt.mnt_flags |= MNT_LOCK_READONLY; |
804 | |
805 | atomic_inc(&sb->s_active); |
806 | mnt->mnt.mnt_sb = sb; |
807 | mnt->mnt.mnt_root = dget(root); |
808 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
809 | mnt->mnt_parent = mnt; |
810 | br_write_lock(&vfsmount_lock); |
811 | list_add_tail(&mnt->mnt_instance, &sb->s_mounts); |
812 | br_write_unlock(&vfsmount_lock); |
813 | |
814 | if ((flag & CL_SLAVE) || |
815 | ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) { |
816 | list_add(&mnt->mnt_slave, &old->mnt_slave_list); |
817 | mnt->mnt_master = old; |
818 | CLEAR_MNT_SHARED(mnt); |
819 | } else if (!(flag & CL_PRIVATE)) { |
820 | if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old)) |
821 | list_add(&mnt->mnt_share, &old->mnt_share); |
822 | if (IS_MNT_SLAVE(old)) |
823 | list_add(&mnt->mnt_slave, &old->mnt_slave); |
824 | mnt->mnt_master = old->mnt_master; |
825 | } |
826 | if (flag & CL_MAKE_SHARED) |
827 | set_mnt_shared(mnt); |
828 | |
829 | /* stick the duplicate mount on the same expiry list |
830 | * as the original if that was on one */ |
831 | if (flag & CL_EXPIRE) { |
832 | if (!list_empty(&old->mnt_expire)) |
833 | list_add(&mnt->mnt_expire, &old->mnt_expire); |
834 | } |
835 | |
836 | return mnt; |
837 | |
838 | out_free: |
839 | free_vfsmnt(mnt); |
840 | return ERR_PTR(err); |
841 | } |
842 | |
843 | static inline void mntfree(struct mount *mnt) |
844 | { |
845 | struct vfsmount *m = &mnt->mnt; |
846 | struct super_block *sb = m->mnt_sb; |
847 | |
848 | /* |
849 | * This probably indicates that somebody messed |
850 | * up a mnt_want/drop_write() pair. If this |
851 | * happens, the filesystem was probably unable |
852 | * to make r/w->r/o transitions. |
853 | */ |
854 | /* |
855 | * The locking used to deal with mnt_count decrement provides barriers, |
856 | * so mnt_get_writers() below is safe. |
857 | */ |
858 | WARN_ON(mnt_get_writers(mnt)); |
859 | fsnotify_vfsmount_delete(m); |
860 | dput(m->mnt_root); |
861 | free_vfsmnt(mnt); |
862 | deactivate_super(sb); |
863 | } |
864 | |
865 | static void mntput_no_expire(struct mount *mnt) |
866 | { |
867 | put_again: |
868 | #ifdef CONFIG_SMP |
869 | br_read_lock(&vfsmount_lock); |
870 | if (likely(mnt->mnt_ns)) { |
871 | /* shouldn't be the last one */ |
872 | mnt_add_count(mnt, -1); |
873 | br_read_unlock(&vfsmount_lock); |
874 | return; |
875 | } |
876 | br_read_unlock(&vfsmount_lock); |
877 | |
878 | br_write_lock(&vfsmount_lock); |
879 | mnt_add_count(mnt, -1); |
880 | if (mnt_get_count(mnt)) { |
881 | br_write_unlock(&vfsmount_lock); |
882 | return; |
883 | } |
884 | #else |
885 | mnt_add_count(mnt, -1); |
886 | if (likely(mnt_get_count(mnt))) |
887 | return; |
888 | br_write_lock(&vfsmount_lock); |
889 | #endif |
890 | if (unlikely(mnt->mnt_pinned)) { |
891 | mnt_add_count(mnt, mnt->mnt_pinned + 1); |
892 | mnt->mnt_pinned = 0; |
893 | br_write_unlock(&vfsmount_lock); |
894 | acct_auto_close_mnt(&mnt->mnt); |
895 | goto put_again; |
896 | } |
897 | |
898 | list_del(&mnt->mnt_instance); |
899 | br_write_unlock(&vfsmount_lock); |
900 | mntfree(mnt); |
901 | } |
902 | |
903 | void mntput(struct vfsmount *mnt) |
904 | { |
905 | if (mnt) { |
906 | struct mount *m = real_mount(mnt); |
907 | /* avoid cacheline pingpong, hope gcc doesn't get "smart" */ |
908 | if (unlikely(m->mnt_expiry_mark)) |
909 | m->mnt_expiry_mark = 0; |
910 | mntput_no_expire(m); |
911 | } |
912 | } |
913 | EXPORT_SYMBOL(mntput); |
914 | |
915 | struct vfsmount *mntget(struct vfsmount *mnt) |
916 | { |
917 | if (mnt) |
918 | mnt_add_count(real_mount(mnt), 1); |
919 | return mnt; |
920 | } |
921 | EXPORT_SYMBOL(mntget); |
922 | |
923 | void mnt_pin(struct vfsmount *mnt) |
924 | { |
925 | br_write_lock(&vfsmount_lock); |
926 | real_mount(mnt)->mnt_pinned++; |
927 | br_write_unlock(&vfsmount_lock); |
928 | } |
929 | EXPORT_SYMBOL(mnt_pin); |
930 | |
931 | void mnt_unpin(struct vfsmount *m) |
932 | { |
933 | struct mount *mnt = real_mount(m); |
934 | br_write_lock(&vfsmount_lock); |
935 | if (mnt->mnt_pinned) { |
936 | mnt_add_count(mnt, 1); |
937 | mnt->mnt_pinned--; |
938 | } |
939 | br_write_unlock(&vfsmount_lock); |
940 | } |
941 | EXPORT_SYMBOL(mnt_unpin); |
942 | |
943 | static inline void mangle(struct seq_file *m, const char *s) |
944 | { |
945 | seq_escape(m, s, " \t\n\\"); |
946 | } |
947 | |
948 | /* |
949 | * Simple .show_options callback for filesystems which don't want to |
950 | * implement more complex mount option showing. |
951 | * |
952 | * See also save_mount_options(). |
953 | */ |
954 | int generic_show_options(struct seq_file *m, struct dentry *root) |
955 | { |
956 | const char *options; |
957 | |
958 | rcu_read_lock(); |
959 | options = rcu_dereference(root->d_sb->s_options); |
960 | |
961 | if (options != NULL && options[0]) { |
962 | seq_putc(m, ','); |
963 | mangle(m, options); |
964 | } |
965 | rcu_read_unlock(); |
966 | |
967 | return 0; |
968 | } |
969 | EXPORT_SYMBOL(generic_show_options); |
970 | |
971 | /* |
972 | * If filesystem uses generic_show_options(), this function should be |
973 | * called from the fill_super() callback. |
974 | * |
975 | * The .remount_fs callback usually needs to be handled in a special |
976 | * way, to make sure, that previous options are not overwritten if the |
977 | * remount fails. |
978 | * |
979 | * Also note, that if the filesystem's .remount_fs function doesn't |
980 | * reset all options to their default value, but changes only newly |
981 | * given options, then the displayed options will not reflect reality |
982 | * any more. |
983 | */ |
984 | void save_mount_options(struct super_block *sb, char *options) |
985 | { |
986 | BUG_ON(sb->s_options); |
987 | rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL)); |
988 | } |
989 | EXPORT_SYMBOL(save_mount_options); |
990 | |
991 | void replace_mount_options(struct super_block *sb, char *options) |
992 | { |
993 | char *old = sb->s_options; |
994 | rcu_assign_pointer(sb->s_options, options); |
995 | if (old) { |
996 | synchronize_rcu(); |
997 | kfree(old); |
998 | } |
999 | } |
1000 | EXPORT_SYMBOL(replace_mount_options); |
1001 | |
1002 | #ifdef CONFIG_PROC_FS |
1003 | /* iterator; we want it to have access to namespace_sem, thus here... */ |
1004 | static void *m_start(struct seq_file *m, loff_t *pos) |
1005 | { |
1006 | struct proc_mounts *p = proc_mounts(m); |
1007 | |
1008 | down_read(&namespace_sem); |
1009 | return seq_list_start(&p->ns->list, *pos); |
1010 | } |
1011 | |
1012 | static void *m_next(struct seq_file *m, void *v, loff_t *pos) |
1013 | { |
1014 | struct proc_mounts *p = proc_mounts(m); |
1015 | |
1016 | return seq_list_next(v, &p->ns->list, pos); |
1017 | } |
1018 | |
1019 | static void m_stop(struct seq_file *m, void *v) |
1020 | { |
1021 | up_read(&namespace_sem); |
1022 | } |
1023 | |
1024 | static int m_show(struct seq_file *m, void *v) |
1025 | { |
1026 | struct proc_mounts *p = proc_mounts(m); |
1027 | struct mount *r = list_entry(v, struct mount, mnt_list); |
1028 | return p->show(m, &r->mnt); |
1029 | } |
1030 | |
1031 | const struct seq_operations mounts_op = { |
1032 | .start = m_start, |
1033 | .next = m_next, |
1034 | .stop = m_stop, |
1035 | .show = m_show, |
1036 | }; |
1037 | #endif /* CONFIG_PROC_FS */ |
1038 | |
1039 | /** |
1040 | * may_umount_tree - check if a mount tree is busy |
1041 | * @mnt: root of mount tree |
1042 | * |
1043 | * This is called to check if a tree of mounts has any |
1044 | * open files, pwds, chroots or sub mounts that are |
1045 | * busy. |
1046 | */ |
1047 | int may_umount_tree(struct vfsmount *m) |
1048 | { |
1049 | struct mount *mnt = real_mount(m); |
1050 | int actual_refs = 0; |
1051 | int minimum_refs = 0; |
1052 | struct mount *p; |
1053 | BUG_ON(!m); |
1054 | |
1055 | /* write lock needed for mnt_get_count */ |
1056 | br_write_lock(&vfsmount_lock); |
1057 | for (p = mnt; p; p = next_mnt(p, mnt)) { |
1058 | actual_refs += mnt_get_count(p); |
1059 | minimum_refs += 2; |
1060 | } |
1061 | br_write_unlock(&vfsmount_lock); |
1062 | |
1063 | if (actual_refs > minimum_refs) |
1064 | return 0; |
1065 | |
1066 | return 1; |
1067 | } |
1068 | |
1069 | EXPORT_SYMBOL(may_umount_tree); |
1070 | |
1071 | /** |
1072 | * may_umount - check if a mount point is busy |
1073 | * @mnt: root of mount |
1074 | * |
1075 | * This is called to check if a mount point has any |
1076 | * open files, pwds, chroots or sub mounts. If the |
1077 | * mount has sub mounts this will return busy |
1078 | * regardless of whether the sub mounts are busy. |
1079 | * |
1080 | * Doesn't take quota and stuff into account. IOW, in some cases it will |
1081 | * give false negatives. The main reason why it's here is that we need |
1082 | * a non-destructive way to look for easily umountable filesystems. |
1083 | */ |
1084 | int may_umount(struct vfsmount *mnt) |
1085 | { |
1086 | int ret = 1; |
1087 | down_read(&namespace_sem); |
1088 | br_write_lock(&vfsmount_lock); |
1089 | if (propagate_mount_busy(real_mount(mnt), 2)) |
1090 | ret = 0; |
1091 | br_write_unlock(&vfsmount_lock); |
1092 | up_read(&namespace_sem); |
1093 | return ret; |
1094 | } |
1095 | |
1096 | EXPORT_SYMBOL(may_umount); |
1097 | |
1098 | void release_mounts(struct list_head *head) |
1099 | { |
1100 | struct mount *mnt; |
1101 | while (!list_empty(head)) { |
1102 | mnt = list_first_entry(head, struct mount, mnt_hash); |
1103 | list_del_init(&mnt->mnt_hash); |
1104 | if (mnt_has_parent(mnt)) { |
1105 | struct dentry *dentry; |
1106 | struct mount *m; |
1107 | |
1108 | br_write_lock(&vfsmount_lock); |
1109 | dentry = mnt->mnt_mountpoint; |
1110 | m = mnt->mnt_parent; |
1111 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
1112 | mnt->mnt_parent = mnt; |
1113 | m->mnt_ghosts--; |
1114 | br_write_unlock(&vfsmount_lock); |
1115 | dput(dentry); |
1116 | mntput(&m->mnt); |
1117 | } |
1118 | mntput(&mnt->mnt); |
1119 | } |
1120 | } |
1121 | |
1122 | /* |
1123 | * vfsmount lock must be held for write |
1124 | * namespace_sem must be held for write |
1125 | */ |
1126 | void umount_tree(struct mount *mnt, int propagate, struct list_head *kill) |
1127 | { |
1128 | LIST_HEAD(tmp_list); |
1129 | struct mount *p; |
1130 | |
1131 | for (p = mnt; p; p = next_mnt(p, mnt)) |
1132 | list_move(&p->mnt_hash, &tmp_list); |
1133 | |
1134 | if (propagate) |
1135 | propagate_umount(&tmp_list); |
1136 | |
1137 | list_for_each_entry(p, &tmp_list, mnt_hash) { |
1138 | list_del_init(&p->mnt_expire); |
1139 | list_del_init(&p->mnt_list); |
1140 | __touch_mnt_namespace(p->mnt_ns); |
1141 | p->mnt_ns = NULL; |
1142 | list_del_init(&p->mnt_child); |
1143 | if (mnt_has_parent(p)) { |
1144 | p->mnt_parent->mnt_ghosts++; |
1145 | dentry_reset_mounted(p->mnt_mountpoint); |
1146 | } |
1147 | change_mnt_propagation(p, MS_PRIVATE); |
1148 | } |
1149 | list_splice(&tmp_list, kill); |
1150 | } |
1151 | |
1152 | static void shrink_submounts(struct mount *mnt, struct list_head *umounts); |
1153 | |
1154 | static int do_umount(struct mount *mnt, int flags) |
1155 | { |
1156 | struct super_block *sb = mnt->mnt.mnt_sb; |
1157 | int retval; |
1158 | LIST_HEAD(umount_list); |
1159 | |
1160 | retval = security_sb_umount(&mnt->mnt, flags); |
1161 | if (retval) |
1162 | return retval; |
1163 | |
1164 | /* |
1165 | * Allow userspace to request a mountpoint be expired rather than |
1166 | * unmounting unconditionally. Unmount only happens if: |
1167 | * (1) the mark is already set (the mark is cleared by mntput()) |
1168 | * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] |
1169 | */ |
1170 | if (flags & MNT_EXPIRE) { |
1171 | if (&mnt->mnt == current->fs->root.mnt || |
1172 | flags & (MNT_FORCE | MNT_DETACH)) |
1173 | return -EINVAL; |
1174 | |
1175 | /* |
1176 | * probably don't strictly need the lock here if we examined |
1177 | * all race cases, but it's a slowpath. |
1178 | */ |
1179 | br_write_lock(&vfsmount_lock); |
1180 | if (mnt_get_count(mnt) != 2) { |
1181 | br_write_unlock(&vfsmount_lock); |
1182 | return -EBUSY; |
1183 | } |
1184 | br_write_unlock(&vfsmount_lock); |
1185 | |
1186 | if (!xchg(&mnt->mnt_expiry_mark, 1)) |
1187 | return -EAGAIN; |
1188 | } |
1189 | |
1190 | /* |
1191 | * If we may have to abort operations to get out of this |
1192 | * mount, and they will themselves hold resources we must |
1193 | * allow the fs to do things. In the Unix tradition of |
1194 | * 'Gee thats tricky lets do it in userspace' the umount_begin |
1195 | * might fail to complete on the first run through as other tasks |
1196 | * must return, and the like. Thats for the mount program to worry |
1197 | * about for the moment. |
1198 | */ |
1199 | |
1200 | if (flags & MNT_FORCE && sb->s_op->umount_begin) { |
1201 | sb->s_op->umount_begin(sb); |
1202 | } |
1203 | |
1204 | /* |
1205 | * No sense to grab the lock for this test, but test itself looks |
1206 | * somewhat bogus. Suggestions for better replacement? |
1207 | * Ho-hum... In principle, we might treat that as umount + switch |
1208 | * to rootfs. GC would eventually take care of the old vfsmount. |
1209 | * Actually it makes sense, especially if rootfs would contain a |
1210 | * /reboot - static binary that would close all descriptors and |
1211 | * call reboot(9). Then init(8) could umount root and exec /reboot. |
1212 | */ |
1213 | if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { |
1214 | /* |
1215 | * Special case for "unmounting" root ... |
1216 | * we just try to remount it readonly. |
1217 | */ |
1218 | down_write(&sb->s_umount); |
1219 | if (!(sb->s_flags & MS_RDONLY)) |
1220 | retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); |
1221 | up_write(&sb->s_umount); |
1222 | return retval; |
1223 | } |
1224 | |
1225 | down_write(&namespace_sem); |
1226 | br_write_lock(&vfsmount_lock); |
1227 | event++; |
1228 | |
1229 | if (!(flags & MNT_DETACH)) |
1230 | shrink_submounts(mnt, &umount_list); |
1231 | |
1232 | retval = -EBUSY; |
1233 | if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) { |
1234 | if (!list_empty(&mnt->mnt_list)) |
1235 | umount_tree(mnt, 1, &umount_list); |
1236 | retval = 0; |
1237 | } |
1238 | br_write_unlock(&vfsmount_lock); |
1239 | up_write(&namespace_sem); |
1240 | release_mounts(&umount_list); |
1241 | return retval; |
1242 | } |
1243 | |
1244 | /* |
1245 | * Is the caller allowed to modify his namespace? |
1246 | */ |
1247 | static inline bool may_mount(void) |
1248 | { |
1249 | return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN); |
1250 | } |
1251 | |
1252 | /* |
1253 | * Now umount can handle mount points as well as block devices. |
1254 | * This is important for filesystems which use unnamed block devices. |
1255 | * |
1256 | * We now support a flag for forced unmount like the other 'big iron' |
1257 | * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD |
1258 | */ |
1259 | |
1260 | SYSCALL_DEFINE2(umount, char __user *, name, int, flags) |
1261 | { |
1262 | struct path path; |
1263 | struct mount *mnt; |
1264 | int retval; |
1265 | int lookup_flags = 0; |
1266 | |
1267 | if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) |
1268 | return -EINVAL; |
1269 | |
1270 | if (!may_mount()) |
1271 | return -EPERM; |
1272 | |
1273 | if (!(flags & UMOUNT_NOFOLLOW)) |
1274 | lookup_flags |= LOOKUP_FOLLOW; |
1275 | |
1276 | retval = user_path_at(AT_FDCWD, name, lookup_flags, &path); |
1277 | if (retval) |
1278 | goto out; |
1279 | mnt = real_mount(path.mnt); |
1280 | retval = -EINVAL; |
1281 | if (path.dentry != path.mnt->mnt_root) |
1282 | goto dput_and_out; |
1283 | if (!check_mnt(mnt)) |
1284 | goto dput_and_out; |
1285 | |
1286 | retval = do_umount(mnt, flags); |
1287 | dput_and_out: |
1288 | /* we mustn't call path_put() as that would clear mnt_expiry_mark */ |
1289 | dput(path.dentry); |
1290 | mntput_no_expire(mnt); |
1291 | out: |
1292 | return retval; |
1293 | } |
1294 | |
1295 | #ifdef __ARCH_WANT_SYS_OLDUMOUNT |
1296 | |
1297 | /* |
1298 | * The 2.0 compatible umount. No flags. |
1299 | */ |
1300 | SYSCALL_DEFINE1(oldumount, char __user *, name) |
1301 | { |
1302 | return sys_umount(name, 0); |
1303 | } |
1304 | |
1305 | #endif |
1306 | |
1307 | static bool mnt_ns_loop(struct path *path) |
1308 | { |
1309 | /* Could bind mounting the mount namespace inode cause a |
1310 | * mount namespace loop? |
1311 | */ |
1312 | struct inode *inode = path->dentry->d_inode; |
1313 | struct proc_inode *ei; |
1314 | struct mnt_namespace *mnt_ns; |
1315 | |
1316 | if (!proc_ns_inode(inode)) |
1317 | return false; |
1318 | |
1319 | ei = PROC_I(inode); |
1320 | if (ei->ns_ops != &mntns_operations) |
1321 | return false; |
1322 | |
1323 | mnt_ns = ei->ns; |
1324 | return current->nsproxy->mnt_ns->seq >= mnt_ns->seq; |
1325 | } |
1326 | |
1327 | struct mount *copy_tree(struct mount *mnt, struct dentry *dentry, |
1328 | int flag) |
1329 | { |
1330 | struct mount *res, *p, *q, *r; |
1331 | struct path path; |
1332 | |
1333 | if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt)) |
1334 | return ERR_PTR(-EINVAL); |
1335 | |
1336 | res = q = clone_mnt(mnt, dentry, flag); |
1337 | if (IS_ERR(q)) |
1338 | return q; |
1339 | |
1340 | q->mnt_mountpoint = mnt->mnt_mountpoint; |
1341 | |
1342 | p = mnt; |
1343 | list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { |
1344 | struct mount *s; |
1345 | if (!is_subdir(r->mnt_mountpoint, dentry)) |
1346 | continue; |
1347 | |
1348 | for (s = r; s; s = next_mnt(s, r)) { |
1349 | if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) { |
1350 | s = skip_mnt_tree(s); |
1351 | continue; |
1352 | } |
1353 | while (p != s->mnt_parent) { |
1354 | p = p->mnt_parent; |
1355 | q = q->mnt_parent; |
1356 | } |
1357 | p = s; |
1358 | path.mnt = &q->mnt; |
1359 | path.dentry = p->mnt_mountpoint; |
1360 | q = clone_mnt(p, p->mnt.mnt_root, flag); |
1361 | if (IS_ERR(q)) |
1362 | goto out; |
1363 | br_write_lock(&vfsmount_lock); |
1364 | list_add_tail(&q->mnt_list, &res->mnt_list); |
1365 | attach_mnt(q, &path); |
1366 | br_write_unlock(&vfsmount_lock); |
1367 | } |
1368 | } |
1369 | return res; |
1370 | out: |
1371 | if (res) { |
1372 | LIST_HEAD(umount_list); |
1373 | br_write_lock(&vfsmount_lock); |
1374 | umount_tree(res, 0, &umount_list); |
1375 | br_write_unlock(&vfsmount_lock); |
1376 | release_mounts(&umount_list); |
1377 | } |
1378 | return q; |
1379 | } |
1380 | |
1381 | /* Caller should check returned pointer for errors */ |
1382 | |
1383 | struct vfsmount *collect_mounts(struct path *path) |
1384 | { |
1385 | struct mount *tree; |
1386 | down_write(&namespace_sem); |
1387 | tree = copy_tree(real_mount(path->mnt), path->dentry, |
1388 | CL_COPY_ALL | CL_PRIVATE); |
1389 | up_write(&namespace_sem); |
1390 | if (IS_ERR(tree)) |
1391 | return NULL; |
1392 | return &tree->mnt; |
1393 | } |
1394 | |
1395 | void drop_collected_mounts(struct vfsmount *mnt) |
1396 | { |
1397 | LIST_HEAD(umount_list); |
1398 | down_write(&namespace_sem); |
1399 | br_write_lock(&vfsmount_lock); |
1400 | umount_tree(real_mount(mnt), 0, &umount_list); |
1401 | br_write_unlock(&vfsmount_lock); |
1402 | up_write(&namespace_sem); |
1403 | release_mounts(&umount_list); |
1404 | } |
1405 | |
1406 | int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, |
1407 | struct vfsmount *root) |
1408 | { |
1409 | struct mount *mnt; |
1410 | int res = f(root, arg); |
1411 | if (res) |
1412 | return res; |
1413 | list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) { |
1414 | res = f(&mnt->mnt, arg); |
1415 | if (res) |
1416 | return res; |
1417 | } |
1418 | return 0; |
1419 | } |
1420 | |
1421 | static void cleanup_group_ids(struct mount *mnt, struct mount *end) |
1422 | { |
1423 | struct mount *p; |
1424 | |
1425 | for (p = mnt; p != end; p = next_mnt(p, mnt)) { |
1426 | if (p->mnt_group_id && !IS_MNT_SHARED(p)) |
1427 | mnt_release_group_id(p); |
1428 | } |
1429 | } |
1430 | |
1431 | static int invent_group_ids(struct mount *mnt, bool recurse) |
1432 | { |
1433 | struct mount *p; |
1434 | |
1435 | for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { |
1436 | if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { |
1437 | int err = mnt_alloc_group_id(p); |
1438 | if (err) { |
1439 | cleanup_group_ids(mnt, p); |
1440 | return err; |
1441 | } |
1442 | } |
1443 | } |
1444 | |
1445 | return 0; |
1446 | } |
1447 | |
1448 | /* |
1449 | * @source_mnt : mount tree to be attached |
1450 | * @nd : place the mount tree @source_mnt is attached |
1451 | * @parent_nd : if non-null, detach the source_mnt from its parent and |
1452 | * store the parent mount and mountpoint dentry. |
1453 | * (done when source_mnt is moved) |
1454 | * |
1455 | * NOTE: in the table below explains the semantics when a source mount |
1456 | * of a given type is attached to a destination mount of a given type. |
1457 | * --------------------------------------------------------------------------- |
1458 | * | BIND MOUNT OPERATION | |
1459 | * |************************************************************************** |
1460 | * | source-->| shared | private | slave | unbindable | |
1461 | * | dest | | | | | |
1462 | * | | | | | | | |
1463 | * | v | | | | | |
1464 | * |************************************************************************** |
1465 | * | shared | shared (++) | shared (+) | shared(+++)| invalid | |
1466 | * | | | | | | |
1467 | * |non-shared| shared (+) | private | slave (*) | invalid | |
1468 | * *************************************************************************** |
1469 | * A bind operation clones the source mount and mounts the clone on the |
1470 | * destination mount. |
1471 | * |
1472 | * (++) the cloned mount is propagated to all the mounts in the propagation |
1473 | * tree of the destination mount and the cloned mount is added to |
1474 | * the peer group of the source mount. |
1475 | * (+) the cloned mount is created under the destination mount and is marked |
1476 | * as shared. The cloned mount is added to the peer group of the source |
1477 | * mount. |
1478 | * (+++) the mount is propagated to all the mounts in the propagation tree |
1479 | * of the destination mount and the cloned mount is made slave |
1480 | * of the same master as that of the source mount. The cloned mount |
1481 | * is marked as 'shared and slave'. |
1482 | * (*) the cloned mount is made a slave of the same master as that of the |
1483 | * source mount. |
1484 | * |
1485 | * --------------------------------------------------------------------------- |
1486 | * | MOVE MOUNT OPERATION | |
1487 | * |************************************************************************** |
1488 | * | source-->| shared | private | slave | unbindable | |
1489 | * | dest | | | | | |
1490 | * | | | | | | | |
1491 | * | v | | | | | |
1492 | * |************************************************************************** |
1493 | * | shared | shared (+) | shared (+) | shared(+++) | invalid | |
1494 | * | | | | | | |
1495 | * |non-shared| shared (+*) | private | slave (*) | unbindable | |
1496 | * *************************************************************************** |
1497 | * |
1498 | * (+) the mount is moved to the destination. And is then propagated to |
1499 | * all the mounts in the propagation tree of the destination mount. |
1500 | * (+*) the mount is moved to the destination. |
1501 | * (+++) the mount is moved to the destination and is then propagated to |
1502 | * all the mounts belonging to the destination mount's propagation tree. |
1503 | * the mount is marked as 'shared and slave'. |
1504 | * (*) the mount continues to be a slave at the new location. |
1505 | * |
1506 | * if the source mount is a tree, the operations explained above is |
1507 | * applied to each mount in the tree. |
1508 | * Must be called without spinlocks held, since this function can sleep |
1509 | * in allocations. |
1510 | */ |
1511 | static int attach_recursive_mnt(struct mount *source_mnt, |
1512 | struct path *path, struct path *parent_path) |
1513 | { |
1514 | LIST_HEAD(tree_list); |
1515 | struct mount *dest_mnt = real_mount(path->mnt); |
1516 | struct dentry *dest_dentry = path->dentry; |
1517 | struct mount *child, *p; |
1518 | int err; |
1519 | |
1520 | if (IS_MNT_SHARED(dest_mnt)) { |
1521 | err = invent_group_ids(source_mnt, true); |
1522 | if (err) |
1523 | goto out; |
1524 | } |
1525 | err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list); |
1526 | if (err) |
1527 | goto out_cleanup_ids; |
1528 | |
1529 | br_write_lock(&vfsmount_lock); |
1530 | |
1531 | if (IS_MNT_SHARED(dest_mnt)) { |
1532 | for (p = source_mnt; p; p = next_mnt(p, source_mnt)) |
1533 | set_mnt_shared(p); |
1534 | } |
1535 | if (parent_path) { |
1536 | detach_mnt(source_mnt, parent_path); |
1537 | attach_mnt(source_mnt, path); |
1538 | touch_mnt_namespace(source_mnt->mnt_ns); |
1539 | } else { |
1540 | mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt); |
1541 | commit_tree(source_mnt); |
1542 | } |
1543 | |
1544 | list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { |
1545 | list_del_init(&child->mnt_hash); |
1546 | commit_tree(child); |
1547 | } |
1548 | br_write_unlock(&vfsmount_lock); |
1549 | |
1550 | return 0; |
1551 | |
1552 | out_cleanup_ids: |
1553 | if (IS_MNT_SHARED(dest_mnt)) |
1554 | cleanup_group_ids(source_mnt, NULL); |
1555 | out: |
1556 | return err; |
1557 | } |
1558 | |
1559 | static int lock_mount(struct path *path) |
1560 | { |
1561 | struct vfsmount *mnt; |
1562 | retry: |
1563 | mutex_lock(&path->dentry->d_inode->i_mutex); |
1564 | if (unlikely(cant_mount(path->dentry))) { |
1565 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
1566 | return -ENOENT; |
1567 | } |
1568 | down_write(&namespace_sem); |
1569 | mnt = lookup_mnt(path); |
1570 | if (likely(!mnt)) |
1571 | return 0; |
1572 | up_write(&namespace_sem); |
1573 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
1574 | path_put(path); |
1575 | path->mnt = mnt; |
1576 | path->dentry = dget(mnt->mnt_root); |
1577 | goto retry; |
1578 | } |
1579 | |
1580 | static void unlock_mount(struct path *path) |
1581 | { |
1582 | up_write(&namespace_sem); |
1583 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
1584 | } |
1585 | |
1586 | static int graft_tree(struct mount *mnt, struct path *path) |
1587 | { |
1588 | if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER) |
1589 | return -EINVAL; |
1590 | |
1591 | if (S_ISDIR(path->dentry->d_inode->i_mode) != |
1592 | S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode)) |
1593 | return -ENOTDIR; |
1594 | |
1595 | if (d_unlinked(path->dentry)) |
1596 | return -ENOENT; |
1597 | |
1598 | return attach_recursive_mnt(mnt, path, NULL); |
1599 | } |
1600 | |
1601 | /* |
1602 | * Sanity check the flags to change_mnt_propagation. |
1603 | */ |
1604 | |
1605 | static int flags_to_propagation_type(int flags) |
1606 | { |
1607 | int type = flags & ~(MS_REC | MS_SILENT); |
1608 | |
1609 | /* Fail if any non-propagation flags are set */ |
1610 | if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
1611 | return 0; |
1612 | /* Only one propagation flag should be set */ |
1613 | if (!is_power_of_2(type)) |
1614 | return 0; |
1615 | return type; |
1616 | } |
1617 | |
1618 | /* |
1619 | * recursively change the type of the mountpoint. |
1620 | */ |
1621 | static int do_change_type(struct path *path, int flag) |
1622 | { |
1623 | struct mount *m; |
1624 | struct mount *mnt = real_mount(path->mnt); |
1625 | int recurse = flag & MS_REC; |
1626 | int type; |
1627 | int err = 0; |
1628 | |
1629 | if (path->dentry != path->mnt->mnt_root) |
1630 | return -EINVAL; |
1631 | |
1632 | type = flags_to_propagation_type(flag); |
1633 | if (!type) |
1634 | return -EINVAL; |
1635 | |
1636 | down_write(&namespace_sem); |
1637 | if (type == MS_SHARED) { |
1638 | err = invent_group_ids(mnt, recurse); |
1639 | if (err) |
1640 | goto out_unlock; |
1641 | } |
1642 | |
1643 | br_write_lock(&vfsmount_lock); |
1644 | for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) |
1645 | change_mnt_propagation(m, type); |
1646 | br_write_unlock(&vfsmount_lock); |
1647 | |
1648 | out_unlock: |
1649 | up_write(&namespace_sem); |
1650 | return err; |
1651 | } |
1652 | |
1653 | /* |
1654 | * do loopback mount. |
1655 | */ |
1656 | static int do_loopback(struct path *path, const char *old_name, |
1657 | int recurse) |
1658 | { |
1659 | LIST_HEAD(umount_list); |
1660 | struct path old_path; |
1661 | struct mount *mnt = NULL, *old; |
1662 | int err; |
1663 | if (!old_name || !*old_name) |
1664 | return -EINVAL; |
1665 | err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); |
1666 | if (err) |
1667 | return err; |
1668 | |
1669 | err = -EINVAL; |
1670 | if (mnt_ns_loop(&old_path)) |
1671 | goto out; |
1672 | |
1673 | err = lock_mount(path); |
1674 | if (err) |
1675 | goto out; |
1676 | |
1677 | old = real_mount(old_path.mnt); |
1678 | |
1679 | err = -EINVAL; |
1680 | if (IS_MNT_UNBINDABLE(old)) |
1681 | goto out2; |
1682 | |
1683 | if (!check_mnt(real_mount(path->mnt)) || !check_mnt(old)) |
1684 | goto out2; |
1685 | |
1686 | if (recurse) |
1687 | mnt = copy_tree(old, old_path.dentry, 0); |
1688 | else |
1689 | mnt = clone_mnt(old, old_path.dentry, 0); |
1690 | |
1691 | if (IS_ERR(mnt)) { |
1692 | err = PTR_ERR(mnt); |
1693 | goto out2; |
1694 | } |
1695 | |
1696 | err = graft_tree(mnt, path); |
1697 | if (err) { |
1698 | br_write_lock(&vfsmount_lock); |
1699 | umount_tree(mnt, 0, &umount_list); |
1700 | br_write_unlock(&vfsmount_lock); |
1701 | } |
1702 | out2: |
1703 | unlock_mount(path); |
1704 | release_mounts(&umount_list); |
1705 | out: |
1706 | path_put(&old_path); |
1707 | return err; |
1708 | } |
1709 | |
1710 | static int change_mount_flags(struct vfsmount *mnt, int ms_flags) |
1711 | { |
1712 | int error = 0; |
1713 | int readonly_request = 0; |
1714 | |
1715 | if (ms_flags & MS_RDONLY) |
1716 | readonly_request = 1; |
1717 | if (readonly_request == __mnt_is_readonly(mnt)) |
1718 | return 0; |
1719 | |
1720 | if (mnt->mnt_flags & MNT_LOCK_READONLY) |
1721 | return -EPERM; |
1722 | |
1723 | if (readonly_request) |
1724 | error = mnt_make_readonly(real_mount(mnt)); |
1725 | else |
1726 | __mnt_unmake_readonly(real_mount(mnt)); |
1727 | return error; |
1728 | } |
1729 | |
1730 | /* |
1731 | * change filesystem flags. dir should be a physical root of filesystem. |
1732 | * If you've mounted a non-root directory somewhere and want to do remount |
1733 | * on it - tough luck. |
1734 | */ |
1735 | static int do_remount(struct path *path, int flags, int mnt_flags, |
1736 | void *data) |
1737 | { |
1738 | int err; |
1739 | struct super_block *sb = path->mnt->mnt_sb; |
1740 | struct mount *mnt = real_mount(path->mnt); |
1741 | |
1742 | if (!check_mnt(mnt)) |
1743 | return -EINVAL; |
1744 | |
1745 | if (path->dentry != path->mnt->mnt_root) |
1746 | return -EINVAL; |
1747 | |
1748 | err = security_sb_remount(sb, data); |
1749 | if (err) |
1750 | return err; |
1751 | |
1752 | down_write(&sb->s_umount); |
1753 | if (flags & MS_BIND) |
1754 | err = change_mount_flags(path->mnt, flags); |
1755 | else if (!capable(CAP_SYS_ADMIN)) |
1756 | err = -EPERM; |
1757 | else |
1758 | err = do_remount_sb(sb, flags, data, 0); |
1759 | if (!err) { |
1760 | br_write_lock(&vfsmount_lock); |
1761 | mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK; |
1762 | mnt->mnt.mnt_flags = mnt_flags; |
1763 | br_write_unlock(&vfsmount_lock); |
1764 | } |
1765 | up_write(&sb->s_umount); |
1766 | if (!err) { |
1767 | br_write_lock(&vfsmount_lock); |
1768 | touch_mnt_namespace(mnt->mnt_ns); |
1769 | br_write_unlock(&vfsmount_lock); |
1770 | } |
1771 | return err; |
1772 | } |
1773 | |
1774 | static inline int tree_contains_unbindable(struct mount *mnt) |
1775 | { |
1776 | struct mount *p; |
1777 | for (p = mnt; p; p = next_mnt(p, mnt)) { |
1778 | if (IS_MNT_UNBINDABLE(p)) |
1779 | return 1; |
1780 | } |
1781 | return 0; |
1782 | } |
1783 | |
1784 | static int do_move_mount(struct path *path, const char *old_name) |
1785 | { |
1786 | struct path old_path, parent_path; |
1787 | struct mount *p; |
1788 | struct mount *old; |
1789 | int err; |
1790 | if (!old_name || !*old_name) |
1791 | return -EINVAL; |
1792 | err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); |
1793 | if (err) |
1794 | return err; |
1795 | |
1796 | err = lock_mount(path); |
1797 | if (err < 0) |
1798 | goto out; |
1799 | |
1800 | old = real_mount(old_path.mnt); |
1801 | p = real_mount(path->mnt); |
1802 | |
1803 | err = -EINVAL; |
1804 | if (!check_mnt(p) || !check_mnt(old)) |
1805 | goto out1; |
1806 | |
1807 | if (d_unlinked(path->dentry)) |
1808 | goto out1; |
1809 | |
1810 | err = -EINVAL; |
1811 | if (old_path.dentry != old_path.mnt->mnt_root) |
1812 | goto out1; |
1813 | |
1814 | if (!mnt_has_parent(old)) |
1815 | goto out1; |
1816 | |
1817 | if (S_ISDIR(path->dentry->d_inode->i_mode) != |
1818 | S_ISDIR(old_path.dentry->d_inode->i_mode)) |
1819 | goto out1; |
1820 | /* |
1821 | * Don't move a mount residing in a shared parent. |
1822 | */ |
1823 | if (IS_MNT_SHARED(old->mnt_parent)) |
1824 | goto out1; |
1825 | /* |
1826 | * Don't move a mount tree containing unbindable mounts to a destination |
1827 | * mount which is shared. |
1828 | */ |
1829 | if (IS_MNT_SHARED(p) && tree_contains_unbindable(old)) |
1830 | goto out1; |
1831 | err = -ELOOP; |
1832 | for (; mnt_has_parent(p); p = p->mnt_parent) |
1833 | if (p == old) |
1834 | goto out1; |
1835 | |
1836 | err = attach_recursive_mnt(old, path, &parent_path); |
1837 | if (err) |
1838 | goto out1; |
1839 | |
1840 | /* if the mount is moved, it should no longer be expire |
1841 | * automatically */ |
1842 | list_del_init(&old->mnt_expire); |
1843 | out1: |
1844 | unlock_mount(path); |
1845 | out: |
1846 | if (!err) |
1847 | path_put(&parent_path); |
1848 | path_put(&old_path); |
1849 | return err; |
1850 | } |
1851 | |
1852 | static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype) |
1853 | { |
1854 | int err; |
1855 | const char *subtype = strchr(fstype, '.'); |
1856 | if (subtype) { |
1857 | subtype++; |
1858 | err = -EINVAL; |
1859 | if (!subtype[0]) |
1860 | goto err; |
1861 | } else |
1862 | subtype = ""; |
1863 | |
1864 | mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL); |
1865 | err = -ENOMEM; |
1866 | if (!mnt->mnt_sb->s_subtype) |
1867 | goto err; |
1868 | return mnt; |
1869 | |
1870 | err: |
1871 | mntput(mnt); |
1872 | return ERR_PTR(err); |
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, const char *fstype, int flags, |
1921 | int mnt_flags, const char *name, void *data) |
1922 | { |
1923 | struct file_system_type *type; |
1924 | struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; |
1925 | struct vfsmount *mnt; |
1926 | int err; |
1927 | |
1928 | if (!fstype) |
1929 | return -EINVAL; |
1930 | |
1931 | type = get_fs_type(fstype); |
1932 | if (!type) |
1933 | return -ENODEV; |
1934 | |
1935 | if (user_ns != &init_user_ns) { |
1936 | if (!(type->fs_flags & FS_USERNS_MOUNT)) { |
1937 | put_filesystem(type); |
1938 | return -EPERM; |
1939 | } |
1940 | /* Only in special cases allow devices from mounts |
1941 | * created outside the initial user namespace. |
1942 | */ |
1943 | if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) { |
1944 | flags |= MS_NODEV; |
1945 | mnt_flags |= MNT_NODEV; |
1946 | } |
1947 | } |
1948 | |
1949 | mnt = vfs_kern_mount(type, flags, name, data); |
1950 | if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && |
1951 | !mnt->mnt_sb->s_subtype) |
1952 | mnt = fs_set_subtype(mnt, fstype); |
1953 | |
1954 | put_filesystem(type); |
1955 | if (IS_ERR(mnt)) |
1956 | return PTR_ERR(mnt); |
1957 | |
1958 | err = do_add_mount(real_mount(mnt), path, mnt_flags); |
1959 | if (err) |
1960 | mntput(mnt); |
1961 | return err; |
1962 | } |
1963 | |
1964 | int finish_automount(struct vfsmount *m, struct path *path) |
1965 | { |
1966 | struct mount *mnt = real_mount(m); |
1967 | int err; |
1968 | /* The new mount record should have at least 2 refs to prevent it being |
1969 | * expired before we get a chance to add it |
1970 | */ |
1971 | BUG_ON(mnt_get_count(mnt) < 2); |
1972 | |
1973 | if (m->mnt_sb == path->mnt->mnt_sb && |
1974 | m->mnt_root == path->dentry) { |
1975 | err = -ELOOP; |
1976 | goto fail; |
1977 | } |
1978 | |
1979 | err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE); |
1980 | if (!err) |
1981 | return 0; |
1982 | fail: |
1983 | /* remove m from any expiration list it may be on */ |
1984 | if (!list_empty(&mnt->mnt_expire)) { |
1985 | down_write(&namespace_sem); |
1986 | br_write_lock(&vfsmount_lock); |
1987 | list_del_init(&mnt->mnt_expire); |
1988 | br_write_unlock(&vfsmount_lock); |
1989 | up_write(&namespace_sem); |
1990 | } |
1991 | mntput(m); |
1992 | mntput(m); |
1993 | return err; |
1994 | } |
1995 | |
1996 | /** |
1997 | * mnt_set_expiry - Put a mount on an expiration list |
1998 | * @mnt: The mount to list. |
1999 | * @expiry_list: The list to add the mount to. |
2000 | */ |
2001 | void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list) |
2002 | { |
2003 | down_write(&namespace_sem); |
2004 | br_write_lock(&vfsmount_lock); |
2005 | |
2006 | list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list); |
2007 | |
2008 | br_write_unlock(&vfsmount_lock); |
2009 | up_write(&namespace_sem); |
2010 | } |
2011 | EXPORT_SYMBOL(mnt_set_expiry); |
2012 | |
2013 | /* |
2014 | * process a list of expirable mountpoints with the intent of discarding any |
2015 | * mountpoints that aren't in use and haven't been touched since last we came |
2016 | * here |
2017 | */ |
2018 | void mark_mounts_for_expiry(struct list_head *mounts) |
2019 | { |
2020 | struct mount *mnt, *next; |
2021 | LIST_HEAD(graveyard); |
2022 | LIST_HEAD(umounts); |
2023 | |
2024 | if (list_empty(mounts)) |
2025 | return; |
2026 | |
2027 | down_write(&namespace_sem); |
2028 | br_write_lock(&vfsmount_lock); |
2029 | |
2030 | /* extract from the expiration list every vfsmount that matches the |
2031 | * following criteria: |
2032 | * - only referenced by its parent vfsmount |
2033 | * - still marked for expiry (marked on the last call here; marks are |
2034 | * cleared by mntput()) |
2035 | */ |
2036 | list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { |
2037 | if (!xchg(&mnt->mnt_expiry_mark, 1) || |
2038 | propagate_mount_busy(mnt, 1)) |
2039 | continue; |
2040 | list_move(&mnt->mnt_expire, &graveyard); |
2041 | } |
2042 | while (!list_empty(&graveyard)) { |
2043 | mnt = list_first_entry(&graveyard, struct mount, mnt_expire); |
2044 | touch_mnt_namespace(mnt->mnt_ns); |
2045 | umount_tree(mnt, 1, &umounts); |
2046 | } |
2047 | br_write_unlock(&vfsmount_lock); |
2048 | up_write(&namespace_sem); |
2049 | |
2050 | release_mounts(&umounts); |
2051 | } |
2052 | |
2053 | EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); |
2054 | |
2055 | /* |
2056 | * Ripoff of 'select_parent()' |
2057 | * |
2058 | * search the list of submounts for a given mountpoint, and move any |
2059 | * shrinkable submounts to the 'graveyard' list. |
2060 | */ |
2061 | static int select_submounts(struct mount *parent, struct list_head *graveyard) |
2062 | { |
2063 | struct mount *this_parent = parent; |
2064 | struct list_head *next; |
2065 | int found = 0; |
2066 | |
2067 | repeat: |
2068 | next = this_parent->mnt_mounts.next; |
2069 | resume: |
2070 | while (next != &this_parent->mnt_mounts) { |
2071 | struct list_head *tmp = next; |
2072 | struct mount *mnt = list_entry(tmp, struct mount, mnt_child); |
2073 | |
2074 | next = tmp->next; |
2075 | if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE)) |
2076 | continue; |
2077 | /* |
2078 | * Descend a level if the d_mounts list is non-empty. |
2079 | */ |
2080 | if (!list_empty(&mnt->mnt_mounts)) { |
2081 | this_parent = mnt; |
2082 | goto repeat; |
2083 | } |
2084 | |
2085 | if (!propagate_mount_busy(mnt, 1)) { |
2086 | list_move_tail(&mnt->mnt_expire, graveyard); |
2087 | found++; |
2088 | } |
2089 | } |
2090 | /* |
2091 | * All done at this level ... ascend and resume the search |
2092 | */ |
2093 | if (this_parent != parent) { |
2094 | next = this_parent->mnt_child.next; |
2095 | this_parent = this_parent->mnt_parent; |
2096 | goto resume; |
2097 | } |
2098 | return found; |
2099 | } |
2100 | |
2101 | /* |
2102 | * process a list of expirable mountpoints with the intent of discarding any |
2103 | * submounts of a specific parent mountpoint |
2104 | * |
2105 | * vfsmount_lock must be held for write |
2106 | */ |
2107 | static void shrink_submounts(struct mount *mnt, struct list_head *umounts) |
2108 | { |
2109 | LIST_HEAD(graveyard); |
2110 | struct mount *m; |
2111 | |
2112 | /* extract submounts of 'mountpoint' from the expiration list */ |
2113 | while (select_submounts(mnt, &graveyard)) { |
2114 | while (!list_empty(&graveyard)) { |
2115 | m = list_first_entry(&graveyard, struct mount, |
2116 | mnt_expire); |
2117 | touch_mnt_namespace(m->mnt_ns); |
2118 | umount_tree(m, 1, umounts); |
2119 | } |
2120 | } |
2121 | } |
2122 | |
2123 | /* |
2124 | * Some copy_from_user() implementations do not return the exact number of |
2125 | * bytes remaining to copy on a fault. But copy_mount_options() requires that. |
2126 | * Note that this function differs from copy_from_user() in that it will oops |
2127 | * on bad values of `to', rather than returning a short copy. |
2128 | */ |
2129 | static long exact_copy_from_user(void *to, const void __user * from, |
2130 | unsigned long n) |
2131 | { |
2132 | char *t = to; |
2133 | const char __user *f = from; |
2134 | char c; |
2135 | |
2136 | if (!access_ok(VERIFY_READ, from, n)) |
2137 | return n; |
2138 | |
2139 | while (n) { |
2140 | if (__get_user(c, f)) { |
2141 | memset(t, 0, n); |
2142 | break; |
2143 | } |
2144 | *t++ = c; |
2145 | f++; |
2146 | n--; |
2147 | } |
2148 | return n; |
2149 | } |
2150 | |
2151 | int copy_mount_options(const void __user * data, unsigned long *where) |
2152 | { |
2153 | int i; |
2154 | unsigned long page; |
2155 | unsigned long size; |
2156 | |
2157 | *where = 0; |
2158 | if (!data) |
2159 | return 0; |
2160 | |
2161 | if (!(page = __get_free_page(GFP_KERNEL))) |
2162 | return -ENOMEM; |
2163 | |
2164 | /* We only care that *some* data at the address the user |
2165 | * gave us is valid. Just in case, we'll zero |
2166 | * the remainder of the page. |
2167 | */ |
2168 | /* copy_from_user cannot cross TASK_SIZE ! */ |
2169 | size = TASK_SIZE - (unsigned long)data; |
2170 | if (size > PAGE_SIZE) |
2171 | size = PAGE_SIZE; |
2172 | |
2173 | i = size - exact_copy_from_user((void *)page, data, size); |
2174 | if (!i) { |
2175 | free_page(page); |
2176 | return -EFAULT; |
2177 | } |
2178 | if (i != PAGE_SIZE) |
2179 | memset((char *)page + i, 0, PAGE_SIZE - i); |
2180 | *where = page; |
2181 | return 0; |
2182 | } |
2183 | |
2184 | int copy_mount_string(const void __user *data, char **where) |
2185 | { |
2186 | char *tmp; |
2187 | |
2188 | if (!data) { |
2189 | *where = NULL; |
2190 | return 0; |
2191 | } |
2192 | |
2193 | tmp = strndup_user(data, PAGE_SIZE); |
2194 | if (IS_ERR(tmp)) |
2195 | return PTR_ERR(tmp); |
2196 | |
2197 | *where = tmp; |
2198 | return 0; |
2199 | } |
2200 | |
2201 | /* |
2202 | * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to |
2203 | * be given to the mount() call (ie: read-only, no-dev, no-suid etc). |
2204 | * |
2205 | * data is a (void *) that can point to any structure up to |
2206 | * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent |
2207 | * information (or be NULL). |
2208 | * |
2209 | * Pre-0.97 versions of mount() didn't have a flags word. |
2210 | * When the flags word was introduced its top half was required |
2211 | * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. |
2212 | * Therefore, if this magic number is present, it carries no information |
2213 | * and must be discarded. |
2214 | */ |
2215 | long do_mount(const char *dev_name, const char *dir_name, |
2216 | const char *type_page, unsigned long flags, void *data_page) |
2217 | { |
2218 | struct path path; |
2219 | int retval = 0; |
2220 | int mnt_flags = 0; |
2221 | |
2222 | /* Discard magic */ |
2223 | if ((flags & MS_MGC_MSK) == MS_MGC_VAL) |
2224 | flags &= ~MS_MGC_MSK; |
2225 | |
2226 | /* Basic sanity checks */ |
2227 | |
2228 | if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) |
2229 | return -EINVAL; |
2230 | |
2231 | if (data_page) |
2232 | ((char *)data_page)[PAGE_SIZE - 1] = 0; |
2233 | |
2234 | /* ... and get the mountpoint */ |
2235 | retval = kern_path(dir_name, LOOKUP_FOLLOW, &path); |
2236 | if (retval) |
2237 | return retval; |
2238 | |
2239 | retval = security_sb_mount(dev_name, &path, |
2240 | type_page, flags, data_page); |
2241 | if (retval) |
2242 | goto dput_out; |
2243 | |
2244 | if (!may_mount()) |
2245 | return -EPERM; |
2246 | |
2247 | /* Default to relatime unless overriden */ |
2248 | if (!(flags & MS_NOATIME)) |
2249 | mnt_flags |= MNT_RELATIME; |
2250 | |
2251 | /* Separate the per-mountpoint flags */ |
2252 | if (flags & MS_NOSUID) |
2253 | mnt_flags |= MNT_NOSUID; |
2254 | if (flags & MS_NODEV) |
2255 | mnt_flags |= MNT_NODEV; |
2256 | if (flags & MS_NOEXEC) |
2257 | mnt_flags |= MNT_NOEXEC; |
2258 | if (flags & MS_NOATIME) |
2259 | mnt_flags |= MNT_NOATIME; |
2260 | if (flags & MS_NODIRATIME) |
2261 | mnt_flags |= MNT_NODIRATIME; |
2262 | if (flags & MS_STRICTATIME) |
2263 | mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); |
2264 | if (flags & MS_RDONLY) |
2265 | mnt_flags |= MNT_READONLY; |
2266 | |
2267 | flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN | |
2268 | MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT | |
2269 | MS_STRICTATIME); |
2270 | |
2271 | if (flags & MS_REMOUNT) |
2272 | retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags, |
2273 | data_page); |
2274 | else if (flags & MS_BIND) |
2275 | retval = do_loopback(&path, dev_name, flags & MS_REC); |
2276 | else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
2277 | retval = do_change_type(&path, flags); |
2278 | else if (flags & MS_MOVE) |
2279 | retval = do_move_mount(&path, dev_name); |
2280 | else |
2281 | retval = do_new_mount(&path, type_page, flags, mnt_flags, |
2282 | dev_name, data_page); |
2283 | dput_out: |
2284 | path_put(&path); |
2285 | return retval; |
2286 | } |
2287 | |
2288 | static void free_mnt_ns(struct mnt_namespace *ns) |
2289 | { |
2290 | proc_free_inum(ns->proc_inum); |
2291 | put_user_ns(ns->user_ns); |
2292 | kfree(ns); |
2293 | } |
2294 | |
2295 | /* |
2296 | * Assign a sequence number so we can detect when we attempt to bind |
2297 | * mount a reference to an older mount namespace into the current |
2298 | * mount namespace, preventing reference counting loops. A 64bit |
2299 | * number incrementing at 10Ghz will take 12,427 years to wrap which |
2300 | * is effectively never, so we can ignore the possibility. |
2301 | */ |
2302 | static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1); |
2303 | |
2304 | static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns) |
2305 | { |
2306 | struct mnt_namespace *new_ns; |
2307 | int ret; |
2308 | |
2309 | new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); |
2310 | if (!new_ns) |
2311 | return ERR_PTR(-ENOMEM); |
2312 | ret = proc_alloc_inum(&new_ns->proc_inum); |
2313 | if (ret) { |
2314 | kfree(new_ns); |
2315 | return ERR_PTR(ret); |
2316 | } |
2317 | new_ns->seq = atomic64_add_return(1, &mnt_ns_seq); |
2318 | atomic_set(&new_ns->count, 1); |
2319 | new_ns->root = NULL; |
2320 | INIT_LIST_HEAD(&new_ns->list); |
2321 | init_waitqueue_head(&new_ns->poll); |
2322 | new_ns->event = 0; |
2323 | new_ns->user_ns = get_user_ns(user_ns); |
2324 | return new_ns; |
2325 | } |
2326 | |
2327 | /* |
2328 | * Allocate a new namespace structure and populate it with contents |
2329 | * copied from the namespace of the passed in task structure. |
2330 | */ |
2331 | static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns, |
2332 | struct user_namespace *user_ns, struct fs_struct *fs) |
2333 | { |
2334 | struct mnt_namespace *new_ns; |
2335 | struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; |
2336 | struct mount *p, *q; |
2337 | struct mount *old = mnt_ns->root; |
2338 | struct mount *new; |
2339 | int copy_flags; |
2340 | |
2341 | new_ns = alloc_mnt_ns(user_ns); |
2342 | if (IS_ERR(new_ns)) |
2343 | return new_ns; |
2344 | |
2345 | down_write(&namespace_sem); |
2346 | /* First pass: copy the tree topology */ |
2347 | copy_flags = CL_COPY_ALL | CL_EXPIRE; |
2348 | if (user_ns != mnt_ns->user_ns) |
2349 | copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED; |
2350 | new = copy_tree(old, old->mnt.mnt_root, copy_flags); |
2351 | if (IS_ERR(new)) { |
2352 | up_write(&namespace_sem); |
2353 | free_mnt_ns(new_ns); |
2354 | return ERR_CAST(new); |
2355 | } |
2356 | new_ns->root = new; |
2357 | br_write_lock(&vfsmount_lock); |
2358 | list_add_tail(&new_ns->list, &new->mnt_list); |
2359 | br_write_unlock(&vfsmount_lock); |
2360 | |
2361 | /* |
2362 | * Second pass: switch the tsk->fs->* elements and mark new vfsmounts |
2363 | * as belonging to new namespace. We have already acquired a private |
2364 | * fs_struct, so tsk->fs->lock is not needed. |
2365 | */ |
2366 | p = old; |
2367 | q = new; |
2368 | while (p) { |
2369 | q->mnt_ns = new_ns; |
2370 | if (fs) { |
2371 | if (&p->mnt == fs->root.mnt) { |
2372 | fs->root.mnt = mntget(&q->mnt); |
2373 | rootmnt = &p->mnt; |
2374 | } |
2375 | if (&p->mnt == fs->pwd.mnt) { |
2376 | fs->pwd.mnt = mntget(&q->mnt); |
2377 | pwdmnt = &p->mnt; |
2378 | } |
2379 | } |
2380 | p = next_mnt(p, old); |
2381 | q = next_mnt(q, new); |
2382 | } |
2383 | up_write(&namespace_sem); |
2384 | |
2385 | if (rootmnt) |
2386 | mntput(rootmnt); |
2387 | if (pwdmnt) |
2388 | mntput(pwdmnt); |
2389 | |
2390 | return new_ns; |
2391 | } |
2392 | |
2393 | struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, |
2394 | struct user_namespace *user_ns, struct fs_struct *new_fs) |
2395 | { |
2396 | struct mnt_namespace *new_ns; |
2397 | |
2398 | BUG_ON(!ns); |
2399 | get_mnt_ns(ns); |
2400 | |
2401 | if (!(flags & CLONE_NEWNS)) |
2402 | return ns; |
2403 | |
2404 | new_ns = dup_mnt_ns(ns, user_ns, new_fs); |
2405 | |
2406 | put_mnt_ns(ns); |
2407 | return new_ns; |
2408 | } |
2409 | |
2410 | /** |
2411 | * create_mnt_ns - creates a private namespace and adds a root filesystem |
2412 | * @mnt: pointer to the new root filesystem mountpoint |
2413 | */ |
2414 | static struct mnt_namespace *create_mnt_ns(struct vfsmount *m) |
2415 | { |
2416 | struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns); |
2417 | if (!IS_ERR(new_ns)) { |
2418 | struct mount *mnt = real_mount(m); |
2419 | mnt->mnt_ns = new_ns; |
2420 | new_ns->root = mnt; |
2421 | list_add(&new_ns->list, &mnt->mnt_list); |
2422 | } else { |
2423 | mntput(m); |
2424 | } |
2425 | return new_ns; |
2426 | } |
2427 | |
2428 | struct dentry *mount_subtree(struct vfsmount *mnt, const char *name) |
2429 | { |
2430 | struct mnt_namespace *ns; |
2431 | struct super_block *s; |
2432 | struct path path; |
2433 | int err; |
2434 | |
2435 | ns = create_mnt_ns(mnt); |
2436 | if (IS_ERR(ns)) |
2437 | return ERR_CAST(ns); |
2438 | |
2439 | err = vfs_path_lookup(mnt->mnt_root, mnt, |
2440 | name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); |
2441 | |
2442 | put_mnt_ns(ns); |
2443 | |
2444 | if (err) |
2445 | return ERR_PTR(err); |
2446 | |
2447 | /* trade a vfsmount reference for active sb one */ |
2448 | s = path.mnt->mnt_sb; |
2449 | atomic_inc(&s->s_active); |
2450 | mntput(path.mnt); |
2451 | /* lock the sucker */ |
2452 | down_write(&s->s_umount); |
2453 | /* ... and return the root of (sub)tree on it */ |
2454 | return path.dentry; |
2455 | } |
2456 | EXPORT_SYMBOL(mount_subtree); |
2457 | |
2458 | SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, |
2459 | char __user *, type, unsigned long, flags, void __user *, data) |
2460 | { |
2461 | int ret; |
2462 | char *kernel_type; |
2463 | struct filename *kernel_dir; |
2464 | char *kernel_dev; |
2465 | unsigned long data_page; |
2466 | |
2467 | ret = copy_mount_string(type, &kernel_type); |
2468 | if (ret < 0) |
2469 | goto out_type; |
2470 | |
2471 | kernel_dir = getname(dir_name); |
2472 | if (IS_ERR(kernel_dir)) { |
2473 | ret = PTR_ERR(kernel_dir); |
2474 | goto out_dir; |
2475 | } |
2476 | |
2477 | ret = copy_mount_string(dev_name, &kernel_dev); |
2478 | if (ret < 0) |
2479 | goto out_dev; |
2480 | |
2481 | ret = copy_mount_options(data, &data_page); |
2482 | if (ret < 0) |
2483 | goto out_data; |
2484 | |
2485 | ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags, |
2486 | (void *) data_page); |
2487 | |
2488 | free_page(data_page); |
2489 | out_data: |
2490 | kfree(kernel_dev); |
2491 | out_dev: |
2492 | putname(kernel_dir); |
2493 | out_dir: |
2494 | kfree(kernel_type); |
2495 | out_type: |
2496 | return ret; |
2497 | } |
2498 | |
2499 | /* |
2500 | * Return true if path is reachable from root |
2501 | * |
2502 | * namespace_sem or vfsmount_lock is held |
2503 | */ |
2504 | bool is_path_reachable(struct mount *mnt, struct dentry *dentry, |
2505 | const struct path *root) |
2506 | { |
2507 | while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) { |
2508 | dentry = mnt->mnt_mountpoint; |
2509 | mnt = mnt->mnt_parent; |
2510 | } |
2511 | return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry); |
2512 | } |
2513 | |
2514 | int path_is_under(struct path *path1, struct path *path2) |
2515 | { |
2516 | int res; |
2517 | br_read_lock(&vfsmount_lock); |
2518 | res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2); |
2519 | br_read_unlock(&vfsmount_lock); |
2520 | return res; |
2521 | } |
2522 | EXPORT_SYMBOL(path_is_under); |
2523 | |
2524 | /* |
2525 | * pivot_root Semantics: |
2526 | * Moves the root file system of the current process to the directory put_old, |
2527 | * makes new_root as the new root file system of the current process, and sets |
2528 | * root/cwd of all processes which had them on the current root to new_root. |
2529 | * |
2530 | * Restrictions: |
2531 | * The new_root and put_old must be directories, and must not be on the |
2532 | * same file system as the current process root. The put_old must be |
2533 | * underneath new_root, i.e. adding a non-zero number of /.. to the string |
2534 | * pointed to by put_old must yield the same directory as new_root. No other |
2535 | * file system may be mounted on put_old. After all, new_root is a mountpoint. |
2536 | * |
2537 | * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. |
2538 | * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives |
2539 | * in this situation. |
2540 | * |
2541 | * Notes: |
2542 | * - we don't move root/cwd if they are not at the root (reason: if something |
2543 | * cared enough to change them, it's probably wrong to force them elsewhere) |
2544 | * - it's okay to pick a root that isn't the root of a file system, e.g. |
2545 | * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, |
2546 | * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root |
2547 | * first. |
2548 | */ |
2549 | SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, |
2550 | const char __user *, put_old) |
2551 | { |
2552 | struct path new, old, parent_path, root_parent, root; |
2553 | struct mount *new_mnt, *root_mnt; |
2554 | int error; |
2555 | |
2556 | if (!may_mount()) |
2557 | return -EPERM; |
2558 | |
2559 | error = user_path_dir(new_root, &new); |
2560 | if (error) |
2561 | goto out0; |
2562 | |
2563 | error = user_path_dir(put_old, &old); |
2564 | if (error) |
2565 | goto out1; |
2566 | |
2567 | error = security_sb_pivotroot(&old, &new); |
2568 | if (error) |
2569 | goto out2; |
2570 | |
2571 | get_fs_root(current->fs, &root); |
2572 | error = lock_mount(&old); |
2573 | if (error) |
2574 | goto out3; |
2575 | |
2576 | error = -EINVAL; |
2577 | new_mnt = real_mount(new.mnt); |
2578 | root_mnt = real_mount(root.mnt); |
2579 | if (IS_MNT_SHARED(real_mount(old.mnt)) || |
2580 | IS_MNT_SHARED(new_mnt->mnt_parent) || |
2581 | IS_MNT_SHARED(root_mnt->mnt_parent)) |
2582 | goto out4; |
2583 | if (!check_mnt(root_mnt) || !check_mnt(new_mnt)) |
2584 | goto out4; |
2585 | error = -ENOENT; |
2586 | if (d_unlinked(new.dentry)) |
2587 | goto out4; |
2588 | if (d_unlinked(old.dentry)) |
2589 | goto out4; |
2590 | error = -EBUSY; |
2591 | if (new.mnt == root.mnt || |
2592 | old.mnt == root.mnt) |
2593 | goto out4; /* loop, on the same file system */ |
2594 | error = -EINVAL; |
2595 | if (root.mnt->mnt_root != root.dentry) |
2596 | goto out4; /* not a mountpoint */ |
2597 | if (!mnt_has_parent(root_mnt)) |
2598 | goto out4; /* not attached */ |
2599 | if (new.mnt->mnt_root != new.dentry) |
2600 | goto out4; /* not a mountpoint */ |
2601 | if (!mnt_has_parent(new_mnt)) |
2602 | goto out4; /* not attached */ |
2603 | /* make sure we can reach put_old from new_root */ |
2604 | if (!is_path_reachable(real_mount(old.mnt), old.dentry, &new)) |
2605 | goto out4; |
2606 | br_write_lock(&vfsmount_lock); |
2607 | detach_mnt(new_mnt, &parent_path); |
2608 | detach_mnt(root_mnt, &root_parent); |
2609 | /* mount old root on put_old */ |
2610 | attach_mnt(root_mnt, &old); |
2611 | /* mount new_root on / */ |
2612 | attach_mnt(new_mnt, &root_parent); |
2613 | touch_mnt_namespace(current->nsproxy->mnt_ns); |
2614 | br_write_unlock(&vfsmount_lock); |
2615 | chroot_fs_refs(&root, &new); |
2616 | error = 0; |
2617 | out4: |
2618 | unlock_mount(&old); |
2619 | if (!error) { |
2620 | path_put(&root_parent); |
2621 | path_put(&parent_path); |
2622 | } |
2623 | out3: |
2624 | path_put(&root); |
2625 | out2: |
2626 | path_put(&old); |
2627 | out1: |
2628 | path_put(&new); |
2629 | out0: |
2630 | return error; |
2631 | } |
2632 | |
2633 | static void __init init_mount_tree(void) |
2634 | { |
2635 | struct vfsmount *mnt; |
2636 | struct mnt_namespace *ns; |
2637 | struct path root; |
2638 | struct file_system_type *type; |
2639 | |
2640 | type = get_fs_type("rootfs"); |
2641 | if (!type) |
2642 | panic("Can't find rootfs type"); |
2643 | mnt = vfs_kern_mount(type, 0, "rootfs", NULL); |
2644 | put_filesystem(type); |
2645 | if (IS_ERR(mnt)) |
2646 | panic("Can't create rootfs"); |
2647 | |
2648 | ns = create_mnt_ns(mnt); |
2649 | if (IS_ERR(ns)) |
2650 | panic("Can't allocate initial namespace"); |
2651 | |
2652 | init_task.nsproxy->mnt_ns = ns; |
2653 | get_mnt_ns(ns); |
2654 | |
2655 | root.mnt = mnt; |
2656 | root.dentry = mnt->mnt_root; |
2657 | |
2658 | set_fs_pwd(current->fs, &root); |
2659 | set_fs_root(current->fs, &root); |
2660 | } |
2661 | |
2662 | void __init mnt_init(void) |
2663 | { |
2664 | unsigned u; |
2665 | int err; |
2666 | |
2667 | init_rwsem(&namespace_sem); |
2668 | |
2669 | mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount), |
2670 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); |
2671 | |
2672 | mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); |
2673 | |
2674 | if (!mount_hashtable) |
2675 | panic("Failed to allocate mount hash table\n"); |
2676 | |
2677 | printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE); |
2678 | |
2679 | for (u = 0; u < HASH_SIZE; u++) |
2680 | INIT_LIST_HEAD(&mount_hashtable[u]); |
2681 | |
2682 | br_lock_init(&vfsmount_lock); |
2683 | |
2684 | err = sysfs_init(); |
2685 | if (err) |
2686 | printk(KERN_WARNING "%s: sysfs_init error: %d\n", |
2687 | __func__, err); |
2688 | fs_kobj = kobject_create_and_add("fs", NULL); |
2689 | if (!fs_kobj) |
2690 | printk(KERN_WARNING "%s: kobj create error\n", __func__); |
2691 | init_rootfs(); |
2692 | init_mount_tree(); |
2693 | } |
2694 | |
2695 | void put_mnt_ns(struct mnt_namespace *ns) |
2696 | { |
2697 | LIST_HEAD(umount_list); |
2698 | |
2699 | if (!atomic_dec_and_test(&ns->count)) |
2700 | return; |
2701 | down_write(&namespace_sem); |
2702 | br_write_lock(&vfsmount_lock); |
2703 | umount_tree(ns->root, 0, &umount_list); |
2704 | br_write_unlock(&vfsmount_lock); |
2705 | up_write(&namespace_sem); |
2706 | release_mounts(&umount_list); |
2707 | free_mnt_ns(ns); |
2708 | } |
2709 | |
2710 | struct vfsmount *kern_mount_data(struct file_system_type *type, void *data) |
2711 | { |
2712 | struct vfsmount *mnt; |
2713 | mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data); |
2714 | if (!IS_ERR(mnt)) { |
2715 | /* |
2716 | * it is a longterm mount, don't release mnt until |
2717 | * we unmount before file sys is unregistered |
2718 | */ |
2719 | real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL; |
2720 | } |
2721 | return mnt; |
2722 | } |
2723 | EXPORT_SYMBOL_GPL(kern_mount_data); |
2724 | |
2725 | void kern_unmount(struct vfsmount *mnt) |
2726 | { |
2727 | /* release long term mount so mount point can be released */ |
2728 | if (!IS_ERR_OR_NULL(mnt)) { |
2729 | br_write_lock(&vfsmount_lock); |
2730 | real_mount(mnt)->mnt_ns = NULL; |
2731 | br_write_unlock(&vfsmount_lock); |
2732 | mntput(mnt); |
2733 | } |
2734 | } |
2735 | EXPORT_SYMBOL(kern_unmount); |
2736 | |
2737 | bool our_mnt(struct vfsmount *mnt) |
2738 | { |
2739 | return check_mnt(real_mount(mnt)); |
2740 | } |
2741 | |
2742 | bool current_chrooted(void) |
2743 | { |
2744 | /* Does the current process have a non-standard root */ |
2745 | struct path ns_root; |
2746 | struct path fs_root; |
2747 | bool chrooted; |
2748 | |
2749 | /* Find the namespace root */ |
2750 | ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt; |
2751 | ns_root.dentry = ns_root.mnt->mnt_root; |
2752 | path_get(&ns_root); |
2753 | while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root)) |
2754 | ; |
2755 | |
2756 | get_fs_root(current->fs, &fs_root); |
2757 | |
2758 | chrooted = !path_equal(&fs_root, &ns_root); |
2759 | |
2760 | path_put(&fs_root); |
2761 | path_put(&ns_root); |
2762 | |
2763 | return chrooted; |
2764 | } |
2765 | |
2766 | void update_mnt_policy(struct user_namespace *userns) |
2767 | { |
2768 | struct mnt_namespace *ns = current->nsproxy->mnt_ns; |
2769 | struct mount *mnt; |
2770 | |
2771 | down_read(&namespace_sem); |
2772 | list_for_each_entry(mnt, &ns->list, mnt_list) { |
2773 | switch (mnt->mnt.mnt_sb->s_magic) { |
2774 | case SYSFS_MAGIC: |
2775 | userns->may_mount_sysfs = true; |
2776 | break; |
2777 | case PROC_SUPER_MAGIC: |
2778 | userns->may_mount_proc = true; |
2779 | break; |
2780 | } |
2781 | if (userns->may_mount_sysfs && userns->may_mount_proc) |
2782 | break; |
2783 | } |
2784 | up_read(&namespace_sem); |
2785 | } |
2786 | |
2787 | static void *mntns_get(struct task_struct *task) |
2788 | { |
2789 | struct mnt_namespace *ns = NULL; |
2790 | struct nsproxy *nsproxy; |
2791 | |
2792 | rcu_read_lock(); |
2793 | nsproxy = task_nsproxy(task); |
2794 | if (nsproxy) { |
2795 | ns = nsproxy->mnt_ns; |
2796 | get_mnt_ns(ns); |
2797 | } |
2798 | rcu_read_unlock(); |
2799 | |
2800 | return ns; |
2801 | } |
2802 | |
2803 | static void mntns_put(void *ns) |
2804 | { |
2805 | put_mnt_ns(ns); |
2806 | } |
2807 | |
2808 | static int mntns_install(struct nsproxy *nsproxy, void *ns) |
2809 | { |
2810 | struct fs_struct *fs = current->fs; |
2811 | struct mnt_namespace *mnt_ns = ns; |
2812 | struct path root; |
2813 | |
2814 | if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) || |
2815 | !nsown_capable(CAP_SYS_CHROOT) || |
2816 | !nsown_capable(CAP_SYS_ADMIN)) |
2817 | return -EPERM; |
2818 | |
2819 | if (fs->users != 1) |
2820 | return -EINVAL; |
2821 | |
2822 | get_mnt_ns(mnt_ns); |
2823 | put_mnt_ns(nsproxy->mnt_ns); |
2824 | nsproxy->mnt_ns = mnt_ns; |
2825 | |
2826 | /* Find the root */ |
2827 | root.mnt = &mnt_ns->root->mnt; |
2828 | root.dentry = mnt_ns->root->mnt.mnt_root; |
2829 | path_get(&root); |
2830 | while(d_mountpoint(root.dentry) && follow_down_one(&root)) |
2831 | ; |
2832 | |
2833 | /* Update the pwd and root */ |
2834 | set_fs_pwd(fs, &root); |
2835 | set_fs_root(fs, &root); |
2836 | |
2837 | path_put(&root); |
2838 | return 0; |
2839 | } |
2840 | |
2841 | static unsigned int mntns_inum(void *ns) |
2842 | { |
2843 | struct mnt_namespace *mnt_ns = ns; |
2844 | return mnt_ns->proc_inum; |
2845 | } |
2846 | |
2847 | const struct proc_ns_operations mntns_operations = { |
2848 | .name = "mnt", |
2849 | .type = CLONE_NEWNS, |
2850 | .get = mntns_get, |
2851 | .put = mntns_put, |
2852 | .install = mntns_install, |
2853 | .inum = mntns_inum, |
2854 | }; |
2855 |
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