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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/init.h> /* init_rootfs */ |
21 | #include <linux/fs_struct.h> /* get_fs_root et.al. */ |
22 | #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */ |
23 | #include <linux/uaccess.h> |
24 | #include <linux/proc_ns.h> |
25 | #include <linux/magic.h> |
26 | #include "pnode.h" |
27 | #include "internal.h" |
28 | |
29 | #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head)) |
30 | #define HASH_SIZE (1UL << HASH_SHIFT) |
31 | |
32 | static int event; |
33 | static DEFINE_IDA(mnt_id_ida); |
34 | static DEFINE_IDA(mnt_group_ida); |
35 | static DEFINE_SPINLOCK(mnt_id_lock); |
36 | static int mnt_id_start = 0; |
37 | static int mnt_group_start = 1; |
38 | |
39 | static struct list_head *mount_hashtable __read_mostly; |
40 | static struct list_head *mountpoint_hashtable __read_mostly; |
41 | static struct kmem_cache *mnt_cache __read_mostly; |
42 | static struct rw_semaphore namespace_sem; |
43 | |
44 | /* /sys/fs */ |
45 | struct kobject *fs_kobj; |
46 | EXPORT_SYMBOL_GPL(fs_kobj); |
47 | |
48 | /* |
49 | * vfsmount lock may be taken for read to prevent changes to the |
50 | * vfsmount hash, ie. during mountpoint lookups or walking back |
51 | * up the tree. |
52 | * |
53 | * It should be taken for write in all cases where the vfsmount |
54 | * tree or hash is modified or when a vfsmount structure is modified. |
55 | */ |
56 | DEFINE_BRLOCK(vfsmount_lock); |
57 | |
58 | static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) |
59 | { |
60 | unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); |
61 | tmp += ((unsigned long)dentry / L1_CACHE_BYTES); |
62 | tmp = tmp + (tmp >> HASH_SHIFT); |
63 | return tmp & (HASH_SIZE - 1); |
64 | } |
65 | |
66 | #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16) |
67 | |
68 | /* |
69 | * allocation is serialized by namespace_sem, but we need the spinlock to |
70 | * serialize with freeing. |
71 | */ |
72 | static int mnt_alloc_id(struct mount *mnt) |
73 | { |
74 | int res; |
75 | |
76 | retry: |
77 | ida_pre_get(&mnt_id_ida, GFP_KERNEL); |
78 | spin_lock(&mnt_id_lock); |
79 | res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id); |
80 | if (!res) |
81 | mnt_id_start = mnt->mnt_id + 1; |
82 | spin_unlock(&mnt_id_lock); |
83 | if (res == -EAGAIN) |
84 | goto retry; |
85 | |
86 | return res; |
87 | } |
88 | |
89 | static void mnt_free_id(struct mount *mnt) |
90 | { |
91 | int id = mnt->mnt_id; |
92 | spin_lock(&mnt_id_lock); |
93 | ida_remove(&mnt_id_ida, id); |
94 | if (mnt_id_start > id) |
95 | mnt_id_start = id; |
96 | spin_unlock(&mnt_id_lock); |
97 | } |
98 | |
99 | /* |
100 | * Allocate a new peer group ID |
101 | * |
102 | * mnt_group_ida is protected by namespace_sem |
103 | */ |
104 | static int mnt_alloc_group_id(struct mount *mnt) |
105 | { |
106 | int res; |
107 | |
108 | if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL)) |
109 | return -ENOMEM; |
110 | |
111 | res = ida_get_new_above(&mnt_group_ida, |
112 | mnt_group_start, |
113 | &mnt->mnt_group_id); |
114 | if (!res) |
115 | mnt_group_start = mnt->mnt_group_id + 1; |
116 | |
117 | return res; |
118 | } |
119 | |
120 | /* |
121 | * Release a peer group ID |
122 | */ |
123 | void mnt_release_group_id(struct mount *mnt) |
124 | { |
125 | int id = mnt->mnt_group_id; |
126 | ida_remove(&mnt_group_ida, id); |
127 | if (mnt_group_start > id) |
128 | mnt_group_start = id; |
129 | mnt->mnt_group_id = 0; |
130 | } |
131 | |
132 | /* |
133 | * vfsmount lock must be held for read |
134 | */ |
135 | static inline void mnt_add_count(struct mount *mnt, int n) |
136 | { |
137 | #ifdef CONFIG_SMP |
138 | this_cpu_add(mnt->mnt_pcp->mnt_count, n); |
139 | #else |
140 | preempt_disable(); |
141 | mnt->mnt_count += n; |
142 | preempt_enable(); |
143 | #endif |
144 | } |
145 | |
146 | /* |
147 | * vfsmount lock must be held for write |
148 | */ |
149 | unsigned int mnt_get_count(struct mount *mnt) |
150 | { |
151 | #ifdef CONFIG_SMP |
152 | unsigned int count = 0; |
153 | int cpu; |
154 | |
155 | for_each_possible_cpu(cpu) { |
156 | count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count; |
157 | } |
158 | |
159 | return count; |
160 | #else |
161 | return mnt->mnt_count; |
162 | #endif |
163 | } |
164 | |
165 | static struct mount *alloc_vfsmnt(const char *name) |
166 | { |
167 | struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); |
168 | if (mnt) { |
169 | int err; |
170 | |
171 | err = mnt_alloc_id(mnt); |
172 | if (err) |
173 | goto out_free_cache; |
174 | |
175 | if (name) { |
176 | mnt->mnt_devname = kstrdup(name, GFP_KERNEL); |
177 | if (!mnt->mnt_devname) |
178 | goto out_free_id; |
179 | } |
180 | |
181 | #ifdef CONFIG_SMP |
182 | mnt->mnt_pcp = alloc_percpu(struct mnt_pcp); |
183 | if (!mnt->mnt_pcp) |
184 | goto out_free_devname; |
185 | |
186 | this_cpu_add(mnt->mnt_pcp->mnt_count, 1); |
187 | #else |
188 | mnt->mnt_count = 1; |
189 | mnt->mnt_writers = 0; |
190 | #endif |
191 | |
192 | INIT_LIST_HEAD(&mnt->mnt_hash); |
193 | INIT_LIST_HEAD(&mnt->mnt_child); |
194 | INIT_LIST_HEAD(&mnt->mnt_mounts); |
195 | INIT_LIST_HEAD(&mnt->mnt_list); |
196 | INIT_LIST_HEAD(&mnt->mnt_expire); |
197 | INIT_LIST_HEAD(&mnt->mnt_share); |
198 | INIT_LIST_HEAD(&mnt->mnt_slave_list); |
199 | INIT_LIST_HEAD(&mnt->mnt_slave); |
200 | #ifdef CONFIG_FSNOTIFY |
201 | INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks); |
202 | #endif |
203 | } |
204 | return mnt; |
205 | |
206 | #ifdef CONFIG_SMP |
207 | out_free_devname: |
208 | kfree(mnt->mnt_devname); |
209 | #endif |
210 | out_free_id: |
211 | mnt_free_id(mnt); |
212 | out_free_cache: |
213 | kmem_cache_free(mnt_cache, mnt); |
214 | return NULL; |
215 | } |
216 | |
217 | /* |
218 | * Most r/o checks on a fs are for operations that take |
219 | * discrete amounts of time, like a write() or unlink(). |
220 | * We must keep track of when those operations start |
221 | * (for permission checks) and when they end, so that |
222 | * we can determine when writes are able to occur to |
223 | * a filesystem. |
224 | */ |
225 | /* |
226 | * __mnt_is_readonly: check whether a mount is read-only |
227 | * @mnt: the mount to check for its write status |
228 | * |
229 | * This shouldn't be used directly ouside of the VFS. |
230 | * It does not guarantee that the filesystem will stay |
231 | * r/w, just that it is right *now*. This can not and |
232 | * should not be used in place of IS_RDONLY(inode). |
233 | * mnt_want/drop_write() will _keep_ the filesystem |
234 | * r/w. |
235 | */ |
236 | int __mnt_is_readonly(struct vfsmount *mnt) |
237 | { |
238 | if (mnt->mnt_flags & MNT_READONLY) |
239 | return 1; |
240 | if (mnt->mnt_sb->s_flags & MS_RDONLY) |
241 | return 1; |
242 | return 0; |
243 | } |
244 | EXPORT_SYMBOL_GPL(__mnt_is_readonly); |
245 | |
246 | static inline void mnt_inc_writers(struct mount *mnt) |
247 | { |
248 | #ifdef CONFIG_SMP |
249 | this_cpu_inc(mnt->mnt_pcp->mnt_writers); |
250 | #else |
251 | mnt->mnt_writers++; |
252 | #endif |
253 | } |
254 | |
255 | static inline void mnt_dec_writers(struct mount *mnt) |
256 | { |
257 | #ifdef CONFIG_SMP |
258 | this_cpu_dec(mnt->mnt_pcp->mnt_writers); |
259 | #else |
260 | mnt->mnt_writers--; |
261 | #endif |
262 | } |
263 | |
264 | static unsigned int mnt_get_writers(struct mount *mnt) |
265 | { |
266 | #ifdef CONFIG_SMP |
267 | unsigned int count = 0; |
268 | int cpu; |
269 | |
270 | for_each_possible_cpu(cpu) { |
271 | count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers; |
272 | } |
273 | |
274 | return count; |
275 | #else |
276 | return mnt->mnt_writers; |
277 | #endif |
278 | } |
279 | |
280 | static int mnt_is_readonly(struct vfsmount *mnt) |
281 | { |
282 | if (mnt->mnt_sb->s_readonly_remount) |
283 | return 1; |
284 | /* Order wrt setting s_flags/s_readonly_remount in do_remount() */ |
285 | smp_rmb(); |
286 | return __mnt_is_readonly(mnt); |
287 | } |
288 | |
289 | /* |
290 | * Most r/o & frozen checks on a fs are for operations that take discrete |
291 | * amounts of time, like a write() or unlink(). We must keep track of when |
292 | * those operations start (for permission checks) and when they end, so that we |
293 | * can determine when writes are able to occur to a filesystem. |
294 | */ |
295 | /** |
296 | * __mnt_want_write - get write access to a mount without freeze protection |
297 | * @m: the mount on which to take a write |
298 | * |
299 | * This tells the low-level filesystem that a write is about to be performed to |
300 | * it, and makes sure that writes are allowed (mnt it read-write) before |
301 | * returning success. This operation does not protect against filesystem being |
302 | * frozen. When the write operation is finished, __mnt_drop_write() must be |
303 | * called. This is effectively a refcount. |
304 | */ |
305 | int __mnt_want_write(struct vfsmount *m) |
306 | { |
307 | struct mount *mnt = real_mount(m); |
308 | int ret = 0; |
309 | |
310 | preempt_disable(); |
311 | mnt_inc_writers(mnt); |
312 | /* |
313 | * The store to mnt_inc_writers must be visible before we pass |
314 | * MNT_WRITE_HOLD loop below, so that the slowpath can see our |
315 | * incremented count after it has set MNT_WRITE_HOLD. |
316 | */ |
317 | smp_mb(); |
318 | while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) |
319 | cpu_relax(); |
320 | /* |
321 | * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will |
322 | * be set to match its requirements. So we must not load that until |
323 | * MNT_WRITE_HOLD is cleared. |
324 | */ |
325 | smp_rmb(); |
326 | if (mnt_is_readonly(m)) { |
327 | mnt_dec_writers(mnt); |
328 | ret = -EROFS; |
329 | } |
330 | preempt_enable(); |
331 | |
332 | return ret; |
333 | } |
334 | |
335 | /** |
336 | * mnt_want_write - get write access to a mount |
337 | * @m: the mount on which to take a write |
338 | * |
339 | * This tells the low-level filesystem that a write is about to be performed to |
340 | * it, and makes sure that writes are allowed (mount is read-write, filesystem |
341 | * is not frozen) before returning success. When the write operation is |
342 | * finished, mnt_drop_write() must be called. This is effectively a refcount. |
343 | */ |
344 | int mnt_want_write(struct vfsmount *m) |
345 | { |
346 | int ret; |
347 | |
348 | sb_start_write(m->mnt_sb); |
349 | ret = __mnt_want_write(m); |
350 | if (ret) |
351 | sb_end_write(m->mnt_sb); |
352 | return ret; |
353 | } |
354 | EXPORT_SYMBOL_GPL(mnt_want_write); |
355 | |
356 | /** |
357 | * mnt_clone_write - get write access to a mount |
358 | * @mnt: the mount on which to take a write |
359 | * |
360 | * This is effectively like mnt_want_write, except |
361 | * it must only be used to take an extra write reference |
362 | * on a mountpoint that we already know has a write reference |
363 | * on it. This allows some optimisation. |
364 | * |
365 | * After finished, mnt_drop_write must be called as usual to |
366 | * drop the reference. |
367 | */ |
368 | int mnt_clone_write(struct vfsmount *mnt) |
369 | { |
370 | /* superblock may be r/o */ |
371 | if (__mnt_is_readonly(mnt)) |
372 | return -EROFS; |
373 | preempt_disable(); |
374 | mnt_inc_writers(real_mount(mnt)); |
375 | preempt_enable(); |
376 | return 0; |
377 | } |
378 | EXPORT_SYMBOL_GPL(mnt_clone_write); |
379 | |
380 | /** |
381 | * __mnt_want_write_file - get write access to a file's mount |
382 | * @file: the file who's mount on which to take a write |
383 | * |
384 | * This is like __mnt_want_write, but it takes a file and can |
385 | * do some optimisations if the file is open for write already |
386 | */ |
387 | int __mnt_want_write_file(struct file *file) |
388 | { |
389 | struct inode *inode = file_inode(file); |
390 | |
391 | if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode)) |
392 | return __mnt_want_write(file->f_path.mnt); |
393 | else |
394 | return mnt_clone_write(file->f_path.mnt); |
395 | } |
396 | |
397 | /** |
398 | * mnt_want_write_file - get write access to a file's mount |
399 | * @file: the file who's mount on which to take a write |
400 | * |
401 | * This is like mnt_want_write, but it takes a file and can |
402 | * do some optimisations if the file is open for write already |
403 | */ |
404 | int mnt_want_write_file(struct file *file) |
405 | { |
406 | int ret; |
407 | |
408 | sb_start_write(file->f_path.mnt->mnt_sb); |
409 | ret = __mnt_want_write_file(file); |
410 | if (ret) |
411 | sb_end_write(file->f_path.mnt->mnt_sb); |
412 | return ret; |
413 | } |
414 | EXPORT_SYMBOL_GPL(mnt_want_write_file); |
415 | |
416 | /** |
417 | * __mnt_drop_write - give up write access to a mount |
418 | * @mnt: the mount on which to give up write access |
419 | * |
420 | * Tells the low-level filesystem that we are done |
421 | * performing writes to it. Must be matched with |
422 | * __mnt_want_write() call above. |
423 | */ |
424 | void __mnt_drop_write(struct vfsmount *mnt) |
425 | { |
426 | preempt_disable(); |
427 | mnt_dec_writers(real_mount(mnt)); |
428 | preempt_enable(); |
429 | } |
430 | |
431 | /** |
432 | * mnt_drop_write - give up write access to a mount |
433 | * @mnt: the mount on which to give up write access |
434 | * |
435 | * Tells the low-level filesystem that we are done performing writes to it and |
436 | * also allows filesystem to be frozen again. Must be matched with |
437 | * mnt_want_write() call above. |
438 | */ |
439 | void mnt_drop_write(struct vfsmount *mnt) |
440 | { |
441 | __mnt_drop_write(mnt); |
442 | sb_end_write(mnt->mnt_sb); |
443 | } |
444 | EXPORT_SYMBOL_GPL(mnt_drop_write); |
445 | |
446 | void __mnt_drop_write_file(struct file *file) |
447 | { |
448 | __mnt_drop_write(file->f_path.mnt); |
449 | } |
450 | |
451 | void mnt_drop_write_file(struct file *file) |
452 | { |
453 | mnt_drop_write(file->f_path.mnt); |
454 | } |
455 | EXPORT_SYMBOL(mnt_drop_write_file); |
456 | |
457 | static int mnt_make_readonly(struct mount *mnt) |
458 | { |
459 | int ret = 0; |
460 | |
461 | br_write_lock(&vfsmount_lock); |
462 | mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; |
463 | /* |
464 | * After storing MNT_WRITE_HOLD, we'll read the counters. This store |
465 | * should be visible before we do. |
466 | */ |
467 | smp_mb(); |
468 | |
469 | /* |
470 | * With writers on hold, if this value is zero, then there are |
471 | * definitely no active writers (although held writers may subsequently |
472 | * increment the count, they'll have to wait, and decrement it after |
473 | * seeing MNT_READONLY). |
474 | * |
475 | * It is OK to have counter incremented on one CPU and decremented on |
476 | * another: the sum will add up correctly. The danger would be when we |
477 | * sum up each counter, if we read a counter before it is incremented, |
478 | * but then read another CPU's count which it has been subsequently |
479 | * decremented from -- we would see more decrements than we should. |
480 | * MNT_WRITE_HOLD protects against this scenario, because |
481 | * mnt_want_write first increments count, then smp_mb, then spins on |
482 | * MNT_WRITE_HOLD, so it can't be decremented by another CPU while |
483 | * we're counting up here. |
484 | */ |
485 | if (mnt_get_writers(mnt) > 0) |
486 | ret = -EBUSY; |
487 | else |
488 | mnt->mnt.mnt_flags |= MNT_READONLY; |
489 | /* |
490 | * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers |
491 | * that become unheld will see MNT_READONLY. |
492 | */ |
493 | smp_wmb(); |
494 | mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; |
495 | br_write_unlock(&vfsmount_lock); |
496 | return ret; |
497 | } |
498 | |
499 | static void __mnt_unmake_readonly(struct mount *mnt) |
500 | { |
501 | br_write_lock(&vfsmount_lock); |
502 | mnt->mnt.mnt_flags &= ~MNT_READONLY; |
503 | br_write_unlock(&vfsmount_lock); |
504 | } |
505 | |
506 | int sb_prepare_remount_readonly(struct super_block *sb) |
507 | { |
508 | struct mount *mnt; |
509 | int err = 0; |
510 | |
511 | /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */ |
512 | if (atomic_long_read(&sb->s_remove_count)) |
513 | return -EBUSY; |
514 | |
515 | br_write_lock(&vfsmount_lock); |
516 | list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { |
517 | if (!(mnt->mnt.mnt_flags & MNT_READONLY)) { |
518 | mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; |
519 | smp_mb(); |
520 | if (mnt_get_writers(mnt) > 0) { |
521 | err = -EBUSY; |
522 | break; |
523 | } |
524 | } |
525 | } |
526 | if (!err && atomic_long_read(&sb->s_remove_count)) |
527 | err = -EBUSY; |
528 | |
529 | if (!err) { |
530 | sb->s_readonly_remount = 1; |
531 | smp_wmb(); |
532 | } |
533 | list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { |
534 | if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD) |
535 | mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; |
536 | } |
537 | br_write_unlock(&vfsmount_lock); |
538 | |
539 | return err; |
540 | } |
541 | |
542 | static void free_vfsmnt(struct mount *mnt) |
543 | { |
544 | kfree(mnt->mnt_devname); |
545 | mnt_free_id(mnt); |
546 | #ifdef CONFIG_SMP |
547 | free_percpu(mnt->mnt_pcp); |
548 | #endif |
549 | kmem_cache_free(mnt_cache, mnt); |
550 | } |
551 | |
552 | /* |
553 | * find the first or last mount at @dentry on vfsmount @mnt depending on |
554 | * @dir. If @dir is set return the first mount else return the last mount. |
555 | * vfsmount_lock must be held for read or write. |
556 | */ |
557 | struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry, |
558 | int dir) |
559 | { |
560 | struct list_head *head = mount_hashtable + hash(mnt, dentry); |
561 | struct list_head *tmp = head; |
562 | struct mount *p, *found = NULL; |
563 | |
564 | for (;;) { |
565 | tmp = dir ? tmp->next : tmp->prev; |
566 | p = NULL; |
567 | if (tmp == head) |
568 | break; |
569 | p = list_entry(tmp, struct mount, mnt_hash); |
570 | if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) { |
571 | found = p; |
572 | break; |
573 | } |
574 | } |
575 | return found; |
576 | } |
577 | |
578 | /* |
579 | * lookup_mnt - Return the first child mount mounted at path |
580 | * |
581 | * "First" means first mounted chronologically. If you create the |
582 | * following mounts: |
583 | * |
584 | * mount /dev/sda1 /mnt |
585 | * mount /dev/sda2 /mnt |
586 | * mount /dev/sda3 /mnt |
587 | * |
588 | * Then lookup_mnt() on the base /mnt dentry in the root mount will |
589 | * return successively the root dentry and vfsmount of /dev/sda1, then |
590 | * /dev/sda2, then /dev/sda3, then NULL. |
591 | * |
592 | * lookup_mnt takes a reference to the found vfsmount. |
593 | */ |
594 | struct vfsmount *lookup_mnt(struct path *path) |
595 | { |
596 | struct mount *child_mnt; |
597 | |
598 | br_read_lock(&vfsmount_lock); |
599 | child_mnt = __lookup_mnt(path->mnt, path->dentry, 1); |
600 | if (child_mnt) { |
601 | mnt_add_count(child_mnt, 1); |
602 | br_read_unlock(&vfsmount_lock); |
603 | return &child_mnt->mnt; |
604 | } else { |
605 | br_read_unlock(&vfsmount_lock); |
606 | return NULL; |
607 | } |
608 | } |
609 | |
610 | static struct mountpoint *new_mountpoint(struct dentry *dentry) |
611 | { |
612 | struct list_head *chain = mountpoint_hashtable + hash(NULL, dentry); |
613 | struct mountpoint *mp; |
614 | int ret; |
615 | |
616 | list_for_each_entry(mp, chain, m_hash) { |
617 | if (mp->m_dentry == dentry) { |
618 | /* might be worth a WARN_ON() */ |
619 | if (d_unlinked(dentry)) |
620 | return ERR_PTR(-ENOENT); |
621 | mp->m_count++; |
622 | return mp; |
623 | } |
624 | } |
625 | |
626 | mp = kmalloc(sizeof(struct mountpoint), GFP_KERNEL); |
627 | if (!mp) |
628 | return ERR_PTR(-ENOMEM); |
629 | |
630 | ret = d_set_mounted(dentry); |
631 | if (ret) { |
632 | kfree(mp); |
633 | return ERR_PTR(ret); |
634 | } |
635 | |
636 | mp->m_dentry = dentry; |
637 | mp->m_count = 1; |
638 | list_add(&mp->m_hash, chain); |
639 | return mp; |
640 | } |
641 | |
642 | static void put_mountpoint(struct mountpoint *mp) |
643 | { |
644 | if (!--mp->m_count) { |
645 | struct dentry *dentry = mp->m_dentry; |
646 | spin_lock(&dentry->d_lock); |
647 | dentry->d_flags &= ~DCACHE_MOUNTED; |
648 | spin_unlock(&dentry->d_lock); |
649 | list_del(&mp->m_hash); |
650 | kfree(mp); |
651 | } |
652 | } |
653 | |
654 | static inline int check_mnt(struct mount *mnt) |
655 | { |
656 | return mnt->mnt_ns == current->nsproxy->mnt_ns; |
657 | } |
658 | |
659 | /* |
660 | * vfsmount lock must be held for write |
661 | */ |
662 | static void touch_mnt_namespace(struct mnt_namespace *ns) |
663 | { |
664 | if (ns) { |
665 | ns->event = ++event; |
666 | wake_up_interruptible(&ns->poll); |
667 | } |
668 | } |
669 | |
670 | /* |
671 | * vfsmount lock must be held for write |
672 | */ |
673 | static void __touch_mnt_namespace(struct mnt_namespace *ns) |
674 | { |
675 | if (ns && ns->event != event) { |
676 | ns->event = event; |
677 | wake_up_interruptible(&ns->poll); |
678 | } |
679 | } |
680 | |
681 | /* |
682 | * vfsmount lock must be held for write |
683 | */ |
684 | static void detach_mnt(struct mount *mnt, struct path *old_path) |
685 | { |
686 | old_path->dentry = mnt->mnt_mountpoint; |
687 | old_path->mnt = &mnt->mnt_parent->mnt; |
688 | mnt->mnt_parent = mnt; |
689 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
690 | list_del_init(&mnt->mnt_child); |
691 | list_del_init(&mnt->mnt_hash); |
692 | put_mountpoint(mnt->mnt_mp); |
693 | mnt->mnt_mp = NULL; |
694 | } |
695 | |
696 | /* |
697 | * vfsmount lock must be held for write |
698 | */ |
699 | void mnt_set_mountpoint(struct mount *mnt, |
700 | struct mountpoint *mp, |
701 | struct mount *child_mnt) |
702 | { |
703 | mp->m_count++; |
704 | mnt_add_count(mnt, 1); /* essentially, that's mntget */ |
705 | child_mnt->mnt_mountpoint = dget(mp->m_dentry); |
706 | child_mnt->mnt_parent = mnt; |
707 | child_mnt->mnt_mp = mp; |
708 | } |
709 | |
710 | /* |
711 | * vfsmount lock must be held for write |
712 | */ |
713 | static void attach_mnt(struct mount *mnt, |
714 | struct mount *parent, |
715 | struct mountpoint *mp) |
716 | { |
717 | mnt_set_mountpoint(parent, mp, mnt); |
718 | list_add_tail(&mnt->mnt_hash, mount_hashtable + |
719 | hash(&parent->mnt, mp->m_dentry)); |
720 | list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); |
721 | } |
722 | |
723 | /* |
724 | * vfsmount lock must be held for write |
725 | */ |
726 | static void commit_tree(struct mount *mnt) |
727 | { |
728 | struct mount *parent = mnt->mnt_parent; |
729 | struct mount *m; |
730 | LIST_HEAD(head); |
731 | struct mnt_namespace *n = parent->mnt_ns; |
732 | |
733 | BUG_ON(parent == mnt); |
734 | |
735 | list_add_tail(&head, &mnt->mnt_list); |
736 | list_for_each_entry(m, &head, mnt_list) |
737 | m->mnt_ns = n; |
738 | |
739 | list_splice(&head, n->list.prev); |
740 | |
741 | list_add_tail(&mnt->mnt_hash, mount_hashtable + |
742 | hash(&parent->mnt, mnt->mnt_mountpoint)); |
743 | list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); |
744 | touch_mnt_namespace(n); |
745 | } |
746 | |
747 | static struct mount *next_mnt(struct mount *p, struct mount *root) |
748 | { |
749 | struct list_head *next = p->mnt_mounts.next; |
750 | if (next == &p->mnt_mounts) { |
751 | while (1) { |
752 | if (p == root) |
753 | return NULL; |
754 | next = p->mnt_child.next; |
755 | if (next != &p->mnt_parent->mnt_mounts) |
756 | break; |
757 | p = p->mnt_parent; |
758 | } |
759 | } |
760 | return list_entry(next, struct mount, mnt_child); |
761 | } |
762 | |
763 | static struct mount *skip_mnt_tree(struct mount *p) |
764 | { |
765 | struct list_head *prev = p->mnt_mounts.prev; |
766 | while (prev != &p->mnt_mounts) { |
767 | p = list_entry(prev, struct mount, mnt_child); |
768 | prev = p->mnt_mounts.prev; |
769 | } |
770 | return p; |
771 | } |
772 | |
773 | struct vfsmount * |
774 | vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data) |
775 | { |
776 | struct mount *mnt; |
777 | struct dentry *root; |
778 | |
779 | if (!type) |
780 | return ERR_PTR(-ENODEV); |
781 | |
782 | mnt = alloc_vfsmnt(name); |
783 | if (!mnt) |
784 | return ERR_PTR(-ENOMEM); |
785 | |
786 | if (flags & MS_KERNMOUNT) |
787 | mnt->mnt.mnt_flags = MNT_INTERNAL; |
788 | |
789 | root = mount_fs(type, flags, name, data); |
790 | if (IS_ERR(root)) { |
791 | free_vfsmnt(mnt); |
792 | return ERR_CAST(root); |
793 | } |
794 | |
795 | mnt->mnt.mnt_root = root; |
796 | mnt->mnt.mnt_sb = root->d_sb; |
797 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
798 | mnt->mnt_parent = mnt; |
799 | br_write_lock(&vfsmount_lock); |
800 | list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts); |
801 | br_write_unlock(&vfsmount_lock); |
802 | return &mnt->mnt; |
803 | } |
804 | EXPORT_SYMBOL_GPL(vfs_kern_mount); |
805 | |
806 | static struct mount *clone_mnt(struct mount *old, struct dentry *root, |
807 | int flag) |
808 | { |
809 | struct super_block *sb = old->mnt.mnt_sb; |
810 | struct mount *mnt; |
811 | int err; |
812 | |
813 | mnt = alloc_vfsmnt(old->mnt_devname); |
814 | if (!mnt) |
815 | return ERR_PTR(-ENOMEM); |
816 | |
817 | if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE)) |
818 | mnt->mnt_group_id = 0; /* not a peer of original */ |
819 | else |
820 | mnt->mnt_group_id = old->mnt_group_id; |
821 | |
822 | if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { |
823 | err = mnt_alloc_group_id(mnt); |
824 | if (err) |
825 | goto out_free; |
826 | } |
827 | |
828 | mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD; |
829 | /* Don't allow unprivileged users to change mount flags */ |
830 | if ((flag & CL_UNPRIVILEGED) && (mnt->mnt.mnt_flags & MNT_READONLY)) |
831 | mnt->mnt.mnt_flags |= MNT_LOCK_READONLY; |
832 | |
833 | /* Don't allow unprivileged users to reveal what is under a mount */ |
834 | if ((flag & CL_UNPRIVILEGED) && list_empty(&old->mnt_expire)) |
835 | mnt->mnt.mnt_flags |= MNT_LOCKED; |
836 | |
837 | atomic_inc(&sb->s_active); |
838 | mnt->mnt.mnt_sb = sb; |
839 | mnt->mnt.mnt_root = dget(root); |
840 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
841 | mnt->mnt_parent = mnt; |
842 | br_write_lock(&vfsmount_lock); |
843 | list_add_tail(&mnt->mnt_instance, &sb->s_mounts); |
844 | br_write_unlock(&vfsmount_lock); |
845 | |
846 | if ((flag & CL_SLAVE) || |
847 | ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) { |
848 | list_add(&mnt->mnt_slave, &old->mnt_slave_list); |
849 | mnt->mnt_master = old; |
850 | CLEAR_MNT_SHARED(mnt); |
851 | } else if (!(flag & CL_PRIVATE)) { |
852 | if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old)) |
853 | list_add(&mnt->mnt_share, &old->mnt_share); |
854 | if (IS_MNT_SLAVE(old)) |
855 | list_add(&mnt->mnt_slave, &old->mnt_slave); |
856 | mnt->mnt_master = old->mnt_master; |
857 | } |
858 | if (flag & CL_MAKE_SHARED) |
859 | set_mnt_shared(mnt); |
860 | |
861 | /* stick the duplicate mount on the same expiry list |
862 | * as the original if that was on one */ |
863 | if (flag & CL_EXPIRE) { |
864 | if (!list_empty(&old->mnt_expire)) |
865 | list_add(&mnt->mnt_expire, &old->mnt_expire); |
866 | } |
867 | |
868 | return mnt; |
869 | |
870 | out_free: |
871 | free_vfsmnt(mnt); |
872 | return ERR_PTR(err); |
873 | } |
874 | |
875 | static inline void mntfree(struct mount *mnt) |
876 | { |
877 | struct vfsmount *m = &mnt->mnt; |
878 | struct super_block *sb = m->mnt_sb; |
879 | |
880 | /* |
881 | * This probably indicates that somebody messed |
882 | * up a mnt_want/drop_write() pair. If this |
883 | * happens, the filesystem was probably unable |
884 | * to make r/w->r/o transitions. |
885 | */ |
886 | /* |
887 | * The locking used to deal with mnt_count decrement provides barriers, |
888 | * so mnt_get_writers() below is safe. |
889 | */ |
890 | WARN_ON(mnt_get_writers(mnt)); |
891 | fsnotify_vfsmount_delete(m); |
892 | dput(m->mnt_root); |
893 | free_vfsmnt(mnt); |
894 | deactivate_super(sb); |
895 | } |
896 | |
897 | static void mntput_no_expire(struct mount *mnt) |
898 | { |
899 | put_again: |
900 | #ifdef CONFIG_SMP |
901 | br_read_lock(&vfsmount_lock); |
902 | if (likely(mnt->mnt_ns)) { |
903 | /* shouldn't be the last one */ |
904 | mnt_add_count(mnt, -1); |
905 | br_read_unlock(&vfsmount_lock); |
906 | return; |
907 | } |
908 | br_read_unlock(&vfsmount_lock); |
909 | |
910 | br_write_lock(&vfsmount_lock); |
911 | mnt_add_count(mnt, -1); |
912 | if (mnt_get_count(mnt)) { |
913 | br_write_unlock(&vfsmount_lock); |
914 | return; |
915 | } |
916 | #else |
917 | mnt_add_count(mnt, -1); |
918 | if (likely(mnt_get_count(mnt))) |
919 | return; |
920 | br_write_lock(&vfsmount_lock); |
921 | #endif |
922 | if (unlikely(mnt->mnt_pinned)) { |
923 | mnt_add_count(mnt, mnt->mnt_pinned + 1); |
924 | mnt->mnt_pinned = 0; |
925 | br_write_unlock(&vfsmount_lock); |
926 | acct_auto_close_mnt(&mnt->mnt); |
927 | goto put_again; |
928 | } |
929 | |
930 | list_del(&mnt->mnt_instance); |
931 | br_write_unlock(&vfsmount_lock); |
932 | mntfree(mnt); |
933 | } |
934 | |
935 | void mntput(struct vfsmount *mnt) |
936 | { |
937 | if (mnt) { |
938 | struct mount *m = real_mount(mnt); |
939 | /* avoid cacheline pingpong, hope gcc doesn't get "smart" */ |
940 | if (unlikely(m->mnt_expiry_mark)) |
941 | m->mnt_expiry_mark = 0; |
942 | mntput_no_expire(m); |
943 | } |
944 | } |
945 | EXPORT_SYMBOL(mntput); |
946 | |
947 | struct vfsmount *mntget(struct vfsmount *mnt) |
948 | { |
949 | if (mnt) |
950 | mnt_add_count(real_mount(mnt), 1); |
951 | return mnt; |
952 | } |
953 | EXPORT_SYMBOL(mntget); |
954 | |
955 | void mnt_pin(struct vfsmount *mnt) |
956 | { |
957 | br_write_lock(&vfsmount_lock); |
958 | real_mount(mnt)->mnt_pinned++; |
959 | br_write_unlock(&vfsmount_lock); |
960 | } |
961 | EXPORT_SYMBOL(mnt_pin); |
962 | |
963 | void mnt_unpin(struct vfsmount *m) |
964 | { |
965 | struct mount *mnt = real_mount(m); |
966 | br_write_lock(&vfsmount_lock); |
967 | if (mnt->mnt_pinned) { |
968 | mnt_add_count(mnt, 1); |
969 | mnt->mnt_pinned--; |
970 | } |
971 | br_write_unlock(&vfsmount_lock); |
972 | } |
973 | EXPORT_SYMBOL(mnt_unpin); |
974 | |
975 | static inline void mangle(struct seq_file *m, const char *s) |
976 | { |
977 | seq_escape(m, s, " \t\n\\"); |
978 | } |
979 | |
980 | /* |
981 | * Simple .show_options callback for filesystems which don't want to |
982 | * implement more complex mount option showing. |
983 | * |
984 | * See also save_mount_options(). |
985 | */ |
986 | int generic_show_options(struct seq_file *m, struct dentry *root) |
987 | { |
988 | const char *options; |
989 | |
990 | rcu_read_lock(); |
991 | options = rcu_dereference(root->d_sb->s_options); |
992 | |
993 | if (options != NULL && options[0]) { |
994 | seq_putc(m, ','); |
995 | mangle(m, options); |
996 | } |
997 | rcu_read_unlock(); |
998 | |
999 | return 0; |
1000 | } |
1001 | EXPORT_SYMBOL(generic_show_options); |
1002 | |
1003 | /* |
1004 | * If filesystem uses generic_show_options(), this function should be |
1005 | * called from the fill_super() callback. |
1006 | * |
1007 | * The .remount_fs callback usually needs to be handled in a special |
1008 | * way, to make sure, that previous options are not overwritten if the |
1009 | * remount fails. |
1010 | * |
1011 | * Also note, that if the filesystem's .remount_fs function doesn't |
1012 | * reset all options to their default value, but changes only newly |
1013 | * given options, then the displayed options will not reflect reality |
1014 | * any more. |
1015 | */ |
1016 | void save_mount_options(struct super_block *sb, char *options) |
1017 | { |
1018 | BUG_ON(sb->s_options); |
1019 | rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL)); |
1020 | } |
1021 | EXPORT_SYMBOL(save_mount_options); |
1022 | |
1023 | void replace_mount_options(struct super_block *sb, char *options) |
1024 | { |
1025 | char *old = sb->s_options; |
1026 | rcu_assign_pointer(sb->s_options, options); |
1027 | if (old) { |
1028 | synchronize_rcu(); |
1029 | kfree(old); |
1030 | } |
1031 | } |
1032 | EXPORT_SYMBOL(replace_mount_options); |
1033 | |
1034 | #ifdef CONFIG_PROC_FS |
1035 | /* iterator; we want it to have access to namespace_sem, thus here... */ |
1036 | static void *m_start(struct seq_file *m, loff_t *pos) |
1037 | { |
1038 | struct proc_mounts *p = proc_mounts(m); |
1039 | |
1040 | down_read(&namespace_sem); |
1041 | return seq_list_start(&p->ns->list, *pos); |
1042 | } |
1043 | |
1044 | static void *m_next(struct seq_file *m, void *v, loff_t *pos) |
1045 | { |
1046 | struct proc_mounts *p = proc_mounts(m); |
1047 | |
1048 | return seq_list_next(v, &p->ns->list, pos); |
1049 | } |
1050 | |
1051 | static void m_stop(struct seq_file *m, void *v) |
1052 | { |
1053 | up_read(&namespace_sem); |
1054 | } |
1055 | |
1056 | static int m_show(struct seq_file *m, void *v) |
1057 | { |
1058 | struct proc_mounts *p = proc_mounts(m); |
1059 | struct mount *r = list_entry(v, struct mount, mnt_list); |
1060 | return p->show(m, &r->mnt); |
1061 | } |
1062 | |
1063 | const struct seq_operations mounts_op = { |
1064 | .start = m_start, |
1065 | .next = m_next, |
1066 | .stop = m_stop, |
1067 | .show = m_show, |
1068 | }; |
1069 | #endif /* CONFIG_PROC_FS */ |
1070 | |
1071 | /** |
1072 | * may_umount_tree - check if a mount tree is busy |
1073 | * @mnt: root of mount tree |
1074 | * |
1075 | * This is called to check if a tree of mounts has any |
1076 | * open files, pwds, chroots or sub mounts that are |
1077 | * busy. |
1078 | */ |
1079 | int may_umount_tree(struct vfsmount *m) |
1080 | { |
1081 | struct mount *mnt = real_mount(m); |
1082 | int actual_refs = 0; |
1083 | int minimum_refs = 0; |
1084 | struct mount *p; |
1085 | BUG_ON(!m); |
1086 | |
1087 | /* write lock needed for mnt_get_count */ |
1088 | br_write_lock(&vfsmount_lock); |
1089 | for (p = mnt; p; p = next_mnt(p, mnt)) { |
1090 | actual_refs += mnt_get_count(p); |
1091 | minimum_refs += 2; |
1092 | } |
1093 | br_write_unlock(&vfsmount_lock); |
1094 | |
1095 | if (actual_refs > minimum_refs) |
1096 | return 0; |
1097 | |
1098 | return 1; |
1099 | } |
1100 | |
1101 | EXPORT_SYMBOL(may_umount_tree); |
1102 | |
1103 | /** |
1104 | * may_umount - check if a mount point is busy |
1105 | * @mnt: root of mount |
1106 | * |
1107 | * This is called to check if a mount point has any |
1108 | * open files, pwds, chroots or sub mounts. If the |
1109 | * mount has sub mounts this will return busy |
1110 | * regardless of whether the sub mounts are busy. |
1111 | * |
1112 | * Doesn't take quota and stuff into account. IOW, in some cases it will |
1113 | * give false negatives. The main reason why it's here is that we need |
1114 | * a non-destructive way to look for easily umountable filesystems. |
1115 | */ |
1116 | int may_umount(struct vfsmount *mnt) |
1117 | { |
1118 | int ret = 1; |
1119 | down_read(&namespace_sem); |
1120 | br_write_lock(&vfsmount_lock); |
1121 | if (propagate_mount_busy(real_mount(mnt), 2)) |
1122 | ret = 0; |
1123 | br_write_unlock(&vfsmount_lock); |
1124 | up_read(&namespace_sem); |
1125 | return ret; |
1126 | } |
1127 | |
1128 | EXPORT_SYMBOL(may_umount); |
1129 | |
1130 | static LIST_HEAD(unmounted); /* protected by namespace_sem */ |
1131 | |
1132 | static void namespace_unlock(void) |
1133 | { |
1134 | struct mount *mnt; |
1135 | LIST_HEAD(head); |
1136 | |
1137 | if (likely(list_empty(&unmounted))) { |
1138 | up_write(&namespace_sem); |
1139 | return; |
1140 | } |
1141 | |
1142 | list_splice_init(&unmounted, &head); |
1143 | up_write(&namespace_sem); |
1144 | |
1145 | while (!list_empty(&head)) { |
1146 | mnt = list_first_entry(&head, struct mount, mnt_hash); |
1147 | list_del_init(&mnt->mnt_hash); |
1148 | if (mnt_has_parent(mnt)) { |
1149 | struct dentry *dentry; |
1150 | struct mount *m; |
1151 | |
1152 | br_write_lock(&vfsmount_lock); |
1153 | dentry = mnt->mnt_mountpoint; |
1154 | m = mnt->mnt_parent; |
1155 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
1156 | mnt->mnt_parent = mnt; |
1157 | m->mnt_ghosts--; |
1158 | br_write_unlock(&vfsmount_lock); |
1159 | dput(dentry); |
1160 | mntput(&m->mnt); |
1161 | } |
1162 | mntput(&mnt->mnt); |
1163 | } |
1164 | } |
1165 | |
1166 | static inline void namespace_lock(void) |
1167 | { |
1168 | down_write(&namespace_sem); |
1169 | } |
1170 | |
1171 | /* |
1172 | * vfsmount lock must be held for write |
1173 | * namespace_sem must be held for write |
1174 | */ |
1175 | void umount_tree(struct mount *mnt, int propagate) |
1176 | { |
1177 | LIST_HEAD(tmp_list); |
1178 | struct mount *p; |
1179 | |
1180 | for (p = mnt; p; p = next_mnt(p, mnt)) |
1181 | list_move(&p->mnt_hash, &tmp_list); |
1182 | |
1183 | if (propagate) |
1184 | propagate_umount(&tmp_list); |
1185 | |
1186 | list_for_each_entry(p, &tmp_list, mnt_hash) { |
1187 | list_del_init(&p->mnt_expire); |
1188 | list_del_init(&p->mnt_list); |
1189 | __touch_mnt_namespace(p->mnt_ns); |
1190 | p->mnt_ns = NULL; |
1191 | list_del_init(&p->mnt_child); |
1192 | if (mnt_has_parent(p)) { |
1193 | p->mnt_parent->mnt_ghosts++; |
1194 | put_mountpoint(p->mnt_mp); |
1195 | p->mnt_mp = NULL; |
1196 | } |
1197 | change_mnt_propagation(p, MS_PRIVATE); |
1198 | } |
1199 | list_splice(&tmp_list, &unmounted); |
1200 | } |
1201 | |
1202 | static void shrink_submounts(struct mount *mnt); |
1203 | |
1204 | static int do_umount(struct mount *mnt, int flags) |
1205 | { |
1206 | struct super_block *sb = mnt->mnt.mnt_sb; |
1207 | int retval; |
1208 | |
1209 | retval = security_sb_umount(&mnt->mnt, flags); |
1210 | if (retval) |
1211 | return retval; |
1212 | |
1213 | /* |
1214 | * Allow userspace to request a mountpoint be expired rather than |
1215 | * unmounting unconditionally. Unmount only happens if: |
1216 | * (1) the mark is already set (the mark is cleared by mntput()) |
1217 | * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] |
1218 | */ |
1219 | if (flags & MNT_EXPIRE) { |
1220 | if (&mnt->mnt == current->fs->root.mnt || |
1221 | flags & (MNT_FORCE | MNT_DETACH)) |
1222 | return -EINVAL; |
1223 | |
1224 | /* |
1225 | * probably don't strictly need the lock here if we examined |
1226 | * all race cases, but it's a slowpath. |
1227 | */ |
1228 | br_write_lock(&vfsmount_lock); |
1229 | if (mnt_get_count(mnt) != 2) { |
1230 | br_write_unlock(&vfsmount_lock); |
1231 | return -EBUSY; |
1232 | } |
1233 | br_write_unlock(&vfsmount_lock); |
1234 | |
1235 | if (!xchg(&mnt->mnt_expiry_mark, 1)) |
1236 | return -EAGAIN; |
1237 | } |
1238 | |
1239 | /* |
1240 | * If we may have to abort operations to get out of this |
1241 | * mount, and they will themselves hold resources we must |
1242 | * allow the fs to do things. In the Unix tradition of |
1243 | * 'Gee thats tricky lets do it in userspace' the umount_begin |
1244 | * might fail to complete on the first run through as other tasks |
1245 | * must return, and the like. Thats for the mount program to worry |
1246 | * about for the moment. |
1247 | */ |
1248 | |
1249 | if (flags & MNT_FORCE && sb->s_op->umount_begin) { |
1250 | sb->s_op->umount_begin(sb); |
1251 | } |
1252 | |
1253 | /* |
1254 | * No sense to grab the lock for this test, but test itself looks |
1255 | * somewhat bogus. Suggestions for better replacement? |
1256 | * Ho-hum... In principle, we might treat that as umount + switch |
1257 | * to rootfs. GC would eventually take care of the old vfsmount. |
1258 | * Actually it makes sense, especially if rootfs would contain a |
1259 | * /reboot - static binary that would close all descriptors and |
1260 | * call reboot(9). Then init(8) could umount root and exec /reboot. |
1261 | */ |
1262 | if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { |
1263 | /* |
1264 | * Special case for "unmounting" root ... |
1265 | * we just try to remount it readonly. |
1266 | */ |
1267 | down_write(&sb->s_umount); |
1268 | if (!(sb->s_flags & MS_RDONLY)) |
1269 | retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); |
1270 | up_write(&sb->s_umount); |
1271 | return retval; |
1272 | } |
1273 | |
1274 | namespace_lock(); |
1275 | br_write_lock(&vfsmount_lock); |
1276 | event++; |
1277 | |
1278 | if (!(flags & MNT_DETACH)) |
1279 | shrink_submounts(mnt); |
1280 | |
1281 | retval = -EBUSY; |
1282 | if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) { |
1283 | if (!list_empty(&mnt->mnt_list)) |
1284 | umount_tree(mnt, 1); |
1285 | retval = 0; |
1286 | } |
1287 | br_write_unlock(&vfsmount_lock); |
1288 | namespace_unlock(); |
1289 | return retval; |
1290 | } |
1291 | |
1292 | /* |
1293 | * Is the caller allowed to modify his namespace? |
1294 | */ |
1295 | static inline bool may_mount(void) |
1296 | { |
1297 | return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN); |
1298 | } |
1299 | |
1300 | /* |
1301 | * Now umount can handle mount points as well as block devices. |
1302 | * This is important for filesystems which use unnamed block devices. |
1303 | * |
1304 | * We now support a flag for forced unmount like the other 'big iron' |
1305 | * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD |
1306 | */ |
1307 | |
1308 | SYSCALL_DEFINE2(umount, char __user *, name, int, flags) |
1309 | { |
1310 | struct path path; |
1311 | struct mount *mnt; |
1312 | int retval; |
1313 | int lookup_flags = 0; |
1314 | |
1315 | if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) |
1316 | return -EINVAL; |
1317 | |
1318 | if (!may_mount()) |
1319 | return -EPERM; |
1320 | |
1321 | if (!(flags & UMOUNT_NOFOLLOW)) |
1322 | lookup_flags |= LOOKUP_FOLLOW; |
1323 | |
1324 | retval = user_path_mountpoint_at(AT_FDCWD, name, lookup_flags, &path); |
1325 | if (retval) |
1326 | goto out; |
1327 | mnt = real_mount(path.mnt); |
1328 | retval = -EINVAL; |
1329 | if (path.dentry != path.mnt->mnt_root) |
1330 | goto dput_and_out; |
1331 | if (!check_mnt(mnt)) |
1332 | goto dput_and_out; |
1333 | if (mnt->mnt.mnt_flags & MNT_LOCKED) |
1334 | goto dput_and_out; |
1335 | |
1336 | retval = do_umount(mnt, flags); |
1337 | dput_and_out: |
1338 | /* we mustn't call path_put() as that would clear mnt_expiry_mark */ |
1339 | dput(path.dentry); |
1340 | mntput_no_expire(mnt); |
1341 | out: |
1342 | return retval; |
1343 | } |
1344 | |
1345 | #ifdef __ARCH_WANT_SYS_OLDUMOUNT |
1346 | |
1347 | /* |
1348 | * The 2.0 compatible umount. No flags. |
1349 | */ |
1350 | SYSCALL_DEFINE1(oldumount, char __user *, name) |
1351 | { |
1352 | return sys_umount(name, 0); |
1353 | } |
1354 | |
1355 | #endif |
1356 | |
1357 | static bool is_mnt_ns_file(struct dentry *dentry) |
1358 | { |
1359 | /* Is this a proxy for a mount namespace? */ |
1360 | struct inode *inode = dentry->d_inode; |
1361 | struct proc_ns *ei; |
1362 | |
1363 | if (!proc_ns_inode(inode)) |
1364 | return false; |
1365 | |
1366 | ei = get_proc_ns(inode); |
1367 | if (ei->ns_ops != &mntns_operations) |
1368 | return false; |
1369 | |
1370 | return true; |
1371 | } |
1372 | |
1373 | static bool mnt_ns_loop(struct dentry *dentry) |
1374 | { |
1375 | /* Could bind mounting the mount namespace inode cause a |
1376 | * mount namespace loop? |
1377 | */ |
1378 | struct mnt_namespace *mnt_ns; |
1379 | if (!is_mnt_ns_file(dentry)) |
1380 | return false; |
1381 | |
1382 | mnt_ns = get_proc_ns(dentry->d_inode)->ns; |
1383 | return current->nsproxy->mnt_ns->seq >= mnt_ns->seq; |
1384 | } |
1385 | |
1386 | struct mount *copy_tree(struct mount *mnt, struct dentry *dentry, |
1387 | int flag) |
1388 | { |
1389 | struct mount *res, *p, *q, *r, *parent; |
1390 | |
1391 | if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt)) |
1392 | return ERR_PTR(-EINVAL); |
1393 | |
1394 | if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry)) |
1395 | return ERR_PTR(-EINVAL); |
1396 | |
1397 | res = q = clone_mnt(mnt, dentry, flag); |
1398 | if (IS_ERR(q)) |
1399 | return q; |
1400 | |
1401 | q->mnt.mnt_flags &= ~MNT_LOCKED; |
1402 | q->mnt_mountpoint = mnt->mnt_mountpoint; |
1403 | |
1404 | p = mnt; |
1405 | list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { |
1406 | struct mount *s; |
1407 | if (!is_subdir(r->mnt_mountpoint, dentry)) |
1408 | continue; |
1409 | |
1410 | for (s = r; s; s = next_mnt(s, r)) { |
1411 | if (!(flag & CL_COPY_UNBINDABLE) && |
1412 | IS_MNT_UNBINDABLE(s)) { |
1413 | s = skip_mnt_tree(s); |
1414 | continue; |
1415 | } |
1416 | if (!(flag & CL_COPY_MNT_NS_FILE) && |
1417 | is_mnt_ns_file(s->mnt.mnt_root)) { |
1418 | s = skip_mnt_tree(s); |
1419 | continue; |
1420 | } |
1421 | while (p != s->mnt_parent) { |
1422 | p = p->mnt_parent; |
1423 | q = q->mnt_parent; |
1424 | } |
1425 | p = s; |
1426 | parent = q; |
1427 | q = clone_mnt(p, p->mnt.mnt_root, flag); |
1428 | if (IS_ERR(q)) |
1429 | goto out; |
1430 | br_write_lock(&vfsmount_lock); |
1431 | list_add_tail(&q->mnt_list, &res->mnt_list); |
1432 | attach_mnt(q, parent, p->mnt_mp); |
1433 | br_write_unlock(&vfsmount_lock); |
1434 | } |
1435 | } |
1436 | return res; |
1437 | out: |
1438 | if (res) { |
1439 | br_write_lock(&vfsmount_lock); |
1440 | umount_tree(res, 0); |
1441 | br_write_unlock(&vfsmount_lock); |
1442 | } |
1443 | return q; |
1444 | } |
1445 | |
1446 | /* Caller should check returned pointer for errors */ |
1447 | |
1448 | struct vfsmount *collect_mounts(struct path *path) |
1449 | { |
1450 | struct mount *tree; |
1451 | namespace_lock(); |
1452 | tree = copy_tree(real_mount(path->mnt), path->dentry, |
1453 | CL_COPY_ALL | CL_PRIVATE); |
1454 | namespace_unlock(); |
1455 | if (IS_ERR(tree)) |
1456 | return ERR_CAST(tree); |
1457 | return &tree->mnt; |
1458 | } |
1459 | |
1460 | void drop_collected_mounts(struct vfsmount *mnt) |
1461 | { |
1462 | namespace_lock(); |
1463 | br_write_lock(&vfsmount_lock); |
1464 | umount_tree(real_mount(mnt), 0); |
1465 | br_write_unlock(&vfsmount_lock); |
1466 | namespace_unlock(); |
1467 | } |
1468 | |
1469 | int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, |
1470 | struct vfsmount *root) |
1471 | { |
1472 | struct mount *mnt; |
1473 | int res = f(root, arg); |
1474 | if (res) |
1475 | return res; |
1476 | list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) { |
1477 | res = f(&mnt->mnt, arg); |
1478 | if (res) |
1479 | return res; |
1480 | } |
1481 | return 0; |
1482 | } |
1483 | |
1484 | static void cleanup_group_ids(struct mount *mnt, struct mount *end) |
1485 | { |
1486 | struct mount *p; |
1487 | |
1488 | for (p = mnt; p != end; p = next_mnt(p, mnt)) { |
1489 | if (p->mnt_group_id && !IS_MNT_SHARED(p)) |
1490 | mnt_release_group_id(p); |
1491 | } |
1492 | } |
1493 | |
1494 | static int invent_group_ids(struct mount *mnt, bool recurse) |
1495 | { |
1496 | struct mount *p; |
1497 | |
1498 | for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { |
1499 | if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { |
1500 | int err = mnt_alloc_group_id(p); |
1501 | if (err) { |
1502 | cleanup_group_ids(mnt, p); |
1503 | return err; |
1504 | } |
1505 | } |
1506 | } |
1507 | |
1508 | return 0; |
1509 | } |
1510 | |
1511 | /* |
1512 | * @source_mnt : mount tree to be attached |
1513 | * @nd : place the mount tree @source_mnt is attached |
1514 | * @parent_nd : if non-null, detach the source_mnt from its parent and |
1515 | * store the parent mount and mountpoint dentry. |
1516 | * (done when source_mnt is moved) |
1517 | * |
1518 | * NOTE: in the table below explains the semantics when a source mount |
1519 | * of a given type is attached to a destination mount of a given type. |
1520 | * --------------------------------------------------------------------------- |
1521 | * | BIND MOUNT OPERATION | |
1522 | * |************************************************************************** |
1523 | * | source-->| shared | private | slave | unbindable | |
1524 | * | dest | | | | | |
1525 | * | | | | | | | |
1526 | * | v | | | | | |
1527 | * |************************************************************************** |
1528 | * | shared | shared (++) | shared (+) | shared(+++)| invalid | |
1529 | * | | | | | | |
1530 | * |non-shared| shared (+) | private | slave (*) | invalid | |
1531 | * *************************************************************************** |
1532 | * A bind operation clones the source mount and mounts the clone on the |
1533 | * destination mount. |
1534 | * |
1535 | * (++) the cloned mount is propagated to all the mounts in the propagation |
1536 | * tree of the destination mount and the cloned mount is added to |
1537 | * the peer group of the source mount. |
1538 | * (+) the cloned mount is created under the destination mount and is marked |
1539 | * as shared. The cloned mount is added to the peer group of the source |
1540 | * mount. |
1541 | * (+++) the mount is propagated to all the mounts in the propagation tree |
1542 | * of the destination mount and the cloned mount is made slave |
1543 | * of the same master as that of the source mount. The cloned mount |
1544 | * is marked as 'shared and slave'. |
1545 | * (*) the cloned mount is made a slave of the same master as that of the |
1546 | * source mount. |
1547 | * |
1548 | * --------------------------------------------------------------------------- |
1549 | * | MOVE MOUNT OPERATION | |
1550 | * |************************************************************************** |
1551 | * | source-->| shared | private | slave | unbindable | |
1552 | * | dest | | | | | |
1553 | * | | | | | | | |
1554 | * | v | | | | | |
1555 | * |************************************************************************** |
1556 | * | shared | shared (+) | shared (+) | shared(+++) | invalid | |
1557 | * | | | | | | |
1558 | * |non-shared| shared (+*) | private | slave (*) | unbindable | |
1559 | * *************************************************************************** |
1560 | * |
1561 | * (+) the mount is moved to the destination. And is then propagated to |
1562 | * all the mounts in the propagation tree of the destination mount. |
1563 | * (+*) the mount is moved to the destination. |
1564 | * (+++) the mount is moved to the destination and is then propagated to |
1565 | * all the mounts belonging to the destination mount's propagation tree. |
1566 | * the mount is marked as 'shared and slave'. |
1567 | * (*) the mount continues to be a slave at the new location. |
1568 | * |
1569 | * if the source mount is a tree, the operations explained above is |
1570 | * applied to each mount in the tree. |
1571 | * Must be called without spinlocks held, since this function can sleep |
1572 | * in allocations. |
1573 | */ |
1574 | static int attach_recursive_mnt(struct mount *source_mnt, |
1575 | struct mount *dest_mnt, |
1576 | struct mountpoint *dest_mp, |
1577 | struct path *parent_path) |
1578 | { |
1579 | LIST_HEAD(tree_list); |
1580 | struct mount *child, *p; |
1581 | int err; |
1582 | |
1583 | if (IS_MNT_SHARED(dest_mnt)) { |
1584 | err = invent_group_ids(source_mnt, true); |
1585 | if (err) |
1586 | goto out; |
1587 | } |
1588 | err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list); |
1589 | if (err) |
1590 | goto out_cleanup_ids; |
1591 | |
1592 | br_write_lock(&vfsmount_lock); |
1593 | |
1594 | if (IS_MNT_SHARED(dest_mnt)) { |
1595 | for (p = source_mnt; p; p = next_mnt(p, source_mnt)) |
1596 | set_mnt_shared(p); |
1597 | } |
1598 | if (parent_path) { |
1599 | detach_mnt(source_mnt, parent_path); |
1600 | attach_mnt(source_mnt, dest_mnt, dest_mp); |
1601 | touch_mnt_namespace(source_mnt->mnt_ns); |
1602 | } else { |
1603 | mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt); |
1604 | commit_tree(source_mnt); |
1605 | } |
1606 | |
1607 | list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { |
1608 | list_del_init(&child->mnt_hash); |
1609 | commit_tree(child); |
1610 | } |
1611 | br_write_unlock(&vfsmount_lock); |
1612 | |
1613 | return 0; |
1614 | |
1615 | out_cleanup_ids: |
1616 | if (IS_MNT_SHARED(dest_mnt)) |
1617 | cleanup_group_ids(source_mnt, NULL); |
1618 | out: |
1619 | return err; |
1620 | } |
1621 | |
1622 | static struct mountpoint *lock_mount(struct path *path) |
1623 | { |
1624 | struct vfsmount *mnt; |
1625 | struct dentry *dentry = path->dentry; |
1626 | retry: |
1627 | mutex_lock(&dentry->d_inode->i_mutex); |
1628 | if (unlikely(cant_mount(dentry))) { |
1629 | mutex_unlock(&dentry->d_inode->i_mutex); |
1630 | return ERR_PTR(-ENOENT); |
1631 | } |
1632 | namespace_lock(); |
1633 | mnt = lookup_mnt(path); |
1634 | if (likely(!mnt)) { |
1635 | struct mountpoint *mp = new_mountpoint(dentry); |
1636 | if (IS_ERR(mp)) { |
1637 | namespace_unlock(); |
1638 | mutex_unlock(&dentry->d_inode->i_mutex); |
1639 | return mp; |
1640 | } |
1641 | return mp; |
1642 | } |
1643 | namespace_unlock(); |
1644 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
1645 | path_put(path); |
1646 | path->mnt = mnt; |
1647 | dentry = path->dentry = dget(mnt->mnt_root); |
1648 | goto retry; |
1649 | } |
1650 | |
1651 | static void unlock_mount(struct mountpoint *where) |
1652 | { |
1653 | struct dentry *dentry = where->m_dentry; |
1654 | put_mountpoint(where); |
1655 | namespace_unlock(); |
1656 | mutex_unlock(&dentry->d_inode->i_mutex); |
1657 | } |
1658 | |
1659 | static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp) |
1660 | { |
1661 | if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER) |
1662 | return -EINVAL; |
1663 | |
1664 | if (S_ISDIR(mp->m_dentry->d_inode->i_mode) != |
1665 | S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode)) |
1666 | return -ENOTDIR; |
1667 | |
1668 | return attach_recursive_mnt(mnt, p, mp, NULL); |
1669 | } |
1670 | |
1671 | /* |
1672 | * Sanity check the flags to change_mnt_propagation. |
1673 | */ |
1674 | |
1675 | static int flags_to_propagation_type(int flags) |
1676 | { |
1677 | int type = flags & ~(MS_REC | MS_SILENT); |
1678 | |
1679 | /* Fail if any non-propagation flags are set */ |
1680 | if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
1681 | return 0; |
1682 | /* Only one propagation flag should be set */ |
1683 | if (!is_power_of_2(type)) |
1684 | return 0; |
1685 | return type; |
1686 | } |
1687 | |
1688 | /* |
1689 | * recursively change the type of the mountpoint. |
1690 | */ |
1691 | static int do_change_type(struct path *path, int flag) |
1692 | { |
1693 | struct mount *m; |
1694 | struct mount *mnt = real_mount(path->mnt); |
1695 | int recurse = flag & MS_REC; |
1696 | int type; |
1697 | int err = 0; |
1698 | |
1699 | if (path->dentry != path->mnt->mnt_root) |
1700 | return -EINVAL; |
1701 | |
1702 | type = flags_to_propagation_type(flag); |
1703 | if (!type) |
1704 | return -EINVAL; |
1705 | |
1706 | namespace_lock(); |
1707 | if (type == MS_SHARED) { |
1708 | err = invent_group_ids(mnt, recurse); |
1709 | if (err) |
1710 | goto out_unlock; |
1711 | } |
1712 | |
1713 | br_write_lock(&vfsmount_lock); |
1714 | for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) |
1715 | change_mnt_propagation(m, type); |
1716 | br_write_unlock(&vfsmount_lock); |
1717 | |
1718 | out_unlock: |
1719 | namespace_unlock(); |
1720 | return err; |
1721 | } |
1722 | |
1723 | static bool has_locked_children(struct mount *mnt, struct dentry *dentry) |
1724 | { |
1725 | struct mount *child; |
1726 | list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { |
1727 | if (!is_subdir(child->mnt_mountpoint, dentry)) |
1728 | continue; |
1729 | |
1730 | if (child->mnt.mnt_flags & MNT_LOCKED) |
1731 | return true; |
1732 | } |
1733 | return false; |
1734 | } |
1735 | |
1736 | /* |
1737 | * do loopback mount. |
1738 | */ |
1739 | static int do_loopback(struct path *path, const char *old_name, |
1740 | int recurse) |
1741 | { |
1742 | struct path old_path; |
1743 | struct mount *mnt = NULL, *old, *parent; |
1744 | struct mountpoint *mp; |
1745 | int err; |
1746 | if (!old_name || !*old_name) |
1747 | return -EINVAL; |
1748 | err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); |
1749 | if (err) |
1750 | return err; |
1751 | |
1752 | err = -EINVAL; |
1753 | if (mnt_ns_loop(old_path.dentry)) |
1754 | goto out; |
1755 | |
1756 | mp = lock_mount(path); |
1757 | err = PTR_ERR(mp); |
1758 | if (IS_ERR(mp)) |
1759 | goto out; |
1760 | |
1761 | old = real_mount(old_path.mnt); |
1762 | parent = real_mount(path->mnt); |
1763 | |
1764 | err = -EINVAL; |
1765 | if (IS_MNT_UNBINDABLE(old)) |
1766 | goto out2; |
1767 | |
1768 | if (!check_mnt(parent) || !check_mnt(old)) |
1769 | goto out2; |
1770 | |
1771 | if (!recurse && has_locked_children(old, old_path.dentry)) |
1772 | goto out2; |
1773 | |
1774 | if (recurse) |
1775 | mnt = copy_tree(old, old_path.dentry, CL_COPY_MNT_NS_FILE); |
1776 | else |
1777 | mnt = clone_mnt(old, old_path.dentry, 0); |
1778 | |
1779 | if (IS_ERR(mnt)) { |
1780 | err = PTR_ERR(mnt); |
1781 | goto out2; |
1782 | } |
1783 | |
1784 | mnt->mnt.mnt_flags &= ~MNT_LOCKED; |
1785 | |
1786 | err = graft_tree(mnt, parent, mp); |
1787 | if (err) { |
1788 | br_write_lock(&vfsmount_lock); |
1789 | umount_tree(mnt, 0); |
1790 | br_write_unlock(&vfsmount_lock); |
1791 | } |
1792 | out2: |
1793 | unlock_mount(mp); |
1794 | out: |
1795 | path_put(&old_path); |
1796 | return err; |
1797 | } |
1798 | |
1799 | static int change_mount_flags(struct vfsmount *mnt, int ms_flags) |
1800 | { |
1801 | int error = 0; |
1802 | int readonly_request = 0; |
1803 | |
1804 | if (ms_flags & MS_RDONLY) |
1805 | readonly_request = 1; |
1806 | if (readonly_request == __mnt_is_readonly(mnt)) |
1807 | return 0; |
1808 | |
1809 | if (mnt->mnt_flags & MNT_LOCK_READONLY) |
1810 | return -EPERM; |
1811 | |
1812 | if (readonly_request) |
1813 | error = mnt_make_readonly(real_mount(mnt)); |
1814 | else |
1815 | __mnt_unmake_readonly(real_mount(mnt)); |
1816 | return error; |
1817 | } |
1818 | |
1819 | /* |
1820 | * change filesystem flags. dir should be a physical root of filesystem. |
1821 | * If you've mounted a non-root directory somewhere and want to do remount |
1822 | * on it - tough luck. |
1823 | */ |
1824 | static int do_remount(struct path *path, int flags, int mnt_flags, |
1825 | void *data) |
1826 | { |
1827 | int err; |
1828 | struct super_block *sb = path->mnt->mnt_sb; |
1829 | struct mount *mnt = real_mount(path->mnt); |
1830 | |
1831 | if (!check_mnt(mnt)) |
1832 | return -EINVAL; |
1833 | |
1834 | if (path->dentry != path->mnt->mnt_root) |
1835 | return -EINVAL; |
1836 | |
1837 | err = security_sb_remount(sb, data); |
1838 | if (err) |
1839 | return err; |
1840 | |
1841 | down_write(&sb->s_umount); |
1842 | if (flags & MS_BIND) |
1843 | err = change_mount_flags(path->mnt, flags); |
1844 | else if (!capable(CAP_SYS_ADMIN)) |
1845 | err = -EPERM; |
1846 | else |
1847 | err = do_remount_sb(sb, flags, data, 0); |
1848 | if (!err) { |
1849 | br_write_lock(&vfsmount_lock); |
1850 | mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK; |
1851 | mnt->mnt.mnt_flags = mnt_flags; |
1852 | br_write_unlock(&vfsmount_lock); |
1853 | } |
1854 | up_write(&sb->s_umount); |
1855 | if (!err) { |
1856 | br_write_lock(&vfsmount_lock); |
1857 | touch_mnt_namespace(mnt->mnt_ns); |
1858 | br_write_unlock(&vfsmount_lock); |
1859 | } |
1860 | return err; |
1861 | } |
1862 | |
1863 | static inline int tree_contains_unbindable(struct mount *mnt) |
1864 | { |
1865 | struct mount *p; |
1866 | for (p = mnt; p; p = next_mnt(p, mnt)) { |
1867 | if (IS_MNT_UNBINDABLE(p)) |
1868 | return 1; |
1869 | } |
1870 | return 0; |
1871 | } |
1872 | |
1873 | static int do_move_mount(struct path *path, const char *old_name) |
1874 | { |
1875 | struct path old_path, parent_path; |
1876 | struct mount *p; |
1877 | struct mount *old; |
1878 | struct mountpoint *mp; |
1879 | int err; |
1880 | if (!old_name || !*old_name) |
1881 | return -EINVAL; |
1882 | err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); |
1883 | if (err) |
1884 | return err; |
1885 | |
1886 | mp = lock_mount(path); |
1887 | err = PTR_ERR(mp); |
1888 | if (IS_ERR(mp)) |
1889 | goto out; |
1890 | |
1891 | old = real_mount(old_path.mnt); |
1892 | p = real_mount(path->mnt); |
1893 | |
1894 | err = -EINVAL; |
1895 | if (!check_mnt(p) || !check_mnt(old)) |
1896 | goto out1; |
1897 | |
1898 | if (old->mnt.mnt_flags & MNT_LOCKED) |
1899 | goto out1; |
1900 | |
1901 | err = -EINVAL; |
1902 | if (old_path.dentry != old_path.mnt->mnt_root) |
1903 | goto out1; |
1904 | |
1905 | if (!mnt_has_parent(old)) |
1906 | goto out1; |
1907 | |
1908 | if (S_ISDIR(path->dentry->d_inode->i_mode) != |
1909 | S_ISDIR(old_path.dentry->d_inode->i_mode)) |
1910 | goto out1; |
1911 | /* |
1912 | * Don't move a mount residing in a shared parent. |
1913 | */ |
1914 | if (IS_MNT_SHARED(old->mnt_parent)) |
1915 | goto out1; |
1916 | /* |
1917 | * Don't move a mount tree containing unbindable mounts to a destination |
1918 | * mount which is shared. |
1919 | */ |
1920 | if (IS_MNT_SHARED(p) && tree_contains_unbindable(old)) |
1921 | goto out1; |
1922 | err = -ELOOP; |
1923 | for (; mnt_has_parent(p); p = p->mnt_parent) |
1924 | if (p == old) |
1925 | goto out1; |
1926 | |
1927 | err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path); |
1928 | if (err) |
1929 | goto out1; |
1930 | |
1931 | /* if the mount is moved, it should no longer be expire |
1932 | * automatically */ |
1933 | list_del_init(&old->mnt_expire); |
1934 | out1: |
1935 | unlock_mount(mp); |
1936 | out: |
1937 | if (!err) |
1938 | path_put(&parent_path); |
1939 | path_put(&old_path); |
1940 | return err; |
1941 | } |
1942 | |
1943 | static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype) |
1944 | { |
1945 | int err; |
1946 | const char *subtype = strchr(fstype, '.'); |
1947 | if (subtype) { |
1948 | subtype++; |
1949 | err = -EINVAL; |
1950 | if (!subtype[0]) |
1951 | goto err; |
1952 | } else |
1953 | subtype = ""; |
1954 | |
1955 | mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL); |
1956 | err = -ENOMEM; |
1957 | if (!mnt->mnt_sb->s_subtype) |
1958 | goto err; |
1959 | return mnt; |
1960 | |
1961 | err: |
1962 | mntput(mnt); |
1963 | return ERR_PTR(err); |
1964 | } |
1965 | |
1966 | /* |
1967 | * add a mount into a namespace's mount tree |
1968 | */ |
1969 | static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags) |
1970 | { |
1971 | struct mountpoint *mp; |
1972 | struct mount *parent; |
1973 | int err; |
1974 | |
1975 | mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL); |
1976 | |
1977 | mp = lock_mount(path); |
1978 | if (IS_ERR(mp)) |
1979 | return PTR_ERR(mp); |
1980 | |
1981 | parent = real_mount(path->mnt); |
1982 | err = -EINVAL; |
1983 | if (unlikely(!check_mnt(parent))) { |
1984 | /* that's acceptable only for automounts done in private ns */ |
1985 | if (!(mnt_flags & MNT_SHRINKABLE)) |
1986 | goto unlock; |
1987 | /* ... and for those we'd better have mountpoint still alive */ |
1988 | if (!parent->mnt_ns) |
1989 | goto unlock; |
1990 | } |
1991 | |
1992 | /* Refuse the same filesystem on the same mount point */ |
1993 | err = -EBUSY; |
1994 | if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && |
1995 | path->mnt->mnt_root == path->dentry) |
1996 | goto unlock; |
1997 | |
1998 | err = -EINVAL; |
1999 | if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode)) |
2000 | goto unlock; |
2001 | |
2002 | newmnt->mnt.mnt_flags = mnt_flags; |
2003 | err = graft_tree(newmnt, parent, mp); |
2004 | |
2005 | unlock: |
2006 | unlock_mount(mp); |
2007 | return err; |
2008 | } |
2009 | |
2010 | /* |
2011 | * create a new mount for userspace and request it to be added into the |
2012 | * namespace's tree |
2013 | */ |
2014 | static int do_new_mount(struct path *path, const char *fstype, int flags, |
2015 | int mnt_flags, const char *name, void *data) |
2016 | { |
2017 | struct file_system_type *type; |
2018 | struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; |
2019 | struct vfsmount *mnt; |
2020 | int err; |
2021 | |
2022 | if (!fstype) |
2023 | return -EINVAL; |
2024 | |
2025 | type = get_fs_type(fstype); |
2026 | if (!type) |
2027 | return -ENODEV; |
2028 | |
2029 | if (user_ns != &init_user_ns) { |
2030 | if (!(type->fs_flags & FS_USERNS_MOUNT)) { |
2031 | put_filesystem(type); |
2032 | return -EPERM; |
2033 | } |
2034 | /* Only in special cases allow devices from mounts |
2035 | * created outside the initial user namespace. |
2036 | */ |
2037 | if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) { |
2038 | flags |= MS_NODEV; |
2039 | mnt_flags |= MNT_NODEV; |
2040 | } |
2041 | } |
2042 | |
2043 | mnt = vfs_kern_mount(type, flags, name, data); |
2044 | if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && |
2045 | !mnt->mnt_sb->s_subtype) |
2046 | mnt = fs_set_subtype(mnt, fstype); |
2047 | |
2048 | put_filesystem(type); |
2049 | if (IS_ERR(mnt)) |
2050 | return PTR_ERR(mnt); |
2051 | |
2052 | err = do_add_mount(real_mount(mnt), path, mnt_flags); |
2053 | if (err) |
2054 | mntput(mnt); |
2055 | return err; |
2056 | } |
2057 | |
2058 | int finish_automount(struct vfsmount *m, struct path *path) |
2059 | { |
2060 | struct mount *mnt = real_mount(m); |
2061 | int err; |
2062 | /* The new mount record should have at least 2 refs to prevent it being |
2063 | * expired before we get a chance to add it |
2064 | */ |
2065 | BUG_ON(mnt_get_count(mnt) < 2); |
2066 | |
2067 | if (m->mnt_sb == path->mnt->mnt_sb && |
2068 | m->mnt_root == path->dentry) { |
2069 | err = -ELOOP; |
2070 | goto fail; |
2071 | } |
2072 | |
2073 | err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE); |
2074 | if (!err) |
2075 | return 0; |
2076 | fail: |
2077 | /* remove m from any expiration list it may be on */ |
2078 | if (!list_empty(&mnt->mnt_expire)) { |
2079 | namespace_lock(); |
2080 | br_write_lock(&vfsmount_lock); |
2081 | list_del_init(&mnt->mnt_expire); |
2082 | br_write_unlock(&vfsmount_lock); |
2083 | namespace_unlock(); |
2084 | } |
2085 | mntput(m); |
2086 | mntput(m); |
2087 | return err; |
2088 | } |
2089 | |
2090 | /** |
2091 | * mnt_set_expiry - Put a mount on an expiration list |
2092 | * @mnt: The mount to list. |
2093 | * @expiry_list: The list to add the mount to. |
2094 | */ |
2095 | void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list) |
2096 | { |
2097 | namespace_lock(); |
2098 | br_write_lock(&vfsmount_lock); |
2099 | |
2100 | list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list); |
2101 | |
2102 | br_write_unlock(&vfsmount_lock); |
2103 | namespace_unlock(); |
2104 | } |
2105 | EXPORT_SYMBOL(mnt_set_expiry); |
2106 | |
2107 | /* |
2108 | * process a list of expirable mountpoints with the intent of discarding any |
2109 | * mountpoints that aren't in use and haven't been touched since last we came |
2110 | * here |
2111 | */ |
2112 | void mark_mounts_for_expiry(struct list_head *mounts) |
2113 | { |
2114 | struct mount *mnt, *next; |
2115 | LIST_HEAD(graveyard); |
2116 | |
2117 | if (list_empty(mounts)) |
2118 | return; |
2119 | |
2120 | namespace_lock(); |
2121 | br_write_lock(&vfsmount_lock); |
2122 | |
2123 | /* extract from the expiration list every vfsmount that matches the |
2124 | * following criteria: |
2125 | * - only referenced by its parent vfsmount |
2126 | * - still marked for expiry (marked on the last call here; marks are |
2127 | * cleared by mntput()) |
2128 | */ |
2129 | list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { |
2130 | if (!xchg(&mnt->mnt_expiry_mark, 1) || |
2131 | propagate_mount_busy(mnt, 1)) |
2132 | continue; |
2133 | list_move(&mnt->mnt_expire, &graveyard); |
2134 | } |
2135 | while (!list_empty(&graveyard)) { |
2136 | mnt = list_first_entry(&graveyard, struct mount, mnt_expire); |
2137 | touch_mnt_namespace(mnt->mnt_ns); |
2138 | umount_tree(mnt, 1); |
2139 | } |
2140 | br_write_unlock(&vfsmount_lock); |
2141 | namespace_unlock(); |
2142 | } |
2143 | |
2144 | EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); |
2145 | |
2146 | /* |
2147 | * Ripoff of 'select_parent()' |
2148 | * |
2149 | * search the list of submounts for a given mountpoint, and move any |
2150 | * shrinkable submounts to the 'graveyard' list. |
2151 | */ |
2152 | static int select_submounts(struct mount *parent, struct list_head *graveyard) |
2153 | { |
2154 | struct mount *this_parent = parent; |
2155 | struct list_head *next; |
2156 | int found = 0; |
2157 | |
2158 | repeat: |
2159 | next = this_parent->mnt_mounts.next; |
2160 | resume: |
2161 | while (next != &this_parent->mnt_mounts) { |
2162 | struct list_head *tmp = next; |
2163 | struct mount *mnt = list_entry(tmp, struct mount, mnt_child); |
2164 | |
2165 | next = tmp->next; |
2166 | if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE)) |
2167 | continue; |
2168 | /* |
2169 | * Descend a level if the d_mounts list is non-empty. |
2170 | */ |
2171 | if (!list_empty(&mnt->mnt_mounts)) { |
2172 | this_parent = mnt; |
2173 | goto repeat; |
2174 | } |
2175 | |
2176 | if (!propagate_mount_busy(mnt, 1)) { |
2177 | list_move_tail(&mnt->mnt_expire, graveyard); |
2178 | found++; |
2179 | } |
2180 | } |
2181 | /* |
2182 | * All done at this level ... ascend and resume the search |
2183 | */ |
2184 | if (this_parent != parent) { |
2185 | next = this_parent->mnt_child.next; |
2186 | this_parent = this_parent->mnt_parent; |
2187 | goto resume; |
2188 | } |
2189 | return found; |
2190 | } |
2191 | |
2192 | /* |
2193 | * process a list of expirable mountpoints with the intent of discarding any |
2194 | * submounts of a specific parent mountpoint |
2195 | * |
2196 | * vfsmount_lock must be held for write |
2197 | */ |
2198 | static void shrink_submounts(struct mount *mnt) |
2199 | { |
2200 | LIST_HEAD(graveyard); |
2201 | struct mount *m; |
2202 | |
2203 | /* extract submounts of 'mountpoint' from the expiration list */ |
2204 | while (select_submounts(mnt, &graveyard)) { |
2205 | while (!list_empty(&graveyard)) { |
2206 | m = list_first_entry(&graveyard, struct mount, |
2207 | mnt_expire); |
2208 | touch_mnt_namespace(m->mnt_ns); |
2209 | umount_tree(m, 1); |
2210 | } |
2211 | } |
2212 | } |
2213 | |
2214 | /* |
2215 | * Some copy_from_user() implementations do not return the exact number of |
2216 | * bytes remaining to copy on a fault. But copy_mount_options() requires that. |
2217 | * Note that this function differs from copy_from_user() in that it will oops |
2218 | * on bad values of `to', rather than returning a short copy. |
2219 | */ |
2220 | static long exact_copy_from_user(void *to, const void __user * from, |
2221 | unsigned long n) |
2222 | { |
2223 | char *t = to; |
2224 | const char __user *f = from; |
2225 | char c; |
2226 | |
2227 | if (!access_ok(VERIFY_READ, from, n)) |
2228 | return n; |
2229 | |
2230 | while (n) { |
2231 | if (__get_user(c, f)) { |
2232 | memset(t, 0, n); |
2233 | break; |
2234 | } |
2235 | *t++ = c; |
2236 | f++; |
2237 | n--; |
2238 | } |
2239 | return n; |
2240 | } |
2241 | |
2242 | int copy_mount_options(const void __user * data, unsigned long *where) |
2243 | { |
2244 | int i; |
2245 | unsigned long page; |
2246 | unsigned long size; |
2247 | |
2248 | *where = 0; |
2249 | if (!data) |
2250 | return 0; |
2251 | |
2252 | if (!(page = __get_free_page(GFP_KERNEL))) |
2253 | return -ENOMEM; |
2254 | |
2255 | /* We only care that *some* data at the address the user |
2256 | * gave us is valid. Just in case, we'll zero |
2257 | * the remainder of the page. |
2258 | */ |
2259 | /* copy_from_user cannot cross TASK_SIZE ! */ |
2260 | size = TASK_SIZE - (unsigned long)data; |
2261 | if (size > PAGE_SIZE) |
2262 | size = PAGE_SIZE; |
2263 | |
2264 | i = size - exact_copy_from_user((void *)page, data, size); |
2265 | if (!i) { |
2266 | free_page(page); |
2267 | return -EFAULT; |
2268 | } |
2269 | if (i != PAGE_SIZE) |
2270 | memset((char *)page + i, 0, PAGE_SIZE - i); |
2271 | *where = page; |
2272 | return 0; |
2273 | } |
2274 | |
2275 | int copy_mount_string(const void __user *data, char **where) |
2276 | { |
2277 | char *tmp; |
2278 | |
2279 | if (!data) { |
2280 | *where = NULL; |
2281 | return 0; |
2282 | } |
2283 | |
2284 | tmp = strndup_user(data, PAGE_SIZE); |
2285 | if (IS_ERR(tmp)) |
2286 | return PTR_ERR(tmp); |
2287 | |
2288 | *where = tmp; |
2289 | return 0; |
2290 | } |
2291 | |
2292 | /* |
2293 | * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to |
2294 | * be given to the mount() call (ie: read-only, no-dev, no-suid etc). |
2295 | * |
2296 | * data is a (void *) that can point to any structure up to |
2297 | * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent |
2298 | * information (or be NULL). |
2299 | * |
2300 | * Pre-0.97 versions of mount() didn't have a flags word. |
2301 | * When the flags word was introduced its top half was required |
2302 | * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. |
2303 | * Therefore, if this magic number is present, it carries no information |
2304 | * and must be discarded. |
2305 | */ |
2306 | long do_mount(const char *dev_name, const char *dir_name, |
2307 | const char *type_page, unsigned long flags, void *data_page) |
2308 | { |
2309 | struct path path; |
2310 | int retval = 0; |
2311 | int mnt_flags = 0; |
2312 | |
2313 | /* Discard magic */ |
2314 | if ((flags & MS_MGC_MSK) == MS_MGC_VAL) |
2315 | flags &= ~MS_MGC_MSK; |
2316 | |
2317 | /* Basic sanity checks */ |
2318 | |
2319 | if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) |
2320 | return -EINVAL; |
2321 | |
2322 | if (data_page) |
2323 | ((char *)data_page)[PAGE_SIZE - 1] = 0; |
2324 | |
2325 | /* ... and get the mountpoint */ |
2326 | retval = kern_path(dir_name, LOOKUP_FOLLOW, &path); |
2327 | if (retval) |
2328 | return retval; |
2329 | |
2330 | retval = security_sb_mount(dev_name, &path, |
2331 | type_page, flags, data_page); |
2332 | if (!retval && !may_mount()) |
2333 | retval = -EPERM; |
2334 | if (retval) |
2335 | goto dput_out; |
2336 | |
2337 | /* Default to relatime unless overriden */ |
2338 | if (!(flags & MS_NOATIME)) |
2339 | mnt_flags |= MNT_RELATIME; |
2340 | |
2341 | /* Separate the per-mountpoint flags */ |
2342 | if (flags & MS_NOSUID) |
2343 | mnt_flags |= MNT_NOSUID; |
2344 | if (flags & MS_NODEV) |
2345 | mnt_flags |= MNT_NODEV; |
2346 | if (flags & MS_NOEXEC) |
2347 | mnt_flags |= MNT_NOEXEC; |
2348 | if (flags & MS_NOATIME) |
2349 | mnt_flags |= MNT_NOATIME; |
2350 | if (flags & MS_NODIRATIME) |
2351 | mnt_flags |= MNT_NODIRATIME; |
2352 | if (flags & MS_STRICTATIME) |
2353 | mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); |
2354 | if (flags & MS_RDONLY) |
2355 | mnt_flags |= MNT_READONLY; |
2356 | |
2357 | flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN | |
2358 | MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT | |
2359 | MS_STRICTATIME); |
2360 | |
2361 | if (flags & MS_REMOUNT) |
2362 | retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags, |
2363 | data_page); |
2364 | else if (flags & MS_BIND) |
2365 | retval = do_loopback(&path, dev_name, flags & MS_REC); |
2366 | else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
2367 | retval = do_change_type(&path, flags); |
2368 | else if (flags & MS_MOVE) |
2369 | retval = do_move_mount(&path, dev_name); |
2370 | else |
2371 | retval = do_new_mount(&path, type_page, flags, mnt_flags, |
2372 | dev_name, data_page); |
2373 | dput_out: |
2374 | path_put(&path); |
2375 | return retval; |
2376 | } |
2377 | |
2378 | static void free_mnt_ns(struct mnt_namespace *ns) |
2379 | { |
2380 | proc_free_inum(ns->proc_inum); |
2381 | put_user_ns(ns->user_ns); |
2382 | kfree(ns); |
2383 | } |
2384 | |
2385 | /* |
2386 | * Assign a sequence number so we can detect when we attempt to bind |
2387 | * mount a reference to an older mount namespace into the current |
2388 | * mount namespace, preventing reference counting loops. A 64bit |
2389 | * number incrementing at 10Ghz will take 12,427 years to wrap which |
2390 | * is effectively never, so we can ignore the possibility. |
2391 | */ |
2392 | static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1); |
2393 | |
2394 | static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns) |
2395 | { |
2396 | struct mnt_namespace *new_ns; |
2397 | int ret; |
2398 | |
2399 | new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); |
2400 | if (!new_ns) |
2401 | return ERR_PTR(-ENOMEM); |
2402 | ret = proc_alloc_inum(&new_ns->proc_inum); |
2403 | if (ret) { |
2404 | kfree(new_ns); |
2405 | return ERR_PTR(ret); |
2406 | } |
2407 | new_ns->seq = atomic64_add_return(1, &mnt_ns_seq); |
2408 | atomic_set(&new_ns->count, 1); |
2409 | new_ns->root = NULL; |
2410 | INIT_LIST_HEAD(&new_ns->list); |
2411 | init_waitqueue_head(&new_ns->poll); |
2412 | new_ns->event = 0; |
2413 | new_ns->user_ns = get_user_ns(user_ns); |
2414 | return new_ns; |
2415 | } |
2416 | |
2417 | /* |
2418 | * Allocate a new namespace structure and populate it with contents |
2419 | * copied from the namespace of the passed in task structure. |
2420 | */ |
2421 | static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns, |
2422 | struct user_namespace *user_ns, struct fs_struct *fs) |
2423 | { |
2424 | struct mnt_namespace *new_ns; |
2425 | struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; |
2426 | struct mount *p, *q; |
2427 | struct mount *old = mnt_ns->root; |
2428 | struct mount *new; |
2429 | int copy_flags; |
2430 | |
2431 | new_ns = alloc_mnt_ns(user_ns); |
2432 | if (IS_ERR(new_ns)) |
2433 | return new_ns; |
2434 | |
2435 | namespace_lock(); |
2436 | /* First pass: copy the tree topology */ |
2437 | copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE; |
2438 | if (user_ns != mnt_ns->user_ns) |
2439 | copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED; |
2440 | new = copy_tree(old, old->mnt.mnt_root, copy_flags); |
2441 | if (IS_ERR(new)) { |
2442 | namespace_unlock(); |
2443 | free_mnt_ns(new_ns); |
2444 | return ERR_CAST(new); |
2445 | } |
2446 | new_ns->root = new; |
2447 | br_write_lock(&vfsmount_lock); |
2448 | list_add_tail(&new_ns->list, &new->mnt_list); |
2449 | br_write_unlock(&vfsmount_lock); |
2450 | |
2451 | /* |
2452 | * Second pass: switch the tsk->fs->* elements and mark new vfsmounts |
2453 | * as belonging to new namespace. We have already acquired a private |
2454 | * fs_struct, so tsk->fs->lock is not needed. |
2455 | */ |
2456 | p = old; |
2457 | q = new; |
2458 | while (p) { |
2459 | q->mnt_ns = new_ns; |
2460 | if (fs) { |
2461 | if (&p->mnt == fs->root.mnt) { |
2462 | fs->root.mnt = mntget(&q->mnt); |
2463 | rootmnt = &p->mnt; |
2464 | } |
2465 | if (&p->mnt == fs->pwd.mnt) { |
2466 | fs->pwd.mnt = mntget(&q->mnt); |
2467 | pwdmnt = &p->mnt; |
2468 | } |
2469 | } |
2470 | p = next_mnt(p, old); |
2471 | q = next_mnt(q, new); |
2472 | if (!q) |
2473 | break; |
2474 | while (p->mnt.mnt_root != q->mnt.mnt_root) |
2475 | p = next_mnt(p, old); |
2476 | } |
2477 | namespace_unlock(); |
2478 | |
2479 | if (rootmnt) |
2480 | mntput(rootmnt); |
2481 | if (pwdmnt) |
2482 | mntput(pwdmnt); |
2483 | |
2484 | return new_ns; |
2485 | } |
2486 | |
2487 | struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, |
2488 | struct user_namespace *user_ns, struct fs_struct *new_fs) |
2489 | { |
2490 | struct mnt_namespace *new_ns; |
2491 | |
2492 | BUG_ON(!ns); |
2493 | get_mnt_ns(ns); |
2494 | |
2495 | if (!(flags & CLONE_NEWNS)) |
2496 | return ns; |
2497 | |
2498 | new_ns = dup_mnt_ns(ns, user_ns, new_fs); |
2499 | |
2500 | put_mnt_ns(ns); |
2501 | return new_ns; |
2502 | } |
2503 | |
2504 | /** |
2505 | * create_mnt_ns - creates a private namespace and adds a root filesystem |
2506 | * @mnt: pointer to the new root filesystem mountpoint |
2507 | */ |
2508 | static struct mnt_namespace *create_mnt_ns(struct vfsmount *m) |
2509 | { |
2510 | struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns); |
2511 | if (!IS_ERR(new_ns)) { |
2512 | struct mount *mnt = real_mount(m); |
2513 | mnt->mnt_ns = new_ns; |
2514 | new_ns->root = mnt; |
2515 | list_add(&mnt->mnt_list, &new_ns->list); |
2516 | } else { |
2517 | mntput(m); |
2518 | } |
2519 | return new_ns; |
2520 | } |
2521 | |
2522 | struct dentry *mount_subtree(struct vfsmount *mnt, const char *name) |
2523 | { |
2524 | struct mnt_namespace *ns; |
2525 | struct super_block *s; |
2526 | struct path path; |
2527 | int err; |
2528 | |
2529 | ns = create_mnt_ns(mnt); |
2530 | if (IS_ERR(ns)) |
2531 | return ERR_CAST(ns); |
2532 | |
2533 | err = vfs_path_lookup(mnt->mnt_root, mnt, |
2534 | name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); |
2535 | |
2536 | put_mnt_ns(ns); |
2537 | |
2538 | if (err) |
2539 | return ERR_PTR(err); |
2540 | |
2541 | /* trade a vfsmount reference for active sb one */ |
2542 | s = path.mnt->mnt_sb; |
2543 | atomic_inc(&s->s_active); |
2544 | mntput(path.mnt); |
2545 | /* lock the sucker */ |
2546 | down_write(&s->s_umount); |
2547 | /* ... and return the root of (sub)tree on it */ |
2548 | return path.dentry; |
2549 | } |
2550 | EXPORT_SYMBOL(mount_subtree); |
2551 | |
2552 | SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, |
2553 | char __user *, type, unsigned long, flags, void __user *, data) |
2554 | { |
2555 | int ret; |
2556 | char *kernel_type; |
2557 | struct filename *kernel_dir; |
2558 | char *kernel_dev; |
2559 | unsigned long data_page; |
2560 | |
2561 | ret = copy_mount_string(type, &kernel_type); |
2562 | if (ret < 0) |
2563 | goto out_type; |
2564 | |
2565 | kernel_dir = getname(dir_name); |
2566 | if (IS_ERR(kernel_dir)) { |
2567 | ret = PTR_ERR(kernel_dir); |
2568 | goto out_dir; |
2569 | } |
2570 | |
2571 | ret = copy_mount_string(dev_name, &kernel_dev); |
2572 | if (ret < 0) |
2573 | goto out_dev; |
2574 | |
2575 | ret = copy_mount_options(data, &data_page); |
2576 | if (ret < 0) |
2577 | goto out_data; |
2578 | |
2579 | ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags, |
2580 | (void *) data_page); |
2581 | |
2582 | free_page(data_page); |
2583 | out_data: |
2584 | kfree(kernel_dev); |
2585 | out_dev: |
2586 | putname(kernel_dir); |
2587 | out_dir: |
2588 | kfree(kernel_type); |
2589 | out_type: |
2590 | return ret; |
2591 | } |
2592 | |
2593 | /* |
2594 | * Return true if path is reachable from root |
2595 | * |
2596 | * namespace_sem or vfsmount_lock is held |
2597 | */ |
2598 | bool is_path_reachable(struct mount *mnt, struct dentry *dentry, |
2599 | const struct path *root) |
2600 | { |
2601 | while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) { |
2602 | dentry = mnt->mnt_mountpoint; |
2603 | mnt = mnt->mnt_parent; |
2604 | } |
2605 | return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry); |
2606 | } |
2607 | |
2608 | int path_is_under(struct path *path1, struct path *path2) |
2609 | { |
2610 | int res; |
2611 | br_read_lock(&vfsmount_lock); |
2612 | res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2); |
2613 | br_read_unlock(&vfsmount_lock); |
2614 | return res; |
2615 | } |
2616 | EXPORT_SYMBOL(path_is_under); |
2617 | |
2618 | /* |
2619 | * pivot_root Semantics: |
2620 | * Moves the root file system of the current process to the directory put_old, |
2621 | * makes new_root as the new root file system of the current process, and sets |
2622 | * root/cwd of all processes which had them on the current root to new_root. |
2623 | * |
2624 | * Restrictions: |
2625 | * The new_root and put_old must be directories, and must not be on the |
2626 | * same file system as the current process root. The put_old must be |
2627 | * underneath new_root, i.e. adding a non-zero number of /.. to the string |
2628 | * pointed to by put_old must yield the same directory as new_root. No other |
2629 | * file system may be mounted on put_old. After all, new_root is a mountpoint. |
2630 | * |
2631 | * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. |
2632 | * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives |
2633 | * in this situation. |
2634 | * |
2635 | * Notes: |
2636 | * - we don't move root/cwd if they are not at the root (reason: if something |
2637 | * cared enough to change them, it's probably wrong to force them elsewhere) |
2638 | * - it's okay to pick a root that isn't the root of a file system, e.g. |
2639 | * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, |
2640 | * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root |
2641 | * first. |
2642 | */ |
2643 | SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, |
2644 | const char __user *, put_old) |
2645 | { |
2646 | struct path new, old, parent_path, root_parent, root; |
2647 | struct mount *new_mnt, *root_mnt, *old_mnt; |
2648 | struct mountpoint *old_mp, *root_mp; |
2649 | int error; |
2650 | |
2651 | if (!may_mount()) |
2652 | return -EPERM; |
2653 | |
2654 | error = user_path_dir(new_root, &new); |
2655 | if (error) |
2656 | goto out0; |
2657 | |
2658 | error = user_path_dir(put_old, &old); |
2659 | if (error) |
2660 | goto out1; |
2661 | |
2662 | error = security_sb_pivotroot(&old, &new); |
2663 | if (error) |
2664 | goto out2; |
2665 | |
2666 | get_fs_root(current->fs, &root); |
2667 | old_mp = lock_mount(&old); |
2668 | error = PTR_ERR(old_mp); |
2669 | if (IS_ERR(old_mp)) |
2670 | goto out3; |
2671 | |
2672 | error = -EINVAL; |
2673 | new_mnt = real_mount(new.mnt); |
2674 | root_mnt = real_mount(root.mnt); |
2675 | old_mnt = real_mount(old.mnt); |
2676 | if (IS_MNT_SHARED(old_mnt) || |
2677 | IS_MNT_SHARED(new_mnt->mnt_parent) || |
2678 | IS_MNT_SHARED(root_mnt->mnt_parent)) |
2679 | goto out4; |
2680 | if (!check_mnt(root_mnt) || !check_mnt(new_mnt)) |
2681 | goto out4; |
2682 | if (new_mnt->mnt.mnt_flags & MNT_LOCKED) |
2683 | goto out4; |
2684 | error = -ENOENT; |
2685 | if (d_unlinked(new.dentry)) |
2686 | goto out4; |
2687 | error = -EBUSY; |
2688 | if (new_mnt == root_mnt || old_mnt == root_mnt) |
2689 | goto out4; /* loop, on the same file system */ |
2690 | error = -EINVAL; |
2691 | if (root.mnt->mnt_root != root.dentry) |
2692 | goto out4; /* not a mountpoint */ |
2693 | if (!mnt_has_parent(root_mnt)) |
2694 | goto out4; /* not attached */ |
2695 | root_mp = root_mnt->mnt_mp; |
2696 | if (new.mnt->mnt_root != new.dentry) |
2697 | goto out4; /* not a mountpoint */ |
2698 | if (!mnt_has_parent(new_mnt)) |
2699 | goto out4; /* not attached */ |
2700 | /* make sure we can reach put_old from new_root */ |
2701 | if (!is_path_reachable(old_mnt, old.dentry, &new)) |
2702 | goto out4; |
2703 | root_mp->m_count++; /* pin it so it won't go away */ |
2704 | br_write_lock(&vfsmount_lock); |
2705 | detach_mnt(new_mnt, &parent_path); |
2706 | detach_mnt(root_mnt, &root_parent); |
2707 | if (root_mnt->mnt.mnt_flags & MNT_LOCKED) { |
2708 | new_mnt->mnt.mnt_flags |= MNT_LOCKED; |
2709 | root_mnt->mnt.mnt_flags &= ~MNT_LOCKED; |
2710 | } |
2711 | /* mount old root on put_old */ |
2712 | attach_mnt(root_mnt, old_mnt, old_mp); |
2713 | /* mount new_root on / */ |
2714 | attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp); |
2715 | touch_mnt_namespace(current->nsproxy->mnt_ns); |
2716 | br_write_unlock(&vfsmount_lock); |
2717 | chroot_fs_refs(&root, &new); |
2718 | put_mountpoint(root_mp); |
2719 | error = 0; |
2720 | out4: |
2721 | unlock_mount(old_mp); |
2722 | if (!error) { |
2723 | path_put(&root_parent); |
2724 | path_put(&parent_path); |
2725 | } |
2726 | out3: |
2727 | path_put(&root); |
2728 | out2: |
2729 | path_put(&old); |
2730 | out1: |
2731 | path_put(&new); |
2732 | out0: |
2733 | return error; |
2734 | } |
2735 | |
2736 | static void __init init_mount_tree(void) |
2737 | { |
2738 | struct vfsmount *mnt; |
2739 | struct mnt_namespace *ns; |
2740 | struct path root; |
2741 | struct file_system_type *type; |
2742 | |
2743 | type = get_fs_type("rootfs"); |
2744 | if (!type) |
2745 | panic("Can't find rootfs type"); |
2746 | mnt = vfs_kern_mount(type, 0, "rootfs", NULL); |
2747 | put_filesystem(type); |
2748 | if (IS_ERR(mnt)) |
2749 | panic("Can't create rootfs"); |
2750 | |
2751 | ns = create_mnt_ns(mnt); |
2752 | if (IS_ERR(ns)) |
2753 | panic("Can't allocate initial namespace"); |
2754 | |
2755 | init_task.nsproxy->mnt_ns = ns; |
2756 | get_mnt_ns(ns); |
2757 | |
2758 | root.mnt = mnt; |
2759 | root.dentry = mnt->mnt_root; |
2760 | |
2761 | set_fs_pwd(current->fs, &root); |
2762 | set_fs_root(current->fs, &root); |
2763 | } |
2764 | |
2765 | void __init mnt_init(void) |
2766 | { |
2767 | unsigned u; |
2768 | int err; |
2769 | |
2770 | init_rwsem(&namespace_sem); |
2771 | |
2772 | mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount), |
2773 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); |
2774 | |
2775 | mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); |
2776 | mountpoint_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); |
2777 | |
2778 | if (!mount_hashtable || !mountpoint_hashtable) |
2779 | panic("Failed to allocate mount hash table\n"); |
2780 | |
2781 | printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE); |
2782 | |
2783 | for (u = 0; u < HASH_SIZE; u++) |
2784 | INIT_LIST_HEAD(&mount_hashtable[u]); |
2785 | for (u = 0; u < HASH_SIZE; u++) |
2786 | INIT_LIST_HEAD(&mountpoint_hashtable[u]); |
2787 | |
2788 | br_lock_init(&vfsmount_lock); |
2789 | |
2790 | err = sysfs_init(); |
2791 | if (err) |
2792 | printk(KERN_WARNING "%s: sysfs_init error: %d\n", |
2793 | __func__, err); |
2794 | fs_kobj = kobject_create_and_add("fs", NULL); |
2795 | if (!fs_kobj) |
2796 | printk(KERN_WARNING "%s: kobj create error\n", __func__); |
2797 | init_rootfs(); |
2798 | init_mount_tree(); |
2799 | } |
2800 | |
2801 | void put_mnt_ns(struct mnt_namespace *ns) |
2802 | { |
2803 | if (!atomic_dec_and_test(&ns->count)) |
2804 | return; |
2805 | namespace_lock(); |
2806 | br_write_lock(&vfsmount_lock); |
2807 | umount_tree(ns->root, 0); |
2808 | br_write_unlock(&vfsmount_lock); |
2809 | namespace_unlock(); |
2810 | free_mnt_ns(ns); |
2811 | } |
2812 | |
2813 | struct vfsmount *kern_mount_data(struct file_system_type *type, void *data) |
2814 | { |
2815 | struct vfsmount *mnt; |
2816 | mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data); |
2817 | if (!IS_ERR(mnt)) { |
2818 | /* |
2819 | * it is a longterm mount, don't release mnt until |
2820 | * we unmount before file sys is unregistered |
2821 | */ |
2822 | real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL; |
2823 | } |
2824 | return mnt; |
2825 | } |
2826 | EXPORT_SYMBOL_GPL(kern_mount_data); |
2827 | |
2828 | void kern_unmount(struct vfsmount *mnt) |
2829 | { |
2830 | /* release long term mount so mount point can be released */ |
2831 | if (!IS_ERR_OR_NULL(mnt)) { |
2832 | br_write_lock(&vfsmount_lock); |
2833 | real_mount(mnt)->mnt_ns = NULL; |
2834 | br_write_unlock(&vfsmount_lock); |
2835 | mntput(mnt); |
2836 | } |
2837 | } |
2838 | EXPORT_SYMBOL(kern_unmount); |
2839 | |
2840 | bool our_mnt(struct vfsmount *mnt) |
2841 | { |
2842 | return check_mnt(real_mount(mnt)); |
2843 | } |
2844 | |
2845 | bool current_chrooted(void) |
2846 | { |
2847 | /* Does the current process have a non-standard root */ |
2848 | struct path ns_root; |
2849 | struct path fs_root; |
2850 | bool chrooted; |
2851 | |
2852 | /* Find the namespace root */ |
2853 | ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt; |
2854 | ns_root.dentry = ns_root.mnt->mnt_root; |
2855 | path_get(&ns_root); |
2856 | while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root)) |
2857 | ; |
2858 | |
2859 | get_fs_root(current->fs, &fs_root); |
2860 | |
2861 | chrooted = !path_equal(&fs_root, &ns_root); |
2862 | |
2863 | path_put(&fs_root); |
2864 | path_put(&ns_root); |
2865 | |
2866 | return chrooted; |
2867 | } |
2868 | |
2869 | bool fs_fully_visible(struct file_system_type *type) |
2870 | { |
2871 | struct mnt_namespace *ns = current->nsproxy->mnt_ns; |
2872 | struct mount *mnt; |
2873 | bool visible = false; |
2874 | |
2875 | if (unlikely(!ns)) |
2876 | return false; |
2877 | |
2878 | namespace_lock(); |
2879 | list_for_each_entry(mnt, &ns->list, mnt_list) { |
2880 | struct mount *child; |
2881 | if (mnt->mnt.mnt_sb->s_type != type) |
2882 | continue; |
2883 | |
2884 | /* This mount is not fully visible if there are any child mounts |
2885 | * that cover anything except for empty directories. |
2886 | */ |
2887 | list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { |
2888 | struct inode *inode = child->mnt_mountpoint->d_inode; |
2889 | if (!S_ISDIR(inode->i_mode)) |
2890 | goto next; |
2891 | if (inode->i_nlink != 2) |
2892 | goto next; |
2893 | } |
2894 | visible = true; |
2895 | goto found; |
2896 | next: ; |
2897 | } |
2898 | found: |
2899 | namespace_unlock(); |
2900 | return visible; |
2901 | } |
2902 | |
2903 | static void *mntns_get(struct task_struct *task) |
2904 | { |
2905 | struct mnt_namespace *ns = NULL; |
2906 | struct nsproxy *nsproxy; |
2907 | |
2908 | rcu_read_lock(); |
2909 | nsproxy = task_nsproxy(task); |
2910 | if (nsproxy) { |
2911 | ns = nsproxy->mnt_ns; |
2912 | get_mnt_ns(ns); |
2913 | } |
2914 | rcu_read_unlock(); |
2915 | |
2916 | return ns; |
2917 | } |
2918 | |
2919 | static void mntns_put(void *ns) |
2920 | { |
2921 | put_mnt_ns(ns); |
2922 | } |
2923 | |
2924 | static int mntns_install(struct nsproxy *nsproxy, void *ns) |
2925 | { |
2926 | struct fs_struct *fs = current->fs; |
2927 | struct mnt_namespace *mnt_ns = ns; |
2928 | struct path root; |
2929 | |
2930 | if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) || |
2931 | !ns_capable(current_user_ns(), CAP_SYS_CHROOT) || |
2932 | !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) |
2933 | return -EPERM; |
2934 | |
2935 | if (fs->users != 1) |
2936 | return -EINVAL; |
2937 | |
2938 | get_mnt_ns(mnt_ns); |
2939 | put_mnt_ns(nsproxy->mnt_ns); |
2940 | nsproxy->mnt_ns = mnt_ns; |
2941 | |
2942 | /* Find the root */ |
2943 | root.mnt = &mnt_ns->root->mnt; |
2944 | root.dentry = mnt_ns->root->mnt.mnt_root; |
2945 | path_get(&root); |
2946 | while(d_mountpoint(root.dentry) && follow_down_one(&root)) |
2947 | ; |
2948 | |
2949 | /* Update the pwd and root */ |
2950 | set_fs_pwd(fs, &root); |
2951 | set_fs_root(fs, &root); |
2952 | |
2953 | path_put(&root); |
2954 | return 0; |
2955 | } |
2956 | |
2957 | static unsigned int mntns_inum(void *ns) |
2958 | { |
2959 | struct mnt_namespace *mnt_ns = ns; |
2960 | return mnt_ns->proc_inum; |
2961 | } |
2962 | |
2963 | const struct proc_ns_operations mntns_operations = { |
2964 | .name = "mnt", |
2965 | .type = CLONE_NEWNS, |
2966 | .get = mntns_get, |
2967 | .put = mntns_put, |
2968 | .install = mntns_install, |
2969 | .inum = mntns_inum, |
2970 | }; |
2971 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9