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1 | /* | |
2 | * linux/fs/namespace.c | |
3 | * | |
4 | * (C) Copyright Al Viro 2000, 2001 | |
5 | * Released under GPL v2. | |
6 | * | |
7 | * Based on code from fs/super.c, copyright Linus Torvalds and others. | |
8 | * Heavily rewritten. | |
9 | */ | |
10 | ||
11 | #include <linux/syscalls.h> | |
12 | #include <linux/export.h> | |
13 | #include <linux/capability.h> | |
14 | #include <linux/mnt_namespace.h> | |
15 | #include <linux/user_namespace.h> | |
16 | #include <linux/namei.h> | |
17 | #include <linux/security.h> | |
18 | #include <linux/idr.h> | |
19 | #include <linux/acct.h> /* acct_auto_close_mnt */ | |
20 | #include <linux/ramfs.h> /* init_rootfs */ | |
21 | #include <linux/fs_struct.h> /* get_fs_root et.al. */ | |
22 | #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */ | |
23 | #include <linux/uaccess.h> | |
24 | #include <linux/proc_fs.h> | |
25 | #include "pnode.h" | |
26 | #include "internal.h" | |
27 | ||
28 | #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head)) | |
29 | #define HASH_SIZE (1UL << HASH_SHIFT) | |
30 | ||
31 | static int event; | |
32 | static DEFINE_IDA(mnt_id_ida); | |
33 | static DEFINE_IDA(mnt_group_ida); | |
34 | static DEFINE_SPINLOCK(mnt_id_lock); | |
35 | static int mnt_id_start = 0; | |
36 | static int mnt_group_start = 1; | |
37 | ||
38 | static struct list_head *mount_hashtable __read_mostly; | |
39 | static struct kmem_cache *mnt_cache __read_mostly; | |
40 | static struct rw_semaphore namespace_sem; | |
41 | ||
42 | /* /sys/fs */ | |
43 | struct kobject *fs_kobj; | |
44 | EXPORT_SYMBOL_GPL(fs_kobj); | |
45 | ||
46 | /* | |
47 | * vfsmount lock may be taken for read to prevent changes to the | |
48 | * vfsmount hash, ie. during mountpoint lookups or walking back | |
49 | * up the tree. | |
50 | * | |
51 | * It should be taken for write in all cases where the vfsmount | |
52 | * tree or hash is modified or when a vfsmount structure is modified. | |
53 | */ | |
54 | DEFINE_BRLOCK(vfsmount_lock); | |
55 | ||
56 | static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) | |
57 | { | |
58 | unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); | |
59 | tmp += ((unsigned long)dentry / L1_CACHE_BYTES); | |
60 | tmp = tmp + (tmp >> HASH_SHIFT); | |
61 | return tmp & (HASH_SIZE - 1); | |
62 | } | |
63 | ||
64 | #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16) | |
65 | ||
66 | /* | |
67 | * allocation is serialized by namespace_sem, but we need the spinlock to | |
68 | * serialize with freeing. | |
69 | */ | |
70 | static int mnt_alloc_id(struct mount *mnt) | |
71 | { | |
72 | int res; | |
73 | ||
74 | retry: | |
75 | ida_pre_get(&mnt_id_ida, GFP_KERNEL); | |
76 | spin_lock(&mnt_id_lock); | |
77 | res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id); | |
78 | if (!res) | |
79 | mnt_id_start = mnt->mnt_id + 1; | |
80 | spin_unlock(&mnt_id_lock); | |
81 | if (res == -EAGAIN) | |
82 | goto retry; | |
83 | ||
84 | return res; | |
85 | } | |
86 | ||
87 | static void mnt_free_id(struct mount *mnt) | |
88 | { | |
89 | int id = mnt->mnt_id; | |
90 | spin_lock(&mnt_id_lock); | |
91 | ida_remove(&mnt_id_ida, id); | |
92 | if (mnt_id_start > id) | |
93 | mnt_id_start = id; | |
94 | spin_unlock(&mnt_id_lock); | |
95 | } | |
96 | ||
97 | /* | |
98 | * Allocate a new peer group ID | |
99 | * | |
100 | * mnt_group_ida is protected by namespace_sem | |
101 | */ | |
102 | static int mnt_alloc_group_id(struct mount *mnt) | |
103 | { | |
104 | int res; | |
105 | ||
106 | if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL)) | |
107 | return -ENOMEM; | |
108 | ||
109 | res = ida_get_new_above(&mnt_group_ida, | |
110 | mnt_group_start, | |
111 | &mnt->mnt_group_id); | |
112 | if (!res) | |
113 | mnt_group_start = mnt->mnt_group_id + 1; | |
114 | ||
115 | return res; | |
116 | } | |
117 | ||
118 | /* | |
119 | * Release a peer group ID | |
120 | */ | |
121 | void mnt_release_group_id(struct mount *mnt) | |
122 | { | |
123 | int id = mnt->mnt_group_id; | |
124 | ida_remove(&mnt_group_ida, id); | |
125 | if (mnt_group_start > id) | |
126 | mnt_group_start = id; | |
127 | mnt->mnt_group_id = 0; | |
128 | } | |
129 | ||
130 | /* | |
131 | * vfsmount lock must be held for read | |
132 | */ | |
133 | static inline void mnt_add_count(struct mount *mnt, int n) | |
134 | { | |
135 | #ifdef CONFIG_SMP | |
136 | this_cpu_add(mnt->mnt_pcp->mnt_count, n); | |
137 | #else | |
138 | preempt_disable(); | |
139 | mnt->mnt_count += n; | |
140 | preempt_enable(); | |
141 | #endif | |
142 | } | |
143 | ||
144 | /* | |
145 | * vfsmount lock must be held for write | |
146 | */ | |
147 | unsigned int mnt_get_count(struct mount *mnt) | |
148 | { | |
149 | #ifdef CONFIG_SMP | |
150 | unsigned int count = 0; | |
151 | int cpu; | |
152 | ||
153 | for_each_possible_cpu(cpu) { | |
154 | count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count; | |
155 | } | |
156 | ||
157 | return count; | |
158 | #else | |
159 | return mnt->mnt_count; | |
160 | #endif | |
161 | } | |
162 | ||
163 | static struct mount *alloc_vfsmnt(const char *name) | |
164 | { | |
165 | struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); | |
166 | if (mnt) { | |
167 | int err; | |
168 | ||
169 | err = mnt_alloc_id(mnt); | |
170 | if (err) | |
171 | goto out_free_cache; | |
172 | ||
173 | if (name) { | |
174 | mnt->mnt_devname = kstrdup(name, GFP_KERNEL); | |
175 | if (!mnt->mnt_devname) | |
176 | goto out_free_id; | |
177 | } | |
178 | ||
179 | #ifdef CONFIG_SMP | |
180 | mnt->mnt_pcp = alloc_percpu(struct mnt_pcp); | |
181 | if (!mnt->mnt_pcp) | |
182 | goto out_free_devname; | |
183 | ||
184 | this_cpu_add(mnt->mnt_pcp->mnt_count, 1); | |
185 | #else | |
186 | mnt->mnt_count = 1; | |
187 | mnt->mnt_writers = 0; | |
188 | #endif | |
189 | ||
190 | INIT_LIST_HEAD(&mnt->mnt_hash); | |
191 | INIT_LIST_HEAD(&mnt->mnt_child); | |
192 | INIT_LIST_HEAD(&mnt->mnt_mounts); | |
193 | INIT_LIST_HEAD(&mnt->mnt_list); | |
194 | INIT_LIST_HEAD(&mnt->mnt_expire); | |
195 | INIT_LIST_HEAD(&mnt->mnt_share); | |
196 | INIT_LIST_HEAD(&mnt->mnt_slave_list); | |
197 | INIT_LIST_HEAD(&mnt->mnt_slave); | |
198 | #ifdef CONFIG_FSNOTIFY | |
199 | INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks); | |
200 | #endif | |
201 | } | |
202 | return mnt; | |
203 | ||
204 | #ifdef CONFIG_SMP | |
205 | out_free_devname: | |
206 | kfree(mnt->mnt_devname); | |
207 | #endif | |
208 | out_free_id: | |
209 | mnt_free_id(mnt); | |
210 | out_free_cache: | |
211 | kmem_cache_free(mnt_cache, mnt); | |
212 | return NULL; | |
213 | } | |
214 | ||
215 | /* | |
216 | * Most r/o checks on a fs are for operations that take | |
217 | * discrete amounts of time, like a write() or unlink(). | |
218 | * We must keep track of when those operations start | |
219 | * (for permission checks) and when they end, so that | |
220 | * we can determine when writes are able to occur to | |
221 | * a filesystem. | |
222 | */ | |
223 | /* | |
224 | * __mnt_is_readonly: check whether a mount is read-only | |
225 | * @mnt: the mount to check for its write status | |
226 | * | |
227 | * This shouldn't be used directly ouside of the VFS. | |
228 | * It does not guarantee that the filesystem will stay | |
229 | * r/w, just that it is right *now*. This can not and | |
230 | * should not be used in place of IS_RDONLY(inode). | |
231 | * mnt_want/drop_write() will _keep_ the filesystem | |
232 | * r/w. | |
233 | */ | |
234 | int __mnt_is_readonly(struct vfsmount *mnt) | |
235 | { | |
236 | if (mnt->mnt_flags & MNT_READONLY) | |
237 | return 1; | |
238 | if (mnt->mnt_sb->s_flags & MS_RDONLY) | |
239 | return 1; | |
240 | return 0; | |
241 | } | |
242 | EXPORT_SYMBOL_GPL(__mnt_is_readonly); | |
243 | ||
244 | static inline void mnt_inc_writers(struct mount *mnt) | |
245 | { | |
246 | #ifdef CONFIG_SMP | |
247 | this_cpu_inc(mnt->mnt_pcp->mnt_writers); | |
248 | #else | |
249 | mnt->mnt_writers++; | |
250 | #endif | |
251 | } | |
252 | ||
253 | static inline void mnt_dec_writers(struct mount *mnt) | |
254 | { | |
255 | #ifdef CONFIG_SMP | |
256 | this_cpu_dec(mnt->mnt_pcp->mnt_writers); | |
257 | #else | |
258 | mnt->mnt_writers--; | |
259 | #endif | |
260 | } | |
261 | ||
262 | static unsigned int mnt_get_writers(struct mount *mnt) | |
263 | { | |
264 | #ifdef CONFIG_SMP | |
265 | unsigned int count = 0; | |
266 | int cpu; | |
267 | ||
268 | for_each_possible_cpu(cpu) { | |
269 | count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers; | |
270 | } | |
271 | ||
272 | return count; | |
273 | #else | |
274 | return mnt->mnt_writers; | |
275 | #endif | |
276 | } | |
277 | ||
278 | static int mnt_is_readonly(struct vfsmount *mnt) | |
279 | { | |
280 | if (mnt->mnt_sb->s_readonly_remount) | |
281 | return 1; | |
282 | /* Order wrt setting s_flags/s_readonly_remount in do_remount() */ | |
283 | smp_rmb(); | |
284 | return __mnt_is_readonly(mnt); | |
285 | } | |
286 | ||
287 | /* | |
288 | * Most r/o & frozen checks on a fs are for operations that take discrete | |
289 | * amounts of time, like a write() or unlink(). We must keep track of when | |
290 | * those operations start (for permission checks) and when they end, so that we | |
291 | * can determine when writes are able to occur to a filesystem. | |
292 | */ | |
293 | /** | |
294 | * __mnt_want_write - get write access to a mount without freeze protection | |
295 | * @m: the mount on which to take a write | |
296 | * | |
297 | * This tells the low-level filesystem that a write is about to be performed to | |
298 | * it, and makes sure that writes are allowed (mnt it read-write) before | |
299 | * returning success. This operation does not protect against filesystem being | |
300 | * frozen. When the write operation is finished, __mnt_drop_write() must be | |
301 | * called. This is effectively a refcount. | |
302 | */ | |
303 | int __mnt_want_write(struct vfsmount *m) | |
304 | { | |
305 | struct mount *mnt = real_mount(m); | |
306 | int ret = 0; | |
307 | ||
308 | preempt_disable(); | |
309 | mnt_inc_writers(mnt); | |
310 | /* | |
311 | * The store to mnt_inc_writers must be visible before we pass | |
312 | * MNT_WRITE_HOLD loop below, so that the slowpath can see our | |
313 | * incremented count after it has set MNT_WRITE_HOLD. | |
314 | */ | |
315 | smp_mb(); | |
316 | while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) | |
317 | cpu_relax(); | |
318 | /* | |
319 | * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will | |
320 | * be set to match its requirements. So we must not load that until | |
321 | * MNT_WRITE_HOLD is cleared. | |
322 | */ | |
323 | smp_rmb(); | |
324 | if (mnt_is_readonly(m)) { | |
325 | mnt_dec_writers(mnt); | |
326 | ret = -EROFS; | |
327 | } | |
328 | preempt_enable(); | |
329 | ||
330 | return ret; | |
331 | } | |
332 | ||
333 | /** | |
334 | * mnt_want_write - get write access to a mount | |
335 | * @m: the mount on which to take a write | |
336 | * | |
337 | * This tells the low-level filesystem that a write is about to be performed to | |
338 | * it, and makes sure that writes are allowed (mount is read-write, filesystem | |
339 | * is not frozen) before returning success. When the write operation is | |
340 | * finished, mnt_drop_write() must be called. This is effectively a refcount. | |
341 | */ | |
342 | int mnt_want_write(struct vfsmount *m) | |
343 | { | |
344 | int ret; | |
345 | ||
346 | sb_start_write(m->mnt_sb); | |
347 | ret = __mnt_want_write(m); | |
348 | if (ret) | |
349 | sb_end_write(m->mnt_sb); | |
350 | return ret; | |
351 | } | |
352 | EXPORT_SYMBOL_GPL(mnt_want_write); | |
353 | ||
354 | /** | |
355 | * mnt_clone_write - get write access to a mount | |
356 | * @mnt: the mount on which to take a write | |
357 | * | |
358 | * This is effectively like mnt_want_write, except | |
359 | * it must only be used to take an extra write reference | |
360 | * on a mountpoint that we already know has a write reference | |
361 | * on it. This allows some optimisation. | |
362 | * | |
363 | * After finished, mnt_drop_write must be called as usual to | |
364 | * drop the reference. | |
365 | */ | |
366 | int mnt_clone_write(struct vfsmount *mnt) | |
367 | { | |
368 | /* superblock may be r/o */ | |
369 | if (__mnt_is_readonly(mnt)) | |
370 | return -EROFS; | |
371 | preempt_disable(); | |
372 | mnt_inc_writers(real_mount(mnt)); | |
373 | preempt_enable(); | |
374 | return 0; | |
375 | } | |
376 | EXPORT_SYMBOL_GPL(mnt_clone_write); | |
377 | ||
378 | /** | |
379 | * __mnt_want_write_file - get write access to a file's mount | |
380 | * @file: the file who's mount on which to take a write | |
381 | * | |
382 | * This is like __mnt_want_write, but it takes a file and can | |
383 | * do some optimisations if the file is open for write already | |
384 | */ | |
385 | int __mnt_want_write_file(struct file *file) | |
386 | { | |
387 | struct inode *inode = file->f_dentry->d_inode; | |
388 | ||
389 | if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode)) | |
390 | return __mnt_want_write(file->f_path.mnt); | |
391 | else | |
392 | return mnt_clone_write(file->f_path.mnt); | |
393 | } | |
394 | ||
395 | /** | |
396 | * mnt_want_write_file - get write access to a file's mount | |
397 | * @file: the file who's mount on which to take a write | |
398 | * | |
399 | * This is like mnt_want_write, but it takes a file and can | |
400 | * do some optimisations if the file is open for write already | |
401 | */ | |
402 | int mnt_want_write_file(struct file *file) | |
403 | { | |
404 | int ret; | |
405 | ||
406 | sb_start_write(file->f_path.mnt->mnt_sb); | |
407 | ret = __mnt_want_write_file(file); | |
408 | if (ret) | |
409 | sb_end_write(file->f_path.mnt->mnt_sb); | |
410 | return ret; | |
411 | } | |
412 | EXPORT_SYMBOL_GPL(mnt_want_write_file); | |
413 | ||
414 | /** | |
415 | * __mnt_drop_write - give up write access to a mount | |
416 | * @mnt: the mount on which to give up write access | |
417 | * | |
418 | * Tells the low-level filesystem that we are done | |
419 | * performing writes to it. Must be matched with | |
420 | * __mnt_want_write() call above. | |
421 | */ | |
422 | void __mnt_drop_write(struct vfsmount *mnt) | |
423 | { | |
424 | preempt_disable(); | |
425 | mnt_dec_writers(real_mount(mnt)); | |
426 | preempt_enable(); | |
427 | } | |
428 | ||
429 | /** | |
430 | * mnt_drop_write - give up write access to a mount | |
431 | * @mnt: the mount on which to give up write access | |
432 | * | |
433 | * Tells the low-level filesystem that we are done performing writes to it and | |
434 | * also allows filesystem to be frozen again. Must be matched with | |
435 | * mnt_want_write() call above. | |
436 | */ | |
437 | void mnt_drop_write(struct vfsmount *mnt) | |
438 | { | |
439 | __mnt_drop_write(mnt); | |
440 | sb_end_write(mnt->mnt_sb); | |
441 | } | |
442 | EXPORT_SYMBOL_GPL(mnt_drop_write); | |
443 | ||
444 | void __mnt_drop_write_file(struct file *file) | |
445 | { | |
446 | __mnt_drop_write(file->f_path.mnt); | |
447 | } | |
448 | ||
449 | void mnt_drop_write_file(struct file *file) | |
450 | { | |
451 | mnt_drop_write(file->f_path.mnt); | |
452 | } | |
453 | EXPORT_SYMBOL(mnt_drop_write_file); | |
454 | ||
455 | static int mnt_make_readonly(struct mount *mnt) | |
456 | { | |
457 | int ret = 0; | |
458 | ||
459 | br_write_lock(&vfsmount_lock); | |
460 | mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; | |
461 | /* | |
462 | * After storing MNT_WRITE_HOLD, we'll read the counters. This store | |
463 | * should be visible before we do. | |
464 | */ | |
465 | smp_mb(); | |
466 | ||
467 | /* | |
468 | * With writers on hold, if this value is zero, then there are | |
469 | * definitely no active writers (although held writers may subsequently | |
470 | * increment the count, they'll have to wait, and decrement it after | |
471 | * seeing MNT_READONLY). | |
472 | * | |
473 | * It is OK to have counter incremented on one CPU and decremented on | |
474 | * another: the sum will add up correctly. The danger would be when we | |
475 | * sum up each counter, if we read a counter before it is incremented, | |
476 | * but then read another CPU's count which it has been subsequently | |
477 | * decremented from -- we would see more decrements than we should. | |
478 | * MNT_WRITE_HOLD protects against this scenario, because | |
479 | * mnt_want_write first increments count, then smp_mb, then spins on | |
480 | * MNT_WRITE_HOLD, so it can't be decremented by another CPU while | |
481 | * we're counting up here. | |
482 | */ | |
483 | if (mnt_get_writers(mnt) > 0) | |
484 | ret = -EBUSY; | |
485 | else | |
486 | mnt->mnt.mnt_flags |= MNT_READONLY; | |
487 | /* | |
488 | * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers | |
489 | * that become unheld will see MNT_READONLY. | |
490 | */ | |
491 | smp_wmb(); | |
492 | mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; | |
493 | br_write_unlock(&vfsmount_lock); | |
494 | return ret; | |
495 | } | |
496 | ||
497 | static void __mnt_unmake_readonly(struct mount *mnt) | |
498 | { | |
499 | br_write_lock(&vfsmount_lock); | |
500 | mnt->mnt.mnt_flags &= ~MNT_READONLY; | |
501 | br_write_unlock(&vfsmount_lock); | |
502 | } | |
503 | ||
504 | int sb_prepare_remount_readonly(struct super_block *sb) | |
505 | { | |
506 | struct mount *mnt; | |
507 | int err = 0; | |
508 | ||
509 | /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */ | |
510 | if (atomic_long_read(&sb->s_remove_count)) | |
511 | return -EBUSY; | |
512 | ||
513 | br_write_lock(&vfsmount_lock); | |
514 | list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { | |
515 | if (!(mnt->mnt.mnt_flags & MNT_READONLY)) { | |
516 | mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; | |
517 | smp_mb(); | |
518 | if (mnt_get_writers(mnt) > 0) { | |
519 | err = -EBUSY; | |
520 | break; | |
521 | } | |
522 | } | |
523 | } | |
524 | if (!err && atomic_long_read(&sb->s_remove_count)) | |
525 | err = -EBUSY; | |
526 | ||
527 | if (!err) { | |
528 | sb->s_readonly_remount = 1; | |
529 | smp_wmb(); | |
530 | } | |
531 | list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { | |
532 | if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD) | |
533 | mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; | |
534 | } | |
535 | br_write_unlock(&vfsmount_lock); | |
536 | ||
537 | return err; | |
538 | } | |
539 | ||
540 | static void free_vfsmnt(struct mount *mnt) | |
541 | { | |
542 | kfree(mnt->mnt_devname); | |
543 | mnt_free_id(mnt); | |
544 | #ifdef CONFIG_SMP | |
545 | free_percpu(mnt->mnt_pcp); | |
546 | #endif | |
547 | kmem_cache_free(mnt_cache, mnt); | |
548 | } | |
549 | ||
550 | /* | |
551 | * find the first or last mount at @dentry on vfsmount @mnt depending on | |
552 | * @dir. If @dir is set return the first mount else return the last mount. | |
553 | * vfsmount_lock must be held for read or write. | |
554 | */ | |
555 | struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry, | |
556 | int dir) | |
557 | { | |
558 | struct list_head *head = mount_hashtable + hash(mnt, dentry); | |
559 | struct list_head *tmp = head; | |
560 | struct mount *p, *found = NULL; | |
561 | ||
562 | for (;;) { | |
563 | tmp = dir ? tmp->next : tmp->prev; | |
564 | p = NULL; | |
565 | if (tmp == head) | |
566 | break; | |
567 | p = list_entry(tmp, struct mount, mnt_hash); | |
568 | if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) { | |
569 | found = p; | |
570 | break; | |
571 | } | |
572 | } | |
573 | return found; | |
574 | } | |
575 | ||
576 | /* | |
577 | * lookup_mnt - Return the first child mount mounted at path | |
578 | * | |
579 | * "First" means first mounted chronologically. If you create the | |
580 | * following mounts: | |
581 | * | |
582 | * mount /dev/sda1 /mnt | |
583 | * mount /dev/sda2 /mnt | |
584 | * mount /dev/sda3 /mnt | |
585 | * | |
586 | * Then lookup_mnt() on the base /mnt dentry in the root mount will | |
587 | * return successively the root dentry and vfsmount of /dev/sda1, then | |
588 | * /dev/sda2, then /dev/sda3, then NULL. | |
589 | * | |
590 | * lookup_mnt takes a reference to the found vfsmount. | |
591 | */ | |
592 | struct vfsmount *lookup_mnt(struct path *path) | |
593 | { | |
594 | struct mount *child_mnt; | |
595 | ||
596 | br_read_lock(&vfsmount_lock); | |
597 | child_mnt = __lookup_mnt(path->mnt, path->dentry, 1); | |
598 | if (child_mnt) { | |
599 | mnt_add_count(child_mnt, 1); | |
600 | br_read_unlock(&vfsmount_lock); | |
601 | return &child_mnt->mnt; | |
602 | } else { | |
603 | br_read_unlock(&vfsmount_lock); | |
604 | return NULL; | |
605 | } | |
606 | } | |
607 | ||
608 | static inline int check_mnt(struct mount *mnt) | |
609 | { | |
610 | return mnt->mnt_ns == current->nsproxy->mnt_ns; | |
611 | } | |
612 | ||
613 | /* | |
614 | * vfsmount lock must be held for write | |
615 | */ | |
616 | static void touch_mnt_namespace(struct mnt_namespace *ns) | |
617 | { | |
618 | if (ns) { | |
619 | ns->event = ++event; | |
620 | wake_up_interruptible(&ns->poll); | |
621 | } | |
622 | } | |
623 | ||
624 | /* | |
625 | * vfsmount lock must be held for write | |
626 | */ | |
627 | static void __touch_mnt_namespace(struct mnt_namespace *ns) | |
628 | { | |
629 | if (ns && ns->event != event) { | |
630 | ns->event = event; | |
631 | wake_up_interruptible(&ns->poll); | |
632 | } | |
633 | } | |
634 | ||
635 | /* | |
636 | * Clear dentry's mounted state if it has no remaining mounts. | |
637 | * vfsmount_lock must be held for write. | |
638 | */ | |
639 | static void dentry_reset_mounted(struct dentry *dentry) | |
640 | { | |
641 | unsigned u; | |
642 | ||
643 | for (u = 0; u < HASH_SIZE; u++) { | |
644 | struct mount *p; | |
645 | ||
646 | list_for_each_entry(p, &mount_hashtable[u], mnt_hash) { | |
647 | if (p->mnt_mountpoint == dentry) | |
648 | return; | |
649 | } | |
650 | } | |
651 | spin_lock(&dentry->d_lock); | |
652 | dentry->d_flags &= ~DCACHE_MOUNTED; | |
653 | spin_unlock(&dentry->d_lock); | |
654 | } | |
655 | ||
656 | /* | |
657 | * vfsmount lock must be held for write | |
658 | */ | |
659 | static void detach_mnt(struct mount *mnt, struct path *old_path) | |
660 | { | |
661 | old_path->dentry = mnt->mnt_mountpoint; | |
662 | old_path->mnt = &mnt->mnt_parent->mnt; | |
663 | mnt->mnt_parent = mnt; | |
664 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; | |
665 | list_del_init(&mnt->mnt_child); | |
666 | list_del_init(&mnt->mnt_hash); | |
667 | dentry_reset_mounted(old_path->dentry); | |
668 | } | |
669 | ||
670 | /* | |
671 | * vfsmount lock must be held for write | |
672 | */ | |
673 | void mnt_set_mountpoint(struct mount *mnt, struct dentry *dentry, | |
674 | struct mount *child_mnt) | |
675 | { | |
676 | mnt_add_count(mnt, 1); /* essentially, that's mntget */ | |
677 | child_mnt->mnt_mountpoint = dget(dentry); | |
678 | child_mnt->mnt_parent = mnt; | |
679 | spin_lock(&dentry->d_lock); | |
680 | dentry->d_flags |= DCACHE_MOUNTED; | |
681 | spin_unlock(&dentry->d_lock); | |
682 | } | |
683 | ||
684 | /* | |
685 | * vfsmount lock must be held for write | |
686 | */ | |
687 | static void attach_mnt(struct mount *mnt, struct path *path) | |
688 | { | |
689 | mnt_set_mountpoint(real_mount(path->mnt), path->dentry, mnt); | |
690 | list_add_tail(&mnt->mnt_hash, mount_hashtable + | |
691 | hash(path->mnt, path->dentry)); | |
692 | list_add_tail(&mnt->mnt_child, &real_mount(path->mnt)->mnt_mounts); | |
693 | } | |
694 | ||
695 | /* | |
696 | * vfsmount lock must be held for write | |
697 | */ | |
698 | static void commit_tree(struct mount *mnt) | |
699 | { | |
700 | struct mount *parent = mnt->mnt_parent; | |
701 | struct mount *m; | |
702 | LIST_HEAD(head); | |
703 | struct mnt_namespace *n = parent->mnt_ns; | |
704 | ||
705 | BUG_ON(parent == mnt); | |
706 | ||
707 | list_add_tail(&head, &mnt->mnt_list); | |
708 | list_for_each_entry(m, &head, mnt_list) | |
709 | m->mnt_ns = n; | |
710 | ||
711 | list_splice(&head, n->list.prev); | |
712 | ||
713 | list_add_tail(&mnt->mnt_hash, mount_hashtable + | |
714 | hash(&parent->mnt, mnt->mnt_mountpoint)); | |
715 | list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); | |
716 | touch_mnt_namespace(n); | |
717 | } | |
718 | ||
719 | static struct mount *next_mnt(struct mount *p, struct mount *root) | |
720 | { | |
721 | struct list_head *next = p->mnt_mounts.next; | |
722 | if (next == &p->mnt_mounts) { | |
723 | while (1) { | |
724 | if (p == root) | |
725 | return NULL; | |
726 | next = p->mnt_child.next; | |
727 | if (next != &p->mnt_parent->mnt_mounts) | |
728 | break; | |
729 | p = p->mnt_parent; | |
730 | } | |
731 | } | |
732 | return list_entry(next, struct mount, mnt_child); | |
733 | } | |
734 | ||
735 | static struct mount *skip_mnt_tree(struct mount *p) | |
736 | { | |
737 | struct list_head *prev = p->mnt_mounts.prev; | |
738 | while (prev != &p->mnt_mounts) { | |
739 | p = list_entry(prev, struct mount, mnt_child); | |
740 | prev = p->mnt_mounts.prev; | |
741 | } | |
742 | return p; | |
743 | } | |
744 | ||
745 | struct vfsmount * | |
746 | vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data) | |
747 | { | |
748 | struct mount *mnt; | |
749 | struct dentry *root; | |
750 | ||
751 | if (!type) | |
752 | return ERR_PTR(-ENODEV); | |
753 | ||
754 | mnt = alloc_vfsmnt(name); | |
755 | if (!mnt) | |
756 | return ERR_PTR(-ENOMEM); | |
757 | ||
758 | if (flags & MS_KERNMOUNT) | |
759 | mnt->mnt.mnt_flags = MNT_INTERNAL; | |
760 | ||
761 | root = mount_fs(type, flags, name, data); | |
762 | if (IS_ERR(root)) { | |
763 | free_vfsmnt(mnt); | |
764 | return ERR_CAST(root); | |
765 | } | |
766 | ||
767 | mnt->mnt.mnt_root = root; | |
768 | mnt->mnt.mnt_sb = root->d_sb; | |
769 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; | |
770 | mnt->mnt_parent = mnt; | |
771 | br_write_lock(&vfsmount_lock); | |
772 | list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts); | |
773 | br_write_unlock(&vfsmount_lock); | |
774 | return &mnt->mnt; | |
775 | } | |
776 | EXPORT_SYMBOL_GPL(vfs_kern_mount); | |
777 | ||
778 | static struct mount *clone_mnt(struct mount *old, struct dentry *root, | |
779 | int flag) | |
780 | { | |
781 | struct super_block *sb = old->mnt.mnt_sb; | |
782 | struct mount *mnt; | |
783 | int err; | |
784 | ||
785 | mnt = alloc_vfsmnt(old->mnt_devname); | |
786 | if (!mnt) | |
787 | return ERR_PTR(-ENOMEM); | |
788 | ||
789 | if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE)) | |
790 | mnt->mnt_group_id = 0; /* not a peer of original */ | |
791 | else | |
792 | mnt->mnt_group_id = old->mnt_group_id; | |
793 | ||
794 | if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { | |
795 | err = mnt_alloc_group_id(mnt); | |
796 | if (err) | |
797 | goto out_free; | |
798 | } | |
799 | ||
800 | mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD; | |
801 | atomic_inc(&sb->s_active); | |
802 | mnt->mnt.mnt_sb = sb; | |
803 | mnt->mnt.mnt_root = dget(root); | |
804 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; | |
805 | mnt->mnt_parent = mnt; | |
806 | br_write_lock(&vfsmount_lock); | |
807 | list_add_tail(&mnt->mnt_instance, &sb->s_mounts); | |
808 | br_write_unlock(&vfsmount_lock); | |
809 | ||
810 | if ((flag & CL_SLAVE) || | |
811 | ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) { | |
812 | list_add(&mnt->mnt_slave, &old->mnt_slave_list); | |
813 | mnt->mnt_master = old; | |
814 | CLEAR_MNT_SHARED(mnt); | |
815 | } else if (!(flag & CL_PRIVATE)) { | |
816 | if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old)) | |
817 | list_add(&mnt->mnt_share, &old->mnt_share); | |
818 | if (IS_MNT_SLAVE(old)) | |
819 | list_add(&mnt->mnt_slave, &old->mnt_slave); | |
820 | mnt->mnt_master = old->mnt_master; | |
821 | } | |
822 | if (flag & CL_MAKE_SHARED) | |
823 | set_mnt_shared(mnt); | |
824 | ||
825 | /* stick the duplicate mount on the same expiry list | |
826 | * as the original if that was on one */ | |
827 | if (flag & CL_EXPIRE) { | |
828 | if (!list_empty(&old->mnt_expire)) | |
829 | list_add(&mnt->mnt_expire, &old->mnt_expire); | |
830 | } | |
831 | ||
832 | return mnt; | |
833 | ||
834 | out_free: | |
835 | free_vfsmnt(mnt); | |
836 | return ERR_PTR(err); | |
837 | } | |
838 | ||
839 | static inline void mntfree(struct mount *mnt) | |
840 | { | |
841 | struct vfsmount *m = &mnt->mnt; | |
842 | struct super_block *sb = m->mnt_sb; | |
843 | ||
844 | /* | |
845 | * This probably indicates that somebody messed | |
846 | * up a mnt_want/drop_write() pair. If this | |
847 | * happens, the filesystem was probably unable | |
848 | * to make r/w->r/o transitions. | |
849 | */ | |
850 | /* | |
851 | * The locking used to deal with mnt_count decrement provides barriers, | |
852 | * so mnt_get_writers() below is safe. | |
853 | */ | |
854 | WARN_ON(mnt_get_writers(mnt)); | |
855 | fsnotify_vfsmount_delete(m); | |
856 | dput(m->mnt_root); | |
857 | free_vfsmnt(mnt); | |
858 | deactivate_super(sb); | |
859 | } | |
860 | ||
861 | static void mntput_no_expire(struct mount *mnt) | |
862 | { | |
863 | put_again: | |
864 | #ifdef CONFIG_SMP | |
865 | br_read_lock(&vfsmount_lock); | |
866 | if (likely(mnt->mnt_ns)) { | |
867 | /* shouldn't be the last one */ | |
868 | mnt_add_count(mnt, -1); | |
869 | br_read_unlock(&vfsmount_lock); | |
870 | return; | |
871 | } | |
872 | br_read_unlock(&vfsmount_lock); | |
873 | ||
874 | br_write_lock(&vfsmount_lock); | |
875 | mnt_add_count(mnt, -1); | |
876 | if (mnt_get_count(mnt)) { | |
877 | br_write_unlock(&vfsmount_lock); | |
878 | return; | |
879 | } | |
880 | #else | |
881 | mnt_add_count(mnt, -1); | |
882 | if (likely(mnt_get_count(mnt))) | |
883 | return; | |
884 | br_write_lock(&vfsmount_lock); | |
885 | #endif | |
886 | if (unlikely(mnt->mnt_pinned)) { | |
887 | mnt_add_count(mnt, mnt->mnt_pinned + 1); | |
888 | mnt->mnt_pinned = 0; | |
889 | br_write_unlock(&vfsmount_lock); | |
890 | acct_auto_close_mnt(&mnt->mnt); | |
891 | goto put_again; | |
892 | } | |
893 | ||
894 | list_del(&mnt->mnt_instance); | |
895 | br_write_unlock(&vfsmount_lock); | |
896 | mntfree(mnt); | |
897 | } | |
898 | ||
899 | void mntput(struct vfsmount *mnt) | |
900 | { | |
901 | if (mnt) { | |
902 | struct mount *m = real_mount(mnt); | |
903 | /* avoid cacheline pingpong, hope gcc doesn't get "smart" */ | |
904 | if (unlikely(m->mnt_expiry_mark)) | |
905 | m->mnt_expiry_mark = 0; | |
906 | mntput_no_expire(m); | |
907 | } | |
908 | } | |
909 | EXPORT_SYMBOL(mntput); | |
910 | ||
911 | struct vfsmount *mntget(struct vfsmount *mnt) | |
912 | { | |
913 | if (mnt) | |
914 | mnt_add_count(real_mount(mnt), 1); | |
915 | return mnt; | |
916 | } | |
917 | EXPORT_SYMBOL(mntget); | |
918 | ||
919 | void mnt_pin(struct vfsmount *mnt) | |
920 | { | |
921 | br_write_lock(&vfsmount_lock); | |
922 | real_mount(mnt)->mnt_pinned++; | |
923 | br_write_unlock(&vfsmount_lock); | |
924 | } | |
925 | EXPORT_SYMBOL(mnt_pin); | |
926 | ||
927 | void mnt_unpin(struct vfsmount *m) | |
928 | { | |
929 | struct mount *mnt = real_mount(m); | |
930 | br_write_lock(&vfsmount_lock); | |
931 | if (mnt->mnt_pinned) { | |
932 | mnt_add_count(mnt, 1); | |
933 | mnt->mnt_pinned--; | |
934 | } | |
935 | br_write_unlock(&vfsmount_lock); | |
936 | } | |
937 | EXPORT_SYMBOL(mnt_unpin); | |
938 | ||
939 | static inline void mangle(struct seq_file *m, const char *s) | |
940 | { | |
941 | seq_escape(m, s, " \t\n\\"); | |
942 | } | |
943 | ||
944 | /* | |
945 | * Simple .show_options callback for filesystems which don't want to | |
946 | * implement more complex mount option showing. | |
947 | * | |
948 | * See also save_mount_options(). | |
949 | */ | |
950 | int generic_show_options(struct seq_file *m, struct dentry *root) | |
951 | { | |
952 | const char *options; | |
953 | ||
954 | rcu_read_lock(); | |
955 | options = rcu_dereference(root->d_sb->s_options); | |
956 | ||
957 | if (options != NULL && options[0]) { | |
958 | seq_putc(m, ','); | |
959 | mangle(m, options); | |
960 | } | |
961 | rcu_read_unlock(); | |
962 | ||
963 | return 0; | |
964 | } | |
965 | EXPORT_SYMBOL(generic_show_options); | |
966 | ||
967 | /* | |
968 | * If filesystem uses generic_show_options(), this function should be | |
969 | * called from the fill_super() callback. | |
970 | * | |
971 | * The .remount_fs callback usually needs to be handled in a special | |
972 | * way, to make sure, that previous options are not overwritten if the | |
973 | * remount fails. | |
974 | * | |
975 | * Also note, that if the filesystem's .remount_fs function doesn't | |
976 | * reset all options to their default value, but changes only newly | |
977 | * given options, then the displayed options will not reflect reality | |
978 | * any more. | |
979 | */ | |
980 | void save_mount_options(struct super_block *sb, char *options) | |
981 | { | |
982 | BUG_ON(sb->s_options); | |
983 | rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL)); | |
984 | } | |
985 | EXPORT_SYMBOL(save_mount_options); | |
986 | ||
987 | void replace_mount_options(struct super_block *sb, char *options) | |
988 | { | |
989 | char *old = sb->s_options; | |
990 | rcu_assign_pointer(sb->s_options, options); | |
991 | if (old) { | |
992 | synchronize_rcu(); | |
993 | kfree(old); | |
994 | } | |
995 | } | |
996 | EXPORT_SYMBOL(replace_mount_options); | |
997 | ||
998 | #ifdef CONFIG_PROC_FS | |
999 | /* iterator; we want it to have access to namespace_sem, thus here... */ | |
1000 | static void *m_start(struct seq_file *m, loff_t *pos) | |
1001 | { | |
1002 | struct proc_mounts *p = proc_mounts(m); | |
1003 | ||
1004 | down_read(&namespace_sem); | |
1005 | return seq_list_start(&p->ns->list, *pos); | |
1006 | } | |
1007 | ||
1008 | static void *m_next(struct seq_file *m, void *v, loff_t *pos) | |
1009 | { | |
1010 | struct proc_mounts *p = proc_mounts(m); | |
1011 | ||
1012 | return seq_list_next(v, &p->ns->list, pos); | |
1013 | } | |
1014 | ||
1015 | static void m_stop(struct seq_file *m, void *v) | |
1016 | { | |
1017 | up_read(&namespace_sem); | |
1018 | } | |
1019 | ||
1020 | static int m_show(struct seq_file *m, void *v) | |
1021 | { | |
1022 | struct proc_mounts *p = proc_mounts(m); | |
1023 | struct mount *r = list_entry(v, struct mount, mnt_list); | |
1024 | return p->show(m, &r->mnt); | |
1025 | } | |
1026 | ||
1027 | const struct seq_operations mounts_op = { | |
1028 | .start = m_start, | |
1029 | .next = m_next, | |
1030 | .stop = m_stop, | |
1031 | .show = m_show, | |
1032 | }; | |
1033 | #endif /* CONFIG_PROC_FS */ | |
1034 | ||
1035 | /** | |
1036 | * may_umount_tree - check if a mount tree is busy | |
1037 | * @mnt: root of mount tree | |
1038 | * | |
1039 | * This is called to check if a tree of mounts has any | |
1040 | * open files, pwds, chroots or sub mounts that are | |
1041 | * busy. | |
1042 | */ | |
1043 | int may_umount_tree(struct vfsmount *m) | |
1044 | { | |
1045 | struct mount *mnt = real_mount(m); | |
1046 | int actual_refs = 0; | |
1047 | int minimum_refs = 0; | |
1048 | struct mount *p; | |
1049 | BUG_ON(!m); | |
1050 | ||
1051 | /* write lock needed for mnt_get_count */ | |
1052 | br_write_lock(&vfsmount_lock); | |
1053 | for (p = mnt; p; p = next_mnt(p, mnt)) { | |
1054 | actual_refs += mnt_get_count(p); | |
1055 | minimum_refs += 2; | |
1056 | } | |
1057 | br_write_unlock(&vfsmount_lock); | |
1058 | ||
1059 | if (actual_refs > minimum_refs) | |
1060 | return 0; | |
1061 | ||
1062 | return 1; | |
1063 | } | |
1064 | ||
1065 | EXPORT_SYMBOL(may_umount_tree); | |
1066 | ||
1067 | /** | |
1068 | * may_umount - check if a mount point is busy | |
1069 | * @mnt: root of mount | |
1070 | * | |
1071 | * This is called to check if a mount point has any | |
1072 | * open files, pwds, chroots or sub mounts. If the | |
1073 | * mount has sub mounts this will return busy | |
1074 | * regardless of whether the sub mounts are busy. | |
1075 | * | |
1076 | * Doesn't take quota and stuff into account. IOW, in some cases it will | |
1077 | * give false negatives. The main reason why it's here is that we need | |
1078 | * a non-destructive way to look for easily umountable filesystems. | |
1079 | */ | |
1080 | int may_umount(struct vfsmount *mnt) | |
1081 | { | |
1082 | int ret = 1; | |
1083 | down_read(&namespace_sem); | |
1084 | br_write_lock(&vfsmount_lock); | |
1085 | if (propagate_mount_busy(real_mount(mnt), 2)) | |
1086 | ret = 0; | |
1087 | br_write_unlock(&vfsmount_lock); | |
1088 | up_read(&namespace_sem); | |
1089 | return ret; | |
1090 | } | |
1091 | ||
1092 | EXPORT_SYMBOL(may_umount); | |
1093 | ||
1094 | void release_mounts(struct list_head *head) | |
1095 | { | |
1096 | struct mount *mnt; | |
1097 | while (!list_empty(head)) { | |
1098 | mnt = list_first_entry(head, struct mount, mnt_hash); | |
1099 | list_del_init(&mnt->mnt_hash); | |
1100 | if (mnt_has_parent(mnt)) { | |
1101 | struct dentry *dentry; | |
1102 | struct mount *m; | |
1103 | ||
1104 | br_write_lock(&vfsmount_lock); | |
1105 | dentry = mnt->mnt_mountpoint; | |
1106 | m = mnt->mnt_parent; | |
1107 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; | |
1108 | mnt->mnt_parent = mnt; | |
1109 | m->mnt_ghosts--; | |
1110 | br_write_unlock(&vfsmount_lock); | |
1111 | dput(dentry); | |
1112 | mntput(&m->mnt); | |
1113 | } | |
1114 | mntput(&mnt->mnt); | |
1115 | } | |
1116 | } | |
1117 | ||
1118 | /* | |
1119 | * vfsmount lock must be held for write | |
1120 | * namespace_sem must be held for write | |
1121 | */ | |
1122 | void umount_tree(struct mount *mnt, int propagate, struct list_head *kill) | |
1123 | { | |
1124 | LIST_HEAD(tmp_list); | |
1125 | struct mount *p; | |
1126 | ||
1127 | for (p = mnt; p; p = next_mnt(p, mnt)) | |
1128 | list_move(&p->mnt_hash, &tmp_list); | |
1129 | ||
1130 | if (propagate) | |
1131 | propagate_umount(&tmp_list); | |
1132 | ||
1133 | list_for_each_entry(p, &tmp_list, mnt_hash) { | |
1134 | list_del_init(&p->mnt_expire); | |
1135 | list_del_init(&p->mnt_list); | |
1136 | __touch_mnt_namespace(p->mnt_ns); | |
1137 | p->mnt_ns = NULL; | |
1138 | list_del_init(&p->mnt_child); | |
1139 | if (mnt_has_parent(p)) { | |
1140 | p->mnt_parent->mnt_ghosts++; | |
1141 | dentry_reset_mounted(p->mnt_mountpoint); | |
1142 | } | |
1143 | change_mnt_propagation(p, MS_PRIVATE); | |
1144 | } | |
1145 | list_splice(&tmp_list, kill); | |
1146 | } | |
1147 | ||
1148 | static void shrink_submounts(struct mount *mnt, struct list_head *umounts); | |
1149 | ||
1150 | static int do_umount(struct mount *mnt, int flags) | |
1151 | { | |
1152 | struct super_block *sb = mnt->mnt.mnt_sb; | |
1153 | int retval; | |
1154 | LIST_HEAD(umount_list); | |
1155 | ||
1156 | retval = security_sb_umount(&mnt->mnt, flags); | |
1157 | if (retval) | |
1158 | return retval; | |
1159 | ||
1160 | /* | |
1161 | * Allow userspace to request a mountpoint be expired rather than | |
1162 | * unmounting unconditionally. Unmount only happens if: | |
1163 | * (1) the mark is already set (the mark is cleared by mntput()) | |
1164 | * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] | |
1165 | */ | |
1166 | if (flags & MNT_EXPIRE) { | |
1167 | if (&mnt->mnt == current->fs->root.mnt || | |
1168 | flags & (MNT_FORCE | MNT_DETACH)) | |
1169 | return -EINVAL; | |
1170 | ||
1171 | /* | |
1172 | * probably don't strictly need the lock here if we examined | |
1173 | * all race cases, but it's a slowpath. | |
1174 | */ | |
1175 | br_write_lock(&vfsmount_lock); | |
1176 | if (mnt_get_count(mnt) != 2) { | |
1177 | br_write_unlock(&vfsmount_lock); | |
1178 | return -EBUSY; | |
1179 | } | |
1180 | br_write_unlock(&vfsmount_lock); | |
1181 | ||
1182 | if (!xchg(&mnt->mnt_expiry_mark, 1)) | |
1183 | return -EAGAIN; | |
1184 | } | |
1185 | ||
1186 | /* | |
1187 | * If we may have to abort operations to get out of this | |
1188 | * mount, and they will themselves hold resources we must | |
1189 | * allow the fs to do things. In the Unix tradition of | |
1190 | * 'Gee thats tricky lets do it in userspace' the umount_begin | |
1191 | * might fail to complete on the first run through as other tasks | |
1192 | * must return, and the like. Thats for the mount program to worry | |
1193 | * about for the moment. | |
1194 | */ | |
1195 | ||
1196 | if (flags & MNT_FORCE && sb->s_op->umount_begin) { | |
1197 | sb->s_op->umount_begin(sb); | |
1198 | } | |
1199 | ||
1200 | /* | |
1201 | * No sense to grab the lock for this test, but test itself looks | |
1202 | * somewhat bogus. Suggestions for better replacement? | |
1203 | * Ho-hum... In principle, we might treat that as umount + switch | |
1204 | * to rootfs. GC would eventually take care of the old vfsmount. | |
1205 | * Actually it makes sense, especially if rootfs would contain a | |
1206 | * /reboot - static binary that would close all descriptors and | |
1207 | * call reboot(9). Then init(8) could umount root and exec /reboot. | |
1208 | */ | |
1209 | if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { | |
1210 | /* | |
1211 | * Special case for "unmounting" root ... | |
1212 | * we just try to remount it readonly. | |
1213 | */ | |
1214 | down_write(&sb->s_umount); | |
1215 | if (!(sb->s_flags & MS_RDONLY)) | |
1216 | retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); | |
1217 | up_write(&sb->s_umount); | |
1218 | return retval; | |
1219 | } | |
1220 | ||
1221 | down_write(&namespace_sem); | |
1222 | br_write_lock(&vfsmount_lock); | |
1223 | event++; | |
1224 | ||
1225 | if (!(flags & MNT_DETACH)) | |
1226 | shrink_submounts(mnt, &umount_list); | |
1227 | ||
1228 | retval = -EBUSY; | |
1229 | if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) { | |
1230 | if (!list_empty(&mnt->mnt_list)) | |
1231 | umount_tree(mnt, 1, &umount_list); | |
1232 | retval = 0; | |
1233 | } | |
1234 | br_write_unlock(&vfsmount_lock); | |
1235 | up_write(&namespace_sem); | |
1236 | release_mounts(&umount_list); | |
1237 | return retval; | |
1238 | } | |
1239 | ||
1240 | /* | |
1241 | * Is the caller allowed to modify his namespace? | |
1242 | */ | |
1243 | static inline bool may_mount(void) | |
1244 | { | |
1245 | return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN); | |
1246 | } | |
1247 | ||
1248 | /* | |
1249 | * Now umount can handle mount points as well as block devices. | |
1250 | * This is important for filesystems which use unnamed block devices. | |
1251 | * | |
1252 | * We now support a flag for forced unmount like the other 'big iron' | |
1253 | * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD | |
1254 | */ | |
1255 | ||
1256 | SYSCALL_DEFINE2(umount, char __user *, name, int, flags) | |
1257 | { | |
1258 | struct path path; | |
1259 | struct mount *mnt; | |
1260 | int retval; | |
1261 | int lookup_flags = 0; | |
1262 | ||
1263 | if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) | |
1264 | return -EINVAL; | |
1265 | ||
1266 | if (!may_mount()) | |
1267 | return -EPERM; | |
1268 | ||
1269 | if (!(flags & UMOUNT_NOFOLLOW)) | |
1270 | lookup_flags |= LOOKUP_FOLLOW; | |
1271 | ||
1272 | retval = user_path_at(AT_FDCWD, name, lookup_flags, &path); | |
1273 | if (retval) | |
1274 | goto out; | |
1275 | mnt = real_mount(path.mnt); | |
1276 | retval = -EINVAL; | |
1277 | if (path.dentry != path.mnt->mnt_root) | |
1278 | goto dput_and_out; | |
1279 | if (!check_mnt(mnt)) | |
1280 | goto dput_and_out; | |
1281 | ||
1282 | retval = do_umount(mnt, flags); | |
1283 | dput_and_out: | |
1284 | /* we mustn't call path_put() as that would clear mnt_expiry_mark */ | |
1285 | dput(path.dentry); | |
1286 | mntput_no_expire(mnt); | |
1287 | out: | |
1288 | return retval; | |
1289 | } | |
1290 | ||
1291 | #ifdef __ARCH_WANT_SYS_OLDUMOUNT | |
1292 | ||
1293 | /* | |
1294 | * The 2.0 compatible umount. No flags. | |
1295 | */ | |
1296 | SYSCALL_DEFINE1(oldumount, char __user *, name) | |
1297 | { | |
1298 | return sys_umount(name, 0); | |
1299 | } | |
1300 | ||
1301 | #endif | |
1302 | ||
1303 | static int mount_is_safe(struct path *path) | |
1304 | { | |
1305 | if (may_mount()) | |
1306 | return 0; | |
1307 | return -EPERM; | |
1308 | #ifdef notyet | |
1309 | if (S_ISLNK(path->dentry->d_inode->i_mode)) | |
1310 | return -EPERM; | |
1311 | if (path->dentry->d_inode->i_mode & S_ISVTX) { | |
1312 | if (current_uid() != path->dentry->d_inode->i_uid) | |
1313 | return -EPERM; | |
1314 | } | |
1315 | if (inode_permission(path->dentry->d_inode, MAY_WRITE)) | |
1316 | return -EPERM; | |
1317 | return 0; | |
1318 | #endif | |
1319 | } | |
1320 | ||
1321 | static bool mnt_ns_loop(struct path *path) | |
1322 | { | |
1323 | /* Could bind mounting the mount namespace inode cause a | |
1324 | * mount namespace loop? | |
1325 | */ | |
1326 | struct inode *inode = path->dentry->d_inode; | |
1327 | struct proc_inode *ei; | |
1328 | struct mnt_namespace *mnt_ns; | |
1329 | ||
1330 | if (!proc_ns_inode(inode)) | |
1331 | return false; | |
1332 | ||
1333 | ei = PROC_I(inode); | |
1334 | if (ei->ns_ops != &mntns_operations) | |
1335 | return false; | |
1336 | ||
1337 | mnt_ns = ei->ns; | |
1338 | return current->nsproxy->mnt_ns->seq >= mnt_ns->seq; | |
1339 | } | |
1340 | ||
1341 | struct mount *copy_tree(struct mount *mnt, struct dentry *dentry, | |
1342 | int flag) | |
1343 | { | |
1344 | struct mount *res, *p, *q, *r; | |
1345 | struct path path; | |
1346 | ||
1347 | if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt)) | |
1348 | return ERR_PTR(-EINVAL); | |
1349 | ||
1350 | res = q = clone_mnt(mnt, dentry, flag); | |
1351 | if (IS_ERR(q)) | |
1352 | return q; | |
1353 | ||
1354 | q->mnt_mountpoint = mnt->mnt_mountpoint; | |
1355 | ||
1356 | p = mnt; | |
1357 | list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { | |
1358 | struct mount *s; | |
1359 | if (!is_subdir(r->mnt_mountpoint, dentry)) | |
1360 | continue; | |
1361 | ||
1362 | for (s = r; s; s = next_mnt(s, r)) { | |
1363 | if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) { | |
1364 | s = skip_mnt_tree(s); | |
1365 | continue; | |
1366 | } | |
1367 | while (p != s->mnt_parent) { | |
1368 | p = p->mnt_parent; | |
1369 | q = q->mnt_parent; | |
1370 | } | |
1371 | p = s; | |
1372 | path.mnt = &q->mnt; | |
1373 | path.dentry = p->mnt_mountpoint; | |
1374 | q = clone_mnt(p, p->mnt.mnt_root, flag); | |
1375 | if (IS_ERR(q)) | |
1376 | goto out; | |
1377 | br_write_lock(&vfsmount_lock); | |
1378 | list_add_tail(&q->mnt_list, &res->mnt_list); | |
1379 | attach_mnt(q, &path); | |
1380 | br_write_unlock(&vfsmount_lock); | |
1381 | } | |
1382 | } | |
1383 | return res; | |
1384 | out: | |
1385 | if (res) { | |
1386 | LIST_HEAD(umount_list); | |
1387 | br_write_lock(&vfsmount_lock); | |
1388 | umount_tree(res, 0, &umount_list); | |
1389 | br_write_unlock(&vfsmount_lock); | |
1390 | release_mounts(&umount_list); | |
1391 | } | |
1392 | return q; | |
1393 | } | |
1394 | ||
1395 | /* Caller should check returned pointer for errors */ | |
1396 | ||
1397 | struct vfsmount *collect_mounts(struct path *path) | |
1398 | { | |
1399 | struct mount *tree; | |
1400 | down_write(&namespace_sem); | |
1401 | tree = copy_tree(real_mount(path->mnt), path->dentry, | |
1402 | CL_COPY_ALL | CL_PRIVATE); | |
1403 | up_write(&namespace_sem); | |
1404 | if (IS_ERR(tree)) | |
1405 | return NULL; | |
1406 | return &tree->mnt; | |
1407 | } | |
1408 | ||
1409 | void drop_collected_mounts(struct vfsmount *mnt) | |
1410 | { | |
1411 | LIST_HEAD(umount_list); | |
1412 | down_write(&namespace_sem); | |
1413 | br_write_lock(&vfsmount_lock); | |
1414 | umount_tree(real_mount(mnt), 0, &umount_list); | |
1415 | br_write_unlock(&vfsmount_lock); | |
1416 | up_write(&namespace_sem); | |
1417 | release_mounts(&umount_list); | |
1418 | } | |
1419 | ||
1420 | int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, | |
1421 | struct vfsmount *root) | |
1422 | { | |
1423 | struct mount *mnt; | |
1424 | int res = f(root, arg); | |
1425 | if (res) | |
1426 | return res; | |
1427 | list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) { | |
1428 | res = f(&mnt->mnt, arg); | |
1429 | if (res) | |
1430 | return res; | |
1431 | } | |
1432 | return 0; | |
1433 | } | |
1434 | ||
1435 | static void cleanup_group_ids(struct mount *mnt, struct mount *end) | |
1436 | { | |
1437 | struct mount *p; | |
1438 | ||
1439 | for (p = mnt; p != end; p = next_mnt(p, mnt)) { | |
1440 | if (p->mnt_group_id && !IS_MNT_SHARED(p)) | |
1441 | mnt_release_group_id(p); | |
1442 | } | |
1443 | } | |
1444 | ||
1445 | static int invent_group_ids(struct mount *mnt, bool recurse) | |
1446 | { | |
1447 | struct mount *p; | |
1448 | ||
1449 | for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { | |
1450 | if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { | |
1451 | int err = mnt_alloc_group_id(p); | |
1452 | if (err) { | |
1453 | cleanup_group_ids(mnt, p); | |
1454 | return err; | |
1455 | } | |
1456 | } | |
1457 | } | |
1458 | ||
1459 | return 0; | |
1460 | } | |
1461 | ||
1462 | /* | |
1463 | * @source_mnt : mount tree to be attached | |
1464 | * @nd : place the mount tree @source_mnt is attached | |
1465 | * @parent_nd : if non-null, detach the source_mnt from its parent and | |
1466 | * store the parent mount and mountpoint dentry. | |
1467 | * (done when source_mnt is moved) | |
1468 | * | |
1469 | * NOTE: in the table below explains the semantics when a source mount | |
1470 | * of a given type is attached to a destination mount of a given type. | |
1471 | * --------------------------------------------------------------------------- | |
1472 | * | BIND MOUNT OPERATION | | |
1473 | * |************************************************************************** | |
1474 | * | source-->| shared | private | slave | unbindable | | |
1475 | * | dest | | | | | | |
1476 | * | | | | | | | | |
1477 | * | v | | | | | | |
1478 | * |************************************************************************** | |
1479 | * | shared | shared (++) | shared (+) | shared(+++)| invalid | | |
1480 | * | | | | | | | |
1481 | * |non-shared| shared (+) | private | slave (*) | invalid | | |
1482 | * *************************************************************************** | |
1483 | * A bind operation clones the source mount and mounts the clone on the | |
1484 | * destination mount. | |
1485 | * | |
1486 | * (++) the cloned mount is propagated to all the mounts in the propagation | |
1487 | * tree of the destination mount and the cloned mount is added to | |
1488 | * the peer group of the source mount. | |
1489 | * (+) the cloned mount is created under the destination mount and is marked | |
1490 | * as shared. The cloned mount is added to the peer group of the source | |
1491 | * mount. | |
1492 | * (+++) the mount is propagated to all the mounts in the propagation tree | |
1493 | * of the destination mount and the cloned mount is made slave | |
1494 | * of the same master as that of the source mount. The cloned mount | |
1495 | * is marked as 'shared and slave'. | |
1496 | * (*) the cloned mount is made a slave of the same master as that of the | |
1497 | * source mount. | |
1498 | * | |
1499 | * --------------------------------------------------------------------------- | |
1500 | * | MOVE MOUNT OPERATION | | |
1501 | * |************************************************************************** | |
1502 | * | source-->| shared | private | slave | unbindable | | |
1503 | * | dest | | | | | | |
1504 | * | | | | | | | | |
1505 | * | v | | | | | | |
1506 | * |************************************************************************** | |
1507 | * | shared | shared (+) | shared (+) | shared(+++) | invalid | | |
1508 | * | | | | | | | |
1509 | * |non-shared| shared (+*) | private | slave (*) | unbindable | | |
1510 | * *************************************************************************** | |
1511 | * | |
1512 | * (+) the mount is moved to the destination. And is then propagated to | |
1513 | * all the mounts in the propagation tree of the destination mount. | |
1514 | * (+*) the mount is moved to the destination. | |
1515 | * (+++) the mount is moved to the destination and is then propagated to | |
1516 | * all the mounts belonging to the destination mount's propagation tree. | |
1517 | * the mount is marked as 'shared and slave'. | |
1518 | * (*) the mount continues to be a slave at the new location. | |
1519 | * | |
1520 | * if the source mount is a tree, the operations explained above is | |
1521 | * applied to each mount in the tree. | |
1522 | * Must be called without spinlocks held, since this function can sleep | |
1523 | * in allocations. | |
1524 | */ | |
1525 | static int attach_recursive_mnt(struct mount *source_mnt, | |
1526 | struct path *path, struct path *parent_path) | |
1527 | { | |
1528 | LIST_HEAD(tree_list); | |
1529 | struct mount *dest_mnt = real_mount(path->mnt); | |
1530 | struct dentry *dest_dentry = path->dentry; | |
1531 | struct mount *child, *p; | |
1532 | int err; | |
1533 | ||
1534 | if (IS_MNT_SHARED(dest_mnt)) { | |
1535 | err = invent_group_ids(source_mnt, true); | |
1536 | if (err) | |
1537 | goto out; | |
1538 | } | |
1539 | err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list); | |
1540 | if (err) | |
1541 | goto out_cleanup_ids; | |
1542 | ||
1543 | br_write_lock(&vfsmount_lock); | |
1544 | ||
1545 | if (IS_MNT_SHARED(dest_mnt)) { | |
1546 | for (p = source_mnt; p; p = next_mnt(p, source_mnt)) | |
1547 | set_mnt_shared(p); | |
1548 | } | |
1549 | if (parent_path) { | |
1550 | detach_mnt(source_mnt, parent_path); | |
1551 | attach_mnt(source_mnt, path); | |
1552 | touch_mnt_namespace(source_mnt->mnt_ns); | |
1553 | } else { | |
1554 | mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt); | |
1555 | commit_tree(source_mnt); | |
1556 | } | |
1557 | ||
1558 | list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { | |
1559 | list_del_init(&child->mnt_hash); | |
1560 | commit_tree(child); | |
1561 | } | |
1562 | br_write_unlock(&vfsmount_lock); | |
1563 | ||
1564 | return 0; | |
1565 | ||
1566 | out_cleanup_ids: | |
1567 | if (IS_MNT_SHARED(dest_mnt)) | |
1568 | cleanup_group_ids(source_mnt, NULL); | |
1569 | out: | |
1570 | return err; | |
1571 | } | |
1572 | ||
1573 | static int lock_mount(struct path *path) | |
1574 | { | |
1575 | struct vfsmount *mnt; | |
1576 | retry: | |
1577 | mutex_lock(&path->dentry->d_inode->i_mutex); | |
1578 | if (unlikely(cant_mount(path->dentry))) { | |
1579 | mutex_unlock(&path->dentry->d_inode->i_mutex); | |
1580 | return -ENOENT; | |
1581 | } | |
1582 | down_write(&namespace_sem); | |
1583 | mnt = lookup_mnt(path); | |
1584 | if (likely(!mnt)) | |
1585 | return 0; | |
1586 | up_write(&namespace_sem); | |
1587 | mutex_unlock(&path->dentry->d_inode->i_mutex); | |
1588 | path_put(path); | |
1589 | path->mnt = mnt; | |
1590 | path->dentry = dget(mnt->mnt_root); | |
1591 | goto retry; | |
1592 | } | |
1593 | ||
1594 | static void unlock_mount(struct path *path) | |
1595 | { | |
1596 | up_write(&namespace_sem); | |
1597 | mutex_unlock(&path->dentry->d_inode->i_mutex); | |
1598 | } | |
1599 | ||
1600 | static int graft_tree(struct mount *mnt, struct path *path) | |
1601 | { | |
1602 | if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER) | |
1603 | return -EINVAL; | |
1604 | ||
1605 | if (S_ISDIR(path->dentry->d_inode->i_mode) != | |
1606 | S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode)) | |
1607 | return -ENOTDIR; | |
1608 | ||
1609 | if (d_unlinked(path->dentry)) | |
1610 | return -ENOENT; | |
1611 | ||
1612 | return attach_recursive_mnt(mnt, path, NULL); | |
1613 | } | |
1614 | ||
1615 | /* | |
1616 | * Sanity check the flags to change_mnt_propagation. | |
1617 | */ | |
1618 | ||
1619 | static int flags_to_propagation_type(int flags) | |
1620 | { | |
1621 | int type = flags & ~(MS_REC | MS_SILENT); | |
1622 | ||
1623 | /* Fail if any non-propagation flags are set */ | |
1624 | if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) | |
1625 | return 0; | |
1626 | /* Only one propagation flag should be set */ | |
1627 | if (!is_power_of_2(type)) | |
1628 | return 0; | |
1629 | return type; | |
1630 | } | |
1631 | ||
1632 | /* | |
1633 | * recursively change the type of the mountpoint. | |
1634 | */ | |
1635 | static int do_change_type(struct path *path, int flag) | |
1636 | { | |
1637 | struct mount *m; | |
1638 | struct mount *mnt = real_mount(path->mnt); | |
1639 | int recurse = flag & MS_REC; | |
1640 | int type; | |
1641 | int err = 0; | |
1642 | ||
1643 | if (!may_mount()) | |
1644 | return -EPERM; | |
1645 | ||
1646 | if (path->dentry != path->mnt->mnt_root) | |
1647 | return -EINVAL; | |
1648 | ||
1649 | type = flags_to_propagation_type(flag); | |
1650 | if (!type) | |
1651 | return -EINVAL; | |
1652 | ||
1653 | down_write(&namespace_sem); | |
1654 | if (type == MS_SHARED) { | |
1655 | err = invent_group_ids(mnt, recurse); | |
1656 | if (err) | |
1657 | goto out_unlock; | |
1658 | } | |
1659 | ||
1660 | br_write_lock(&vfsmount_lock); | |
1661 | for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) | |
1662 | change_mnt_propagation(m, type); | |
1663 | br_write_unlock(&vfsmount_lock); | |
1664 | ||
1665 | out_unlock: | |
1666 | up_write(&namespace_sem); | |
1667 | return err; | |
1668 | } | |
1669 | ||
1670 | /* | |
1671 | * do loopback mount. | |
1672 | */ | |
1673 | static int do_loopback(struct path *path, const char *old_name, | |
1674 | int recurse) | |
1675 | { | |
1676 | LIST_HEAD(umount_list); | |
1677 | struct path old_path; | |
1678 | struct mount *mnt = NULL, *old; | |
1679 | int err = mount_is_safe(path); | |
1680 | if (err) | |
1681 | return err; | |
1682 | if (!old_name || !*old_name) | |
1683 | return -EINVAL; | |
1684 | err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); | |
1685 | if (err) | |
1686 | return err; | |
1687 | ||
1688 | err = -EINVAL; | |
1689 | if (mnt_ns_loop(&old_path)) | |
1690 | goto out; | |
1691 | ||
1692 | err = lock_mount(path); | |
1693 | if (err) | |
1694 | goto out; | |
1695 | ||
1696 | old = real_mount(old_path.mnt); | |
1697 | ||
1698 | err = -EINVAL; | |
1699 | if (IS_MNT_UNBINDABLE(old)) | |
1700 | goto out2; | |
1701 | ||
1702 | if (!check_mnt(real_mount(path->mnt)) || !check_mnt(old)) | |
1703 | goto out2; | |
1704 | ||
1705 | if (recurse) | |
1706 | mnt = copy_tree(old, old_path.dentry, 0); | |
1707 | else | |
1708 | mnt = clone_mnt(old, old_path.dentry, 0); | |
1709 | ||
1710 | if (IS_ERR(mnt)) { | |
1711 | err = PTR_ERR(mnt); | |
1712 | goto out; | |
1713 | } | |
1714 | ||
1715 | err = graft_tree(mnt, path); | |
1716 | if (err) { | |
1717 | br_write_lock(&vfsmount_lock); | |
1718 | umount_tree(mnt, 0, &umount_list); | |
1719 | br_write_unlock(&vfsmount_lock); | |
1720 | } | |
1721 | out2: | |
1722 | unlock_mount(path); | |
1723 | release_mounts(&umount_list); | |
1724 | out: | |
1725 | path_put(&old_path); | |
1726 | return err; | |
1727 | } | |
1728 | ||
1729 | static int change_mount_flags(struct vfsmount *mnt, int ms_flags) | |
1730 | { | |
1731 | int error = 0; | |
1732 | int readonly_request = 0; | |
1733 | ||
1734 | if (ms_flags & MS_RDONLY) | |
1735 | readonly_request = 1; | |
1736 | if (readonly_request == __mnt_is_readonly(mnt)) | |
1737 | return 0; | |
1738 | ||
1739 | if (readonly_request) | |
1740 | error = mnt_make_readonly(real_mount(mnt)); | |
1741 | else | |
1742 | __mnt_unmake_readonly(real_mount(mnt)); | |
1743 | return error; | |
1744 | } | |
1745 | ||
1746 | /* | |
1747 | * change filesystem flags. dir should be a physical root of filesystem. | |
1748 | * If you've mounted a non-root directory somewhere and want to do remount | |
1749 | * on it - tough luck. | |
1750 | */ | |
1751 | static int do_remount(struct path *path, int flags, int mnt_flags, | |
1752 | void *data) | |
1753 | { | |
1754 | int err; | |
1755 | struct super_block *sb = path->mnt->mnt_sb; | |
1756 | struct mount *mnt = real_mount(path->mnt); | |
1757 | ||
1758 | if (!capable(CAP_SYS_ADMIN)) | |
1759 | return -EPERM; | |
1760 | ||
1761 | if (!check_mnt(mnt)) | |
1762 | return -EINVAL; | |
1763 | ||
1764 | if (path->dentry != path->mnt->mnt_root) | |
1765 | return -EINVAL; | |
1766 | ||
1767 | err = security_sb_remount(sb, data); | |
1768 | if (err) | |
1769 | return err; | |
1770 | ||
1771 | down_write(&sb->s_umount); | |
1772 | if (flags & MS_BIND) | |
1773 | err = change_mount_flags(path->mnt, flags); | |
1774 | else | |
1775 | err = do_remount_sb(sb, flags, data, 0); | |
1776 | if (!err) { | |
1777 | br_write_lock(&vfsmount_lock); | |
1778 | mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK; | |
1779 | mnt->mnt.mnt_flags = mnt_flags; | |
1780 | br_write_unlock(&vfsmount_lock); | |
1781 | } | |
1782 | up_write(&sb->s_umount); | |
1783 | if (!err) { | |
1784 | br_write_lock(&vfsmount_lock); | |
1785 | touch_mnt_namespace(mnt->mnt_ns); | |
1786 | br_write_unlock(&vfsmount_lock); | |
1787 | } | |
1788 | return err; | |
1789 | } | |
1790 | ||
1791 | static inline int tree_contains_unbindable(struct mount *mnt) | |
1792 | { | |
1793 | struct mount *p; | |
1794 | for (p = mnt; p; p = next_mnt(p, mnt)) { | |
1795 | if (IS_MNT_UNBINDABLE(p)) | |
1796 | return 1; | |
1797 | } | |
1798 | return 0; | |
1799 | } | |
1800 | ||
1801 | static int do_move_mount(struct path *path, const char *old_name) | |
1802 | { | |
1803 | struct path old_path, parent_path; | |
1804 | struct mount *p; | |
1805 | struct mount *old; | |
1806 | int err = 0; | |
1807 | if (!may_mount()) | |
1808 | return -EPERM; | |
1809 | if (!old_name || !*old_name) | |
1810 | return -EINVAL; | |
1811 | err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); | |
1812 | if (err) | |
1813 | return err; | |
1814 | ||
1815 | err = lock_mount(path); | |
1816 | if (err < 0) | |
1817 | goto out; | |
1818 | ||
1819 | old = real_mount(old_path.mnt); | |
1820 | p = real_mount(path->mnt); | |
1821 | ||
1822 | err = -EINVAL; | |
1823 | if (!check_mnt(p) || !check_mnt(old)) | |
1824 | goto out1; | |
1825 | ||
1826 | if (d_unlinked(path->dentry)) | |
1827 | goto out1; | |
1828 | ||
1829 | err = -EINVAL; | |
1830 | if (old_path.dentry != old_path.mnt->mnt_root) | |
1831 | goto out1; | |
1832 | ||
1833 | if (!mnt_has_parent(old)) | |
1834 | goto out1; | |
1835 | ||
1836 | if (S_ISDIR(path->dentry->d_inode->i_mode) != | |
1837 | S_ISDIR(old_path.dentry->d_inode->i_mode)) | |
1838 | goto out1; | |
1839 | /* | |
1840 | * Don't move a mount residing in a shared parent. | |
1841 | */ | |
1842 | if (IS_MNT_SHARED(old->mnt_parent)) | |
1843 | goto out1; | |
1844 | /* | |
1845 | * Don't move a mount tree containing unbindable mounts to a destination | |
1846 | * mount which is shared. | |
1847 | */ | |
1848 | if (IS_MNT_SHARED(p) && tree_contains_unbindable(old)) | |
1849 | goto out1; | |
1850 | err = -ELOOP; | |
1851 | for (; mnt_has_parent(p); p = p->mnt_parent) | |
1852 | if (p == old) | |
1853 | goto out1; | |
1854 | ||
1855 | err = attach_recursive_mnt(old, path, &parent_path); | |
1856 | if (err) | |
1857 | goto out1; | |
1858 | ||
1859 | /* if the mount is moved, it should no longer be expire | |
1860 | * automatically */ | |
1861 | list_del_init(&old->mnt_expire); | |
1862 | out1: | |
1863 | unlock_mount(path); | |
1864 | out: | |
1865 | if (!err) | |
1866 | path_put(&parent_path); | |
1867 | path_put(&old_path); | |
1868 | return err; | |
1869 | } | |
1870 | ||
1871 | static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype) | |
1872 | { | |
1873 | int err; | |
1874 | const char *subtype = strchr(fstype, '.'); | |
1875 | if (subtype) { | |
1876 | subtype++; | |
1877 | err = -EINVAL; | |
1878 | if (!subtype[0]) | |
1879 | goto err; | |
1880 | } else | |
1881 | subtype = ""; | |
1882 | ||
1883 | mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL); | |
1884 | err = -ENOMEM; | |
1885 | if (!mnt->mnt_sb->s_subtype) | |
1886 | goto err; | |
1887 | return mnt; | |
1888 | ||
1889 | err: | |
1890 | mntput(mnt); | |
1891 | return ERR_PTR(err); | |
1892 | } | |
1893 | ||
1894 | /* | |
1895 | * add a mount into a namespace's mount tree | |
1896 | */ | |
1897 | static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags) | |
1898 | { | |
1899 | int err; | |
1900 | ||
1901 | mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL); | |
1902 | ||
1903 | err = lock_mount(path); | |
1904 | if (err) | |
1905 | return err; | |
1906 | ||
1907 | err = -EINVAL; | |
1908 | if (unlikely(!check_mnt(real_mount(path->mnt)))) { | |
1909 | /* that's acceptable only for automounts done in private ns */ | |
1910 | if (!(mnt_flags & MNT_SHRINKABLE)) | |
1911 | goto unlock; | |
1912 | /* ... and for those we'd better have mountpoint still alive */ | |
1913 | if (!real_mount(path->mnt)->mnt_ns) | |
1914 | goto unlock; | |
1915 | } | |
1916 | ||
1917 | /* Refuse the same filesystem on the same mount point */ | |
1918 | err = -EBUSY; | |
1919 | if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && | |
1920 | path->mnt->mnt_root == path->dentry) | |
1921 | goto unlock; | |
1922 | ||
1923 | err = -EINVAL; | |
1924 | if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode)) | |
1925 | goto unlock; | |
1926 | ||
1927 | newmnt->mnt.mnt_flags = mnt_flags; | |
1928 | err = graft_tree(newmnt, path); | |
1929 | ||
1930 | unlock: | |
1931 | unlock_mount(path); | |
1932 | return err; | |
1933 | } | |
1934 | ||
1935 | /* | |
1936 | * create a new mount for userspace and request it to be added into the | |
1937 | * namespace's tree | |
1938 | */ | |
1939 | static int do_new_mount(struct path *path, const char *fstype, int flags, | |
1940 | int mnt_flags, const char *name, void *data) | |
1941 | { | |
1942 | struct file_system_type *type; | |
1943 | struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; | |
1944 | struct vfsmount *mnt; | |
1945 | int err; | |
1946 | ||
1947 | if (!fstype) | |
1948 | return -EINVAL; | |
1949 | ||
1950 | if (!may_mount()) | |
1951 | return -EPERM; | |
1952 | ||
1953 | type = get_fs_type(fstype); | |
1954 | if (!type) | |
1955 | return -ENODEV; | |
1956 | ||
1957 | if (user_ns != &init_user_ns) { | |
1958 | if (!(type->fs_flags & FS_USERNS_MOUNT)) { | |
1959 | put_filesystem(type); | |
1960 | return -EPERM; | |
1961 | } | |
1962 | /* Only in special cases allow devices from mounts | |
1963 | * created outside the initial user namespace. | |
1964 | */ | |
1965 | if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) { | |
1966 | flags |= MS_NODEV; | |
1967 | mnt_flags |= MNT_NODEV; | |
1968 | } | |
1969 | } | |
1970 | ||
1971 | mnt = vfs_kern_mount(type, flags, name, data); | |
1972 | if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && | |
1973 | !mnt->mnt_sb->s_subtype) | |
1974 | mnt = fs_set_subtype(mnt, fstype); | |
1975 | ||
1976 | put_filesystem(type); | |
1977 | if (IS_ERR(mnt)) | |
1978 | return PTR_ERR(mnt); | |
1979 | ||
1980 | err = do_add_mount(real_mount(mnt), path, mnt_flags); | |
1981 | if (err) | |
1982 | mntput(mnt); | |
1983 | return err; | |
1984 | } | |
1985 | ||
1986 | int finish_automount(struct vfsmount *m, struct path *path) | |
1987 | { | |
1988 | struct mount *mnt = real_mount(m); | |
1989 | int err; | |
1990 | /* The new mount record should have at least 2 refs to prevent it being | |
1991 | * expired before we get a chance to add it | |
1992 | */ | |
1993 | BUG_ON(mnt_get_count(mnt) < 2); | |
1994 | ||
1995 | if (m->mnt_sb == path->mnt->mnt_sb && | |
1996 | m->mnt_root == path->dentry) { | |
1997 | err = -ELOOP; | |
1998 | goto fail; | |
1999 | } | |
2000 | ||
2001 | err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE); | |
2002 | if (!err) | |
2003 | return 0; | |
2004 | fail: | |
2005 | /* remove m from any expiration list it may be on */ | |
2006 | if (!list_empty(&mnt->mnt_expire)) { | |
2007 | down_write(&namespace_sem); | |
2008 | br_write_lock(&vfsmount_lock); | |
2009 | list_del_init(&mnt->mnt_expire); | |
2010 | br_write_unlock(&vfsmount_lock); | |
2011 | up_write(&namespace_sem); | |
2012 | } | |
2013 | mntput(m); | |
2014 | mntput(m); | |
2015 | return err; | |
2016 | } | |
2017 | ||
2018 | /** | |
2019 | * mnt_set_expiry - Put a mount on an expiration list | |
2020 | * @mnt: The mount to list. | |
2021 | * @expiry_list: The list to add the mount to. | |
2022 | */ | |
2023 | void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list) | |
2024 | { | |
2025 | down_write(&namespace_sem); | |
2026 | br_write_lock(&vfsmount_lock); | |
2027 | ||
2028 | list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list); | |
2029 | ||
2030 | br_write_unlock(&vfsmount_lock); | |
2031 | up_write(&namespace_sem); | |
2032 | } | |
2033 | EXPORT_SYMBOL(mnt_set_expiry); | |
2034 | ||
2035 | /* | |
2036 | * process a list of expirable mountpoints with the intent of discarding any | |
2037 | * mountpoints that aren't in use and haven't been touched since last we came | |
2038 | * here | |
2039 | */ | |
2040 | void mark_mounts_for_expiry(struct list_head *mounts) | |
2041 | { | |
2042 | struct mount *mnt, *next; | |
2043 | LIST_HEAD(graveyard); | |
2044 | LIST_HEAD(umounts); | |
2045 | ||
2046 | if (list_empty(mounts)) | |
2047 | return; | |
2048 | ||
2049 | down_write(&namespace_sem); | |
2050 | br_write_lock(&vfsmount_lock); | |
2051 | ||
2052 | /* extract from the expiration list every vfsmount that matches the | |
2053 | * following criteria: | |
2054 | * - only referenced by its parent vfsmount | |
2055 | * - still marked for expiry (marked on the last call here; marks are | |
2056 | * cleared by mntput()) | |
2057 | */ | |
2058 | list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { | |
2059 | if (!xchg(&mnt->mnt_expiry_mark, 1) || | |
2060 | propagate_mount_busy(mnt, 1)) | |
2061 | continue; | |
2062 | list_move(&mnt->mnt_expire, &graveyard); | |
2063 | } | |
2064 | while (!list_empty(&graveyard)) { | |
2065 | mnt = list_first_entry(&graveyard, struct mount, mnt_expire); | |
2066 | touch_mnt_namespace(mnt->mnt_ns); | |
2067 | umount_tree(mnt, 1, &umounts); | |
2068 | } | |
2069 | br_write_unlock(&vfsmount_lock); | |
2070 | up_write(&namespace_sem); | |
2071 | ||
2072 | release_mounts(&umounts); | |
2073 | } | |
2074 | ||
2075 | EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); | |
2076 | ||
2077 | /* | |
2078 | * Ripoff of 'select_parent()' | |
2079 | * | |
2080 | * search the list of submounts for a given mountpoint, and move any | |
2081 | * shrinkable submounts to the 'graveyard' list. | |
2082 | */ | |
2083 | static int select_submounts(struct mount *parent, struct list_head *graveyard) | |
2084 | { | |
2085 | struct mount *this_parent = parent; | |
2086 | struct list_head *next; | |
2087 | int found = 0; | |
2088 | ||
2089 | repeat: | |
2090 | next = this_parent->mnt_mounts.next; | |
2091 | resume: | |
2092 | while (next != &this_parent->mnt_mounts) { | |
2093 | struct list_head *tmp = next; | |
2094 | struct mount *mnt = list_entry(tmp, struct mount, mnt_child); | |
2095 | ||
2096 | next = tmp->next; | |
2097 | if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE)) | |
2098 | continue; | |
2099 | /* | |
2100 | * Descend a level if the d_mounts list is non-empty. | |
2101 | */ | |
2102 | if (!list_empty(&mnt->mnt_mounts)) { | |
2103 | this_parent = mnt; | |
2104 | goto repeat; | |
2105 | } | |
2106 | ||
2107 | if (!propagate_mount_busy(mnt, 1)) { | |
2108 | list_move_tail(&mnt->mnt_expire, graveyard); | |
2109 | found++; | |
2110 | } | |
2111 | } | |
2112 | /* | |
2113 | * All done at this level ... ascend and resume the search | |
2114 | */ | |
2115 | if (this_parent != parent) { | |
2116 | next = this_parent->mnt_child.next; | |
2117 | this_parent = this_parent->mnt_parent; | |
2118 | goto resume; | |
2119 | } | |
2120 | return found; | |
2121 | } | |
2122 | ||
2123 | /* | |
2124 | * process a list of expirable mountpoints with the intent of discarding any | |
2125 | * submounts of a specific parent mountpoint | |
2126 | * | |
2127 | * vfsmount_lock must be held for write | |
2128 | */ | |
2129 | static void shrink_submounts(struct mount *mnt, struct list_head *umounts) | |
2130 | { | |
2131 | LIST_HEAD(graveyard); | |
2132 | struct mount *m; | |
2133 | ||
2134 | /* extract submounts of 'mountpoint' from the expiration list */ | |
2135 | while (select_submounts(mnt, &graveyard)) { | |
2136 | while (!list_empty(&graveyard)) { | |
2137 | m = list_first_entry(&graveyard, struct mount, | |
2138 | mnt_expire); | |
2139 | touch_mnt_namespace(m->mnt_ns); | |
2140 | umount_tree(m, 1, umounts); | |
2141 | } | |
2142 | } | |
2143 | } | |
2144 | ||
2145 | /* | |
2146 | * Some copy_from_user() implementations do not return the exact number of | |
2147 | * bytes remaining to copy on a fault. But copy_mount_options() requires that. | |
2148 | * Note that this function differs from copy_from_user() in that it will oops | |
2149 | * on bad values of `to', rather than returning a short copy. | |
2150 | */ | |
2151 | static long exact_copy_from_user(void *to, const void __user * from, | |
2152 | unsigned long n) | |
2153 | { | |
2154 | char *t = to; | |
2155 | const char __user *f = from; | |
2156 | char c; | |
2157 | ||
2158 | if (!access_ok(VERIFY_READ, from, n)) | |
2159 | return n; | |
2160 | ||
2161 | while (n) { | |
2162 | if (__get_user(c, f)) { | |
2163 | memset(t, 0, n); | |
2164 | break; | |
2165 | } | |
2166 | *t++ = c; | |
2167 | f++; | |
2168 | n--; | |
2169 | } | |
2170 | return n; | |
2171 | } | |
2172 | ||
2173 | int copy_mount_options(const void __user * data, unsigned long *where) | |
2174 | { | |
2175 | int i; | |
2176 | unsigned long page; | |
2177 | unsigned long size; | |
2178 | ||
2179 | *where = 0; | |
2180 | if (!data) | |
2181 | return 0; | |
2182 | ||
2183 | if (!(page = __get_free_page(GFP_KERNEL))) | |
2184 | return -ENOMEM; | |
2185 | ||
2186 | /* We only care that *some* data at the address the user | |
2187 | * gave us is valid. Just in case, we'll zero | |
2188 | * the remainder of the page. | |
2189 | */ | |
2190 | /* copy_from_user cannot cross TASK_SIZE ! */ | |
2191 | size = TASK_SIZE - (unsigned long)data; | |
2192 | if (size > PAGE_SIZE) | |
2193 | size = PAGE_SIZE; | |
2194 | ||
2195 | i = size - exact_copy_from_user((void *)page, data, size); | |
2196 | if (!i) { | |
2197 | free_page(page); | |
2198 | return -EFAULT; | |
2199 | } | |
2200 | if (i != PAGE_SIZE) | |
2201 | memset((char *)page + i, 0, PAGE_SIZE - i); | |
2202 | *where = page; | |
2203 | return 0; | |
2204 | } | |
2205 | ||
2206 | int copy_mount_string(const void __user *data, char **where) | |
2207 | { | |
2208 | char *tmp; | |
2209 | ||
2210 | if (!data) { | |
2211 | *where = NULL; | |
2212 | return 0; | |
2213 | } | |
2214 | ||
2215 | tmp = strndup_user(data, PAGE_SIZE); | |
2216 | if (IS_ERR(tmp)) | |
2217 | return PTR_ERR(tmp); | |
2218 | ||
2219 | *where = tmp; | |
2220 | return 0; | |
2221 | } | |
2222 | ||
2223 | /* | |
2224 | * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to | |
2225 | * be given to the mount() call (ie: read-only, no-dev, no-suid etc). | |
2226 | * | |
2227 | * data is a (void *) that can point to any structure up to | |
2228 | * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent | |
2229 | * information (or be NULL). | |
2230 | * | |
2231 | * Pre-0.97 versions of mount() didn't have a flags word. | |
2232 | * When the flags word was introduced its top half was required | |
2233 | * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. | |
2234 | * Therefore, if this magic number is present, it carries no information | |
2235 | * and must be discarded. | |
2236 | */ | |
2237 | long do_mount(const char *dev_name, const char *dir_name, | |
2238 | const char *type_page, unsigned long flags, void *data_page) | |
2239 | { | |
2240 | struct path path; | |
2241 | int retval = 0; | |
2242 | int mnt_flags = 0; | |
2243 | ||
2244 | /* Discard magic */ | |
2245 | if ((flags & MS_MGC_MSK) == MS_MGC_VAL) | |
2246 | flags &= ~MS_MGC_MSK; | |
2247 | ||
2248 | /* Basic sanity checks */ | |
2249 | ||
2250 | if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) | |
2251 | return -EINVAL; | |
2252 | ||
2253 | if (data_page) | |
2254 | ((char *)data_page)[PAGE_SIZE - 1] = 0; | |
2255 | ||
2256 | /* ... and get the mountpoint */ | |
2257 | retval = kern_path(dir_name, LOOKUP_FOLLOW, &path); | |
2258 | if (retval) | |
2259 | return retval; | |
2260 | ||
2261 | retval = security_sb_mount(dev_name, &path, | |
2262 | type_page, flags, data_page); | |
2263 | if (retval) | |
2264 | goto dput_out; | |
2265 | ||
2266 | /* Default to relatime unless overriden */ | |
2267 | if (!(flags & MS_NOATIME)) | |
2268 | mnt_flags |= MNT_RELATIME; | |
2269 | ||
2270 | /* Separate the per-mountpoint flags */ | |
2271 | if (flags & MS_NOSUID) | |
2272 | mnt_flags |= MNT_NOSUID; | |
2273 | if (flags & MS_NODEV) | |
2274 | mnt_flags |= MNT_NODEV; | |
2275 | if (flags & MS_NOEXEC) | |
2276 | mnt_flags |= MNT_NOEXEC; | |
2277 | if (flags & MS_NOATIME) | |
2278 | mnt_flags |= MNT_NOATIME; | |
2279 | if (flags & MS_NODIRATIME) | |
2280 | mnt_flags |= MNT_NODIRATIME; | |
2281 | if (flags & MS_STRICTATIME) | |
2282 | mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); | |
2283 | if (flags & MS_RDONLY) | |
2284 | mnt_flags |= MNT_READONLY; | |
2285 | ||
2286 | flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN | | |
2287 | MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT | | |
2288 | MS_STRICTATIME); | |
2289 | ||
2290 | if (flags & MS_REMOUNT) | |
2291 | retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags, | |
2292 | data_page); | |
2293 | else if (flags & MS_BIND) | |
2294 | retval = do_loopback(&path, dev_name, flags & MS_REC); | |
2295 | else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) | |
2296 | retval = do_change_type(&path, flags); | |
2297 | else if (flags & MS_MOVE) | |
2298 | retval = do_move_mount(&path, dev_name); | |
2299 | else | |
2300 | retval = do_new_mount(&path, type_page, flags, mnt_flags, | |
2301 | dev_name, data_page); | |
2302 | dput_out: | |
2303 | path_put(&path); | |
2304 | return retval; | |
2305 | } | |
2306 | ||
2307 | static void free_mnt_ns(struct mnt_namespace *ns) | |
2308 | { | |
2309 | proc_free_inum(ns->proc_inum); | |
2310 | put_user_ns(ns->user_ns); | |
2311 | kfree(ns); | |
2312 | } | |
2313 | ||
2314 | /* | |
2315 | * Assign a sequence number so we can detect when we attempt to bind | |
2316 | * mount a reference to an older mount namespace into the current | |
2317 | * mount namespace, preventing reference counting loops. A 64bit | |
2318 | * number incrementing at 10Ghz will take 12,427 years to wrap which | |
2319 | * is effectively never, so we can ignore the possibility. | |
2320 | */ | |
2321 | static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1); | |
2322 | ||
2323 | static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns) | |
2324 | { | |
2325 | struct mnt_namespace *new_ns; | |
2326 | int ret; | |
2327 | ||
2328 | new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); | |
2329 | if (!new_ns) | |
2330 | return ERR_PTR(-ENOMEM); | |
2331 | ret = proc_alloc_inum(&new_ns->proc_inum); | |
2332 | if (ret) { | |
2333 | kfree(new_ns); | |
2334 | return ERR_PTR(ret); | |
2335 | } | |
2336 | new_ns->seq = atomic64_add_return(1, &mnt_ns_seq); | |
2337 | atomic_set(&new_ns->count, 1); | |
2338 | new_ns->root = NULL; | |
2339 | INIT_LIST_HEAD(&new_ns->list); | |
2340 | init_waitqueue_head(&new_ns->poll); | |
2341 | new_ns->event = 0; | |
2342 | new_ns->user_ns = get_user_ns(user_ns); | |
2343 | return new_ns; | |
2344 | } | |
2345 | ||
2346 | /* | |
2347 | * Allocate a new namespace structure and populate it with contents | |
2348 | * copied from the namespace of the passed in task structure. | |
2349 | */ | |
2350 | static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns, | |
2351 | struct user_namespace *user_ns, struct fs_struct *fs) | |
2352 | { | |
2353 | struct mnt_namespace *new_ns; | |
2354 | struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; | |
2355 | struct mount *p, *q; | |
2356 | struct mount *old = mnt_ns->root; | |
2357 | struct mount *new; | |
2358 | int copy_flags; | |
2359 | ||
2360 | new_ns = alloc_mnt_ns(user_ns); | |
2361 | if (IS_ERR(new_ns)) | |
2362 | return new_ns; | |
2363 | ||
2364 | down_write(&namespace_sem); | |
2365 | /* First pass: copy the tree topology */ | |
2366 | copy_flags = CL_COPY_ALL | CL_EXPIRE; | |
2367 | if (user_ns != mnt_ns->user_ns) | |
2368 | copy_flags |= CL_SHARED_TO_SLAVE; | |
2369 | new = copy_tree(old, old->mnt.mnt_root, copy_flags); | |
2370 | if (IS_ERR(new)) { | |
2371 | up_write(&namespace_sem); | |
2372 | free_mnt_ns(new_ns); | |
2373 | return ERR_CAST(new); | |
2374 | } | |
2375 | new_ns->root = new; | |
2376 | br_write_lock(&vfsmount_lock); | |
2377 | list_add_tail(&new_ns->list, &new->mnt_list); | |
2378 | br_write_unlock(&vfsmount_lock); | |
2379 | ||
2380 | /* | |
2381 | * Second pass: switch the tsk->fs->* elements and mark new vfsmounts | |
2382 | * as belonging to new namespace. We have already acquired a private | |
2383 | * fs_struct, so tsk->fs->lock is not needed. | |
2384 | */ | |
2385 | p = old; | |
2386 | q = new; | |
2387 | while (p) { | |
2388 | q->mnt_ns = new_ns; | |
2389 | if (fs) { | |
2390 | if (&p->mnt == fs->root.mnt) { | |
2391 | fs->root.mnt = mntget(&q->mnt); | |
2392 | rootmnt = &p->mnt; | |
2393 | } | |
2394 | if (&p->mnt == fs->pwd.mnt) { | |
2395 | fs->pwd.mnt = mntget(&q->mnt); | |
2396 | pwdmnt = &p->mnt; | |
2397 | } | |
2398 | } | |
2399 | p = next_mnt(p, old); | |
2400 | q = next_mnt(q, new); | |
2401 | } | |
2402 | up_write(&namespace_sem); | |
2403 | ||
2404 | if (rootmnt) | |
2405 | mntput(rootmnt); | |
2406 | if (pwdmnt) | |
2407 | mntput(pwdmnt); | |
2408 | ||
2409 | return new_ns; | |
2410 | } | |
2411 | ||
2412 | struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, | |
2413 | struct user_namespace *user_ns, struct fs_struct *new_fs) | |
2414 | { | |
2415 | struct mnt_namespace *new_ns; | |
2416 | ||
2417 | BUG_ON(!ns); | |
2418 | get_mnt_ns(ns); | |
2419 | ||
2420 | if (!(flags & CLONE_NEWNS)) | |
2421 | return ns; | |
2422 | ||
2423 | new_ns = dup_mnt_ns(ns, user_ns, new_fs); | |
2424 | ||
2425 | put_mnt_ns(ns); | |
2426 | return new_ns; | |
2427 | } | |
2428 | ||
2429 | /** | |
2430 | * create_mnt_ns - creates a private namespace and adds a root filesystem | |
2431 | * @mnt: pointer to the new root filesystem mountpoint | |
2432 | */ | |
2433 | static struct mnt_namespace *create_mnt_ns(struct vfsmount *m) | |
2434 | { | |
2435 | struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns); | |
2436 | if (!IS_ERR(new_ns)) { | |
2437 | struct mount *mnt = real_mount(m); | |
2438 | mnt->mnt_ns = new_ns; | |
2439 | new_ns->root = mnt; | |
2440 | list_add(&new_ns->list, &mnt->mnt_list); | |
2441 | } else { | |
2442 | mntput(m); | |
2443 | } | |
2444 | return new_ns; | |
2445 | } | |
2446 | ||
2447 | struct dentry *mount_subtree(struct vfsmount *mnt, const char *name) | |
2448 | { | |
2449 | struct mnt_namespace *ns; | |
2450 | struct super_block *s; | |
2451 | struct path path; | |
2452 | int err; | |
2453 | ||
2454 | ns = create_mnt_ns(mnt); | |
2455 | if (IS_ERR(ns)) | |
2456 | return ERR_CAST(ns); | |
2457 | ||
2458 | err = vfs_path_lookup(mnt->mnt_root, mnt, | |
2459 | name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); | |
2460 | ||
2461 | put_mnt_ns(ns); | |
2462 | ||
2463 | if (err) | |
2464 | return ERR_PTR(err); | |
2465 | ||
2466 | /* trade a vfsmount reference for active sb one */ | |
2467 | s = path.mnt->mnt_sb; | |
2468 | atomic_inc(&s->s_active); | |
2469 | mntput(path.mnt); | |
2470 | /* lock the sucker */ | |
2471 | down_write(&s->s_umount); | |
2472 | /* ... and return the root of (sub)tree on it */ | |
2473 | return path.dentry; | |
2474 | } | |
2475 | EXPORT_SYMBOL(mount_subtree); | |
2476 | ||
2477 | SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, | |
2478 | char __user *, type, unsigned long, flags, void __user *, data) | |
2479 | { | |
2480 | int ret; | |
2481 | char *kernel_type; | |
2482 | struct filename *kernel_dir; | |
2483 | char *kernel_dev; | |
2484 | unsigned long data_page; | |
2485 | ||
2486 | ret = copy_mount_string(type, &kernel_type); | |
2487 | if (ret < 0) | |
2488 | goto out_type; | |
2489 | ||
2490 | kernel_dir = getname(dir_name); | |
2491 | if (IS_ERR(kernel_dir)) { | |
2492 | ret = PTR_ERR(kernel_dir); | |
2493 | goto out_dir; | |
2494 | } | |
2495 | ||
2496 | ret = copy_mount_string(dev_name, &kernel_dev); | |
2497 | if (ret < 0) | |
2498 | goto out_dev; | |
2499 | ||
2500 | ret = copy_mount_options(data, &data_page); | |
2501 | if (ret < 0) | |
2502 | goto out_data; | |
2503 | ||
2504 | ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags, | |
2505 | (void *) data_page); | |
2506 | ||
2507 | free_page(data_page); | |
2508 | out_data: | |
2509 | kfree(kernel_dev); | |
2510 | out_dev: | |
2511 | putname(kernel_dir); | |
2512 | out_dir: | |
2513 | kfree(kernel_type); | |
2514 | out_type: | |
2515 | return ret; | |
2516 | } | |
2517 | ||
2518 | /* | |
2519 | * Return true if path is reachable from root | |
2520 | * | |
2521 | * namespace_sem or vfsmount_lock is held | |
2522 | */ | |
2523 | bool is_path_reachable(struct mount *mnt, struct dentry *dentry, | |
2524 | const struct path *root) | |
2525 | { | |
2526 | while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) { | |
2527 | dentry = mnt->mnt_mountpoint; | |
2528 | mnt = mnt->mnt_parent; | |
2529 | } | |
2530 | return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry); | |
2531 | } | |
2532 | ||
2533 | int path_is_under(struct path *path1, struct path *path2) | |
2534 | { | |
2535 | int res; | |
2536 | br_read_lock(&vfsmount_lock); | |
2537 | res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2); | |
2538 | br_read_unlock(&vfsmount_lock); | |
2539 | return res; | |
2540 | } | |
2541 | EXPORT_SYMBOL(path_is_under); | |
2542 | ||
2543 | /* | |
2544 | * pivot_root Semantics: | |
2545 | * Moves the root file system of the current process to the directory put_old, | |
2546 | * makes new_root as the new root file system of the current process, and sets | |
2547 | * root/cwd of all processes which had them on the current root to new_root. | |
2548 | * | |
2549 | * Restrictions: | |
2550 | * The new_root and put_old must be directories, and must not be on the | |
2551 | * same file system as the current process root. The put_old must be | |
2552 | * underneath new_root, i.e. adding a non-zero number of /.. to the string | |
2553 | * pointed to by put_old must yield the same directory as new_root. No other | |
2554 | * file system may be mounted on put_old. After all, new_root is a mountpoint. | |
2555 | * | |
2556 | * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. | |
2557 | * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives | |
2558 | * in this situation. | |
2559 | * | |
2560 | * Notes: | |
2561 | * - we don't move root/cwd if they are not at the root (reason: if something | |
2562 | * cared enough to change them, it's probably wrong to force them elsewhere) | |
2563 | * - it's okay to pick a root that isn't the root of a file system, e.g. | |
2564 | * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, | |
2565 | * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root | |
2566 | * first. | |
2567 | */ | |
2568 | SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, | |
2569 | const char __user *, put_old) | |
2570 | { | |
2571 | struct path new, old, parent_path, root_parent, root; | |
2572 | struct mount *new_mnt, *root_mnt; | |
2573 | int error; | |
2574 | ||
2575 | if (!may_mount()) | |
2576 | return -EPERM; | |
2577 | ||
2578 | error = user_path_dir(new_root, &new); | |
2579 | if (error) | |
2580 | goto out0; | |
2581 | ||
2582 | error = user_path_dir(put_old, &old); | |
2583 | if (error) | |
2584 | goto out1; | |
2585 | ||
2586 | error = security_sb_pivotroot(&old, &new); | |
2587 | if (error) | |
2588 | goto out2; | |
2589 | ||
2590 | get_fs_root(current->fs, &root); | |
2591 | error = lock_mount(&old); | |
2592 | if (error) | |
2593 | goto out3; | |
2594 | ||
2595 | error = -EINVAL; | |
2596 | new_mnt = real_mount(new.mnt); | |
2597 | root_mnt = real_mount(root.mnt); | |
2598 | if (IS_MNT_SHARED(real_mount(old.mnt)) || | |
2599 | IS_MNT_SHARED(new_mnt->mnt_parent) || | |
2600 | IS_MNT_SHARED(root_mnt->mnt_parent)) | |
2601 | goto out4; | |
2602 | if (!check_mnt(root_mnt) || !check_mnt(new_mnt)) | |
2603 | goto out4; | |
2604 | error = -ENOENT; | |
2605 | if (d_unlinked(new.dentry)) | |
2606 | goto out4; | |
2607 | if (d_unlinked(old.dentry)) | |
2608 | goto out4; | |
2609 | error = -EBUSY; | |
2610 | if (new.mnt == root.mnt || | |
2611 | old.mnt == root.mnt) | |
2612 | goto out4; /* loop, on the same file system */ | |
2613 | error = -EINVAL; | |
2614 | if (root.mnt->mnt_root != root.dentry) | |
2615 | goto out4; /* not a mountpoint */ | |
2616 | if (!mnt_has_parent(root_mnt)) | |
2617 | goto out4; /* not attached */ | |
2618 | if (new.mnt->mnt_root != new.dentry) | |
2619 | goto out4; /* not a mountpoint */ | |
2620 | if (!mnt_has_parent(new_mnt)) | |
2621 | goto out4; /* not attached */ | |
2622 | /* make sure we can reach put_old from new_root */ | |
2623 | if (!is_path_reachable(real_mount(old.mnt), old.dentry, &new)) | |
2624 | goto out4; | |
2625 | br_write_lock(&vfsmount_lock); | |
2626 | detach_mnt(new_mnt, &parent_path); | |
2627 | detach_mnt(root_mnt, &root_parent); | |
2628 | /* mount old root on put_old */ | |
2629 | attach_mnt(root_mnt, &old); | |
2630 | /* mount new_root on / */ | |
2631 | attach_mnt(new_mnt, &root_parent); | |
2632 | touch_mnt_namespace(current->nsproxy->mnt_ns); | |
2633 | br_write_unlock(&vfsmount_lock); | |
2634 | chroot_fs_refs(&root, &new); | |
2635 | error = 0; | |
2636 | out4: | |
2637 | unlock_mount(&old); | |
2638 | if (!error) { | |
2639 | path_put(&root_parent); | |
2640 | path_put(&parent_path); | |
2641 | } | |
2642 | out3: | |
2643 | path_put(&root); | |
2644 | out2: | |
2645 | path_put(&old); | |
2646 | out1: | |
2647 | path_put(&new); | |
2648 | out0: | |
2649 | return error; | |
2650 | } | |
2651 | ||
2652 | static void __init init_mount_tree(void) | |
2653 | { | |
2654 | struct vfsmount *mnt; | |
2655 | struct mnt_namespace *ns; | |
2656 | struct path root; | |
2657 | struct file_system_type *type; | |
2658 | ||
2659 | type = get_fs_type("rootfs"); | |
2660 | if (!type) | |
2661 | panic("Can't find rootfs type"); | |
2662 | mnt = vfs_kern_mount(type, 0, "rootfs", NULL); | |
2663 | put_filesystem(type); | |
2664 | if (IS_ERR(mnt)) | |
2665 | panic("Can't create rootfs"); | |
2666 | ||
2667 | ns = create_mnt_ns(mnt); | |
2668 | if (IS_ERR(ns)) | |
2669 | panic("Can't allocate initial namespace"); | |
2670 | ||
2671 | init_task.nsproxy->mnt_ns = ns; | |
2672 | get_mnt_ns(ns); | |
2673 | ||
2674 | root.mnt = mnt; | |
2675 | root.dentry = mnt->mnt_root; | |
2676 | ||
2677 | set_fs_pwd(current->fs, &root); | |
2678 | set_fs_root(current->fs, &root); | |
2679 | } | |
2680 | ||
2681 | void __init mnt_init(void) | |
2682 | { | |
2683 | unsigned u; | |
2684 | int err; | |
2685 | ||
2686 | init_rwsem(&namespace_sem); | |
2687 | ||
2688 | mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount), | |
2689 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); | |
2690 | ||
2691 | mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); | |
2692 | ||
2693 | if (!mount_hashtable) | |
2694 | panic("Failed to allocate mount hash table\n"); | |
2695 | ||
2696 | printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE); | |
2697 | ||
2698 | for (u = 0; u < HASH_SIZE; u++) | |
2699 | INIT_LIST_HEAD(&mount_hashtable[u]); | |
2700 | ||
2701 | br_lock_init(&vfsmount_lock); | |
2702 | ||
2703 | err = sysfs_init(); | |
2704 | if (err) | |
2705 | printk(KERN_WARNING "%s: sysfs_init error: %d\n", | |
2706 | __func__, err); | |
2707 | fs_kobj = kobject_create_and_add("fs", NULL); | |
2708 | if (!fs_kobj) | |
2709 | printk(KERN_WARNING "%s: kobj create error\n", __func__); | |
2710 | init_rootfs(); | |
2711 | init_mount_tree(); | |
2712 | } | |
2713 | ||
2714 | void put_mnt_ns(struct mnt_namespace *ns) | |
2715 | { | |
2716 | LIST_HEAD(umount_list); | |
2717 | ||
2718 | if (!atomic_dec_and_test(&ns->count)) | |
2719 | return; | |
2720 | down_write(&namespace_sem); | |
2721 | br_write_lock(&vfsmount_lock); | |
2722 | umount_tree(ns->root, 0, &umount_list); | |
2723 | br_write_unlock(&vfsmount_lock); | |
2724 | up_write(&namespace_sem); | |
2725 | release_mounts(&umount_list); | |
2726 | free_mnt_ns(ns); | |
2727 | } | |
2728 | ||
2729 | struct vfsmount *kern_mount_data(struct file_system_type *type, void *data) | |
2730 | { | |
2731 | struct vfsmount *mnt; | |
2732 | mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data); | |
2733 | if (!IS_ERR(mnt)) { | |
2734 | /* | |
2735 | * it is a longterm mount, don't release mnt until | |
2736 | * we unmount before file sys is unregistered | |
2737 | */ | |
2738 | real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL; | |
2739 | } | |
2740 | return mnt; | |
2741 | } | |
2742 | EXPORT_SYMBOL_GPL(kern_mount_data); | |
2743 | ||
2744 | void kern_unmount(struct vfsmount *mnt) | |
2745 | { | |
2746 | /* release long term mount so mount point can be released */ | |
2747 | if (!IS_ERR_OR_NULL(mnt)) { | |
2748 | br_write_lock(&vfsmount_lock); | |
2749 | real_mount(mnt)->mnt_ns = NULL; | |
2750 | br_write_unlock(&vfsmount_lock); | |
2751 | mntput(mnt); | |
2752 | } | |
2753 | } | |
2754 | EXPORT_SYMBOL(kern_unmount); | |
2755 | ||
2756 | bool our_mnt(struct vfsmount *mnt) | |
2757 | { | |
2758 | return check_mnt(real_mount(mnt)); | |
2759 | } | |
2760 | ||
2761 | static void *mntns_get(struct task_struct *task) | |
2762 | { | |
2763 | struct mnt_namespace *ns = NULL; | |
2764 | struct nsproxy *nsproxy; | |
2765 | ||
2766 | rcu_read_lock(); | |
2767 | nsproxy = task_nsproxy(task); | |
2768 | if (nsproxy) { | |
2769 | ns = nsproxy->mnt_ns; | |
2770 | get_mnt_ns(ns); | |
2771 | } | |
2772 | rcu_read_unlock(); | |
2773 | ||
2774 | return ns; | |
2775 | } | |
2776 | ||
2777 | static void mntns_put(void *ns) | |
2778 | { | |
2779 | put_mnt_ns(ns); | |
2780 | } | |
2781 | ||
2782 | static int mntns_install(struct nsproxy *nsproxy, void *ns) | |
2783 | { | |
2784 | struct fs_struct *fs = current->fs; | |
2785 | struct mnt_namespace *mnt_ns = ns; | |
2786 | struct path root; | |
2787 | ||
2788 | if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) || | |
2789 | !nsown_capable(CAP_SYS_CHROOT) || | |
2790 | !nsown_capable(CAP_SYS_ADMIN)) | |
2791 | return -EPERM; | |
2792 | ||
2793 | if (fs->users != 1) | |
2794 | return -EINVAL; | |
2795 | ||
2796 | get_mnt_ns(mnt_ns); | |
2797 | put_mnt_ns(nsproxy->mnt_ns); | |
2798 | nsproxy->mnt_ns = mnt_ns; | |
2799 | ||
2800 | /* Find the root */ | |
2801 | root.mnt = &mnt_ns->root->mnt; | |
2802 | root.dentry = mnt_ns->root->mnt.mnt_root; | |
2803 | path_get(&root); | |
2804 | while(d_mountpoint(root.dentry) && follow_down_one(&root)) | |
2805 | ; | |
2806 | ||
2807 | /* Update the pwd and root */ | |
2808 | set_fs_pwd(fs, &root); | |
2809 | set_fs_root(fs, &root); | |
2810 | ||
2811 | path_put(&root); | |
2812 | return 0; | |
2813 | } | |
2814 | ||
2815 | static unsigned int mntns_inum(void *ns) | |
2816 | { | |
2817 | struct mnt_namespace *mnt_ns = ns; | |
2818 | return mnt_ns->proc_inum; | |
2819 | } | |
2820 | ||
2821 | const struct proc_ns_operations mntns_operations = { | |
2822 | .name = "mnt", | |
2823 | .type = CLONE_NEWNS, | |
2824 | .get = mntns_get, | |
2825 | .put = mntns_put, | |
2826 | .install = mntns_install, | |
2827 | .inum = mntns_inum, | |
2828 | }; |