]>
Commit | Line | Data |
---|---|---|
1 | /* | |
2 | * linux/fs/namespace.c | |
3 | * | |
4 | * (C) Copyright Al Viro 2000, 2001 | |
5 | * Released under GPL v2. | |
6 | * | |
7 | * Based on code from fs/super.c, copyright Linus Torvalds and others. | |
8 | * Heavily rewritten. | |
9 | */ | |
10 | ||
11 | #include <linux/syscalls.h> | |
12 | #include <linux/export.h> | |
13 | #include <linux/capability.h> | |
14 | #include <linux/mnt_namespace.h> | |
15 | #include <linux/user_namespace.h> | |
16 | #include <linux/namei.h> | |
17 | #include <linux/security.h> | |
18 | #include <linux/idr.h> | |
19 | #include <linux/acct.h> /* acct_auto_close_mnt */ | |
20 | #include <linux/init.h> /* init_rootfs */ | |
21 | #include <linux/fs_struct.h> /* get_fs_root et.al. */ | |
22 | #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */ | |
23 | #include <linux/uaccess.h> | |
24 | #include <linux/proc_ns.h> | |
25 | #include <linux/magic.h> | |
26 | #include "pnode.h" | |
27 | #include "internal.h" | |
28 | ||
29 | #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head)) | |
30 | #define HASH_SIZE (1UL << HASH_SHIFT) | |
31 | ||
32 | static int event; | |
33 | static DEFINE_IDA(mnt_id_ida); | |
34 | static DEFINE_IDA(mnt_group_ida); | |
35 | static DEFINE_SPINLOCK(mnt_id_lock); | |
36 | static int mnt_id_start = 0; | |
37 | static int mnt_group_start = 1; | |
38 | ||
39 | static struct list_head *mount_hashtable __read_mostly; | |
40 | static struct list_head *mountpoint_hashtable __read_mostly; | |
41 | static struct kmem_cache *mnt_cache __read_mostly; | |
42 | static DECLARE_RWSEM(namespace_sem); | |
43 | ||
44 | /* /sys/fs */ | |
45 | struct kobject *fs_kobj; | |
46 | EXPORT_SYMBOL_GPL(fs_kobj); | |
47 | ||
48 | /* | |
49 | * vfsmount lock may be taken for read to prevent changes to the | |
50 | * vfsmount hash, ie. during mountpoint lookups or walking back | |
51 | * up the tree. | |
52 | * | |
53 | * It should be taken for write in all cases where the vfsmount | |
54 | * tree or hash is modified or when a vfsmount structure is modified. | |
55 | */ | |
56 | DEFINE_BRLOCK(vfsmount_lock); | |
57 | ||
58 | static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) | |
59 | { | |
60 | unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); | |
61 | tmp += ((unsigned long)dentry / L1_CACHE_BYTES); | |
62 | tmp = tmp + (tmp >> HASH_SHIFT); | |
63 | return tmp & (HASH_SIZE - 1); | |
64 | } | |
65 | ||
66 | #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16) | |
67 | ||
68 | /* | |
69 | * allocation is serialized by namespace_sem, but we need the spinlock to | |
70 | * serialize with freeing. | |
71 | */ | |
72 | static int mnt_alloc_id(struct mount *mnt) | |
73 | { | |
74 | int res; | |
75 | ||
76 | retry: | |
77 | ida_pre_get(&mnt_id_ida, GFP_KERNEL); | |
78 | spin_lock(&mnt_id_lock); | |
79 | res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id); | |
80 | if (!res) | |
81 | mnt_id_start = mnt->mnt_id + 1; | |
82 | spin_unlock(&mnt_id_lock); | |
83 | if (res == -EAGAIN) | |
84 | goto retry; | |
85 | ||
86 | return res; | |
87 | } | |
88 | ||
89 | static void mnt_free_id(struct mount *mnt) | |
90 | { | |
91 | int id = mnt->mnt_id; | |
92 | spin_lock(&mnt_id_lock); | |
93 | ida_remove(&mnt_id_ida, id); | |
94 | if (mnt_id_start > id) | |
95 | mnt_id_start = id; | |
96 | spin_unlock(&mnt_id_lock); | |
97 | } | |
98 | ||
99 | /* | |
100 | * Allocate a new peer group ID | |
101 | * | |
102 | * mnt_group_ida is protected by namespace_sem | |
103 | */ | |
104 | static int mnt_alloc_group_id(struct mount *mnt) | |
105 | { | |
106 | int res; | |
107 | ||
108 | if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL)) | |
109 | return -ENOMEM; | |
110 | ||
111 | res = ida_get_new_above(&mnt_group_ida, | |
112 | mnt_group_start, | |
113 | &mnt->mnt_group_id); | |
114 | if (!res) | |
115 | mnt_group_start = mnt->mnt_group_id + 1; | |
116 | ||
117 | return res; | |
118 | } | |
119 | ||
120 | /* | |
121 | * Release a peer group ID | |
122 | */ | |
123 | void mnt_release_group_id(struct mount *mnt) | |
124 | { | |
125 | int id = mnt->mnt_group_id; | |
126 | ida_remove(&mnt_group_ida, id); | |
127 | if (mnt_group_start > id) | |
128 | mnt_group_start = id; | |
129 | mnt->mnt_group_id = 0; | |
130 | } | |
131 | ||
132 | /* | |
133 | * vfsmount lock must be held for read | |
134 | */ | |
135 | static inline void mnt_add_count(struct mount *mnt, int n) | |
136 | { | |
137 | #ifdef CONFIG_SMP | |
138 | this_cpu_add(mnt->mnt_pcp->mnt_count, n); | |
139 | #else | |
140 | preempt_disable(); | |
141 | mnt->mnt_count += n; | |
142 | preempt_enable(); | |
143 | #endif | |
144 | } | |
145 | ||
146 | /* | |
147 | * vfsmount lock must be held for write | |
148 | */ | |
149 | unsigned int mnt_get_count(struct mount *mnt) | |
150 | { | |
151 | #ifdef CONFIG_SMP | |
152 | unsigned int count = 0; | |
153 | int cpu; | |
154 | ||
155 | for_each_possible_cpu(cpu) { | |
156 | count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count; | |
157 | } | |
158 | ||
159 | return count; | |
160 | #else | |
161 | return mnt->mnt_count; | |
162 | #endif | |
163 | } | |
164 | ||
165 | static struct mount *alloc_vfsmnt(const char *name) | |
166 | { | |
167 | struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); | |
168 | if (mnt) { | |
169 | int err; | |
170 | ||
171 | err = mnt_alloc_id(mnt); | |
172 | if (err) | |
173 | goto out_free_cache; | |
174 | ||
175 | if (name) { | |
176 | mnt->mnt_devname = kstrdup(name, GFP_KERNEL); | |
177 | if (!mnt->mnt_devname) | |
178 | goto out_free_id; | |
179 | } | |
180 | ||
181 | #ifdef CONFIG_SMP | |
182 | mnt->mnt_pcp = alloc_percpu(struct mnt_pcp); | |
183 | if (!mnt->mnt_pcp) | |
184 | goto out_free_devname; | |
185 | ||
186 | this_cpu_add(mnt->mnt_pcp->mnt_count, 1); | |
187 | #else | |
188 | mnt->mnt_count = 1; | |
189 | mnt->mnt_writers = 0; | |
190 | #endif | |
191 | ||
192 | INIT_LIST_HEAD(&mnt->mnt_hash); | |
193 | INIT_LIST_HEAD(&mnt->mnt_child); | |
194 | INIT_LIST_HEAD(&mnt->mnt_mounts); | |
195 | INIT_LIST_HEAD(&mnt->mnt_list); | |
196 | INIT_LIST_HEAD(&mnt->mnt_expire); | |
197 | INIT_LIST_HEAD(&mnt->mnt_share); | |
198 | INIT_LIST_HEAD(&mnt->mnt_slave_list); | |
199 | INIT_LIST_HEAD(&mnt->mnt_slave); | |
200 | #ifdef CONFIG_FSNOTIFY | |
201 | INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks); | |
202 | #endif | |
203 | } | |
204 | return mnt; | |
205 | ||
206 | #ifdef CONFIG_SMP | |
207 | out_free_devname: | |
208 | kfree(mnt->mnt_devname); | |
209 | #endif | |
210 | out_free_id: | |
211 | mnt_free_id(mnt); | |
212 | out_free_cache: | |
213 | kmem_cache_free(mnt_cache, mnt); | |
214 | return NULL; | |
215 | } | |
216 | ||
217 | /* | |
218 | * Most r/o checks on a fs are for operations that take | |
219 | * discrete amounts of time, like a write() or unlink(). | |
220 | * We must keep track of when those operations start | |
221 | * (for permission checks) and when they end, so that | |
222 | * we can determine when writes are able to occur to | |
223 | * a filesystem. | |
224 | */ | |
225 | /* | |
226 | * __mnt_is_readonly: check whether a mount is read-only | |
227 | * @mnt: the mount to check for its write status | |
228 | * | |
229 | * This shouldn't be used directly ouside of the VFS. | |
230 | * It does not guarantee that the filesystem will stay | |
231 | * r/w, just that it is right *now*. This can not and | |
232 | * should not be used in place of IS_RDONLY(inode). | |
233 | * mnt_want/drop_write() will _keep_ the filesystem | |
234 | * r/w. | |
235 | */ | |
236 | int __mnt_is_readonly(struct vfsmount *mnt) | |
237 | { | |
238 | if (mnt->mnt_flags & MNT_READONLY) | |
239 | return 1; | |
240 | if (mnt->mnt_sb->s_flags & MS_RDONLY) | |
241 | return 1; | |
242 | return 0; | |
243 | } | |
244 | EXPORT_SYMBOL_GPL(__mnt_is_readonly); | |
245 | ||
246 | static inline void mnt_inc_writers(struct mount *mnt) | |
247 | { | |
248 | #ifdef CONFIG_SMP | |
249 | this_cpu_inc(mnt->mnt_pcp->mnt_writers); | |
250 | #else | |
251 | mnt->mnt_writers++; | |
252 | #endif | |
253 | } | |
254 | ||
255 | static inline void mnt_dec_writers(struct mount *mnt) | |
256 | { | |
257 | #ifdef CONFIG_SMP | |
258 | this_cpu_dec(mnt->mnt_pcp->mnt_writers); | |
259 | #else | |
260 | mnt->mnt_writers--; | |
261 | #endif | |
262 | } | |
263 | ||
264 | static unsigned int mnt_get_writers(struct mount *mnt) | |
265 | { | |
266 | #ifdef CONFIG_SMP | |
267 | unsigned int count = 0; | |
268 | int cpu; | |
269 | ||
270 | for_each_possible_cpu(cpu) { | |
271 | count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers; | |
272 | } | |
273 | ||
274 | return count; | |
275 | #else | |
276 | return mnt->mnt_writers; | |
277 | #endif | |
278 | } | |
279 | ||
280 | static int mnt_is_readonly(struct vfsmount *mnt) | |
281 | { | |
282 | if (mnt->mnt_sb->s_readonly_remount) | |
283 | return 1; | |
284 | /* Order wrt setting s_flags/s_readonly_remount in do_remount() */ | |
285 | smp_rmb(); | |
286 | return __mnt_is_readonly(mnt); | |
287 | } | |
288 | ||
289 | /* | |
290 | * Most r/o & frozen checks on a fs are for operations that take discrete | |
291 | * amounts of time, like a write() or unlink(). We must keep track of when | |
292 | * those operations start (for permission checks) and when they end, so that we | |
293 | * can determine when writes are able to occur to a filesystem. | |
294 | */ | |
295 | /** | |
296 | * __mnt_want_write - get write access to a mount without freeze protection | |
297 | * @m: the mount on which to take a write | |
298 | * | |
299 | * This tells the low-level filesystem that a write is about to be performed to | |
300 | * it, and makes sure that writes are allowed (mnt it read-write) before | |
301 | * returning success. This operation does not protect against filesystem being | |
302 | * frozen. When the write operation is finished, __mnt_drop_write() must be | |
303 | * called. This is effectively a refcount. | |
304 | */ | |
305 | int __mnt_want_write(struct vfsmount *m) | |
306 | { | |
307 | struct mount *mnt = real_mount(m); | |
308 | int ret = 0; | |
309 | ||
310 | preempt_disable(); | |
311 | mnt_inc_writers(mnt); | |
312 | /* | |
313 | * The store to mnt_inc_writers must be visible before we pass | |
314 | * MNT_WRITE_HOLD loop below, so that the slowpath can see our | |
315 | * incremented count after it has set MNT_WRITE_HOLD. | |
316 | */ | |
317 | smp_mb(); | |
318 | while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) | |
319 | cpu_relax(); | |
320 | /* | |
321 | * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will | |
322 | * be set to match its requirements. So we must not load that until | |
323 | * MNT_WRITE_HOLD is cleared. | |
324 | */ | |
325 | smp_rmb(); | |
326 | if (mnt_is_readonly(m)) { | |
327 | mnt_dec_writers(mnt); | |
328 | ret = -EROFS; | |
329 | } | |
330 | preempt_enable(); | |
331 | ||
332 | return ret; | |
333 | } | |
334 | ||
335 | /** | |
336 | * mnt_want_write - get write access to a mount | |
337 | * @m: the mount on which to take a write | |
338 | * | |
339 | * This tells the low-level filesystem that a write is about to be performed to | |
340 | * it, and makes sure that writes are allowed (mount is read-write, filesystem | |
341 | * is not frozen) before returning success. When the write operation is | |
342 | * finished, mnt_drop_write() must be called. This is effectively a refcount. | |
343 | */ | |
344 | int mnt_want_write(struct vfsmount *m) | |
345 | { | |
346 | int ret; | |
347 | ||
348 | sb_start_write(m->mnt_sb); | |
349 | ret = __mnt_want_write(m); | |
350 | if (ret) | |
351 | sb_end_write(m->mnt_sb); | |
352 | return ret; | |
353 | } | |
354 | EXPORT_SYMBOL_GPL(mnt_want_write); | |
355 | ||
356 | /** | |
357 | * mnt_clone_write - get write access to a mount | |
358 | * @mnt: the mount on which to take a write | |
359 | * | |
360 | * This is effectively like mnt_want_write, except | |
361 | * it must only be used to take an extra write reference | |
362 | * on a mountpoint that we already know has a write reference | |
363 | * on it. This allows some optimisation. | |
364 | * | |
365 | * After finished, mnt_drop_write must be called as usual to | |
366 | * drop the reference. | |
367 | */ | |
368 | int mnt_clone_write(struct vfsmount *mnt) | |
369 | { | |
370 | /* superblock may be r/o */ | |
371 | if (__mnt_is_readonly(mnt)) | |
372 | return -EROFS; | |
373 | preempt_disable(); | |
374 | mnt_inc_writers(real_mount(mnt)); | |
375 | preempt_enable(); | |
376 | return 0; | |
377 | } | |
378 | EXPORT_SYMBOL_GPL(mnt_clone_write); | |
379 | ||
380 | /** | |
381 | * __mnt_want_write_file - get write access to a file's mount | |
382 | * @file: the file who's mount on which to take a write | |
383 | * | |
384 | * This is like __mnt_want_write, but it takes a file and can | |
385 | * do some optimisations if the file is open for write already | |
386 | */ | |
387 | int __mnt_want_write_file(struct file *file) | |
388 | { | |
389 | struct inode *inode = file_inode(file); | |
390 | ||
391 | if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode)) | |
392 | return __mnt_want_write(file->f_path.mnt); | |
393 | else | |
394 | return mnt_clone_write(file->f_path.mnt); | |
395 | } | |
396 | ||
397 | /** | |
398 | * mnt_want_write_file - get write access to a file's mount | |
399 | * @file: the file who's mount on which to take a write | |
400 | * | |
401 | * This is like mnt_want_write, but it takes a file and can | |
402 | * do some optimisations if the file is open for write already | |
403 | */ | |
404 | int mnt_want_write_file(struct file *file) | |
405 | { | |
406 | int ret; | |
407 | ||
408 | sb_start_write(file->f_path.mnt->mnt_sb); | |
409 | ret = __mnt_want_write_file(file); | |
410 | if (ret) | |
411 | sb_end_write(file->f_path.mnt->mnt_sb); | |
412 | return ret; | |
413 | } | |
414 | EXPORT_SYMBOL_GPL(mnt_want_write_file); | |
415 | ||
416 | /** | |
417 | * __mnt_drop_write - give up write access to a mount | |
418 | * @mnt: the mount on which to give up write access | |
419 | * | |
420 | * Tells the low-level filesystem that we are done | |
421 | * performing writes to it. Must be matched with | |
422 | * __mnt_want_write() call above. | |
423 | */ | |
424 | void __mnt_drop_write(struct vfsmount *mnt) | |
425 | { | |
426 | preempt_disable(); | |
427 | mnt_dec_writers(real_mount(mnt)); | |
428 | preempt_enable(); | |
429 | } | |
430 | ||
431 | /** | |
432 | * mnt_drop_write - give up write access to a mount | |
433 | * @mnt: the mount on which to give up write access | |
434 | * | |
435 | * Tells the low-level filesystem that we are done performing writes to it and | |
436 | * also allows filesystem to be frozen again. Must be matched with | |
437 | * mnt_want_write() call above. | |
438 | */ | |
439 | void mnt_drop_write(struct vfsmount *mnt) | |
440 | { | |
441 | __mnt_drop_write(mnt); | |
442 | sb_end_write(mnt->mnt_sb); | |
443 | } | |
444 | EXPORT_SYMBOL_GPL(mnt_drop_write); | |
445 | ||
446 | void __mnt_drop_write_file(struct file *file) | |
447 | { | |
448 | __mnt_drop_write(file->f_path.mnt); | |
449 | } | |
450 | ||
451 | void mnt_drop_write_file(struct file *file) | |
452 | { | |
453 | mnt_drop_write(file->f_path.mnt); | |
454 | } | |
455 | EXPORT_SYMBOL(mnt_drop_write_file); | |
456 | ||
457 | static int mnt_make_readonly(struct mount *mnt) | |
458 | { | |
459 | int ret = 0; | |
460 | ||
461 | br_write_lock(&vfsmount_lock); | |
462 | mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; | |
463 | /* | |
464 | * After storing MNT_WRITE_HOLD, we'll read the counters. This store | |
465 | * should be visible before we do. | |
466 | */ | |
467 | smp_mb(); | |
468 | ||
469 | /* | |
470 | * With writers on hold, if this value is zero, then there are | |
471 | * definitely no active writers (although held writers may subsequently | |
472 | * increment the count, they'll have to wait, and decrement it after | |
473 | * seeing MNT_READONLY). | |
474 | * | |
475 | * It is OK to have counter incremented on one CPU and decremented on | |
476 | * another: the sum will add up correctly. The danger would be when we | |
477 | * sum up each counter, if we read a counter before it is incremented, | |
478 | * but then read another CPU's count which it has been subsequently | |
479 | * decremented from -- we would see more decrements than we should. | |
480 | * MNT_WRITE_HOLD protects against this scenario, because | |
481 | * mnt_want_write first increments count, then smp_mb, then spins on | |
482 | * MNT_WRITE_HOLD, so it can't be decremented by another CPU while | |
483 | * we're counting up here. | |
484 | */ | |
485 | if (mnt_get_writers(mnt) > 0) | |
486 | ret = -EBUSY; | |
487 | else | |
488 | mnt->mnt.mnt_flags |= MNT_READONLY; | |
489 | /* | |
490 | * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers | |
491 | * that become unheld will see MNT_READONLY. | |
492 | */ | |
493 | smp_wmb(); | |
494 | mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; | |
495 | br_write_unlock(&vfsmount_lock); | |
496 | return ret; | |
497 | } | |
498 | ||
499 | static void __mnt_unmake_readonly(struct mount *mnt) | |
500 | { | |
501 | br_write_lock(&vfsmount_lock); | |
502 | mnt->mnt.mnt_flags &= ~MNT_READONLY; | |
503 | br_write_unlock(&vfsmount_lock); | |
504 | } | |
505 | ||
506 | int sb_prepare_remount_readonly(struct super_block *sb) | |
507 | { | |
508 | struct mount *mnt; | |
509 | int err = 0; | |
510 | ||
511 | /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */ | |
512 | if (atomic_long_read(&sb->s_remove_count)) | |
513 | return -EBUSY; | |
514 | ||
515 | br_write_lock(&vfsmount_lock); | |
516 | list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { | |
517 | if (!(mnt->mnt.mnt_flags & MNT_READONLY)) { | |
518 | mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; | |
519 | smp_mb(); | |
520 | if (mnt_get_writers(mnt) > 0) { | |
521 | err = -EBUSY; | |
522 | break; | |
523 | } | |
524 | } | |
525 | } | |
526 | if (!err && atomic_long_read(&sb->s_remove_count)) | |
527 | err = -EBUSY; | |
528 | ||
529 | if (!err) { | |
530 | sb->s_readonly_remount = 1; | |
531 | smp_wmb(); | |
532 | } | |
533 | list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { | |
534 | if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD) | |
535 | mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; | |
536 | } | |
537 | br_write_unlock(&vfsmount_lock); | |
538 | ||
539 | return err; | |
540 | } | |
541 | ||
542 | static void free_vfsmnt(struct mount *mnt) | |
543 | { | |
544 | kfree(mnt->mnt_devname); | |
545 | mnt_free_id(mnt); | |
546 | #ifdef CONFIG_SMP | |
547 | free_percpu(mnt->mnt_pcp); | |
548 | #endif | |
549 | kmem_cache_free(mnt_cache, mnt); | |
550 | } | |
551 | ||
552 | /* | |
553 | * find the first or last mount at @dentry on vfsmount @mnt depending on | |
554 | * @dir. If @dir is set return the first mount else return the last mount. | |
555 | * vfsmount_lock must be held for read or write. | |
556 | */ | |
557 | struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry, | |
558 | int dir) | |
559 | { | |
560 | struct list_head *head = mount_hashtable + hash(mnt, dentry); | |
561 | struct list_head *tmp = head; | |
562 | struct mount *p, *found = NULL; | |
563 | ||
564 | for (;;) { | |
565 | tmp = dir ? tmp->next : tmp->prev; | |
566 | p = NULL; | |
567 | if (tmp == head) | |
568 | break; | |
569 | p = list_entry(tmp, struct mount, mnt_hash); | |
570 | if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) { | |
571 | found = p; | |
572 | break; | |
573 | } | |
574 | } | |
575 | return found; | |
576 | } | |
577 | ||
578 | /* | |
579 | * lookup_mnt - Return the first child mount mounted at path | |
580 | * | |
581 | * "First" means first mounted chronologically. If you create the | |
582 | * following mounts: | |
583 | * | |
584 | * mount /dev/sda1 /mnt | |
585 | * mount /dev/sda2 /mnt | |
586 | * mount /dev/sda3 /mnt | |
587 | * | |
588 | * Then lookup_mnt() on the base /mnt dentry in the root mount will | |
589 | * return successively the root dentry and vfsmount of /dev/sda1, then | |
590 | * /dev/sda2, then /dev/sda3, then NULL. | |
591 | * | |
592 | * lookup_mnt takes a reference to the found vfsmount. | |
593 | */ | |
594 | struct vfsmount *lookup_mnt(struct path *path) | |
595 | { | |
596 | struct mount *child_mnt; | |
597 | ||
598 | br_read_lock(&vfsmount_lock); | |
599 | child_mnt = __lookup_mnt(path->mnt, path->dentry, 1); | |
600 | if (child_mnt) { | |
601 | mnt_add_count(child_mnt, 1); | |
602 | br_read_unlock(&vfsmount_lock); | |
603 | return &child_mnt->mnt; | |
604 | } else { | |
605 | br_read_unlock(&vfsmount_lock); | |
606 | return NULL; | |
607 | } | |
608 | } | |
609 | ||
610 | static struct mountpoint *new_mountpoint(struct dentry *dentry) | |
611 | { | |
612 | struct list_head *chain = mountpoint_hashtable + hash(NULL, dentry); | |
613 | struct mountpoint *mp; | |
614 | int ret; | |
615 | ||
616 | list_for_each_entry(mp, chain, m_hash) { | |
617 | if (mp->m_dentry == dentry) { | |
618 | /* might be worth a WARN_ON() */ | |
619 | if (d_unlinked(dentry)) | |
620 | return ERR_PTR(-ENOENT); | |
621 | mp->m_count++; | |
622 | return mp; | |
623 | } | |
624 | } | |
625 | ||
626 | mp = kmalloc(sizeof(struct mountpoint), GFP_KERNEL); | |
627 | if (!mp) | |
628 | return ERR_PTR(-ENOMEM); | |
629 | ||
630 | ret = d_set_mounted(dentry); | |
631 | if (ret) { | |
632 | kfree(mp); | |
633 | return ERR_PTR(ret); | |
634 | } | |
635 | ||
636 | mp->m_dentry = dentry; | |
637 | mp->m_count = 1; | |
638 | list_add(&mp->m_hash, chain); | |
639 | return mp; | |
640 | } | |
641 | ||
642 | static void put_mountpoint(struct mountpoint *mp) | |
643 | { | |
644 | if (!--mp->m_count) { | |
645 | struct dentry *dentry = mp->m_dentry; | |
646 | spin_lock(&dentry->d_lock); | |
647 | dentry->d_flags &= ~DCACHE_MOUNTED; | |
648 | spin_unlock(&dentry->d_lock); | |
649 | list_del(&mp->m_hash); | |
650 | kfree(mp); | |
651 | } | |
652 | } | |
653 | ||
654 | static inline int check_mnt(struct mount *mnt) | |
655 | { | |
656 | return mnt->mnt_ns == current->nsproxy->mnt_ns; | |
657 | } | |
658 | ||
659 | /* | |
660 | * vfsmount lock must be held for write | |
661 | */ | |
662 | static void touch_mnt_namespace(struct mnt_namespace *ns) | |
663 | { | |
664 | if (ns) { | |
665 | ns->event = ++event; | |
666 | wake_up_interruptible(&ns->poll); | |
667 | } | |
668 | } | |
669 | ||
670 | /* | |
671 | * vfsmount lock must be held for write | |
672 | */ | |
673 | static void __touch_mnt_namespace(struct mnt_namespace *ns) | |
674 | { | |
675 | if (ns && ns->event != event) { | |
676 | ns->event = event; | |
677 | wake_up_interruptible(&ns->poll); | |
678 | } | |
679 | } | |
680 | ||
681 | /* | |
682 | * vfsmount lock must be held for write | |
683 | */ | |
684 | static void detach_mnt(struct mount *mnt, struct path *old_path) | |
685 | { | |
686 | old_path->dentry = mnt->mnt_mountpoint; | |
687 | old_path->mnt = &mnt->mnt_parent->mnt; | |
688 | mnt->mnt_parent = mnt; | |
689 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; | |
690 | list_del_init(&mnt->mnt_child); | |
691 | list_del_init(&mnt->mnt_hash); | |
692 | put_mountpoint(mnt->mnt_mp); | |
693 | mnt->mnt_mp = NULL; | |
694 | } | |
695 | ||
696 | /* | |
697 | * vfsmount lock must be held for write | |
698 | */ | |
699 | void mnt_set_mountpoint(struct mount *mnt, | |
700 | struct mountpoint *mp, | |
701 | struct mount *child_mnt) | |
702 | { | |
703 | mp->m_count++; | |
704 | mnt_add_count(mnt, 1); /* essentially, that's mntget */ | |
705 | child_mnt->mnt_mountpoint = dget(mp->m_dentry); | |
706 | child_mnt->mnt_parent = mnt; | |
707 | child_mnt->mnt_mp = mp; | |
708 | } | |
709 | ||
710 | /* | |
711 | * vfsmount lock must be held for write | |
712 | */ | |
713 | static void attach_mnt(struct mount *mnt, | |
714 | struct mount *parent, | |
715 | struct mountpoint *mp) | |
716 | { | |
717 | mnt_set_mountpoint(parent, mp, mnt); | |
718 | list_add_tail(&mnt->mnt_hash, mount_hashtable + | |
719 | hash(&parent->mnt, mp->m_dentry)); | |
720 | list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); | |
721 | } | |
722 | ||
723 | /* | |
724 | * vfsmount lock must be held for write | |
725 | */ | |
726 | static void commit_tree(struct mount *mnt) | |
727 | { | |
728 | struct mount *parent = mnt->mnt_parent; | |
729 | struct mount *m; | |
730 | LIST_HEAD(head); | |
731 | struct mnt_namespace *n = parent->mnt_ns; | |
732 | ||
733 | BUG_ON(parent == mnt); | |
734 | ||
735 | list_add_tail(&head, &mnt->mnt_list); | |
736 | list_for_each_entry(m, &head, mnt_list) | |
737 | m->mnt_ns = n; | |
738 | ||
739 | list_splice(&head, n->list.prev); | |
740 | ||
741 | list_add_tail(&mnt->mnt_hash, mount_hashtable + | |
742 | hash(&parent->mnt, mnt->mnt_mountpoint)); | |
743 | list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); | |
744 | touch_mnt_namespace(n); | |
745 | } | |
746 | ||
747 | static struct mount *next_mnt(struct mount *p, struct mount *root) | |
748 | { | |
749 | struct list_head *next = p->mnt_mounts.next; | |
750 | if (next == &p->mnt_mounts) { | |
751 | while (1) { | |
752 | if (p == root) | |
753 | return NULL; | |
754 | next = p->mnt_child.next; | |
755 | if (next != &p->mnt_parent->mnt_mounts) | |
756 | break; | |
757 | p = p->mnt_parent; | |
758 | } | |
759 | } | |
760 | return list_entry(next, struct mount, mnt_child); | |
761 | } | |
762 | ||
763 | static struct mount *skip_mnt_tree(struct mount *p) | |
764 | { | |
765 | struct list_head *prev = p->mnt_mounts.prev; | |
766 | while (prev != &p->mnt_mounts) { | |
767 | p = list_entry(prev, struct mount, mnt_child); | |
768 | prev = p->mnt_mounts.prev; | |
769 | } | |
770 | return p; | |
771 | } | |
772 | ||
773 | struct vfsmount * | |
774 | vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data) | |
775 | { | |
776 | struct mount *mnt; | |
777 | struct dentry *root; | |
778 | ||
779 | if (!type) | |
780 | return ERR_PTR(-ENODEV); | |
781 | ||
782 | mnt = alloc_vfsmnt(name); | |
783 | if (!mnt) | |
784 | return ERR_PTR(-ENOMEM); | |
785 | ||
786 | if (flags & MS_KERNMOUNT) | |
787 | mnt->mnt.mnt_flags = MNT_INTERNAL; | |
788 | ||
789 | root = mount_fs(type, flags, name, data); | |
790 | if (IS_ERR(root)) { | |
791 | free_vfsmnt(mnt); | |
792 | return ERR_CAST(root); | |
793 | } | |
794 | ||
795 | mnt->mnt.mnt_root = root; | |
796 | mnt->mnt.mnt_sb = root->d_sb; | |
797 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; | |
798 | mnt->mnt_parent = mnt; | |
799 | br_write_lock(&vfsmount_lock); | |
800 | list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts); | |
801 | br_write_unlock(&vfsmount_lock); | |
802 | return &mnt->mnt; | |
803 | } | |
804 | EXPORT_SYMBOL_GPL(vfs_kern_mount); | |
805 | ||
806 | static struct mount *clone_mnt(struct mount *old, struct dentry *root, | |
807 | int flag) | |
808 | { | |
809 | struct super_block *sb = old->mnt.mnt_sb; | |
810 | struct mount *mnt; | |
811 | int err; | |
812 | ||
813 | mnt = alloc_vfsmnt(old->mnt_devname); | |
814 | if (!mnt) | |
815 | return ERR_PTR(-ENOMEM); | |
816 | ||
817 | if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE)) | |
818 | mnt->mnt_group_id = 0; /* not a peer of original */ | |
819 | else | |
820 | mnt->mnt_group_id = old->mnt_group_id; | |
821 | ||
822 | if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { | |
823 | err = mnt_alloc_group_id(mnt); | |
824 | if (err) | |
825 | goto out_free; | |
826 | } | |
827 | ||
828 | mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD; | |
829 | /* Don't allow unprivileged users to change mount flags */ | |
830 | if ((flag & CL_UNPRIVILEGED) && (mnt->mnt.mnt_flags & MNT_READONLY)) | |
831 | mnt->mnt.mnt_flags |= MNT_LOCK_READONLY; | |
832 | ||
833 | /* Don't allow unprivileged users to reveal what is under a mount */ | |
834 | if ((flag & CL_UNPRIVILEGED) && list_empty(&old->mnt_expire)) | |
835 | mnt->mnt.mnt_flags |= MNT_LOCKED; | |
836 | ||
837 | atomic_inc(&sb->s_active); | |
838 | mnt->mnt.mnt_sb = sb; | |
839 | mnt->mnt.mnt_root = dget(root); | |
840 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; | |
841 | mnt->mnt_parent = mnt; | |
842 | br_write_lock(&vfsmount_lock); | |
843 | list_add_tail(&mnt->mnt_instance, &sb->s_mounts); | |
844 | br_write_unlock(&vfsmount_lock); | |
845 | ||
846 | if ((flag & CL_SLAVE) || | |
847 | ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) { | |
848 | list_add(&mnt->mnt_slave, &old->mnt_slave_list); | |
849 | mnt->mnt_master = old; | |
850 | CLEAR_MNT_SHARED(mnt); | |
851 | } else if (!(flag & CL_PRIVATE)) { | |
852 | if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old)) | |
853 | list_add(&mnt->mnt_share, &old->mnt_share); | |
854 | if (IS_MNT_SLAVE(old)) | |
855 | list_add(&mnt->mnt_slave, &old->mnt_slave); | |
856 | mnt->mnt_master = old->mnt_master; | |
857 | } | |
858 | if (flag & CL_MAKE_SHARED) | |
859 | set_mnt_shared(mnt); | |
860 | ||
861 | /* stick the duplicate mount on the same expiry list | |
862 | * as the original if that was on one */ | |
863 | if (flag & CL_EXPIRE) { | |
864 | if (!list_empty(&old->mnt_expire)) | |
865 | list_add(&mnt->mnt_expire, &old->mnt_expire); | |
866 | } | |
867 | ||
868 | return mnt; | |
869 | ||
870 | out_free: | |
871 | free_vfsmnt(mnt); | |
872 | return ERR_PTR(err); | |
873 | } | |
874 | ||
875 | static inline void mntfree(struct mount *mnt) | |
876 | { | |
877 | struct vfsmount *m = &mnt->mnt; | |
878 | struct super_block *sb = m->mnt_sb; | |
879 | ||
880 | /* | |
881 | * This probably indicates that somebody messed | |
882 | * up a mnt_want/drop_write() pair. If this | |
883 | * happens, the filesystem was probably unable | |
884 | * to make r/w->r/o transitions. | |
885 | */ | |
886 | /* | |
887 | * The locking used to deal with mnt_count decrement provides barriers, | |
888 | * so mnt_get_writers() below is safe. | |
889 | */ | |
890 | WARN_ON(mnt_get_writers(mnt)); | |
891 | fsnotify_vfsmount_delete(m); | |
892 | dput(m->mnt_root); | |
893 | free_vfsmnt(mnt); | |
894 | deactivate_super(sb); | |
895 | } | |
896 | ||
897 | static void mntput_no_expire(struct mount *mnt) | |
898 | { | |
899 | put_again: | |
900 | #ifdef CONFIG_SMP | |
901 | br_read_lock(&vfsmount_lock); | |
902 | if (likely(mnt->mnt_ns)) { | |
903 | /* shouldn't be the last one */ | |
904 | mnt_add_count(mnt, -1); | |
905 | br_read_unlock(&vfsmount_lock); | |
906 | return; | |
907 | } | |
908 | br_read_unlock(&vfsmount_lock); | |
909 | ||
910 | br_write_lock(&vfsmount_lock); | |
911 | mnt_add_count(mnt, -1); | |
912 | if (mnt_get_count(mnt)) { | |
913 | br_write_unlock(&vfsmount_lock); | |
914 | return; | |
915 | } | |
916 | #else | |
917 | mnt_add_count(mnt, -1); | |
918 | if (likely(mnt_get_count(mnt))) | |
919 | return; | |
920 | br_write_lock(&vfsmount_lock); | |
921 | #endif | |
922 | if (unlikely(mnt->mnt_pinned)) { | |
923 | mnt_add_count(mnt, mnt->mnt_pinned + 1); | |
924 | mnt->mnt_pinned = 0; | |
925 | br_write_unlock(&vfsmount_lock); | |
926 | acct_auto_close_mnt(&mnt->mnt); | |
927 | goto put_again; | |
928 | } | |
929 | ||
930 | list_del(&mnt->mnt_instance); | |
931 | br_write_unlock(&vfsmount_lock); | |
932 | mntfree(mnt); | |
933 | } | |
934 | ||
935 | void mntput(struct vfsmount *mnt) | |
936 | { | |
937 | if (mnt) { | |
938 | struct mount *m = real_mount(mnt); | |
939 | /* avoid cacheline pingpong, hope gcc doesn't get "smart" */ | |
940 | if (unlikely(m->mnt_expiry_mark)) | |
941 | m->mnt_expiry_mark = 0; | |
942 | mntput_no_expire(m); | |
943 | } | |
944 | } | |
945 | EXPORT_SYMBOL(mntput); | |
946 | ||
947 | struct vfsmount *mntget(struct vfsmount *mnt) | |
948 | { | |
949 | if (mnt) | |
950 | mnt_add_count(real_mount(mnt), 1); | |
951 | return mnt; | |
952 | } | |
953 | EXPORT_SYMBOL(mntget); | |
954 | ||
955 | void mnt_pin(struct vfsmount *mnt) | |
956 | { | |
957 | br_write_lock(&vfsmount_lock); | |
958 | real_mount(mnt)->mnt_pinned++; | |
959 | br_write_unlock(&vfsmount_lock); | |
960 | } | |
961 | EXPORT_SYMBOL(mnt_pin); | |
962 | ||
963 | void mnt_unpin(struct vfsmount *m) | |
964 | { | |
965 | struct mount *mnt = real_mount(m); | |
966 | br_write_lock(&vfsmount_lock); | |
967 | if (mnt->mnt_pinned) { | |
968 | mnt_add_count(mnt, 1); | |
969 | mnt->mnt_pinned--; | |
970 | } | |
971 | br_write_unlock(&vfsmount_lock); | |
972 | } | |
973 | EXPORT_SYMBOL(mnt_unpin); | |
974 | ||
975 | static inline void mangle(struct seq_file *m, const char *s) | |
976 | { | |
977 | seq_escape(m, s, " \t\n\\"); | |
978 | } | |
979 | ||
980 | /* | |
981 | * Simple .show_options callback for filesystems which don't want to | |
982 | * implement more complex mount option showing. | |
983 | * | |
984 | * See also save_mount_options(). | |
985 | */ | |
986 | int generic_show_options(struct seq_file *m, struct dentry *root) | |
987 | { | |
988 | const char *options; | |
989 | ||
990 | rcu_read_lock(); | |
991 | options = rcu_dereference(root->d_sb->s_options); | |
992 | ||
993 | if (options != NULL && options[0]) { | |
994 | seq_putc(m, ','); | |
995 | mangle(m, options); | |
996 | } | |
997 | rcu_read_unlock(); | |
998 | ||
999 | return 0; | |
1000 | } | |
1001 | EXPORT_SYMBOL(generic_show_options); | |
1002 | ||
1003 | /* | |
1004 | * If filesystem uses generic_show_options(), this function should be | |
1005 | * called from the fill_super() callback. | |
1006 | * | |
1007 | * The .remount_fs callback usually needs to be handled in a special | |
1008 | * way, to make sure, that previous options are not overwritten if the | |
1009 | * remount fails. | |
1010 | * | |
1011 | * Also note, that if the filesystem's .remount_fs function doesn't | |
1012 | * reset all options to their default value, but changes only newly | |
1013 | * given options, then the displayed options will not reflect reality | |
1014 | * any more. | |
1015 | */ | |
1016 | void save_mount_options(struct super_block *sb, char *options) | |
1017 | { | |
1018 | BUG_ON(sb->s_options); | |
1019 | rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL)); | |
1020 | } | |
1021 | EXPORT_SYMBOL(save_mount_options); | |
1022 | ||
1023 | void replace_mount_options(struct super_block *sb, char *options) | |
1024 | { | |
1025 | char *old = sb->s_options; | |
1026 | rcu_assign_pointer(sb->s_options, options); | |
1027 | if (old) { | |
1028 | synchronize_rcu(); | |
1029 | kfree(old); | |
1030 | } | |
1031 | } | |
1032 | EXPORT_SYMBOL(replace_mount_options); | |
1033 | ||
1034 | #ifdef CONFIG_PROC_FS | |
1035 | /* iterator; we want it to have access to namespace_sem, thus here... */ | |
1036 | static void *m_start(struct seq_file *m, loff_t *pos) | |
1037 | { | |
1038 | struct proc_mounts *p = proc_mounts(m); | |
1039 | ||
1040 | down_read(&namespace_sem); | |
1041 | return seq_list_start(&p->ns->list, *pos); | |
1042 | } | |
1043 | ||
1044 | static void *m_next(struct seq_file *m, void *v, loff_t *pos) | |
1045 | { | |
1046 | struct proc_mounts *p = proc_mounts(m); | |
1047 | ||
1048 | return seq_list_next(v, &p->ns->list, pos); | |
1049 | } | |
1050 | ||
1051 | static void m_stop(struct seq_file *m, void *v) | |
1052 | { | |
1053 | up_read(&namespace_sem); | |
1054 | } | |
1055 | ||
1056 | static int m_show(struct seq_file *m, void *v) | |
1057 | { | |
1058 | struct proc_mounts *p = proc_mounts(m); | |
1059 | struct mount *r = list_entry(v, struct mount, mnt_list); | |
1060 | return p->show(m, &r->mnt); | |
1061 | } | |
1062 | ||
1063 | const struct seq_operations mounts_op = { | |
1064 | .start = m_start, | |
1065 | .next = m_next, | |
1066 | .stop = m_stop, | |
1067 | .show = m_show, | |
1068 | }; | |
1069 | #endif /* CONFIG_PROC_FS */ | |
1070 | ||
1071 | /** | |
1072 | * may_umount_tree - check if a mount tree is busy | |
1073 | * @mnt: root of mount tree | |
1074 | * | |
1075 | * This is called to check if a tree of mounts has any | |
1076 | * open files, pwds, chroots or sub mounts that are | |
1077 | * busy. | |
1078 | */ | |
1079 | int may_umount_tree(struct vfsmount *m) | |
1080 | { | |
1081 | struct mount *mnt = real_mount(m); | |
1082 | int actual_refs = 0; | |
1083 | int minimum_refs = 0; | |
1084 | struct mount *p; | |
1085 | BUG_ON(!m); | |
1086 | ||
1087 | /* write lock needed for mnt_get_count */ | |
1088 | br_write_lock(&vfsmount_lock); | |
1089 | for (p = mnt; p; p = next_mnt(p, mnt)) { | |
1090 | actual_refs += mnt_get_count(p); | |
1091 | minimum_refs += 2; | |
1092 | } | |
1093 | br_write_unlock(&vfsmount_lock); | |
1094 | ||
1095 | if (actual_refs > minimum_refs) | |
1096 | return 0; | |
1097 | ||
1098 | return 1; | |
1099 | } | |
1100 | ||
1101 | EXPORT_SYMBOL(may_umount_tree); | |
1102 | ||
1103 | /** | |
1104 | * may_umount - check if a mount point is busy | |
1105 | * @mnt: root of mount | |
1106 | * | |
1107 | * This is called to check if a mount point has any | |
1108 | * open files, pwds, chroots or sub mounts. If the | |
1109 | * mount has sub mounts this will return busy | |
1110 | * regardless of whether the sub mounts are busy. | |
1111 | * | |
1112 | * Doesn't take quota and stuff into account. IOW, in some cases it will | |
1113 | * give false negatives. The main reason why it's here is that we need | |
1114 | * a non-destructive way to look for easily umountable filesystems. | |
1115 | */ | |
1116 | int may_umount(struct vfsmount *mnt) | |
1117 | { | |
1118 | int ret = 1; | |
1119 | down_read(&namespace_sem); | |
1120 | br_write_lock(&vfsmount_lock); | |
1121 | if (propagate_mount_busy(real_mount(mnt), 2)) | |
1122 | ret = 0; | |
1123 | br_write_unlock(&vfsmount_lock); | |
1124 | up_read(&namespace_sem); | |
1125 | return ret; | |
1126 | } | |
1127 | ||
1128 | EXPORT_SYMBOL(may_umount); | |
1129 | ||
1130 | static LIST_HEAD(unmounted); /* protected by namespace_sem */ | |
1131 | ||
1132 | static void namespace_unlock(void) | |
1133 | { | |
1134 | struct mount *mnt; | |
1135 | LIST_HEAD(head); | |
1136 | ||
1137 | if (likely(list_empty(&unmounted))) { | |
1138 | up_write(&namespace_sem); | |
1139 | return; | |
1140 | } | |
1141 | ||
1142 | list_splice_init(&unmounted, &head); | |
1143 | up_write(&namespace_sem); | |
1144 | ||
1145 | while (!list_empty(&head)) { | |
1146 | mnt = list_first_entry(&head, struct mount, mnt_hash); | |
1147 | list_del_init(&mnt->mnt_hash); | |
1148 | if (mnt_has_parent(mnt)) { | |
1149 | struct dentry *dentry; | |
1150 | struct mount *m; | |
1151 | ||
1152 | br_write_lock(&vfsmount_lock); | |
1153 | dentry = mnt->mnt_mountpoint; | |
1154 | m = mnt->mnt_parent; | |
1155 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; | |
1156 | mnt->mnt_parent = mnt; | |
1157 | m->mnt_ghosts--; | |
1158 | br_write_unlock(&vfsmount_lock); | |
1159 | dput(dentry); | |
1160 | mntput(&m->mnt); | |
1161 | } | |
1162 | mntput(&mnt->mnt); | |
1163 | } | |
1164 | } | |
1165 | ||
1166 | static inline void namespace_lock(void) | |
1167 | { | |
1168 | down_write(&namespace_sem); | |
1169 | } | |
1170 | ||
1171 | /* | |
1172 | * vfsmount lock must be held for write | |
1173 | * namespace_sem must be held for write | |
1174 | */ | |
1175 | void umount_tree(struct mount *mnt, int propagate) | |
1176 | { | |
1177 | LIST_HEAD(tmp_list); | |
1178 | struct mount *p; | |
1179 | ||
1180 | for (p = mnt; p; p = next_mnt(p, mnt)) | |
1181 | list_move(&p->mnt_hash, &tmp_list); | |
1182 | ||
1183 | if (propagate) | |
1184 | propagate_umount(&tmp_list); | |
1185 | ||
1186 | list_for_each_entry(p, &tmp_list, mnt_hash) { | |
1187 | list_del_init(&p->mnt_expire); | |
1188 | list_del_init(&p->mnt_list); | |
1189 | __touch_mnt_namespace(p->mnt_ns); | |
1190 | p->mnt_ns = NULL; | |
1191 | list_del_init(&p->mnt_child); | |
1192 | if (mnt_has_parent(p)) { | |
1193 | p->mnt_parent->mnt_ghosts++; | |
1194 | put_mountpoint(p->mnt_mp); | |
1195 | p->mnt_mp = NULL; | |
1196 | } | |
1197 | change_mnt_propagation(p, MS_PRIVATE); | |
1198 | } | |
1199 | list_splice(&tmp_list, &unmounted); | |
1200 | } | |
1201 | ||
1202 | static void shrink_submounts(struct mount *mnt); | |
1203 | ||
1204 | static int do_umount(struct mount *mnt, int flags) | |
1205 | { | |
1206 | struct super_block *sb = mnt->mnt.mnt_sb; | |
1207 | int retval; | |
1208 | ||
1209 | retval = security_sb_umount(&mnt->mnt, flags); | |
1210 | if (retval) | |
1211 | return retval; | |
1212 | ||
1213 | /* | |
1214 | * Allow userspace to request a mountpoint be expired rather than | |
1215 | * unmounting unconditionally. Unmount only happens if: | |
1216 | * (1) the mark is already set (the mark is cleared by mntput()) | |
1217 | * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] | |
1218 | */ | |
1219 | if (flags & MNT_EXPIRE) { | |
1220 | if (&mnt->mnt == current->fs->root.mnt || | |
1221 | flags & (MNT_FORCE | MNT_DETACH)) | |
1222 | return -EINVAL; | |
1223 | ||
1224 | /* | |
1225 | * probably don't strictly need the lock here if we examined | |
1226 | * all race cases, but it's a slowpath. | |
1227 | */ | |
1228 | br_write_lock(&vfsmount_lock); | |
1229 | if (mnt_get_count(mnt) != 2) { | |
1230 | br_write_unlock(&vfsmount_lock); | |
1231 | return -EBUSY; | |
1232 | } | |
1233 | br_write_unlock(&vfsmount_lock); | |
1234 | ||
1235 | if (!xchg(&mnt->mnt_expiry_mark, 1)) | |
1236 | return -EAGAIN; | |
1237 | } | |
1238 | ||
1239 | /* | |
1240 | * If we may have to abort operations to get out of this | |
1241 | * mount, and they will themselves hold resources we must | |
1242 | * allow the fs to do things. In the Unix tradition of | |
1243 | * 'Gee thats tricky lets do it in userspace' the umount_begin | |
1244 | * might fail to complete on the first run through as other tasks | |
1245 | * must return, and the like. Thats for the mount program to worry | |
1246 | * about for the moment. | |
1247 | */ | |
1248 | ||
1249 | if (flags & MNT_FORCE && sb->s_op->umount_begin) { | |
1250 | sb->s_op->umount_begin(sb); | |
1251 | } | |
1252 | ||
1253 | /* | |
1254 | * No sense to grab the lock for this test, but test itself looks | |
1255 | * somewhat bogus. Suggestions for better replacement? | |
1256 | * Ho-hum... In principle, we might treat that as umount + switch | |
1257 | * to rootfs. GC would eventually take care of the old vfsmount. | |
1258 | * Actually it makes sense, especially if rootfs would contain a | |
1259 | * /reboot - static binary that would close all descriptors and | |
1260 | * call reboot(9). Then init(8) could umount root and exec /reboot. | |
1261 | */ | |
1262 | if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { | |
1263 | /* | |
1264 | * Special case for "unmounting" root ... | |
1265 | * we just try to remount it readonly. | |
1266 | */ | |
1267 | down_write(&sb->s_umount); | |
1268 | if (!(sb->s_flags & MS_RDONLY)) | |
1269 | retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); | |
1270 | up_write(&sb->s_umount); | |
1271 | return retval; | |
1272 | } | |
1273 | ||
1274 | namespace_lock(); | |
1275 | br_write_lock(&vfsmount_lock); | |
1276 | event++; | |
1277 | ||
1278 | if (!(flags & MNT_DETACH)) | |
1279 | shrink_submounts(mnt); | |
1280 | ||
1281 | retval = -EBUSY; | |
1282 | if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) { | |
1283 | if (!list_empty(&mnt->mnt_list)) | |
1284 | umount_tree(mnt, 1); | |
1285 | retval = 0; | |
1286 | } | |
1287 | br_write_unlock(&vfsmount_lock); | |
1288 | namespace_unlock(); | |
1289 | return retval; | |
1290 | } | |
1291 | ||
1292 | /* | |
1293 | * Is the caller allowed to modify his namespace? | |
1294 | */ | |
1295 | static inline bool may_mount(void) | |
1296 | { | |
1297 | return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN); | |
1298 | } | |
1299 | ||
1300 | /* | |
1301 | * Now umount can handle mount points as well as block devices. | |
1302 | * This is important for filesystems which use unnamed block devices. | |
1303 | * | |
1304 | * We now support a flag for forced unmount like the other 'big iron' | |
1305 | * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD | |
1306 | */ | |
1307 | ||
1308 | SYSCALL_DEFINE2(umount, char __user *, name, int, flags) | |
1309 | { | |
1310 | struct path path; | |
1311 | struct mount *mnt; | |
1312 | int retval; | |
1313 | int lookup_flags = 0; | |
1314 | ||
1315 | if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) | |
1316 | return -EINVAL; | |
1317 | ||
1318 | if (!may_mount()) | |
1319 | return -EPERM; | |
1320 | ||
1321 | if (!(flags & UMOUNT_NOFOLLOW)) | |
1322 | lookup_flags |= LOOKUP_FOLLOW; | |
1323 | ||
1324 | retval = user_path_mountpoint_at(AT_FDCWD, name, lookup_flags, &path); | |
1325 | if (retval) | |
1326 | goto out; | |
1327 | mnt = real_mount(path.mnt); | |
1328 | retval = -EINVAL; | |
1329 | if (path.dentry != path.mnt->mnt_root) | |
1330 | goto dput_and_out; | |
1331 | if (!check_mnt(mnt)) | |
1332 | goto dput_and_out; | |
1333 | if (mnt->mnt.mnt_flags & MNT_LOCKED) | |
1334 | goto dput_and_out; | |
1335 | ||
1336 | retval = do_umount(mnt, flags); | |
1337 | dput_and_out: | |
1338 | /* we mustn't call path_put() as that would clear mnt_expiry_mark */ | |
1339 | dput(path.dentry); | |
1340 | mntput_no_expire(mnt); | |
1341 | out: | |
1342 | return retval; | |
1343 | } | |
1344 | ||
1345 | #ifdef __ARCH_WANT_SYS_OLDUMOUNT | |
1346 | ||
1347 | /* | |
1348 | * The 2.0 compatible umount. No flags. | |
1349 | */ | |
1350 | SYSCALL_DEFINE1(oldumount, char __user *, name) | |
1351 | { | |
1352 | return sys_umount(name, 0); | |
1353 | } | |
1354 | ||
1355 | #endif | |
1356 | ||
1357 | static bool is_mnt_ns_file(struct dentry *dentry) | |
1358 | { | |
1359 | /* Is this a proxy for a mount namespace? */ | |
1360 | struct inode *inode = dentry->d_inode; | |
1361 | struct proc_ns *ei; | |
1362 | ||
1363 | if (!proc_ns_inode(inode)) | |
1364 | return false; | |
1365 | ||
1366 | ei = get_proc_ns(inode); | |
1367 | if (ei->ns_ops != &mntns_operations) | |
1368 | return false; | |
1369 | ||
1370 | return true; | |
1371 | } | |
1372 | ||
1373 | static bool mnt_ns_loop(struct dentry *dentry) | |
1374 | { | |
1375 | /* Could bind mounting the mount namespace inode cause a | |
1376 | * mount namespace loop? | |
1377 | */ | |
1378 | struct mnt_namespace *mnt_ns; | |
1379 | if (!is_mnt_ns_file(dentry)) | |
1380 | return false; | |
1381 | ||
1382 | mnt_ns = get_proc_ns(dentry->d_inode)->ns; | |
1383 | return current->nsproxy->mnt_ns->seq >= mnt_ns->seq; | |
1384 | } | |
1385 | ||
1386 | struct mount *copy_tree(struct mount *mnt, struct dentry *dentry, | |
1387 | int flag) | |
1388 | { | |
1389 | struct mount *res, *p, *q, *r, *parent; | |
1390 | ||
1391 | if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt)) | |
1392 | return ERR_PTR(-EINVAL); | |
1393 | ||
1394 | if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry)) | |
1395 | return ERR_PTR(-EINVAL); | |
1396 | ||
1397 | res = q = clone_mnt(mnt, dentry, flag); | |
1398 | if (IS_ERR(q)) | |
1399 | return q; | |
1400 | ||
1401 | q->mnt.mnt_flags &= ~MNT_LOCKED; | |
1402 | q->mnt_mountpoint = mnt->mnt_mountpoint; | |
1403 | ||
1404 | p = mnt; | |
1405 | list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { | |
1406 | struct mount *s; | |
1407 | if (!is_subdir(r->mnt_mountpoint, dentry)) | |
1408 | continue; | |
1409 | ||
1410 | for (s = r; s; s = next_mnt(s, r)) { | |
1411 | if (!(flag & CL_COPY_UNBINDABLE) && | |
1412 | IS_MNT_UNBINDABLE(s)) { | |
1413 | s = skip_mnt_tree(s); | |
1414 | continue; | |
1415 | } | |
1416 | if (!(flag & CL_COPY_MNT_NS_FILE) && | |
1417 | is_mnt_ns_file(s->mnt.mnt_root)) { | |
1418 | s = skip_mnt_tree(s); | |
1419 | continue; | |
1420 | } | |
1421 | while (p != s->mnt_parent) { | |
1422 | p = p->mnt_parent; | |
1423 | q = q->mnt_parent; | |
1424 | } | |
1425 | p = s; | |
1426 | parent = q; | |
1427 | q = clone_mnt(p, p->mnt.mnt_root, flag); | |
1428 | if (IS_ERR(q)) | |
1429 | goto out; | |
1430 | br_write_lock(&vfsmount_lock); | |
1431 | list_add_tail(&q->mnt_list, &res->mnt_list); | |
1432 | attach_mnt(q, parent, p->mnt_mp); | |
1433 | br_write_unlock(&vfsmount_lock); | |
1434 | } | |
1435 | } | |
1436 | return res; | |
1437 | out: | |
1438 | if (res) { | |
1439 | br_write_lock(&vfsmount_lock); | |
1440 | umount_tree(res, 0); | |
1441 | br_write_unlock(&vfsmount_lock); | |
1442 | } | |
1443 | return q; | |
1444 | } | |
1445 | ||
1446 | /* Caller should check returned pointer for errors */ | |
1447 | ||
1448 | struct vfsmount *collect_mounts(struct path *path) | |
1449 | { | |
1450 | struct mount *tree; | |
1451 | namespace_lock(); | |
1452 | tree = copy_tree(real_mount(path->mnt), path->dentry, | |
1453 | CL_COPY_ALL | CL_PRIVATE); | |
1454 | namespace_unlock(); | |
1455 | if (IS_ERR(tree)) | |
1456 | return ERR_CAST(tree); | |
1457 | return &tree->mnt; | |
1458 | } | |
1459 | ||
1460 | void drop_collected_mounts(struct vfsmount *mnt) | |
1461 | { | |
1462 | namespace_lock(); | |
1463 | br_write_lock(&vfsmount_lock); | |
1464 | umount_tree(real_mount(mnt), 0); | |
1465 | br_write_unlock(&vfsmount_lock); | |
1466 | namespace_unlock(); | |
1467 | } | |
1468 | ||
1469 | int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, | |
1470 | struct vfsmount *root) | |
1471 | { | |
1472 | struct mount *mnt; | |
1473 | int res = f(root, arg); | |
1474 | if (res) | |
1475 | return res; | |
1476 | list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) { | |
1477 | res = f(&mnt->mnt, arg); | |
1478 | if (res) | |
1479 | return res; | |
1480 | } | |
1481 | return 0; | |
1482 | } | |
1483 | ||
1484 | static void cleanup_group_ids(struct mount *mnt, struct mount *end) | |
1485 | { | |
1486 | struct mount *p; | |
1487 | ||
1488 | for (p = mnt; p != end; p = next_mnt(p, mnt)) { | |
1489 | if (p->mnt_group_id && !IS_MNT_SHARED(p)) | |
1490 | mnt_release_group_id(p); | |
1491 | } | |
1492 | } | |
1493 | ||
1494 | static int invent_group_ids(struct mount *mnt, bool recurse) | |
1495 | { | |
1496 | struct mount *p; | |
1497 | ||
1498 | for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { | |
1499 | if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { | |
1500 | int err = mnt_alloc_group_id(p); | |
1501 | if (err) { | |
1502 | cleanup_group_ids(mnt, p); | |
1503 | return err; | |
1504 | } | |
1505 | } | |
1506 | } | |
1507 | ||
1508 | return 0; | |
1509 | } | |
1510 | ||
1511 | /* | |
1512 | * @source_mnt : mount tree to be attached | |
1513 | * @nd : place the mount tree @source_mnt is attached | |
1514 | * @parent_nd : if non-null, detach the source_mnt from its parent and | |
1515 | * store the parent mount and mountpoint dentry. | |
1516 | * (done when source_mnt is moved) | |
1517 | * | |
1518 | * NOTE: in the table below explains the semantics when a source mount | |
1519 | * of a given type is attached to a destination mount of a given type. | |
1520 | * --------------------------------------------------------------------------- | |
1521 | * | BIND MOUNT OPERATION | | |
1522 | * |************************************************************************** | |
1523 | * | source-->| shared | private | slave | unbindable | | |
1524 | * | dest | | | | | | |
1525 | * | | | | | | | | |
1526 | * | v | | | | | | |
1527 | * |************************************************************************** | |
1528 | * | shared | shared (++) | shared (+) | shared(+++)| invalid | | |
1529 | * | | | | | | | |
1530 | * |non-shared| shared (+) | private | slave (*) | invalid | | |
1531 | * *************************************************************************** | |
1532 | * A bind operation clones the source mount and mounts the clone on the | |
1533 | * destination mount. | |
1534 | * | |
1535 | * (++) the cloned mount is propagated to all the mounts in the propagation | |
1536 | * tree of the destination mount and the cloned mount is added to | |
1537 | * the peer group of the source mount. | |
1538 | * (+) the cloned mount is created under the destination mount and is marked | |
1539 | * as shared. The cloned mount is added to the peer group of the source | |
1540 | * mount. | |
1541 | * (+++) the mount is propagated to all the mounts in the propagation tree | |
1542 | * of the destination mount and the cloned mount is made slave | |
1543 | * of the same master as that of the source mount. The cloned mount | |
1544 | * is marked as 'shared and slave'. | |
1545 | * (*) the cloned mount is made a slave of the same master as that of the | |
1546 | * source mount. | |
1547 | * | |
1548 | * --------------------------------------------------------------------------- | |
1549 | * | MOVE MOUNT OPERATION | | |
1550 | * |************************************************************************** | |
1551 | * | source-->| shared | private | slave | unbindable | | |
1552 | * | dest | | | | | | |
1553 | * | | | | | | | | |
1554 | * | v | | | | | | |
1555 | * |************************************************************************** | |
1556 | * | shared | shared (+) | shared (+) | shared(+++) | invalid | | |
1557 | * | | | | | | | |
1558 | * |non-shared| shared (+*) | private | slave (*) | unbindable | | |
1559 | * *************************************************************************** | |
1560 | * | |
1561 | * (+) the mount is moved to the destination. And is then propagated to | |
1562 | * all the mounts in the propagation tree of the destination mount. | |
1563 | * (+*) the mount is moved to the destination. | |
1564 | * (+++) the mount is moved to the destination and is then propagated to | |
1565 | * all the mounts belonging to the destination mount's propagation tree. | |
1566 | * the mount is marked as 'shared and slave'. | |
1567 | * (*) the mount continues to be a slave at the new location. | |
1568 | * | |
1569 | * if the source mount is a tree, the operations explained above is | |
1570 | * applied to each mount in the tree. | |
1571 | * Must be called without spinlocks held, since this function can sleep | |
1572 | * in allocations. | |
1573 | */ | |
1574 | static int attach_recursive_mnt(struct mount *source_mnt, | |
1575 | struct mount *dest_mnt, | |
1576 | struct mountpoint *dest_mp, | |
1577 | struct path *parent_path) | |
1578 | { | |
1579 | LIST_HEAD(tree_list); | |
1580 | struct mount *child, *p; | |
1581 | int err; | |
1582 | ||
1583 | if (IS_MNT_SHARED(dest_mnt)) { | |
1584 | err = invent_group_ids(source_mnt, true); | |
1585 | if (err) | |
1586 | goto out; | |
1587 | } | |
1588 | err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list); | |
1589 | if (err) | |
1590 | goto out_cleanup_ids; | |
1591 | ||
1592 | br_write_lock(&vfsmount_lock); | |
1593 | ||
1594 | if (IS_MNT_SHARED(dest_mnt)) { | |
1595 | for (p = source_mnt; p; p = next_mnt(p, source_mnt)) | |
1596 | set_mnt_shared(p); | |
1597 | } | |
1598 | if (parent_path) { | |
1599 | detach_mnt(source_mnt, parent_path); | |
1600 | attach_mnt(source_mnt, dest_mnt, dest_mp); | |
1601 | touch_mnt_namespace(source_mnt->mnt_ns); | |
1602 | } else { | |
1603 | mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt); | |
1604 | commit_tree(source_mnt); | |
1605 | } | |
1606 | ||
1607 | list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { | |
1608 | list_del_init(&child->mnt_hash); | |
1609 | commit_tree(child); | |
1610 | } | |
1611 | br_write_unlock(&vfsmount_lock); | |
1612 | ||
1613 | return 0; | |
1614 | ||
1615 | out_cleanup_ids: | |
1616 | if (IS_MNT_SHARED(dest_mnt)) | |
1617 | cleanup_group_ids(source_mnt, NULL); | |
1618 | out: | |
1619 | return err; | |
1620 | } | |
1621 | ||
1622 | static struct mountpoint *lock_mount(struct path *path) | |
1623 | { | |
1624 | struct vfsmount *mnt; | |
1625 | struct dentry *dentry = path->dentry; | |
1626 | retry: | |
1627 | mutex_lock(&dentry->d_inode->i_mutex); | |
1628 | if (unlikely(cant_mount(dentry))) { | |
1629 | mutex_unlock(&dentry->d_inode->i_mutex); | |
1630 | return ERR_PTR(-ENOENT); | |
1631 | } | |
1632 | namespace_lock(); | |
1633 | mnt = lookup_mnt(path); | |
1634 | if (likely(!mnt)) { | |
1635 | struct mountpoint *mp = new_mountpoint(dentry); | |
1636 | if (IS_ERR(mp)) { | |
1637 | namespace_unlock(); | |
1638 | mutex_unlock(&dentry->d_inode->i_mutex); | |
1639 | return mp; | |
1640 | } | |
1641 | return mp; | |
1642 | } | |
1643 | namespace_unlock(); | |
1644 | mutex_unlock(&path->dentry->d_inode->i_mutex); | |
1645 | path_put(path); | |
1646 | path->mnt = mnt; | |
1647 | dentry = path->dentry = dget(mnt->mnt_root); | |
1648 | goto retry; | |
1649 | } | |
1650 | ||
1651 | static void unlock_mount(struct mountpoint *where) | |
1652 | { | |
1653 | struct dentry *dentry = where->m_dentry; | |
1654 | put_mountpoint(where); | |
1655 | namespace_unlock(); | |
1656 | mutex_unlock(&dentry->d_inode->i_mutex); | |
1657 | } | |
1658 | ||
1659 | static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp) | |
1660 | { | |
1661 | if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER) | |
1662 | return -EINVAL; | |
1663 | ||
1664 | if (S_ISDIR(mp->m_dentry->d_inode->i_mode) != | |
1665 | S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode)) | |
1666 | return -ENOTDIR; | |
1667 | ||
1668 | return attach_recursive_mnt(mnt, p, mp, NULL); | |
1669 | } | |
1670 | ||
1671 | /* | |
1672 | * Sanity check the flags to change_mnt_propagation. | |
1673 | */ | |
1674 | ||
1675 | static int flags_to_propagation_type(int flags) | |
1676 | { | |
1677 | int type = flags & ~(MS_REC | MS_SILENT); | |
1678 | ||
1679 | /* Fail if any non-propagation flags are set */ | |
1680 | if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) | |
1681 | return 0; | |
1682 | /* Only one propagation flag should be set */ | |
1683 | if (!is_power_of_2(type)) | |
1684 | return 0; | |
1685 | return type; | |
1686 | } | |
1687 | ||
1688 | /* | |
1689 | * recursively change the type of the mountpoint. | |
1690 | */ | |
1691 | static int do_change_type(struct path *path, int flag) | |
1692 | { | |
1693 | struct mount *m; | |
1694 | struct mount *mnt = real_mount(path->mnt); | |
1695 | int recurse = flag & MS_REC; | |
1696 | int type; | |
1697 | int err = 0; | |
1698 | ||
1699 | if (path->dentry != path->mnt->mnt_root) | |
1700 | return -EINVAL; | |
1701 | ||
1702 | type = flags_to_propagation_type(flag); | |
1703 | if (!type) | |
1704 | return -EINVAL; | |
1705 | ||
1706 | namespace_lock(); | |
1707 | if (type == MS_SHARED) { | |
1708 | err = invent_group_ids(mnt, recurse); | |
1709 | if (err) | |
1710 | goto out_unlock; | |
1711 | } | |
1712 | ||
1713 | br_write_lock(&vfsmount_lock); | |
1714 | for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) | |
1715 | change_mnt_propagation(m, type); | |
1716 | br_write_unlock(&vfsmount_lock); | |
1717 | ||
1718 | out_unlock: | |
1719 | namespace_unlock(); | |
1720 | return err; | |
1721 | } | |
1722 | ||
1723 | static bool has_locked_children(struct mount *mnt, struct dentry *dentry) | |
1724 | { | |
1725 | struct mount *child; | |
1726 | list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { | |
1727 | if (!is_subdir(child->mnt_mountpoint, dentry)) | |
1728 | continue; | |
1729 | ||
1730 | if (child->mnt.mnt_flags & MNT_LOCKED) | |
1731 | return true; | |
1732 | } | |
1733 | return false; | |
1734 | } | |
1735 | ||
1736 | /* | |
1737 | * do loopback mount. | |
1738 | */ | |
1739 | static int do_loopback(struct path *path, const char *old_name, | |
1740 | int recurse) | |
1741 | { | |
1742 | struct path old_path; | |
1743 | struct mount *mnt = NULL, *old, *parent; | |
1744 | struct mountpoint *mp; | |
1745 | int err; | |
1746 | if (!old_name || !*old_name) | |
1747 | return -EINVAL; | |
1748 | err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); | |
1749 | if (err) | |
1750 | return err; | |
1751 | ||
1752 | err = -EINVAL; | |
1753 | if (mnt_ns_loop(old_path.dentry)) | |
1754 | goto out; | |
1755 | ||
1756 | mp = lock_mount(path); | |
1757 | err = PTR_ERR(mp); | |
1758 | if (IS_ERR(mp)) | |
1759 | goto out; | |
1760 | ||
1761 | old = real_mount(old_path.mnt); | |
1762 | parent = real_mount(path->mnt); | |
1763 | ||
1764 | err = -EINVAL; | |
1765 | if (IS_MNT_UNBINDABLE(old)) | |
1766 | goto out2; | |
1767 | ||
1768 | if (!check_mnt(parent) || !check_mnt(old)) | |
1769 | goto out2; | |
1770 | ||
1771 | if (!recurse && has_locked_children(old, old_path.dentry)) | |
1772 | goto out2; | |
1773 | ||
1774 | if (recurse) | |
1775 | mnt = copy_tree(old, old_path.dentry, CL_COPY_MNT_NS_FILE); | |
1776 | else | |
1777 | mnt = clone_mnt(old, old_path.dentry, 0); | |
1778 | ||
1779 | if (IS_ERR(mnt)) { | |
1780 | err = PTR_ERR(mnt); | |
1781 | goto out2; | |
1782 | } | |
1783 | ||
1784 | mnt->mnt.mnt_flags &= ~MNT_LOCKED; | |
1785 | ||
1786 | err = graft_tree(mnt, parent, mp); | |
1787 | if (err) { | |
1788 | br_write_lock(&vfsmount_lock); | |
1789 | umount_tree(mnt, 0); | |
1790 | br_write_unlock(&vfsmount_lock); | |
1791 | } | |
1792 | out2: | |
1793 | unlock_mount(mp); | |
1794 | out: | |
1795 | path_put(&old_path); | |
1796 | return err; | |
1797 | } | |
1798 | ||
1799 | static int change_mount_flags(struct vfsmount *mnt, int ms_flags) | |
1800 | { | |
1801 | int error = 0; | |
1802 | int readonly_request = 0; | |
1803 | ||
1804 | if (ms_flags & MS_RDONLY) | |
1805 | readonly_request = 1; | |
1806 | if (readonly_request == __mnt_is_readonly(mnt)) | |
1807 | return 0; | |
1808 | ||
1809 | if (mnt->mnt_flags & MNT_LOCK_READONLY) | |
1810 | return -EPERM; | |
1811 | ||
1812 | if (readonly_request) | |
1813 | error = mnt_make_readonly(real_mount(mnt)); | |
1814 | else | |
1815 | __mnt_unmake_readonly(real_mount(mnt)); | |
1816 | return error; | |
1817 | } | |
1818 | ||
1819 | /* | |
1820 | * change filesystem flags. dir should be a physical root of filesystem. | |
1821 | * If you've mounted a non-root directory somewhere and want to do remount | |
1822 | * on it - tough luck. | |
1823 | */ | |
1824 | static int do_remount(struct path *path, int flags, int mnt_flags, | |
1825 | void *data) | |
1826 | { | |
1827 | int err; | |
1828 | struct super_block *sb = path->mnt->mnt_sb; | |
1829 | struct mount *mnt = real_mount(path->mnt); | |
1830 | ||
1831 | if (!check_mnt(mnt)) | |
1832 | return -EINVAL; | |
1833 | ||
1834 | if (path->dentry != path->mnt->mnt_root) | |
1835 | return -EINVAL; | |
1836 | ||
1837 | err = security_sb_remount(sb, data); | |
1838 | if (err) | |
1839 | return err; | |
1840 | ||
1841 | down_write(&sb->s_umount); | |
1842 | if (flags & MS_BIND) | |
1843 | err = change_mount_flags(path->mnt, flags); | |
1844 | else if (!capable(CAP_SYS_ADMIN)) | |
1845 | err = -EPERM; | |
1846 | else | |
1847 | err = do_remount_sb(sb, flags, data, 0); | |
1848 | if (!err) { | |
1849 | br_write_lock(&vfsmount_lock); | |
1850 | mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK; | |
1851 | mnt->mnt.mnt_flags = mnt_flags; | |
1852 | br_write_unlock(&vfsmount_lock); | |
1853 | } | |
1854 | up_write(&sb->s_umount); | |
1855 | if (!err) { | |
1856 | br_write_lock(&vfsmount_lock); | |
1857 | touch_mnt_namespace(mnt->mnt_ns); | |
1858 | br_write_unlock(&vfsmount_lock); | |
1859 | } | |
1860 | return err; | |
1861 | } | |
1862 | ||
1863 | static inline int tree_contains_unbindable(struct mount *mnt) | |
1864 | { | |
1865 | struct mount *p; | |
1866 | for (p = mnt; p; p = next_mnt(p, mnt)) { | |
1867 | if (IS_MNT_UNBINDABLE(p)) | |
1868 | return 1; | |
1869 | } | |
1870 | return 0; | |
1871 | } | |
1872 | ||
1873 | static int do_move_mount(struct path *path, const char *old_name) | |
1874 | { | |
1875 | struct path old_path, parent_path; | |
1876 | struct mount *p; | |
1877 | struct mount *old; | |
1878 | struct mountpoint *mp; | |
1879 | int err; | |
1880 | if (!old_name || !*old_name) | |
1881 | return -EINVAL; | |
1882 | err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); | |
1883 | if (err) | |
1884 | return err; | |
1885 | ||
1886 | mp = lock_mount(path); | |
1887 | err = PTR_ERR(mp); | |
1888 | if (IS_ERR(mp)) | |
1889 | goto out; | |
1890 | ||
1891 | old = real_mount(old_path.mnt); | |
1892 | p = real_mount(path->mnt); | |
1893 | ||
1894 | err = -EINVAL; | |
1895 | if (!check_mnt(p) || !check_mnt(old)) | |
1896 | goto out1; | |
1897 | ||
1898 | if (old->mnt.mnt_flags & MNT_LOCKED) | |
1899 | goto out1; | |
1900 | ||
1901 | err = -EINVAL; | |
1902 | if (old_path.dentry != old_path.mnt->mnt_root) | |
1903 | goto out1; | |
1904 | ||
1905 | if (!mnt_has_parent(old)) | |
1906 | goto out1; | |
1907 | ||
1908 | if (S_ISDIR(path->dentry->d_inode->i_mode) != | |
1909 | S_ISDIR(old_path.dentry->d_inode->i_mode)) | |
1910 | goto out1; | |
1911 | /* | |
1912 | * Don't move a mount residing in a shared parent. | |
1913 | */ | |
1914 | if (IS_MNT_SHARED(old->mnt_parent)) | |
1915 | goto out1; | |
1916 | /* | |
1917 | * Don't move a mount tree containing unbindable mounts to a destination | |
1918 | * mount which is shared. | |
1919 | */ | |
1920 | if (IS_MNT_SHARED(p) && tree_contains_unbindable(old)) | |
1921 | goto out1; | |
1922 | err = -ELOOP; | |
1923 | for (; mnt_has_parent(p); p = p->mnt_parent) | |
1924 | if (p == old) | |
1925 | goto out1; | |
1926 | ||
1927 | err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path); | |
1928 | if (err) | |
1929 | goto out1; | |
1930 | ||
1931 | /* if the mount is moved, it should no longer be expire | |
1932 | * automatically */ | |
1933 | list_del_init(&old->mnt_expire); | |
1934 | out1: | |
1935 | unlock_mount(mp); | |
1936 | out: | |
1937 | if (!err) | |
1938 | path_put(&parent_path); | |
1939 | path_put(&old_path); | |
1940 | return err; | |
1941 | } | |
1942 | ||
1943 | static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype) | |
1944 | { | |
1945 | int err; | |
1946 | const char *subtype = strchr(fstype, '.'); | |
1947 | if (subtype) { | |
1948 | subtype++; | |
1949 | err = -EINVAL; | |
1950 | if (!subtype[0]) | |
1951 | goto err; | |
1952 | } else | |
1953 | subtype = ""; | |
1954 | ||
1955 | mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL); | |
1956 | err = -ENOMEM; | |
1957 | if (!mnt->mnt_sb->s_subtype) | |
1958 | goto err; | |
1959 | return mnt; | |
1960 | ||
1961 | err: | |
1962 | mntput(mnt); | |
1963 | return ERR_PTR(err); | |
1964 | } | |
1965 | ||
1966 | /* | |
1967 | * add a mount into a namespace's mount tree | |
1968 | */ | |
1969 | static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags) | |
1970 | { | |
1971 | struct mountpoint *mp; | |
1972 | struct mount *parent; | |
1973 | int err; | |
1974 | ||
1975 | mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL); | |
1976 | ||
1977 | mp = lock_mount(path); | |
1978 | if (IS_ERR(mp)) | |
1979 | return PTR_ERR(mp); | |
1980 | ||
1981 | parent = real_mount(path->mnt); | |
1982 | err = -EINVAL; | |
1983 | if (unlikely(!check_mnt(parent))) { | |
1984 | /* that's acceptable only for automounts done in private ns */ | |
1985 | if (!(mnt_flags & MNT_SHRINKABLE)) | |
1986 | goto unlock; | |
1987 | /* ... and for those we'd better have mountpoint still alive */ | |
1988 | if (!parent->mnt_ns) | |
1989 | goto unlock; | |
1990 | } | |
1991 | ||
1992 | /* Refuse the same filesystem on the same mount point */ | |
1993 | err = -EBUSY; | |
1994 | if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && | |
1995 | path->mnt->mnt_root == path->dentry) | |
1996 | goto unlock; | |
1997 | ||
1998 | err = -EINVAL; | |
1999 | if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode)) | |
2000 | goto unlock; | |
2001 | ||
2002 | newmnt->mnt.mnt_flags = mnt_flags; | |
2003 | err = graft_tree(newmnt, parent, mp); | |
2004 | ||
2005 | unlock: | |
2006 | unlock_mount(mp); | |
2007 | return err; | |
2008 | } | |
2009 | ||
2010 | /* | |
2011 | * create a new mount for userspace and request it to be added into the | |
2012 | * namespace's tree | |
2013 | */ | |
2014 | static int do_new_mount(struct path *path, const char *fstype, int flags, | |
2015 | int mnt_flags, const char *name, void *data) | |
2016 | { | |
2017 | struct file_system_type *type; | |
2018 | struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; | |
2019 | struct vfsmount *mnt; | |
2020 | int err; | |
2021 | ||
2022 | if (!fstype) | |
2023 | return -EINVAL; | |
2024 | ||
2025 | type = get_fs_type(fstype); | |
2026 | if (!type) | |
2027 | return -ENODEV; | |
2028 | ||
2029 | if (user_ns != &init_user_ns) { | |
2030 | if (!(type->fs_flags & FS_USERNS_MOUNT)) { | |
2031 | put_filesystem(type); | |
2032 | return -EPERM; | |
2033 | } | |
2034 | /* Only in special cases allow devices from mounts | |
2035 | * created outside the initial user namespace. | |
2036 | */ | |
2037 | if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) { | |
2038 | flags |= MS_NODEV; | |
2039 | mnt_flags |= MNT_NODEV; | |
2040 | } | |
2041 | } | |
2042 | ||
2043 | mnt = vfs_kern_mount(type, flags, name, data); | |
2044 | if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && | |
2045 | !mnt->mnt_sb->s_subtype) | |
2046 | mnt = fs_set_subtype(mnt, fstype); | |
2047 | ||
2048 | put_filesystem(type); | |
2049 | if (IS_ERR(mnt)) | |
2050 | return PTR_ERR(mnt); | |
2051 | ||
2052 | err = do_add_mount(real_mount(mnt), path, mnt_flags); | |
2053 | if (err) | |
2054 | mntput(mnt); | |
2055 | return err; | |
2056 | } | |
2057 | ||
2058 | int finish_automount(struct vfsmount *m, struct path *path) | |
2059 | { | |
2060 | struct mount *mnt = real_mount(m); | |
2061 | int err; | |
2062 | /* The new mount record should have at least 2 refs to prevent it being | |
2063 | * expired before we get a chance to add it | |
2064 | */ | |
2065 | BUG_ON(mnt_get_count(mnt) < 2); | |
2066 | ||
2067 | if (m->mnt_sb == path->mnt->mnt_sb && | |
2068 | m->mnt_root == path->dentry) { | |
2069 | err = -ELOOP; | |
2070 | goto fail; | |
2071 | } | |
2072 | ||
2073 | err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE); | |
2074 | if (!err) | |
2075 | return 0; | |
2076 | fail: | |
2077 | /* remove m from any expiration list it may be on */ | |
2078 | if (!list_empty(&mnt->mnt_expire)) { | |
2079 | namespace_lock(); | |
2080 | br_write_lock(&vfsmount_lock); | |
2081 | list_del_init(&mnt->mnt_expire); | |
2082 | br_write_unlock(&vfsmount_lock); | |
2083 | namespace_unlock(); | |
2084 | } | |
2085 | mntput(m); | |
2086 | mntput(m); | |
2087 | return err; | |
2088 | } | |
2089 | ||
2090 | /** | |
2091 | * mnt_set_expiry - Put a mount on an expiration list | |
2092 | * @mnt: The mount to list. | |
2093 | * @expiry_list: The list to add the mount to. | |
2094 | */ | |
2095 | void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list) | |
2096 | { | |
2097 | namespace_lock(); | |
2098 | br_write_lock(&vfsmount_lock); | |
2099 | ||
2100 | list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list); | |
2101 | ||
2102 | br_write_unlock(&vfsmount_lock); | |
2103 | namespace_unlock(); | |
2104 | } | |
2105 | EXPORT_SYMBOL(mnt_set_expiry); | |
2106 | ||
2107 | /* | |
2108 | * process a list of expirable mountpoints with the intent of discarding any | |
2109 | * mountpoints that aren't in use and haven't been touched since last we came | |
2110 | * here | |
2111 | */ | |
2112 | void mark_mounts_for_expiry(struct list_head *mounts) | |
2113 | { | |
2114 | struct mount *mnt, *next; | |
2115 | LIST_HEAD(graveyard); | |
2116 | ||
2117 | if (list_empty(mounts)) | |
2118 | return; | |
2119 | ||
2120 | namespace_lock(); | |
2121 | br_write_lock(&vfsmount_lock); | |
2122 | ||
2123 | /* extract from the expiration list every vfsmount that matches the | |
2124 | * following criteria: | |
2125 | * - only referenced by its parent vfsmount | |
2126 | * - still marked for expiry (marked on the last call here; marks are | |
2127 | * cleared by mntput()) | |
2128 | */ | |
2129 | list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { | |
2130 | if (!xchg(&mnt->mnt_expiry_mark, 1) || | |
2131 | propagate_mount_busy(mnt, 1)) | |
2132 | continue; | |
2133 | list_move(&mnt->mnt_expire, &graveyard); | |
2134 | } | |
2135 | while (!list_empty(&graveyard)) { | |
2136 | mnt = list_first_entry(&graveyard, struct mount, mnt_expire); | |
2137 | touch_mnt_namespace(mnt->mnt_ns); | |
2138 | umount_tree(mnt, 1); | |
2139 | } | |
2140 | br_write_unlock(&vfsmount_lock); | |
2141 | namespace_unlock(); | |
2142 | } | |
2143 | ||
2144 | EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); | |
2145 | ||
2146 | /* | |
2147 | * Ripoff of 'select_parent()' | |
2148 | * | |
2149 | * search the list of submounts for a given mountpoint, and move any | |
2150 | * shrinkable submounts to the 'graveyard' list. | |
2151 | */ | |
2152 | static int select_submounts(struct mount *parent, struct list_head *graveyard) | |
2153 | { | |
2154 | struct mount *this_parent = parent; | |
2155 | struct list_head *next; | |
2156 | int found = 0; | |
2157 | ||
2158 | repeat: | |
2159 | next = this_parent->mnt_mounts.next; | |
2160 | resume: | |
2161 | while (next != &this_parent->mnt_mounts) { | |
2162 | struct list_head *tmp = next; | |
2163 | struct mount *mnt = list_entry(tmp, struct mount, mnt_child); | |
2164 | ||
2165 | next = tmp->next; | |
2166 | if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE)) | |
2167 | continue; | |
2168 | /* | |
2169 | * Descend a level if the d_mounts list is non-empty. | |
2170 | */ | |
2171 | if (!list_empty(&mnt->mnt_mounts)) { | |
2172 | this_parent = mnt; | |
2173 | goto repeat; | |
2174 | } | |
2175 | ||
2176 | if (!propagate_mount_busy(mnt, 1)) { | |
2177 | list_move_tail(&mnt->mnt_expire, graveyard); | |
2178 | found++; | |
2179 | } | |
2180 | } | |
2181 | /* | |
2182 | * All done at this level ... ascend and resume the search | |
2183 | */ | |
2184 | if (this_parent != parent) { | |
2185 | next = this_parent->mnt_child.next; | |
2186 | this_parent = this_parent->mnt_parent; | |
2187 | goto resume; | |
2188 | } | |
2189 | return found; | |
2190 | } | |
2191 | ||
2192 | /* | |
2193 | * process a list of expirable mountpoints with the intent of discarding any | |
2194 | * submounts of a specific parent mountpoint | |
2195 | * | |
2196 | * vfsmount_lock must be held for write | |
2197 | */ | |
2198 | static void shrink_submounts(struct mount *mnt) | |
2199 | { | |
2200 | LIST_HEAD(graveyard); | |
2201 | struct mount *m; | |
2202 | ||
2203 | /* extract submounts of 'mountpoint' from the expiration list */ | |
2204 | while (select_submounts(mnt, &graveyard)) { | |
2205 | while (!list_empty(&graveyard)) { | |
2206 | m = list_first_entry(&graveyard, struct mount, | |
2207 | mnt_expire); | |
2208 | touch_mnt_namespace(m->mnt_ns); | |
2209 | umount_tree(m, 1); | |
2210 | } | |
2211 | } | |
2212 | } | |
2213 | ||
2214 | /* | |
2215 | * Some copy_from_user() implementations do not return the exact number of | |
2216 | * bytes remaining to copy on a fault. But copy_mount_options() requires that. | |
2217 | * Note that this function differs from copy_from_user() in that it will oops | |
2218 | * on bad values of `to', rather than returning a short copy. | |
2219 | */ | |
2220 | static long exact_copy_from_user(void *to, const void __user * from, | |
2221 | unsigned long n) | |
2222 | { | |
2223 | char *t = to; | |
2224 | const char __user *f = from; | |
2225 | char c; | |
2226 | ||
2227 | if (!access_ok(VERIFY_READ, from, n)) | |
2228 | return n; | |
2229 | ||
2230 | while (n) { | |
2231 | if (__get_user(c, f)) { | |
2232 | memset(t, 0, n); | |
2233 | break; | |
2234 | } | |
2235 | *t++ = c; | |
2236 | f++; | |
2237 | n--; | |
2238 | } | |
2239 | return n; | |
2240 | } | |
2241 | ||
2242 | int copy_mount_options(const void __user * data, unsigned long *where) | |
2243 | { | |
2244 | int i; | |
2245 | unsigned long page; | |
2246 | unsigned long size; | |
2247 | ||
2248 | *where = 0; | |
2249 | if (!data) | |
2250 | return 0; | |
2251 | ||
2252 | if (!(page = __get_free_page(GFP_KERNEL))) | |
2253 | return -ENOMEM; | |
2254 | ||
2255 | /* We only care that *some* data at the address the user | |
2256 | * gave us is valid. Just in case, we'll zero | |
2257 | * the remainder of the page. | |
2258 | */ | |
2259 | /* copy_from_user cannot cross TASK_SIZE ! */ | |
2260 | size = TASK_SIZE - (unsigned long)data; | |
2261 | if (size > PAGE_SIZE) | |
2262 | size = PAGE_SIZE; | |
2263 | ||
2264 | i = size - exact_copy_from_user((void *)page, data, size); | |
2265 | if (!i) { | |
2266 | free_page(page); | |
2267 | return -EFAULT; | |
2268 | } | |
2269 | if (i != PAGE_SIZE) | |
2270 | memset((char *)page + i, 0, PAGE_SIZE - i); | |
2271 | *where = page; | |
2272 | return 0; | |
2273 | } | |
2274 | ||
2275 | int copy_mount_string(const void __user *data, char **where) | |
2276 | { | |
2277 | char *tmp; | |
2278 | ||
2279 | if (!data) { | |
2280 | *where = NULL; | |
2281 | return 0; | |
2282 | } | |
2283 | ||
2284 | tmp = strndup_user(data, PAGE_SIZE); | |
2285 | if (IS_ERR(tmp)) | |
2286 | return PTR_ERR(tmp); | |
2287 | ||
2288 | *where = tmp; | |
2289 | return 0; | |
2290 | } | |
2291 | ||
2292 | /* | |
2293 | * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to | |
2294 | * be given to the mount() call (ie: read-only, no-dev, no-suid etc). | |
2295 | * | |
2296 | * data is a (void *) that can point to any structure up to | |
2297 | * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent | |
2298 | * information (or be NULL). | |
2299 | * | |
2300 | * Pre-0.97 versions of mount() didn't have a flags word. | |
2301 | * When the flags word was introduced its top half was required | |
2302 | * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. | |
2303 | * Therefore, if this magic number is present, it carries no information | |
2304 | * and must be discarded. | |
2305 | */ | |
2306 | long do_mount(const char *dev_name, const char *dir_name, | |
2307 | const char *type_page, unsigned long flags, void *data_page) | |
2308 | { | |
2309 | struct path path; | |
2310 | int retval = 0; | |
2311 | int mnt_flags = 0; | |
2312 | ||
2313 | /* Discard magic */ | |
2314 | if ((flags & MS_MGC_MSK) == MS_MGC_VAL) | |
2315 | flags &= ~MS_MGC_MSK; | |
2316 | ||
2317 | /* Basic sanity checks */ | |
2318 | ||
2319 | if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) | |
2320 | return -EINVAL; | |
2321 | ||
2322 | if (data_page) | |
2323 | ((char *)data_page)[PAGE_SIZE - 1] = 0; | |
2324 | ||
2325 | /* ... and get the mountpoint */ | |
2326 | retval = kern_path(dir_name, LOOKUP_FOLLOW, &path); | |
2327 | if (retval) | |
2328 | return retval; | |
2329 | ||
2330 | retval = security_sb_mount(dev_name, &path, | |
2331 | type_page, flags, data_page); | |
2332 | if (!retval && !may_mount()) | |
2333 | retval = -EPERM; | |
2334 | if (retval) | |
2335 | goto dput_out; | |
2336 | ||
2337 | /* Default to relatime unless overriden */ | |
2338 | if (!(flags & MS_NOATIME)) | |
2339 | mnt_flags |= MNT_RELATIME; | |
2340 | ||
2341 | /* Separate the per-mountpoint flags */ | |
2342 | if (flags & MS_NOSUID) | |
2343 | mnt_flags |= MNT_NOSUID; | |
2344 | if (flags & MS_NODEV) | |
2345 | mnt_flags |= MNT_NODEV; | |
2346 | if (flags & MS_NOEXEC) | |
2347 | mnt_flags |= MNT_NOEXEC; | |
2348 | if (flags & MS_NOATIME) | |
2349 | mnt_flags |= MNT_NOATIME; | |
2350 | if (flags & MS_NODIRATIME) | |
2351 | mnt_flags |= MNT_NODIRATIME; | |
2352 | if (flags & MS_STRICTATIME) | |
2353 | mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); | |
2354 | if (flags & MS_RDONLY) | |
2355 | mnt_flags |= MNT_READONLY; | |
2356 | ||
2357 | flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN | | |
2358 | MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT | | |
2359 | MS_STRICTATIME); | |
2360 | ||
2361 | if (flags & MS_REMOUNT) | |
2362 | retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags, | |
2363 | data_page); | |
2364 | else if (flags & MS_BIND) | |
2365 | retval = do_loopback(&path, dev_name, flags & MS_REC); | |
2366 | else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) | |
2367 | retval = do_change_type(&path, flags); | |
2368 | else if (flags & MS_MOVE) | |
2369 | retval = do_move_mount(&path, dev_name); | |
2370 | else | |
2371 | retval = do_new_mount(&path, type_page, flags, mnt_flags, | |
2372 | dev_name, data_page); | |
2373 | dput_out: | |
2374 | path_put(&path); | |
2375 | return retval; | |
2376 | } | |
2377 | ||
2378 | static void free_mnt_ns(struct mnt_namespace *ns) | |
2379 | { | |
2380 | proc_free_inum(ns->proc_inum); | |
2381 | put_user_ns(ns->user_ns); | |
2382 | kfree(ns); | |
2383 | } | |
2384 | ||
2385 | /* | |
2386 | * Assign a sequence number so we can detect when we attempt to bind | |
2387 | * mount a reference to an older mount namespace into the current | |
2388 | * mount namespace, preventing reference counting loops. A 64bit | |
2389 | * number incrementing at 10Ghz will take 12,427 years to wrap which | |
2390 | * is effectively never, so we can ignore the possibility. | |
2391 | */ | |
2392 | static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1); | |
2393 | ||
2394 | static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns) | |
2395 | { | |
2396 | struct mnt_namespace *new_ns; | |
2397 | int ret; | |
2398 | ||
2399 | new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); | |
2400 | if (!new_ns) | |
2401 | return ERR_PTR(-ENOMEM); | |
2402 | ret = proc_alloc_inum(&new_ns->proc_inum); | |
2403 | if (ret) { | |
2404 | kfree(new_ns); | |
2405 | return ERR_PTR(ret); | |
2406 | } | |
2407 | new_ns->seq = atomic64_add_return(1, &mnt_ns_seq); | |
2408 | atomic_set(&new_ns->count, 1); | |
2409 | new_ns->root = NULL; | |
2410 | INIT_LIST_HEAD(&new_ns->list); | |
2411 | init_waitqueue_head(&new_ns->poll); | |
2412 | new_ns->event = 0; | |
2413 | new_ns->user_ns = get_user_ns(user_ns); | |
2414 | return new_ns; | |
2415 | } | |
2416 | ||
2417 | /* | |
2418 | * Allocate a new namespace structure and populate it with contents | |
2419 | * copied from the namespace of the passed in task structure. | |
2420 | */ | |
2421 | static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns, | |
2422 | struct user_namespace *user_ns, struct fs_struct *fs) | |
2423 | { | |
2424 | struct mnt_namespace *new_ns; | |
2425 | struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; | |
2426 | struct mount *p, *q; | |
2427 | struct mount *old = mnt_ns->root; | |
2428 | struct mount *new; | |
2429 | int copy_flags; | |
2430 | ||
2431 | new_ns = alloc_mnt_ns(user_ns); | |
2432 | if (IS_ERR(new_ns)) | |
2433 | return new_ns; | |
2434 | ||
2435 | namespace_lock(); | |
2436 | /* First pass: copy the tree topology */ | |
2437 | copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE; | |
2438 | if (user_ns != mnt_ns->user_ns) | |
2439 | copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED; | |
2440 | new = copy_tree(old, old->mnt.mnt_root, copy_flags); | |
2441 | if (IS_ERR(new)) { | |
2442 | namespace_unlock(); | |
2443 | free_mnt_ns(new_ns); | |
2444 | return ERR_CAST(new); | |
2445 | } | |
2446 | new_ns->root = new; | |
2447 | list_add_tail(&new_ns->list, &new->mnt_list); | |
2448 | ||
2449 | /* | |
2450 | * Second pass: switch the tsk->fs->* elements and mark new vfsmounts | |
2451 | * as belonging to new namespace. We have already acquired a private | |
2452 | * fs_struct, so tsk->fs->lock is not needed. | |
2453 | */ | |
2454 | p = old; | |
2455 | q = new; | |
2456 | while (p) { | |
2457 | q->mnt_ns = new_ns; | |
2458 | if (fs) { | |
2459 | if (&p->mnt == fs->root.mnt) { | |
2460 | fs->root.mnt = mntget(&q->mnt); | |
2461 | rootmnt = &p->mnt; | |
2462 | } | |
2463 | if (&p->mnt == fs->pwd.mnt) { | |
2464 | fs->pwd.mnt = mntget(&q->mnt); | |
2465 | pwdmnt = &p->mnt; | |
2466 | } | |
2467 | } | |
2468 | p = next_mnt(p, old); | |
2469 | q = next_mnt(q, new); | |
2470 | if (!q) | |
2471 | break; | |
2472 | while (p->mnt.mnt_root != q->mnt.mnt_root) | |
2473 | p = next_mnt(p, old); | |
2474 | } | |
2475 | namespace_unlock(); | |
2476 | ||
2477 | if (rootmnt) | |
2478 | mntput(rootmnt); | |
2479 | if (pwdmnt) | |
2480 | mntput(pwdmnt); | |
2481 | ||
2482 | return new_ns; | |
2483 | } | |
2484 | ||
2485 | struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, | |
2486 | struct user_namespace *user_ns, struct fs_struct *new_fs) | |
2487 | { | |
2488 | struct mnt_namespace *new_ns; | |
2489 | ||
2490 | BUG_ON(!ns); | |
2491 | get_mnt_ns(ns); | |
2492 | ||
2493 | if (!(flags & CLONE_NEWNS)) | |
2494 | return ns; | |
2495 | ||
2496 | new_ns = dup_mnt_ns(ns, user_ns, new_fs); | |
2497 | ||
2498 | put_mnt_ns(ns); | |
2499 | return new_ns; | |
2500 | } | |
2501 | ||
2502 | /** | |
2503 | * create_mnt_ns - creates a private namespace and adds a root filesystem | |
2504 | * @mnt: pointer to the new root filesystem mountpoint | |
2505 | */ | |
2506 | static struct mnt_namespace *create_mnt_ns(struct vfsmount *m) | |
2507 | { | |
2508 | struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns); | |
2509 | if (!IS_ERR(new_ns)) { | |
2510 | struct mount *mnt = real_mount(m); | |
2511 | mnt->mnt_ns = new_ns; | |
2512 | new_ns->root = mnt; | |
2513 | list_add(&mnt->mnt_list, &new_ns->list); | |
2514 | } else { | |
2515 | mntput(m); | |
2516 | } | |
2517 | return new_ns; | |
2518 | } | |
2519 | ||
2520 | struct dentry *mount_subtree(struct vfsmount *mnt, const char *name) | |
2521 | { | |
2522 | struct mnt_namespace *ns; | |
2523 | struct super_block *s; | |
2524 | struct path path; | |
2525 | int err; | |
2526 | ||
2527 | ns = create_mnt_ns(mnt); | |
2528 | if (IS_ERR(ns)) | |
2529 | return ERR_CAST(ns); | |
2530 | ||
2531 | err = vfs_path_lookup(mnt->mnt_root, mnt, | |
2532 | name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); | |
2533 | ||
2534 | put_mnt_ns(ns); | |
2535 | ||
2536 | if (err) | |
2537 | return ERR_PTR(err); | |
2538 | ||
2539 | /* trade a vfsmount reference for active sb one */ | |
2540 | s = path.mnt->mnt_sb; | |
2541 | atomic_inc(&s->s_active); | |
2542 | mntput(path.mnt); | |
2543 | /* lock the sucker */ | |
2544 | down_write(&s->s_umount); | |
2545 | /* ... and return the root of (sub)tree on it */ | |
2546 | return path.dentry; | |
2547 | } | |
2548 | EXPORT_SYMBOL(mount_subtree); | |
2549 | ||
2550 | SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, | |
2551 | char __user *, type, unsigned long, flags, void __user *, data) | |
2552 | { | |
2553 | int ret; | |
2554 | char *kernel_type; | |
2555 | struct filename *kernel_dir; | |
2556 | char *kernel_dev; | |
2557 | unsigned long data_page; | |
2558 | ||
2559 | ret = copy_mount_string(type, &kernel_type); | |
2560 | if (ret < 0) | |
2561 | goto out_type; | |
2562 | ||
2563 | kernel_dir = getname(dir_name); | |
2564 | if (IS_ERR(kernel_dir)) { | |
2565 | ret = PTR_ERR(kernel_dir); | |
2566 | goto out_dir; | |
2567 | } | |
2568 | ||
2569 | ret = copy_mount_string(dev_name, &kernel_dev); | |
2570 | if (ret < 0) | |
2571 | goto out_dev; | |
2572 | ||
2573 | ret = copy_mount_options(data, &data_page); | |
2574 | if (ret < 0) | |
2575 | goto out_data; | |
2576 | ||
2577 | ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags, | |
2578 | (void *) data_page); | |
2579 | ||
2580 | free_page(data_page); | |
2581 | out_data: | |
2582 | kfree(kernel_dev); | |
2583 | out_dev: | |
2584 | putname(kernel_dir); | |
2585 | out_dir: | |
2586 | kfree(kernel_type); | |
2587 | out_type: | |
2588 | return ret; | |
2589 | } | |
2590 | ||
2591 | /* | |
2592 | * Return true if path is reachable from root | |
2593 | * | |
2594 | * namespace_sem or vfsmount_lock is held | |
2595 | */ | |
2596 | bool is_path_reachable(struct mount *mnt, struct dentry *dentry, | |
2597 | const struct path *root) | |
2598 | { | |
2599 | while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) { | |
2600 | dentry = mnt->mnt_mountpoint; | |
2601 | mnt = mnt->mnt_parent; | |
2602 | } | |
2603 | return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry); | |
2604 | } | |
2605 | ||
2606 | int path_is_under(struct path *path1, struct path *path2) | |
2607 | { | |
2608 | int res; | |
2609 | br_read_lock(&vfsmount_lock); | |
2610 | res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2); | |
2611 | br_read_unlock(&vfsmount_lock); | |
2612 | return res; | |
2613 | } | |
2614 | EXPORT_SYMBOL(path_is_under); | |
2615 | ||
2616 | /* | |
2617 | * pivot_root Semantics: | |
2618 | * Moves the root file system of the current process to the directory put_old, | |
2619 | * makes new_root as the new root file system of the current process, and sets | |
2620 | * root/cwd of all processes which had them on the current root to new_root. | |
2621 | * | |
2622 | * Restrictions: | |
2623 | * The new_root and put_old must be directories, and must not be on the | |
2624 | * same file system as the current process root. The put_old must be | |
2625 | * underneath new_root, i.e. adding a non-zero number of /.. to the string | |
2626 | * pointed to by put_old must yield the same directory as new_root. No other | |
2627 | * file system may be mounted on put_old. After all, new_root is a mountpoint. | |
2628 | * | |
2629 | * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. | |
2630 | * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives | |
2631 | * in this situation. | |
2632 | * | |
2633 | * Notes: | |
2634 | * - we don't move root/cwd if they are not at the root (reason: if something | |
2635 | * cared enough to change them, it's probably wrong to force them elsewhere) | |
2636 | * - it's okay to pick a root that isn't the root of a file system, e.g. | |
2637 | * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, | |
2638 | * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root | |
2639 | * first. | |
2640 | */ | |
2641 | SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, | |
2642 | const char __user *, put_old) | |
2643 | { | |
2644 | struct path new, old, parent_path, root_parent, root; | |
2645 | struct mount *new_mnt, *root_mnt, *old_mnt; | |
2646 | struct mountpoint *old_mp, *root_mp; | |
2647 | int error; | |
2648 | ||
2649 | if (!may_mount()) | |
2650 | return -EPERM; | |
2651 | ||
2652 | error = user_path_dir(new_root, &new); | |
2653 | if (error) | |
2654 | goto out0; | |
2655 | ||
2656 | error = user_path_dir(put_old, &old); | |
2657 | if (error) | |
2658 | goto out1; | |
2659 | ||
2660 | error = security_sb_pivotroot(&old, &new); | |
2661 | if (error) | |
2662 | goto out2; | |
2663 | ||
2664 | get_fs_root(current->fs, &root); | |
2665 | old_mp = lock_mount(&old); | |
2666 | error = PTR_ERR(old_mp); | |
2667 | if (IS_ERR(old_mp)) | |
2668 | goto out3; | |
2669 | ||
2670 | error = -EINVAL; | |
2671 | new_mnt = real_mount(new.mnt); | |
2672 | root_mnt = real_mount(root.mnt); | |
2673 | old_mnt = real_mount(old.mnt); | |
2674 | if (IS_MNT_SHARED(old_mnt) || | |
2675 | IS_MNT_SHARED(new_mnt->mnt_parent) || | |
2676 | IS_MNT_SHARED(root_mnt->mnt_parent)) | |
2677 | goto out4; | |
2678 | if (!check_mnt(root_mnt) || !check_mnt(new_mnt)) | |
2679 | goto out4; | |
2680 | if (new_mnt->mnt.mnt_flags & MNT_LOCKED) | |
2681 | goto out4; | |
2682 | error = -ENOENT; | |
2683 | if (d_unlinked(new.dentry)) | |
2684 | goto out4; | |
2685 | error = -EBUSY; | |
2686 | if (new_mnt == root_mnt || old_mnt == root_mnt) | |
2687 | goto out4; /* loop, on the same file system */ | |
2688 | error = -EINVAL; | |
2689 | if (root.mnt->mnt_root != root.dentry) | |
2690 | goto out4; /* not a mountpoint */ | |
2691 | if (!mnt_has_parent(root_mnt)) | |
2692 | goto out4; /* not attached */ | |
2693 | root_mp = root_mnt->mnt_mp; | |
2694 | if (new.mnt->mnt_root != new.dentry) | |
2695 | goto out4; /* not a mountpoint */ | |
2696 | if (!mnt_has_parent(new_mnt)) | |
2697 | goto out4; /* not attached */ | |
2698 | /* make sure we can reach put_old from new_root */ | |
2699 | if (!is_path_reachable(old_mnt, old.dentry, &new)) | |
2700 | goto out4; | |
2701 | root_mp->m_count++; /* pin it so it won't go away */ | |
2702 | br_write_lock(&vfsmount_lock); | |
2703 | detach_mnt(new_mnt, &parent_path); | |
2704 | detach_mnt(root_mnt, &root_parent); | |
2705 | if (root_mnt->mnt.mnt_flags & MNT_LOCKED) { | |
2706 | new_mnt->mnt.mnt_flags |= MNT_LOCKED; | |
2707 | root_mnt->mnt.mnt_flags &= ~MNT_LOCKED; | |
2708 | } | |
2709 | /* mount old root on put_old */ | |
2710 | attach_mnt(root_mnt, old_mnt, old_mp); | |
2711 | /* mount new_root on / */ | |
2712 | attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp); | |
2713 | touch_mnt_namespace(current->nsproxy->mnt_ns); | |
2714 | br_write_unlock(&vfsmount_lock); | |
2715 | chroot_fs_refs(&root, &new); | |
2716 | put_mountpoint(root_mp); | |
2717 | error = 0; | |
2718 | out4: | |
2719 | unlock_mount(old_mp); | |
2720 | if (!error) { | |
2721 | path_put(&root_parent); | |
2722 | path_put(&parent_path); | |
2723 | } | |
2724 | out3: | |
2725 | path_put(&root); | |
2726 | out2: | |
2727 | path_put(&old); | |
2728 | out1: | |
2729 | path_put(&new); | |
2730 | out0: | |
2731 | return error; | |
2732 | } | |
2733 | ||
2734 | static void __init init_mount_tree(void) | |
2735 | { | |
2736 | struct vfsmount *mnt; | |
2737 | struct mnt_namespace *ns; | |
2738 | struct path root; | |
2739 | struct file_system_type *type; | |
2740 | ||
2741 | type = get_fs_type("rootfs"); | |
2742 | if (!type) | |
2743 | panic("Can't find rootfs type"); | |
2744 | mnt = vfs_kern_mount(type, 0, "rootfs", NULL); | |
2745 | put_filesystem(type); | |
2746 | if (IS_ERR(mnt)) | |
2747 | panic("Can't create rootfs"); | |
2748 | ||
2749 | ns = create_mnt_ns(mnt); | |
2750 | if (IS_ERR(ns)) | |
2751 | panic("Can't allocate initial namespace"); | |
2752 | ||
2753 | init_task.nsproxy->mnt_ns = ns; | |
2754 | get_mnt_ns(ns); | |
2755 | ||
2756 | root.mnt = mnt; | |
2757 | root.dentry = mnt->mnt_root; | |
2758 | ||
2759 | set_fs_pwd(current->fs, &root); | |
2760 | set_fs_root(current->fs, &root); | |
2761 | } | |
2762 | ||
2763 | void __init mnt_init(void) | |
2764 | { | |
2765 | unsigned u; | |
2766 | int err; | |
2767 | ||
2768 | mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount), | |
2769 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); | |
2770 | ||
2771 | mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); | |
2772 | mountpoint_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); | |
2773 | ||
2774 | if (!mount_hashtable || !mountpoint_hashtable) | |
2775 | panic("Failed to allocate mount hash table\n"); | |
2776 | ||
2777 | printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE); | |
2778 | ||
2779 | for (u = 0; u < HASH_SIZE; u++) | |
2780 | INIT_LIST_HEAD(&mount_hashtable[u]); | |
2781 | for (u = 0; u < HASH_SIZE; u++) | |
2782 | INIT_LIST_HEAD(&mountpoint_hashtable[u]); | |
2783 | ||
2784 | br_lock_init(&vfsmount_lock); | |
2785 | ||
2786 | err = sysfs_init(); | |
2787 | if (err) | |
2788 | printk(KERN_WARNING "%s: sysfs_init error: %d\n", | |
2789 | __func__, err); | |
2790 | fs_kobj = kobject_create_and_add("fs", NULL); | |
2791 | if (!fs_kobj) | |
2792 | printk(KERN_WARNING "%s: kobj create error\n", __func__); | |
2793 | init_rootfs(); | |
2794 | init_mount_tree(); | |
2795 | } | |
2796 | ||
2797 | void put_mnt_ns(struct mnt_namespace *ns) | |
2798 | { | |
2799 | if (!atomic_dec_and_test(&ns->count)) | |
2800 | return; | |
2801 | drop_collected_mounts(&ns->root->mnt); | |
2802 | free_mnt_ns(ns); | |
2803 | } | |
2804 | ||
2805 | struct vfsmount *kern_mount_data(struct file_system_type *type, void *data) | |
2806 | { | |
2807 | struct vfsmount *mnt; | |
2808 | mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data); | |
2809 | if (!IS_ERR(mnt)) { | |
2810 | /* | |
2811 | * it is a longterm mount, don't release mnt until | |
2812 | * we unmount before file sys is unregistered | |
2813 | */ | |
2814 | real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL; | |
2815 | } | |
2816 | return mnt; | |
2817 | } | |
2818 | EXPORT_SYMBOL_GPL(kern_mount_data); | |
2819 | ||
2820 | void kern_unmount(struct vfsmount *mnt) | |
2821 | { | |
2822 | /* release long term mount so mount point can be released */ | |
2823 | if (!IS_ERR_OR_NULL(mnt)) { | |
2824 | br_write_lock(&vfsmount_lock); | |
2825 | real_mount(mnt)->mnt_ns = NULL; | |
2826 | br_write_unlock(&vfsmount_lock); | |
2827 | mntput(mnt); | |
2828 | } | |
2829 | } | |
2830 | EXPORT_SYMBOL(kern_unmount); | |
2831 | ||
2832 | bool our_mnt(struct vfsmount *mnt) | |
2833 | { | |
2834 | return check_mnt(real_mount(mnt)); | |
2835 | } | |
2836 | ||
2837 | bool current_chrooted(void) | |
2838 | { | |
2839 | /* Does the current process have a non-standard root */ | |
2840 | struct path ns_root; | |
2841 | struct path fs_root; | |
2842 | bool chrooted; | |
2843 | ||
2844 | /* Find the namespace root */ | |
2845 | ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt; | |
2846 | ns_root.dentry = ns_root.mnt->mnt_root; | |
2847 | path_get(&ns_root); | |
2848 | while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root)) | |
2849 | ; | |
2850 | ||
2851 | get_fs_root(current->fs, &fs_root); | |
2852 | ||
2853 | chrooted = !path_equal(&fs_root, &ns_root); | |
2854 | ||
2855 | path_put(&fs_root); | |
2856 | path_put(&ns_root); | |
2857 | ||
2858 | return chrooted; | |
2859 | } | |
2860 | ||
2861 | bool fs_fully_visible(struct file_system_type *type) | |
2862 | { | |
2863 | struct mnt_namespace *ns = current->nsproxy->mnt_ns; | |
2864 | struct mount *mnt; | |
2865 | bool visible = false; | |
2866 | ||
2867 | if (unlikely(!ns)) | |
2868 | return false; | |
2869 | ||
2870 | down_read(&namespace_sem); | |
2871 | list_for_each_entry(mnt, &ns->list, mnt_list) { | |
2872 | struct mount *child; | |
2873 | if (mnt->mnt.mnt_sb->s_type != type) | |
2874 | continue; | |
2875 | ||
2876 | /* This mount is not fully visible if there are any child mounts | |
2877 | * that cover anything except for empty directories. | |
2878 | */ | |
2879 | list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { | |
2880 | struct inode *inode = child->mnt_mountpoint->d_inode; | |
2881 | if (!S_ISDIR(inode->i_mode)) | |
2882 | goto next; | |
2883 | if (inode->i_nlink != 2) | |
2884 | goto next; | |
2885 | } | |
2886 | visible = true; | |
2887 | goto found; | |
2888 | next: ; | |
2889 | } | |
2890 | found: | |
2891 | up_read(&namespace_sem); | |
2892 | return visible; | |
2893 | } | |
2894 | ||
2895 | static void *mntns_get(struct task_struct *task) | |
2896 | { | |
2897 | struct mnt_namespace *ns = NULL; | |
2898 | struct nsproxy *nsproxy; | |
2899 | ||
2900 | rcu_read_lock(); | |
2901 | nsproxy = task_nsproxy(task); | |
2902 | if (nsproxy) { | |
2903 | ns = nsproxy->mnt_ns; | |
2904 | get_mnt_ns(ns); | |
2905 | } | |
2906 | rcu_read_unlock(); | |
2907 | ||
2908 | return ns; | |
2909 | } | |
2910 | ||
2911 | static void mntns_put(void *ns) | |
2912 | { | |
2913 | put_mnt_ns(ns); | |
2914 | } | |
2915 | ||
2916 | static int mntns_install(struct nsproxy *nsproxy, void *ns) | |
2917 | { | |
2918 | struct fs_struct *fs = current->fs; | |
2919 | struct mnt_namespace *mnt_ns = ns; | |
2920 | struct path root; | |
2921 | ||
2922 | if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) || | |
2923 | !ns_capable(current_user_ns(), CAP_SYS_CHROOT) || | |
2924 | !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) | |
2925 | return -EPERM; | |
2926 | ||
2927 | if (fs->users != 1) | |
2928 | return -EINVAL; | |
2929 | ||
2930 | get_mnt_ns(mnt_ns); | |
2931 | put_mnt_ns(nsproxy->mnt_ns); | |
2932 | nsproxy->mnt_ns = mnt_ns; | |
2933 | ||
2934 | /* Find the root */ | |
2935 | root.mnt = &mnt_ns->root->mnt; | |
2936 | root.dentry = mnt_ns->root->mnt.mnt_root; | |
2937 | path_get(&root); | |
2938 | while(d_mountpoint(root.dentry) && follow_down_one(&root)) | |
2939 | ; | |
2940 | ||
2941 | /* Update the pwd and root */ | |
2942 | set_fs_pwd(fs, &root); | |
2943 | set_fs_root(fs, &root); | |
2944 | ||
2945 | path_put(&root); | |
2946 | return 0; | |
2947 | } | |
2948 | ||
2949 | static unsigned int mntns_inum(void *ns) | |
2950 | { | |
2951 | struct mnt_namespace *mnt_ns = ns; | |
2952 | return mnt_ns->proc_inum; | |
2953 | } | |
2954 | ||
2955 | const struct proc_ns_operations mntns_operations = { | |
2956 | .name = "mnt", | |
2957 | .type = CLONE_NEWNS, | |
2958 | .get = mntns_get, | |
2959 | .put = mntns_put, | |
2960 | .install = mntns_install, | |
2961 | .inum = mntns_inum, | |
2962 | }; |