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1 | /* | |
2 | * linux/fs/namespace.c | |
3 | * | |
4 | * (C) Copyright Al Viro 2000, 2001 | |
5 | * Released under GPL v2. | |
6 | * | |
7 | * Based on code from fs/super.c, copyright Linus Torvalds and others. | |
8 | * Heavily rewritten. | |
9 | */ | |
10 | ||
11 | #include <linux/syscalls.h> | |
12 | #include <linux/export.h> | |
13 | #include <linux/capability.h> | |
14 | #include <linux/mnt_namespace.h> | |
15 | #include <linux/user_namespace.h> | |
16 | #include <linux/namei.h> | |
17 | #include <linux/security.h> | |
18 | #include <linux/idr.h> | |
19 | #include <linux/init.h> /* init_rootfs */ | |
20 | #include <linux/fs_struct.h> /* get_fs_root et.al. */ | |
21 | #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */ | |
22 | #include <linux/uaccess.h> | |
23 | #include <linux/proc_ns.h> | |
24 | #include <linux/magic.h> | |
25 | #include <linux/bootmem.h> | |
26 | #include <linux/task_work.h> | |
27 | #include "pnode.h" | |
28 | #include "internal.h" | |
29 | ||
30 | static unsigned int m_hash_mask __read_mostly; | |
31 | static unsigned int m_hash_shift __read_mostly; | |
32 | static unsigned int mp_hash_mask __read_mostly; | |
33 | static unsigned int mp_hash_shift __read_mostly; | |
34 | ||
35 | static __initdata unsigned long mhash_entries; | |
36 | static int __init set_mhash_entries(char *str) | |
37 | { | |
38 | if (!str) | |
39 | return 0; | |
40 | mhash_entries = simple_strtoul(str, &str, 0); | |
41 | return 1; | |
42 | } | |
43 | __setup("mhash_entries=", set_mhash_entries); | |
44 | ||
45 | static __initdata unsigned long mphash_entries; | |
46 | static int __init set_mphash_entries(char *str) | |
47 | { | |
48 | if (!str) | |
49 | return 0; | |
50 | mphash_entries = simple_strtoul(str, &str, 0); | |
51 | return 1; | |
52 | } | |
53 | __setup("mphash_entries=", set_mphash_entries); | |
54 | ||
55 | static u64 event; | |
56 | static DEFINE_IDA(mnt_id_ida); | |
57 | static DEFINE_IDA(mnt_group_ida); | |
58 | static DEFINE_SPINLOCK(mnt_id_lock); | |
59 | static int mnt_id_start = 0; | |
60 | static int mnt_group_start = 1; | |
61 | ||
62 | static struct hlist_head *mount_hashtable __read_mostly; | |
63 | static struct hlist_head *mountpoint_hashtable __read_mostly; | |
64 | static struct kmem_cache *mnt_cache __read_mostly; | |
65 | static DECLARE_RWSEM(namespace_sem); | |
66 | ||
67 | /* /sys/fs */ | |
68 | struct kobject *fs_kobj; | |
69 | EXPORT_SYMBOL_GPL(fs_kobj); | |
70 | ||
71 | /* | |
72 | * vfsmount lock may be taken for read to prevent changes to the | |
73 | * vfsmount hash, ie. during mountpoint lookups or walking back | |
74 | * up the tree. | |
75 | * | |
76 | * It should be taken for write in all cases where the vfsmount | |
77 | * tree or hash is modified or when a vfsmount structure is modified. | |
78 | */ | |
79 | __cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock); | |
80 | ||
81 | static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry) | |
82 | { | |
83 | unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); | |
84 | tmp += ((unsigned long)dentry / L1_CACHE_BYTES); | |
85 | tmp = tmp + (tmp >> m_hash_shift); | |
86 | return &mount_hashtable[tmp & m_hash_mask]; | |
87 | } | |
88 | ||
89 | static inline struct hlist_head *mp_hash(struct dentry *dentry) | |
90 | { | |
91 | unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES); | |
92 | tmp = tmp + (tmp >> mp_hash_shift); | |
93 | return &mountpoint_hashtable[tmp & mp_hash_mask]; | |
94 | } | |
95 | ||
96 | /* | |
97 | * allocation is serialized by namespace_sem, but we need the spinlock to | |
98 | * serialize with freeing. | |
99 | */ | |
100 | static int mnt_alloc_id(struct mount *mnt) | |
101 | { | |
102 | int res; | |
103 | ||
104 | retry: | |
105 | ida_pre_get(&mnt_id_ida, GFP_KERNEL); | |
106 | spin_lock(&mnt_id_lock); | |
107 | res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id); | |
108 | if (!res) | |
109 | mnt_id_start = mnt->mnt_id + 1; | |
110 | spin_unlock(&mnt_id_lock); | |
111 | if (res == -EAGAIN) | |
112 | goto retry; | |
113 | ||
114 | return res; | |
115 | } | |
116 | ||
117 | static void mnt_free_id(struct mount *mnt) | |
118 | { | |
119 | int id = mnt->mnt_id; | |
120 | spin_lock(&mnt_id_lock); | |
121 | ida_remove(&mnt_id_ida, id); | |
122 | if (mnt_id_start > id) | |
123 | mnt_id_start = id; | |
124 | spin_unlock(&mnt_id_lock); | |
125 | } | |
126 | ||
127 | /* | |
128 | * Allocate a new peer group ID | |
129 | * | |
130 | * mnt_group_ida is protected by namespace_sem | |
131 | */ | |
132 | static int mnt_alloc_group_id(struct mount *mnt) | |
133 | { | |
134 | int res; | |
135 | ||
136 | if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL)) | |
137 | return -ENOMEM; | |
138 | ||
139 | res = ida_get_new_above(&mnt_group_ida, | |
140 | mnt_group_start, | |
141 | &mnt->mnt_group_id); | |
142 | if (!res) | |
143 | mnt_group_start = mnt->mnt_group_id + 1; | |
144 | ||
145 | return res; | |
146 | } | |
147 | ||
148 | /* | |
149 | * Release a peer group ID | |
150 | */ | |
151 | void mnt_release_group_id(struct mount *mnt) | |
152 | { | |
153 | int id = mnt->mnt_group_id; | |
154 | ida_remove(&mnt_group_ida, id); | |
155 | if (mnt_group_start > id) | |
156 | mnt_group_start = id; | |
157 | mnt->mnt_group_id = 0; | |
158 | } | |
159 | ||
160 | /* | |
161 | * vfsmount lock must be held for read | |
162 | */ | |
163 | static inline void mnt_add_count(struct mount *mnt, int n) | |
164 | { | |
165 | #ifdef CONFIG_SMP | |
166 | this_cpu_add(mnt->mnt_pcp->mnt_count, n); | |
167 | #else | |
168 | preempt_disable(); | |
169 | mnt->mnt_count += n; | |
170 | preempt_enable(); | |
171 | #endif | |
172 | } | |
173 | ||
174 | /* | |
175 | * vfsmount lock must be held for write | |
176 | */ | |
177 | unsigned int mnt_get_count(struct mount *mnt) | |
178 | { | |
179 | #ifdef CONFIG_SMP | |
180 | unsigned int count = 0; | |
181 | int cpu; | |
182 | ||
183 | for_each_possible_cpu(cpu) { | |
184 | count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count; | |
185 | } | |
186 | ||
187 | return count; | |
188 | #else | |
189 | return mnt->mnt_count; | |
190 | #endif | |
191 | } | |
192 | ||
193 | static void drop_mountpoint(struct fs_pin *p) | |
194 | { | |
195 | struct mount *m = container_of(p, struct mount, mnt_umount); | |
196 | dput(m->mnt_ex_mountpoint); | |
197 | pin_remove(p); | |
198 | mntput(&m->mnt); | |
199 | } | |
200 | ||
201 | static struct mount *alloc_vfsmnt(const char *name) | |
202 | { | |
203 | struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); | |
204 | if (mnt) { | |
205 | int err; | |
206 | ||
207 | err = mnt_alloc_id(mnt); | |
208 | if (err) | |
209 | goto out_free_cache; | |
210 | ||
211 | if (name) { | |
212 | mnt->mnt_devname = kstrdup_const(name, GFP_KERNEL); | |
213 | if (!mnt->mnt_devname) | |
214 | goto out_free_id; | |
215 | } | |
216 | ||
217 | #ifdef CONFIG_SMP | |
218 | mnt->mnt_pcp = alloc_percpu(struct mnt_pcp); | |
219 | if (!mnt->mnt_pcp) | |
220 | goto out_free_devname; | |
221 | ||
222 | this_cpu_add(mnt->mnt_pcp->mnt_count, 1); | |
223 | #else | |
224 | mnt->mnt_count = 1; | |
225 | mnt->mnt_writers = 0; | |
226 | #endif | |
227 | ||
228 | INIT_HLIST_NODE(&mnt->mnt_hash); | |
229 | INIT_LIST_HEAD(&mnt->mnt_child); | |
230 | INIT_LIST_HEAD(&mnt->mnt_mounts); | |
231 | INIT_LIST_HEAD(&mnt->mnt_list); | |
232 | INIT_LIST_HEAD(&mnt->mnt_expire); | |
233 | INIT_LIST_HEAD(&mnt->mnt_share); | |
234 | INIT_LIST_HEAD(&mnt->mnt_slave_list); | |
235 | INIT_LIST_HEAD(&mnt->mnt_slave); | |
236 | INIT_HLIST_NODE(&mnt->mnt_mp_list); | |
237 | #ifdef CONFIG_FSNOTIFY | |
238 | INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks); | |
239 | #endif | |
240 | init_fs_pin(&mnt->mnt_umount, drop_mountpoint); | |
241 | } | |
242 | return mnt; | |
243 | ||
244 | #ifdef CONFIG_SMP | |
245 | out_free_devname: | |
246 | kfree_const(mnt->mnt_devname); | |
247 | #endif | |
248 | out_free_id: | |
249 | mnt_free_id(mnt); | |
250 | out_free_cache: | |
251 | kmem_cache_free(mnt_cache, mnt); | |
252 | return NULL; | |
253 | } | |
254 | ||
255 | /* | |
256 | * Most r/o checks on a fs are for operations that take | |
257 | * discrete amounts of time, like a write() or unlink(). | |
258 | * We must keep track of when those operations start | |
259 | * (for permission checks) and when they end, so that | |
260 | * we can determine when writes are able to occur to | |
261 | * a filesystem. | |
262 | */ | |
263 | /* | |
264 | * __mnt_is_readonly: check whether a mount is read-only | |
265 | * @mnt: the mount to check for its write status | |
266 | * | |
267 | * This shouldn't be used directly ouside of the VFS. | |
268 | * It does not guarantee that the filesystem will stay | |
269 | * r/w, just that it is right *now*. This can not and | |
270 | * should not be used in place of IS_RDONLY(inode). | |
271 | * mnt_want/drop_write() will _keep_ the filesystem | |
272 | * r/w. | |
273 | */ | |
274 | int __mnt_is_readonly(struct vfsmount *mnt) | |
275 | { | |
276 | if (mnt->mnt_flags & MNT_READONLY) | |
277 | return 1; | |
278 | if (mnt->mnt_sb->s_flags & MS_RDONLY) | |
279 | return 1; | |
280 | return 0; | |
281 | } | |
282 | EXPORT_SYMBOL_GPL(__mnt_is_readonly); | |
283 | ||
284 | static inline void mnt_inc_writers(struct mount *mnt) | |
285 | { | |
286 | #ifdef CONFIG_SMP | |
287 | this_cpu_inc(mnt->mnt_pcp->mnt_writers); | |
288 | #else | |
289 | mnt->mnt_writers++; | |
290 | #endif | |
291 | } | |
292 | ||
293 | static inline void mnt_dec_writers(struct mount *mnt) | |
294 | { | |
295 | #ifdef CONFIG_SMP | |
296 | this_cpu_dec(mnt->mnt_pcp->mnt_writers); | |
297 | #else | |
298 | mnt->mnt_writers--; | |
299 | #endif | |
300 | } | |
301 | ||
302 | static unsigned int mnt_get_writers(struct mount *mnt) | |
303 | { | |
304 | #ifdef CONFIG_SMP | |
305 | unsigned int count = 0; | |
306 | int cpu; | |
307 | ||
308 | for_each_possible_cpu(cpu) { | |
309 | count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers; | |
310 | } | |
311 | ||
312 | return count; | |
313 | #else | |
314 | return mnt->mnt_writers; | |
315 | #endif | |
316 | } | |
317 | ||
318 | static int mnt_is_readonly(struct vfsmount *mnt) | |
319 | { | |
320 | if (mnt->mnt_sb->s_readonly_remount) | |
321 | return 1; | |
322 | /* Order wrt setting s_flags/s_readonly_remount in do_remount() */ | |
323 | smp_rmb(); | |
324 | return __mnt_is_readonly(mnt); | |
325 | } | |
326 | ||
327 | /* | |
328 | * Most r/o & frozen checks on a fs are for operations that take discrete | |
329 | * amounts of time, like a write() or unlink(). We must keep track of when | |
330 | * those operations start (for permission checks) and when they end, so that we | |
331 | * can determine when writes are able to occur to a filesystem. | |
332 | */ | |
333 | /** | |
334 | * __mnt_want_write - get write access to a mount without freeze protection | |
335 | * @m: the mount on which to take a write | |
336 | * | |
337 | * This tells the low-level filesystem that a write is about to be performed to | |
338 | * it, and makes sure that writes are allowed (mnt it read-write) before | |
339 | * returning success. This operation does not protect against filesystem being | |
340 | * frozen. When the write operation is finished, __mnt_drop_write() must be | |
341 | * called. This is effectively a refcount. | |
342 | */ | |
343 | int __mnt_want_write(struct vfsmount *m) | |
344 | { | |
345 | struct mount *mnt = real_mount(m); | |
346 | int ret = 0; | |
347 | ||
348 | preempt_disable(); | |
349 | mnt_inc_writers(mnt); | |
350 | /* | |
351 | * The store to mnt_inc_writers must be visible before we pass | |
352 | * MNT_WRITE_HOLD loop below, so that the slowpath can see our | |
353 | * incremented count after it has set MNT_WRITE_HOLD. | |
354 | */ | |
355 | smp_mb(); | |
356 | while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) | |
357 | cpu_relax(); | |
358 | /* | |
359 | * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will | |
360 | * be set to match its requirements. So we must not load that until | |
361 | * MNT_WRITE_HOLD is cleared. | |
362 | */ | |
363 | smp_rmb(); | |
364 | if (mnt_is_readonly(m)) { | |
365 | mnt_dec_writers(mnt); | |
366 | ret = -EROFS; | |
367 | } | |
368 | preempt_enable(); | |
369 | ||
370 | return ret; | |
371 | } | |
372 | ||
373 | /** | |
374 | * mnt_want_write - get write access to a mount | |
375 | * @m: the mount on which to take a write | |
376 | * | |
377 | * This tells the low-level filesystem that a write is about to be performed to | |
378 | * it, and makes sure that writes are allowed (mount is read-write, filesystem | |
379 | * is not frozen) before returning success. When the write operation is | |
380 | * finished, mnt_drop_write() must be called. This is effectively a refcount. | |
381 | */ | |
382 | int mnt_want_write(struct vfsmount *m) | |
383 | { | |
384 | int ret; | |
385 | ||
386 | sb_start_write(m->mnt_sb); | |
387 | ret = __mnt_want_write(m); | |
388 | if (ret) | |
389 | sb_end_write(m->mnt_sb); | |
390 | return ret; | |
391 | } | |
392 | EXPORT_SYMBOL_GPL(mnt_want_write); | |
393 | ||
394 | /** | |
395 | * mnt_clone_write - get write access to a mount | |
396 | * @mnt: the mount on which to take a write | |
397 | * | |
398 | * This is effectively like mnt_want_write, except | |
399 | * it must only be used to take an extra write reference | |
400 | * on a mountpoint that we already know has a write reference | |
401 | * on it. This allows some optimisation. | |
402 | * | |
403 | * After finished, mnt_drop_write must be called as usual to | |
404 | * drop the reference. | |
405 | */ | |
406 | int mnt_clone_write(struct vfsmount *mnt) | |
407 | { | |
408 | /* superblock may be r/o */ | |
409 | if (__mnt_is_readonly(mnt)) | |
410 | return -EROFS; | |
411 | preempt_disable(); | |
412 | mnt_inc_writers(real_mount(mnt)); | |
413 | preempt_enable(); | |
414 | return 0; | |
415 | } | |
416 | EXPORT_SYMBOL_GPL(mnt_clone_write); | |
417 | ||
418 | /** | |
419 | * __mnt_want_write_file - get write access to a file's mount | |
420 | * @file: the file who's mount on which to take a write | |
421 | * | |
422 | * This is like __mnt_want_write, but it takes a file and can | |
423 | * do some optimisations if the file is open for write already | |
424 | */ | |
425 | int __mnt_want_write_file(struct file *file) | |
426 | { | |
427 | if (!(file->f_mode & FMODE_WRITER)) | |
428 | return __mnt_want_write(file->f_path.mnt); | |
429 | else | |
430 | return mnt_clone_write(file->f_path.mnt); | |
431 | } | |
432 | ||
433 | /** | |
434 | * mnt_want_write_file - get write access to a file's mount | |
435 | * @file: the file who's mount on which to take a write | |
436 | * | |
437 | * This is like mnt_want_write, but it takes a file and can | |
438 | * do some optimisations if the file is open for write already | |
439 | */ | |
440 | int mnt_want_write_file(struct file *file) | |
441 | { | |
442 | int ret; | |
443 | ||
444 | sb_start_write(file->f_path.mnt->mnt_sb); | |
445 | ret = __mnt_want_write_file(file); | |
446 | if (ret) | |
447 | sb_end_write(file->f_path.mnt->mnt_sb); | |
448 | return ret; | |
449 | } | |
450 | EXPORT_SYMBOL_GPL(mnt_want_write_file); | |
451 | ||
452 | /** | |
453 | * __mnt_drop_write - give up write access to a mount | |
454 | * @mnt: the mount on which to give up write access | |
455 | * | |
456 | * Tells the low-level filesystem that we are done | |
457 | * performing writes to it. Must be matched with | |
458 | * __mnt_want_write() call above. | |
459 | */ | |
460 | void __mnt_drop_write(struct vfsmount *mnt) | |
461 | { | |
462 | preempt_disable(); | |
463 | mnt_dec_writers(real_mount(mnt)); | |
464 | preempt_enable(); | |
465 | } | |
466 | ||
467 | /** | |
468 | * mnt_drop_write - give up write access to a mount | |
469 | * @mnt: the mount on which to give up write access | |
470 | * | |
471 | * Tells the low-level filesystem that we are done performing writes to it and | |
472 | * also allows filesystem to be frozen again. Must be matched with | |
473 | * mnt_want_write() call above. | |
474 | */ | |
475 | void mnt_drop_write(struct vfsmount *mnt) | |
476 | { | |
477 | __mnt_drop_write(mnt); | |
478 | sb_end_write(mnt->mnt_sb); | |
479 | } | |
480 | EXPORT_SYMBOL_GPL(mnt_drop_write); | |
481 | ||
482 | void __mnt_drop_write_file(struct file *file) | |
483 | { | |
484 | __mnt_drop_write(file->f_path.mnt); | |
485 | } | |
486 | ||
487 | void mnt_drop_write_file(struct file *file) | |
488 | { | |
489 | mnt_drop_write(file->f_path.mnt); | |
490 | } | |
491 | EXPORT_SYMBOL(mnt_drop_write_file); | |
492 | ||
493 | static int mnt_make_readonly(struct mount *mnt) | |
494 | { | |
495 | int ret = 0; | |
496 | ||
497 | lock_mount_hash(); | |
498 | mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; | |
499 | /* | |
500 | * After storing MNT_WRITE_HOLD, we'll read the counters. This store | |
501 | * should be visible before we do. | |
502 | */ | |
503 | smp_mb(); | |
504 | ||
505 | /* | |
506 | * With writers on hold, if this value is zero, then there are | |
507 | * definitely no active writers (although held writers may subsequently | |
508 | * increment the count, they'll have to wait, and decrement it after | |
509 | * seeing MNT_READONLY). | |
510 | * | |
511 | * It is OK to have counter incremented on one CPU and decremented on | |
512 | * another: the sum will add up correctly. The danger would be when we | |
513 | * sum up each counter, if we read a counter before it is incremented, | |
514 | * but then read another CPU's count which it has been subsequently | |
515 | * decremented from -- we would see more decrements than we should. | |
516 | * MNT_WRITE_HOLD protects against this scenario, because | |
517 | * mnt_want_write first increments count, then smp_mb, then spins on | |
518 | * MNT_WRITE_HOLD, so it can't be decremented by another CPU while | |
519 | * we're counting up here. | |
520 | */ | |
521 | if (mnt_get_writers(mnt) > 0) | |
522 | ret = -EBUSY; | |
523 | else | |
524 | mnt->mnt.mnt_flags |= MNT_READONLY; | |
525 | /* | |
526 | * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers | |
527 | * that become unheld will see MNT_READONLY. | |
528 | */ | |
529 | smp_wmb(); | |
530 | mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; | |
531 | unlock_mount_hash(); | |
532 | return ret; | |
533 | } | |
534 | ||
535 | static void __mnt_unmake_readonly(struct mount *mnt) | |
536 | { | |
537 | lock_mount_hash(); | |
538 | mnt->mnt.mnt_flags &= ~MNT_READONLY; | |
539 | unlock_mount_hash(); | |
540 | } | |
541 | ||
542 | int sb_prepare_remount_readonly(struct super_block *sb) | |
543 | { | |
544 | struct mount *mnt; | |
545 | int err = 0; | |
546 | ||
547 | /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */ | |
548 | if (atomic_long_read(&sb->s_remove_count)) | |
549 | return -EBUSY; | |
550 | ||
551 | lock_mount_hash(); | |
552 | list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { | |
553 | if (!(mnt->mnt.mnt_flags & MNT_READONLY)) { | |
554 | mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; | |
555 | smp_mb(); | |
556 | if (mnt_get_writers(mnt) > 0) { | |
557 | err = -EBUSY; | |
558 | break; | |
559 | } | |
560 | } | |
561 | } | |
562 | if (!err && atomic_long_read(&sb->s_remove_count)) | |
563 | err = -EBUSY; | |
564 | ||
565 | if (!err) { | |
566 | sb->s_readonly_remount = 1; | |
567 | smp_wmb(); | |
568 | } | |
569 | list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { | |
570 | if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD) | |
571 | mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; | |
572 | } | |
573 | unlock_mount_hash(); | |
574 | ||
575 | return err; | |
576 | } | |
577 | ||
578 | static void free_vfsmnt(struct mount *mnt) | |
579 | { | |
580 | kfree_const(mnt->mnt_devname); | |
581 | #ifdef CONFIG_SMP | |
582 | free_percpu(mnt->mnt_pcp); | |
583 | #endif | |
584 | kmem_cache_free(mnt_cache, mnt); | |
585 | } | |
586 | ||
587 | static void delayed_free_vfsmnt(struct rcu_head *head) | |
588 | { | |
589 | free_vfsmnt(container_of(head, struct mount, mnt_rcu)); | |
590 | } | |
591 | ||
592 | /* call under rcu_read_lock */ | |
593 | int __legitimize_mnt(struct vfsmount *bastard, unsigned seq) | |
594 | { | |
595 | struct mount *mnt; | |
596 | if (read_seqretry(&mount_lock, seq)) | |
597 | return 1; | |
598 | if (bastard == NULL) | |
599 | return 0; | |
600 | mnt = real_mount(bastard); | |
601 | mnt_add_count(mnt, 1); | |
602 | if (likely(!read_seqretry(&mount_lock, seq))) | |
603 | return 0; | |
604 | if (bastard->mnt_flags & MNT_SYNC_UMOUNT) { | |
605 | mnt_add_count(mnt, -1); | |
606 | return 1; | |
607 | } | |
608 | return -1; | |
609 | } | |
610 | ||
611 | /* call under rcu_read_lock */ | |
612 | bool legitimize_mnt(struct vfsmount *bastard, unsigned seq) | |
613 | { | |
614 | int res = __legitimize_mnt(bastard, seq); | |
615 | if (likely(!res)) | |
616 | return true; | |
617 | if (unlikely(res < 0)) { | |
618 | rcu_read_unlock(); | |
619 | mntput(bastard); | |
620 | rcu_read_lock(); | |
621 | } | |
622 | return false; | |
623 | } | |
624 | ||
625 | /* | |
626 | * find the first mount at @dentry on vfsmount @mnt. | |
627 | * call under rcu_read_lock() | |
628 | */ | |
629 | struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry) | |
630 | { | |
631 | struct hlist_head *head = m_hash(mnt, dentry); | |
632 | struct mount *p; | |
633 | ||
634 | hlist_for_each_entry_rcu(p, head, mnt_hash) | |
635 | if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) | |
636 | return p; | |
637 | return NULL; | |
638 | } | |
639 | ||
640 | /* | |
641 | * find the last mount at @dentry on vfsmount @mnt. | |
642 | * mount_lock must be held. | |
643 | */ | |
644 | struct mount *__lookup_mnt_last(struct vfsmount *mnt, struct dentry *dentry) | |
645 | { | |
646 | struct mount *p, *res = NULL; | |
647 | p = __lookup_mnt(mnt, dentry); | |
648 | if (!p) | |
649 | goto out; | |
650 | if (!(p->mnt.mnt_flags & MNT_UMOUNT)) | |
651 | res = p; | |
652 | hlist_for_each_entry_continue(p, mnt_hash) { | |
653 | if (&p->mnt_parent->mnt != mnt || p->mnt_mountpoint != dentry) | |
654 | break; | |
655 | if (!(p->mnt.mnt_flags & MNT_UMOUNT)) | |
656 | res = p; | |
657 | } | |
658 | out: | |
659 | return res; | |
660 | } | |
661 | ||
662 | /* | |
663 | * lookup_mnt - Return the first child mount mounted at path | |
664 | * | |
665 | * "First" means first mounted chronologically. If you create the | |
666 | * following mounts: | |
667 | * | |
668 | * mount /dev/sda1 /mnt | |
669 | * mount /dev/sda2 /mnt | |
670 | * mount /dev/sda3 /mnt | |
671 | * | |
672 | * Then lookup_mnt() on the base /mnt dentry in the root mount will | |
673 | * return successively the root dentry and vfsmount of /dev/sda1, then | |
674 | * /dev/sda2, then /dev/sda3, then NULL. | |
675 | * | |
676 | * lookup_mnt takes a reference to the found vfsmount. | |
677 | */ | |
678 | struct vfsmount *lookup_mnt(struct path *path) | |
679 | { | |
680 | struct mount *child_mnt; | |
681 | struct vfsmount *m; | |
682 | unsigned seq; | |
683 | ||
684 | rcu_read_lock(); | |
685 | do { | |
686 | seq = read_seqbegin(&mount_lock); | |
687 | child_mnt = __lookup_mnt(path->mnt, path->dentry); | |
688 | m = child_mnt ? &child_mnt->mnt : NULL; | |
689 | } while (!legitimize_mnt(m, seq)); | |
690 | rcu_read_unlock(); | |
691 | return m; | |
692 | } | |
693 | ||
694 | /* | |
695 | * __is_local_mountpoint - Test to see if dentry is a mountpoint in the | |
696 | * current mount namespace. | |
697 | * | |
698 | * The common case is dentries are not mountpoints at all and that | |
699 | * test is handled inline. For the slow case when we are actually | |
700 | * dealing with a mountpoint of some kind, walk through all of the | |
701 | * mounts in the current mount namespace and test to see if the dentry | |
702 | * is a mountpoint. | |
703 | * | |
704 | * The mount_hashtable is not usable in the context because we | |
705 | * need to identify all mounts that may be in the current mount | |
706 | * namespace not just a mount that happens to have some specified | |
707 | * parent mount. | |
708 | */ | |
709 | bool __is_local_mountpoint(struct dentry *dentry) | |
710 | { | |
711 | struct mnt_namespace *ns = current->nsproxy->mnt_ns; | |
712 | struct mount *mnt; | |
713 | bool is_covered = false; | |
714 | ||
715 | if (!d_mountpoint(dentry)) | |
716 | goto out; | |
717 | ||
718 | down_read(&namespace_sem); | |
719 | list_for_each_entry(mnt, &ns->list, mnt_list) { | |
720 | is_covered = (mnt->mnt_mountpoint == dentry); | |
721 | if (is_covered) | |
722 | break; | |
723 | } | |
724 | up_read(&namespace_sem); | |
725 | out: | |
726 | return is_covered; | |
727 | } | |
728 | ||
729 | static struct mountpoint *lookup_mountpoint(struct dentry *dentry) | |
730 | { | |
731 | struct hlist_head *chain = mp_hash(dentry); | |
732 | struct mountpoint *mp; | |
733 | ||
734 | hlist_for_each_entry(mp, chain, m_hash) { | |
735 | if (mp->m_dentry == dentry) { | |
736 | /* might be worth a WARN_ON() */ | |
737 | if (d_unlinked(dentry)) | |
738 | return ERR_PTR(-ENOENT); | |
739 | mp->m_count++; | |
740 | return mp; | |
741 | } | |
742 | } | |
743 | return NULL; | |
744 | } | |
745 | ||
746 | static struct mountpoint *new_mountpoint(struct dentry *dentry) | |
747 | { | |
748 | struct hlist_head *chain = mp_hash(dentry); | |
749 | struct mountpoint *mp; | |
750 | int ret; | |
751 | ||
752 | mp = kmalloc(sizeof(struct mountpoint), GFP_KERNEL); | |
753 | if (!mp) | |
754 | return ERR_PTR(-ENOMEM); | |
755 | ||
756 | ret = d_set_mounted(dentry); | |
757 | if (ret) { | |
758 | kfree(mp); | |
759 | return ERR_PTR(ret); | |
760 | } | |
761 | ||
762 | mp->m_dentry = dentry; | |
763 | mp->m_count = 1; | |
764 | hlist_add_head(&mp->m_hash, chain); | |
765 | INIT_HLIST_HEAD(&mp->m_list); | |
766 | return mp; | |
767 | } | |
768 | ||
769 | static void put_mountpoint(struct mountpoint *mp) | |
770 | { | |
771 | if (!--mp->m_count) { | |
772 | struct dentry *dentry = mp->m_dentry; | |
773 | BUG_ON(!hlist_empty(&mp->m_list)); | |
774 | spin_lock(&dentry->d_lock); | |
775 | dentry->d_flags &= ~DCACHE_MOUNTED; | |
776 | spin_unlock(&dentry->d_lock); | |
777 | hlist_del(&mp->m_hash); | |
778 | kfree(mp); | |
779 | } | |
780 | } | |
781 | ||
782 | static inline int check_mnt(struct mount *mnt) | |
783 | { | |
784 | return mnt->mnt_ns == current->nsproxy->mnt_ns; | |
785 | } | |
786 | ||
787 | /* | |
788 | * vfsmount lock must be held for write | |
789 | */ | |
790 | static void touch_mnt_namespace(struct mnt_namespace *ns) | |
791 | { | |
792 | if (ns) { | |
793 | ns->event = ++event; | |
794 | wake_up_interruptible(&ns->poll); | |
795 | } | |
796 | } | |
797 | ||
798 | /* | |
799 | * vfsmount lock must be held for write | |
800 | */ | |
801 | static void __touch_mnt_namespace(struct mnt_namespace *ns) | |
802 | { | |
803 | if (ns && ns->event != event) { | |
804 | ns->event = event; | |
805 | wake_up_interruptible(&ns->poll); | |
806 | } | |
807 | } | |
808 | ||
809 | /* | |
810 | * vfsmount lock must be held for write | |
811 | */ | |
812 | static void unhash_mnt(struct mount *mnt) | |
813 | { | |
814 | mnt->mnt_parent = mnt; | |
815 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; | |
816 | list_del_init(&mnt->mnt_child); | |
817 | hlist_del_init_rcu(&mnt->mnt_hash); | |
818 | hlist_del_init(&mnt->mnt_mp_list); | |
819 | put_mountpoint(mnt->mnt_mp); | |
820 | mnt->mnt_mp = NULL; | |
821 | } | |
822 | ||
823 | /* | |
824 | * vfsmount lock must be held for write | |
825 | */ | |
826 | static void detach_mnt(struct mount *mnt, struct path *old_path) | |
827 | { | |
828 | old_path->dentry = mnt->mnt_mountpoint; | |
829 | old_path->mnt = &mnt->mnt_parent->mnt; | |
830 | unhash_mnt(mnt); | |
831 | } | |
832 | ||
833 | /* | |
834 | * vfsmount lock must be held for write | |
835 | */ | |
836 | static void umount_mnt(struct mount *mnt) | |
837 | { | |
838 | /* old mountpoint will be dropped when we can do that */ | |
839 | mnt->mnt_ex_mountpoint = mnt->mnt_mountpoint; | |
840 | unhash_mnt(mnt); | |
841 | } | |
842 | ||
843 | /* | |
844 | * vfsmount lock must be held for write | |
845 | */ | |
846 | void mnt_set_mountpoint(struct mount *mnt, | |
847 | struct mountpoint *mp, | |
848 | struct mount *child_mnt) | |
849 | { | |
850 | mp->m_count++; | |
851 | mnt_add_count(mnt, 1); /* essentially, that's mntget */ | |
852 | child_mnt->mnt_mountpoint = dget(mp->m_dentry); | |
853 | child_mnt->mnt_parent = mnt; | |
854 | child_mnt->mnt_mp = mp; | |
855 | hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list); | |
856 | } | |
857 | ||
858 | /* | |
859 | * vfsmount lock must be held for write | |
860 | */ | |
861 | static void attach_mnt(struct mount *mnt, | |
862 | struct mount *parent, | |
863 | struct mountpoint *mp) | |
864 | { | |
865 | mnt_set_mountpoint(parent, mp, mnt); | |
866 | hlist_add_head_rcu(&mnt->mnt_hash, m_hash(&parent->mnt, mp->m_dentry)); | |
867 | list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); | |
868 | } | |
869 | ||
870 | static void attach_shadowed(struct mount *mnt, | |
871 | struct mount *parent, | |
872 | struct mount *shadows) | |
873 | { | |
874 | if (shadows) { | |
875 | hlist_add_behind_rcu(&mnt->mnt_hash, &shadows->mnt_hash); | |
876 | list_add(&mnt->mnt_child, &shadows->mnt_child); | |
877 | } else { | |
878 | hlist_add_head_rcu(&mnt->mnt_hash, | |
879 | m_hash(&parent->mnt, mnt->mnt_mountpoint)); | |
880 | list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); | |
881 | } | |
882 | } | |
883 | ||
884 | /* | |
885 | * vfsmount lock must be held for write | |
886 | */ | |
887 | static void commit_tree(struct mount *mnt, struct mount *shadows) | |
888 | { | |
889 | struct mount *parent = mnt->mnt_parent; | |
890 | struct mount *m; | |
891 | LIST_HEAD(head); | |
892 | struct mnt_namespace *n = parent->mnt_ns; | |
893 | ||
894 | BUG_ON(parent == mnt); | |
895 | ||
896 | list_add_tail(&head, &mnt->mnt_list); | |
897 | list_for_each_entry(m, &head, mnt_list) | |
898 | m->mnt_ns = n; | |
899 | ||
900 | list_splice(&head, n->list.prev); | |
901 | ||
902 | attach_shadowed(mnt, parent, shadows); | |
903 | touch_mnt_namespace(n); | |
904 | } | |
905 | ||
906 | static struct mount *next_mnt(struct mount *p, struct mount *root) | |
907 | { | |
908 | struct list_head *next = p->mnt_mounts.next; | |
909 | if (next == &p->mnt_mounts) { | |
910 | while (1) { | |
911 | if (p == root) | |
912 | return NULL; | |
913 | next = p->mnt_child.next; | |
914 | if (next != &p->mnt_parent->mnt_mounts) | |
915 | break; | |
916 | p = p->mnt_parent; | |
917 | } | |
918 | } | |
919 | return list_entry(next, struct mount, mnt_child); | |
920 | } | |
921 | ||
922 | static struct mount *skip_mnt_tree(struct mount *p) | |
923 | { | |
924 | struct list_head *prev = p->mnt_mounts.prev; | |
925 | while (prev != &p->mnt_mounts) { | |
926 | p = list_entry(prev, struct mount, mnt_child); | |
927 | prev = p->mnt_mounts.prev; | |
928 | } | |
929 | return p; | |
930 | } | |
931 | ||
932 | struct vfsmount * | |
933 | vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data) | |
934 | { | |
935 | struct mount *mnt; | |
936 | struct dentry *root; | |
937 | ||
938 | if (!type) | |
939 | return ERR_PTR(-ENODEV); | |
940 | ||
941 | mnt = alloc_vfsmnt(name); | |
942 | if (!mnt) | |
943 | return ERR_PTR(-ENOMEM); | |
944 | ||
945 | if (flags & MS_KERNMOUNT) | |
946 | mnt->mnt.mnt_flags = MNT_INTERNAL; | |
947 | ||
948 | root = mount_fs(type, flags, name, data); | |
949 | if (IS_ERR(root)) { | |
950 | mnt_free_id(mnt); | |
951 | free_vfsmnt(mnt); | |
952 | return ERR_CAST(root); | |
953 | } | |
954 | ||
955 | mnt->mnt.mnt_root = root; | |
956 | mnt->mnt.mnt_sb = root->d_sb; | |
957 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; | |
958 | mnt->mnt_parent = mnt; | |
959 | lock_mount_hash(); | |
960 | list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts); | |
961 | unlock_mount_hash(); | |
962 | return &mnt->mnt; | |
963 | } | |
964 | EXPORT_SYMBOL_GPL(vfs_kern_mount); | |
965 | ||
966 | static struct mount *clone_mnt(struct mount *old, struct dentry *root, | |
967 | int flag) | |
968 | { | |
969 | struct super_block *sb = old->mnt.mnt_sb; | |
970 | struct mount *mnt; | |
971 | int err; | |
972 | ||
973 | mnt = alloc_vfsmnt(old->mnt_devname); | |
974 | if (!mnt) | |
975 | return ERR_PTR(-ENOMEM); | |
976 | ||
977 | if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE)) | |
978 | mnt->mnt_group_id = 0; /* not a peer of original */ | |
979 | else | |
980 | mnt->mnt_group_id = old->mnt_group_id; | |
981 | ||
982 | if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { | |
983 | err = mnt_alloc_group_id(mnt); | |
984 | if (err) | |
985 | goto out_free; | |
986 | } | |
987 | ||
988 | mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~(MNT_WRITE_HOLD|MNT_MARKED); | |
989 | /* Don't allow unprivileged users to change mount flags */ | |
990 | if (flag & CL_UNPRIVILEGED) { | |
991 | mnt->mnt.mnt_flags |= MNT_LOCK_ATIME; | |
992 | ||
993 | if (mnt->mnt.mnt_flags & MNT_READONLY) | |
994 | mnt->mnt.mnt_flags |= MNT_LOCK_READONLY; | |
995 | ||
996 | if (mnt->mnt.mnt_flags & MNT_NODEV) | |
997 | mnt->mnt.mnt_flags |= MNT_LOCK_NODEV; | |
998 | ||
999 | if (mnt->mnt.mnt_flags & MNT_NOSUID) | |
1000 | mnt->mnt.mnt_flags |= MNT_LOCK_NOSUID; | |
1001 | ||
1002 | if (mnt->mnt.mnt_flags & MNT_NOEXEC) | |
1003 | mnt->mnt.mnt_flags |= MNT_LOCK_NOEXEC; | |
1004 | } | |
1005 | ||
1006 | /* Don't allow unprivileged users to reveal what is under a mount */ | |
1007 | if ((flag & CL_UNPRIVILEGED) && | |
1008 | (!(flag & CL_EXPIRE) || list_empty(&old->mnt_expire))) | |
1009 | mnt->mnt.mnt_flags |= MNT_LOCKED; | |
1010 | ||
1011 | atomic_inc(&sb->s_active); | |
1012 | mnt->mnt.mnt_sb = sb; | |
1013 | mnt->mnt.mnt_root = dget(root); | |
1014 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; | |
1015 | mnt->mnt_parent = mnt; | |
1016 | lock_mount_hash(); | |
1017 | list_add_tail(&mnt->mnt_instance, &sb->s_mounts); | |
1018 | unlock_mount_hash(); | |
1019 | ||
1020 | if ((flag & CL_SLAVE) || | |
1021 | ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) { | |
1022 | list_add(&mnt->mnt_slave, &old->mnt_slave_list); | |
1023 | mnt->mnt_master = old; | |
1024 | CLEAR_MNT_SHARED(mnt); | |
1025 | } else if (!(flag & CL_PRIVATE)) { | |
1026 | if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old)) | |
1027 | list_add(&mnt->mnt_share, &old->mnt_share); | |
1028 | if (IS_MNT_SLAVE(old)) | |
1029 | list_add(&mnt->mnt_slave, &old->mnt_slave); | |
1030 | mnt->mnt_master = old->mnt_master; | |
1031 | } | |
1032 | if (flag & CL_MAKE_SHARED) | |
1033 | set_mnt_shared(mnt); | |
1034 | ||
1035 | /* stick the duplicate mount on the same expiry list | |
1036 | * as the original if that was on one */ | |
1037 | if (flag & CL_EXPIRE) { | |
1038 | if (!list_empty(&old->mnt_expire)) | |
1039 | list_add(&mnt->mnt_expire, &old->mnt_expire); | |
1040 | } | |
1041 | ||
1042 | return mnt; | |
1043 | ||
1044 | out_free: | |
1045 | mnt_free_id(mnt); | |
1046 | free_vfsmnt(mnt); | |
1047 | return ERR_PTR(err); | |
1048 | } | |
1049 | ||
1050 | static void cleanup_mnt(struct mount *mnt) | |
1051 | { | |
1052 | /* | |
1053 | * This probably indicates that somebody messed | |
1054 | * up a mnt_want/drop_write() pair. If this | |
1055 | * happens, the filesystem was probably unable | |
1056 | * to make r/w->r/o transitions. | |
1057 | */ | |
1058 | /* | |
1059 | * The locking used to deal with mnt_count decrement provides barriers, | |
1060 | * so mnt_get_writers() below is safe. | |
1061 | */ | |
1062 | WARN_ON(mnt_get_writers(mnt)); | |
1063 | if (unlikely(mnt->mnt_pins.first)) | |
1064 | mnt_pin_kill(mnt); | |
1065 | fsnotify_vfsmount_delete(&mnt->mnt); | |
1066 | dput(mnt->mnt.mnt_root); | |
1067 | deactivate_super(mnt->mnt.mnt_sb); | |
1068 | mnt_free_id(mnt); | |
1069 | call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt); | |
1070 | } | |
1071 | ||
1072 | static void __cleanup_mnt(struct rcu_head *head) | |
1073 | { | |
1074 | cleanup_mnt(container_of(head, struct mount, mnt_rcu)); | |
1075 | } | |
1076 | ||
1077 | static LLIST_HEAD(delayed_mntput_list); | |
1078 | static void delayed_mntput(struct work_struct *unused) | |
1079 | { | |
1080 | struct llist_node *node = llist_del_all(&delayed_mntput_list); | |
1081 | struct llist_node *next; | |
1082 | ||
1083 | for (; node; node = next) { | |
1084 | next = llist_next(node); | |
1085 | cleanup_mnt(llist_entry(node, struct mount, mnt_llist)); | |
1086 | } | |
1087 | } | |
1088 | static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput); | |
1089 | ||
1090 | static void mntput_no_expire(struct mount *mnt) | |
1091 | { | |
1092 | rcu_read_lock(); | |
1093 | mnt_add_count(mnt, -1); | |
1094 | if (likely(mnt->mnt_ns)) { /* shouldn't be the last one */ | |
1095 | rcu_read_unlock(); | |
1096 | return; | |
1097 | } | |
1098 | lock_mount_hash(); | |
1099 | if (mnt_get_count(mnt)) { | |
1100 | rcu_read_unlock(); | |
1101 | unlock_mount_hash(); | |
1102 | return; | |
1103 | } | |
1104 | if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) { | |
1105 | rcu_read_unlock(); | |
1106 | unlock_mount_hash(); | |
1107 | return; | |
1108 | } | |
1109 | mnt->mnt.mnt_flags |= MNT_DOOMED; | |
1110 | rcu_read_unlock(); | |
1111 | ||
1112 | list_del(&mnt->mnt_instance); | |
1113 | ||
1114 | if (unlikely(!list_empty(&mnt->mnt_mounts))) { | |
1115 | struct mount *p, *tmp; | |
1116 | list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) { | |
1117 | umount_mnt(p); | |
1118 | } | |
1119 | } | |
1120 | unlock_mount_hash(); | |
1121 | ||
1122 | if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) { | |
1123 | struct task_struct *task = current; | |
1124 | if (likely(!(task->flags & PF_KTHREAD))) { | |
1125 | init_task_work(&mnt->mnt_rcu, __cleanup_mnt); | |
1126 | if (!task_work_add(task, &mnt->mnt_rcu, true)) | |
1127 | return; | |
1128 | } | |
1129 | if (llist_add(&mnt->mnt_llist, &delayed_mntput_list)) | |
1130 | schedule_delayed_work(&delayed_mntput_work, 1); | |
1131 | return; | |
1132 | } | |
1133 | cleanup_mnt(mnt); | |
1134 | } | |
1135 | ||
1136 | void mntput(struct vfsmount *mnt) | |
1137 | { | |
1138 | if (mnt) { | |
1139 | struct mount *m = real_mount(mnt); | |
1140 | /* avoid cacheline pingpong, hope gcc doesn't get "smart" */ | |
1141 | if (unlikely(m->mnt_expiry_mark)) | |
1142 | m->mnt_expiry_mark = 0; | |
1143 | mntput_no_expire(m); | |
1144 | } | |
1145 | } | |
1146 | EXPORT_SYMBOL(mntput); | |
1147 | ||
1148 | struct vfsmount *mntget(struct vfsmount *mnt) | |
1149 | { | |
1150 | if (mnt) | |
1151 | mnt_add_count(real_mount(mnt), 1); | |
1152 | return mnt; | |
1153 | } | |
1154 | EXPORT_SYMBOL(mntget); | |
1155 | ||
1156 | struct vfsmount *mnt_clone_internal(struct path *path) | |
1157 | { | |
1158 | struct mount *p; | |
1159 | p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE); | |
1160 | if (IS_ERR(p)) | |
1161 | return ERR_CAST(p); | |
1162 | p->mnt.mnt_flags |= MNT_INTERNAL; | |
1163 | return &p->mnt; | |
1164 | } | |
1165 | ||
1166 | static inline void mangle(struct seq_file *m, const char *s) | |
1167 | { | |
1168 | seq_escape(m, s, " \t\n\\"); | |
1169 | } | |
1170 | ||
1171 | /* | |
1172 | * Simple .show_options callback for filesystems which don't want to | |
1173 | * implement more complex mount option showing. | |
1174 | * | |
1175 | * See also save_mount_options(). | |
1176 | */ | |
1177 | int generic_show_options(struct seq_file *m, struct dentry *root) | |
1178 | { | |
1179 | const char *options; | |
1180 | ||
1181 | rcu_read_lock(); | |
1182 | options = rcu_dereference(root->d_sb->s_options); | |
1183 | ||
1184 | if (options != NULL && options[0]) { | |
1185 | seq_putc(m, ','); | |
1186 | mangle(m, options); | |
1187 | } | |
1188 | rcu_read_unlock(); | |
1189 | ||
1190 | return 0; | |
1191 | } | |
1192 | EXPORT_SYMBOL(generic_show_options); | |
1193 | ||
1194 | /* | |
1195 | * If filesystem uses generic_show_options(), this function should be | |
1196 | * called from the fill_super() callback. | |
1197 | * | |
1198 | * The .remount_fs callback usually needs to be handled in a special | |
1199 | * way, to make sure, that previous options are not overwritten if the | |
1200 | * remount fails. | |
1201 | * | |
1202 | * Also note, that if the filesystem's .remount_fs function doesn't | |
1203 | * reset all options to their default value, but changes only newly | |
1204 | * given options, then the displayed options will not reflect reality | |
1205 | * any more. | |
1206 | */ | |
1207 | void save_mount_options(struct super_block *sb, char *options) | |
1208 | { | |
1209 | BUG_ON(sb->s_options); | |
1210 | rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL)); | |
1211 | } | |
1212 | EXPORT_SYMBOL(save_mount_options); | |
1213 | ||
1214 | void replace_mount_options(struct super_block *sb, char *options) | |
1215 | { | |
1216 | char *old = sb->s_options; | |
1217 | rcu_assign_pointer(sb->s_options, options); | |
1218 | if (old) { | |
1219 | synchronize_rcu(); | |
1220 | kfree(old); | |
1221 | } | |
1222 | } | |
1223 | EXPORT_SYMBOL(replace_mount_options); | |
1224 | ||
1225 | #ifdef CONFIG_PROC_FS | |
1226 | /* iterator; we want it to have access to namespace_sem, thus here... */ | |
1227 | static void *m_start(struct seq_file *m, loff_t *pos) | |
1228 | { | |
1229 | struct proc_mounts *p = m->private; | |
1230 | ||
1231 | down_read(&namespace_sem); | |
1232 | if (p->cached_event == p->ns->event) { | |
1233 | void *v = p->cached_mount; | |
1234 | if (*pos == p->cached_index) | |
1235 | return v; | |
1236 | if (*pos == p->cached_index + 1) { | |
1237 | v = seq_list_next(v, &p->ns->list, &p->cached_index); | |
1238 | return p->cached_mount = v; | |
1239 | } | |
1240 | } | |
1241 | ||
1242 | p->cached_event = p->ns->event; | |
1243 | p->cached_mount = seq_list_start(&p->ns->list, *pos); | |
1244 | p->cached_index = *pos; | |
1245 | return p->cached_mount; | |
1246 | } | |
1247 | ||
1248 | static void *m_next(struct seq_file *m, void *v, loff_t *pos) | |
1249 | { | |
1250 | struct proc_mounts *p = m->private; | |
1251 | ||
1252 | p->cached_mount = seq_list_next(v, &p->ns->list, pos); | |
1253 | p->cached_index = *pos; | |
1254 | return p->cached_mount; | |
1255 | } | |
1256 | ||
1257 | static void m_stop(struct seq_file *m, void *v) | |
1258 | { | |
1259 | up_read(&namespace_sem); | |
1260 | } | |
1261 | ||
1262 | static int m_show(struct seq_file *m, void *v) | |
1263 | { | |
1264 | struct proc_mounts *p = m->private; | |
1265 | struct mount *r = list_entry(v, struct mount, mnt_list); | |
1266 | return p->show(m, &r->mnt); | |
1267 | } | |
1268 | ||
1269 | const struct seq_operations mounts_op = { | |
1270 | .start = m_start, | |
1271 | .next = m_next, | |
1272 | .stop = m_stop, | |
1273 | .show = m_show, | |
1274 | }; | |
1275 | #endif /* CONFIG_PROC_FS */ | |
1276 | ||
1277 | /** | |
1278 | * may_umount_tree - check if a mount tree is busy | |
1279 | * @mnt: root of mount tree | |
1280 | * | |
1281 | * This is called to check if a tree of mounts has any | |
1282 | * open files, pwds, chroots or sub mounts that are | |
1283 | * busy. | |
1284 | */ | |
1285 | int may_umount_tree(struct vfsmount *m) | |
1286 | { | |
1287 | struct mount *mnt = real_mount(m); | |
1288 | int actual_refs = 0; | |
1289 | int minimum_refs = 0; | |
1290 | struct mount *p; | |
1291 | BUG_ON(!m); | |
1292 | ||
1293 | /* write lock needed for mnt_get_count */ | |
1294 | lock_mount_hash(); | |
1295 | for (p = mnt; p; p = next_mnt(p, mnt)) { | |
1296 | actual_refs += mnt_get_count(p); | |
1297 | minimum_refs += 2; | |
1298 | } | |
1299 | unlock_mount_hash(); | |
1300 | ||
1301 | if (actual_refs > minimum_refs) | |
1302 | return 0; | |
1303 | ||
1304 | return 1; | |
1305 | } | |
1306 | ||
1307 | EXPORT_SYMBOL(may_umount_tree); | |
1308 | ||
1309 | /** | |
1310 | * may_umount - check if a mount point is busy | |
1311 | * @mnt: root of mount | |
1312 | * | |
1313 | * This is called to check if a mount point has any | |
1314 | * open files, pwds, chroots or sub mounts. If the | |
1315 | * mount has sub mounts this will return busy | |
1316 | * regardless of whether the sub mounts are busy. | |
1317 | * | |
1318 | * Doesn't take quota and stuff into account. IOW, in some cases it will | |
1319 | * give false negatives. The main reason why it's here is that we need | |
1320 | * a non-destructive way to look for easily umountable filesystems. | |
1321 | */ | |
1322 | int may_umount(struct vfsmount *mnt) | |
1323 | { | |
1324 | int ret = 1; | |
1325 | down_read(&namespace_sem); | |
1326 | lock_mount_hash(); | |
1327 | if (propagate_mount_busy(real_mount(mnt), 2)) | |
1328 | ret = 0; | |
1329 | unlock_mount_hash(); | |
1330 | up_read(&namespace_sem); | |
1331 | return ret; | |
1332 | } | |
1333 | ||
1334 | EXPORT_SYMBOL(may_umount); | |
1335 | ||
1336 | static HLIST_HEAD(unmounted); /* protected by namespace_sem */ | |
1337 | ||
1338 | static void namespace_unlock(void) | |
1339 | { | |
1340 | struct hlist_head head; | |
1341 | ||
1342 | hlist_move_list(&unmounted, &head); | |
1343 | ||
1344 | up_write(&namespace_sem); | |
1345 | ||
1346 | if (likely(hlist_empty(&head))) | |
1347 | return; | |
1348 | ||
1349 | synchronize_rcu(); | |
1350 | ||
1351 | group_pin_kill(&head); | |
1352 | } | |
1353 | ||
1354 | static inline void namespace_lock(void) | |
1355 | { | |
1356 | down_write(&namespace_sem); | |
1357 | } | |
1358 | ||
1359 | enum umount_tree_flags { | |
1360 | UMOUNT_SYNC = 1, | |
1361 | UMOUNT_PROPAGATE = 2, | |
1362 | UMOUNT_CONNECTED = 4, | |
1363 | }; | |
1364 | ||
1365 | static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how) | |
1366 | { | |
1367 | /* Leaving mounts connected is only valid for lazy umounts */ | |
1368 | if (how & UMOUNT_SYNC) | |
1369 | return true; | |
1370 | ||
1371 | /* A mount without a parent has nothing to be connected to */ | |
1372 | if (!mnt_has_parent(mnt)) | |
1373 | return true; | |
1374 | ||
1375 | /* Because the reference counting rules change when mounts are | |
1376 | * unmounted and connected, umounted mounts may not be | |
1377 | * connected to mounted mounts. | |
1378 | */ | |
1379 | if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT)) | |
1380 | return true; | |
1381 | ||
1382 | /* Has it been requested that the mount remain connected? */ | |
1383 | if (how & UMOUNT_CONNECTED) | |
1384 | return false; | |
1385 | ||
1386 | /* Is the mount locked such that it needs to remain connected? */ | |
1387 | if (IS_MNT_LOCKED(mnt)) | |
1388 | return false; | |
1389 | ||
1390 | /* By default disconnect the mount */ | |
1391 | return true; | |
1392 | } | |
1393 | ||
1394 | /* | |
1395 | * mount_lock must be held | |
1396 | * namespace_sem must be held for write | |
1397 | */ | |
1398 | static void umount_tree(struct mount *mnt, enum umount_tree_flags how) | |
1399 | { | |
1400 | LIST_HEAD(tmp_list); | |
1401 | struct mount *p; | |
1402 | ||
1403 | if (how & UMOUNT_PROPAGATE) | |
1404 | propagate_mount_unlock(mnt); | |
1405 | ||
1406 | /* Gather the mounts to umount */ | |
1407 | for (p = mnt; p; p = next_mnt(p, mnt)) { | |
1408 | p->mnt.mnt_flags |= MNT_UMOUNT; | |
1409 | list_move(&p->mnt_list, &tmp_list); | |
1410 | } | |
1411 | ||
1412 | /* Hide the mounts from mnt_mounts */ | |
1413 | list_for_each_entry(p, &tmp_list, mnt_list) { | |
1414 | list_del_init(&p->mnt_child); | |
1415 | } | |
1416 | ||
1417 | /* Add propogated mounts to the tmp_list */ | |
1418 | if (how & UMOUNT_PROPAGATE) | |
1419 | propagate_umount(&tmp_list); | |
1420 | ||
1421 | while (!list_empty(&tmp_list)) { | |
1422 | bool disconnect; | |
1423 | p = list_first_entry(&tmp_list, struct mount, mnt_list); | |
1424 | list_del_init(&p->mnt_expire); | |
1425 | list_del_init(&p->mnt_list); | |
1426 | __touch_mnt_namespace(p->mnt_ns); | |
1427 | p->mnt_ns = NULL; | |
1428 | if (how & UMOUNT_SYNC) | |
1429 | p->mnt.mnt_flags |= MNT_SYNC_UMOUNT; | |
1430 | ||
1431 | disconnect = disconnect_mount(p, how); | |
1432 | ||
1433 | pin_insert_group(&p->mnt_umount, &p->mnt_parent->mnt, | |
1434 | disconnect ? &unmounted : NULL); | |
1435 | if (mnt_has_parent(p)) { | |
1436 | mnt_add_count(p->mnt_parent, -1); | |
1437 | if (!disconnect) { | |
1438 | /* Don't forget about p */ | |
1439 | list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts); | |
1440 | } else { | |
1441 | umount_mnt(p); | |
1442 | } | |
1443 | } | |
1444 | change_mnt_propagation(p, MS_PRIVATE); | |
1445 | } | |
1446 | } | |
1447 | ||
1448 | static void shrink_submounts(struct mount *mnt); | |
1449 | ||
1450 | static int do_umount(struct mount *mnt, int flags) | |
1451 | { | |
1452 | struct super_block *sb = mnt->mnt.mnt_sb; | |
1453 | int retval; | |
1454 | ||
1455 | retval = security_sb_umount(&mnt->mnt, flags); | |
1456 | if (retval) | |
1457 | return retval; | |
1458 | ||
1459 | /* | |
1460 | * Allow userspace to request a mountpoint be expired rather than | |
1461 | * unmounting unconditionally. Unmount only happens if: | |
1462 | * (1) the mark is already set (the mark is cleared by mntput()) | |
1463 | * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] | |
1464 | */ | |
1465 | if (flags & MNT_EXPIRE) { | |
1466 | if (&mnt->mnt == current->fs->root.mnt || | |
1467 | flags & (MNT_FORCE | MNT_DETACH)) | |
1468 | return -EINVAL; | |
1469 | ||
1470 | /* | |
1471 | * probably don't strictly need the lock here if we examined | |
1472 | * all race cases, but it's a slowpath. | |
1473 | */ | |
1474 | lock_mount_hash(); | |
1475 | if (mnt_get_count(mnt) != 2) { | |
1476 | unlock_mount_hash(); | |
1477 | return -EBUSY; | |
1478 | } | |
1479 | unlock_mount_hash(); | |
1480 | ||
1481 | if (!xchg(&mnt->mnt_expiry_mark, 1)) | |
1482 | return -EAGAIN; | |
1483 | } | |
1484 | ||
1485 | /* | |
1486 | * If we may have to abort operations to get out of this | |
1487 | * mount, and they will themselves hold resources we must | |
1488 | * allow the fs to do things. In the Unix tradition of | |
1489 | * 'Gee thats tricky lets do it in userspace' the umount_begin | |
1490 | * might fail to complete on the first run through as other tasks | |
1491 | * must return, and the like. Thats for the mount program to worry | |
1492 | * about for the moment. | |
1493 | */ | |
1494 | ||
1495 | if (flags & MNT_FORCE && sb->s_op->umount_begin) { | |
1496 | sb->s_op->umount_begin(sb); | |
1497 | } | |
1498 | ||
1499 | /* | |
1500 | * No sense to grab the lock for this test, but test itself looks | |
1501 | * somewhat bogus. Suggestions for better replacement? | |
1502 | * Ho-hum... In principle, we might treat that as umount + switch | |
1503 | * to rootfs. GC would eventually take care of the old vfsmount. | |
1504 | * Actually it makes sense, especially if rootfs would contain a | |
1505 | * /reboot - static binary that would close all descriptors and | |
1506 | * call reboot(9). Then init(8) could umount root and exec /reboot. | |
1507 | */ | |
1508 | if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { | |
1509 | /* | |
1510 | * Special case for "unmounting" root ... | |
1511 | * we just try to remount it readonly. | |
1512 | */ | |
1513 | if (!capable(CAP_SYS_ADMIN)) | |
1514 | return -EPERM; | |
1515 | down_write(&sb->s_umount); | |
1516 | if (!(sb->s_flags & MS_RDONLY)) | |
1517 | retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); | |
1518 | up_write(&sb->s_umount); | |
1519 | return retval; | |
1520 | } | |
1521 | ||
1522 | namespace_lock(); | |
1523 | lock_mount_hash(); | |
1524 | event++; | |
1525 | ||
1526 | if (flags & MNT_DETACH) { | |
1527 | if (!list_empty(&mnt->mnt_list)) | |
1528 | umount_tree(mnt, UMOUNT_PROPAGATE); | |
1529 | retval = 0; | |
1530 | } else { | |
1531 | shrink_submounts(mnt); | |
1532 | retval = -EBUSY; | |
1533 | if (!propagate_mount_busy(mnt, 2)) { | |
1534 | if (!list_empty(&mnt->mnt_list)) | |
1535 | umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC); | |
1536 | retval = 0; | |
1537 | } | |
1538 | } | |
1539 | unlock_mount_hash(); | |
1540 | namespace_unlock(); | |
1541 | return retval; | |
1542 | } | |
1543 | ||
1544 | /* | |
1545 | * __detach_mounts - lazily unmount all mounts on the specified dentry | |
1546 | * | |
1547 | * During unlink, rmdir, and d_drop it is possible to loose the path | |
1548 | * to an existing mountpoint, and wind up leaking the mount. | |
1549 | * detach_mounts allows lazily unmounting those mounts instead of | |
1550 | * leaking them. | |
1551 | * | |
1552 | * The caller may hold dentry->d_inode->i_mutex. | |
1553 | */ | |
1554 | void __detach_mounts(struct dentry *dentry) | |
1555 | { | |
1556 | struct mountpoint *mp; | |
1557 | struct mount *mnt; | |
1558 | ||
1559 | namespace_lock(); | |
1560 | mp = lookup_mountpoint(dentry); | |
1561 | if (IS_ERR_OR_NULL(mp)) | |
1562 | goto out_unlock; | |
1563 | ||
1564 | lock_mount_hash(); | |
1565 | while (!hlist_empty(&mp->m_list)) { | |
1566 | mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list); | |
1567 | if (mnt->mnt.mnt_flags & MNT_UMOUNT) { | |
1568 | hlist_add_head(&mnt->mnt_umount.s_list, &unmounted); | |
1569 | umount_mnt(mnt); | |
1570 | } | |
1571 | else umount_tree(mnt, UMOUNT_CONNECTED); | |
1572 | } | |
1573 | unlock_mount_hash(); | |
1574 | put_mountpoint(mp); | |
1575 | out_unlock: | |
1576 | namespace_unlock(); | |
1577 | } | |
1578 | ||
1579 | /* | |
1580 | * Is the caller allowed to modify his namespace? | |
1581 | */ | |
1582 | static inline bool may_mount(void) | |
1583 | { | |
1584 | return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN); | |
1585 | } | |
1586 | ||
1587 | static inline bool may_mandlock(void) | |
1588 | { | |
1589 | #ifndef CONFIG_MANDATORY_FILE_LOCKING | |
1590 | return false; | |
1591 | #endif | |
1592 | return capable(CAP_SYS_ADMIN); | |
1593 | } | |
1594 | ||
1595 | /* | |
1596 | * Now umount can handle mount points as well as block devices. | |
1597 | * This is important for filesystems which use unnamed block devices. | |
1598 | * | |
1599 | * We now support a flag for forced unmount like the other 'big iron' | |
1600 | * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD | |
1601 | */ | |
1602 | ||
1603 | SYSCALL_DEFINE2(umount, char __user *, name, int, flags) | |
1604 | { | |
1605 | struct path path; | |
1606 | struct mount *mnt; | |
1607 | int retval; | |
1608 | int lookup_flags = 0; | |
1609 | ||
1610 | if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) | |
1611 | return -EINVAL; | |
1612 | ||
1613 | if (!may_mount()) | |
1614 | return -EPERM; | |
1615 | ||
1616 | if (!(flags & UMOUNT_NOFOLLOW)) | |
1617 | lookup_flags |= LOOKUP_FOLLOW; | |
1618 | ||
1619 | retval = user_path_mountpoint_at(AT_FDCWD, name, lookup_flags, &path); | |
1620 | if (retval) | |
1621 | goto out; | |
1622 | mnt = real_mount(path.mnt); | |
1623 | retval = -EINVAL; | |
1624 | if (path.dentry != path.mnt->mnt_root) | |
1625 | goto dput_and_out; | |
1626 | if (!check_mnt(mnt)) | |
1627 | goto dput_and_out; | |
1628 | if (mnt->mnt.mnt_flags & MNT_LOCKED) | |
1629 | goto dput_and_out; | |
1630 | retval = -EPERM; | |
1631 | if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN)) | |
1632 | goto dput_and_out; | |
1633 | ||
1634 | retval = do_umount(mnt, flags); | |
1635 | dput_and_out: | |
1636 | /* we mustn't call path_put() as that would clear mnt_expiry_mark */ | |
1637 | dput(path.dentry); | |
1638 | mntput_no_expire(mnt); | |
1639 | out: | |
1640 | return retval; | |
1641 | } | |
1642 | ||
1643 | #ifdef __ARCH_WANT_SYS_OLDUMOUNT | |
1644 | ||
1645 | /* | |
1646 | * The 2.0 compatible umount. No flags. | |
1647 | */ | |
1648 | SYSCALL_DEFINE1(oldumount, char __user *, name) | |
1649 | { | |
1650 | return sys_umount(name, 0); | |
1651 | } | |
1652 | ||
1653 | #endif | |
1654 | ||
1655 | static bool is_mnt_ns_file(struct dentry *dentry) | |
1656 | { | |
1657 | /* Is this a proxy for a mount namespace? */ | |
1658 | return dentry->d_op == &ns_dentry_operations && | |
1659 | dentry->d_fsdata == &mntns_operations; | |
1660 | } | |
1661 | ||
1662 | struct mnt_namespace *to_mnt_ns(struct ns_common *ns) | |
1663 | { | |
1664 | return container_of(ns, struct mnt_namespace, ns); | |
1665 | } | |
1666 | ||
1667 | static bool mnt_ns_loop(struct dentry *dentry) | |
1668 | { | |
1669 | /* Could bind mounting the mount namespace inode cause a | |
1670 | * mount namespace loop? | |
1671 | */ | |
1672 | struct mnt_namespace *mnt_ns; | |
1673 | if (!is_mnt_ns_file(dentry)) | |
1674 | return false; | |
1675 | ||
1676 | mnt_ns = to_mnt_ns(get_proc_ns(dentry->d_inode)); | |
1677 | return current->nsproxy->mnt_ns->seq >= mnt_ns->seq; | |
1678 | } | |
1679 | ||
1680 | struct mount *copy_tree(struct mount *mnt, struct dentry *dentry, | |
1681 | int flag) | |
1682 | { | |
1683 | struct mount *res, *p, *q, *r, *parent; | |
1684 | ||
1685 | if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt)) | |
1686 | return ERR_PTR(-EINVAL); | |
1687 | ||
1688 | if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry)) | |
1689 | return ERR_PTR(-EINVAL); | |
1690 | ||
1691 | res = q = clone_mnt(mnt, dentry, flag); | |
1692 | if (IS_ERR(q)) | |
1693 | return q; | |
1694 | ||
1695 | q->mnt_mountpoint = mnt->mnt_mountpoint; | |
1696 | ||
1697 | p = mnt; | |
1698 | list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { | |
1699 | struct mount *s; | |
1700 | if (!is_subdir(r->mnt_mountpoint, dentry)) | |
1701 | continue; | |
1702 | ||
1703 | for (s = r; s; s = next_mnt(s, r)) { | |
1704 | struct mount *t = NULL; | |
1705 | if (!(flag & CL_COPY_UNBINDABLE) && | |
1706 | IS_MNT_UNBINDABLE(s)) { | |
1707 | s = skip_mnt_tree(s); | |
1708 | continue; | |
1709 | } | |
1710 | if (!(flag & CL_COPY_MNT_NS_FILE) && | |
1711 | is_mnt_ns_file(s->mnt.mnt_root)) { | |
1712 | s = skip_mnt_tree(s); | |
1713 | continue; | |
1714 | } | |
1715 | while (p != s->mnt_parent) { | |
1716 | p = p->mnt_parent; | |
1717 | q = q->mnt_parent; | |
1718 | } | |
1719 | p = s; | |
1720 | parent = q; | |
1721 | q = clone_mnt(p, p->mnt.mnt_root, flag); | |
1722 | if (IS_ERR(q)) | |
1723 | goto out; | |
1724 | lock_mount_hash(); | |
1725 | list_add_tail(&q->mnt_list, &res->mnt_list); | |
1726 | mnt_set_mountpoint(parent, p->mnt_mp, q); | |
1727 | if (!list_empty(&parent->mnt_mounts)) { | |
1728 | t = list_last_entry(&parent->mnt_mounts, | |
1729 | struct mount, mnt_child); | |
1730 | if (t->mnt_mp != p->mnt_mp) | |
1731 | t = NULL; | |
1732 | } | |
1733 | attach_shadowed(q, parent, t); | |
1734 | unlock_mount_hash(); | |
1735 | } | |
1736 | } | |
1737 | return res; | |
1738 | out: | |
1739 | if (res) { | |
1740 | lock_mount_hash(); | |
1741 | umount_tree(res, UMOUNT_SYNC); | |
1742 | unlock_mount_hash(); | |
1743 | } | |
1744 | return q; | |
1745 | } | |
1746 | ||
1747 | /* Caller should check returned pointer for errors */ | |
1748 | ||
1749 | struct vfsmount *collect_mounts(struct path *path) | |
1750 | { | |
1751 | struct mount *tree; | |
1752 | namespace_lock(); | |
1753 | if (!check_mnt(real_mount(path->mnt))) | |
1754 | tree = ERR_PTR(-EINVAL); | |
1755 | else | |
1756 | tree = copy_tree(real_mount(path->mnt), path->dentry, | |
1757 | CL_COPY_ALL | CL_PRIVATE); | |
1758 | namespace_unlock(); | |
1759 | if (IS_ERR(tree)) | |
1760 | return ERR_CAST(tree); | |
1761 | return &tree->mnt; | |
1762 | } | |
1763 | ||
1764 | void drop_collected_mounts(struct vfsmount *mnt) | |
1765 | { | |
1766 | namespace_lock(); | |
1767 | lock_mount_hash(); | |
1768 | umount_tree(real_mount(mnt), UMOUNT_SYNC); | |
1769 | unlock_mount_hash(); | |
1770 | namespace_unlock(); | |
1771 | } | |
1772 | ||
1773 | /** | |
1774 | * clone_private_mount - create a private clone of a path | |
1775 | * | |
1776 | * This creates a new vfsmount, which will be the clone of @path. The new will | |
1777 | * not be attached anywhere in the namespace and will be private (i.e. changes | |
1778 | * to the originating mount won't be propagated into this). | |
1779 | * | |
1780 | * Release with mntput(). | |
1781 | */ | |
1782 | struct vfsmount *clone_private_mount(struct path *path) | |
1783 | { | |
1784 | struct mount *old_mnt = real_mount(path->mnt); | |
1785 | struct mount *new_mnt; | |
1786 | ||
1787 | if (IS_MNT_UNBINDABLE(old_mnt)) | |
1788 | return ERR_PTR(-EINVAL); | |
1789 | ||
1790 | down_read(&namespace_sem); | |
1791 | new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE); | |
1792 | up_read(&namespace_sem); | |
1793 | if (IS_ERR(new_mnt)) | |
1794 | return ERR_CAST(new_mnt); | |
1795 | ||
1796 | return &new_mnt->mnt; | |
1797 | } | |
1798 | EXPORT_SYMBOL_GPL(clone_private_mount); | |
1799 | ||
1800 | int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, | |
1801 | struct vfsmount *root) | |
1802 | { | |
1803 | struct mount *mnt; | |
1804 | int res = f(root, arg); | |
1805 | if (res) | |
1806 | return res; | |
1807 | list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) { | |
1808 | res = f(&mnt->mnt, arg); | |
1809 | if (res) | |
1810 | return res; | |
1811 | } | |
1812 | return 0; | |
1813 | } | |
1814 | ||
1815 | static void cleanup_group_ids(struct mount *mnt, struct mount *end) | |
1816 | { | |
1817 | struct mount *p; | |
1818 | ||
1819 | for (p = mnt; p != end; p = next_mnt(p, mnt)) { | |
1820 | if (p->mnt_group_id && !IS_MNT_SHARED(p)) | |
1821 | mnt_release_group_id(p); | |
1822 | } | |
1823 | } | |
1824 | ||
1825 | static int invent_group_ids(struct mount *mnt, bool recurse) | |
1826 | { | |
1827 | struct mount *p; | |
1828 | ||
1829 | for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { | |
1830 | if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { | |
1831 | int err = mnt_alloc_group_id(p); | |
1832 | if (err) { | |
1833 | cleanup_group_ids(mnt, p); | |
1834 | return err; | |
1835 | } | |
1836 | } | |
1837 | } | |
1838 | ||
1839 | return 0; | |
1840 | } | |
1841 | ||
1842 | /* | |
1843 | * @source_mnt : mount tree to be attached | |
1844 | * @nd : place the mount tree @source_mnt is attached | |
1845 | * @parent_nd : if non-null, detach the source_mnt from its parent and | |
1846 | * store the parent mount and mountpoint dentry. | |
1847 | * (done when source_mnt is moved) | |
1848 | * | |
1849 | * NOTE: in the table below explains the semantics when a source mount | |
1850 | * of a given type is attached to a destination mount of a given type. | |
1851 | * --------------------------------------------------------------------------- | |
1852 | * | BIND MOUNT OPERATION | | |
1853 | * |************************************************************************** | |
1854 | * | source-->| shared | private | slave | unbindable | | |
1855 | * | dest | | | | | | |
1856 | * | | | | | | | | |
1857 | * | v | | | | | | |
1858 | * |************************************************************************** | |
1859 | * | shared | shared (++) | shared (+) | shared(+++)| invalid | | |
1860 | * | | | | | | | |
1861 | * |non-shared| shared (+) | private | slave (*) | invalid | | |
1862 | * *************************************************************************** | |
1863 | * A bind operation clones the source mount and mounts the clone on the | |
1864 | * destination mount. | |
1865 | * | |
1866 | * (++) the cloned mount is propagated to all the mounts in the propagation | |
1867 | * tree of the destination mount and the cloned mount is added to | |
1868 | * the peer group of the source mount. | |
1869 | * (+) the cloned mount is created under the destination mount and is marked | |
1870 | * as shared. The cloned mount is added to the peer group of the source | |
1871 | * mount. | |
1872 | * (+++) the mount is propagated to all the mounts in the propagation tree | |
1873 | * of the destination mount and the cloned mount is made slave | |
1874 | * of the same master as that of the source mount. The cloned mount | |
1875 | * is marked as 'shared and slave'. | |
1876 | * (*) the cloned mount is made a slave of the same master as that of the | |
1877 | * source mount. | |
1878 | * | |
1879 | * --------------------------------------------------------------------------- | |
1880 | * | MOVE MOUNT OPERATION | | |
1881 | * |************************************************************************** | |
1882 | * | source-->| shared | private | slave | unbindable | | |
1883 | * | dest | | | | | | |
1884 | * | | | | | | | | |
1885 | * | v | | | | | | |
1886 | * |************************************************************************** | |
1887 | * | shared | shared (+) | shared (+) | shared(+++) | invalid | | |
1888 | * | | | | | | | |
1889 | * |non-shared| shared (+*) | private | slave (*) | unbindable | | |
1890 | * *************************************************************************** | |
1891 | * | |
1892 | * (+) the mount is moved to the destination. And is then propagated to | |
1893 | * all the mounts in the propagation tree of the destination mount. | |
1894 | * (+*) the mount is moved to the destination. | |
1895 | * (+++) the mount is moved to the destination and is then propagated to | |
1896 | * all the mounts belonging to the destination mount's propagation tree. | |
1897 | * the mount is marked as 'shared and slave'. | |
1898 | * (*) the mount continues to be a slave at the new location. | |
1899 | * | |
1900 | * if the source mount is a tree, the operations explained above is | |
1901 | * applied to each mount in the tree. | |
1902 | * Must be called without spinlocks held, since this function can sleep | |
1903 | * in allocations. | |
1904 | */ | |
1905 | static int attach_recursive_mnt(struct mount *source_mnt, | |
1906 | struct mount *dest_mnt, | |
1907 | struct mountpoint *dest_mp, | |
1908 | struct path *parent_path) | |
1909 | { | |
1910 | HLIST_HEAD(tree_list); | |
1911 | struct mount *child, *p; | |
1912 | struct hlist_node *n; | |
1913 | int err; | |
1914 | ||
1915 | if (IS_MNT_SHARED(dest_mnt)) { | |
1916 | err = invent_group_ids(source_mnt, true); | |
1917 | if (err) | |
1918 | goto out; | |
1919 | err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list); | |
1920 | lock_mount_hash(); | |
1921 | if (err) | |
1922 | goto out_cleanup_ids; | |
1923 | for (p = source_mnt; p; p = next_mnt(p, source_mnt)) | |
1924 | set_mnt_shared(p); | |
1925 | } else { | |
1926 | lock_mount_hash(); | |
1927 | } | |
1928 | if (parent_path) { | |
1929 | detach_mnt(source_mnt, parent_path); | |
1930 | attach_mnt(source_mnt, dest_mnt, dest_mp); | |
1931 | touch_mnt_namespace(source_mnt->mnt_ns); | |
1932 | } else { | |
1933 | mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt); | |
1934 | commit_tree(source_mnt, NULL); | |
1935 | } | |
1936 | ||
1937 | hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) { | |
1938 | struct mount *q; | |
1939 | hlist_del_init(&child->mnt_hash); | |
1940 | q = __lookup_mnt_last(&child->mnt_parent->mnt, | |
1941 | child->mnt_mountpoint); | |
1942 | commit_tree(child, q); | |
1943 | } | |
1944 | unlock_mount_hash(); | |
1945 | ||
1946 | return 0; | |
1947 | ||
1948 | out_cleanup_ids: | |
1949 | while (!hlist_empty(&tree_list)) { | |
1950 | child = hlist_entry(tree_list.first, struct mount, mnt_hash); | |
1951 | umount_tree(child, UMOUNT_SYNC); | |
1952 | } | |
1953 | unlock_mount_hash(); | |
1954 | cleanup_group_ids(source_mnt, NULL); | |
1955 | out: | |
1956 | return err; | |
1957 | } | |
1958 | ||
1959 | static struct mountpoint *lock_mount(struct path *path) | |
1960 | { | |
1961 | struct vfsmount *mnt; | |
1962 | struct dentry *dentry = path->dentry; | |
1963 | retry: | |
1964 | inode_lock(dentry->d_inode); | |
1965 | if (unlikely(cant_mount(dentry))) { | |
1966 | inode_unlock(dentry->d_inode); | |
1967 | return ERR_PTR(-ENOENT); | |
1968 | } | |
1969 | namespace_lock(); | |
1970 | mnt = lookup_mnt(path); | |
1971 | if (likely(!mnt)) { | |
1972 | struct mountpoint *mp = lookup_mountpoint(dentry); | |
1973 | if (!mp) | |
1974 | mp = new_mountpoint(dentry); | |
1975 | if (IS_ERR(mp)) { | |
1976 | namespace_unlock(); | |
1977 | inode_unlock(dentry->d_inode); | |
1978 | return mp; | |
1979 | } | |
1980 | return mp; | |
1981 | } | |
1982 | namespace_unlock(); | |
1983 | inode_unlock(path->dentry->d_inode); | |
1984 | path_put(path); | |
1985 | path->mnt = mnt; | |
1986 | dentry = path->dentry = dget(mnt->mnt_root); | |
1987 | goto retry; | |
1988 | } | |
1989 | ||
1990 | static void unlock_mount(struct mountpoint *where) | |
1991 | { | |
1992 | struct dentry *dentry = where->m_dentry; | |
1993 | put_mountpoint(where); | |
1994 | namespace_unlock(); | |
1995 | inode_unlock(dentry->d_inode); | |
1996 | } | |
1997 | ||
1998 | static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp) | |
1999 | { | |
2000 | if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER) | |
2001 | return -EINVAL; | |
2002 | ||
2003 | if (d_is_dir(mp->m_dentry) != | |
2004 | d_is_dir(mnt->mnt.mnt_root)) | |
2005 | return -ENOTDIR; | |
2006 | ||
2007 | return attach_recursive_mnt(mnt, p, mp, NULL); | |
2008 | } | |
2009 | ||
2010 | /* | |
2011 | * Sanity check the flags to change_mnt_propagation. | |
2012 | */ | |
2013 | ||
2014 | static int flags_to_propagation_type(int flags) | |
2015 | { | |
2016 | int type = flags & ~(MS_REC | MS_SILENT); | |
2017 | ||
2018 | /* Fail if any non-propagation flags are set */ | |
2019 | if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) | |
2020 | return 0; | |
2021 | /* Only one propagation flag should be set */ | |
2022 | if (!is_power_of_2(type)) | |
2023 | return 0; | |
2024 | return type; | |
2025 | } | |
2026 | ||
2027 | /* | |
2028 | * recursively change the type of the mountpoint. | |
2029 | */ | |
2030 | static int do_change_type(struct path *path, int flag) | |
2031 | { | |
2032 | struct mount *m; | |
2033 | struct mount *mnt = real_mount(path->mnt); | |
2034 | int recurse = flag & MS_REC; | |
2035 | int type; | |
2036 | int err = 0; | |
2037 | ||
2038 | if (path->dentry != path->mnt->mnt_root) | |
2039 | return -EINVAL; | |
2040 | ||
2041 | type = flags_to_propagation_type(flag); | |
2042 | if (!type) | |
2043 | return -EINVAL; | |
2044 | ||
2045 | namespace_lock(); | |
2046 | if (type == MS_SHARED) { | |
2047 | err = invent_group_ids(mnt, recurse); | |
2048 | if (err) | |
2049 | goto out_unlock; | |
2050 | } | |
2051 | ||
2052 | lock_mount_hash(); | |
2053 | for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) | |
2054 | change_mnt_propagation(m, type); | |
2055 | unlock_mount_hash(); | |
2056 | ||
2057 | out_unlock: | |
2058 | namespace_unlock(); | |
2059 | return err; | |
2060 | } | |
2061 | ||
2062 | static bool has_locked_children(struct mount *mnt, struct dentry *dentry) | |
2063 | { | |
2064 | struct mount *child; | |
2065 | list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { | |
2066 | if (!is_subdir(child->mnt_mountpoint, dentry)) | |
2067 | continue; | |
2068 | ||
2069 | if (child->mnt.mnt_flags & MNT_LOCKED) | |
2070 | return true; | |
2071 | } | |
2072 | return false; | |
2073 | } | |
2074 | ||
2075 | /* | |
2076 | * do loopback mount. | |
2077 | */ | |
2078 | static int do_loopback(struct path *path, const char *old_name, | |
2079 | int recurse) | |
2080 | { | |
2081 | struct path old_path; | |
2082 | struct mount *mnt = NULL, *old, *parent; | |
2083 | struct mountpoint *mp; | |
2084 | int err; | |
2085 | if (!old_name || !*old_name) | |
2086 | return -EINVAL; | |
2087 | err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); | |
2088 | if (err) | |
2089 | return err; | |
2090 | ||
2091 | err = -EINVAL; | |
2092 | if (mnt_ns_loop(old_path.dentry)) | |
2093 | goto out; | |
2094 | ||
2095 | mp = lock_mount(path); | |
2096 | err = PTR_ERR(mp); | |
2097 | if (IS_ERR(mp)) | |
2098 | goto out; | |
2099 | ||
2100 | old = real_mount(old_path.mnt); | |
2101 | parent = real_mount(path->mnt); | |
2102 | ||
2103 | err = -EINVAL; | |
2104 | if (IS_MNT_UNBINDABLE(old)) | |
2105 | goto out2; | |
2106 | ||
2107 | if (!check_mnt(parent)) | |
2108 | goto out2; | |
2109 | ||
2110 | if (!check_mnt(old) && old_path.dentry->d_op != &ns_dentry_operations) | |
2111 | goto out2; | |
2112 | ||
2113 | if (!recurse && has_locked_children(old, old_path.dentry)) | |
2114 | goto out2; | |
2115 | ||
2116 | if (recurse) | |
2117 | mnt = copy_tree(old, old_path.dentry, CL_COPY_MNT_NS_FILE); | |
2118 | else | |
2119 | mnt = clone_mnt(old, old_path.dentry, 0); | |
2120 | ||
2121 | if (IS_ERR(mnt)) { | |
2122 | err = PTR_ERR(mnt); | |
2123 | goto out2; | |
2124 | } | |
2125 | ||
2126 | mnt->mnt.mnt_flags &= ~MNT_LOCKED; | |
2127 | ||
2128 | err = graft_tree(mnt, parent, mp); | |
2129 | if (err) { | |
2130 | lock_mount_hash(); | |
2131 | umount_tree(mnt, UMOUNT_SYNC); | |
2132 | unlock_mount_hash(); | |
2133 | } | |
2134 | out2: | |
2135 | unlock_mount(mp); | |
2136 | out: | |
2137 | path_put(&old_path); | |
2138 | return err; | |
2139 | } | |
2140 | ||
2141 | static int change_mount_flags(struct vfsmount *mnt, int ms_flags) | |
2142 | { | |
2143 | int error = 0; | |
2144 | int readonly_request = 0; | |
2145 | ||
2146 | if (ms_flags & MS_RDONLY) | |
2147 | readonly_request = 1; | |
2148 | if (readonly_request == __mnt_is_readonly(mnt)) | |
2149 | return 0; | |
2150 | ||
2151 | if (readonly_request) | |
2152 | error = mnt_make_readonly(real_mount(mnt)); | |
2153 | else | |
2154 | __mnt_unmake_readonly(real_mount(mnt)); | |
2155 | return error; | |
2156 | } | |
2157 | ||
2158 | /* | |
2159 | * change filesystem flags. dir should be a physical root of filesystem. | |
2160 | * If you've mounted a non-root directory somewhere and want to do remount | |
2161 | * on it - tough luck. | |
2162 | */ | |
2163 | static int do_remount(struct path *path, int flags, int mnt_flags, | |
2164 | void *data) | |
2165 | { | |
2166 | int err; | |
2167 | struct super_block *sb = path->mnt->mnt_sb; | |
2168 | struct mount *mnt = real_mount(path->mnt); | |
2169 | ||
2170 | if (!check_mnt(mnt)) | |
2171 | return -EINVAL; | |
2172 | ||
2173 | if (path->dentry != path->mnt->mnt_root) | |
2174 | return -EINVAL; | |
2175 | ||
2176 | /* Don't allow changing of locked mnt flags. | |
2177 | * | |
2178 | * No locks need to be held here while testing the various | |
2179 | * MNT_LOCK flags because those flags can never be cleared | |
2180 | * once they are set. | |
2181 | */ | |
2182 | if ((mnt->mnt.mnt_flags & MNT_LOCK_READONLY) && | |
2183 | !(mnt_flags & MNT_READONLY)) { | |
2184 | return -EPERM; | |
2185 | } | |
2186 | if ((mnt->mnt.mnt_flags & MNT_LOCK_NODEV) && | |
2187 | !(mnt_flags & MNT_NODEV)) { | |
2188 | /* Was the nodev implicitly added in mount? */ | |
2189 | if ((mnt->mnt_ns->user_ns != &init_user_ns) && | |
2190 | !(sb->s_type->fs_flags & FS_USERNS_DEV_MOUNT)) { | |
2191 | mnt_flags |= MNT_NODEV; | |
2192 | } else { | |
2193 | return -EPERM; | |
2194 | } | |
2195 | } | |
2196 | if ((mnt->mnt.mnt_flags & MNT_LOCK_NOSUID) && | |
2197 | !(mnt_flags & MNT_NOSUID)) { | |
2198 | return -EPERM; | |
2199 | } | |
2200 | if ((mnt->mnt.mnt_flags & MNT_LOCK_NOEXEC) && | |
2201 | !(mnt_flags & MNT_NOEXEC)) { | |
2202 | return -EPERM; | |
2203 | } | |
2204 | if ((mnt->mnt.mnt_flags & MNT_LOCK_ATIME) && | |
2205 | ((mnt->mnt.mnt_flags & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK))) { | |
2206 | return -EPERM; | |
2207 | } | |
2208 | ||
2209 | err = security_sb_remount(sb, data); | |
2210 | if (err) | |
2211 | return err; | |
2212 | ||
2213 | down_write(&sb->s_umount); | |
2214 | if (flags & MS_BIND) | |
2215 | err = change_mount_flags(path->mnt, flags); | |
2216 | else if (!capable(CAP_SYS_ADMIN)) | |
2217 | err = -EPERM; | |
2218 | else | |
2219 | err = do_remount_sb(sb, flags, data, 0); | |
2220 | if (!err) { | |
2221 | lock_mount_hash(); | |
2222 | mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK; | |
2223 | mnt->mnt.mnt_flags = mnt_flags; | |
2224 | touch_mnt_namespace(mnt->mnt_ns); | |
2225 | unlock_mount_hash(); | |
2226 | } | |
2227 | up_write(&sb->s_umount); | |
2228 | return err; | |
2229 | } | |
2230 | ||
2231 | static inline int tree_contains_unbindable(struct mount *mnt) | |
2232 | { | |
2233 | struct mount *p; | |
2234 | for (p = mnt; p; p = next_mnt(p, mnt)) { | |
2235 | if (IS_MNT_UNBINDABLE(p)) | |
2236 | return 1; | |
2237 | } | |
2238 | return 0; | |
2239 | } | |
2240 | ||
2241 | static int do_move_mount(struct path *path, const char *old_name) | |
2242 | { | |
2243 | struct path old_path, parent_path; | |
2244 | struct mount *p; | |
2245 | struct mount *old; | |
2246 | struct mountpoint *mp; | |
2247 | int err; | |
2248 | if (!old_name || !*old_name) | |
2249 | return -EINVAL; | |
2250 | err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); | |
2251 | if (err) | |
2252 | return err; | |
2253 | ||
2254 | mp = lock_mount(path); | |
2255 | err = PTR_ERR(mp); | |
2256 | if (IS_ERR(mp)) | |
2257 | goto out; | |
2258 | ||
2259 | old = real_mount(old_path.mnt); | |
2260 | p = real_mount(path->mnt); | |
2261 | ||
2262 | err = -EINVAL; | |
2263 | if (!check_mnt(p) || !check_mnt(old)) | |
2264 | goto out1; | |
2265 | ||
2266 | if (old->mnt.mnt_flags & MNT_LOCKED) | |
2267 | goto out1; | |
2268 | ||
2269 | err = -EINVAL; | |
2270 | if (old_path.dentry != old_path.mnt->mnt_root) | |
2271 | goto out1; | |
2272 | ||
2273 | if (!mnt_has_parent(old)) | |
2274 | goto out1; | |
2275 | ||
2276 | if (d_is_dir(path->dentry) != | |
2277 | d_is_dir(old_path.dentry)) | |
2278 | goto out1; | |
2279 | /* | |
2280 | * Don't move a mount residing in a shared parent. | |
2281 | */ | |
2282 | if (IS_MNT_SHARED(old->mnt_parent)) | |
2283 | goto out1; | |
2284 | /* | |
2285 | * Don't move a mount tree containing unbindable mounts to a destination | |
2286 | * mount which is shared. | |
2287 | */ | |
2288 | if (IS_MNT_SHARED(p) && tree_contains_unbindable(old)) | |
2289 | goto out1; | |
2290 | err = -ELOOP; | |
2291 | for (; mnt_has_parent(p); p = p->mnt_parent) | |
2292 | if (p == old) | |
2293 | goto out1; | |
2294 | ||
2295 | err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path); | |
2296 | if (err) | |
2297 | goto out1; | |
2298 | ||
2299 | /* if the mount is moved, it should no longer be expire | |
2300 | * automatically */ | |
2301 | list_del_init(&old->mnt_expire); | |
2302 | out1: | |
2303 | unlock_mount(mp); | |
2304 | out: | |
2305 | if (!err) | |
2306 | path_put(&parent_path); | |
2307 | path_put(&old_path); | |
2308 | return err; | |
2309 | } | |
2310 | ||
2311 | static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype) | |
2312 | { | |
2313 | int err; | |
2314 | const char *subtype = strchr(fstype, '.'); | |
2315 | if (subtype) { | |
2316 | subtype++; | |
2317 | err = -EINVAL; | |
2318 | if (!subtype[0]) | |
2319 | goto err; | |
2320 | } else | |
2321 | subtype = ""; | |
2322 | ||
2323 | mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL); | |
2324 | err = -ENOMEM; | |
2325 | if (!mnt->mnt_sb->s_subtype) | |
2326 | goto err; | |
2327 | return mnt; | |
2328 | ||
2329 | err: | |
2330 | mntput(mnt); | |
2331 | return ERR_PTR(err); | |
2332 | } | |
2333 | ||
2334 | /* | |
2335 | * add a mount into a namespace's mount tree | |
2336 | */ | |
2337 | static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags) | |
2338 | { | |
2339 | struct mountpoint *mp; | |
2340 | struct mount *parent; | |
2341 | int err; | |
2342 | ||
2343 | mnt_flags &= ~MNT_INTERNAL_FLAGS; | |
2344 | ||
2345 | mp = lock_mount(path); | |
2346 | if (IS_ERR(mp)) | |
2347 | return PTR_ERR(mp); | |
2348 | ||
2349 | parent = real_mount(path->mnt); | |
2350 | err = -EINVAL; | |
2351 | if (unlikely(!check_mnt(parent))) { | |
2352 | /* that's acceptable only for automounts done in private ns */ | |
2353 | if (!(mnt_flags & MNT_SHRINKABLE)) | |
2354 | goto unlock; | |
2355 | /* ... and for those we'd better have mountpoint still alive */ | |
2356 | if (!parent->mnt_ns) | |
2357 | goto unlock; | |
2358 | } | |
2359 | ||
2360 | /* Refuse the same filesystem on the same mount point */ | |
2361 | err = -EBUSY; | |
2362 | if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && | |
2363 | path->mnt->mnt_root == path->dentry) | |
2364 | goto unlock; | |
2365 | ||
2366 | err = -EINVAL; | |
2367 | if (d_is_symlink(newmnt->mnt.mnt_root)) | |
2368 | goto unlock; | |
2369 | ||
2370 | newmnt->mnt.mnt_flags = mnt_flags; | |
2371 | err = graft_tree(newmnt, parent, mp); | |
2372 | ||
2373 | unlock: | |
2374 | unlock_mount(mp); | |
2375 | return err; | |
2376 | } | |
2377 | ||
2378 | static bool fs_fully_visible(struct file_system_type *fs_type, int *new_mnt_flags); | |
2379 | ||
2380 | /* | |
2381 | * create a new mount for userspace and request it to be added into the | |
2382 | * namespace's tree | |
2383 | */ | |
2384 | static int do_new_mount(struct path *path, const char *fstype, int flags, | |
2385 | int mnt_flags, const char *name, void *data) | |
2386 | { | |
2387 | struct file_system_type *type; | |
2388 | struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; | |
2389 | struct vfsmount *mnt; | |
2390 | int err; | |
2391 | ||
2392 | if (!fstype) | |
2393 | return -EINVAL; | |
2394 | ||
2395 | type = get_fs_type(fstype); | |
2396 | if (!type) | |
2397 | return -ENODEV; | |
2398 | ||
2399 | if (user_ns != &init_user_ns) { | |
2400 | if (!(type->fs_flags & FS_USERNS_MOUNT)) { | |
2401 | put_filesystem(type); | |
2402 | return -EPERM; | |
2403 | } | |
2404 | /* Only in special cases allow devices from mounts | |
2405 | * created outside the initial user namespace. | |
2406 | */ | |
2407 | if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) { | |
2408 | flags |= MS_NODEV; | |
2409 | mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV; | |
2410 | } | |
2411 | if (type->fs_flags & FS_USERNS_VISIBLE) { | |
2412 | if (!fs_fully_visible(type, &mnt_flags)) | |
2413 | return -EPERM; | |
2414 | } | |
2415 | } | |
2416 | ||
2417 | mnt = vfs_kern_mount(type, flags, name, data); | |
2418 | if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && | |
2419 | !mnt->mnt_sb->s_subtype) | |
2420 | mnt = fs_set_subtype(mnt, fstype); | |
2421 | ||
2422 | put_filesystem(type); | |
2423 | if (IS_ERR(mnt)) | |
2424 | return PTR_ERR(mnt); | |
2425 | ||
2426 | err = do_add_mount(real_mount(mnt), path, mnt_flags); | |
2427 | if (err) | |
2428 | mntput(mnt); | |
2429 | return err; | |
2430 | } | |
2431 | ||
2432 | int finish_automount(struct vfsmount *m, struct path *path) | |
2433 | { | |
2434 | struct mount *mnt = real_mount(m); | |
2435 | int err; | |
2436 | /* The new mount record should have at least 2 refs to prevent it being | |
2437 | * expired before we get a chance to add it | |
2438 | */ | |
2439 | BUG_ON(mnt_get_count(mnt) < 2); | |
2440 | ||
2441 | if (m->mnt_sb == path->mnt->mnt_sb && | |
2442 | m->mnt_root == path->dentry) { | |
2443 | err = -ELOOP; | |
2444 | goto fail; | |
2445 | } | |
2446 | ||
2447 | err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE); | |
2448 | if (!err) | |
2449 | return 0; | |
2450 | fail: | |
2451 | /* remove m from any expiration list it may be on */ | |
2452 | if (!list_empty(&mnt->mnt_expire)) { | |
2453 | namespace_lock(); | |
2454 | list_del_init(&mnt->mnt_expire); | |
2455 | namespace_unlock(); | |
2456 | } | |
2457 | mntput(m); | |
2458 | mntput(m); | |
2459 | return err; | |
2460 | } | |
2461 | ||
2462 | /** | |
2463 | * mnt_set_expiry - Put a mount on an expiration list | |
2464 | * @mnt: The mount to list. | |
2465 | * @expiry_list: The list to add the mount to. | |
2466 | */ | |
2467 | void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list) | |
2468 | { | |
2469 | namespace_lock(); | |
2470 | ||
2471 | list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list); | |
2472 | ||
2473 | namespace_unlock(); | |
2474 | } | |
2475 | EXPORT_SYMBOL(mnt_set_expiry); | |
2476 | ||
2477 | /* | |
2478 | * process a list of expirable mountpoints with the intent of discarding any | |
2479 | * mountpoints that aren't in use and haven't been touched since last we came | |
2480 | * here | |
2481 | */ | |
2482 | void mark_mounts_for_expiry(struct list_head *mounts) | |
2483 | { | |
2484 | struct mount *mnt, *next; | |
2485 | LIST_HEAD(graveyard); | |
2486 | ||
2487 | if (list_empty(mounts)) | |
2488 | return; | |
2489 | ||
2490 | namespace_lock(); | |
2491 | lock_mount_hash(); | |
2492 | ||
2493 | /* extract from the expiration list every vfsmount that matches the | |
2494 | * following criteria: | |
2495 | * - only referenced by its parent vfsmount | |
2496 | * - still marked for expiry (marked on the last call here; marks are | |
2497 | * cleared by mntput()) | |
2498 | */ | |
2499 | list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { | |
2500 | if (!xchg(&mnt->mnt_expiry_mark, 1) || | |
2501 | propagate_mount_busy(mnt, 1)) | |
2502 | continue; | |
2503 | list_move(&mnt->mnt_expire, &graveyard); | |
2504 | } | |
2505 | while (!list_empty(&graveyard)) { | |
2506 | mnt = list_first_entry(&graveyard, struct mount, mnt_expire); | |
2507 | touch_mnt_namespace(mnt->mnt_ns); | |
2508 | umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC); | |
2509 | } | |
2510 | unlock_mount_hash(); | |
2511 | namespace_unlock(); | |
2512 | } | |
2513 | ||
2514 | EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); | |
2515 | ||
2516 | /* | |
2517 | * Ripoff of 'select_parent()' | |
2518 | * | |
2519 | * search the list of submounts for a given mountpoint, and move any | |
2520 | * shrinkable submounts to the 'graveyard' list. | |
2521 | */ | |
2522 | static int select_submounts(struct mount *parent, struct list_head *graveyard) | |
2523 | { | |
2524 | struct mount *this_parent = parent; | |
2525 | struct list_head *next; | |
2526 | int found = 0; | |
2527 | ||
2528 | repeat: | |
2529 | next = this_parent->mnt_mounts.next; | |
2530 | resume: | |
2531 | while (next != &this_parent->mnt_mounts) { | |
2532 | struct list_head *tmp = next; | |
2533 | struct mount *mnt = list_entry(tmp, struct mount, mnt_child); | |
2534 | ||
2535 | next = tmp->next; | |
2536 | if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE)) | |
2537 | continue; | |
2538 | /* | |
2539 | * Descend a level if the d_mounts list is non-empty. | |
2540 | */ | |
2541 | if (!list_empty(&mnt->mnt_mounts)) { | |
2542 | this_parent = mnt; | |
2543 | goto repeat; | |
2544 | } | |
2545 | ||
2546 | if (!propagate_mount_busy(mnt, 1)) { | |
2547 | list_move_tail(&mnt->mnt_expire, graveyard); | |
2548 | found++; | |
2549 | } | |
2550 | } | |
2551 | /* | |
2552 | * All done at this level ... ascend and resume the search | |
2553 | */ | |
2554 | if (this_parent != parent) { | |
2555 | next = this_parent->mnt_child.next; | |
2556 | this_parent = this_parent->mnt_parent; | |
2557 | goto resume; | |
2558 | } | |
2559 | return found; | |
2560 | } | |
2561 | ||
2562 | /* | |
2563 | * process a list of expirable mountpoints with the intent of discarding any | |
2564 | * submounts of a specific parent mountpoint | |
2565 | * | |
2566 | * mount_lock must be held for write | |
2567 | */ | |
2568 | static void shrink_submounts(struct mount *mnt) | |
2569 | { | |
2570 | LIST_HEAD(graveyard); | |
2571 | struct mount *m; | |
2572 | ||
2573 | /* extract submounts of 'mountpoint' from the expiration list */ | |
2574 | while (select_submounts(mnt, &graveyard)) { | |
2575 | while (!list_empty(&graveyard)) { | |
2576 | m = list_first_entry(&graveyard, struct mount, | |
2577 | mnt_expire); | |
2578 | touch_mnt_namespace(m->mnt_ns); | |
2579 | umount_tree(m, UMOUNT_PROPAGATE|UMOUNT_SYNC); | |
2580 | } | |
2581 | } | |
2582 | } | |
2583 | ||
2584 | /* | |
2585 | * Some copy_from_user() implementations do not return the exact number of | |
2586 | * bytes remaining to copy on a fault. But copy_mount_options() requires that. | |
2587 | * Note that this function differs from copy_from_user() in that it will oops | |
2588 | * on bad values of `to', rather than returning a short copy. | |
2589 | */ | |
2590 | static long exact_copy_from_user(void *to, const void __user * from, | |
2591 | unsigned long n) | |
2592 | { | |
2593 | char *t = to; | |
2594 | const char __user *f = from; | |
2595 | char c; | |
2596 | ||
2597 | if (!access_ok(VERIFY_READ, from, n)) | |
2598 | return n; | |
2599 | ||
2600 | while (n) { | |
2601 | if (__get_user(c, f)) { | |
2602 | memset(t, 0, n); | |
2603 | break; | |
2604 | } | |
2605 | *t++ = c; | |
2606 | f++; | |
2607 | n--; | |
2608 | } | |
2609 | return n; | |
2610 | } | |
2611 | ||
2612 | void *copy_mount_options(const void __user * data) | |
2613 | { | |
2614 | int i; | |
2615 | unsigned long size; | |
2616 | char *copy; | |
2617 | ||
2618 | if (!data) | |
2619 | return NULL; | |
2620 | ||
2621 | copy = kmalloc(PAGE_SIZE, GFP_KERNEL); | |
2622 | if (!copy) | |
2623 | return ERR_PTR(-ENOMEM); | |
2624 | ||
2625 | /* We only care that *some* data at the address the user | |
2626 | * gave us is valid. Just in case, we'll zero | |
2627 | * the remainder of the page. | |
2628 | */ | |
2629 | /* copy_from_user cannot cross TASK_SIZE ! */ | |
2630 | size = TASK_SIZE - (unsigned long)data; | |
2631 | if (size > PAGE_SIZE) | |
2632 | size = PAGE_SIZE; | |
2633 | ||
2634 | i = size - exact_copy_from_user(copy, data, size); | |
2635 | if (!i) { | |
2636 | kfree(copy); | |
2637 | return ERR_PTR(-EFAULT); | |
2638 | } | |
2639 | if (i != PAGE_SIZE) | |
2640 | memset(copy + i, 0, PAGE_SIZE - i); | |
2641 | return copy; | |
2642 | } | |
2643 | ||
2644 | char *copy_mount_string(const void __user *data) | |
2645 | { | |
2646 | return data ? strndup_user(data, PAGE_SIZE) : NULL; | |
2647 | } | |
2648 | ||
2649 | /* | |
2650 | * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to | |
2651 | * be given to the mount() call (ie: read-only, no-dev, no-suid etc). | |
2652 | * | |
2653 | * data is a (void *) that can point to any structure up to | |
2654 | * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent | |
2655 | * information (or be NULL). | |
2656 | * | |
2657 | * Pre-0.97 versions of mount() didn't have a flags word. | |
2658 | * When the flags word was introduced its top half was required | |
2659 | * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. | |
2660 | * Therefore, if this magic number is present, it carries no information | |
2661 | * and must be discarded. | |
2662 | */ | |
2663 | long do_mount(const char *dev_name, const char __user *dir_name, | |
2664 | const char *type_page, unsigned long flags, void *data_page) | |
2665 | { | |
2666 | struct path path; | |
2667 | int retval = 0; | |
2668 | int mnt_flags = 0; | |
2669 | ||
2670 | /* Discard magic */ | |
2671 | if ((flags & MS_MGC_MSK) == MS_MGC_VAL) | |
2672 | flags &= ~MS_MGC_MSK; | |
2673 | ||
2674 | /* Basic sanity checks */ | |
2675 | if (data_page) | |
2676 | ((char *)data_page)[PAGE_SIZE - 1] = 0; | |
2677 | ||
2678 | /* ... and get the mountpoint */ | |
2679 | retval = user_path(dir_name, &path); | |
2680 | if (retval) | |
2681 | return retval; | |
2682 | ||
2683 | retval = security_sb_mount(dev_name, &path, | |
2684 | type_page, flags, data_page); | |
2685 | if (!retval && !may_mount()) | |
2686 | retval = -EPERM; | |
2687 | if (!retval && (flags & MS_MANDLOCK) && !may_mandlock()) | |
2688 | retval = -EPERM; | |
2689 | if (retval) | |
2690 | goto dput_out; | |
2691 | ||
2692 | /* Default to relatime unless overriden */ | |
2693 | if (!(flags & MS_NOATIME)) | |
2694 | mnt_flags |= MNT_RELATIME; | |
2695 | ||
2696 | /* Separate the per-mountpoint flags */ | |
2697 | if (flags & MS_NOSUID) | |
2698 | mnt_flags |= MNT_NOSUID; | |
2699 | if (flags & MS_NODEV) | |
2700 | mnt_flags |= MNT_NODEV; | |
2701 | if (flags & MS_NOEXEC) | |
2702 | mnt_flags |= MNT_NOEXEC; | |
2703 | if (flags & MS_NOATIME) | |
2704 | mnt_flags |= MNT_NOATIME; | |
2705 | if (flags & MS_NODIRATIME) | |
2706 | mnt_flags |= MNT_NODIRATIME; | |
2707 | if (flags & MS_STRICTATIME) | |
2708 | mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); | |
2709 | if (flags & MS_RDONLY) | |
2710 | mnt_flags |= MNT_READONLY; | |
2711 | ||
2712 | /* The default atime for remount is preservation */ | |
2713 | if ((flags & MS_REMOUNT) && | |
2714 | ((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME | | |
2715 | MS_STRICTATIME)) == 0)) { | |
2716 | mnt_flags &= ~MNT_ATIME_MASK; | |
2717 | mnt_flags |= path.mnt->mnt_flags & MNT_ATIME_MASK; | |
2718 | } | |
2719 | ||
2720 | flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN | | |
2721 | MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT | | |
2722 | MS_STRICTATIME); | |
2723 | ||
2724 | if (flags & MS_REMOUNT) | |
2725 | retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags, | |
2726 | data_page); | |
2727 | else if (flags & MS_BIND) | |
2728 | retval = do_loopback(&path, dev_name, flags & MS_REC); | |
2729 | else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) | |
2730 | retval = do_change_type(&path, flags); | |
2731 | else if (flags & MS_MOVE) | |
2732 | retval = do_move_mount(&path, dev_name); | |
2733 | else | |
2734 | retval = do_new_mount(&path, type_page, flags, mnt_flags, | |
2735 | dev_name, data_page); | |
2736 | dput_out: | |
2737 | path_put(&path); | |
2738 | return retval; | |
2739 | } | |
2740 | ||
2741 | static void free_mnt_ns(struct mnt_namespace *ns) | |
2742 | { | |
2743 | ns_free_inum(&ns->ns); | |
2744 | put_user_ns(ns->user_ns); | |
2745 | kfree(ns); | |
2746 | } | |
2747 | ||
2748 | /* | |
2749 | * Assign a sequence number so we can detect when we attempt to bind | |
2750 | * mount a reference to an older mount namespace into the current | |
2751 | * mount namespace, preventing reference counting loops. A 64bit | |
2752 | * number incrementing at 10Ghz will take 12,427 years to wrap which | |
2753 | * is effectively never, so we can ignore the possibility. | |
2754 | */ | |
2755 | static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1); | |
2756 | ||
2757 | static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns) | |
2758 | { | |
2759 | struct mnt_namespace *new_ns; | |
2760 | int ret; | |
2761 | ||
2762 | new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); | |
2763 | if (!new_ns) | |
2764 | return ERR_PTR(-ENOMEM); | |
2765 | ret = ns_alloc_inum(&new_ns->ns); | |
2766 | if (ret) { | |
2767 | kfree(new_ns); | |
2768 | return ERR_PTR(ret); | |
2769 | } | |
2770 | new_ns->ns.ops = &mntns_operations; | |
2771 | new_ns->seq = atomic64_add_return(1, &mnt_ns_seq); | |
2772 | atomic_set(&new_ns->count, 1); | |
2773 | new_ns->root = NULL; | |
2774 | INIT_LIST_HEAD(&new_ns->list); | |
2775 | init_waitqueue_head(&new_ns->poll); | |
2776 | new_ns->event = 0; | |
2777 | new_ns->user_ns = get_user_ns(user_ns); | |
2778 | return new_ns; | |
2779 | } | |
2780 | ||
2781 | struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, | |
2782 | struct user_namespace *user_ns, struct fs_struct *new_fs) | |
2783 | { | |
2784 | struct mnt_namespace *new_ns; | |
2785 | struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; | |
2786 | struct mount *p, *q; | |
2787 | struct mount *old; | |
2788 | struct mount *new; | |
2789 | int copy_flags; | |
2790 | ||
2791 | BUG_ON(!ns); | |
2792 | ||
2793 | if (likely(!(flags & CLONE_NEWNS))) { | |
2794 | get_mnt_ns(ns); | |
2795 | return ns; | |
2796 | } | |
2797 | ||
2798 | old = ns->root; | |
2799 | ||
2800 | new_ns = alloc_mnt_ns(user_ns); | |
2801 | if (IS_ERR(new_ns)) | |
2802 | return new_ns; | |
2803 | ||
2804 | namespace_lock(); | |
2805 | /* First pass: copy the tree topology */ | |
2806 | copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE; | |
2807 | if (user_ns != ns->user_ns) | |
2808 | copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED; | |
2809 | new = copy_tree(old, old->mnt.mnt_root, copy_flags); | |
2810 | if (IS_ERR(new)) { | |
2811 | namespace_unlock(); | |
2812 | free_mnt_ns(new_ns); | |
2813 | return ERR_CAST(new); | |
2814 | } | |
2815 | new_ns->root = new; | |
2816 | list_add_tail(&new_ns->list, &new->mnt_list); | |
2817 | ||
2818 | /* | |
2819 | * Second pass: switch the tsk->fs->* elements and mark new vfsmounts | |
2820 | * as belonging to new namespace. We have already acquired a private | |
2821 | * fs_struct, so tsk->fs->lock is not needed. | |
2822 | */ | |
2823 | p = old; | |
2824 | q = new; | |
2825 | while (p) { | |
2826 | q->mnt_ns = new_ns; | |
2827 | if (new_fs) { | |
2828 | if (&p->mnt == new_fs->root.mnt) { | |
2829 | new_fs->root.mnt = mntget(&q->mnt); | |
2830 | rootmnt = &p->mnt; | |
2831 | } | |
2832 | if (&p->mnt == new_fs->pwd.mnt) { | |
2833 | new_fs->pwd.mnt = mntget(&q->mnt); | |
2834 | pwdmnt = &p->mnt; | |
2835 | } | |
2836 | } | |
2837 | p = next_mnt(p, old); | |
2838 | q = next_mnt(q, new); | |
2839 | if (!q) | |
2840 | break; | |
2841 | while (p->mnt.mnt_root != q->mnt.mnt_root) | |
2842 | p = next_mnt(p, old); | |
2843 | } | |
2844 | namespace_unlock(); | |
2845 | ||
2846 | if (rootmnt) | |
2847 | mntput(rootmnt); | |
2848 | if (pwdmnt) | |
2849 | mntput(pwdmnt); | |
2850 | ||
2851 | return new_ns; | |
2852 | } | |
2853 | ||
2854 | /** | |
2855 | * create_mnt_ns - creates a private namespace and adds a root filesystem | |
2856 | * @mnt: pointer to the new root filesystem mountpoint | |
2857 | */ | |
2858 | static struct mnt_namespace *create_mnt_ns(struct vfsmount *m) | |
2859 | { | |
2860 | struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns); | |
2861 | if (!IS_ERR(new_ns)) { | |
2862 | struct mount *mnt = real_mount(m); | |
2863 | mnt->mnt_ns = new_ns; | |
2864 | new_ns->root = mnt; | |
2865 | list_add(&mnt->mnt_list, &new_ns->list); | |
2866 | } else { | |
2867 | mntput(m); | |
2868 | } | |
2869 | return new_ns; | |
2870 | } | |
2871 | ||
2872 | struct dentry *mount_subtree(struct vfsmount *mnt, const char *name) | |
2873 | { | |
2874 | struct mnt_namespace *ns; | |
2875 | struct super_block *s; | |
2876 | struct path path; | |
2877 | int err; | |
2878 | ||
2879 | ns = create_mnt_ns(mnt); | |
2880 | if (IS_ERR(ns)) | |
2881 | return ERR_CAST(ns); | |
2882 | ||
2883 | err = vfs_path_lookup(mnt->mnt_root, mnt, | |
2884 | name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); | |
2885 | ||
2886 | put_mnt_ns(ns); | |
2887 | ||
2888 | if (err) | |
2889 | return ERR_PTR(err); | |
2890 | ||
2891 | /* trade a vfsmount reference for active sb one */ | |
2892 | s = path.mnt->mnt_sb; | |
2893 | atomic_inc(&s->s_active); | |
2894 | mntput(path.mnt); | |
2895 | /* lock the sucker */ | |
2896 | down_write(&s->s_umount); | |
2897 | /* ... and return the root of (sub)tree on it */ | |
2898 | return path.dentry; | |
2899 | } | |
2900 | EXPORT_SYMBOL(mount_subtree); | |
2901 | ||
2902 | SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, | |
2903 | char __user *, type, unsigned long, flags, void __user *, data) | |
2904 | { | |
2905 | int ret; | |
2906 | char *kernel_type; | |
2907 | char *kernel_dev; | |
2908 | void *options; | |
2909 | ||
2910 | kernel_type = copy_mount_string(type); | |
2911 | ret = PTR_ERR(kernel_type); | |
2912 | if (IS_ERR(kernel_type)) | |
2913 | goto out_type; | |
2914 | ||
2915 | kernel_dev = copy_mount_string(dev_name); | |
2916 | ret = PTR_ERR(kernel_dev); | |
2917 | if (IS_ERR(kernel_dev)) | |
2918 | goto out_dev; | |
2919 | ||
2920 | options = copy_mount_options(data); | |
2921 | ret = PTR_ERR(options); | |
2922 | if (IS_ERR(options)) | |
2923 | goto out_data; | |
2924 | ||
2925 | ret = do_mount(kernel_dev, dir_name, kernel_type, flags, options); | |
2926 | ||
2927 | kfree(options); | |
2928 | out_data: | |
2929 | kfree(kernel_dev); | |
2930 | out_dev: | |
2931 | kfree(kernel_type); | |
2932 | out_type: | |
2933 | return ret; | |
2934 | } | |
2935 | ||
2936 | /* | |
2937 | * Return true if path is reachable from root | |
2938 | * | |
2939 | * namespace_sem or mount_lock is held | |
2940 | */ | |
2941 | bool is_path_reachable(struct mount *mnt, struct dentry *dentry, | |
2942 | const struct path *root) | |
2943 | { | |
2944 | while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) { | |
2945 | dentry = mnt->mnt_mountpoint; | |
2946 | mnt = mnt->mnt_parent; | |
2947 | } | |
2948 | return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry); | |
2949 | } | |
2950 | ||
2951 | bool path_is_under(struct path *path1, struct path *path2) | |
2952 | { | |
2953 | bool res; | |
2954 | read_seqlock_excl(&mount_lock); | |
2955 | res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2); | |
2956 | read_sequnlock_excl(&mount_lock); | |
2957 | return res; | |
2958 | } | |
2959 | EXPORT_SYMBOL(path_is_under); | |
2960 | ||
2961 | /* | |
2962 | * pivot_root Semantics: | |
2963 | * Moves the root file system of the current process to the directory put_old, | |
2964 | * makes new_root as the new root file system of the current process, and sets | |
2965 | * root/cwd of all processes which had them on the current root to new_root. | |
2966 | * | |
2967 | * Restrictions: | |
2968 | * The new_root and put_old must be directories, and must not be on the | |
2969 | * same file system as the current process root. The put_old must be | |
2970 | * underneath new_root, i.e. adding a non-zero number of /.. to the string | |
2971 | * pointed to by put_old must yield the same directory as new_root. No other | |
2972 | * file system may be mounted on put_old. After all, new_root is a mountpoint. | |
2973 | * | |
2974 | * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. | |
2975 | * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives | |
2976 | * in this situation. | |
2977 | * | |
2978 | * Notes: | |
2979 | * - we don't move root/cwd if they are not at the root (reason: if something | |
2980 | * cared enough to change them, it's probably wrong to force them elsewhere) | |
2981 | * - it's okay to pick a root that isn't the root of a file system, e.g. | |
2982 | * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, | |
2983 | * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root | |
2984 | * first. | |
2985 | */ | |
2986 | SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, | |
2987 | const char __user *, put_old) | |
2988 | { | |
2989 | struct path new, old, parent_path, root_parent, root; | |
2990 | struct mount *new_mnt, *root_mnt, *old_mnt; | |
2991 | struct mountpoint *old_mp, *root_mp; | |
2992 | int error; | |
2993 | ||
2994 | if (!may_mount()) | |
2995 | return -EPERM; | |
2996 | ||
2997 | error = user_path_dir(new_root, &new); | |
2998 | if (error) | |
2999 | goto out0; | |
3000 | ||
3001 | error = user_path_dir(put_old, &old); | |
3002 | if (error) | |
3003 | goto out1; | |
3004 | ||
3005 | error = security_sb_pivotroot(&old, &new); | |
3006 | if (error) | |
3007 | goto out2; | |
3008 | ||
3009 | get_fs_root(current->fs, &root); | |
3010 | old_mp = lock_mount(&old); | |
3011 | error = PTR_ERR(old_mp); | |
3012 | if (IS_ERR(old_mp)) | |
3013 | goto out3; | |
3014 | ||
3015 | error = -EINVAL; | |
3016 | new_mnt = real_mount(new.mnt); | |
3017 | root_mnt = real_mount(root.mnt); | |
3018 | old_mnt = real_mount(old.mnt); | |
3019 | if (IS_MNT_SHARED(old_mnt) || | |
3020 | IS_MNT_SHARED(new_mnt->mnt_parent) || | |
3021 | IS_MNT_SHARED(root_mnt->mnt_parent)) | |
3022 | goto out4; | |
3023 | if (!check_mnt(root_mnt) || !check_mnt(new_mnt)) | |
3024 | goto out4; | |
3025 | if (new_mnt->mnt.mnt_flags & MNT_LOCKED) | |
3026 | goto out4; | |
3027 | error = -ENOENT; | |
3028 | if (d_unlinked(new.dentry)) | |
3029 | goto out4; | |
3030 | error = -EBUSY; | |
3031 | if (new_mnt == root_mnt || old_mnt == root_mnt) | |
3032 | goto out4; /* loop, on the same file system */ | |
3033 | error = -EINVAL; | |
3034 | if (root.mnt->mnt_root != root.dentry) | |
3035 | goto out4; /* not a mountpoint */ | |
3036 | if (!mnt_has_parent(root_mnt)) | |
3037 | goto out4; /* not attached */ | |
3038 | root_mp = root_mnt->mnt_mp; | |
3039 | if (new.mnt->mnt_root != new.dentry) | |
3040 | goto out4; /* not a mountpoint */ | |
3041 | if (!mnt_has_parent(new_mnt)) | |
3042 | goto out4; /* not attached */ | |
3043 | /* make sure we can reach put_old from new_root */ | |
3044 | if (!is_path_reachable(old_mnt, old.dentry, &new)) | |
3045 | goto out4; | |
3046 | /* make certain new is below the root */ | |
3047 | if (!is_path_reachable(new_mnt, new.dentry, &root)) | |
3048 | goto out4; | |
3049 | root_mp->m_count++; /* pin it so it won't go away */ | |
3050 | lock_mount_hash(); | |
3051 | detach_mnt(new_mnt, &parent_path); | |
3052 | detach_mnt(root_mnt, &root_parent); | |
3053 | if (root_mnt->mnt.mnt_flags & MNT_LOCKED) { | |
3054 | new_mnt->mnt.mnt_flags |= MNT_LOCKED; | |
3055 | root_mnt->mnt.mnt_flags &= ~MNT_LOCKED; | |
3056 | } | |
3057 | /* mount old root on put_old */ | |
3058 | attach_mnt(root_mnt, old_mnt, old_mp); | |
3059 | /* mount new_root on / */ | |
3060 | attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp); | |
3061 | touch_mnt_namespace(current->nsproxy->mnt_ns); | |
3062 | /* A moved mount should not expire automatically */ | |
3063 | list_del_init(&new_mnt->mnt_expire); | |
3064 | unlock_mount_hash(); | |
3065 | chroot_fs_refs(&root, &new); | |
3066 | put_mountpoint(root_mp); | |
3067 | error = 0; | |
3068 | out4: | |
3069 | unlock_mount(old_mp); | |
3070 | if (!error) { | |
3071 | path_put(&root_parent); | |
3072 | path_put(&parent_path); | |
3073 | } | |
3074 | out3: | |
3075 | path_put(&root); | |
3076 | out2: | |
3077 | path_put(&old); | |
3078 | out1: | |
3079 | path_put(&new); | |
3080 | out0: | |
3081 | return error; | |
3082 | } | |
3083 | ||
3084 | static void __init init_mount_tree(void) | |
3085 | { | |
3086 | struct vfsmount *mnt; | |
3087 | struct mnt_namespace *ns; | |
3088 | struct path root; | |
3089 | struct file_system_type *type; | |
3090 | ||
3091 | type = get_fs_type("rootfs"); | |
3092 | if (!type) | |
3093 | panic("Can't find rootfs type"); | |
3094 | mnt = vfs_kern_mount(type, 0, "rootfs", NULL); | |
3095 | put_filesystem(type); | |
3096 | if (IS_ERR(mnt)) | |
3097 | panic("Can't create rootfs"); | |
3098 | ||
3099 | ns = create_mnt_ns(mnt); | |
3100 | if (IS_ERR(ns)) | |
3101 | panic("Can't allocate initial namespace"); | |
3102 | ||
3103 | init_task.nsproxy->mnt_ns = ns; | |
3104 | get_mnt_ns(ns); | |
3105 | ||
3106 | root.mnt = mnt; | |
3107 | root.dentry = mnt->mnt_root; | |
3108 | mnt->mnt_flags |= MNT_LOCKED; | |
3109 | ||
3110 | set_fs_pwd(current->fs, &root); | |
3111 | set_fs_root(current->fs, &root); | |
3112 | } | |
3113 | ||
3114 | void __init mnt_init(void) | |
3115 | { | |
3116 | unsigned u; | |
3117 | int err; | |
3118 | ||
3119 | mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount), | |
3120 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); | |
3121 | ||
3122 | mount_hashtable = alloc_large_system_hash("Mount-cache", | |
3123 | sizeof(struct hlist_head), | |
3124 | mhash_entries, 19, | |
3125 | 0, | |
3126 | &m_hash_shift, &m_hash_mask, 0, 0); | |
3127 | mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache", | |
3128 | sizeof(struct hlist_head), | |
3129 | mphash_entries, 19, | |
3130 | 0, | |
3131 | &mp_hash_shift, &mp_hash_mask, 0, 0); | |
3132 | ||
3133 | if (!mount_hashtable || !mountpoint_hashtable) | |
3134 | panic("Failed to allocate mount hash table\n"); | |
3135 | ||
3136 | for (u = 0; u <= m_hash_mask; u++) | |
3137 | INIT_HLIST_HEAD(&mount_hashtable[u]); | |
3138 | for (u = 0; u <= mp_hash_mask; u++) | |
3139 | INIT_HLIST_HEAD(&mountpoint_hashtable[u]); | |
3140 | ||
3141 | kernfs_init(); | |
3142 | ||
3143 | err = sysfs_init(); | |
3144 | if (err) | |
3145 | printk(KERN_WARNING "%s: sysfs_init error: %d\n", | |
3146 | __func__, err); | |
3147 | fs_kobj = kobject_create_and_add("fs", NULL); | |
3148 | if (!fs_kobj) | |
3149 | printk(KERN_WARNING "%s: kobj create error\n", __func__); | |
3150 | init_rootfs(); | |
3151 | init_mount_tree(); | |
3152 | } | |
3153 | ||
3154 | void put_mnt_ns(struct mnt_namespace *ns) | |
3155 | { | |
3156 | if (!atomic_dec_and_test(&ns->count)) | |
3157 | return; | |
3158 | drop_collected_mounts(&ns->root->mnt); | |
3159 | free_mnt_ns(ns); | |
3160 | } | |
3161 | ||
3162 | struct vfsmount *kern_mount_data(struct file_system_type *type, void *data) | |
3163 | { | |
3164 | struct vfsmount *mnt; | |
3165 | mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data); | |
3166 | if (!IS_ERR(mnt)) { | |
3167 | /* | |
3168 | * it is a longterm mount, don't release mnt until | |
3169 | * we unmount before file sys is unregistered | |
3170 | */ | |
3171 | real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL; | |
3172 | } | |
3173 | return mnt; | |
3174 | } | |
3175 | EXPORT_SYMBOL_GPL(kern_mount_data); | |
3176 | ||
3177 | void kern_unmount(struct vfsmount *mnt) | |
3178 | { | |
3179 | /* release long term mount so mount point can be released */ | |
3180 | if (!IS_ERR_OR_NULL(mnt)) { | |
3181 | real_mount(mnt)->mnt_ns = NULL; | |
3182 | synchronize_rcu(); /* yecchhh... */ | |
3183 | mntput(mnt); | |
3184 | } | |
3185 | } | |
3186 | EXPORT_SYMBOL(kern_unmount); | |
3187 | ||
3188 | bool our_mnt(struct vfsmount *mnt) | |
3189 | { | |
3190 | return check_mnt(real_mount(mnt)); | |
3191 | } | |
3192 | ||
3193 | bool current_chrooted(void) | |
3194 | { | |
3195 | /* Does the current process have a non-standard root */ | |
3196 | struct path ns_root; | |
3197 | struct path fs_root; | |
3198 | bool chrooted; | |
3199 | ||
3200 | /* Find the namespace root */ | |
3201 | ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt; | |
3202 | ns_root.dentry = ns_root.mnt->mnt_root; | |
3203 | path_get(&ns_root); | |
3204 | while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root)) | |
3205 | ; | |
3206 | ||
3207 | get_fs_root(current->fs, &fs_root); | |
3208 | ||
3209 | chrooted = !path_equal(&fs_root, &ns_root); | |
3210 | ||
3211 | path_put(&fs_root); | |
3212 | path_put(&ns_root); | |
3213 | ||
3214 | return chrooted; | |
3215 | } | |
3216 | ||
3217 | static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags) | |
3218 | { | |
3219 | struct mnt_namespace *ns = current->nsproxy->mnt_ns; | |
3220 | int new_flags = *new_mnt_flags; | |
3221 | struct mount *mnt; | |
3222 | bool visible = false; | |
3223 | ||
3224 | if (unlikely(!ns)) | |
3225 | return false; | |
3226 | ||
3227 | down_read(&namespace_sem); | |
3228 | list_for_each_entry(mnt, &ns->list, mnt_list) { | |
3229 | struct mount *child; | |
3230 | int mnt_flags; | |
3231 | ||
3232 | if (mnt->mnt.mnt_sb->s_type != type) | |
3233 | continue; | |
3234 | ||
3235 | /* This mount is not fully visible if it's root directory | |
3236 | * is not the root directory of the filesystem. | |
3237 | */ | |
3238 | if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root) | |
3239 | continue; | |
3240 | ||
3241 | /* Read the mount flags and filter out flags that | |
3242 | * may safely be ignored. | |
3243 | */ | |
3244 | mnt_flags = mnt->mnt.mnt_flags; | |
3245 | if (mnt->mnt.mnt_sb->s_iflags & SB_I_NOEXEC) | |
3246 | mnt_flags &= ~(MNT_LOCK_NOSUID | MNT_LOCK_NOEXEC); | |
3247 | ||
3248 | /* Verify the mount flags are equal to or more permissive | |
3249 | * than the proposed new mount. | |
3250 | */ | |
3251 | if ((mnt_flags & MNT_LOCK_READONLY) && | |
3252 | !(new_flags & MNT_READONLY)) | |
3253 | continue; | |
3254 | if ((mnt_flags & MNT_LOCK_NODEV) && | |
3255 | !(new_flags & MNT_NODEV)) | |
3256 | continue; | |
3257 | if ((mnt_flags & MNT_LOCK_NOSUID) && | |
3258 | !(new_flags & MNT_NOSUID)) | |
3259 | continue; | |
3260 | if ((mnt_flags & MNT_LOCK_NOEXEC) && | |
3261 | !(new_flags & MNT_NOEXEC)) | |
3262 | continue; | |
3263 | if ((mnt_flags & MNT_LOCK_ATIME) && | |
3264 | ((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK))) | |
3265 | continue; | |
3266 | ||
3267 | /* This mount is not fully visible if there are any | |
3268 | * locked child mounts that cover anything except for | |
3269 | * empty directories. | |
3270 | */ | |
3271 | list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { | |
3272 | struct inode *inode = child->mnt_mountpoint->d_inode; | |
3273 | /* Only worry about locked mounts */ | |
3274 | if (!(mnt_flags & MNT_LOCKED)) | |
3275 | continue; | |
3276 | /* Is the directory permanetly empty? */ | |
3277 | if (!is_empty_dir_inode(inode)) | |
3278 | goto next; | |
3279 | } | |
3280 | /* Preserve the locked attributes */ | |
3281 | *new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \ | |
3282 | MNT_LOCK_NODEV | \ | |
3283 | MNT_LOCK_NOSUID | \ | |
3284 | MNT_LOCK_NOEXEC | \ | |
3285 | MNT_LOCK_ATIME); | |
3286 | visible = true; | |
3287 | goto found; | |
3288 | next: ; | |
3289 | } | |
3290 | found: | |
3291 | up_read(&namespace_sem); | |
3292 | return visible; | |
3293 | } | |
3294 | ||
3295 | static struct ns_common *mntns_get(struct task_struct *task) | |
3296 | { | |
3297 | struct ns_common *ns = NULL; | |
3298 | struct nsproxy *nsproxy; | |
3299 | ||
3300 | task_lock(task); | |
3301 | nsproxy = task->nsproxy; | |
3302 | if (nsproxy) { | |
3303 | ns = &nsproxy->mnt_ns->ns; | |
3304 | get_mnt_ns(to_mnt_ns(ns)); | |
3305 | } | |
3306 | task_unlock(task); | |
3307 | ||
3308 | return ns; | |
3309 | } | |
3310 | ||
3311 | static void mntns_put(struct ns_common *ns) | |
3312 | { | |
3313 | put_mnt_ns(to_mnt_ns(ns)); | |
3314 | } | |
3315 | ||
3316 | static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns) | |
3317 | { | |
3318 | struct fs_struct *fs = current->fs; | |
3319 | struct mnt_namespace *mnt_ns = to_mnt_ns(ns); | |
3320 | struct path root; | |
3321 | ||
3322 | if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) || | |
3323 | !ns_capable(current_user_ns(), CAP_SYS_CHROOT) || | |
3324 | !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) | |
3325 | return -EPERM; | |
3326 | ||
3327 | if (fs->users != 1) | |
3328 | return -EINVAL; | |
3329 | ||
3330 | get_mnt_ns(mnt_ns); | |
3331 | put_mnt_ns(nsproxy->mnt_ns); | |
3332 | nsproxy->mnt_ns = mnt_ns; | |
3333 | ||
3334 | /* Find the root */ | |
3335 | root.mnt = &mnt_ns->root->mnt; | |
3336 | root.dentry = mnt_ns->root->mnt.mnt_root; | |
3337 | path_get(&root); | |
3338 | while(d_mountpoint(root.dentry) && follow_down_one(&root)) | |
3339 | ; | |
3340 | ||
3341 | /* Update the pwd and root */ | |
3342 | set_fs_pwd(fs, &root); | |
3343 | set_fs_root(fs, &root); | |
3344 | ||
3345 | path_put(&root); | |
3346 | return 0; | |
3347 | } | |
3348 | ||
3349 | const struct proc_ns_operations mntns_operations = { | |
3350 | .name = "mnt", | |
3351 | .type = CLONE_NEWNS, | |
3352 | .get = mntns_get, | |
3353 | .put = mntns_put, | |
3354 | .install = mntns_install, | |
3355 | }; |