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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 | /* | |
1588 | * Now umount can handle mount points as well as block devices. | |
1589 | * This is important for filesystems which use unnamed block devices. | |
1590 | * | |
1591 | * We now support a flag for forced unmount like the other 'big iron' | |
1592 | * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD | |
1593 | */ | |
1594 | ||
1595 | SYSCALL_DEFINE2(umount, char __user *, name, int, flags) | |
1596 | { | |
1597 | struct path path; | |
1598 | struct mount *mnt; | |
1599 | int retval; | |
1600 | int lookup_flags = 0; | |
1601 | ||
1602 | if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) | |
1603 | return -EINVAL; | |
1604 | ||
1605 | if (!may_mount()) | |
1606 | return -EPERM; | |
1607 | ||
1608 | if (!(flags & UMOUNT_NOFOLLOW)) | |
1609 | lookup_flags |= LOOKUP_FOLLOW; | |
1610 | ||
1611 | retval = user_path_mountpoint_at(AT_FDCWD, name, lookup_flags, &path); | |
1612 | if (retval) | |
1613 | goto out; | |
1614 | mnt = real_mount(path.mnt); | |
1615 | retval = -EINVAL; | |
1616 | if (path.dentry != path.mnt->mnt_root) | |
1617 | goto dput_and_out; | |
1618 | if (!check_mnt(mnt)) | |
1619 | goto dput_and_out; | |
1620 | if (mnt->mnt.mnt_flags & MNT_LOCKED) | |
1621 | goto dput_and_out; | |
1622 | retval = -EPERM; | |
1623 | if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN)) | |
1624 | goto dput_and_out; | |
1625 | ||
1626 | retval = do_umount(mnt, flags); | |
1627 | dput_and_out: | |
1628 | /* we mustn't call path_put() as that would clear mnt_expiry_mark */ | |
1629 | dput(path.dentry); | |
1630 | mntput_no_expire(mnt); | |
1631 | out: | |
1632 | return retval; | |
1633 | } | |
1634 | ||
1635 | #ifdef __ARCH_WANT_SYS_OLDUMOUNT | |
1636 | ||
1637 | /* | |
1638 | * The 2.0 compatible umount. No flags. | |
1639 | */ | |
1640 | SYSCALL_DEFINE1(oldumount, char __user *, name) | |
1641 | { | |
1642 | return sys_umount(name, 0); | |
1643 | } | |
1644 | ||
1645 | #endif | |
1646 | ||
1647 | static bool is_mnt_ns_file(struct dentry *dentry) | |
1648 | { | |
1649 | /* Is this a proxy for a mount namespace? */ | |
1650 | return dentry->d_op == &ns_dentry_operations && | |
1651 | dentry->d_fsdata == &mntns_operations; | |
1652 | } | |
1653 | ||
1654 | struct mnt_namespace *to_mnt_ns(struct ns_common *ns) | |
1655 | { | |
1656 | return container_of(ns, struct mnt_namespace, ns); | |
1657 | } | |
1658 | ||
1659 | static bool mnt_ns_loop(struct dentry *dentry) | |
1660 | { | |
1661 | /* Could bind mounting the mount namespace inode cause a | |
1662 | * mount namespace loop? | |
1663 | */ | |
1664 | struct mnt_namespace *mnt_ns; | |
1665 | if (!is_mnt_ns_file(dentry)) | |
1666 | return false; | |
1667 | ||
1668 | mnt_ns = to_mnt_ns(get_proc_ns(dentry->d_inode)); | |
1669 | return current->nsproxy->mnt_ns->seq >= mnt_ns->seq; | |
1670 | } | |
1671 | ||
1672 | struct mount *copy_tree(struct mount *mnt, struct dentry *dentry, | |
1673 | int flag) | |
1674 | { | |
1675 | struct mount *res, *p, *q, *r, *parent; | |
1676 | ||
1677 | if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt)) | |
1678 | return ERR_PTR(-EINVAL); | |
1679 | ||
1680 | if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry)) | |
1681 | return ERR_PTR(-EINVAL); | |
1682 | ||
1683 | res = q = clone_mnt(mnt, dentry, flag); | |
1684 | if (IS_ERR(q)) | |
1685 | return q; | |
1686 | ||
1687 | q->mnt_mountpoint = mnt->mnt_mountpoint; | |
1688 | ||
1689 | p = mnt; | |
1690 | list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { | |
1691 | struct mount *s; | |
1692 | if (!is_subdir(r->mnt_mountpoint, dentry)) | |
1693 | continue; | |
1694 | ||
1695 | for (s = r; s; s = next_mnt(s, r)) { | |
1696 | struct mount *t = NULL; | |
1697 | if (!(flag & CL_COPY_UNBINDABLE) && | |
1698 | IS_MNT_UNBINDABLE(s)) { | |
1699 | s = skip_mnt_tree(s); | |
1700 | continue; | |
1701 | } | |
1702 | if (!(flag & CL_COPY_MNT_NS_FILE) && | |
1703 | is_mnt_ns_file(s->mnt.mnt_root)) { | |
1704 | s = skip_mnt_tree(s); | |
1705 | continue; | |
1706 | } | |
1707 | while (p != s->mnt_parent) { | |
1708 | p = p->mnt_parent; | |
1709 | q = q->mnt_parent; | |
1710 | } | |
1711 | p = s; | |
1712 | parent = q; | |
1713 | q = clone_mnt(p, p->mnt.mnt_root, flag); | |
1714 | if (IS_ERR(q)) | |
1715 | goto out; | |
1716 | lock_mount_hash(); | |
1717 | list_add_tail(&q->mnt_list, &res->mnt_list); | |
1718 | mnt_set_mountpoint(parent, p->mnt_mp, q); | |
1719 | if (!list_empty(&parent->mnt_mounts)) { | |
1720 | t = list_last_entry(&parent->mnt_mounts, | |
1721 | struct mount, mnt_child); | |
1722 | if (t->mnt_mp != p->mnt_mp) | |
1723 | t = NULL; | |
1724 | } | |
1725 | attach_shadowed(q, parent, t); | |
1726 | unlock_mount_hash(); | |
1727 | } | |
1728 | } | |
1729 | return res; | |
1730 | out: | |
1731 | if (res) { | |
1732 | lock_mount_hash(); | |
1733 | umount_tree(res, UMOUNT_SYNC); | |
1734 | unlock_mount_hash(); | |
1735 | } | |
1736 | return q; | |
1737 | } | |
1738 | ||
1739 | /* Caller should check returned pointer for errors */ | |
1740 | ||
1741 | struct vfsmount *collect_mounts(struct path *path) | |
1742 | { | |
1743 | struct mount *tree; | |
1744 | namespace_lock(); | |
1745 | if (!check_mnt(real_mount(path->mnt))) | |
1746 | tree = ERR_PTR(-EINVAL); | |
1747 | else | |
1748 | tree = copy_tree(real_mount(path->mnt), path->dentry, | |
1749 | CL_COPY_ALL | CL_PRIVATE); | |
1750 | namespace_unlock(); | |
1751 | if (IS_ERR(tree)) | |
1752 | return ERR_CAST(tree); | |
1753 | return &tree->mnt; | |
1754 | } | |
1755 | ||
1756 | void drop_collected_mounts(struct vfsmount *mnt) | |
1757 | { | |
1758 | namespace_lock(); | |
1759 | lock_mount_hash(); | |
1760 | umount_tree(real_mount(mnt), UMOUNT_SYNC); | |
1761 | unlock_mount_hash(); | |
1762 | namespace_unlock(); | |
1763 | } | |
1764 | ||
1765 | /** | |
1766 | * clone_private_mount - create a private clone of a path | |
1767 | * | |
1768 | * This creates a new vfsmount, which will be the clone of @path. The new will | |
1769 | * not be attached anywhere in the namespace and will be private (i.e. changes | |
1770 | * to the originating mount won't be propagated into this). | |
1771 | * | |
1772 | * Release with mntput(). | |
1773 | */ | |
1774 | struct vfsmount *clone_private_mount(struct path *path) | |
1775 | { | |
1776 | struct mount *old_mnt = real_mount(path->mnt); | |
1777 | struct mount *new_mnt; | |
1778 | ||
1779 | if (IS_MNT_UNBINDABLE(old_mnt)) | |
1780 | return ERR_PTR(-EINVAL); | |
1781 | ||
1782 | down_read(&namespace_sem); | |
1783 | new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE); | |
1784 | up_read(&namespace_sem); | |
1785 | if (IS_ERR(new_mnt)) | |
1786 | return ERR_CAST(new_mnt); | |
1787 | ||
1788 | return &new_mnt->mnt; | |
1789 | } | |
1790 | EXPORT_SYMBOL_GPL(clone_private_mount); | |
1791 | ||
1792 | int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, | |
1793 | struct vfsmount *root) | |
1794 | { | |
1795 | struct mount *mnt; | |
1796 | int res = f(root, arg); | |
1797 | if (res) | |
1798 | return res; | |
1799 | list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) { | |
1800 | res = f(&mnt->mnt, arg); | |
1801 | if (res) | |
1802 | return res; | |
1803 | } | |
1804 | return 0; | |
1805 | } | |
1806 | ||
1807 | static void cleanup_group_ids(struct mount *mnt, struct mount *end) | |
1808 | { | |
1809 | struct mount *p; | |
1810 | ||
1811 | for (p = mnt; p != end; p = next_mnt(p, mnt)) { | |
1812 | if (p->mnt_group_id && !IS_MNT_SHARED(p)) | |
1813 | mnt_release_group_id(p); | |
1814 | } | |
1815 | } | |
1816 | ||
1817 | static int invent_group_ids(struct mount *mnt, bool recurse) | |
1818 | { | |
1819 | struct mount *p; | |
1820 | ||
1821 | for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { | |
1822 | if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { | |
1823 | int err = mnt_alloc_group_id(p); | |
1824 | if (err) { | |
1825 | cleanup_group_ids(mnt, p); | |
1826 | return err; | |
1827 | } | |
1828 | } | |
1829 | } | |
1830 | ||
1831 | return 0; | |
1832 | } | |
1833 | ||
1834 | /* | |
1835 | * @source_mnt : mount tree to be attached | |
1836 | * @nd : place the mount tree @source_mnt is attached | |
1837 | * @parent_nd : if non-null, detach the source_mnt from its parent and | |
1838 | * store the parent mount and mountpoint dentry. | |
1839 | * (done when source_mnt is moved) | |
1840 | * | |
1841 | * NOTE: in the table below explains the semantics when a source mount | |
1842 | * of a given type is attached to a destination mount of a given type. | |
1843 | * --------------------------------------------------------------------------- | |
1844 | * | BIND MOUNT OPERATION | | |
1845 | * |************************************************************************** | |
1846 | * | source-->| shared | private | slave | unbindable | | |
1847 | * | dest | | | | | | |
1848 | * | | | | | | | | |
1849 | * | v | | | | | | |
1850 | * |************************************************************************** | |
1851 | * | shared | shared (++) | shared (+) | shared(+++)| invalid | | |
1852 | * | | | | | | | |
1853 | * |non-shared| shared (+) | private | slave (*) | invalid | | |
1854 | * *************************************************************************** | |
1855 | * A bind operation clones the source mount and mounts the clone on the | |
1856 | * destination mount. | |
1857 | * | |
1858 | * (++) the cloned mount is propagated to all the mounts in the propagation | |
1859 | * tree of the destination mount and the cloned mount is added to | |
1860 | * the peer group of the source mount. | |
1861 | * (+) the cloned mount is created under the destination mount and is marked | |
1862 | * as shared. The cloned mount is added to the peer group of the source | |
1863 | * mount. | |
1864 | * (+++) the mount is propagated to all the mounts in the propagation tree | |
1865 | * of the destination mount and the cloned mount is made slave | |
1866 | * of the same master as that of the source mount. The cloned mount | |
1867 | * is marked as 'shared and slave'. | |
1868 | * (*) the cloned mount is made a slave of the same master as that of the | |
1869 | * source mount. | |
1870 | * | |
1871 | * --------------------------------------------------------------------------- | |
1872 | * | MOVE MOUNT OPERATION | | |
1873 | * |************************************************************************** | |
1874 | * | source-->| shared | private | slave | unbindable | | |
1875 | * | dest | | | | | | |
1876 | * | | | | | | | | |
1877 | * | v | | | | | | |
1878 | * |************************************************************************** | |
1879 | * | shared | shared (+) | shared (+) | shared(+++) | invalid | | |
1880 | * | | | | | | | |
1881 | * |non-shared| shared (+*) | private | slave (*) | unbindable | | |
1882 | * *************************************************************************** | |
1883 | * | |
1884 | * (+) the mount is moved to the destination. And is then propagated to | |
1885 | * all the mounts in the propagation tree of the destination mount. | |
1886 | * (+*) the mount is moved to the destination. | |
1887 | * (+++) the mount is moved to the destination and is then propagated to | |
1888 | * all the mounts belonging to the destination mount's propagation tree. | |
1889 | * the mount is marked as 'shared and slave'. | |
1890 | * (*) the mount continues to be a slave at the new location. | |
1891 | * | |
1892 | * if the source mount is a tree, the operations explained above is | |
1893 | * applied to each mount in the tree. | |
1894 | * Must be called without spinlocks held, since this function can sleep | |
1895 | * in allocations. | |
1896 | */ | |
1897 | static int attach_recursive_mnt(struct mount *source_mnt, | |
1898 | struct mount *dest_mnt, | |
1899 | struct mountpoint *dest_mp, | |
1900 | struct path *parent_path) | |
1901 | { | |
1902 | HLIST_HEAD(tree_list); | |
1903 | struct mount *child, *p; | |
1904 | struct hlist_node *n; | |
1905 | int err; | |
1906 | ||
1907 | if (IS_MNT_SHARED(dest_mnt)) { | |
1908 | err = invent_group_ids(source_mnt, true); | |
1909 | if (err) | |
1910 | goto out; | |
1911 | err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list); | |
1912 | lock_mount_hash(); | |
1913 | if (err) | |
1914 | goto out_cleanup_ids; | |
1915 | for (p = source_mnt; p; p = next_mnt(p, source_mnt)) | |
1916 | set_mnt_shared(p); | |
1917 | } else { | |
1918 | lock_mount_hash(); | |
1919 | } | |
1920 | if (parent_path) { | |
1921 | detach_mnt(source_mnt, parent_path); | |
1922 | attach_mnt(source_mnt, dest_mnt, dest_mp); | |
1923 | touch_mnt_namespace(source_mnt->mnt_ns); | |
1924 | } else { | |
1925 | mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt); | |
1926 | commit_tree(source_mnt, NULL); | |
1927 | } | |
1928 | ||
1929 | hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) { | |
1930 | struct mount *q; | |
1931 | hlist_del_init(&child->mnt_hash); | |
1932 | q = __lookup_mnt_last(&child->mnt_parent->mnt, | |
1933 | child->mnt_mountpoint); | |
1934 | commit_tree(child, q); | |
1935 | } | |
1936 | unlock_mount_hash(); | |
1937 | ||
1938 | return 0; | |
1939 | ||
1940 | out_cleanup_ids: | |
1941 | while (!hlist_empty(&tree_list)) { | |
1942 | child = hlist_entry(tree_list.first, struct mount, mnt_hash); | |
1943 | umount_tree(child, UMOUNT_SYNC); | |
1944 | } | |
1945 | unlock_mount_hash(); | |
1946 | cleanup_group_ids(source_mnt, NULL); | |
1947 | out: | |
1948 | return err; | |
1949 | } | |
1950 | ||
1951 | static struct mountpoint *lock_mount(struct path *path) | |
1952 | { | |
1953 | struct vfsmount *mnt; | |
1954 | struct dentry *dentry = path->dentry; | |
1955 | retry: | |
1956 | mutex_lock(&dentry->d_inode->i_mutex); | |
1957 | if (unlikely(cant_mount(dentry))) { | |
1958 | mutex_unlock(&dentry->d_inode->i_mutex); | |
1959 | return ERR_PTR(-ENOENT); | |
1960 | } | |
1961 | namespace_lock(); | |
1962 | mnt = lookup_mnt(path); | |
1963 | if (likely(!mnt)) { | |
1964 | struct mountpoint *mp = lookup_mountpoint(dentry); | |
1965 | if (!mp) | |
1966 | mp = new_mountpoint(dentry); | |
1967 | if (IS_ERR(mp)) { | |
1968 | namespace_unlock(); | |
1969 | mutex_unlock(&dentry->d_inode->i_mutex); | |
1970 | return mp; | |
1971 | } | |
1972 | return mp; | |
1973 | } | |
1974 | namespace_unlock(); | |
1975 | mutex_unlock(&path->dentry->d_inode->i_mutex); | |
1976 | path_put(path); | |
1977 | path->mnt = mnt; | |
1978 | dentry = path->dentry = dget(mnt->mnt_root); | |
1979 | goto retry; | |
1980 | } | |
1981 | ||
1982 | static void unlock_mount(struct mountpoint *where) | |
1983 | { | |
1984 | struct dentry *dentry = where->m_dentry; | |
1985 | put_mountpoint(where); | |
1986 | namespace_unlock(); | |
1987 | mutex_unlock(&dentry->d_inode->i_mutex); | |
1988 | } | |
1989 | ||
1990 | static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp) | |
1991 | { | |
1992 | if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER) | |
1993 | return -EINVAL; | |
1994 | ||
1995 | if (d_is_dir(mp->m_dentry) != | |
1996 | d_is_dir(mnt->mnt.mnt_root)) | |
1997 | return -ENOTDIR; | |
1998 | ||
1999 | return attach_recursive_mnt(mnt, p, mp, NULL); | |
2000 | } | |
2001 | ||
2002 | /* | |
2003 | * Sanity check the flags to change_mnt_propagation. | |
2004 | */ | |
2005 | ||
2006 | static int flags_to_propagation_type(int flags) | |
2007 | { | |
2008 | int type = flags & ~(MS_REC | MS_SILENT); | |
2009 | ||
2010 | /* Fail if any non-propagation flags are set */ | |
2011 | if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) | |
2012 | return 0; | |
2013 | /* Only one propagation flag should be set */ | |
2014 | if (!is_power_of_2(type)) | |
2015 | return 0; | |
2016 | return type; | |
2017 | } | |
2018 | ||
2019 | /* | |
2020 | * recursively change the type of the mountpoint. | |
2021 | */ | |
2022 | static int do_change_type(struct path *path, int flag) | |
2023 | { | |
2024 | struct mount *m; | |
2025 | struct mount *mnt = real_mount(path->mnt); | |
2026 | int recurse = flag & MS_REC; | |
2027 | int type; | |
2028 | int err = 0; | |
2029 | ||
2030 | if (path->dentry != path->mnt->mnt_root) | |
2031 | return -EINVAL; | |
2032 | ||
2033 | type = flags_to_propagation_type(flag); | |
2034 | if (!type) | |
2035 | return -EINVAL; | |
2036 | ||
2037 | namespace_lock(); | |
2038 | if (type == MS_SHARED) { | |
2039 | err = invent_group_ids(mnt, recurse); | |
2040 | if (err) | |
2041 | goto out_unlock; | |
2042 | } | |
2043 | ||
2044 | lock_mount_hash(); | |
2045 | for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) | |
2046 | change_mnt_propagation(m, type); | |
2047 | unlock_mount_hash(); | |
2048 | ||
2049 | out_unlock: | |
2050 | namespace_unlock(); | |
2051 | return err; | |
2052 | } | |
2053 | ||
2054 | static bool has_locked_children(struct mount *mnt, struct dentry *dentry) | |
2055 | { | |
2056 | struct mount *child; | |
2057 | list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { | |
2058 | if (!is_subdir(child->mnt_mountpoint, dentry)) | |
2059 | continue; | |
2060 | ||
2061 | if (child->mnt.mnt_flags & MNT_LOCKED) | |
2062 | return true; | |
2063 | } | |
2064 | return false; | |
2065 | } | |
2066 | ||
2067 | /* | |
2068 | * do loopback mount. | |
2069 | */ | |
2070 | static int do_loopback(struct path *path, const char *old_name, | |
2071 | int recurse) | |
2072 | { | |
2073 | struct path old_path; | |
2074 | struct mount *mnt = NULL, *old, *parent; | |
2075 | struct mountpoint *mp; | |
2076 | int err; | |
2077 | if (!old_name || !*old_name) | |
2078 | return -EINVAL; | |
2079 | err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); | |
2080 | if (err) | |
2081 | return err; | |
2082 | ||
2083 | err = -EINVAL; | |
2084 | if (mnt_ns_loop(old_path.dentry)) | |
2085 | goto out; | |
2086 | ||
2087 | mp = lock_mount(path); | |
2088 | err = PTR_ERR(mp); | |
2089 | if (IS_ERR(mp)) | |
2090 | goto out; | |
2091 | ||
2092 | old = real_mount(old_path.mnt); | |
2093 | parent = real_mount(path->mnt); | |
2094 | ||
2095 | err = -EINVAL; | |
2096 | if (IS_MNT_UNBINDABLE(old)) | |
2097 | goto out2; | |
2098 | ||
2099 | if (!check_mnt(parent)) | |
2100 | goto out2; | |
2101 | ||
2102 | if (!check_mnt(old) && old_path.dentry->d_op != &ns_dentry_operations) | |
2103 | goto out2; | |
2104 | ||
2105 | if (!recurse && has_locked_children(old, old_path.dentry)) | |
2106 | goto out2; | |
2107 | ||
2108 | if (recurse) | |
2109 | mnt = copy_tree(old, old_path.dentry, CL_COPY_MNT_NS_FILE); | |
2110 | else | |
2111 | mnt = clone_mnt(old, old_path.dentry, 0); | |
2112 | ||
2113 | if (IS_ERR(mnt)) { | |
2114 | err = PTR_ERR(mnt); | |
2115 | goto out2; | |
2116 | } | |
2117 | ||
2118 | mnt->mnt.mnt_flags &= ~MNT_LOCKED; | |
2119 | ||
2120 | err = graft_tree(mnt, parent, mp); | |
2121 | if (err) { | |
2122 | lock_mount_hash(); | |
2123 | umount_tree(mnt, UMOUNT_SYNC); | |
2124 | unlock_mount_hash(); | |
2125 | } | |
2126 | out2: | |
2127 | unlock_mount(mp); | |
2128 | out: | |
2129 | path_put(&old_path); | |
2130 | return err; | |
2131 | } | |
2132 | ||
2133 | static int change_mount_flags(struct vfsmount *mnt, int ms_flags) | |
2134 | { | |
2135 | int error = 0; | |
2136 | int readonly_request = 0; | |
2137 | ||
2138 | if (ms_flags & MS_RDONLY) | |
2139 | readonly_request = 1; | |
2140 | if (readonly_request == __mnt_is_readonly(mnt)) | |
2141 | return 0; | |
2142 | ||
2143 | if (readonly_request) | |
2144 | error = mnt_make_readonly(real_mount(mnt)); | |
2145 | else | |
2146 | __mnt_unmake_readonly(real_mount(mnt)); | |
2147 | return error; | |
2148 | } | |
2149 | ||
2150 | /* | |
2151 | * change filesystem flags. dir should be a physical root of filesystem. | |
2152 | * If you've mounted a non-root directory somewhere and want to do remount | |
2153 | * on it - tough luck. | |
2154 | */ | |
2155 | static int do_remount(struct path *path, int flags, int mnt_flags, | |
2156 | void *data) | |
2157 | { | |
2158 | int err; | |
2159 | struct super_block *sb = path->mnt->mnt_sb; | |
2160 | struct mount *mnt = real_mount(path->mnt); | |
2161 | ||
2162 | if (!check_mnt(mnt)) | |
2163 | return -EINVAL; | |
2164 | ||
2165 | if (path->dentry != path->mnt->mnt_root) | |
2166 | return -EINVAL; | |
2167 | ||
2168 | /* Don't allow changing of locked mnt flags. | |
2169 | * | |
2170 | * No locks need to be held here while testing the various | |
2171 | * MNT_LOCK flags because those flags can never be cleared | |
2172 | * once they are set. | |
2173 | */ | |
2174 | if ((mnt->mnt.mnt_flags & MNT_LOCK_READONLY) && | |
2175 | !(mnt_flags & MNT_READONLY)) { | |
2176 | return -EPERM; | |
2177 | } | |
2178 | if ((mnt->mnt.mnt_flags & MNT_LOCK_NODEV) && | |
2179 | !(mnt_flags & MNT_NODEV)) { | |
2180 | /* Was the nodev implicitly added in mount? */ | |
2181 | if ((mnt->mnt_ns->user_ns != &init_user_ns) && | |
2182 | !(sb->s_type->fs_flags & FS_USERNS_DEV_MOUNT)) { | |
2183 | mnt_flags |= MNT_NODEV; | |
2184 | } else { | |
2185 | return -EPERM; | |
2186 | } | |
2187 | } | |
2188 | if ((mnt->mnt.mnt_flags & MNT_LOCK_NOSUID) && | |
2189 | !(mnt_flags & MNT_NOSUID)) { | |
2190 | return -EPERM; | |
2191 | } | |
2192 | if ((mnt->mnt.mnt_flags & MNT_LOCK_NOEXEC) && | |
2193 | !(mnt_flags & MNT_NOEXEC)) { | |
2194 | return -EPERM; | |
2195 | } | |
2196 | if ((mnt->mnt.mnt_flags & MNT_LOCK_ATIME) && | |
2197 | ((mnt->mnt.mnt_flags & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK))) { | |
2198 | return -EPERM; | |
2199 | } | |
2200 | ||
2201 | err = security_sb_remount(sb, data); | |
2202 | if (err) | |
2203 | return err; | |
2204 | ||
2205 | down_write(&sb->s_umount); | |
2206 | if (flags & MS_BIND) | |
2207 | err = change_mount_flags(path->mnt, flags); | |
2208 | else if (!capable(CAP_SYS_ADMIN)) | |
2209 | err = -EPERM; | |
2210 | else | |
2211 | err = do_remount_sb(sb, flags, data, 0); | |
2212 | if (!err) { | |
2213 | lock_mount_hash(); | |
2214 | mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK; | |
2215 | mnt->mnt.mnt_flags = mnt_flags; | |
2216 | touch_mnt_namespace(mnt->mnt_ns); | |
2217 | unlock_mount_hash(); | |
2218 | } | |
2219 | up_write(&sb->s_umount); | |
2220 | return err; | |
2221 | } | |
2222 | ||
2223 | static inline int tree_contains_unbindable(struct mount *mnt) | |
2224 | { | |
2225 | struct mount *p; | |
2226 | for (p = mnt; p; p = next_mnt(p, mnt)) { | |
2227 | if (IS_MNT_UNBINDABLE(p)) | |
2228 | return 1; | |
2229 | } | |
2230 | return 0; | |
2231 | } | |
2232 | ||
2233 | static int do_move_mount(struct path *path, const char *old_name) | |
2234 | { | |
2235 | struct path old_path, parent_path; | |
2236 | struct mount *p; | |
2237 | struct mount *old; | |
2238 | struct mountpoint *mp; | |
2239 | int err; | |
2240 | if (!old_name || !*old_name) | |
2241 | return -EINVAL; | |
2242 | err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); | |
2243 | if (err) | |
2244 | return err; | |
2245 | ||
2246 | mp = lock_mount(path); | |
2247 | err = PTR_ERR(mp); | |
2248 | if (IS_ERR(mp)) | |
2249 | goto out; | |
2250 | ||
2251 | old = real_mount(old_path.mnt); | |
2252 | p = real_mount(path->mnt); | |
2253 | ||
2254 | err = -EINVAL; | |
2255 | if (!check_mnt(p) || !check_mnt(old)) | |
2256 | goto out1; | |
2257 | ||
2258 | if (old->mnt.mnt_flags & MNT_LOCKED) | |
2259 | goto out1; | |
2260 | ||
2261 | err = -EINVAL; | |
2262 | if (old_path.dentry != old_path.mnt->mnt_root) | |
2263 | goto out1; | |
2264 | ||
2265 | if (!mnt_has_parent(old)) | |
2266 | goto out1; | |
2267 | ||
2268 | if (d_is_dir(path->dentry) != | |
2269 | d_is_dir(old_path.dentry)) | |
2270 | goto out1; | |
2271 | /* | |
2272 | * Don't move a mount residing in a shared parent. | |
2273 | */ | |
2274 | if (IS_MNT_SHARED(old->mnt_parent)) | |
2275 | goto out1; | |
2276 | /* | |
2277 | * Don't move a mount tree containing unbindable mounts to a destination | |
2278 | * mount which is shared. | |
2279 | */ | |
2280 | if (IS_MNT_SHARED(p) && tree_contains_unbindable(old)) | |
2281 | goto out1; | |
2282 | err = -ELOOP; | |
2283 | for (; mnt_has_parent(p); p = p->mnt_parent) | |
2284 | if (p == old) | |
2285 | goto out1; | |
2286 | ||
2287 | err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path); | |
2288 | if (err) | |
2289 | goto out1; | |
2290 | ||
2291 | /* if the mount is moved, it should no longer be expire | |
2292 | * automatically */ | |
2293 | list_del_init(&old->mnt_expire); | |
2294 | out1: | |
2295 | unlock_mount(mp); | |
2296 | out: | |
2297 | if (!err) | |
2298 | path_put(&parent_path); | |
2299 | path_put(&old_path); | |
2300 | return err; | |
2301 | } | |
2302 | ||
2303 | static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype) | |
2304 | { | |
2305 | int err; | |
2306 | const char *subtype = strchr(fstype, '.'); | |
2307 | if (subtype) { | |
2308 | subtype++; | |
2309 | err = -EINVAL; | |
2310 | if (!subtype[0]) | |
2311 | goto err; | |
2312 | } else | |
2313 | subtype = ""; | |
2314 | ||
2315 | mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL); | |
2316 | err = -ENOMEM; | |
2317 | if (!mnt->mnt_sb->s_subtype) | |
2318 | goto err; | |
2319 | return mnt; | |
2320 | ||
2321 | err: | |
2322 | mntput(mnt); | |
2323 | return ERR_PTR(err); | |
2324 | } | |
2325 | ||
2326 | /* | |
2327 | * add a mount into a namespace's mount tree | |
2328 | */ | |
2329 | static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags) | |
2330 | { | |
2331 | struct mountpoint *mp; | |
2332 | struct mount *parent; | |
2333 | int err; | |
2334 | ||
2335 | mnt_flags &= ~MNT_INTERNAL_FLAGS; | |
2336 | ||
2337 | mp = lock_mount(path); | |
2338 | if (IS_ERR(mp)) | |
2339 | return PTR_ERR(mp); | |
2340 | ||
2341 | parent = real_mount(path->mnt); | |
2342 | err = -EINVAL; | |
2343 | if (unlikely(!check_mnt(parent))) { | |
2344 | /* that's acceptable only for automounts done in private ns */ | |
2345 | if (!(mnt_flags & MNT_SHRINKABLE)) | |
2346 | goto unlock; | |
2347 | /* ... and for those we'd better have mountpoint still alive */ | |
2348 | if (!parent->mnt_ns) | |
2349 | goto unlock; | |
2350 | } | |
2351 | ||
2352 | /* Refuse the same filesystem on the same mount point */ | |
2353 | err = -EBUSY; | |
2354 | if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && | |
2355 | path->mnt->mnt_root == path->dentry) | |
2356 | goto unlock; | |
2357 | ||
2358 | err = -EINVAL; | |
2359 | if (d_is_symlink(newmnt->mnt.mnt_root)) | |
2360 | goto unlock; | |
2361 | ||
2362 | newmnt->mnt.mnt_flags = mnt_flags; | |
2363 | err = graft_tree(newmnt, parent, mp); | |
2364 | ||
2365 | unlock: | |
2366 | unlock_mount(mp); | |
2367 | return err; | |
2368 | } | |
2369 | ||
2370 | static bool fs_fully_visible(struct file_system_type *fs_type, int *new_mnt_flags); | |
2371 | ||
2372 | /* | |
2373 | * create a new mount for userspace and request it to be added into the | |
2374 | * namespace's tree | |
2375 | */ | |
2376 | static int do_new_mount(struct path *path, const char *fstype, int flags, | |
2377 | int mnt_flags, const char *name, void *data) | |
2378 | { | |
2379 | struct file_system_type *type; | |
2380 | struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; | |
2381 | struct vfsmount *mnt; | |
2382 | int err; | |
2383 | ||
2384 | if (!fstype) | |
2385 | return -EINVAL; | |
2386 | ||
2387 | type = get_fs_type(fstype); | |
2388 | if (!type) | |
2389 | return -ENODEV; | |
2390 | ||
2391 | if (user_ns != &init_user_ns) { | |
2392 | if (!(type->fs_flags & FS_USERNS_MOUNT)) { | |
2393 | put_filesystem(type); | |
2394 | return -EPERM; | |
2395 | } | |
2396 | /* Only in special cases allow devices from mounts | |
2397 | * created outside the initial user namespace. | |
2398 | */ | |
2399 | if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) { | |
2400 | flags |= MS_NODEV; | |
2401 | mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV; | |
2402 | } | |
2403 | if (type->fs_flags & FS_USERNS_VISIBLE) { | |
2404 | if (!fs_fully_visible(type, &mnt_flags)) | |
2405 | return -EPERM; | |
2406 | } | |
2407 | } | |
2408 | ||
2409 | mnt = vfs_kern_mount(type, flags, name, data); | |
2410 | if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && | |
2411 | !mnt->mnt_sb->s_subtype) | |
2412 | mnt = fs_set_subtype(mnt, fstype); | |
2413 | ||
2414 | put_filesystem(type); | |
2415 | if (IS_ERR(mnt)) | |
2416 | return PTR_ERR(mnt); | |
2417 | ||
2418 | err = do_add_mount(real_mount(mnt), path, mnt_flags); | |
2419 | if (err) | |
2420 | mntput(mnt); | |
2421 | return err; | |
2422 | } | |
2423 | ||
2424 | int finish_automount(struct vfsmount *m, struct path *path) | |
2425 | { | |
2426 | struct mount *mnt = real_mount(m); | |
2427 | int err; | |
2428 | /* The new mount record should have at least 2 refs to prevent it being | |
2429 | * expired before we get a chance to add it | |
2430 | */ | |
2431 | BUG_ON(mnt_get_count(mnt) < 2); | |
2432 | ||
2433 | if (m->mnt_sb == path->mnt->mnt_sb && | |
2434 | m->mnt_root == path->dentry) { | |
2435 | err = -ELOOP; | |
2436 | goto fail; | |
2437 | } | |
2438 | ||
2439 | err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE); | |
2440 | if (!err) | |
2441 | return 0; | |
2442 | fail: | |
2443 | /* remove m from any expiration list it may be on */ | |
2444 | if (!list_empty(&mnt->mnt_expire)) { | |
2445 | namespace_lock(); | |
2446 | list_del_init(&mnt->mnt_expire); | |
2447 | namespace_unlock(); | |
2448 | } | |
2449 | mntput(m); | |
2450 | mntput(m); | |
2451 | return err; | |
2452 | } | |
2453 | ||
2454 | /** | |
2455 | * mnt_set_expiry - Put a mount on an expiration list | |
2456 | * @mnt: The mount to list. | |
2457 | * @expiry_list: The list to add the mount to. | |
2458 | */ | |
2459 | void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list) | |
2460 | { | |
2461 | namespace_lock(); | |
2462 | ||
2463 | list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list); | |
2464 | ||
2465 | namespace_unlock(); | |
2466 | } | |
2467 | EXPORT_SYMBOL(mnt_set_expiry); | |
2468 | ||
2469 | /* | |
2470 | * process a list of expirable mountpoints with the intent of discarding any | |
2471 | * mountpoints that aren't in use and haven't been touched since last we came | |
2472 | * here | |
2473 | */ | |
2474 | void mark_mounts_for_expiry(struct list_head *mounts) | |
2475 | { | |
2476 | struct mount *mnt, *next; | |
2477 | LIST_HEAD(graveyard); | |
2478 | ||
2479 | if (list_empty(mounts)) | |
2480 | return; | |
2481 | ||
2482 | namespace_lock(); | |
2483 | lock_mount_hash(); | |
2484 | ||
2485 | /* extract from the expiration list every vfsmount that matches the | |
2486 | * following criteria: | |
2487 | * - only referenced by its parent vfsmount | |
2488 | * - still marked for expiry (marked on the last call here; marks are | |
2489 | * cleared by mntput()) | |
2490 | */ | |
2491 | list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { | |
2492 | if (!xchg(&mnt->mnt_expiry_mark, 1) || | |
2493 | propagate_mount_busy(mnt, 1)) | |
2494 | continue; | |
2495 | list_move(&mnt->mnt_expire, &graveyard); | |
2496 | } | |
2497 | while (!list_empty(&graveyard)) { | |
2498 | mnt = list_first_entry(&graveyard, struct mount, mnt_expire); | |
2499 | touch_mnt_namespace(mnt->mnt_ns); | |
2500 | umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC); | |
2501 | } | |
2502 | unlock_mount_hash(); | |
2503 | namespace_unlock(); | |
2504 | } | |
2505 | ||
2506 | EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); | |
2507 | ||
2508 | /* | |
2509 | * Ripoff of 'select_parent()' | |
2510 | * | |
2511 | * search the list of submounts for a given mountpoint, and move any | |
2512 | * shrinkable submounts to the 'graveyard' list. | |
2513 | */ | |
2514 | static int select_submounts(struct mount *parent, struct list_head *graveyard) | |
2515 | { | |
2516 | struct mount *this_parent = parent; | |
2517 | struct list_head *next; | |
2518 | int found = 0; | |
2519 | ||
2520 | repeat: | |
2521 | next = this_parent->mnt_mounts.next; | |
2522 | resume: | |
2523 | while (next != &this_parent->mnt_mounts) { | |
2524 | struct list_head *tmp = next; | |
2525 | struct mount *mnt = list_entry(tmp, struct mount, mnt_child); | |
2526 | ||
2527 | next = tmp->next; | |
2528 | if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE)) | |
2529 | continue; | |
2530 | /* | |
2531 | * Descend a level if the d_mounts list is non-empty. | |
2532 | */ | |
2533 | if (!list_empty(&mnt->mnt_mounts)) { | |
2534 | this_parent = mnt; | |
2535 | goto repeat; | |
2536 | } | |
2537 | ||
2538 | if (!propagate_mount_busy(mnt, 1)) { | |
2539 | list_move_tail(&mnt->mnt_expire, graveyard); | |
2540 | found++; | |
2541 | } | |
2542 | } | |
2543 | /* | |
2544 | * All done at this level ... ascend and resume the search | |
2545 | */ | |
2546 | if (this_parent != parent) { | |
2547 | next = this_parent->mnt_child.next; | |
2548 | this_parent = this_parent->mnt_parent; | |
2549 | goto resume; | |
2550 | } | |
2551 | return found; | |
2552 | } | |
2553 | ||
2554 | /* | |
2555 | * process a list of expirable mountpoints with the intent of discarding any | |
2556 | * submounts of a specific parent mountpoint | |
2557 | * | |
2558 | * mount_lock must be held for write | |
2559 | */ | |
2560 | static void shrink_submounts(struct mount *mnt) | |
2561 | { | |
2562 | LIST_HEAD(graveyard); | |
2563 | struct mount *m; | |
2564 | ||
2565 | /* extract submounts of 'mountpoint' from the expiration list */ | |
2566 | while (select_submounts(mnt, &graveyard)) { | |
2567 | while (!list_empty(&graveyard)) { | |
2568 | m = list_first_entry(&graveyard, struct mount, | |
2569 | mnt_expire); | |
2570 | touch_mnt_namespace(m->mnt_ns); | |
2571 | umount_tree(m, UMOUNT_PROPAGATE|UMOUNT_SYNC); | |
2572 | } | |
2573 | } | |
2574 | } | |
2575 | ||
2576 | /* | |
2577 | * Some copy_from_user() implementations do not return the exact number of | |
2578 | * bytes remaining to copy on a fault. But copy_mount_options() requires that. | |
2579 | * Note that this function differs from copy_from_user() in that it will oops | |
2580 | * on bad values of `to', rather than returning a short copy. | |
2581 | */ | |
2582 | static long exact_copy_from_user(void *to, const void __user * from, | |
2583 | unsigned long n) | |
2584 | { | |
2585 | char *t = to; | |
2586 | const char __user *f = from; | |
2587 | char c; | |
2588 | ||
2589 | if (!access_ok(VERIFY_READ, from, n)) | |
2590 | return n; | |
2591 | ||
2592 | while (n) { | |
2593 | if (__get_user(c, f)) { | |
2594 | memset(t, 0, n); | |
2595 | break; | |
2596 | } | |
2597 | *t++ = c; | |
2598 | f++; | |
2599 | n--; | |
2600 | } | |
2601 | return n; | |
2602 | } | |
2603 | ||
2604 | int copy_mount_options(const void __user * data, unsigned long *where) | |
2605 | { | |
2606 | int i; | |
2607 | unsigned long page; | |
2608 | unsigned long size; | |
2609 | ||
2610 | *where = 0; | |
2611 | if (!data) | |
2612 | return 0; | |
2613 | ||
2614 | if (!(page = __get_free_page(GFP_KERNEL))) | |
2615 | return -ENOMEM; | |
2616 | ||
2617 | /* We only care that *some* data at the address the user | |
2618 | * gave us is valid. Just in case, we'll zero | |
2619 | * the remainder of the page. | |
2620 | */ | |
2621 | /* copy_from_user cannot cross TASK_SIZE ! */ | |
2622 | size = TASK_SIZE - (unsigned long)data; | |
2623 | if (size > PAGE_SIZE) | |
2624 | size = PAGE_SIZE; | |
2625 | ||
2626 | i = size - exact_copy_from_user((void *)page, data, size); | |
2627 | if (!i) { | |
2628 | free_page(page); | |
2629 | return -EFAULT; | |
2630 | } | |
2631 | if (i != PAGE_SIZE) | |
2632 | memset((char *)page + i, 0, PAGE_SIZE - i); | |
2633 | *where = page; | |
2634 | return 0; | |
2635 | } | |
2636 | ||
2637 | char *copy_mount_string(const void __user *data) | |
2638 | { | |
2639 | return data ? strndup_user(data, PAGE_SIZE) : NULL; | |
2640 | } | |
2641 | ||
2642 | /* | |
2643 | * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to | |
2644 | * be given to the mount() call (ie: read-only, no-dev, no-suid etc). | |
2645 | * | |
2646 | * data is a (void *) that can point to any structure up to | |
2647 | * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent | |
2648 | * information (or be NULL). | |
2649 | * | |
2650 | * Pre-0.97 versions of mount() didn't have a flags word. | |
2651 | * When the flags word was introduced its top half was required | |
2652 | * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. | |
2653 | * Therefore, if this magic number is present, it carries no information | |
2654 | * and must be discarded. | |
2655 | */ | |
2656 | long do_mount(const char *dev_name, const char __user *dir_name, | |
2657 | const char *type_page, unsigned long flags, void *data_page) | |
2658 | { | |
2659 | struct path path; | |
2660 | int retval = 0; | |
2661 | int mnt_flags = 0; | |
2662 | ||
2663 | /* Discard magic */ | |
2664 | if ((flags & MS_MGC_MSK) == MS_MGC_VAL) | |
2665 | flags &= ~MS_MGC_MSK; | |
2666 | ||
2667 | /* Basic sanity checks */ | |
2668 | if (data_page) | |
2669 | ((char *)data_page)[PAGE_SIZE - 1] = 0; | |
2670 | ||
2671 | /* ... and get the mountpoint */ | |
2672 | retval = user_path(dir_name, &path); | |
2673 | if (retval) | |
2674 | return retval; | |
2675 | ||
2676 | retval = security_sb_mount(dev_name, &path, | |
2677 | type_page, flags, data_page); | |
2678 | if (!retval && !may_mount()) | |
2679 | retval = -EPERM; | |
2680 | if (retval) | |
2681 | goto dput_out; | |
2682 | ||
2683 | /* Default to relatime unless overriden */ | |
2684 | if (!(flags & MS_NOATIME)) | |
2685 | mnt_flags |= MNT_RELATIME; | |
2686 | ||
2687 | /* Separate the per-mountpoint flags */ | |
2688 | if (flags & MS_NOSUID) | |
2689 | mnt_flags |= MNT_NOSUID; | |
2690 | if (flags & MS_NODEV) | |
2691 | mnt_flags |= MNT_NODEV; | |
2692 | if (flags & MS_NOEXEC) | |
2693 | mnt_flags |= MNT_NOEXEC; | |
2694 | if (flags & MS_NOATIME) | |
2695 | mnt_flags |= MNT_NOATIME; | |
2696 | if (flags & MS_NODIRATIME) | |
2697 | mnt_flags |= MNT_NODIRATIME; | |
2698 | if (flags & MS_STRICTATIME) | |
2699 | mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); | |
2700 | if (flags & MS_RDONLY) | |
2701 | mnt_flags |= MNT_READONLY; | |
2702 | ||
2703 | /* The default atime for remount is preservation */ | |
2704 | if ((flags & MS_REMOUNT) && | |
2705 | ((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME | | |
2706 | MS_STRICTATIME)) == 0)) { | |
2707 | mnt_flags &= ~MNT_ATIME_MASK; | |
2708 | mnt_flags |= path.mnt->mnt_flags & MNT_ATIME_MASK; | |
2709 | } | |
2710 | ||
2711 | flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN | | |
2712 | MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT | | |
2713 | MS_STRICTATIME); | |
2714 | ||
2715 | if (flags & MS_REMOUNT) | |
2716 | retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags, | |
2717 | data_page); | |
2718 | else if (flags & MS_BIND) | |
2719 | retval = do_loopback(&path, dev_name, flags & MS_REC); | |
2720 | else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) | |
2721 | retval = do_change_type(&path, flags); | |
2722 | else if (flags & MS_MOVE) | |
2723 | retval = do_move_mount(&path, dev_name); | |
2724 | else | |
2725 | retval = do_new_mount(&path, type_page, flags, mnt_flags, | |
2726 | dev_name, data_page); | |
2727 | dput_out: | |
2728 | path_put(&path); | |
2729 | return retval; | |
2730 | } | |
2731 | ||
2732 | static void free_mnt_ns(struct mnt_namespace *ns) | |
2733 | { | |
2734 | ns_free_inum(&ns->ns); | |
2735 | put_user_ns(ns->user_ns); | |
2736 | kfree(ns); | |
2737 | } | |
2738 | ||
2739 | /* | |
2740 | * Assign a sequence number so we can detect when we attempt to bind | |
2741 | * mount a reference to an older mount namespace into the current | |
2742 | * mount namespace, preventing reference counting loops. A 64bit | |
2743 | * number incrementing at 10Ghz will take 12,427 years to wrap which | |
2744 | * is effectively never, so we can ignore the possibility. | |
2745 | */ | |
2746 | static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1); | |
2747 | ||
2748 | static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns) | |
2749 | { | |
2750 | struct mnt_namespace *new_ns; | |
2751 | int ret; | |
2752 | ||
2753 | new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); | |
2754 | if (!new_ns) | |
2755 | return ERR_PTR(-ENOMEM); | |
2756 | ret = ns_alloc_inum(&new_ns->ns); | |
2757 | if (ret) { | |
2758 | kfree(new_ns); | |
2759 | return ERR_PTR(ret); | |
2760 | } | |
2761 | new_ns->ns.ops = &mntns_operations; | |
2762 | new_ns->seq = atomic64_add_return(1, &mnt_ns_seq); | |
2763 | atomic_set(&new_ns->count, 1); | |
2764 | new_ns->root = NULL; | |
2765 | INIT_LIST_HEAD(&new_ns->list); | |
2766 | init_waitqueue_head(&new_ns->poll); | |
2767 | new_ns->event = 0; | |
2768 | new_ns->user_ns = get_user_ns(user_ns); | |
2769 | return new_ns; | |
2770 | } | |
2771 | ||
2772 | struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, | |
2773 | struct user_namespace *user_ns, struct fs_struct *new_fs) | |
2774 | { | |
2775 | struct mnt_namespace *new_ns; | |
2776 | struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; | |
2777 | struct mount *p, *q; | |
2778 | struct mount *old; | |
2779 | struct mount *new; | |
2780 | int copy_flags; | |
2781 | ||
2782 | BUG_ON(!ns); | |
2783 | ||
2784 | if (likely(!(flags & CLONE_NEWNS))) { | |
2785 | get_mnt_ns(ns); | |
2786 | return ns; | |
2787 | } | |
2788 | ||
2789 | old = ns->root; | |
2790 | ||
2791 | new_ns = alloc_mnt_ns(user_ns); | |
2792 | if (IS_ERR(new_ns)) | |
2793 | return new_ns; | |
2794 | ||
2795 | namespace_lock(); | |
2796 | /* First pass: copy the tree topology */ | |
2797 | copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE; | |
2798 | if (user_ns != ns->user_ns) | |
2799 | copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED; | |
2800 | new = copy_tree(old, old->mnt.mnt_root, copy_flags); | |
2801 | if (IS_ERR(new)) { | |
2802 | namespace_unlock(); | |
2803 | free_mnt_ns(new_ns); | |
2804 | return ERR_CAST(new); | |
2805 | } | |
2806 | new_ns->root = new; | |
2807 | list_add_tail(&new_ns->list, &new->mnt_list); | |
2808 | ||
2809 | /* | |
2810 | * Second pass: switch the tsk->fs->* elements and mark new vfsmounts | |
2811 | * as belonging to new namespace. We have already acquired a private | |
2812 | * fs_struct, so tsk->fs->lock is not needed. | |
2813 | */ | |
2814 | p = old; | |
2815 | q = new; | |
2816 | while (p) { | |
2817 | q->mnt_ns = new_ns; | |
2818 | if (new_fs) { | |
2819 | if (&p->mnt == new_fs->root.mnt) { | |
2820 | new_fs->root.mnt = mntget(&q->mnt); | |
2821 | rootmnt = &p->mnt; | |
2822 | } | |
2823 | if (&p->mnt == new_fs->pwd.mnt) { | |
2824 | new_fs->pwd.mnt = mntget(&q->mnt); | |
2825 | pwdmnt = &p->mnt; | |
2826 | } | |
2827 | } | |
2828 | p = next_mnt(p, old); | |
2829 | q = next_mnt(q, new); | |
2830 | if (!q) | |
2831 | break; | |
2832 | while (p->mnt.mnt_root != q->mnt.mnt_root) | |
2833 | p = next_mnt(p, old); | |
2834 | } | |
2835 | namespace_unlock(); | |
2836 | ||
2837 | if (rootmnt) | |
2838 | mntput(rootmnt); | |
2839 | if (pwdmnt) | |
2840 | mntput(pwdmnt); | |
2841 | ||
2842 | return new_ns; | |
2843 | } | |
2844 | ||
2845 | /** | |
2846 | * create_mnt_ns - creates a private namespace and adds a root filesystem | |
2847 | * @mnt: pointer to the new root filesystem mountpoint | |
2848 | */ | |
2849 | static struct mnt_namespace *create_mnt_ns(struct vfsmount *m) | |
2850 | { | |
2851 | struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns); | |
2852 | if (!IS_ERR(new_ns)) { | |
2853 | struct mount *mnt = real_mount(m); | |
2854 | mnt->mnt_ns = new_ns; | |
2855 | new_ns->root = mnt; | |
2856 | list_add(&mnt->mnt_list, &new_ns->list); | |
2857 | } else { | |
2858 | mntput(m); | |
2859 | } | |
2860 | return new_ns; | |
2861 | } | |
2862 | ||
2863 | struct dentry *mount_subtree(struct vfsmount *mnt, const char *name) | |
2864 | { | |
2865 | struct mnt_namespace *ns; | |
2866 | struct super_block *s; | |
2867 | struct path path; | |
2868 | int err; | |
2869 | ||
2870 | ns = create_mnt_ns(mnt); | |
2871 | if (IS_ERR(ns)) | |
2872 | return ERR_CAST(ns); | |
2873 | ||
2874 | err = vfs_path_lookup(mnt->mnt_root, mnt, | |
2875 | name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); | |
2876 | ||
2877 | put_mnt_ns(ns); | |
2878 | ||
2879 | if (err) | |
2880 | return ERR_PTR(err); | |
2881 | ||
2882 | /* trade a vfsmount reference for active sb one */ | |
2883 | s = path.mnt->mnt_sb; | |
2884 | atomic_inc(&s->s_active); | |
2885 | mntput(path.mnt); | |
2886 | /* lock the sucker */ | |
2887 | down_write(&s->s_umount); | |
2888 | /* ... and return the root of (sub)tree on it */ | |
2889 | return path.dentry; | |
2890 | } | |
2891 | EXPORT_SYMBOL(mount_subtree); | |
2892 | ||
2893 | SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, | |
2894 | char __user *, type, unsigned long, flags, void __user *, data) | |
2895 | { | |
2896 | int ret; | |
2897 | char *kernel_type; | |
2898 | char *kernel_dev; | |
2899 | unsigned long data_page; | |
2900 | ||
2901 | kernel_type = copy_mount_string(type); | |
2902 | ret = PTR_ERR(kernel_type); | |
2903 | if (IS_ERR(kernel_type)) | |
2904 | goto out_type; | |
2905 | ||
2906 | kernel_dev = copy_mount_string(dev_name); | |
2907 | ret = PTR_ERR(kernel_dev); | |
2908 | if (IS_ERR(kernel_dev)) | |
2909 | goto out_dev; | |
2910 | ||
2911 | ret = copy_mount_options(data, &data_page); | |
2912 | if (ret < 0) | |
2913 | goto out_data; | |
2914 | ||
2915 | ret = do_mount(kernel_dev, dir_name, kernel_type, flags, | |
2916 | (void *) data_page); | |
2917 | ||
2918 | free_page(data_page); | |
2919 | out_data: | |
2920 | kfree(kernel_dev); | |
2921 | out_dev: | |
2922 | kfree(kernel_type); | |
2923 | out_type: | |
2924 | return ret; | |
2925 | } | |
2926 | ||
2927 | /* | |
2928 | * Return true if path is reachable from root | |
2929 | * | |
2930 | * namespace_sem or mount_lock is held | |
2931 | */ | |
2932 | bool is_path_reachable(struct mount *mnt, struct dentry *dentry, | |
2933 | const struct path *root) | |
2934 | { | |
2935 | while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) { | |
2936 | dentry = mnt->mnt_mountpoint; | |
2937 | mnt = mnt->mnt_parent; | |
2938 | } | |
2939 | return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry); | |
2940 | } | |
2941 | ||
2942 | int path_is_under(struct path *path1, struct path *path2) | |
2943 | { | |
2944 | int res; | |
2945 | read_seqlock_excl(&mount_lock); | |
2946 | res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2); | |
2947 | read_sequnlock_excl(&mount_lock); | |
2948 | return res; | |
2949 | } | |
2950 | EXPORT_SYMBOL(path_is_under); | |
2951 | ||
2952 | /* | |
2953 | * pivot_root Semantics: | |
2954 | * Moves the root file system of the current process to the directory put_old, | |
2955 | * makes new_root as the new root file system of the current process, and sets | |
2956 | * root/cwd of all processes which had them on the current root to new_root. | |
2957 | * | |
2958 | * Restrictions: | |
2959 | * The new_root and put_old must be directories, and must not be on the | |
2960 | * same file system as the current process root. The put_old must be | |
2961 | * underneath new_root, i.e. adding a non-zero number of /.. to the string | |
2962 | * pointed to by put_old must yield the same directory as new_root. No other | |
2963 | * file system may be mounted on put_old. After all, new_root is a mountpoint. | |
2964 | * | |
2965 | * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. | |
2966 | * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives | |
2967 | * in this situation. | |
2968 | * | |
2969 | * Notes: | |
2970 | * - we don't move root/cwd if they are not at the root (reason: if something | |
2971 | * cared enough to change them, it's probably wrong to force them elsewhere) | |
2972 | * - it's okay to pick a root that isn't the root of a file system, e.g. | |
2973 | * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, | |
2974 | * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root | |
2975 | * first. | |
2976 | */ | |
2977 | SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, | |
2978 | const char __user *, put_old) | |
2979 | { | |
2980 | struct path new, old, parent_path, root_parent, root; | |
2981 | struct mount *new_mnt, *root_mnt, *old_mnt; | |
2982 | struct mountpoint *old_mp, *root_mp; | |
2983 | int error; | |
2984 | ||
2985 | if (!may_mount()) | |
2986 | return -EPERM; | |
2987 | ||
2988 | error = user_path_dir(new_root, &new); | |
2989 | if (error) | |
2990 | goto out0; | |
2991 | ||
2992 | error = user_path_dir(put_old, &old); | |
2993 | if (error) | |
2994 | goto out1; | |
2995 | ||
2996 | error = security_sb_pivotroot(&old, &new); | |
2997 | if (error) | |
2998 | goto out2; | |
2999 | ||
3000 | get_fs_root(current->fs, &root); | |
3001 | old_mp = lock_mount(&old); | |
3002 | error = PTR_ERR(old_mp); | |
3003 | if (IS_ERR(old_mp)) | |
3004 | goto out3; | |
3005 | ||
3006 | error = -EINVAL; | |
3007 | new_mnt = real_mount(new.mnt); | |
3008 | root_mnt = real_mount(root.mnt); | |
3009 | old_mnt = real_mount(old.mnt); | |
3010 | if (IS_MNT_SHARED(old_mnt) || | |
3011 | IS_MNT_SHARED(new_mnt->mnt_parent) || | |
3012 | IS_MNT_SHARED(root_mnt->mnt_parent)) | |
3013 | goto out4; | |
3014 | if (!check_mnt(root_mnt) || !check_mnt(new_mnt)) | |
3015 | goto out4; | |
3016 | if (new_mnt->mnt.mnt_flags & MNT_LOCKED) | |
3017 | goto out4; | |
3018 | error = -ENOENT; | |
3019 | if (d_unlinked(new.dentry)) | |
3020 | goto out4; | |
3021 | error = -EBUSY; | |
3022 | if (new_mnt == root_mnt || old_mnt == root_mnt) | |
3023 | goto out4; /* loop, on the same file system */ | |
3024 | error = -EINVAL; | |
3025 | if (root.mnt->mnt_root != root.dentry) | |
3026 | goto out4; /* not a mountpoint */ | |
3027 | if (!mnt_has_parent(root_mnt)) | |
3028 | goto out4; /* not attached */ | |
3029 | root_mp = root_mnt->mnt_mp; | |
3030 | if (new.mnt->mnt_root != new.dentry) | |
3031 | goto out4; /* not a mountpoint */ | |
3032 | if (!mnt_has_parent(new_mnt)) | |
3033 | goto out4; /* not attached */ | |
3034 | /* make sure we can reach put_old from new_root */ | |
3035 | if (!is_path_reachable(old_mnt, old.dentry, &new)) | |
3036 | goto out4; | |
3037 | /* make certain new is below the root */ | |
3038 | if (!is_path_reachable(new_mnt, new.dentry, &root)) | |
3039 | goto out4; | |
3040 | root_mp->m_count++; /* pin it so it won't go away */ | |
3041 | lock_mount_hash(); | |
3042 | detach_mnt(new_mnt, &parent_path); | |
3043 | detach_mnt(root_mnt, &root_parent); | |
3044 | if (root_mnt->mnt.mnt_flags & MNT_LOCKED) { | |
3045 | new_mnt->mnt.mnt_flags |= MNT_LOCKED; | |
3046 | root_mnt->mnt.mnt_flags &= ~MNT_LOCKED; | |
3047 | } | |
3048 | /* mount old root on put_old */ | |
3049 | attach_mnt(root_mnt, old_mnt, old_mp); | |
3050 | /* mount new_root on / */ | |
3051 | attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp); | |
3052 | touch_mnt_namespace(current->nsproxy->mnt_ns); | |
3053 | /* A moved mount should not expire automatically */ | |
3054 | list_del_init(&new_mnt->mnt_expire); | |
3055 | unlock_mount_hash(); | |
3056 | chroot_fs_refs(&root, &new); | |
3057 | put_mountpoint(root_mp); | |
3058 | error = 0; | |
3059 | out4: | |
3060 | unlock_mount(old_mp); | |
3061 | if (!error) { | |
3062 | path_put(&root_parent); | |
3063 | path_put(&parent_path); | |
3064 | } | |
3065 | out3: | |
3066 | path_put(&root); | |
3067 | out2: | |
3068 | path_put(&old); | |
3069 | out1: | |
3070 | path_put(&new); | |
3071 | out0: | |
3072 | return error; | |
3073 | } | |
3074 | ||
3075 | static void __init init_mount_tree(void) | |
3076 | { | |
3077 | struct vfsmount *mnt; | |
3078 | struct mnt_namespace *ns; | |
3079 | struct path root; | |
3080 | struct file_system_type *type; | |
3081 | ||
3082 | type = get_fs_type("rootfs"); | |
3083 | if (!type) | |
3084 | panic("Can't find rootfs type"); | |
3085 | mnt = vfs_kern_mount(type, 0, "rootfs", NULL); | |
3086 | put_filesystem(type); | |
3087 | if (IS_ERR(mnt)) | |
3088 | panic("Can't create rootfs"); | |
3089 | ||
3090 | ns = create_mnt_ns(mnt); | |
3091 | if (IS_ERR(ns)) | |
3092 | panic("Can't allocate initial namespace"); | |
3093 | ||
3094 | init_task.nsproxy->mnt_ns = ns; | |
3095 | get_mnt_ns(ns); | |
3096 | ||
3097 | root.mnt = mnt; | |
3098 | root.dentry = mnt->mnt_root; | |
3099 | mnt->mnt_flags |= MNT_LOCKED; | |
3100 | ||
3101 | set_fs_pwd(current->fs, &root); | |
3102 | set_fs_root(current->fs, &root); | |
3103 | } | |
3104 | ||
3105 | void __init mnt_init(void) | |
3106 | { | |
3107 | unsigned u; | |
3108 | int err; | |
3109 | ||
3110 | mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount), | |
3111 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); | |
3112 | ||
3113 | mount_hashtable = alloc_large_system_hash("Mount-cache", | |
3114 | sizeof(struct hlist_head), | |
3115 | mhash_entries, 19, | |
3116 | 0, | |
3117 | &m_hash_shift, &m_hash_mask, 0, 0); | |
3118 | mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache", | |
3119 | sizeof(struct hlist_head), | |
3120 | mphash_entries, 19, | |
3121 | 0, | |
3122 | &mp_hash_shift, &mp_hash_mask, 0, 0); | |
3123 | ||
3124 | if (!mount_hashtable || !mountpoint_hashtable) | |
3125 | panic("Failed to allocate mount hash table\n"); | |
3126 | ||
3127 | for (u = 0; u <= m_hash_mask; u++) | |
3128 | INIT_HLIST_HEAD(&mount_hashtable[u]); | |
3129 | for (u = 0; u <= mp_hash_mask; u++) | |
3130 | INIT_HLIST_HEAD(&mountpoint_hashtable[u]); | |
3131 | ||
3132 | kernfs_init(); | |
3133 | ||
3134 | err = sysfs_init(); | |
3135 | if (err) | |
3136 | printk(KERN_WARNING "%s: sysfs_init error: %d\n", | |
3137 | __func__, err); | |
3138 | fs_kobj = kobject_create_and_add("fs", NULL); | |
3139 | if (!fs_kobj) | |
3140 | printk(KERN_WARNING "%s: kobj create error\n", __func__); | |
3141 | init_rootfs(); | |
3142 | init_mount_tree(); | |
3143 | } | |
3144 | ||
3145 | void put_mnt_ns(struct mnt_namespace *ns) | |
3146 | { | |
3147 | if (!atomic_dec_and_test(&ns->count)) | |
3148 | return; | |
3149 | drop_collected_mounts(&ns->root->mnt); | |
3150 | free_mnt_ns(ns); | |
3151 | } | |
3152 | ||
3153 | struct vfsmount *kern_mount_data(struct file_system_type *type, void *data) | |
3154 | { | |
3155 | struct vfsmount *mnt; | |
3156 | mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data); | |
3157 | if (!IS_ERR(mnt)) { | |
3158 | /* | |
3159 | * it is a longterm mount, don't release mnt until | |
3160 | * we unmount before file sys is unregistered | |
3161 | */ | |
3162 | real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL; | |
3163 | } | |
3164 | return mnt; | |
3165 | } | |
3166 | EXPORT_SYMBOL_GPL(kern_mount_data); | |
3167 | ||
3168 | void kern_unmount(struct vfsmount *mnt) | |
3169 | { | |
3170 | /* release long term mount so mount point can be released */ | |
3171 | if (!IS_ERR_OR_NULL(mnt)) { | |
3172 | real_mount(mnt)->mnt_ns = NULL; | |
3173 | synchronize_rcu(); /* yecchhh... */ | |
3174 | mntput(mnt); | |
3175 | } | |
3176 | } | |
3177 | EXPORT_SYMBOL(kern_unmount); | |
3178 | ||
3179 | bool our_mnt(struct vfsmount *mnt) | |
3180 | { | |
3181 | return check_mnt(real_mount(mnt)); | |
3182 | } | |
3183 | ||
3184 | bool current_chrooted(void) | |
3185 | { | |
3186 | /* Does the current process have a non-standard root */ | |
3187 | struct path ns_root; | |
3188 | struct path fs_root; | |
3189 | bool chrooted; | |
3190 | ||
3191 | /* Find the namespace root */ | |
3192 | ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt; | |
3193 | ns_root.dentry = ns_root.mnt->mnt_root; | |
3194 | path_get(&ns_root); | |
3195 | while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root)) | |
3196 | ; | |
3197 | ||
3198 | get_fs_root(current->fs, &fs_root); | |
3199 | ||
3200 | chrooted = !path_equal(&fs_root, &ns_root); | |
3201 | ||
3202 | path_put(&fs_root); | |
3203 | path_put(&ns_root); | |
3204 | ||
3205 | return chrooted; | |
3206 | } | |
3207 | ||
3208 | static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags) | |
3209 | { | |
3210 | struct mnt_namespace *ns = current->nsproxy->mnt_ns; | |
3211 | int new_flags = *new_mnt_flags; | |
3212 | struct mount *mnt; | |
3213 | bool visible = false; | |
3214 | ||
3215 | if (unlikely(!ns)) | |
3216 | return false; | |
3217 | ||
3218 | down_read(&namespace_sem); | |
3219 | list_for_each_entry(mnt, &ns->list, mnt_list) { | |
3220 | struct mount *child; | |
3221 | int mnt_flags; | |
3222 | ||
3223 | if (mnt->mnt.mnt_sb->s_type != type) | |
3224 | continue; | |
3225 | ||
3226 | /* This mount is not fully visible if it's root directory | |
3227 | * is not the root directory of the filesystem. | |
3228 | */ | |
3229 | if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root) | |
3230 | continue; | |
3231 | ||
3232 | /* Read the mount flags and filter out flags that | |
3233 | * may safely be ignored. | |
3234 | */ | |
3235 | mnt_flags = mnt->mnt.mnt_flags; | |
3236 | if (mnt->mnt.mnt_sb->s_iflags & SB_I_NOEXEC) | |
3237 | mnt_flags &= ~(MNT_LOCK_NOSUID | MNT_LOCK_NOEXEC); | |
3238 | ||
3239 | /* Verify the mount flags are equal to or more permissive | |
3240 | * than the proposed new mount. | |
3241 | */ | |
3242 | if ((mnt_flags & MNT_LOCK_READONLY) && | |
3243 | !(new_flags & MNT_READONLY)) | |
3244 | continue; | |
3245 | if ((mnt_flags & MNT_LOCK_NODEV) && | |
3246 | !(new_flags & MNT_NODEV)) | |
3247 | continue; | |
3248 | if ((mnt_flags & MNT_LOCK_NOSUID) && | |
3249 | !(new_flags & MNT_NOSUID)) | |
3250 | continue; | |
3251 | if ((mnt_flags & MNT_LOCK_NOEXEC) && | |
3252 | !(new_flags & MNT_NOEXEC)) | |
3253 | continue; | |
3254 | if ((mnt_flags & MNT_LOCK_ATIME) && | |
3255 | ((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK))) | |
3256 | continue; | |
3257 | ||
3258 | /* This mount is not fully visible if there are any | |
3259 | * locked child mounts that cover anything except for | |
3260 | * empty directories. | |
3261 | */ | |
3262 | list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { | |
3263 | struct inode *inode = child->mnt_mountpoint->d_inode; | |
3264 | /* Only worry about locked mounts */ | |
3265 | if (!(mnt_flags & MNT_LOCKED)) | |
3266 | continue; | |
3267 | /* Is the directory permanetly empty? */ | |
3268 | if (!is_empty_dir_inode(inode)) | |
3269 | goto next; | |
3270 | } | |
3271 | /* Preserve the locked attributes */ | |
3272 | *new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \ | |
3273 | MNT_LOCK_NODEV | \ | |
3274 | MNT_LOCK_NOSUID | \ | |
3275 | MNT_LOCK_NOEXEC | \ | |
3276 | MNT_LOCK_ATIME); | |
3277 | visible = true; | |
3278 | goto found; | |
3279 | next: ; | |
3280 | } | |
3281 | found: | |
3282 | up_read(&namespace_sem); | |
3283 | return visible; | |
3284 | } | |
3285 | ||
3286 | static struct ns_common *mntns_get(struct task_struct *task) | |
3287 | { | |
3288 | struct ns_common *ns = NULL; | |
3289 | struct nsproxy *nsproxy; | |
3290 | ||
3291 | task_lock(task); | |
3292 | nsproxy = task->nsproxy; | |
3293 | if (nsproxy) { | |
3294 | ns = &nsproxy->mnt_ns->ns; | |
3295 | get_mnt_ns(to_mnt_ns(ns)); | |
3296 | } | |
3297 | task_unlock(task); | |
3298 | ||
3299 | return ns; | |
3300 | } | |
3301 | ||
3302 | static void mntns_put(struct ns_common *ns) | |
3303 | { | |
3304 | put_mnt_ns(to_mnt_ns(ns)); | |
3305 | } | |
3306 | ||
3307 | static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns) | |
3308 | { | |
3309 | struct fs_struct *fs = current->fs; | |
3310 | struct mnt_namespace *mnt_ns = to_mnt_ns(ns); | |
3311 | struct path root; | |
3312 | ||
3313 | if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) || | |
3314 | !ns_capable(current_user_ns(), CAP_SYS_CHROOT) || | |
3315 | !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) | |
3316 | return -EPERM; | |
3317 | ||
3318 | if (fs->users != 1) | |
3319 | return -EINVAL; | |
3320 | ||
3321 | get_mnt_ns(mnt_ns); | |
3322 | put_mnt_ns(nsproxy->mnt_ns); | |
3323 | nsproxy->mnt_ns = mnt_ns; | |
3324 | ||
3325 | /* Find the root */ | |
3326 | root.mnt = &mnt_ns->root->mnt; | |
3327 | root.dentry = mnt_ns->root->mnt.mnt_root; | |
3328 | path_get(&root); | |
3329 | while(d_mountpoint(root.dentry) && follow_down_one(&root)) | |
3330 | ; | |
3331 | ||
3332 | /* Update the pwd and root */ | |
3333 | set_fs_pwd(fs, &root); | |
3334 | set_fs_root(fs, &root); | |
3335 | ||
3336 | path_put(&root); | |
3337 | return 0; | |
3338 | } | |
3339 | ||
3340 | const struct proc_ns_operations mntns_operations = { | |
3341 | .name = "mnt", | |
3342 | .type = CLONE_NEWNS, | |
3343 | .get = mntns_get, | |
3344 | .put = mntns_put, | |
3345 | .install = mntns_install, | |
3346 | }; |