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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/slab.h> |
13 | #include <linux/sched.h> |
14 | #include <linux/spinlock.h> |
15 | #include <linux/percpu.h> |
16 | #include <linux/init.h> |
17 | #include <linux/kernel.h> |
18 | #include <linux/acct.h> |
19 | #include <linux/capability.h> |
20 | #include <linux/cpumask.h> |
21 | #include <linux/module.h> |
22 | #include <linux/sysfs.h> |
23 | #include <linux/seq_file.h> |
24 | #include <linux/mnt_namespace.h> |
25 | #include <linux/namei.h> |
26 | #include <linux/nsproxy.h> |
27 | #include <linux/security.h> |
28 | #include <linux/mount.h> |
29 | #include <linux/ramfs.h> |
30 | #include <linux/log2.h> |
31 | #include <linux/idr.h> |
32 | #include <linux/fs_struct.h> |
33 | #include <linux/fsnotify.h> |
34 | #include <asm/uaccess.h> |
35 | #include <asm/unistd.h> |
36 | #include "pnode.h" |
37 | #include "internal.h" |
38 | |
39 | #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head)) |
40 | #define HASH_SIZE (1UL << HASH_SHIFT) |
41 | |
42 | static int event; |
43 | static DEFINE_IDA(mnt_id_ida); |
44 | static DEFINE_IDA(mnt_group_ida); |
45 | static DEFINE_SPINLOCK(mnt_id_lock); |
46 | static int mnt_id_start = 0; |
47 | static int mnt_group_start = 1; |
48 | |
49 | static struct list_head *mount_hashtable __read_mostly; |
50 | static struct kmem_cache *mnt_cache __read_mostly; |
51 | static struct rw_semaphore namespace_sem; |
52 | |
53 | /* /sys/fs */ |
54 | struct kobject *fs_kobj; |
55 | EXPORT_SYMBOL_GPL(fs_kobj); |
56 | |
57 | /* |
58 | * vfsmount lock may be taken for read to prevent changes to the |
59 | * vfsmount hash, ie. during mountpoint lookups or walking back |
60 | * up the tree. |
61 | * |
62 | * It should be taken for write in all cases where the vfsmount |
63 | * tree or hash is modified or when a vfsmount structure is modified. |
64 | */ |
65 | DEFINE_BRLOCK(vfsmount_lock); |
66 | |
67 | static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) |
68 | { |
69 | unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); |
70 | tmp += ((unsigned long)dentry / L1_CACHE_BYTES); |
71 | tmp = tmp + (tmp >> HASH_SHIFT); |
72 | return tmp & (HASH_SIZE - 1); |
73 | } |
74 | |
75 | #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16) |
76 | |
77 | /* |
78 | * allocation is serialized by namespace_sem, but we need the spinlock to |
79 | * serialize with freeing. |
80 | */ |
81 | static int mnt_alloc_id(struct vfsmount *mnt) |
82 | { |
83 | int res; |
84 | |
85 | retry: |
86 | ida_pre_get(&mnt_id_ida, GFP_KERNEL); |
87 | spin_lock(&mnt_id_lock); |
88 | res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id); |
89 | if (!res) |
90 | mnt_id_start = mnt->mnt_id + 1; |
91 | spin_unlock(&mnt_id_lock); |
92 | if (res == -EAGAIN) |
93 | goto retry; |
94 | |
95 | return res; |
96 | } |
97 | |
98 | static void mnt_free_id(struct vfsmount *mnt) |
99 | { |
100 | int id = mnt->mnt_id; |
101 | spin_lock(&mnt_id_lock); |
102 | ida_remove(&mnt_id_ida, id); |
103 | if (mnt_id_start > id) |
104 | mnt_id_start = id; |
105 | spin_unlock(&mnt_id_lock); |
106 | } |
107 | |
108 | /* |
109 | * Allocate a new peer group ID |
110 | * |
111 | * mnt_group_ida is protected by namespace_sem |
112 | */ |
113 | static int mnt_alloc_group_id(struct vfsmount *mnt) |
114 | { |
115 | int res; |
116 | |
117 | if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL)) |
118 | return -ENOMEM; |
119 | |
120 | res = ida_get_new_above(&mnt_group_ida, |
121 | mnt_group_start, |
122 | &mnt->mnt_group_id); |
123 | if (!res) |
124 | mnt_group_start = mnt->mnt_group_id + 1; |
125 | |
126 | return res; |
127 | } |
128 | |
129 | /* |
130 | * Release a peer group ID |
131 | */ |
132 | void mnt_release_group_id(struct vfsmount *mnt) |
133 | { |
134 | int id = mnt->mnt_group_id; |
135 | ida_remove(&mnt_group_ida, id); |
136 | if (mnt_group_start > id) |
137 | mnt_group_start = id; |
138 | mnt->mnt_group_id = 0; |
139 | } |
140 | |
141 | /* |
142 | * vfsmount lock must be held for read |
143 | */ |
144 | static inline void mnt_add_count(struct vfsmount *mnt, int n) |
145 | { |
146 | #ifdef CONFIG_SMP |
147 | this_cpu_add(mnt->mnt_pcp->mnt_count, n); |
148 | #else |
149 | preempt_disable(); |
150 | mnt->mnt_count += n; |
151 | preempt_enable(); |
152 | #endif |
153 | } |
154 | |
155 | static inline void mnt_set_count(struct vfsmount *mnt, int n) |
156 | { |
157 | #ifdef CONFIG_SMP |
158 | this_cpu_write(mnt->mnt_pcp->mnt_count, n); |
159 | #else |
160 | mnt->mnt_count = n; |
161 | #endif |
162 | } |
163 | |
164 | /* |
165 | * vfsmount lock must be held for read |
166 | */ |
167 | static inline void mnt_inc_count(struct vfsmount *mnt) |
168 | { |
169 | mnt_add_count(mnt, 1); |
170 | } |
171 | |
172 | /* |
173 | * vfsmount lock must be held for read |
174 | */ |
175 | static inline void mnt_dec_count(struct vfsmount *mnt) |
176 | { |
177 | mnt_add_count(mnt, -1); |
178 | } |
179 | |
180 | /* |
181 | * vfsmount lock must be held for write |
182 | */ |
183 | unsigned int mnt_get_count(struct vfsmount *mnt) |
184 | { |
185 | #ifdef CONFIG_SMP |
186 | unsigned int count = 0; |
187 | int cpu; |
188 | |
189 | for_each_possible_cpu(cpu) { |
190 | count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count; |
191 | } |
192 | |
193 | return count; |
194 | #else |
195 | return mnt->mnt_count; |
196 | #endif |
197 | } |
198 | |
199 | static struct vfsmount *alloc_vfsmnt(const char *name) |
200 | { |
201 | struct vfsmount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); |
202 | if (mnt) { |
203 | int err; |
204 | |
205 | err = mnt_alloc_id(mnt); |
206 | if (err) |
207 | goto out_free_cache; |
208 | |
209 | if (name) { |
210 | mnt->mnt_devname = kstrdup(name, GFP_KERNEL); |
211 | if (!mnt->mnt_devname) |
212 | goto out_free_id; |
213 | } |
214 | |
215 | #ifdef CONFIG_SMP |
216 | mnt->mnt_pcp = alloc_percpu(struct mnt_pcp); |
217 | if (!mnt->mnt_pcp) |
218 | goto out_free_devname; |
219 | |
220 | this_cpu_add(mnt->mnt_pcp->mnt_count, 1); |
221 | #else |
222 | mnt->mnt_count = 1; |
223 | mnt->mnt_writers = 0; |
224 | #endif |
225 | |
226 | INIT_LIST_HEAD(&mnt->mnt_hash); |
227 | INIT_LIST_HEAD(&mnt->mnt_child); |
228 | INIT_LIST_HEAD(&mnt->mnt_mounts); |
229 | INIT_LIST_HEAD(&mnt->mnt_list); |
230 | INIT_LIST_HEAD(&mnt->mnt_expire); |
231 | INIT_LIST_HEAD(&mnt->mnt_share); |
232 | INIT_LIST_HEAD(&mnt->mnt_slave_list); |
233 | INIT_LIST_HEAD(&mnt->mnt_slave); |
234 | #ifdef CONFIG_FSNOTIFY |
235 | INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks); |
236 | #endif |
237 | } |
238 | return mnt; |
239 | |
240 | #ifdef CONFIG_SMP |
241 | out_free_devname: |
242 | kfree(mnt->mnt_devname); |
243 | #endif |
244 | out_free_id: |
245 | mnt_free_id(mnt); |
246 | out_free_cache: |
247 | kmem_cache_free(mnt_cache, mnt); |
248 | return NULL; |
249 | } |
250 | |
251 | /* |
252 | * Most r/o checks on a fs are for operations that take |
253 | * discrete amounts of time, like a write() or unlink(). |
254 | * We must keep track of when those operations start |
255 | * (for permission checks) and when they end, so that |
256 | * we can determine when writes are able to occur to |
257 | * a filesystem. |
258 | */ |
259 | /* |
260 | * __mnt_is_readonly: check whether a mount is read-only |
261 | * @mnt: the mount to check for its write status |
262 | * |
263 | * This shouldn't be used directly ouside of the VFS. |
264 | * It does not guarantee that the filesystem will stay |
265 | * r/w, just that it is right *now*. This can not and |
266 | * should not be used in place of IS_RDONLY(inode). |
267 | * mnt_want/drop_write() will _keep_ the filesystem |
268 | * r/w. |
269 | */ |
270 | int __mnt_is_readonly(struct vfsmount *mnt) |
271 | { |
272 | if (mnt->mnt_flags & MNT_READONLY) |
273 | return 1; |
274 | if (mnt->mnt_sb->s_flags & MS_RDONLY) |
275 | return 1; |
276 | return 0; |
277 | } |
278 | EXPORT_SYMBOL_GPL(__mnt_is_readonly); |
279 | |
280 | static inline void mnt_inc_writers(struct vfsmount *mnt) |
281 | { |
282 | #ifdef CONFIG_SMP |
283 | this_cpu_inc(mnt->mnt_pcp->mnt_writers); |
284 | #else |
285 | mnt->mnt_writers++; |
286 | #endif |
287 | } |
288 | |
289 | static inline void mnt_dec_writers(struct vfsmount *mnt) |
290 | { |
291 | #ifdef CONFIG_SMP |
292 | this_cpu_dec(mnt->mnt_pcp->mnt_writers); |
293 | #else |
294 | mnt->mnt_writers--; |
295 | #endif |
296 | } |
297 | |
298 | static unsigned int mnt_get_writers(struct vfsmount *mnt) |
299 | { |
300 | #ifdef CONFIG_SMP |
301 | unsigned int count = 0; |
302 | int cpu; |
303 | |
304 | for_each_possible_cpu(cpu) { |
305 | count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers; |
306 | } |
307 | |
308 | return count; |
309 | #else |
310 | return mnt->mnt_writers; |
311 | #endif |
312 | } |
313 | |
314 | /* |
315 | * Most r/o checks on a fs are for operations that take |
316 | * discrete amounts of time, like a write() or unlink(). |
317 | * We must keep track of when those operations start |
318 | * (for permission checks) and when they end, so that |
319 | * we can determine when writes are able to occur to |
320 | * a filesystem. |
321 | */ |
322 | /** |
323 | * mnt_want_write - get write access to a mount |
324 | * @mnt: the mount on which to take a write |
325 | * |
326 | * This tells the low-level filesystem that a write is |
327 | * about to be performed to it, and makes sure that |
328 | * writes are allowed before returning success. When |
329 | * the write operation is finished, mnt_drop_write() |
330 | * must be called. This is effectively a refcount. |
331 | */ |
332 | int mnt_want_write(struct vfsmount *mnt) |
333 | { |
334 | int ret = 0; |
335 | |
336 | preempt_disable(); |
337 | mnt_inc_writers(mnt); |
338 | /* |
339 | * The store to mnt_inc_writers must be visible before we pass |
340 | * MNT_WRITE_HOLD loop below, so that the slowpath can see our |
341 | * incremented count after it has set MNT_WRITE_HOLD. |
342 | */ |
343 | smp_mb(); |
344 | while (mnt->mnt_flags & MNT_WRITE_HOLD) |
345 | cpu_relax(); |
346 | /* |
347 | * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will |
348 | * be set to match its requirements. So we must not load that until |
349 | * MNT_WRITE_HOLD is cleared. |
350 | */ |
351 | smp_rmb(); |
352 | if (__mnt_is_readonly(mnt)) { |
353 | mnt_dec_writers(mnt); |
354 | ret = -EROFS; |
355 | goto out; |
356 | } |
357 | out: |
358 | preempt_enable(); |
359 | return ret; |
360 | } |
361 | EXPORT_SYMBOL_GPL(mnt_want_write); |
362 | |
363 | /** |
364 | * mnt_clone_write - get write access to a mount |
365 | * @mnt: the mount on which to take a write |
366 | * |
367 | * This is effectively like mnt_want_write, except |
368 | * it must only be used to take an extra write reference |
369 | * on a mountpoint that we already know has a write reference |
370 | * on it. This allows some optimisation. |
371 | * |
372 | * After finished, mnt_drop_write must be called as usual to |
373 | * drop the reference. |
374 | */ |
375 | int mnt_clone_write(struct vfsmount *mnt) |
376 | { |
377 | /* superblock may be r/o */ |
378 | if (__mnt_is_readonly(mnt)) |
379 | return -EROFS; |
380 | preempt_disable(); |
381 | mnt_inc_writers(mnt); |
382 | preempt_enable(); |
383 | return 0; |
384 | } |
385 | EXPORT_SYMBOL_GPL(mnt_clone_write); |
386 | |
387 | /** |
388 | * mnt_want_write_file - get write access to a file's mount |
389 | * @file: the file who's mount on which to take a write |
390 | * |
391 | * This is like mnt_want_write, but it takes a file and can |
392 | * do some optimisations if the file is open for write already |
393 | */ |
394 | int mnt_want_write_file(struct file *file) |
395 | { |
396 | struct inode *inode = file->f_dentry->d_inode; |
397 | if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode)) |
398 | return mnt_want_write(file->f_path.mnt); |
399 | else |
400 | return mnt_clone_write(file->f_path.mnt); |
401 | } |
402 | EXPORT_SYMBOL_GPL(mnt_want_write_file); |
403 | |
404 | /** |
405 | * mnt_drop_write - give up write access to a mount |
406 | * @mnt: the mount on which to give up write access |
407 | * |
408 | * Tells the low-level filesystem that we are done |
409 | * performing writes to it. Must be matched with |
410 | * mnt_want_write() call above. |
411 | */ |
412 | void mnt_drop_write(struct vfsmount *mnt) |
413 | { |
414 | preempt_disable(); |
415 | mnt_dec_writers(mnt); |
416 | preempt_enable(); |
417 | } |
418 | EXPORT_SYMBOL_GPL(mnt_drop_write); |
419 | |
420 | static int mnt_make_readonly(struct vfsmount *mnt) |
421 | { |
422 | int ret = 0; |
423 | |
424 | br_write_lock(vfsmount_lock); |
425 | mnt->mnt_flags |= MNT_WRITE_HOLD; |
426 | /* |
427 | * After storing MNT_WRITE_HOLD, we'll read the counters. This store |
428 | * should be visible before we do. |
429 | */ |
430 | smp_mb(); |
431 | |
432 | /* |
433 | * With writers on hold, if this value is zero, then there are |
434 | * definitely no active writers (although held writers may subsequently |
435 | * increment the count, they'll have to wait, and decrement it after |
436 | * seeing MNT_READONLY). |
437 | * |
438 | * It is OK to have counter incremented on one CPU and decremented on |
439 | * another: the sum will add up correctly. The danger would be when we |
440 | * sum up each counter, if we read a counter before it is incremented, |
441 | * but then read another CPU's count which it has been subsequently |
442 | * decremented from -- we would see more decrements than we should. |
443 | * MNT_WRITE_HOLD protects against this scenario, because |
444 | * mnt_want_write first increments count, then smp_mb, then spins on |
445 | * MNT_WRITE_HOLD, so it can't be decremented by another CPU while |
446 | * we're counting up here. |
447 | */ |
448 | if (mnt_get_writers(mnt) > 0) |
449 | ret = -EBUSY; |
450 | else |
451 | mnt->mnt_flags |= MNT_READONLY; |
452 | /* |
453 | * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers |
454 | * that become unheld will see MNT_READONLY. |
455 | */ |
456 | smp_wmb(); |
457 | mnt->mnt_flags &= ~MNT_WRITE_HOLD; |
458 | br_write_unlock(vfsmount_lock); |
459 | return ret; |
460 | } |
461 | |
462 | static void __mnt_unmake_readonly(struct vfsmount *mnt) |
463 | { |
464 | br_write_lock(vfsmount_lock); |
465 | mnt->mnt_flags &= ~MNT_READONLY; |
466 | br_write_unlock(vfsmount_lock); |
467 | } |
468 | |
469 | static void free_vfsmnt(struct vfsmount *mnt) |
470 | { |
471 | kfree(mnt->mnt_devname); |
472 | mnt_free_id(mnt); |
473 | #ifdef CONFIG_SMP |
474 | free_percpu(mnt->mnt_pcp); |
475 | #endif |
476 | kmem_cache_free(mnt_cache, mnt); |
477 | } |
478 | |
479 | /* |
480 | * find the first or last mount at @dentry on vfsmount @mnt depending on |
481 | * @dir. If @dir is set return the first mount else return the last mount. |
482 | * vfsmount_lock must be held for read or write. |
483 | */ |
484 | struct vfsmount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry, |
485 | int dir) |
486 | { |
487 | struct list_head *head = mount_hashtable + hash(mnt, dentry); |
488 | struct list_head *tmp = head; |
489 | struct vfsmount *p, *found = NULL; |
490 | |
491 | for (;;) { |
492 | tmp = dir ? tmp->next : tmp->prev; |
493 | p = NULL; |
494 | if (tmp == head) |
495 | break; |
496 | p = list_entry(tmp, struct vfsmount, mnt_hash); |
497 | if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) { |
498 | found = p; |
499 | break; |
500 | } |
501 | } |
502 | return found; |
503 | } |
504 | |
505 | /* |
506 | * lookup_mnt increments the ref count before returning |
507 | * the vfsmount struct. |
508 | */ |
509 | struct vfsmount *lookup_mnt(struct path *path) |
510 | { |
511 | struct vfsmount *child_mnt; |
512 | |
513 | br_read_lock(vfsmount_lock); |
514 | if ((child_mnt = __lookup_mnt(path->mnt, path->dentry, 1))) |
515 | mntget(child_mnt); |
516 | br_read_unlock(vfsmount_lock); |
517 | return child_mnt; |
518 | } |
519 | |
520 | static inline int check_mnt(struct vfsmount *mnt) |
521 | { |
522 | return mnt->mnt_ns == current->nsproxy->mnt_ns; |
523 | } |
524 | |
525 | /* |
526 | * vfsmount lock must be held for write |
527 | */ |
528 | static void touch_mnt_namespace(struct mnt_namespace *ns) |
529 | { |
530 | if (ns) { |
531 | ns->event = ++event; |
532 | wake_up_interruptible(&ns->poll); |
533 | } |
534 | } |
535 | |
536 | /* |
537 | * vfsmount lock must be held for write |
538 | */ |
539 | static void __touch_mnt_namespace(struct mnt_namespace *ns) |
540 | { |
541 | if (ns && ns->event != event) { |
542 | ns->event = event; |
543 | wake_up_interruptible(&ns->poll); |
544 | } |
545 | } |
546 | |
547 | /* |
548 | * Clear dentry's mounted state if it has no remaining mounts. |
549 | * vfsmount_lock must be held for write. |
550 | */ |
551 | static void dentry_reset_mounted(struct vfsmount *mnt, struct dentry *dentry) |
552 | { |
553 | unsigned u; |
554 | |
555 | for (u = 0; u < HASH_SIZE; u++) { |
556 | struct vfsmount *p; |
557 | |
558 | list_for_each_entry(p, &mount_hashtable[u], mnt_hash) { |
559 | if (p->mnt_mountpoint == dentry) |
560 | return; |
561 | } |
562 | } |
563 | spin_lock(&dentry->d_lock); |
564 | dentry->d_flags &= ~DCACHE_MOUNTED; |
565 | spin_unlock(&dentry->d_lock); |
566 | } |
567 | |
568 | /* |
569 | * vfsmount lock must be held for write |
570 | */ |
571 | static void detach_mnt(struct vfsmount *mnt, struct path *old_path) |
572 | { |
573 | old_path->dentry = mnt->mnt_mountpoint; |
574 | old_path->mnt = mnt->mnt_parent; |
575 | mnt->mnt_parent = mnt; |
576 | mnt->mnt_mountpoint = mnt->mnt_root; |
577 | list_del_init(&mnt->mnt_child); |
578 | list_del_init(&mnt->mnt_hash); |
579 | dentry_reset_mounted(old_path->mnt, old_path->dentry); |
580 | } |
581 | |
582 | /* |
583 | * vfsmount lock must be held for write |
584 | */ |
585 | void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry, |
586 | struct vfsmount *child_mnt) |
587 | { |
588 | child_mnt->mnt_parent = mntget(mnt); |
589 | child_mnt->mnt_mountpoint = dget(dentry); |
590 | spin_lock(&dentry->d_lock); |
591 | dentry->d_flags |= DCACHE_MOUNTED; |
592 | spin_unlock(&dentry->d_lock); |
593 | } |
594 | |
595 | /* |
596 | * vfsmount lock must be held for write |
597 | */ |
598 | static void attach_mnt(struct vfsmount *mnt, struct path *path) |
599 | { |
600 | mnt_set_mountpoint(path->mnt, path->dentry, mnt); |
601 | list_add_tail(&mnt->mnt_hash, mount_hashtable + |
602 | hash(path->mnt, path->dentry)); |
603 | list_add_tail(&mnt->mnt_child, &path->mnt->mnt_mounts); |
604 | } |
605 | |
606 | static inline void __mnt_make_longterm(struct vfsmount *mnt) |
607 | { |
608 | #ifdef CONFIG_SMP |
609 | atomic_inc(&mnt->mnt_longterm); |
610 | #endif |
611 | } |
612 | |
613 | /* needs vfsmount lock for write */ |
614 | static inline void __mnt_make_shortterm(struct vfsmount *mnt) |
615 | { |
616 | #ifdef CONFIG_SMP |
617 | atomic_dec(&mnt->mnt_longterm); |
618 | #endif |
619 | } |
620 | |
621 | /* |
622 | * vfsmount lock must be held for write |
623 | */ |
624 | static void commit_tree(struct vfsmount *mnt) |
625 | { |
626 | struct vfsmount *parent = mnt->mnt_parent; |
627 | struct vfsmount *m; |
628 | LIST_HEAD(head); |
629 | struct mnt_namespace *n = parent->mnt_ns; |
630 | |
631 | BUG_ON(parent == mnt); |
632 | |
633 | list_add_tail(&head, &mnt->mnt_list); |
634 | list_for_each_entry(m, &head, mnt_list) { |
635 | m->mnt_ns = n; |
636 | __mnt_make_longterm(m); |
637 | } |
638 | |
639 | list_splice(&head, n->list.prev); |
640 | |
641 | list_add_tail(&mnt->mnt_hash, mount_hashtable + |
642 | hash(parent, mnt->mnt_mountpoint)); |
643 | list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); |
644 | touch_mnt_namespace(n); |
645 | } |
646 | |
647 | static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *root) |
648 | { |
649 | struct list_head *next = p->mnt_mounts.next; |
650 | if (next == &p->mnt_mounts) { |
651 | while (1) { |
652 | if (p == root) |
653 | return NULL; |
654 | next = p->mnt_child.next; |
655 | if (next != &p->mnt_parent->mnt_mounts) |
656 | break; |
657 | p = p->mnt_parent; |
658 | } |
659 | } |
660 | return list_entry(next, struct vfsmount, mnt_child); |
661 | } |
662 | |
663 | static struct vfsmount *skip_mnt_tree(struct vfsmount *p) |
664 | { |
665 | struct list_head *prev = p->mnt_mounts.prev; |
666 | while (prev != &p->mnt_mounts) { |
667 | p = list_entry(prev, struct vfsmount, mnt_child); |
668 | prev = p->mnt_mounts.prev; |
669 | } |
670 | return p; |
671 | } |
672 | |
673 | struct vfsmount * |
674 | vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data) |
675 | { |
676 | struct vfsmount *mnt; |
677 | struct dentry *root; |
678 | |
679 | if (!type) |
680 | return ERR_PTR(-ENODEV); |
681 | |
682 | mnt = alloc_vfsmnt(name); |
683 | if (!mnt) |
684 | return ERR_PTR(-ENOMEM); |
685 | |
686 | if (flags & MS_KERNMOUNT) |
687 | mnt->mnt_flags = MNT_INTERNAL; |
688 | |
689 | root = mount_fs(type, flags, name, data); |
690 | if (IS_ERR(root)) { |
691 | free_vfsmnt(mnt); |
692 | return ERR_CAST(root); |
693 | } |
694 | |
695 | mnt->mnt_root = root; |
696 | mnt->mnt_sb = root->d_sb; |
697 | mnt->mnt_mountpoint = mnt->mnt_root; |
698 | mnt->mnt_parent = mnt; |
699 | return mnt; |
700 | } |
701 | EXPORT_SYMBOL_GPL(vfs_kern_mount); |
702 | |
703 | static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root, |
704 | int flag) |
705 | { |
706 | struct super_block *sb = old->mnt_sb; |
707 | struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname); |
708 | |
709 | if (mnt) { |
710 | if (flag & (CL_SLAVE | CL_PRIVATE)) |
711 | mnt->mnt_group_id = 0; /* not a peer of original */ |
712 | else |
713 | mnt->mnt_group_id = old->mnt_group_id; |
714 | |
715 | if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { |
716 | int err = mnt_alloc_group_id(mnt); |
717 | if (err) |
718 | goto out_free; |
719 | } |
720 | |
721 | mnt->mnt_flags = old->mnt_flags & ~MNT_WRITE_HOLD; |
722 | atomic_inc(&sb->s_active); |
723 | mnt->mnt_sb = sb; |
724 | mnt->mnt_root = dget(root); |
725 | mnt->mnt_mountpoint = mnt->mnt_root; |
726 | mnt->mnt_parent = mnt; |
727 | |
728 | if (flag & CL_SLAVE) { |
729 | list_add(&mnt->mnt_slave, &old->mnt_slave_list); |
730 | mnt->mnt_master = old; |
731 | CLEAR_MNT_SHARED(mnt); |
732 | } else if (!(flag & CL_PRIVATE)) { |
733 | if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old)) |
734 | list_add(&mnt->mnt_share, &old->mnt_share); |
735 | if (IS_MNT_SLAVE(old)) |
736 | list_add(&mnt->mnt_slave, &old->mnt_slave); |
737 | mnt->mnt_master = old->mnt_master; |
738 | } |
739 | if (flag & CL_MAKE_SHARED) |
740 | set_mnt_shared(mnt); |
741 | |
742 | /* stick the duplicate mount on the same expiry list |
743 | * as the original if that was on one */ |
744 | if (flag & CL_EXPIRE) { |
745 | if (!list_empty(&old->mnt_expire)) |
746 | list_add(&mnt->mnt_expire, &old->mnt_expire); |
747 | } |
748 | } |
749 | return mnt; |
750 | |
751 | out_free: |
752 | free_vfsmnt(mnt); |
753 | return NULL; |
754 | } |
755 | |
756 | static inline void mntfree(struct vfsmount *mnt) |
757 | { |
758 | struct super_block *sb = mnt->mnt_sb; |
759 | |
760 | /* |
761 | * This probably indicates that somebody messed |
762 | * up a mnt_want/drop_write() pair. If this |
763 | * happens, the filesystem was probably unable |
764 | * to make r/w->r/o transitions. |
765 | */ |
766 | /* |
767 | * The locking used to deal with mnt_count decrement provides barriers, |
768 | * so mnt_get_writers() below is safe. |
769 | */ |
770 | WARN_ON(mnt_get_writers(mnt)); |
771 | fsnotify_vfsmount_delete(mnt); |
772 | dput(mnt->mnt_root); |
773 | free_vfsmnt(mnt); |
774 | deactivate_super(sb); |
775 | } |
776 | |
777 | static void mntput_no_expire(struct vfsmount *mnt) |
778 | { |
779 | put_again: |
780 | #ifdef CONFIG_SMP |
781 | br_read_lock(vfsmount_lock); |
782 | if (likely(atomic_read(&mnt->mnt_longterm))) { |
783 | mnt_dec_count(mnt); |
784 | br_read_unlock(vfsmount_lock); |
785 | return; |
786 | } |
787 | br_read_unlock(vfsmount_lock); |
788 | |
789 | br_write_lock(vfsmount_lock); |
790 | mnt_dec_count(mnt); |
791 | if (mnt_get_count(mnt)) { |
792 | br_write_unlock(vfsmount_lock); |
793 | return; |
794 | } |
795 | #else |
796 | mnt_dec_count(mnt); |
797 | if (likely(mnt_get_count(mnt))) |
798 | return; |
799 | br_write_lock(vfsmount_lock); |
800 | #endif |
801 | if (unlikely(mnt->mnt_pinned)) { |
802 | mnt_add_count(mnt, mnt->mnt_pinned + 1); |
803 | mnt->mnt_pinned = 0; |
804 | br_write_unlock(vfsmount_lock); |
805 | acct_auto_close_mnt(mnt); |
806 | goto put_again; |
807 | } |
808 | br_write_unlock(vfsmount_lock); |
809 | mntfree(mnt); |
810 | } |
811 | |
812 | void mntput(struct vfsmount *mnt) |
813 | { |
814 | if (mnt) { |
815 | /* avoid cacheline pingpong, hope gcc doesn't get "smart" */ |
816 | if (unlikely(mnt->mnt_expiry_mark)) |
817 | mnt->mnt_expiry_mark = 0; |
818 | mntput_no_expire(mnt); |
819 | } |
820 | } |
821 | EXPORT_SYMBOL(mntput); |
822 | |
823 | struct vfsmount *mntget(struct vfsmount *mnt) |
824 | { |
825 | if (mnt) |
826 | mnt_inc_count(mnt); |
827 | return mnt; |
828 | } |
829 | EXPORT_SYMBOL(mntget); |
830 | |
831 | void mnt_pin(struct vfsmount *mnt) |
832 | { |
833 | br_write_lock(vfsmount_lock); |
834 | mnt->mnt_pinned++; |
835 | br_write_unlock(vfsmount_lock); |
836 | } |
837 | EXPORT_SYMBOL(mnt_pin); |
838 | |
839 | void mnt_unpin(struct vfsmount *mnt) |
840 | { |
841 | br_write_lock(vfsmount_lock); |
842 | if (mnt->mnt_pinned) { |
843 | mnt_inc_count(mnt); |
844 | mnt->mnt_pinned--; |
845 | } |
846 | br_write_unlock(vfsmount_lock); |
847 | } |
848 | EXPORT_SYMBOL(mnt_unpin); |
849 | |
850 | static inline void mangle(struct seq_file *m, const char *s) |
851 | { |
852 | seq_escape(m, s, " \t\n\\"); |
853 | } |
854 | |
855 | /* |
856 | * Simple .show_options callback for filesystems which don't want to |
857 | * implement more complex mount option showing. |
858 | * |
859 | * See also save_mount_options(). |
860 | */ |
861 | int generic_show_options(struct seq_file *m, struct vfsmount *mnt) |
862 | { |
863 | const char *options; |
864 | |
865 | rcu_read_lock(); |
866 | options = rcu_dereference(mnt->mnt_sb->s_options); |
867 | |
868 | if (options != NULL && options[0]) { |
869 | seq_putc(m, ','); |
870 | mangle(m, options); |
871 | } |
872 | rcu_read_unlock(); |
873 | |
874 | return 0; |
875 | } |
876 | EXPORT_SYMBOL(generic_show_options); |
877 | |
878 | /* |
879 | * If filesystem uses generic_show_options(), this function should be |
880 | * called from the fill_super() callback. |
881 | * |
882 | * The .remount_fs callback usually needs to be handled in a special |
883 | * way, to make sure, that previous options are not overwritten if the |
884 | * remount fails. |
885 | * |
886 | * Also note, that if the filesystem's .remount_fs function doesn't |
887 | * reset all options to their default value, but changes only newly |
888 | * given options, then the displayed options will not reflect reality |
889 | * any more. |
890 | */ |
891 | void save_mount_options(struct super_block *sb, char *options) |
892 | { |
893 | BUG_ON(sb->s_options); |
894 | rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL)); |
895 | } |
896 | EXPORT_SYMBOL(save_mount_options); |
897 | |
898 | void replace_mount_options(struct super_block *sb, char *options) |
899 | { |
900 | char *old = sb->s_options; |
901 | rcu_assign_pointer(sb->s_options, options); |
902 | if (old) { |
903 | synchronize_rcu(); |
904 | kfree(old); |
905 | } |
906 | } |
907 | EXPORT_SYMBOL(replace_mount_options); |
908 | |
909 | #ifdef CONFIG_PROC_FS |
910 | /* iterator */ |
911 | static void *m_start(struct seq_file *m, loff_t *pos) |
912 | { |
913 | struct proc_mounts *p = m->private; |
914 | |
915 | down_read(&namespace_sem); |
916 | return seq_list_start(&p->ns->list, *pos); |
917 | } |
918 | |
919 | static void *m_next(struct seq_file *m, void *v, loff_t *pos) |
920 | { |
921 | struct proc_mounts *p = m->private; |
922 | |
923 | return seq_list_next(v, &p->ns->list, pos); |
924 | } |
925 | |
926 | static void m_stop(struct seq_file *m, void *v) |
927 | { |
928 | up_read(&namespace_sem); |
929 | } |
930 | |
931 | int mnt_had_events(struct proc_mounts *p) |
932 | { |
933 | struct mnt_namespace *ns = p->ns; |
934 | int res = 0; |
935 | |
936 | br_read_lock(vfsmount_lock); |
937 | if (p->event != ns->event) { |
938 | p->event = ns->event; |
939 | res = 1; |
940 | } |
941 | br_read_unlock(vfsmount_lock); |
942 | |
943 | return res; |
944 | } |
945 | |
946 | struct proc_fs_info { |
947 | int flag; |
948 | const char *str; |
949 | }; |
950 | |
951 | static int show_sb_opts(struct seq_file *m, struct super_block *sb) |
952 | { |
953 | static const struct proc_fs_info fs_info[] = { |
954 | { MS_SYNCHRONOUS, ",sync" }, |
955 | { MS_DIRSYNC, ",dirsync" }, |
956 | { MS_MANDLOCK, ",mand" }, |
957 | { 0, NULL } |
958 | }; |
959 | const struct proc_fs_info *fs_infop; |
960 | |
961 | for (fs_infop = fs_info; fs_infop->flag; fs_infop++) { |
962 | if (sb->s_flags & fs_infop->flag) |
963 | seq_puts(m, fs_infop->str); |
964 | } |
965 | |
966 | return security_sb_show_options(m, sb); |
967 | } |
968 | |
969 | static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt) |
970 | { |
971 | static const struct proc_fs_info mnt_info[] = { |
972 | { MNT_NOSUID, ",nosuid" }, |
973 | { MNT_NODEV, ",nodev" }, |
974 | { MNT_NOEXEC, ",noexec" }, |
975 | { MNT_NOATIME, ",noatime" }, |
976 | { MNT_NODIRATIME, ",nodiratime" }, |
977 | { MNT_RELATIME, ",relatime" }, |
978 | { 0, NULL } |
979 | }; |
980 | const struct proc_fs_info *fs_infop; |
981 | |
982 | for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) { |
983 | if (mnt->mnt_flags & fs_infop->flag) |
984 | seq_puts(m, fs_infop->str); |
985 | } |
986 | } |
987 | |
988 | static void show_type(struct seq_file *m, struct super_block *sb) |
989 | { |
990 | mangle(m, sb->s_type->name); |
991 | if (sb->s_subtype && sb->s_subtype[0]) { |
992 | seq_putc(m, '.'); |
993 | mangle(m, sb->s_subtype); |
994 | } |
995 | } |
996 | |
997 | static int show_vfsmnt(struct seq_file *m, void *v) |
998 | { |
999 | struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); |
1000 | int err = 0; |
1001 | struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt }; |
1002 | |
1003 | if (mnt->mnt_sb->s_op->show_devname) { |
1004 | err = mnt->mnt_sb->s_op->show_devname(m, mnt); |
1005 | if (err) |
1006 | goto out; |
1007 | } else { |
1008 | mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none"); |
1009 | } |
1010 | seq_putc(m, ' '); |
1011 | seq_path(m, &mnt_path, " \t\n\\"); |
1012 | seq_putc(m, ' '); |
1013 | show_type(m, mnt->mnt_sb); |
1014 | seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw"); |
1015 | err = show_sb_opts(m, mnt->mnt_sb); |
1016 | if (err) |
1017 | goto out; |
1018 | show_mnt_opts(m, mnt); |
1019 | if (mnt->mnt_sb->s_op->show_options) |
1020 | err = mnt->mnt_sb->s_op->show_options(m, mnt); |
1021 | seq_puts(m, " 0 0\n"); |
1022 | out: |
1023 | return err; |
1024 | } |
1025 | |
1026 | const struct seq_operations mounts_op = { |
1027 | .start = m_start, |
1028 | .next = m_next, |
1029 | .stop = m_stop, |
1030 | .show = show_vfsmnt |
1031 | }; |
1032 | |
1033 | static int show_mountinfo(struct seq_file *m, void *v) |
1034 | { |
1035 | struct proc_mounts *p = m->private; |
1036 | struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); |
1037 | struct super_block *sb = mnt->mnt_sb; |
1038 | struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt }; |
1039 | struct path root = p->root; |
1040 | int err = 0; |
1041 | |
1042 | seq_printf(m, "%i %i %u:%u ", mnt->mnt_id, mnt->mnt_parent->mnt_id, |
1043 | MAJOR(sb->s_dev), MINOR(sb->s_dev)); |
1044 | if (sb->s_op->show_path) |
1045 | err = sb->s_op->show_path(m, mnt); |
1046 | else |
1047 | seq_dentry(m, mnt->mnt_root, " \t\n\\"); |
1048 | if (err) |
1049 | goto out; |
1050 | seq_putc(m, ' '); |
1051 | seq_path_root(m, &mnt_path, &root, " \t\n\\"); |
1052 | if (root.mnt != p->root.mnt || root.dentry != p->root.dentry) { |
1053 | /* |
1054 | * Mountpoint is outside root, discard that one. Ugly, |
1055 | * but less so than trying to do that in iterator in a |
1056 | * race-free way (due to renames). |
1057 | */ |
1058 | return SEQ_SKIP; |
1059 | } |
1060 | seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw"); |
1061 | show_mnt_opts(m, mnt); |
1062 | |
1063 | /* Tagged fields ("foo:X" or "bar") */ |
1064 | if (IS_MNT_SHARED(mnt)) |
1065 | seq_printf(m, " shared:%i", mnt->mnt_group_id); |
1066 | if (IS_MNT_SLAVE(mnt)) { |
1067 | int master = mnt->mnt_master->mnt_group_id; |
1068 | int dom = get_dominating_id(mnt, &p->root); |
1069 | seq_printf(m, " master:%i", master); |
1070 | if (dom && dom != master) |
1071 | seq_printf(m, " propagate_from:%i", dom); |
1072 | } |
1073 | if (IS_MNT_UNBINDABLE(mnt)) |
1074 | seq_puts(m, " unbindable"); |
1075 | |
1076 | /* Filesystem specific data */ |
1077 | seq_puts(m, " - "); |
1078 | show_type(m, sb); |
1079 | seq_putc(m, ' '); |
1080 | if (sb->s_op->show_devname) |
1081 | err = sb->s_op->show_devname(m, mnt); |
1082 | else |
1083 | mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none"); |
1084 | if (err) |
1085 | goto out; |
1086 | seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw"); |
1087 | err = show_sb_opts(m, sb); |
1088 | if (err) |
1089 | goto out; |
1090 | if (sb->s_op->show_options) |
1091 | err = sb->s_op->show_options(m, mnt); |
1092 | seq_putc(m, '\n'); |
1093 | out: |
1094 | return err; |
1095 | } |
1096 | |
1097 | const struct seq_operations mountinfo_op = { |
1098 | .start = m_start, |
1099 | .next = m_next, |
1100 | .stop = m_stop, |
1101 | .show = show_mountinfo, |
1102 | }; |
1103 | |
1104 | static int show_vfsstat(struct seq_file *m, void *v) |
1105 | { |
1106 | struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); |
1107 | struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt }; |
1108 | int err = 0; |
1109 | |
1110 | /* device */ |
1111 | if (mnt->mnt_sb->s_op->show_devname) { |
1112 | err = mnt->mnt_sb->s_op->show_devname(m, mnt); |
1113 | } else { |
1114 | if (mnt->mnt_devname) { |
1115 | seq_puts(m, "device "); |
1116 | mangle(m, mnt->mnt_devname); |
1117 | } else |
1118 | seq_puts(m, "no device"); |
1119 | } |
1120 | |
1121 | /* mount point */ |
1122 | seq_puts(m, " mounted on "); |
1123 | seq_path(m, &mnt_path, " \t\n\\"); |
1124 | seq_putc(m, ' '); |
1125 | |
1126 | /* file system type */ |
1127 | seq_puts(m, "with fstype "); |
1128 | show_type(m, mnt->mnt_sb); |
1129 | |
1130 | /* optional statistics */ |
1131 | if (mnt->mnt_sb->s_op->show_stats) { |
1132 | seq_putc(m, ' '); |
1133 | if (!err) |
1134 | err = mnt->mnt_sb->s_op->show_stats(m, mnt); |
1135 | } |
1136 | |
1137 | seq_putc(m, '\n'); |
1138 | return err; |
1139 | } |
1140 | |
1141 | const struct seq_operations mountstats_op = { |
1142 | .start = m_start, |
1143 | .next = m_next, |
1144 | .stop = m_stop, |
1145 | .show = show_vfsstat, |
1146 | }; |
1147 | #endif /* CONFIG_PROC_FS */ |
1148 | |
1149 | /** |
1150 | * may_umount_tree - check if a mount tree is busy |
1151 | * @mnt: root of mount tree |
1152 | * |
1153 | * This is called to check if a tree of mounts has any |
1154 | * open files, pwds, chroots or sub mounts that are |
1155 | * busy. |
1156 | */ |
1157 | int may_umount_tree(struct vfsmount *mnt) |
1158 | { |
1159 | int actual_refs = 0; |
1160 | int minimum_refs = 0; |
1161 | struct vfsmount *p; |
1162 | |
1163 | /* write lock needed for mnt_get_count */ |
1164 | br_write_lock(vfsmount_lock); |
1165 | for (p = mnt; p; p = next_mnt(p, mnt)) { |
1166 | actual_refs += mnt_get_count(p); |
1167 | minimum_refs += 2; |
1168 | } |
1169 | br_write_unlock(vfsmount_lock); |
1170 | |
1171 | if (actual_refs > minimum_refs) |
1172 | return 0; |
1173 | |
1174 | return 1; |
1175 | } |
1176 | |
1177 | EXPORT_SYMBOL(may_umount_tree); |
1178 | |
1179 | /** |
1180 | * may_umount - check if a mount point is busy |
1181 | * @mnt: root of mount |
1182 | * |
1183 | * This is called to check if a mount point has any |
1184 | * open files, pwds, chroots or sub mounts. If the |
1185 | * mount has sub mounts this will return busy |
1186 | * regardless of whether the sub mounts are busy. |
1187 | * |
1188 | * Doesn't take quota and stuff into account. IOW, in some cases it will |
1189 | * give false negatives. The main reason why it's here is that we need |
1190 | * a non-destructive way to look for easily umountable filesystems. |
1191 | */ |
1192 | int may_umount(struct vfsmount *mnt) |
1193 | { |
1194 | int ret = 1; |
1195 | down_read(&namespace_sem); |
1196 | br_write_lock(vfsmount_lock); |
1197 | if (propagate_mount_busy(mnt, 2)) |
1198 | ret = 0; |
1199 | br_write_unlock(vfsmount_lock); |
1200 | up_read(&namespace_sem); |
1201 | return ret; |
1202 | } |
1203 | |
1204 | EXPORT_SYMBOL(may_umount); |
1205 | |
1206 | void release_mounts(struct list_head *head) |
1207 | { |
1208 | struct vfsmount *mnt; |
1209 | while (!list_empty(head)) { |
1210 | mnt = list_first_entry(head, struct vfsmount, mnt_hash); |
1211 | list_del_init(&mnt->mnt_hash); |
1212 | if (mnt->mnt_parent != mnt) { |
1213 | struct dentry *dentry; |
1214 | struct vfsmount *m; |
1215 | |
1216 | br_write_lock(vfsmount_lock); |
1217 | dentry = mnt->mnt_mountpoint; |
1218 | m = mnt->mnt_parent; |
1219 | mnt->mnt_mountpoint = mnt->mnt_root; |
1220 | mnt->mnt_parent = mnt; |
1221 | m->mnt_ghosts--; |
1222 | br_write_unlock(vfsmount_lock); |
1223 | dput(dentry); |
1224 | mntput(m); |
1225 | } |
1226 | mntput(mnt); |
1227 | } |
1228 | } |
1229 | |
1230 | /* |
1231 | * vfsmount lock must be held for write |
1232 | * namespace_sem must be held for write |
1233 | */ |
1234 | void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill) |
1235 | { |
1236 | LIST_HEAD(tmp_list); |
1237 | struct vfsmount *p; |
1238 | |
1239 | for (p = mnt; p; p = next_mnt(p, mnt)) |
1240 | list_move(&p->mnt_hash, &tmp_list); |
1241 | |
1242 | if (propagate) |
1243 | propagate_umount(&tmp_list); |
1244 | |
1245 | list_for_each_entry(p, &tmp_list, mnt_hash) { |
1246 | list_del_init(&p->mnt_expire); |
1247 | list_del_init(&p->mnt_list); |
1248 | __touch_mnt_namespace(p->mnt_ns); |
1249 | p->mnt_ns = NULL; |
1250 | __mnt_make_shortterm(p); |
1251 | list_del_init(&p->mnt_child); |
1252 | if (p->mnt_parent != p) { |
1253 | p->mnt_parent->mnt_ghosts++; |
1254 | dentry_reset_mounted(p->mnt_parent, p->mnt_mountpoint); |
1255 | } |
1256 | change_mnt_propagation(p, MS_PRIVATE); |
1257 | } |
1258 | list_splice(&tmp_list, kill); |
1259 | } |
1260 | |
1261 | static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts); |
1262 | |
1263 | static int do_umount(struct vfsmount *mnt, int flags) |
1264 | { |
1265 | struct super_block *sb = mnt->mnt_sb; |
1266 | int retval; |
1267 | LIST_HEAD(umount_list); |
1268 | |
1269 | retval = security_sb_umount(mnt, flags); |
1270 | if (retval) |
1271 | return retval; |
1272 | |
1273 | /* |
1274 | * Allow userspace to request a mountpoint be expired rather than |
1275 | * unmounting unconditionally. Unmount only happens if: |
1276 | * (1) the mark is already set (the mark is cleared by mntput()) |
1277 | * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] |
1278 | */ |
1279 | if (flags & MNT_EXPIRE) { |
1280 | if (mnt == current->fs->root.mnt || |
1281 | flags & (MNT_FORCE | MNT_DETACH)) |
1282 | return -EINVAL; |
1283 | |
1284 | /* |
1285 | * probably don't strictly need the lock here if we examined |
1286 | * all race cases, but it's a slowpath. |
1287 | */ |
1288 | br_write_lock(vfsmount_lock); |
1289 | if (mnt_get_count(mnt) != 2) { |
1290 | br_write_unlock(vfsmount_lock); |
1291 | return -EBUSY; |
1292 | } |
1293 | br_write_unlock(vfsmount_lock); |
1294 | |
1295 | if (!xchg(&mnt->mnt_expiry_mark, 1)) |
1296 | return -EAGAIN; |
1297 | } |
1298 | |
1299 | /* |
1300 | * If we may have to abort operations to get out of this |
1301 | * mount, and they will themselves hold resources we must |
1302 | * allow the fs to do things. In the Unix tradition of |
1303 | * 'Gee thats tricky lets do it in userspace' the umount_begin |
1304 | * might fail to complete on the first run through as other tasks |
1305 | * must return, and the like. Thats for the mount program to worry |
1306 | * about for the moment. |
1307 | */ |
1308 | |
1309 | if (flags & MNT_FORCE && sb->s_op->umount_begin) { |
1310 | sb->s_op->umount_begin(sb); |
1311 | } |
1312 | |
1313 | /* |
1314 | * No sense to grab the lock for this test, but test itself looks |
1315 | * somewhat bogus. Suggestions for better replacement? |
1316 | * Ho-hum... In principle, we might treat that as umount + switch |
1317 | * to rootfs. GC would eventually take care of the old vfsmount. |
1318 | * Actually it makes sense, especially if rootfs would contain a |
1319 | * /reboot - static binary that would close all descriptors and |
1320 | * call reboot(9). Then init(8) could umount root and exec /reboot. |
1321 | */ |
1322 | if (mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { |
1323 | /* |
1324 | * Special case for "unmounting" root ... |
1325 | * we just try to remount it readonly. |
1326 | */ |
1327 | down_write(&sb->s_umount); |
1328 | if (!(sb->s_flags & MS_RDONLY)) |
1329 | retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); |
1330 | up_write(&sb->s_umount); |
1331 | return retval; |
1332 | } |
1333 | |
1334 | down_write(&namespace_sem); |
1335 | br_write_lock(vfsmount_lock); |
1336 | event++; |
1337 | |
1338 | if (!(flags & MNT_DETACH)) |
1339 | shrink_submounts(mnt, &umount_list); |
1340 | |
1341 | retval = -EBUSY; |
1342 | if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) { |
1343 | if (!list_empty(&mnt->mnt_list)) |
1344 | umount_tree(mnt, 1, &umount_list); |
1345 | retval = 0; |
1346 | } |
1347 | br_write_unlock(vfsmount_lock); |
1348 | up_write(&namespace_sem); |
1349 | release_mounts(&umount_list); |
1350 | return retval; |
1351 | } |
1352 | |
1353 | /* |
1354 | * Now umount can handle mount points as well as block devices. |
1355 | * This is important for filesystems which use unnamed block devices. |
1356 | * |
1357 | * We now support a flag for forced unmount like the other 'big iron' |
1358 | * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD |
1359 | */ |
1360 | |
1361 | SYSCALL_DEFINE2(umount, char __user *, name, int, flags) |
1362 | { |
1363 | struct path path; |
1364 | int retval; |
1365 | int lookup_flags = 0; |
1366 | |
1367 | if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) |
1368 | return -EINVAL; |
1369 | |
1370 | if (!(flags & UMOUNT_NOFOLLOW)) |
1371 | lookup_flags |= LOOKUP_FOLLOW; |
1372 | |
1373 | retval = user_path_at(AT_FDCWD, name, lookup_flags, &path); |
1374 | if (retval) |
1375 | goto out; |
1376 | retval = -EINVAL; |
1377 | if (path.dentry != path.mnt->mnt_root) |
1378 | goto dput_and_out; |
1379 | if (!check_mnt(path.mnt)) |
1380 | goto dput_and_out; |
1381 | |
1382 | retval = -EPERM; |
1383 | if (!capable(CAP_SYS_ADMIN)) |
1384 | goto dput_and_out; |
1385 | |
1386 | retval = do_umount(path.mnt, flags); |
1387 | dput_and_out: |
1388 | /* we mustn't call path_put() as that would clear mnt_expiry_mark */ |
1389 | dput(path.dentry); |
1390 | mntput_no_expire(path.mnt); |
1391 | out: |
1392 | return retval; |
1393 | } |
1394 | |
1395 | #ifdef __ARCH_WANT_SYS_OLDUMOUNT |
1396 | |
1397 | /* |
1398 | * The 2.0 compatible umount. No flags. |
1399 | */ |
1400 | SYSCALL_DEFINE1(oldumount, char __user *, name) |
1401 | { |
1402 | return sys_umount(name, 0); |
1403 | } |
1404 | |
1405 | #endif |
1406 | |
1407 | static int mount_is_safe(struct path *path) |
1408 | { |
1409 | if (capable(CAP_SYS_ADMIN)) |
1410 | return 0; |
1411 | return -EPERM; |
1412 | #ifdef notyet |
1413 | if (S_ISLNK(path->dentry->d_inode->i_mode)) |
1414 | return -EPERM; |
1415 | if (path->dentry->d_inode->i_mode & S_ISVTX) { |
1416 | if (current_uid() != path->dentry->d_inode->i_uid) |
1417 | return -EPERM; |
1418 | } |
1419 | if (inode_permission(path->dentry->d_inode, MAY_WRITE)) |
1420 | return -EPERM; |
1421 | return 0; |
1422 | #endif |
1423 | } |
1424 | |
1425 | struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, |
1426 | int flag) |
1427 | { |
1428 | struct vfsmount *res, *p, *q, *r, *s; |
1429 | struct path path; |
1430 | |
1431 | if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt)) |
1432 | return NULL; |
1433 | |
1434 | res = q = clone_mnt(mnt, dentry, flag); |
1435 | if (!q) |
1436 | goto Enomem; |
1437 | q->mnt_mountpoint = mnt->mnt_mountpoint; |
1438 | |
1439 | p = mnt; |
1440 | list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { |
1441 | if (!is_subdir(r->mnt_mountpoint, dentry)) |
1442 | continue; |
1443 | |
1444 | for (s = r; s; s = next_mnt(s, r)) { |
1445 | if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) { |
1446 | s = skip_mnt_tree(s); |
1447 | continue; |
1448 | } |
1449 | while (p != s->mnt_parent) { |
1450 | p = p->mnt_parent; |
1451 | q = q->mnt_parent; |
1452 | } |
1453 | p = s; |
1454 | path.mnt = q; |
1455 | path.dentry = p->mnt_mountpoint; |
1456 | q = clone_mnt(p, p->mnt_root, flag); |
1457 | if (!q) |
1458 | goto Enomem; |
1459 | br_write_lock(vfsmount_lock); |
1460 | list_add_tail(&q->mnt_list, &res->mnt_list); |
1461 | attach_mnt(q, &path); |
1462 | br_write_unlock(vfsmount_lock); |
1463 | } |
1464 | } |
1465 | return res; |
1466 | Enomem: |
1467 | if (res) { |
1468 | LIST_HEAD(umount_list); |
1469 | br_write_lock(vfsmount_lock); |
1470 | umount_tree(res, 0, &umount_list); |
1471 | br_write_unlock(vfsmount_lock); |
1472 | release_mounts(&umount_list); |
1473 | } |
1474 | return NULL; |
1475 | } |
1476 | |
1477 | struct vfsmount *collect_mounts(struct path *path) |
1478 | { |
1479 | struct vfsmount *tree; |
1480 | down_write(&namespace_sem); |
1481 | tree = copy_tree(path->mnt, path->dentry, CL_COPY_ALL | CL_PRIVATE); |
1482 | up_write(&namespace_sem); |
1483 | return tree; |
1484 | } |
1485 | |
1486 | void drop_collected_mounts(struct vfsmount *mnt) |
1487 | { |
1488 | LIST_HEAD(umount_list); |
1489 | down_write(&namespace_sem); |
1490 | br_write_lock(vfsmount_lock); |
1491 | umount_tree(mnt, 0, &umount_list); |
1492 | br_write_unlock(vfsmount_lock); |
1493 | up_write(&namespace_sem); |
1494 | release_mounts(&umount_list); |
1495 | } |
1496 | |
1497 | int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, |
1498 | struct vfsmount *root) |
1499 | { |
1500 | struct vfsmount *mnt; |
1501 | int res = f(root, arg); |
1502 | if (res) |
1503 | return res; |
1504 | list_for_each_entry(mnt, &root->mnt_list, mnt_list) { |
1505 | res = f(mnt, arg); |
1506 | if (res) |
1507 | return res; |
1508 | } |
1509 | return 0; |
1510 | } |
1511 | |
1512 | static void cleanup_group_ids(struct vfsmount *mnt, struct vfsmount *end) |
1513 | { |
1514 | struct vfsmount *p; |
1515 | |
1516 | for (p = mnt; p != end; p = next_mnt(p, mnt)) { |
1517 | if (p->mnt_group_id && !IS_MNT_SHARED(p)) |
1518 | mnt_release_group_id(p); |
1519 | } |
1520 | } |
1521 | |
1522 | static int invent_group_ids(struct vfsmount *mnt, bool recurse) |
1523 | { |
1524 | struct vfsmount *p; |
1525 | |
1526 | for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { |
1527 | if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { |
1528 | int err = mnt_alloc_group_id(p); |
1529 | if (err) { |
1530 | cleanup_group_ids(mnt, p); |
1531 | return err; |
1532 | } |
1533 | } |
1534 | } |
1535 | |
1536 | return 0; |
1537 | } |
1538 | |
1539 | /* |
1540 | * @source_mnt : mount tree to be attached |
1541 | * @nd : place the mount tree @source_mnt is attached |
1542 | * @parent_nd : if non-null, detach the source_mnt from its parent and |
1543 | * store the parent mount and mountpoint dentry. |
1544 | * (done when source_mnt is moved) |
1545 | * |
1546 | * NOTE: in the table below explains the semantics when a source mount |
1547 | * of a given type is attached to a destination mount of a given type. |
1548 | * --------------------------------------------------------------------------- |
1549 | * | BIND MOUNT OPERATION | |
1550 | * |************************************************************************** |
1551 | * | source-->| shared | private | slave | unbindable | |
1552 | * | dest | | | | | |
1553 | * | | | | | | | |
1554 | * | v | | | | | |
1555 | * |************************************************************************** |
1556 | * | shared | shared (++) | shared (+) | shared(+++)| invalid | |
1557 | * | | | | | | |
1558 | * |non-shared| shared (+) | private | slave (*) | invalid | |
1559 | * *************************************************************************** |
1560 | * A bind operation clones the source mount and mounts the clone on the |
1561 | * destination mount. |
1562 | * |
1563 | * (++) the cloned mount is propagated to all the mounts in the propagation |
1564 | * tree of the destination mount and the cloned mount is added to |
1565 | * the peer group of the source mount. |
1566 | * (+) the cloned mount is created under the destination mount and is marked |
1567 | * as shared. The cloned mount is added to the peer group of the source |
1568 | * mount. |
1569 | * (+++) the mount is propagated to all the mounts in the propagation tree |
1570 | * of the destination mount and the cloned mount is made slave |
1571 | * of the same master as that of the source mount. The cloned mount |
1572 | * is marked as 'shared and slave'. |
1573 | * (*) the cloned mount is made a slave of the same master as that of the |
1574 | * source mount. |
1575 | * |
1576 | * --------------------------------------------------------------------------- |
1577 | * | MOVE MOUNT OPERATION | |
1578 | * |************************************************************************** |
1579 | * | source-->| shared | private | slave | unbindable | |
1580 | * | dest | | | | | |
1581 | * | | | | | | | |
1582 | * | v | | | | | |
1583 | * |************************************************************************** |
1584 | * | shared | shared (+) | shared (+) | shared(+++) | invalid | |
1585 | * | | | | | | |
1586 | * |non-shared| shared (+*) | private | slave (*) | unbindable | |
1587 | * *************************************************************************** |
1588 | * |
1589 | * (+) the mount is moved to the destination. And is then propagated to |
1590 | * all the mounts in the propagation tree of the destination mount. |
1591 | * (+*) the mount is moved to the destination. |
1592 | * (+++) the mount is moved to the destination and is then propagated to |
1593 | * all the mounts belonging to the destination mount's propagation tree. |
1594 | * the mount is marked as 'shared and slave'. |
1595 | * (*) the mount continues to be a slave at the new location. |
1596 | * |
1597 | * if the source mount is a tree, the operations explained above is |
1598 | * applied to each mount in the tree. |
1599 | * Must be called without spinlocks held, since this function can sleep |
1600 | * in allocations. |
1601 | */ |
1602 | static int attach_recursive_mnt(struct vfsmount *source_mnt, |
1603 | struct path *path, struct path *parent_path) |
1604 | { |
1605 | LIST_HEAD(tree_list); |
1606 | struct vfsmount *dest_mnt = path->mnt; |
1607 | struct dentry *dest_dentry = path->dentry; |
1608 | struct vfsmount *child, *p; |
1609 | int err; |
1610 | |
1611 | if (IS_MNT_SHARED(dest_mnt)) { |
1612 | err = invent_group_ids(source_mnt, true); |
1613 | if (err) |
1614 | goto out; |
1615 | } |
1616 | err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list); |
1617 | if (err) |
1618 | goto out_cleanup_ids; |
1619 | |
1620 | br_write_lock(vfsmount_lock); |
1621 | |
1622 | if (IS_MNT_SHARED(dest_mnt)) { |
1623 | for (p = source_mnt; p; p = next_mnt(p, source_mnt)) |
1624 | set_mnt_shared(p); |
1625 | } |
1626 | if (parent_path) { |
1627 | detach_mnt(source_mnt, parent_path); |
1628 | attach_mnt(source_mnt, path); |
1629 | touch_mnt_namespace(parent_path->mnt->mnt_ns); |
1630 | } else { |
1631 | mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt); |
1632 | commit_tree(source_mnt); |
1633 | } |
1634 | |
1635 | list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { |
1636 | list_del_init(&child->mnt_hash); |
1637 | commit_tree(child); |
1638 | } |
1639 | br_write_unlock(vfsmount_lock); |
1640 | |
1641 | return 0; |
1642 | |
1643 | out_cleanup_ids: |
1644 | if (IS_MNT_SHARED(dest_mnt)) |
1645 | cleanup_group_ids(source_mnt, NULL); |
1646 | out: |
1647 | return err; |
1648 | } |
1649 | |
1650 | static int lock_mount(struct path *path) |
1651 | { |
1652 | struct vfsmount *mnt; |
1653 | retry: |
1654 | mutex_lock(&path->dentry->d_inode->i_mutex); |
1655 | if (unlikely(cant_mount(path->dentry))) { |
1656 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
1657 | return -ENOENT; |
1658 | } |
1659 | down_write(&namespace_sem); |
1660 | mnt = lookup_mnt(path); |
1661 | if (likely(!mnt)) |
1662 | return 0; |
1663 | up_write(&namespace_sem); |
1664 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
1665 | path_put(path); |
1666 | path->mnt = mnt; |
1667 | path->dentry = dget(mnt->mnt_root); |
1668 | goto retry; |
1669 | } |
1670 | |
1671 | static void unlock_mount(struct path *path) |
1672 | { |
1673 | up_write(&namespace_sem); |
1674 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
1675 | } |
1676 | |
1677 | static int graft_tree(struct vfsmount *mnt, struct path *path) |
1678 | { |
1679 | if (mnt->mnt_sb->s_flags & MS_NOUSER) |
1680 | return -EINVAL; |
1681 | |
1682 | if (S_ISDIR(path->dentry->d_inode->i_mode) != |
1683 | S_ISDIR(mnt->mnt_root->d_inode->i_mode)) |
1684 | return -ENOTDIR; |
1685 | |
1686 | if (d_unlinked(path->dentry)) |
1687 | return -ENOENT; |
1688 | |
1689 | return attach_recursive_mnt(mnt, path, NULL); |
1690 | } |
1691 | |
1692 | /* |
1693 | * Sanity check the flags to change_mnt_propagation. |
1694 | */ |
1695 | |
1696 | static int flags_to_propagation_type(int flags) |
1697 | { |
1698 | int type = flags & ~(MS_REC | MS_SILENT); |
1699 | |
1700 | /* Fail if any non-propagation flags are set */ |
1701 | if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
1702 | return 0; |
1703 | /* Only one propagation flag should be set */ |
1704 | if (!is_power_of_2(type)) |
1705 | return 0; |
1706 | return type; |
1707 | } |
1708 | |
1709 | /* |
1710 | * recursively change the type of the mountpoint. |
1711 | */ |
1712 | static int do_change_type(struct path *path, int flag) |
1713 | { |
1714 | struct vfsmount *m, *mnt = path->mnt; |
1715 | int recurse = flag & MS_REC; |
1716 | int type; |
1717 | int err = 0; |
1718 | |
1719 | if (!capable(CAP_SYS_ADMIN)) |
1720 | return -EPERM; |
1721 | |
1722 | if (path->dentry != path->mnt->mnt_root) |
1723 | return -EINVAL; |
1724 | |
1725 | type = flags_to_propagation_type(flag); |
1726 | if (!type) |
1727 | return -EINVAL; |
1728 | |
1729 | down_write(&namespace_sem); |
1730 | if (type == MS_SHARED) { |
1731 | err = invent_group_ids(mnt, recurse); |
1732 | if (err) |
1733 | goto out_unlock; |
1734 | } |
1735 | |
1736 | br_write_lock(vfsmount_lock); |
1737 | for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) |
1738 | change_mnt_propagation(m, type); |
1739 | br_write_unlock(vfsmount_lock); |
1740 | |
1741 | out_unlock: |
1742 | up_write(&namespace_sem); |
1743 | return err; |
1744 | } |
1745 | |
1746 | /* |
1747 | * do loopback mount. |
1748 | */ |
1749 | static int do_loopback(struct path *path, char *old_name, |
1750 | int recurse) |
1751 | { |
1752 | LIST_HEAD(umount_list); |
1753 | struct path old_path; |
1754 | struct vfsmount *mnt = NULL; |
1755 | int err = mount_is_safe(path); |
1756 | if (err) |
1757 | return err; |
1758 | if (!old_name || !*old_name) |
1759 | return -EINVAL; |
1760 | err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); |
1761 | if (err) |
1762 | return err; |
1763 | |
1764 | err = lock_mount(path); |
1765 | if (err) |
1766 | goto out; |
1767 | |
1768 | err = -EINVAL; |
1769 | if (IS_MNT_UNBINDABLE(old_path.mnt)) |
1770 | goto out2; |
1771 | |
1772 | if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt)) |
1773 | goto out2; |
1774 | |
1775 | err = -ENOMEM; |
1776 | if (recurse) |
1777 | mnt = copy_tree(old_path.mnt, old_path.dentry, 0); |
1778 | else |
1779 | mnt = clone_mnt(old_path.mnt, old_path.dentry, 0); |
1780 | |
1781 | if (!mnt) |
1782 | goto out2; |
1783 | |
1784 | err = graft_tree(mnt, path); |
1785 | if (err) { |
1786 | br_write_lock(vfsmount_lock); |
1787 | umount_tree(mnt, 0, &umount_list); |
1788 | br_write_unlock(vfsmount_lock); |
1789 | } |
1790 | out2: |
1791 | unlock_mount(path); |
1792 | release_mounts(&umount_list); |
1793 | out: |
1794 | path_put(&old_path); |
1795 | return err; |
1796 | } |
1797 | |
1798 | static int change_mount_flags(struct vfsmount *mnt, int ms_flags) |
1799 | { |
1800 | int error = 0; |
1801 | int readonly_request = 0; |
1802 | |
1803 | if (ms_flags & MS_RDONLY) |
1804 | readonly_request = 1; |
1805 | if (readonly_request == __mnt_is_readonly(mnt)) |
1806 | return 0; |
1807 | |
1808 | if (readonly_request) |
1809 | error = mnt_make_readonly(mnt); |
1810 | else |
1811 | __mnt_unmake_readonly(mnt); |
1812 | return error; |
1813 | } |
1814 | |
1815 | /* |
1816 | * change filesystem flags. dir should be a physical root of filesystem. |
1817 | * If you've mounted a non-root directory somewhere and want to do remount |
1818 | * on it - tough luck. |
1819 | */ |
1820 | static int do_remount(struct path *path, int flags, int mnt_flags, |
1821 | void *data) |
1822 | { |
1823 | int err; |
1824 | struct super_block *sb = path->mnt->mnt_sb; |
1825 | |
1826 | if (!capable(CAP_SYS_ADMIN)) |
1827 | return -EPERM; |
1828 | |
1829 | if (!check_mnt(path->mnt)) |
1830 | return -EINVAL; |
1831 | |
1832 | if (path->dentry != path->mnt->mnt_root) |
1833 | return -EINVAL; |
1834 | |
1835 | err = security_sb_remount(sb, data); |
1836 | if (err) |
1837 | return err; |
1838 | |
1839 | down_write(&sb->s_umount); |
1840 | if (flags & MS_BIND) |
1841 | err = change_mount_flags(path->mnt, flags); |
1842 | else |
1843 | err = do_remount_sb(sb, flags, data, 0); |
1844 | if (!err) { |
1845 | br_write_lock(vfsmount_lock); |
1846 | mnt_flags |= path->mnt->mnt_flags & MNT_PROPAGATION_MASK; |
1847 | path->mnt->mnt_flags = mnt_flags; |
1848 | br_write_unlock(vfsmount_lock); |
1849 | } |
1850 | up_write(&sb->s_umount); |
1851 | if (!err) { |
1852 | br_write_lock(vfsmount_lock); |
1853 | touch_mnt_namespace(path->mnt->mnt_ns); |
1854 | br_write_unlock(vfsmount_lock); |
1855 | } |
1856 | return err; |
1857 | } |
1858 | |
1859 | static inline int tree_contains_unbindable(struct vfsmount *mnt) |
1860 | { |
1861 | struct vfsmount *p; |
1862 | for (p = mnt; p; p = next_mnt(p, mnt)) { |
1863 | if (IS_MNT_UNBINDABLE(p)) |
1864 | return 1; |
1865 | } |
1866 | return 0; |
1867 | } |
1868 | |
1869 | static int do_move_mount(struct path *path, char *old_name) |
1870 | { |
1871 | struct path old_path, parent_path; |
1872 | struct vfsmount *p; |
1873 | int err = 0; |
1874 | if (!capable(CAP_SYS_ADMIN)) |
1875 | return -EPERM; |
1876 | if (!old_name || !*old_name) |
1877 | return -EINVAL; |
1878 | err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); |
1879 | if (err) |
1880 | return err; |
1881 | |
1882 | err = lock_mount(path); |
1883 | if (err < 0) |
1884 | goto out; |
1885 | |
1886 | err = -EINVAL; |
1887 | if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt)) |
1888 | goto out1; |
1889 | |
1890 | if (d_unlinked(path->dentry)) |
1891 | goto out1; |
1892 | |
1893 | err = -EINVAL; |
1894 | if (old_path.dentry != old_path.mnt->mnt_root) |
1895 | goto out1; |
1896 | |
1897 | if (old_path.mnt == old_path.mnt->mnt_parent) |
1898 | goto out1; |
1899 | |
1900 | if (S_ISDIR(path->dentry->d_inode->i_mode) != |
1901 | S_ISDIR(old_path.dentry->d_inode->i_mode)) |
1902 | goto out1; |
1903 | /* |
1904 | * Don't move a mount residing in a shared parent. |
1905 | */ |
1906 | if (old_path.mnt->mnt_parent && |
1907 | IS_MNT_SHARED(old_path.mnt->mnt_parent)) |
1908 | goto out1; |
1909 | /* |
1910 | * Don't move a mount tree containing unbindable mounts to a destination |
1911 | * mount which is shared. |
1912 | */ |
1913 | if (IS_MNT_SHARED(path->mnt) && |
1914 | tree_contains_unbindable(old_path.mnt)) |
1915 | goto out1; |
1916 | err = -ELOOP; |
1917 | for (p = path->mnt; p->mnt_parent != p; p = p->mnt_parent) |
1918 | if (p == old_path.mnt) |
1919 | goto out1; |
1920 | |
1921 | err = attach_recursive_mnt(old_path.mnt, path, &parent_path); |
1922 | if (err) |
1923 | goto out1; |
1924 | |
1925 | /* if the mount is moved, it should no longer be expire |
1926 | * automatically */ |
1927 | list_del_init(&old_path.mnt->mnt_expire); |
1928 | out1: |
1929 | unlock_mount(path); |
1930 | out: |
1931 | if (!err) |
1932 | path_put(&parent_path); |
1933 | path_put(&old_path); |
1934 | return err; |
1935 | } |
1936 | |
1937 | static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype) |
1938 | { |
1939 | int err; |
1940 | const char *subtype = strchr(fstype, '.'); |
1941 | if (subtype) { |
1942 | subtype++; |
1943 | err = -EINVAL; |
1944 | if (!subtype[0]) |
1945 | goto err; |
1946 | } else |
1947 | subtype = ""; |
1948 | |
1949 | mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL); |
1950 | err = -ENOMEM; |
1951 | if (!mnt->mnt_sb->s_subtype) |
1952 | goto err; |
1953 | return mnt; |
1954 | |
1955 | err: |
1956 | mntput(mnt); |
1957 | return ERR_PTR(err); |
1958 | } |
1959 | |
1960 | struct vfsmount * |
1961 | do_kern_mount(const char *fstype, int flags, const char *name, void *data) |
1962 | { |
1963 | struct file_system_type *type = get_fs_type(fstype); |
1964 | struct vfsmount *mnt; |
1965 | if (!type) |
1966 | return ERR_PTR(-ENODEV); |
1967 | mnt = vfs_kern_mount(type, flags, name, data); |
1968 | if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && |
1969 | !mnt->mnt_sb->s_subtype) |
1970 | mnt = fs_set_subtype(mnt, fstype); |
1971 | put_filesystem(type); |
1972 | return mnt; |
1973 | } |
1974 | EXPORT_SYMBOL_GPL(do_kern_mount); |
1975 | |
1976 | /* |
1977 | * add a mount into a namespace's mount tree |
1978 | */ |
1979 | static int do_add_mount(struct vfsmount *newmnt, struct path *path, int mnt_flags) |
1980 | { |
1981 | int err; |
1982 | |
1983 | mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL); |
1984 | |
1985 | err = lock_mount(path); |
1986 | if (err) |
1987 | return err; |
1988 | |
1989 | err = -EINVAL; |
1990 | if (!(mnt_flags & MNT_SHRINKABLE) && !check_mnt(path->mnt)) |
1991 | goto unlock; |
1992 | |
1993 | /* Refuse the same filesystem on the same mount point */ |
1994 | err = -EBUSY; |
1995 | if (path->mnt->mnt_sb == newmnt->mnt_sb && |
1996 | path->mnt->mnt_root == path->dentry) |
1997 | goto unlock; |
1998 | |
1999 | err = -EINVAL; |
2000 | if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode)) |
2001 | goto unlock; |
2002 | |
2003 | newmnt->mnt_flags = mnt_flags; |
2004 | err = graft_tree(newmnt, path); |
2005 | |
2006 | unlock: |
2007 | unlock_mount(path); |
2008 | return err; |
2009 | } |
2010 | |
2011 | /* |
2012 | * create a new mount for userspace and request it to be added into the |
2013 | * namespace's tree |
2014 | */ |
2015 | static int do_new_mount(struct path *path, char *type, int flags, |
2016 | int mnt_flags, char *name, void *data) |
2017 | { |
2018 | struct vfsmount *mnt; |
2019 | int err; |
2020 | |
2021 | if (!type) |
2022 | return -EINVAL; |
2023 | |
2024 | /* we need capabilities... */ |
2025 | if (!capable(CAP_SYS_ADMIN)) |
2026 | return -EPERM; |
2027 | |
2028 | mnt = do_kern_mount(type, flags, name, data); |
2029 | if (IS_ERR(mnt)) |
2030 | return PTR_ERR(mnt); |
2031 | |
2032 | err = do_add_mount(mnt, path, mnt_flags); |
2033 | if (err) |
2034 | mntput(mnt); |
2035 | return err; |
2036 | } |
2037 | |
2038 | int finish_automount(struct vfsmount *m, struct path *path) |
2039 | { |
2040 | int err; |
2041 | /* The new mount record should have at least 2 refs to prevent it being |
2042 | * expired before we get a chance to add it |
2043 | */ |
2044 | BUG_ON(mnt_get_count(m) < 2); |
2045 | |
2046 | if (m->mnt_sb == path->mnt->mnt_sb && |
2047 | m->mnt_root == path->dentry) { |
2048 | err = -ELOOP; |
2049 | goto fail; |
2050 | } |
2051 | |
2052 | err = do_add_mount(m, path, path->mnt->mnt_flags | MNT_SHRINKABLE); |
2053 | if (!err) |
2054 | return 0; |
2055 | fail: |
2056 | /* remove m from any expiration list it may be on */ |
2057 | if (!list_empty(&m->mnt_expire)) { |
2058 | down_write(&namespace_sem); |
2059 | br_write_lock(vfsmount_lock); |
2060 | list_del_init(&m->mnt_expire); |
2061 | br_write_unlock(vfsmount_lock); |
2062 | up_write(&namespace_sem); |
2063 | } |
2064 | mntput(m); |
2065 | mntput(m); |
2066 | return err; |
2067 | } |
2068 | |
2069 | /** |
2070 | * mnt_set_expiry - Put a mount on an expiration list |
2071 | * @mnt: The mount to list. |
2072 | * @expiry_list: The list to add the mount to. |
2073 | */ |
2074 | void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list) |
2075 | { |
2076 | down_write(&namespace_sem); |
2077 | br_write_lock(vfsmount_lock); |
2078 | |
2079 | list_add_tail(&mnt->mnt_expire, expiry_list); |
2080 | |
2081 | br_write_unlock(vfsmount_lock); |
2082 | up_write(&namespace_sem); |
2083 | } |
2084 | EXPORT_SYMBOL(mnt_set_expiry); |
2085 | |
2086 | /* |
2087 | * process a list of expirable mountpoints with the intent of discarding any |
2088 | * mountpoints that aren't in use and haven't been touched since last we came |
2089 | * here |
2090 | */ |
2091 | void mark_mounts_for_expiry(struct list_head *mounts) |
2092 | { |
2093 | struct vfsmount *mnt, *next; |
2094 | LIST_HEAD(graveyard); |
2095 | LIST_HEAD(umounts); |
2096 | |
2097 | if (list_empty(mounts)) |
2098 | return; |
2099 | |
2100 | down_write(&namespace_sem); |
2101 | br_write_lock(vfsmount_lock); |
2102 | |
2103 | /* extract from the expiration list every vfsmount that matches the |
2104 | * following criteria: |
2105 | * - only referenced by its parent vfsmount |
2106 | * - still marked for expiry (marked on the last call here; marks are |
2107 | * cleared by mntput()) |
2108 | */ |
2109 | list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { |
2110 | if (!xchg(&mnt->mnt_expiry_mark, 1) || |
2111 | propagate_mount_busy(mnt, 1)) |
2112 | continue; |
2113 | list_move(&mnt->mnt_expire, &graveyard); |
2114 | } |
2115 | while (!list_empty(&graveyard)) { |
2116 | mnt = list_first_entry(&graveyard, struct vfsmount, mnt_expire); |
2117 | touch_mnt_namespace(mnt->mnt_ns); |
2118 | umount_tree(mnt, 1, &umounts); |
2119 | } |
2120 | br_write_unlock(vfsmount_lock); |
2121 | up_write(&namespace_sem); |
2122 | |
2123 | release_mounts(&umounts); |
2124 | } |
2125 | |
2126 | EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); |
2127 | |
2128 | /* |
2129 | * Ripoff of 'select_parent()' |
2130 | * |
2131 | * search the list of submounts for a given mountpoint, and move any |
2132 | * shrinkable submounts to the 'graveyard' list. |
2133 | */ |
2134 | static int select_submounts(struct vfsmount *parent, struct list_head *graveyard) |
2135 | { |
2136 | struct vfsmount *this_parent = parent; |
2137 | struct list_head *next; |
2138 | int found = 0; |
2139 | |
2140 | repeat: |
2141 | next = this_parent->mnt_mounts.next; |
2142 | resume: |
2143 | while (next != &this_parent->mnt_mounts) { |
2144 | struct list_head *tmp = next; |
2145 | struct vfsmount *mnt = list_entry(tmp, struct vfsmount, mnt_child); |
2146 | |
2147 | next = tmp->next; |
2148 | if (!(mnt->mnt_flags & MNT_SHRINKABLE)) |
2149 | continue; |
2150 | /* |
2151 | * Descend a level if the d_mounts list is non-empty. |
2152 | */ |
2153 | if (!list_empty(&mnt->mnt_mounts)) { |
2154 | this_parent = mnt; |
2155 | goto repeat; |
2156 | } |
2157 | |
2158 | if (!propagate_mount_busy(mnt, 1)) { |
2159 | list_move_tail(&mnt->mnt_expire, graveyard); |
2160 | found++; |
2161 | } |
2162 | } |
2163 | /* |
2164 | * All done at this level ... ascend and resume the search |
2165 | */ |
2166 | if (this_parent != parent) { |
2167 | next = this_parent->mnt_child.next; |
2168 | this_parent = this_parent->mnt_parent; |
2169 | goto resume; |
2170 | } |
2171 | return found; |
2172 | } |
2173 | |
2174 | /* |
2175 | * process a list of expirable mountpoints with the intent of discarding any |
2176 | * submounts of a specific parent mountpoint |
2177 | * |
2178 | * vfsmount_lock must be held for write |
2179 | */ |
2180 | static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts) |
2181 | { |
2182 | LIST_HEAD(graveyard); |
2183 | struct vfsmount *m; |
2184 | |
2185 | /* extract submounts of 'mountpoint' from the expiration list */ |
2186 | while (select_submounts(mnt, &graveyard)) { |
2187 | while (!list_empty(&graveyard)) { |
2188 | m = list_first_entry(&graveyard, struct vfsmount, |
2189 | mnt_expire); |
2190 | touch_mnt_namespace(m->mnt_ns); |
2191 | umount_tree(m, 1, umounts); |
2192 | } |
2193 | } |
2194 | } |
2195 | |
2196 | /* |
2197 | * Some copy_from_user() implementations do not return the exact number of |
2198 | * bytes remaining to copy on a fault. But copy_mount_options() requires that. |
2199 | * Note that this function differs from copy_from_user() in that it will oops |
2200 | * on bad values of `to', rather than returning a short copy. |
2201 | */ |
2202 | static long exact_copy_from_user(void *to, const void __user * from, |
2203 | unsigned long n) |
2204 | { |
2205 | char *t = to; |
2206 | const char __user *f = from; |
2207 | char c; |
2208 | |
2209 | if (!access_ok(VERIFY_READ, from, n)) |
2210 | return n; |
2211 | |
2212 | while (n) { |
2213 | if (__get_user(c, f)) { |
2214 | memset(t, 0, n); |
2215 | break; |
2216 | } |
2217 | *t++ = c; |
2218 | f++; |
2219 | n--; |
2220 | } |
2221 | return n; |
2222 | } |
2223 | |
2224 | int copy_mount_options(const void __user * data, unsigned long *where) |
2225 | { |
2226 | int i; |
2227 | unsigned long page; |
2228 | unsigned long size; |
2229 | |
2230 | *where = 0; |
2231 | if (!data) |
2232 | return 0; |
2233 | |
2234 | if (!(page = __get_free_page(GFP_KERNEL))) |
2235 | return -ENOMEM; |
2236 | |
2237 | /* We only care that *some* data at the address the user |
2238 | * gave us is valid. Just in case, we'll zero |
2239 | * the remainder of the page. |
2240 | */ |
2241 | /* copy_from_user cannot cross TASK_SIZE ! */ |
2242 | size = TASK_SIZE - (unsigned long)data; |
2243 | if (size > PAGE_SIZE) |
2244 | size = PAGE_SIZE; |
2245 | |
2246 | i = size - exact_copy_from_user((void *)page, data, size); |
2247 | if (!i) { |
2248 | free_page(page); |
2249 | return -EFAULT; |
2250 | } |
2251 | if (i != PAGE_SIZE) |
2252 | memset((char *)page + i, 0, PAGE_SIZE - i); |
2253 | *where = page; |
2254 | return 0; |
2255 | } |
2256 | |
2257 | int copy_mount_string(const void __user *data, char **where) |
2258 | { |
2259 | char *tmp; |
2260 | |
2261 | if (!data) { |
2262 | *where = NULL; |
2263 | return 0; |
2264 | } |
2265 | |
2266 | tmp = strndup_user(data, PAGE_SIZE); |
2267 | if (IS_ERR(tmp)) |
2268 | return PTR_ERR(tmp); |
2269 | |
2270 | *where = tmp; |
2271 | return 0; |
2272 | } |
2273 | |
2274 | /* |
2275 | * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to |
2276 | * be given to the mount() call (ie: read-only, no-dev, no-suid etc). |
2277 | * |
2278 | * data is a (void *) that can point to any structure up to |
2279 | * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent |
2280 | * information (or be NULL). |
2281 | * |
2282 | * Pre-0.97 versions of mount() didn't have a flags word. |
2283 | * When the flags word was introduced its top half was required |
2284 | * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. |
2285 | * Therefore, if this magic number is present, it carries no information |
2286 | * and must be discarded. |
2287 | */ |
2288 | long do_mount(char *dev_name, char *dir_name, char *type_page, |
2289 | unsigned long flags, void *data_page) |
2290 | { |
2291 | struct path path; |
2292 | int retval = 0; |
2293 | int mnt_flags = 0; |
2294 | |
2295 | /* Discard magic */ |
2296 | if ((flags & MS_MGC_MSK) == MS_MGC_VAL) |
2297 | flags &= ~MS_MGC_MSK; |
2298 | |
2299 | /* Basic sanity checks */ |
2300 | |
2301 | if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) |
2302 | return -EINVAL; |
2303 | |
2304 | if (data_page) |
2305 | ((char *)data_page)[PAGE_SIZE - 1] = 0; |
2306 | |
2307 | /* ... and get the mountpoint */ |
2308 | retval = kern_path(dir_name, LOOKUP_FOLLOW, &path); |
2309 | if (retval) |
2310 | return retval; |
2311 | |
2312 | retval = security_sb_mount(dev_name, &path, |
2313 | type_page, flags, data_page); |
2314 | if (retval) |
2315 | goto dput_out; |
2316 | |
2317 | /* Default to relatime unless overriden */ |
2318 | if (!(flags & MS_NOATIME)) |
2319 | mnt_flags |= MNT_RELATIME; |
2320 | |
2321 | /* Separate the per-mountpoint flags */ |
2322 | if (flags & MS_NOSUID) |
2323 | mnt_flags |= MNT_NOSUID; |
2324 | if (flags & MS_NODEV) |
2325 | mnt_flags |= MNT_NODEV; |
2326 | if (flags & MS_NOEXEC) |
2327 | mnt_flags |= MNT_NOEXEC; |
2328 | if (flags & MS_NOATIME) |
2329 | mnt_flags |= MNT_NOATIME; |
2330 | if (flags & MS_NODIRATIME) |
2331 | mnt_flags |= MNT_NODIRATIME; |
2332 | if (flags & MS_STRICTATIME) |
2333 | mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); |
2334 | if (flags & MS_RDONLY) |
2335 | mnt_flags |= MNT_READONLY; |
2336 | |
2337 | flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN | |
2338 | MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT | |
2339 | MS_STRICTATIME); |
2340 | |
2341 | if (flags & MS_REMOUNT) |
2342 | retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags, |
2343 | data_page); |
2344 | else if (flags & MS_BIND) |
2345 | retval = do_loopback(&path, dev_name, flags & MS_REC); |
2346 | else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
2347 | retval = do_change_type(&path, flags); |
2348 | else if (flags & MS_MOVE) |
2349 | retval = do_move_mount(&path, dev_name); |
2350 | else |
2351 | retval = do_new_mount(&path, type_page, flags, mnt_flags, |
2352 | dev_name, data_page); |
2353 | dput_out: |
2354 | path_put(&path); |
2355 | return retval; |
2356 | } |
2357 | |
2358 | static struct mnt_namespace *alloc_mnt_ns(void) |
2359 | { |
2360 | struct mnt_namespace *new_ns; |
2361 | |
2362 | new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); |
2363 | if (!new_ns) |
2364 | return ERR_PTR(-ENOMEM); |
2365 | atomic_set(&new_ns->count, 1); |
2366 | new_ns->root = NULL; |
2367 | INIT_LIST_HEAD(&new_ns->list); |
2368 | init_waitqueue_head(&new_ns->poll); |
2369 | new_ns->event = 0; |
2370 | return new_ns; |
2371 | } |
2372 | |
2373 | void mnt_make_longterm(struct vfsmount *mnt) |
2374 | { |
2375 | __mnt_make_longterm(mnt); |
2376 | } |
2377 | |
2378 | void mnt_make_shortterm(struct vfsmount *mnt) |
2379 | { |
2380 | #ifdef CONFIG_SMP |
2381 | if (atomic_add_unless(&mnt->mnt_longterm, -1, 1)) |
2382 | return; |
2383 | br_write_lock(vfsmount_lock); |
2384 | atomic_dec(&mnt->mnt_longterm); |
2385 | br_write_unlock(vfsmount_lock); |
2386 | #endif |
2387 | } |
2388 | |
2389 | /* |
2390 | * Allocate a new namespace structure and populate it with contents |
2391 | * copied from the namespace of the passed in task structure. |
2392 | */ |
2393 | static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns, |
2394 | struct fs_struct *fs) |
2395 | { |
2396 | struct mnt_namespace *new_ns; |
2397 | struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; |
2398 | struct vfsmount *p, *q; |
2399 | |
2400 | new_ns = alloc_mnt_ns(); |
2401 | if (IS_ERR(new_ns)) |
2402 | return new_ns; |
2403 | |
2404 | down_write(&namespace_sem); |
2405 | /* First pass: copy the tree topology */ |
2406 | new_ns->root = copy_tree(mnt_ns->root, mnt_ns->root->mnt_root, |
2407 | CL_COPY_ALL | CL_EXPIRE); |
2408 | if (!new_ns->root) { |
2409 | up_write(&namespace_sem); |
2410 | kfree(new_ns); |
2411 | return ERR_PTR(-ENOMEM); |
2412 | } |
2413 | br_write_lock(vfsmount_lock); |
2414 | list_add_tail(&new_ns->list, &new_ns->root->mnt_list); |
2415 | br_write_unlock(vfsmount_lock); |
2416 | |
2417 | /* |
2418 | * Second pass: switch the tsk->fs->* elements and mark new vfsmounts |
2419 | * as belonging to new namespace. We have already acquired a private |
2420 | * fs_struct, so tsk->fs->lock is not needed. |
2421 | */ |
2422 | p = mnt_ns->root; |
2423 | q = new_ns->root; |
2424 | while (p) { |
2425 | q->mnt_ns = new_ns; |
2426 | __mnt_make_longterm(q); |
2427 | if (fs) { |
2428 | if (p == fs->root.mnt) { |
2429 | fs->root.mnt = mntget(q); |
2430 | __mnt_make_longterm(q); |
2431 | mnt_make_shortterm(p); |
2432 | rootmnt = p; |
2433 | } |
2434 | if (p == fs->pwd.mnt) { |
2435 | fs->pwd.mnt = mntget(q); |
2436 | __mnt_make_longterm(q); |
2437 | mnt_make_shortterm(p); |
2438 | pwdmnt = p; |
2439 | } |
2440 | } |
2441 | p = next_mnt(p, mnt_ns->root); |
2442 | q = next_mnt(q, new_ns->root); |
2443 | } |
2444 | up_write(&namespace_sem); |
2445 | |
2446 | if (rootmnt) |
2447 | mntput(rootmnt); |
2448 | if (pwdmnt) |
2449 | mntput(pwdmnt); |
2450 | |
2451 | return new_ns; |
2452 | } |
2453 | |
2454 | struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, |
2455 | struct fs_struct *new_fs) |
2456 | { |
2457 | struct mnt_namespace *new_ns; |
2458 | |
2459 | BUG_ON(!ns); |
2460 | get_mnt_ns(ns); |
2461 | |
2462 | if (!(flags & CLONE_NEWNS)) |
2463 | return ns; |
2464 | |
2465 | new_ns = dup_mnt_ns(ns, new_fs); |
2466 | |
2467 | put_mnt_ns(ns); |
2468 | return new_ns; |
2469 | } |
2470 | |
2471 | /** |
2472 | * create_mnt_ns - creates a private namespace and adds a root filesystem |
2473 | * @mnt: pointer to the new root filesystem mountpoint |
2474 | */ |
2475 | struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt) |
2476 | { |
2477 | struct mnt_namespace *new_ns; |
2478 | |
2479 | new_ns = alloc_mnt_ns(); |
2480 | if (!IS_ERR(new_ns)) { |
2481 | mnt->mnt_ns = new_ns; |
2482 | __mnt_make_longterm(mnt); |
2483 | new_ns->root = mnt; |
2484 | list_add(&new_ns->list, &new_ns->root->mnt_list); |
2485 | } |
2486 | return new_ns; |
2487 | } |
2488 | EXPORT_SYMBOL(create_mnt_ns); |
2489 | |
2490 | SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, |
2491 | char __user *, type, unsigned long, flags, void __user *, data) |
2492 | { |
2493 | int ret; |
2494 | char *kernel_type; |
2495 | char *kernel_dir; |
2496 | char *kernel_dev; |
2497 | unsigned long data_page; |
2498 | |
2499 | ret = copy_mount_string(type, &kernel_type); |
2500 | if (ret < 0) |
2501 | goto out_type; |
2502 | |
2503 | kernel_dir = getname(dir_name); |
2504 | if (IS_ERR(kernel_dir)) { |
2505 | ret = PTR_ERR(kernel_dir); |
2506 | goto out_dir; |
2507 | } |
2508 | |
2509 | ret = copy_mount_string(dev_name, &kernel_dev); |
2510 | if (ret < 0) |
2511 | goto out_dev; |
2512 | |
2513 | ret = copy_mount_options(data, &data_page); |
2514 | if (ret < 0) |
2515 | goto out_data; |
2516 | |
2517 | ret = do_mount(kernel_dev, kernel_dir, kernel_type, flags, |
2518 | (void *) data_page); |
2519 | |
2520 | free_page(data_page); |
2521 | out_data: |
2522 | kfree(kernel_dev); |
2523 | out_dev: |
2524 | putname(kernel_dir); |
2525 | out_dir: |
2526 | kfree(kernel_type); |
2527 | out_type: |
2528 | return ret; |
2529 | } |
2530 | |
2531 | /* |
2532 | * pivot_root Semantics: |
2533 | * Moves the root file system of the current process to the directory put_old, |
2534 | * makes new_root as the new root file system of the current process, and sets |
2535 | * root/cwd of all processes which had them on the current root to new_root. |
2536 | * |
2537 | * Restrictions: |
2538 | * The new_root and put_old must be directories, and must not be on the |
2539 | * same file system as the current process root. The put_old must be |
2540 | * underneath new_root, i.e. adding a non-zero number of /.. to the string |
2541 | * pointed to by put_old must yield the same directory as new_root. No other |
2542 | * file system may be mounted on put_old. After all, new_root is a mountpoint. |
2543 | * |
2544 | * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. |
2545 | * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives |
2546 | * in this situation. |
2547 | * |
2548 | * Notes: |
2549 | * - we don't move root/cwd if they are not at the root (reason: if something |
2550 | * cared enough to change them, it's probably wrong to force them elsewhere) |
2551 | * - it's okay to pick a root that isn't the root of a file system, e.g. |
2552 | * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, |
2553 | * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root |
2554 | * first. |
2555 | */ |
2556 | SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, |
2557 | const char __user *, put_old) |
2558 | { |
2559 | struct vfsmount *tmp; |
2560 | struct path new, old, parent_path, root_parent, root; |
2561 | int error; |
2562 | |
2563 | if (!capable(CAP_SYS_ADMIN)) |
2564 | return -EPERM; |
2565 | |
2566 | error = user_path_dir(new_root, &new); |
2567 | if (error) |
2568 | goto out0; |
2569 | |
2570 | error = user_path_dir(put_old, &old); |
2571 | if (error) |
2572 | goto out1; |
2573 | |
2574 | error = security_sb_pivotroot(&old, &new); |
2575 | if (error) |
2576 | goto out2; |
2577 | |
2578 | get_fs_root(current->fs, &root); |
2579 | error = lock_mount(&old); |
2580 | if (error) |
2581 | goto out3; |
2582 | |
2583 | error = -EINVAL; |
2584 | if (IS_MNT_SHARED(old.mnt) || |
2585 | IS_MNT_SHARED(new.mnt->mnt_parent) || |
2586 | IS_MNT_SHARED(root.mnt->mnt_parent)) |
2587 | goto out4; |
2588 | if (!check_mnt(root.mnt) || !check_mnt(new.mnt)) |
2589 | goto out4; |
2590 | error = -ENOENT; |
2591 | if (d_unlinked(new.dentry)) |
2592 | goto out4; |
2593 | if (d_unlinked(old.dentry)) |
2594 | goto out4; |
2595 | error = -EBUSY; |
2596 | if (new.mnt == root.mnt || |
2597 | old.mnt == root.mnt) |
2598 | goto out4; /* loop, on the same file system */ |
2599 | error = -EINVAL; |
2600 | if (root.mnt->mnt_root != root.dentry) |
2601 | goto out4; /* not a mountpoint */ |
2602 | if (root.mnt->mnt_parent == root.mnt) |
2603 | goto out4; /* not attached */ |
2604 | if (new.mnt->mnt_root != new.dentry) |
2605 | goto out4; /* not a mountpoint */ |
2606 | if (new.mnt->mnt_parent == new.mnt) |
2607 | goto out4; /* not attached */ |
2608 | /* make sure we can reach put_old from new_root */ |
2609 | tmp = old.mnt; |
2610 | if (tmp != new.mnt) { |
2611 | for (;;) { |
2612 | if (tmp->mnt_parent == tmp) |
2613 | goto out4; /* already mounted on put_old */ |
2614 | if (tmp->mnt_parent == new.mnt) |
2615 | break; |
2616 | tmp = tmp->mnt_parent; |
2617 | } |
2618 | if (!is_subdir(tmp->mnt_mountpoint, new.dentry)) |
2619 | goto out4; |
2620 | } else if (!is_subdir(old.dentry, new.dentry)) |
2621 | goto out4; |
2622 | br_write_lock(vfsmount_lock); |
2623 | detach_mnt(new.mnt, &parent_path); |
2624 | detach_mnt(root.mnt, &root_parent); |
2625 | /* mount old root on put_old */ |
2626 | attach_mnt(root.mnt, &old); |
2627 | /* mount new_root on / */ |
2628 | attach_mnt(new.mnt, &root_parent); |
2629 | touch_mnt_namespace(current->nsproxy->mnt_ns); |
2630 | br_write_unlock(vfsmount_lock); |
2631 | chroot_fs_refs(&root, &new); |
2632 | error = 0; |
2633 | out4: |
2634 | unlock_mount(&old); |
2635 | if (!error) { |
2636 | path_put(&root_parent); |
2637 | path_put(&parent_path); |
2638 | } |
2639 | out3: |
2640 | path_put(&root); |
2641 | out2: |
2642 | path_put(&old); |
2643 | out1: |
2644 | path_put(&new); |
2645 | out0: |
2646 | return error; |
2647 | } |
2648 | |
2649 | static void __init init_mount_tree(void) |
2650 | { |
2651 | struct vfsmount *mnt; |
2652 | struct mnt_namespace *ns; |
2653 | struct path root; |
2654 | |
2655 | mnt = do_kern_mount("rootfs", 0, "rootfs", NULL); |
2656 | if (IS_ERR(mnt)) |
2657 | panic("Can't create rootfs"); |
2658 | |
2659 | ns = create_mnt_ns(mnt); |
2660 | if (IS_ERR(ns)) |
2661 | panic("Can't allocate initial namespace"); |
2662 | |
2663 | init_task.nsproxy->mnt_ns = ns; |
2664 | get_mnt_ns(ns); |
2665 | |
2666 | root.mnt = ns->root; |
2667 | root.dentry = ns->root->mnt_root; |
2668 | |
2669 | set_fs_pwd(current->fs, &root); |
2670 | set_fs_root(current->fs, &root); |
2671 | } |
2672 | |
2673 | void __init mnt_init(void) |
2674 | { |
2675 | unsigned u; |
2676 | int err; |
2677 | |
2678 | init_rwsem(&namespace_sem); |
2679 | |
2680 | mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount), |
2681 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); |
2682 | |
2683 | mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); |
2684 | |
2685 | if (!mount_hashtable) |
2686 | panic("Failed to allocate mount hash table\n"); |
2687 | |
2688 | printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE); |
2689 | |
2690 | for (u = 0; u < HASH_SIZE; u++) |
2691 | INIT_LIST_HEAD(&mount_hashtable[u]); |
2692 | |
2693 | br_lock_init(vfsmount_lock); |
2694 | |
2695 | err = sysfs_init(); |
2696 | if (err) |
2697 | printk(KERN_WARNING "%s: sysfs_init error: %d\n", |
2698 | __func__, err); |
2699 | fs_kobj = kobject_create_and_add("fs", NULL); |
2700 | if (!fs_kobj) |
2701 | printk(KERN_WARNING "%s: kobj create error\n", __func__); |
2702 | init_rootfs(); |
2703 | init_mount_tree(); |
2704 | } |
2705 | |
2706 | void put_mnt_ns(struct mnt_namespace *ns) |
2707 | { |
2708 | LIST_HEAD(umount_list); |
2709 | |
2710 | if (!atomic_dec_and_test(&ns->count)) |
2711 | return; |
2712 | down_write(&namespace_sem); |
2713 | br_write_lock(vfsmount_lock); |
2714 | umount_tree(ns->root, 0, &umount_list); |
2715 | br_write_unlock(vfsmount_lock); |
2716 | up_write(&namespace_sem); |
2717 | release_mounts(&umount_list); |
2718 | kfree(ns); |
2719 | } |
2720 | EXPORT_SYMBOL(put_mnt_ns); |
2721 | |
2722 | struct vfsmount *kern_mount_data(struct file_system_type *type, void *data) |
2723 | { |
2724 | return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data); |
2725 | } |
2726 | EXPORT_SYMBOL_GPL(kern_mount_data); |
2727 |
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