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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 | struct vfsmount *alloc_vfsmnt(const char *name) |
142 | { |
143 | struct vfsmount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); |
144 | if (mnt) { |
145 | int err; |
146 | |
147 | err = mnt_alloc_id(mnt); |
148 | if (err) |
149 | goto out_free_cache; |
150 | |
151 | if (name) { |
152 | mnt->mnt_devname = kstrdup(name, GFP_KERNEL); |
153 | if (!mnt->mnt_devname) |
154 | goto out_free_id; |
155 | } |
156 | |
157 | atomic_set(&mnt->mnt_count, 1); |
158 | INIT_LIST_HEAD(&mnt->mnt_hash); |
159 | INIT_LIST_HEAD(&mnt->mnt_child); |
160 | INIT_LIST_HEAD(&mnt->mnt_mounts); |
161 | INIT_LIST_HEAD(&mnt->mnt_list); |
162 | INIT_LIST_HEAD(&mnt->mnt_expire); |
163 | INIT_LIST_HEAD(&mnt->mnt_share); |
164 | INIT_LIST_HEAD(&mnt->mnt_slave_list); |
165 | INIT_LIST_HEAD(&mnt->mnt_slave); |
166 | #ifdef CONFIG_FSNOTIFY |
167 | INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks); |
168 | #endif |
169 | #ifdef CONFIG_SMP |
170 | mnt->mnt_writers = alloc_percpu(int); |
171 | if (!mnt->mnt_writers) |
172 | goto out_free_devname; |
173 | #else |
174 | mnt->mnt_writers = 0; |
175 | #endif |
176 | } |
177 | return mnt; |
178 | |
179 | #ifdef CONFIG_SMP |
180 | out_free_devname: |
181 | kfree(mnt->mnt_devname); |
182 | #endif |
183 | out_free_id: |
184 | mnt_free_id(mnt); |
185 | out_free_cache: |
186 | kmem_cache_free(mnt_cache, mnt); |
187 | return NULL; |
188 | } |
189 | |
190 | /* |
191 | * Most r/o checks on a fs are for operations that take |
192 | * discrete amounts of time, like a write() or unlink(). |
193 | * We must keep track of when those operations start |
194 | * (for permission checks) and when they end, so that |
195 | * we can determine when writes are able to occur to |
196 | * a filesystem. |
197 | */ |
198 | /* |
199 | * __mnt_is_readonly: check whether a mount is read-only |
200 | * @mnt: the mount to check for its write status |
201 | * |
202 | * This shouldn't be used directly ouside of the VFS. |
203 | * It does not guarantee that the filesystem will stay |
204 | * r/w, just that it is right *now*. This can not and |
205 | * should not be used in place of IS_RDONLY(inode). |
206 | * mnt_want/drop_write() will _keep_ the filesystem |
207 | * r/w. |
208 | */ |
209 | int __mnt_is_readonly(struct vfsmount *mnt) |
210 | { |
211 | if (mnt->mnt_flags & MNT_READONLY) |
212 | return 1; |
213 | if (mnt->mnt_sb->s_flags & MS_RDONLY) |
214 | return 1; |
215 | return 0; |
216 | } |
217 | EXPORT_SYMBOL_GPL(__mnt_is_readonly); |
218 | |
219 | static inline void inc_mnt_writers(struct vfsmount *mnt) |
220 | { |
221 | #ifdef CONFIG_SMP |
222 | (*per_cpu_ptr(mnt->mnt_writers, smp_processor_id()))++; |
223 | #else |
224 | mnt->mnt_writers++; |
225 | #endif |
226 | } |
227 | |
228 | static inline void dec_mnt_writers(struct vfsmount *mnt) |
229 | { |
230 | #ifdef CONFIG_SMP |
231 | (*per_cpu_ptr(mnt->mnt_writers, smp_processor_id()))--; |
232 | #else |
233 | mnt->mnt_writers--; |
234 | #endif |
235 | } |
236 | |
237 | static unsigned int count_mnt_writers(struct vfsmount *mnt) |
238 | { |
239 | #ifdef CONFIG_SMP |
240 | unsigned int count = 0; |
241 | int cpu; |
242 | |
243 | for_each_possible_cpu(cpu) { |
244 | count += *per_cpu_ptr(mnt->mnt_writers, cpu); |
245 | } |
246 | |
247 | return count; |
248 | #else |
249 | return mnt->mnt_writers; |
250 | #endif |
251 | } |
252 | |
253 | /* |
254 | * Most r/o checks on a fs are for operations that take |
255 | * discrete amounts of time, like a write() or unlink(). |
256 | * We must keep track of when those operations start |
257 | * (for permission checks) and when they end, so that |
258 | * we can determine when writes are able to occur to |
259 | * a filesystem. |
260 | */ |
261 | /** |
262 | * mnt_want_write - get write access to a mount |
263 | * @mnt: the mount on which to take a write |
264 | * |
265 | * This tells the low-level filesystem that a write is |
266 | * about to be performed to it, and makes sure that |
267 | * writes are allowed before returning success. When |
268 | * the write operation is finished, mnt_drop_write() |
269 | * must be called. This is effectively a refcount. |
270 | */ |
271 | int mnt_want_write(struct vfsmount *mnt) |
272 | { |
273 | int ret = 0; |
274 | |
275 | preempt_disable(); |
276 | inc_mnt_writers(mnt); |
277 | /* |
278 | * The store to inc_mnt_writers must be visible before we pass |
279 | * MNT_WRITE_HOLD loop below, so that the slowpath can see our |
280 | * incremented count after it has set MNT_WRITE_HOLD. |
281 | */ |
282 | smp_mb(); |
283 | while (mnt->mnt_flags & MNT_WRITE_HOLD) |
284 | cpu_relax(); |
285 | /* |
286 | * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will |
287 | * be set to match its requirements. So we must not load that until |
288 | * MNT_WRITE_HOLD is cleared. |
289 | */ |
290 | smp_rmb(); |
291 | if (__mnt_is_readonly(mnt)) { |
292 | dec_mnt_writers(mnt); |
293 | ret = -EROFS; |
294 | goto out; |
295 | } |
296 | out: |
297 | preempt_enable(); |
298 | return ret; |
299 | } |
300 | EXPORT_SYMBOL_GPL(mnt_want_write); |
301 | |
302 | /** |
303 | * mnt_clone_write - get write access to a mount |
304 | * @mnt: the mount on which to take a write |
305 | * |
306 | * This is effectively like mnt_want_write, except |
307 | * it must only be used to take an extra write reference |
308 | * on a mountpoint that we already know has a write reference |
309 | * on it. This allows some optimisation. |
310 | * |
311 | * After finished, mnt_drop_write must be called as usual to |
312 | * drop the reference. |
313 | */ |
314 | int mnt_clone_write(struct vfsmount *mnt) |
315 | { |
316 | /* superblock may be r/o */ |
317 | if (__mnt_is_readonly(mnt)) |
318 | return -EROFS; |
319 | preempt_disable(); |
320 | inc_mnt_writers(mnt); |
321 | preempt_enable(); |
322 | return 0; |
323 | } |
324 | EXPORT_SYMBOL_GPL(mnt_clone_write); |
325 | |
326 | /** |
327 | * mnt_want_write_file - get write access to a file's mount |
328 | * @file: the file who's mount on which to take a write |
329 | * |
330 | * This is like mnt_want_write, but it takes a file and can |
331 | * do some optimisations if the file is open for write already |
332 | */ |
333 | int mnt_want_write_file(struct file *file) |
334 | { |
335 | struct inode *inode = file->f_dentry->d_inode; |
336 | if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode)) |
337 | return mnt_want_write(file->f_path.mnt); |
338 | else |
339 | return mnt_clone_write(file->f_path.mnt); |
340 | } |
341 | EXPORT_SYMBOL_GPL(mnt_want_write_file); |
342 | |
343 | /** |
344 | * mnt_drop_write - give up write access to a mount |
345 | * @mnt: the mount on which to give up write access |
346 | * |
347 | * Tells the low-level filesystem that we are done |
348 | * performing writes to it. Must be matched with |
349 | * mnt_want_write() call above. |
350 | */ |
351 | void mnt_drop_write(struct vfsmount *mnt) |
352 | { |
353 | preempt_disable(); |
354 | dec_mnt_writers(mnt); |
355 | preempt_enable(); |
356 | } |
357 | EXPORT_SYMBOL_GPL(mnt_drop_write); |
358 | |
359 | static int mnt_make_readonly(struct vfsmount *mnt) |
360 | { |
361 | int ret = 0; |
362 | |
363 | br_write_lock(vfsmount_lock); |
364 | mnt->mnt_flags |= MNT_WRITE_HOLD; |
365 | /* |
366 | * After storing MNT_WRITE_HOLD, we'll read the counters. This store |
367 | * should be visible before we do. |
368 | */ |
369 | smp_mb(); |
370 | |
371 | /* |
372 | * With writers on hold, if this value is zero, then there are |
373 | * definitely no active writers (although held writers may subsequently |
374 | * increment the count, they'll have to wait, and decrement it after |
375 | * seeing MNT_READONLY). |
376 | * |
377 | * It is OK to have counter incremented on one CPU and decremented on |
378 | * another: the sum will add up correctly. The danger would be when we |
379 | * sum up each counter, if we read a counter before it is incremented, |
380 | * but then read another CPU's count which it has been subsequently |
381 | * decremented from -- we would see more decrements than we should. |
382 | * MNT_WRITE_HOLD protects against this scenario, because |
383 | * mnt_want_write first increments count, then smp_mb, then spins on |
384 | * MNT_WRITE_HOLD, so it can't be decremented by another CPU while |
385 | * we're counting up here. |
386 | */ |
387 | if (count_mnt_writers(mnt) > 0) |
388 | ret = -EBUSY; |
389 | else |
390 | mnt->mnt_flags |= MNT_READONLY; |
391 | /* |
392 | * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers |
393 | * that become unheld will see MNT_READONLY. |
394 | */ |
395 | smp_wmb(); |
396 | mnt->mnt_flags &= ~MNT_WRITE_HOLD; |
397 | br_write_unlock(vfsmount_lock); |
398 | return ret; |
399 | } |
400 | |
401 | static void __mnt_unmake_readonly(struct vfsmount *mnt) |
402 | { |
403 | br_write_lock(vfsmount_lock); |
404 | mnt->mnt_flags &= ~MNT_READONLY; |
405 | br_write_unlock(vfsmount_lock); |
406 | } |
407 | |
408 | void simple_set_mnt(struct vfsmount *mnt, struct super_block *sb) |
409 | { |
410 | mnt->mnt_sb = sb; |
411 | mnt->mnt_root = dget(sb->s_root); |
412 | } |
413 | |
414 | EXPORT_SYMBOL(simple_set_mnt); |
415 | |
416 | void free_vfsmnt(struct vfsmount *mnt) |
417 | { |
418 | kfree(mnt->mnt_devname); |
419 | mnt_free_id(mnt); |
420 | #ifdef CONFIG_SMP |
421 | free_percpu(mnt->mnt_writers); |
422 | #endif |
423 | kmem_cache_free(mnt_cache, mnt); |
424 | } |
425 | |
426 | /* |
427 | * find the first or last mount at @dentry on vfsmount @mnt depending on |
428 | * @dir. If @dir is set return the first mount else return the last mount. |
429 | * vfsmount_lock must be held for read or write. |
430 | */ |
431 | struct vfsmount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry, |
432 | int dir) |
433 | { |
434 | struct list_head *head = mount_hashtable + hash(mnt, dentry); |
435 | struct list_head *tmp = head; |
436 | struct vfsmount *p, *found = NULL; |
437 | |
438 | for (;;) { |
439 | tmp = dir ? tmp->next : tmp->prev; |
440 | p = NULL; |
441 | if (tmp == head) |
442 | break; |
443 | p = list_entry(tmp, struct vfsmount, mnt_hash); |
444 | if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) { |
445 | found = p; |
446 | break; |
447 | } |
448 | } |
449 | return found; |
450 | } |
451 | |
452 | /* |
453 | * lookup_mnt increments the ref count before returning |
454 | * the vfsmount struct. |
455 | */ |
456 | struct vfsmount *lookup_mnt(struct path *path) |
457 | { |
458 | struct vfsmount *child_mnt; |
459 | |
460 | br_read_lock(vfsmount_lock); |
461 | if ((child_mnt = __lookup_mnt(path->mnt, path->dentry, 1))) |
462 | mntget(child_mnt); |
463 | br_read_unlock(vfsmount_lock); |
464 | return child_mnt; |
465 | } |
466 | |
467 | static inline int check_mnt(struct vfsmount *mnt) |
468 | { |
469 | return mnt->mnt_ns == current->nsproxy->mnt_ns; |
470 | } |
471 | |
472 | /* |
473 | * vfsmount lock must be held for write |
474 | */ |
475 | static void touch_mnt_namespace(struct mnt_namespace *ns) |
476 | { |
477 | if (ns) { |
478 | ns->event = ++event; |
479 | wake_up_interruptible(&ns->poll); |
480 | } |
481 | } |
482 | |
483 | /* |
484 | * vfsmount lock must be held for write |
485 | */ |
486 | static void __touch_mnt_namespace(struct mnt_namespace *ns) |
487 | { |
488 | if (ns && ns->event != event) { |
489 | ns->event = event; |
490 | wake_up_interruptible(&ns->poll); |
491 | } |
492 | } |
493 | |
494 | /* |
495 | * vfsmount lock must be held for write |
496 | */ |
497 | static void detach_mnt(struct vfsmount *mnt, struct path *old_path) |
498 | { |
499 | old_path->dentry = mnt->mnt_mountpoint; |
500 | old_path->mnt = mnt->mnt_parent; |
501 | mnt->mnt_parent = mnt; |
502 | mnt->mnt_mountpoint = mnt->mnt_root; |
503 | list_del_init(&mnt->mnt_child); |
504 | list_del_init(&mnt->mnt_hash); |
505 | old_path->dentry->d_mounted--; |
506 | } |
507 | |
508 | /* |
509 | * vfsmount lock must be held for write |
510 | */ |
511 | void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry, |
512 | struct vfsmount *child_mnt) |
513 | { |
514 | child_mnt->mnt_parent = mntget(mnt); |
515 | child_mnt->mnt_mountpoint = dget(dentry); |
516 | dentry->d_mounted++; |
517 | } |
518 | |
519 | /* |
520 | * vfsmount lock must be held for write |
521 | */ |
522 | static void attach_mnt(struct vfsmount *mnt, struct path *path) |
523 | { |
524 | mnt_set_mountpoint(path->mnt, path->dentry, mnt); |
525 | list_add_tail(&mnt->mnt_hash, mount_hashtable + |
526 | hash(path->mnt, path->dentry)); |
527 | list_add_tail(&mnt->mnt_child, &path->mnt->mnt_mounts); |
528 | } |
529 | |
530 | /* |
531 | * vfsmount lock must be held for write |
532 | */ |
533 | static void commit_tree(struct vfsmount *mnt) |
534 | { |
535 | struct vfsmount *parent = mnt->mnt_parent; |
536 | struct vfsmount *m; |
537 | LIST_HEAD(head); |
538 | struct mnt_namespace *n = parent->mnt_ns; |
539 | |
540 | BUG_ON(parent == mnt); |
541 | |
542 | list_add_tail(&head, &mnt->mnt_list); |
543 | list_for_each_entry(m, &head, mnt_list) |
544 | m->mnt_ns = n; |
545 | list_splice(&head, n->list.prev); |
546 | |
547 | list_add_tail(&mnt->mnt_hash, mount_hashtable + |
548 | hash(parent, mnt->mnt_mountpoint)); |
549 | list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); |
550 | touch_mnt_namespace(n); |
551 | } |
552 | |
553 | static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *root) |
554 | { |
555 | struct list_head *next = p->mnt_mounts.next; |
556 | if (next == &p->mnt_mounts) { |
557 | while (1) { |
558 | if (p == root) |
559 | return NULL; |
560 | next = p->mnt_child.next; |
561 | if (next != &p->mnt_parent->mnt_mounts) |
562 | break; |
563 | p = p->mnt_parent; |
564 | } |
565 | } |
566 | return list_entry(next, struct vfsmount, mnt_child); |
567 | } |
568 | |
569 | static struct vfsmount *skip_mnt_tree(struct vfsmount *p) |
570 | { |
571 | struct list_head *prev = p->mnt_mounts.prev; |
572 | while (prev != &p->mnt_mounts) { |
573 | p = list_entry(prev, struct vfsmount, mnt_child); |
574 | prev = p->mnt_mounts.prev; |
575 | } |
576 | return p; |
577 | } |
578 | |
579 | static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root, |
580 | int flag) |
581 | { |
582 | struct super_block *sb = old->mnt_sb; |
583 | struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname); |
584 | |
585 | if (mnt) { |
586 | if (flag & (CL_SLAVE | CL_PRIVATE)) |
587 | mnt->mnt_group_id = 0; /* not a peer of original */ |
588 | else |
589 | mnt->mnt_group_id = old->mnt_group_id; |
590 | |
591 | if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { |
592 | int err = mnt_alloc_group_id(mnt); |
593 | if (err) |
594 | goto out_free; |
595 | } |
596 | |
597 | mnt->mnt_flags = old->mnt_flags & ~MNT_WRITE_HOLD; |
598 | atomic_inc(&sb->s_active); |
599 | mnt->mnt_sb = sb; |
600 | mnt->mnt_root = dget(root); |
601 | mnt->mnt_mountpoint = mnt->mnt_root; |
602 | mnt->mnt_parent = mnt; |
603 | |
604 | if (flag & CL_SLAVE) { |
605 | list_add(&mnt->mnt_slave, &old->mnt_slave_list); |
606 | mnt->mnt_master = old; |
607 | CLEAR_MNT_SHARED(mnt); |
608 | } else if (!(flag & CL_PRIVATE)) { |
609 | if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old)) |
610 | list_add(&mnt->mnt_share, &old->mnt_share); |
611 | if (IS_MNT_SLAVE(old)) |
612 | list_add(&mnt->mnt_slave, &old->mnt_slave); |
613 | mnt->mnt_master = old->mnt_master; |
614 | } |
615 | if (flag & CL_MAKE_SHARED) |
616 | set_mnt_shared(mnt); |
617 | |
618 | /* stick the duplicate mount on the same expiry list |
619 | * as the original if that was on one */ |
620 | if (flag & CL_EXPIRE) { |
621 | if (!list_empty(&old->mnt_expire)) |
622 | list_add(&mnt->mnt_expire, &old->mnt_expire); |
623 | } |
624 | } |
625 | return mnt; |
626 | |
627 | out_free: |
628 | free_vfsmnt(mnt); |
629 | return NULL; |
630 | } |
631 | |
632 | static inline void __mntput(struct vfsmount *mnt) |
633 | { |
634 | struct super_block *sb = mnt->mnt_sb; |
635 | /* |
636 | * This probably indicates that somebody messed |
637 | * up a mnt_want/drop_write() pair. If this |
638 | * happens, the filesystem was probably unable |
639 | * to make r/w->r/o transitions. |
640 | */ |
641 | /* |
642 | * atomic_dec_and_lock() used to deal with ->mnt_count decrements |
643 | * provides barriers, so count_mnt_writers() below is safe. AV |
644 | */ |
645 | WARN_ON(count_mnt_writers(mnt)); |
646 | fsnotify_vfsmount_delete(mnt); |
647 | dput(mnt->mnt_root); |
648 | free_vfsmnt(mnt); |
649 | deactivate_super(sb); |
650 | } |
651 | |
652 | void mntput_no_expire(struct vfsmount *mnt) |
653 | { |
654 | repeat: |
655 | if (atomic_add_unless(&mnt->mnt_count, -1, 1)) |
656 | return; |
657 | br_write_lock(vfsmount_lock); |
658 | if (!atomic_dec_and_test(&mnt->mnt_count)) { |
659 | br_write_unlock(vfsmount_lock); |
660 | return; |
661 | } |
662 | if (likely(!mnt->mnt_pinned)) { |
663 | br_write_unlock(vfsmount_lock); |
664 | __mntput(mnt); |
665 | return; |
666 | } |
667 | atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count); |
668 | mnt->mnt_pinned = 0; |
669 | br_write_unlock(vfsmount_lock); |
670 | acct_auto_close_mnt(mnt); |
671 | goto repeat; |
672 | } |
673 | EXPORT_SYMBOL(mntput_no_expire); |
674 | |
675 | void mnt_pin(struct vfsmount *mnt) |
676 | { |
677 | br_write_lock(vfsmount_lock); |
678 | mnt->mnt_pinned++; |
679 | br_write_unlock(vfsmount_lock); |
680 | } |
681 | |
682 | EXPORT_SYMBOL(mnt_pin); |
683 | |
684 | void mnt_unpin(struct vfsmount *mnt) |
685 | { |
686 | br_write_lock(vfsmount_lock); |
687 | if (mnt->mnt_pinned) { |
688 | atomic_inc(&mnt->mnt_count); |
689 | mnt->mnt_pinned--; |
690 | } |
691 | br_write_unlock(vfsmount_lock); |
692 | } |
693 | |
694 | EXPORT_SYMBOL(mnt_unpin); |
695 | |
696 | static inline void mangle(struct seq_file *m, const char *s) |
697 | { |
698 | seq_escape(m, s, " \t\n\\"); |
699 | } |
700 | |
701 | /* |
702 | * Simple .show_options callback for filesystems which don't want to |
703 | * implement more complex mount option showing. |
704 | * |
705 | * See also save_mount_options(). |
706 | */ |
707 | int generic_show_options(struct seq_file *m, struct vfsmount *mnt) |
708 | { |
709 | const char *options; |
710 | |
711 | rcu_read_lock(); |
712 | options = rcu_dereference(mnt->mnt_sb->s_options); |
713 | |
714 | if (options != NULL && options[0]) { |
715 | seq_putc(m, ','); |
716 | mangle(m, options); |
717 | } |
718 | rcu_read_unlock(); |
719 | |
720 | return 0; |
721 | } |
722 | EXPORT_SYMBOL(generic_show_options); |
723 | |
724 | /* |
725 | * If filesystem uses generic_show_options(), this function should be |
726 | * called from the fill_super() callback. |
727 | * |
728 | * The .remount_fs callback usually needs to be handled in a special |
729 | * way, to make sure, that previous options are not overwritten if the |
730 | * remount fails. |
731 | * |
732 | * Also note, that if the filesystem's .remount_fs function doesn't |
733 | * reset all options to their default value, but changes only newly |
734 | * given options, then the displayed options will not reflect reality |
735 | * any more. |
736 | */ |
737 | void save_mount_options(struct super_block *sb, char *options) |
738 | { |
739 | BUG_ON(sb->s_options); |
740 | rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL)); |
741 | } |
742 | EXPORT_SYMBOL(save_mount_options); |
743 | |
744 | void replace_mount_options(struct super_block *sb, char *options) |
745 | { |
746 | char *old = sb->s_options; |
747 | rcu_assign_pointer(sb->s_options, options); |
748 | if (old) { |
749 | synchronize_rcu(); |
750 | kfree(old); |
751 | } |
752 | } |
753 | EXPORT_SYMBOL(replace_mount_options); |
754 | |
755 | #ifdef CONFIG_PROC_FS |
756 | /* iterator */ |
757 | static void *m_start(struct seq_file *m, loff_t *pos) |
758 | { |
759 | struct proc_mounts *p = m->private; |
760 | |
761 | down_read(&namespace_sem); |
762 | return seq_list_start(&p->ns->list, *pos); |
763 | } |
764 | |
765 | static void *m_next(struct seq_file *m, void *v, loff_t *pos) |
766 | { |
767 | struct proc_mounts *p = m->private; |
768 | |
769 | return seq_list_next(v, &p->ns->list, pos); |
770 | } |
771 | |
772 | static void m_stop(struct seq_file *m, void *v) |
773 | { |
774 | up_read(&namespace_sem); |
775 | } |
776 | |
777 | int mnt_had_events(struct proc_mounts *p) |
778 | { |
779 | struct mnt_namespace *ns = p->ns; |
780 | int res = 0; |
781 | |
782 | br_read_lock(vfsmount_lock); |
783 | if (p->event != ns->event) { |
784 | p->event = ns->event; |
785 | res = 1; |
786 | } |
787 | br_read_unlock(vfsmount_lock); |
788 | |
789 | return res; |
790 | } |
791 | |
792 | struct proc_fs_info { |
793 | int flag; |
794 | const char *str; |
795 | }; |
796 | |
797 | static int show_sb_opts(struct seq_file *m, struct super_block *sb) |
798 | { |
799 | static const struct proc_fs_info fs_info[] = { |
800 | { MS_SYNCHRONOUS, ",sync" }, |
801 | { MS_DIRSYNC, ",dirsync" }, |
802 | { MS_MANDLOCK, ",mand" }, |
803 | { 0, NULL } |
804 | }; |
805 | const struct proc_fs_info *fs_infop; |
806 | |
807 | for (fs_infop = fs_info; fs_infop->flag; fs_infop++) { |
808 | if (sb->s_flags & fs_infop->flag) |
809 | seq_puts(m, fs_infop->str); |
810 | } |
811 | |
812 | return security_sb_show_options(m, sb); |
813 | } |
814 | |
815 | static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt) |
816 | { |
817 | static const struct proc_fs_info mnt_info[] = { |
818 | { MNT_NOSUID, ",nosuid" }, |
819 | { MNT_NODEV, ",nodev" }, |
820 | { MNT_NOEXEC, ",noexec" }, |
821 | { MNT_NOATIME, ",noatime" }, |
822 | { MNT_NODIRATIME, ",nodiratime" }, |
823 | { MNT_RELATIME, ",relatime" }, |
824 | { 0, NULL } |
825 | }; |
826 | const struct proc_fs_info *fs_infop; |
827 | |
828 | for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) { |
829 | if (mnt->mnt_flags & fs_infop->flag) |
830 | seq_puts(m, fs_infop->str); |
831 | } |
832 | } |
833 | |
834 | static void show_type(struct seq_file *m, struct super_block *sb) |
835 | { |
836 | mangle(m, sb->s_type->name); |
837 | if (sb->s_subtype && sb->s_subtype[0]) { |
838 | seq_putc(m, '.'); |
839 | mangle(m, sb->s_subtype); |
840 | } |
841 | } |
842 | |
843 | static int show_vfsmnt(struct seq_file *m, void *v) |
844 | { |
845 | struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); |
846 | int err = 0; |
847 | struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt }; |
848 | |
849 | mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none"); |
850 | seq_putc(m, ' '); |
851 | seq_path(m, &mnt_path, " \t\n\\"); |
852 | seq_putc(m, ' '); |
853 | show_type(m, mnt->mnt_sb); |
854 | seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw"); |
855 | err = show_sb_opts(m, mnt->mnt_sb); |
856 | if (err) |
857 | goto out; |
858 | show_mnt_opts(m, mnt); |
859 | if (mnt->mnt_sb->s_op->show_options) |
860 | err = mnt->mnt_sb->s_op->show_options(m, mnt); |
861 | seq_puts(m, " 0 0\n"); |
862 | out: |
863 | return err; |
864 | } |
865 | |
866 | const struct seq_operations mounts_op = { |
867 | .start = m_start, |
868 | .next = m_next, |
869 | .stop = m_stop, |
870 | .show = show_vfsmnt |
871 | }; |
872 | |
873 | static int show_mountinfo(struct seq_file *m, void *v) |
874 | { |
875 | struct proc_mounts *p = m->private; |
876 | struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); |
877 | struct super_block *sb = mnt->mnt_sb; |
878 | struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt }; |
879 | struct path root = p->root; |
880 | int err = 0; |
881 | |
882 | seq_printf(m, "%i %i %u:%u ", mnt->mnt_id, mnt->mnt_parent->mnt_id, |
883 | MAJOR(sb->s_dev), MINOR(sb->s_dev)); |
884 | seq_dentry(m, mnt->mnt_root, " \t\n\\"); |
885 | seq_putc(m, ' '); |
886 | seq_path_root(m, &mnt_path, &root, " \t\n\\"); |
887 | if (root.mnt != p->root.mnt || root.dentry != p->root.dentry) { |
888 | /* |
889 | * Mountpoint is outside root, discard that one. Ugly, |
890 | * but less so than trying to do that in iterator in a |
891 | * race-free way (due to renames). |
892 | */ |
893 | return SEQ_SKIP; |
894 | } |
895 | seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw"); |
896 | show_mnt_opts(m, mnt); |
897 | |
898 | /* Tagged fields ("foo:X" or "bar") */ |
899 | if (IS_MNT_SHARED(mnt)) |
900 | seq_printf(m, " shared:%i", mnt->mnt_group_id); |
901 | if (IS_MNT_SLAVE(mnt)) { |
902 | int master = mnt->mnt_master->mnt_group_id; |
903 | int dom = get_dominating_id(mnt, &p->root); |
904 | seq_printf(m, " master:%i", master); |
905 | if (dom && dom != master) |
906 | seq_printf(m, " propagate_from:%i", dom); |
907 | } |
908 | if (IS_MNT_UNBINDABLE(mnt)) |
909 | seq_puts(m, " unbindable"); |
910 | |
911 | /* Filesystem specific data */ |
912 | seq_puts(m, " - "); |
913 | show_type(m, sb); |
914 | seq_putc(m, ' '); |
915 | mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none"); |
916 | seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw"); |
917 | err = show_sb_opts(m, sb); |
918 | if (err) |
919 | goto out; |
920 | if (sb->s_op->show_options) |
921 | err = sb->s_op->show_options(m, mnt); |
922 | seq_putc(m, '\n'); |
923 | out: |
924 | return err; |
925 | } |
926 | |
927 | const struct seq_operations mountinfo_op = { |
928 | .start = m_start, |
929 | .next = m_next, |
930 | .stop = m_stop, |
931 | .show = show_mountinfo, |
932 | }; |
933 | |
934 | static int show_vfsstat(struct seq_file *m, void *v) |
935 | { |
936 | struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); |
937 | struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt }; |
938 | int err = 0; |
939 | |
940 | /* device */ |
941 | if (mnt->mnt_devname) { |
942 | seq_puts(m, "device "); |
943 | mangle(m, mnt->mnt_devname); |
944 | } else |
945 | seq_puts(m, "no device"); |
946 | |
947 | /* mount point */ |
948 | seq_puts(m, " mounted on "); |
949 | seq_path(m, &mnt_path, " \t\n\\"); |
950 | seq_putc(m, ' '); |
951 | |
952 | /* file system type */ |
953 | seq_puts(m, "with fstype "); |
954 | show_type(m, mnt->mnt_sb); |
955 | |
956 | /* optional statistics */ |
957 | if (mnt->mnt_sb->s_op->show_stats) { |
958 | seq_putc(m, ' '); |
959 | err = mnt->mnt_sb->s_op->show_stats(m, mnt); |
960 | } |
961 | |
962 | seq_putc(m, '\n'); |
963 | return err; |
964 | } |
965 | |
966 | const struct seq_operations mountstats_op = { |
967 | .start = m_start, |
968 | .next = m_next, |
969 | .stop = m_stop, |
970 | .show = show_vfsstat, |
971 | }; |
972 | #endif /* CONFIG_PROC_FS */ |
973 | |
974 | /** |
975 | * may_umount_tree - check if a mount tree is busy |
976 | * @mnt: root of mount tree |
977 | * |
978 | * This is called to check if a tree of mounts has any |
979 | * open files, pwds, chroots or sub mounts that are |
980 | * busy. |
981 | */ |
982 | int may_umount_tree(struct vfsmount *mnt) |
983 | { |
984 | int actual_refs = 0; |
985 | int minimum_refs = 0; |
986 | struct vfsmount *p; |
987 | |
988 | br_read_lock(vfsmount_lock); |
989 | for (p = mnt; p; p = next_mnt(p, mnt)) { |
990 | actual_refs += atomic_read(&p->mnt_count); |
991 | minimum_refs += 2; |
992 | } |
993 | br_read_unlock(vfsmount_lock); |
994 | |
995 | if (actual_refs > minimum_refs) |
996 | return 0; |
997 | |
998 | return 1; |
999 | } |
1000 | |
1001 | EXPORT_SYMBOL(may_umount_tree); |
1002 | |
1003 | /** |
1004 | * may_umount - check if a mount point is busy |
1005 | * @mnt: root of mount |
1006 | * |
1007 | * This is called to check if a mount point has any |
1008 | * open files, pwds, chroots or sub mounts. If the |
1009 | * mount has sub mounts this will return busy |
1010 | * regardless of whether the sub mounts are busy. |
1011 | * |
1012 | * Doesn't take quota and stuff into account. IOW, in some cases it will |
1013 | * give false negatives. The main reason why it's here is that we need |
1014 | * a non-destructive way to look for easily umountable filesystems. |
1015 | */ |
1016 | int may_umount(struct vfsmount *mnt) |
1017 | { |
1018 | int ret = 1; |
1019 | down_read(&namespace_sem); |
1020 | br_read_lock(vfsmount_lock); |
1021 | if (propagate_mount_busy(mnt, 2)) |
1022 | ret = 0; |
1023 | br_read_unlock(vfsmount_lock); |
1024 | up_read(&namespace_sem); |
1025 | return ret; |
1026 | } |
1027 | |
1028 | EXPORT_SYMBOL(may_umount); |
1029 | |
1030 | void release_mounts(struct list_head *head) |
1031 | { |
1032 | struct vfsmount *mnt; |
1033 | while (!list_empty(head)) { |
1034 | mnt = list_first_entry(head, struct vfsmount, mnt_hash); |
1035 | list_del_init(&mnt->mnt_hash); |
1036 | if (mnt->mnt_parent != mnt) { |
1037 | struct dentry *dentry; |
1038 | struct vfsmount *m; |
1039 | |
1040 | br_write_lock(vfsmount_lock); |
1041 | dentry = mnt->mnt_mountpoint; |
1042 | m = mnt->mnt_parent; |
1043 | mnt->mnt_mountpoint = mnt->mnt_root; |
1044 | mnt->mnt_parent = mnt; |
1045 | m->mnt_ghosts--; |
1046 | br_write_unlock(vfsmount_lock); |
1047 | dput(dentry); |
1048 | mntput(m); |
1049 | } |
1050 | mntput(mnt); |
1051 | } |
1052 | } |
1053 | |
1054 | /* |
1055 | * vfsmount lock must be held for write |
1056 | * namespace_sem must be held for write |
1057 | */ |
1058 | void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill) |
1059 | { |
1060 | struct vfsmount *p; |
1061 | |
1062 | for (p = mnt; p; p = next_mnt(p, mnt)) |
1063 | list_move(&p->mnt_hash, kill); |
1064 | |
1065 | if (propagate) |
1066 | propagate_umount(kill); |
1067 | |
1068 | list_for_each_entry(p, kill, mnt_hash) { |
1069 | list_del_init(&p->mnt_expire); |
1070 | list_del_init(&p->mnt_list); |
1071 | __touch_mnt_namespace(p->mnt_ns); |
1072 | p->mnt_ns = NULL; |
1073 | list_del_init(&p->mnt_child); |
1074 | if (p->mnt_parent != p) { |
1075 | p->mnt_parent->mnt_ghosts++; |
1076 | p->mnt_mountpoint->d_mounted--; |
1077 | } |
1078 | change_mnt_propagation(p, MS_PRIVATE); |
1079 | } |
1080 | } |
1081 | |
1082 | static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts); |
1083 | |
1084 | static int do_umount(struct vfsmount *mnt, int flags) |
1085 | { |
1086 | struct super_block *sb = mnt->mnt_sb; |
1087 | int retval; |
1088 | LIST_HEAD(umount_list); |
1089 | |
1090 | retval = security_sb_umount(mnt, flags); |
1091 | if (retval) |
1092 | return retval; |
1093 | |
1094 | /* |
1095 | * Allow userspace to request a mountpoint be expired rather than |
1096 | * unmounting unconditionally. Unmount only happens if: |
1097 | * (1) the mark is already set (the mark is cleared by mntput()) |
1098 | * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] |
1099 | */ |
1100 | if (flags & MNT_EXPIRE) { |
1101 | if (mnt == current->fs->root.mnt || |
1102 | flags & (MNT_FORCE | MNT_DETACH)) |
1103 | return -EINVAL; |
1104 | |
1105 | if (atomic_read(&mnt->mnt_count) != 2) |
1106 | return -EBUSY; |
1107 | |
1108 | if (!xchg(&mnt->mnt_expiry_mark, 1)) |
1109 | return -EAGAIN; |
1110 | } |
1111 | |
1112 | /* |
1113 | * If we may have to abort operations to get out of this |
1114 | * mount, and they will themselves hold resources we must |
1115 | * allow the fs to do things. In the Unix tradition of |
1116 | * 'Gee thats tricky lets do it in userspace' the umount_begin |
1117 | * might fail to complete on the first run through as other tasks |
1118 | * must return, and the like. Thats for the mount program to worry |
1119 | * about for the moment. |
1120 | */ |
1121 | |
1122 | if (flags & MNT_FORCE && sb->s_op->umount_begin) { |
1123 | sb->s_op->umount_begin(sb); |
1124 | } |
1125 | |
1126 | /* |
1127 | * No sense to grab the lock for this test, but test itself looks |
1128 | * somewhat bogus. Suggestions for better replacement? |
1129 | * Ho-hum... In principle, we might treat that as umount + switch |
1130 | * to rootfs. GC would eventually take care of the old vfsmount. |
1131 | * Actually it makes sense, especially if rootfs would contain a |
1132 | * /reboot - static binary that would close all descriptors and |
1133 | * call reboot(9). Then init(8) could umount root and exec /reboot. |
1134 | */ |
1135 | if (mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { |
1136 | /* |
1137 | * Special case for "unmounting" root ... |
1138 | * we just try to remount it readonly. |
1139 | */ |
1140 | down_write(&sb->s_umount); |
1141 | if (!(sb->s_flags & MS_RDONLY)) |
1142 | retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); |
1143 | up_write(&sb->s_umount); |
1144 | return retval; |
1145 | } |
1146 | |
1147 | down_write(&namespace_sem); |
1148 | br_write_lock(vfsmount_lock); |
1149 | event++; |
1150 | |
1151 | if (!(flags & MNT_DETACH)) |
1152 | shrink_submounts(mnt, &umount_list); |
1153 | |
1154 | retval = -EBUSY; |
1155 | if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) { |
1156 | if (!list_empty(&mnt->mnt_list)) |
1157 | umount_tree(mnt, 1, &umount_list); |
1158 | retval = 0; |
1159 | } |
1160 | br_write_unlock(vfsmount_lock); |
1161 | up_write(&namespace_sem); |
1162 | release_mounts(&umount_list); |
1163 | return retval; |
1164 | } |
1165 | |
1166 | /* |
1167 | * Now umount can handle mount points as well as block devices. |
1168 | * This is important for filesystems which use unnamed block devices. |
1169 | * |
1170 | * We now support a flag for forced unmount like the other 'big iron' |
1171 | * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD |
1172 | */ |
1173 | |
1174 | SYSCALL_DEFINE2(umount, char __user *, name, int, flags) |
1175 | { |
1176 | struct path path; |
1177 | int retval; |
1178 | int lookup_flags = 0; |
1179 | |
1180 | if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) |
1181 | return -EINVAL; |
1182 | |
1183 | if (!(flags & UMOUNT_NOFOLLOW)) |
1184 | lookup_flags |= LOOKUP_FOLLOW; |
1185 | |
1186 | retval = user_path_at(AT_FDCWD, name, lookup_flags, &path); |
1187 | if (retval) |
1188 | goto out; |
1189 | retval = -EINVAL; |
1190 | if (path.dentry != path.mnt->mnt_root) |
1191 | goto dput_and_out; |
1192 | if (!check_mnt(path.mnt)) |
1193 | goto dput_and_out; |
1194 | |
1195 | retval = -EPERM; |
1196 | if (!capable(CAP_SYS_ADMIN)) |
1197 | goto dput_and_out; |
1198 | |
1199 | retval = do_umount(path.mnt, flags); |
1200 | dput_and_out: |
1201 | /* we mustn't call path_put() as that would clear mnt_expiry_mark */ |
1202 | dput(path.dentry); |
1203 | mntput_no_expire(path.mnt); |
1204 | out: |
1205 | return retval; |
1206 | } |
1207 | |
1208 | #ifdef __ARCH_WANT_SYS_OLDUMOUNT |
1209 | |
1210 | /* |
1211 | * The 2.0 compatible umount. No flags. |
1212 | */ |
1213 | SYSCALL_DEFINE1(oldumount, char __user *, name) |
1214 | { |
1215 | return sys_umount(name, 0); |
1216 | } |
1217 | |
1218 | #endif |
1219 | |
1220 | static int mount_is_safe(struct path *path) |
1221 | { |
1222 | if (capable(CAP_SYS_ADMIN)) |
1223 | return 0; |
1224 | return -EPERM; |
1225 | #ifdef notyet |
1226 | if (S_ISLNK(path->dentry->d_inode->i_mode)) |
1227 | return -EPERM; |
1228 | if (path->dentry->d_inode->i_mode & S_ISVTX) { |
1229 | if (current_uid() != path->dentry->d_inode->i_uid) |
1230 | return -EPERM; |
1231 | } |
1232 | if (inode_permission(path->dentry->d_inode, MAY_WRITE)) |
1233 | return -EPERM; |
1234 | return 0; |
1235 | #endif |
1236 | } |
1237 | |
1238 | struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, |
1239 | int flag) |
1240 | { |
1241 | struct vfsmount *res, *p, *q, *r, *s; |
1242 | struct path path; |
1243 | |
1244 | if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt)) |
1245 | return NULL; |
1246 | |
1247 | res = q = clone_mnt(mnt, dentry, flag); |
1248 | if (!q) |
1249 | goto Enomem; |
1250 | q->mnt_mountpoint = mnt->mnt_mountpoint; |
1251 | |
1252 | p = mnt; |
1253 | list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { |
1254 | if (!is_subdir(r->mnt_mountpoint, dentry)) |
1255 | continue; |
1256 | |
1257 | for (s = r; s; s = next_mnt(s, r)) { |
1258 | if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) { |
1259 | s = skip_mnt_tree(s); |
1260 | continue; |
1261 | } |
1262 | while (p != s->mnt_parent) { |
1263 | p = p->mnt_parent; |
1264 | q = q->mnt_parent; |
1265 | } |
1266 | p = s; |
1267 | path.mnt = q; |
1268 | path.dentry = p->mnt_mountpoint; |
1269 | q = clone_mnt(p, p->mnt_root, flag); |
1270 | if (!q) |
1271 | goto Enomem; |
1272 | br_write_lock(vfsmount_lock); |
1273 | list_add_tail(&q->mnt_list, &res->mnt_list); |
1274 | attach_mnt(q, &path); |
1275 | br_write_unlock(vfsmount_lock); |
1276 | } |
1277 | } |
1278 | return res; |
1279 | Enomem: |
1280 | if (res) { |
1281 | LIST_HEAD(umount_list); |
1282 | br_write_lock(vfsmount_lock); |
1283 | umount_tree(res, 0, &umount_list); |
1284 | br_write_unlock(vfsmount_lock); |
1285 | release_mounts(&umount_list); |
1286 | } |
1287 | return NULL; |
1288 | } |
1289 | |
1290 | struct vfsmount *collect_mounts(struct path *path) |
1291 | { |
1292 | struct vfsmount *tree; |
1293 | down_write(&namespace_sem); |
1294 | tree = copy_tree(path->mnt, path->dentry, CL_COPY_ALL | CL_PRIVATE); |
1295 | up_write(&namespace_sem); |
1296 | return tree; |
1297 | } |
1298 | |
1299 | void drop_collected_mounts(struct vfsmount *mnt) |
1300 | { |
1301 | LIST_HEAD(umount_list); |
1302 | down_write(&namespace_sem); |
1303 | br_write_lock(vfsmount_lock); |
1304 | umount_tree(mnt, 0, &umount_list); |
1305 | br_write_unlock(vfsmount_lock); |
1306 | up_write(&namespace_sem); |
1307 | release_mounts(&umount_list); |
1308 | } |
1309 | |
1310 | int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, |
1311 | struct vfsmount *root) |
1312 | { |
1313 | struct vfsmount *mnt; |
1314 | int res = f(root, arg); |
1315 | if (res) |
1316 | return res; |
1317 | list_for_each_entry(mnt, &root->mnt_list, mnt_list) { |
1318 | res = f(mnt, arg); |
1319 | if (res) |
1320 | return res; |
1321 | } |
1322 | return 0; |
1323 | } |
1324 | |
1325 | static void cleanup_group_ids(struct vfsmount *mnt, struct vfsmount *end) |
1326 | { |
1327 | struct vfsmount *p; |
1328 | |
1329 | for (p = mnt; p != end; p = next_mnt(p, mnt)) { |
1330 | if (p->mnt_group_id && !IS_MNT_SHARED(p)) |
1331 | mnt_release_group_id(p); |
1332 | } |
1333 | } |
1334 | |
1335 | static int invent_group_ids(struct vfsmount *mnt, bool recurse) |
1336 | { |
1337 | struct vfsmount *p; |
1338 | |
1339 | for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { |
1340 | if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { |
1341 | int err = mnt_alloc_group_id(p); |
1342 | if (err) { |
1343 | cleanup_group_ids(mnt, p); |
1344 | return err; |
1345 | } |
1346 | } |
1347 | } |
1348 | |
1349 | return 0; |
1350 | } |
1351 | |
1352 | /* |
1353 | * @source_mnt : mount tree to be attached |
1354 | * @nd : place the mount tree @source_mnt is attached |
1355 | * @parent_nd : if non-null, detach the source_mnt from its parent and |
1356 | * store the parent mount and mountpoint dentry. |
1357 | * (done when source_mnt is moved) |
1358 | * |
1359 | * NOTE: in the table below explains the semantics when a source mount |
1360 | * of a given type is attached to a destination mount of a given type. |
1361 | * --------------------------------------------------------------------------- |
1362 | * | BIND MOUNT OPERATION | |
1363 | * |************************************************************************** |
1364 | * | source-->| shared | private | slave | unbindable | |
1365 | * | dest | | | | | |
1366 | * | | | | | | | |
1367 | * | v | | | | | |
1368 | * |************************************************************************** |
1369 | * | shared | shared (++) | shared (+) | shared(+++)| invalid | |
1370 | * | | | | | | |
1371 | * |non-shared| shared (+) | private | slave (*) | invalid | |
1372 | * *************************************************************************** |
1373 | * A bind operation clones the source mount and mounts the clone on the |
1374 | * destination mount. |
1375 | * |
1376 | * (++) the cloned mount is propagated to all the mounts in the propagation |
1377 | * tree of the destination mount and the cloned mount is added to |
1378 | * the peer group of the source mount. |
1379 | * (+) the cloned mount is created under the destination mount and is marked |
1380 | * as shared. The cloned mount is added to the peer group of the source |
1381 | * mount. |
1382 | * (+++) the mount is propagated to all the mounts in the propagation tree |
1383 | * of the destination mount and the cloned mount is made slave |
1384 | * of the same master as that of the source mount. The cloned mount |
1385 | * is marked as 'shared and slave'. |
1386 | * (*) the cloned mount is made a slave of the same master as that of the |
1387 | * source mount. |
1388 | * |
1389 | * --------------------------------------------------------------------------- |
1390 | * | MOVE MOUNT OPERATION | |
1391 | * |************************************************************************** |
1392 | * | source-->| shared | private | slave | unbindable | |
1393 | * | dest | | | | | |
1394 | * | | | | | | | |
1395 | * | v | | | | | |
1396 | * |************************************************************************** |
1397 | * | shared | shared (+) | shared (+) | shared(+++) | invalid | |
1398 | * | | | | | | |
1399 | * |non-shared| shared (+*) | private | slave (*) | unbindable | |
1400 | * *************************************************************************** |
1401 | * |
1402 | * (+) the mount is moved to the destination. And is then propagated to |
1403 | * all the mounts in the propagation tree of the destination mount. |
1404 | * (+*) the mount is moved to the destination. |
1405 | * (+++) the mount is moved to the destination and is then propagated to |
1406 | * all the mounts belonging to the destination mount's propagation tree. |
1407 | * the mount is marked as 'shared and slave'. |
1408 | * (*) the mount continues to be a slave at the new location. |
1409 | * |
1410 | * if the source mount is a tree, the operations explained above is |
1411 | * applied to each mount in the tree. |
1412 | * Must be called without spinlocks held, since this function can sleep |
1413 | * in allocations. |
1414 | */ |
1415 | static int attach_recursive_mnt(struct vfsmount *source_mnt, |
1416 | struct path *path, struct path *parent_path) |
1417 | { |
1418 | LIST_HEAD(tree_list); |
1419 | struct vfsmount *dest_mnt = path->mnt; |
1420 | struct dentry *dest_dentry = path->dentry; |
1421 | struct vfsmount *child, *p; |
1422 | int err; |
1423 | |
1424 | if (IS_MNT_SHARED(dest_mnt)) { |
1425 | err = invent_group_ids(source_mnt, true); |
1426 | if (err) |
1427 | goto out; |
1428 | } |
1429 | err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list); |
1430 | if (err) |
1431 | goto out_cleanup_ids; |
1432 | |
1433 | br_write_lock(vfsmount_lock); |
1434 | |
1435 | if (IS_MNT_SHARED(dest_mnt)) { |
1436 | for (p = source_mnt; p; p = next_mnt(p, source_mnt)) |
1437 | set_mnt_shared(p); |
1438 | } |
1439 | if (parent_path) { |
1440 | detach_mnt(source_mnt, parent_path); |
1441 | attach_mnt(source_mnt, path); |
1442 | touch_mnt_namespace(parent_path->mnt->mnt_ns); |
1443 | } else { |
1444 | mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt); |
1445 | commit_tree(source_mnt); |
1446 | } |
1447 | |
1448 | list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { |
1449 | list_del_init(&child->mnt_hash); |
1450 | commit_tree(child); |
1451 | } |
1452 | br_write_unlock(vfsmount_lock); |
1453 | |
1454 | return 0; |
1455 | |
1456 | out_cleanup_ids: |
1457 | if (IS_MNT_SHARED(dest_mnt)) |
1458 | cleanup_group_ids(source_mnt, NULL); |
1459 | out: |
1460 | return err; |
1461 | } |
1462 | |
1463 | static int graft_tree(struct vfsmount *mnt, struct path *path) |
1464 | { |
1465 | int err; |
1466 | if (mnt->mnt_sb->s_flags & MS_NOUSER) |
1467 | return -EINVAL; |
1468 | |
1469 | if (S_ISDIR(path->dentry->d_inode->i_mode) != |
1470 | S_ISDIR(mnt->mnt_root->d_inode->i_mode)) |
1471 | return -ENOTDIR; |
1472 | |
1473 | err = -ENOENT; |
1474 | mutex_lock(&path->dentry->d_inode->i_mutex); |
1475 | if (cant_mount(path->dentry)) |
1476 | goto out_unlock; |
1477 | |
1478 | if (!d_unlinked(path->dentry)) |
1479 | err = attach_recursive_mnt(mnt, path, NULL); |
1480 | out_unlock: |
1481 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
1482 | return err; |
1483 | } |
1484 | |
1485 | /* |
1486 | * Sanity check the flags to change_mnt_propagation. |
1487 | */ |
1488 | |
1489 | static int flags_to_propagation_type(int flags) |
1490 | { |
1491 | int type = flags & ~MS_REC; |
1492 | |
1493 | /* Fail if any non-propagation flags are set */ |
1494 | if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
1495 | return 0; |
1496 | /* Only one propagation flag should be set */ |
1497 | if (!is_power_of_2(type)) |
1498 | return 0; |
1499 | return type; |
1500 | } |
1501 | |
1502 | /* |
1503 | * recursively change the type of the mountpoint. |
1504 | */ |
1505 | static int do_change_type(struct path *path, int flag) |
1506 | { |
1507 | struct vfsmount *m, *mnt = path->mnt; |
1508 | int recurse = flag & MS_REC; |
1509 | int type; |
1510 | int err = 0; |
1511 | |
1512 | if (!capable(CAP_SYS_ADMIN)) |
1513 | return -EPERM; |
1514 | |
1515 | if (path->dentry != path->mnt->mnt_root) |
1516 | return -EINVAL; |
1517 | |
1518 | type = flags_to_propagation_type(flag); |
1519 | if (!type) |
1520 | return -EINVAL; |
1521 | |
1522 | down_write(&namespace_sem); |
1523 | if (type == MS_SHARED) { |
1524 | err = invent_group_ids(mnt, recurse); |
1525 | if (err) |
1526 | goto out_unlock; |
1527 | } |
1528 | |
1529 | br_write_lock(vfsmount_lock); |
1530 | for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) |
1531 | change_mnt_propagation(m, type); |
1532 | br_write_unlock(vfsmount_lock); |
1533 | |
1534 | out_unlock: |
1535 | up_write(&namespace_sem); |
1536 | return err; |
1537 | } |
1538 | |
1539 | /* |
1540 | * do loopback mount. |
1541 | */ |
1542 | static int do_loopback(struct path *path, char *old_name, |
1543 | int recurse) |
1544 | { |
1545 | struct path old_path; |
1546 | struct vfsmount *mnt = NULL; |
1547 | int err = mount_is_safe(path); |
1548 | if (err) |
1549 | return err; |
1550 | if (!old_name || !*old_name) |
1551 | return -EINVAL; |
1552 | err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); |
1553 | if (err) |
1554 | return err; |
1555 | |
1556 | down_write(&namespace_sem); |
1557 | err = -EINVAL; |
1558 | if (IS_MNT_UNBINDABLE(old_path.mnt)) |
1559 | goto out; |
1560 | |
1561 | if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt)) |
1562 | goto out; |
1563 | |
1564 | err = -ENOMEM; |
1565 | if (recurse) |
1566 | mnt = copy_tree(old_path.mnt, old_path.dentry, 0); |
1567 | else |
1568 | mnt = clone_mnt(old_path.mnt, old_path.dentry, 0); |
1569 | |
1570 | if (!mnt) |
1571 | goto out; |
1572 | |
1573 | err = graft_tree(mnt, path); |
1574 | if (err) { |
1575 | LIST_HEAD(umount_list); |
1576 | |
1577 | br_write_lock(vfsmount_lock); |
1578 | umount_tree(mnt, 0, &umount_list); |
1579 | br_write_unlock(vfsmount_lock); |
1580 | release_mounts(&umount_list); |
1581 | } |
1582 | |
1583 | out: |
1584 | up_write(&namespace_sem); |
1585 | path_put(&old_path); |
1586 | return err; |
1587 | } |
1588 | |
1589 | static int change_mount_flags(struct vfsmount *mnt, int ms_flags) |
1590 | { |
1591 | int error = 0; |
1592 | int readonly_request = 0; |
1593 | |
1594 | if (ms_flags & MS_RDONLY) |
1595 | readonly_request = 1; |
1596 | if (readonly_request == __mnt_is_readonly(mnt)) |
1597 | return 0; |
1598 | |
1599 | if (readonly_request) |
1600 | error = mnt_make_readonly(mnt); |
1601 | else |
1602 | __mnt_unmake_readonly(mnt); |
1603 | return error; |
1604 | } |
1605 | |
1606 | /* |
1607 | * change filesystem flags. dir should be a physical root of filesystem. |
1608 | * If you've mounted a non-root directory somewhere and want to do remount |
1609 | * on it - tough luck. |
1610 | */ |
1611 | static int do_remount(struct path *path, int flags, int mnt_flags, |
1612 | void *data) |
1613 | { |
1614 | int err; |
1615 | struct super_block *sb = path->mnt->mnt_sb; |
1616 | |
1617 | if (!capable(CAP_SYS_ADMIN)) |
1618 | return -EPERM; |
1619 | |
1620 | if (!check_mnt(path->mnt)) |
1621 | return -EINVAL; |
1622 | |
1623 | if (path->dentry != path->mnt->mnt_root) |
1624 | return -EINVAL; |
1625 | |
1626 | down_write(&sb->s_umount); |
1627 | if (flags & MS_BIND) |
1628 | err = change_mount_flags(path->mnt, flags); |
1629 | else |
1630 | err = do_remount_sb(sb, flags, data, 0); |
1631 | if (!err) { |
1632 | br_write_lock(vfsmount_lock); |
1633 | mnt_flags |= path->mnt->mnt_flags & MNT_PROPAGATION_MASK; |
1634 | path->mnt->mnt_flags = mnt_flags; |
1635 | br_write_unlock(vfsmount_lock); |
1636 | } |
1637 | up_write(&sb->s_umount); |
1638 | if (!err) { |
1639 | br_write_lock(vfsmount_lock); |
1640 | touch_mnt_namespace(path->mnt->mnt_ns); |
1641 | br_write_unlock(vfsmount_lock); |
1642 | } |
1643 | return err; |
1644 | } |
1645 | |
1646 | static inline int tree_contains_unbindable(struct vfsmount *mnt) |
1647 | { |
1648 | struct vfsmount *p; |
1649 | for (p = mnt; p; p = next_mnt(p, mnt)) { |
1650 | if (IS_MNT_UNBINDABLE(p)) |
1651 | return 1; |
1652 | } |
1653 | return 0; |
1654 | } |
1655 | |
1656 | static int do_move_mount(struct path *path, char *old_name) |
1657 | { |
1658 | struct path old_path, parent_path; |
1659 | struct vfsmount *p; |
1660 | int err = 0; |
1661 | if (!capable(CAP_SYS_ADMIN)) |
1662 | return -EPERM; |
1663 | if (!old_name || !*old_name) |
1664 | return -EINVAL; |
1665 | err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); |
1666 | if (err) |
1667 | return err; |
1668 | |
1669 | down_write(&namespace_sem); |
1670 | while (d_mountpoint(path->dentry) && |
1671 | follow_down(path)) |
1672 | ; |
1673 | err = -EINVAL; |
1674 | if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt)) |
1675 | goto out; |
1676 | |
1677 | err = -ENOENT; |
1678 | mutex_lock(&path->dentry->d_inode->i_mutex); |
1679 | if (cant_mount(path->dentry)) |
1680 | goto out1; |
1681 | |
1682 | if (d_unlinked(path->dentry)) |
1683 | goto out1; |
1684 | |
1685 | err = -EINVAL; |
1686 | if (old_path.dentry != old_path.mnt->mnt_root) |
1687 | goto out1; |
1688 | |
1689 | if (old_path.mnt == old_path.mnt->mnt_parent) |
1690 | goto out1; |
1691 | |
1692 | if (S_ISDIR(path->dentry->d_inode->i_mode) != |
1693 | S_ISDIR(old_path.dentry->d_inode->i_mode)) |
1694 | goto out1; |
1695 | /* |
1696 | * Don't move a mount residing in a shared parent. |
1697 | */ |
1698 | if (old_path.mnt->mnt_parent && |
1699 | IS_MNT_SHARED(old_path.mnt->mnt_parent)) |
1700 | goto out1; |
1701 | /* |
1702 | * Don't move a mount tree containing unbindable mounts to a destination |
1703 | * mount which is shared. |
1704 | */ |
1705 | if (IS_MNT_SHARED(path->mnt) && |
1706 | tree_contains_unbindable(old_path.mnt)) |
1707 | goto out1; |
1708 | err = -ELOOP; |
1709 | for (p = path->mnt; p->mnt_parent != p; p = p->mnt_parent) |
1710 | if (p == old_path.mnt) |
1711 | goto out1; |
1712 | |
1713 | err = attach_recursive_mnt(old_path.mnt, path, &parent_path); |
1714 | if (err) |
1715 | goto out1; |
1716 | |
1717 | /* if the mount is moved, it should no longer be expire |
1718 | * automatically */ |
1719 | list_del_init(&old_path.mnt->mnt_expire); |
1720 | out1: |
1721 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
1722 | out: |
1723 | up_write(&namespace_sem); |
1724 | if (!err) |
1725 | path_put(&parent_path); |
1726 | path_put(&old_path); |
1727 | return err; |
1728 | } |
1729 | |
1730 | /* |
1731 | * create a new mount for userspace and request it to be added into the |
1732 | * namespace's tree |
1733 | */ |
1734 | static int do_new_mount(struct path *path, char *type, int flags, |
1735 | int mnt_flags, char *name, void *data) |
1736 | { |
1737 | struct vfsmount *mnt; |
1738 | |
1739 | if (!type) |
1740 | return -EINVAL; |
1741 | |
1742 | /* we need capabilities... */ |
1743 | if (!capable(CAP_SYS_ADMIN)) |
1744 | return -EPERM; |
1745 | |
1746 | mnt = do_kern_mount(type, flags, name, data); |
1747 | if (IS_ERR(mnt)) |
1748 | return PTR_ERR(mnt); |
1749 | |
1750 | return do_add_mount(mnt, path, mnt_flags, NULL); |
1751 | } |
1752 | |
1753 | /* |
1754 | * add a mount into a namespace's mount tree |
1755 | * - provide the option of adding the new mount to an expiration list |
1756 | */ |
1757 | int do_add_mount(struct vfsmount *newmnt, struct path *path, |
1758 | int mnt_flags, struct list_head *fslist) |
1759 | { |
1760 | int err; |
1761 | |
1762 | mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL); |
1763 | |
1764 | down_write(&namespace_sem); |
1765 | /* Something was mounted here while we slept */ |
1766 | while (d_mountpoint(path->dentry) && |
1767 | follow_down(path)) |
1768 | ; |
1769 | err = -EINVAL; |
1770 | if (!(mnt_flags & MNT_SHRINKABLE) && !check_mnt(path->mnt)) |
1771 | goto unlock; |
1772 | |
1773 | /* Refuse the same filesystem on the same mount point */ |
1774 | err = -EBUSY; |
1775 | if (path->mnt->mnt_sb == newmnt->mnt_sb && |
1776 | path->mnt->mnt_root == path->dentry) |
1777 | goto unlock; |
1778 | |
1779 | err = -EINVAL; |
1780 | if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode)) |
1781 | goto unlock; |
1782 | |
1783 | newmnt->mnt_flags = mnt_flags; |
1784 | if ((err = graft_tree(newmnt, path))) |
1785 | goto unlock; |
1786 | |
1787 | if (fslist) /* add to the specified expiration list */ |
1788 | list_add_tail(&newmnt->mnt_expire, fslist); |
1789 | |
1790 | up_write(&namespace_sem); |
1791 | return 0; |
1792 | |
1793 | unlock: |
1794 | up_write(&namespace_sem); |
1795 | mntput(newmnt); |
1796 | return err; |
1797 | } |
1798 | |
1799 | EXPORT_SYMBOL_GPL(do_add_mount); |
1800 | |
1801 | /* |
1802 | * process a list of expirable mountpoints with the intent of discarding any |
1803 | * mountpoints that aren't in use and haven't been touched since last we came |
1804 | * here |
1805 | */ |
1806 | void mark_mounts_for_expiry(struct list_head *mounts) |
1807 | { |
1808 | struct vfsmount *mnt, *next; |
1809 | LIST_HEAD(graveyard); |
1810 | LIST_HEAD(umounts); |
1811 | |
1812 | if (list_empty(mounts)) |
1813 | return; |
1814 | |
1815 | down_write(&namespace_sem); |
1816 | br_write_lock(vfsmount_lock); |
1817 | |
1818 | /* extract from the expiration list every vfsmount that matches the |
1819 | * following criteria: |
1820 | * - only referenced by its parent vfsmount |
1821 | * - still marked for expiry (marked on the last call here; marks are |
1822 | * cleared by mntput()) |
1823 | */ |
1824 | list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { |
1825 | if (!xchg(&mnt->mnt_expiry_mark, 1) || |
1826 | propagate_mount_busy(mnt, 1)) |
1827 | continue; |
1828 | list_move(&mnt->mnt_expire, &graveyard); |
1829 | } |
1830 | while (!list_empty(&graveyard)) { |
1831 | mnt = list_first_entry(&graveyard, struct vfsmount, mnt_expire); |
1832 | touch_mnt_namespace(mnt->mnt_ns); |
1833 | umount_tree(mnt, 1, &umounts); |
1834 | } |
1835 | br_write_unlock(vfsmount_lock); |
1836 | up_write(&namespace_sem); |
1837 | |
1838 | release_mounts(&umounts); |
1839 | } |
1840 | |
1841 | EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); |
1842 | |
1843 | /* |
1844 | * Ripoff of 'select_parent()' |
1845 | * |
1846 | * search the list of submounts for a given mountpoint, and move any |
1847 | * shrinkable submounts to the 'graveyard' list. |
1848 | */ |
1849 | static int select_submounts(struct vfsmount *parent, struct list_head *graveyard) |
1850 | { |
1851 | struct vfsmount *this_parent = parent; |
1852 | struct list_head *next; |
1853 | int found = 0; |
1854 | |
1855 | repeat: |
1856 | next = this_parent->mnt_mounts.next; |
1857 | resume: |
1858 | while (next != &this_parent->mnt_mounts) { |
1859 | struct list_head *tmp = next; |
1860 | struct vfsmount *mnt = list_entry(tmp, struct vfsmount, mnt_child); |
1861 | |
1862 | next = tmp->next; |
1863 | if (!(mnt->mnt_flags & MNT_SHRINKABLE)) |
1864 | continue; |
1865 | /* |
1866 | * Descend a level if the d_mounts list is non-empty. |
1867 | */ |
1868 | if (!list_empty(&mnt->mnt_mounts)) { |
1869 | this_parent = mnt; |
1870 | goto repeat; |
1871 | } |
1872 | |
1873 | if (!propagate_mount_busy(mnt, 1)) { |
1874 | list_move_tail(&mnt->mnt_expire, graveyard); |
1875 | found++; |
1876 | } |
1877 | } |
1878 | /* |
1879 | * All done at this level ... ascend and resume the search |
1880 | */ |
1881 | if (this_parent != parent) { |
1882 | next = this_parent->mnt_child.next; |
1883 | this_parent = this_parent->mnt_parent; |
1884 | goto resume; |
1885 | } |
1886 | return found; |
1887 | } |
1888 | |
1889 | /* |
1890 | * process a list of expirable mountpoints with the intent of discarding any |
1891 | * submounts of a specific parent mountpoint |
1892 | * |
1893 | * vfsmount_lock must be held for write |
1894 | */ |
1895 | static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts) |
1896 | { |
1897 | LIST_HEAD(graveyard); |
1898 | struct vfsmount *m; |
1899 | |
1900 | /* extract submounts of 'mountpoint' from the expiration list */ |
1901 | while (select_submounts(mnt, &graveyard)) { |
1902 | while (!list_empty(&graveyard)) { |
1903 | m = list_first_entry(&graveyard, struct vfsmount, |
1904 | mnt_expire); |
1905 | touch_mnt_namespace(m->mnt_ns); |
1906 | umount_tree(m, 1, umounts); |
1907 | } |
1908 | } |
1909 | } |
1910 | |
1911 | /* |
1912 | * Some copy_from_user() implementations do not return the exact number of |
1913 | * bytes remaining to copy on a fault. But copy_mount_options() requires that. |
1914 | * Note that this function differs from copy_from_user() in that it will oops |
1915 | * on bad values of `to', rather than returning a short copy. |
1916 | */ |
1917 | static long exact_copy_from_user(void *to, const void __user * from, |
1918 | unsigned long n) |
1919 | { |
1920 | char *t = to; |
1921 | const char __user *f = from; |
1922 | char c; |
1923 | |
1924 | if (!access_ok(VERIFY_READ, from, n)) |
1925 | return n; |
1926 | |
1927 | while (n) { |
1928 | if (__get_user(c, f)) { |
1929 | memset(t, 0, n); |
1930 | break; |
1931 | } |
1932 | *t++ = c; |
1933 | f++; |
1934 | n--; |
1935 | } |
1936 | return n; |
1937 | } |
1938 | |
1939 | int copy_mount_options(const void __user * data, unsigned long *where) |
1940 | { |
1941 | int i; |
1942 | unsigned long page; |
1943 | unsigned long size; |
1944 | |
1945 | *where = 0; |
1946 | if (!data) |
1947 | return 0; |
1948 | |
1949 | if (!(page = __get_free_page(GFP_KERNEL))) |
1950 | return -ENOMEM; |
1951 | |
1952 | /* We only care that *some* data at the address the user |
1953 | * gave us is valid. Just in case, we'll zero |
1954 | * the remainder of the page. |
1955 | */ |
1956 | /* copy_from_user cannot cross TASK_SIZE ! */ |
1957 | size = TASK_SIZE - (unsigned long)data; |
1958 | if (size > PAGE_SIZE) |
1959 | size = PAGE_SIZE; |
1960 | |
1961 | i = size - exact_copy_from_user((void *)page, data, size); |
1962 | if (!i) { |
1963 | free_page(page); |
1964 | return -EFAULT; |
1965 | } |
1966 | if (i != PAGE_SIZE) |
1967 | memset((char *)page + i, 0, PAGE_SIZE - i); |
1968 | *where = page; |
1969 | return 0; |
1970 | } |
1971 | |
1972 | int copy_mount_string(const void __user *data, char **where) |
1973 | { |
1974 | char *tmp; |
1975 | |
1976 | if (!data) { |
1977 | *where = NULL; |
1978 | return 0; |
1979 | } |
1980 | |
1981 | tmp = strndup_user(data, PAGE_SIZE); |
1982 | if (IS_ERR(tmp)) |
1983 | return PTR_ERR(tmp); |
1984 | |
1985 | *where = tmp; |
1986 | return 0; |
1987 | } |
1988 | |
1989 | /* |
1990 | * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to |
1991 | * be given to the mount() call (ie: read-only, no-dev, no-suid etc). |
1992 | * |
1993 | * data is a (void *) that can point to any structure up to |
1994 | * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent |
1995 | * information (or be NULL). |
1996 | * |
1997 | * Pre-0.97 versions of mount() didn't have a flags word. |
1998 | * When the flags word was introduced its top half was required |
1999 | * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. |
2000 | * Therefore, if this magic number is present, it carries no information |
2001 | * and must be discarded. |
2002 | */ |
2003 | long do_mount(char *dev_name, char *dir_name, char *type_page, |
2004 | unsigned long flags, void *data_page) |
2005 | { |
2006 | struct path path; |
2007 | int retval = 0; |
2008 | int mnt_flags = 0; |
2009 | |
2010 | /* Discard magic */ |
2011 | if ((flags & MS_MGC_MSK) == MS_MGC_VAL) |
2012 | flags &= ~MS_MGC_MSK; |
2013 | |
2014 | /* Basic sanity checks */ |
2015 | |
2016 | if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) |
2017 | return -EINVAL; |
2018 | |
2019 | if (data_page) |
2020 | ((char *)data_page)[PAGE_SIZE - 1] = 0; |
2021 | |
2022 | /* ... and get the mountpoint */ |
2023 | retval = kern_path(dir_name, LOOKUP_FOLLOW, &path); |
2024 | if (retval) |
2025 | return retval; |
2026 | |
2027 | retval = security_sb_mount(dev_name, &path, |
2028 | type_page, flags, data_page); |
2029 | if (retval) |
2030 | goto dput_out; |
2031 | |
2032 | /* Default to relatime unless overriden */ |
2033 | if (!(flags & MS_NOATIME)) |
2034 | mnt_flags |= MNT_RELATIME; |
2035 | |
2036 | /* Separate the per-mountpoint flags */ |
2037 | if (flags & MS_NOSUID) |
2038 | mnt_flags |= MNT_NOSUID; |
2039 | if (flags & MS_NODEV) |
2040 | mnt_flags |= MNT_NODEV; |
2041 | if (flags & MS_NOEXEC) |
2042 | mnt_flags |= MNT_NOEXEC; |
2043 | if (flags & MS_NOATIME) |
2044 | mnt_flags |= MNT_NOATIME; |
2045 | if (flags & MS_NODIRATIME) |
2046 | mnt_flags |= MNT_NODIRATIME; |
2047 | if (flags & MS_STRICTATIME) |
2048 | mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); |
2049 | if (flags & MS_RDONLY) |
2050 | mnt_flags |= MNT_READONLY; |
2051 | |
2052 | flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN | |
2053 | MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT | |
2054 | MS_STRICTATIME); |
2055 | |
2056 | if (flags & MS_REMOUNT) |
2057 | retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags, |
2058 | data_page); |
2059 | else if (flags & MS_BIND) |
2060 | retval = do_loopback(&path, dev_name, flags & MS_REC); |
2061 | else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
2062 | retval = do_change_type(&path, flags); |
2063 | else if (flags & MS_MOVE) |
2064 | retval = do_move_mount(&path, dev_name); |
2065 | else |
2066 | retval = do_new_mount(&path, type_page, flags, mnt_flags, |
2067 | dev_name, data_page); |
2068 | dput_out: |
2069 | path_put(&path); |
2070 | return retval; |
2071 | } |
2072 | |
2073 | static struct mnt_namespace *alloc_mnt_ns(void) |
2074 | { |
2075 | struct mnt_namespace *new_ns; |
2076 | |
2077 | new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); |
2078 | if (!new_ns) |
2079 | return ERR_PTR(-ENOMEM); |
2080 | atomic_set(&new_ns->count, 1); |
2081 | new_ns->root = NULL; |
2082 | INIT_LIST_HEAD(&new_ns->list); |
2083 | init_waitqueue_head(&new_ns->poll); |
2084 | new_ns->event = 0; |
2085 | return new_ns; |
2086 | } |
2087 | |
2088 | /* |
2089 | * Allocate a new namespace structure and populate it with contents |
2090 | * copied from the namespace of the passed in task structure. |
2091 | */ |
2092 | static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns, |
2093 | struct fs_struct *fs) |
2094 | { |
2095 | struct mnt_namespace *new_ns; |
2096 | struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; |
2097 | struct vfsmount *p, *q; |
2098 | |
2099 | new_ns = alloc_mnt_ns(); |
2100 | if (IS_ERR(new_ns)) |
2101 | return new_ns; |
2102 | |
2103 | down_write(&namespace_sem); |
2104 | /* First pass: copy the tree topology */ |
2105 | new_ns->root = copy_tree(mnt_ns->root, mnt_ns->root->mnt_root, |
2106 | CL_COPY_ALL | CL_EXPIRE); |
2107 | if (!new_ns->root) { |
2108 | up_write(&namespace_sem); |
2109 | kfree(new_ns); |
2110 | return ERR_PTR(-ENOMEM); |
2111 | } |
2112 | br_write_lock(vfsmount_lock); |
2113 | list_add_tail(&new_ns->list, &new_ns->root->mnt_list); |
2114 | br_write_unlock(vfsmount_lock); |
2115 | |
2116 | /* |
2117 | * Second pass: switch the tsk->fs->* elements and mark new vfsmounts |
2118 | * as belonging to new namespace. We have already acquired a private |
2119 | * fs_struct, so tsk->fs->lock is not needed. |
2120 | */ |
2121 | p = mnt_ns->root; |
2122 | q = new_ns->root; |
2123 | while (p) { |
2124 | q->mnt_ns = new_ns; |
2125 | if (fs) { |
2126 | if (p == fs->root.mnt) { |
2127 | rootmnt = p; |
2128 | fs->root.mnt = mntget(q); |
2129 | } |
2130 | if (p == fs->pwd.mnt) { |
2131 | pwdmnt = p; |
2132 | fs->pwd.mnt = mntget(q); |
2133 | } |
2134 | } |
2135 | p = next_mnt(p, mnt_ns->root); |
2136 | q = next_mnt(q, new_ns->root); |
2137 | } |
2138 | up_write(&namespace_sem); |
2139 | |
2140 | if (rootmnt) |
2141 | mntput(rootmnt); |
2142 | if (pwdmnt) |
2143 | mntput(pwdmnt); |
2144 | |
2145 | return new_ns; |
2146 | } |
2147 | |
2148 | struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, |
2149 | struct fs_struct *new_fs) |
2150 | { |
2151 | struct mnt_namespace *new_ns; |
2152 | |
2153 | BUG_ON(!ns); |
2154 | get_mnt_ns(ns); |
2155 | |
2156 | if (!(flags & CLONE_NEWNS)) |
2157 | return ns; |
2158 | |
2159 | new_ns = dup_mnt_ns(ns, new_fs); |
2160 | |
2161 | put_mnt_ns(ns); |
2162 | return new_ns; |
2163 | } |
2164 | |
2165 | /** |
2166 | * create_mnt_ns - creates a private namespace and adds a root filesystem |
2167 | * @mnt: pointer to the new root filesystem mountpoint |
2168 | */ |
2169 | struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt) |
2170 | { |
2171 | struct mnt_namespace *new_ns; |
2172 | |
2173 | new_ns = alloc_mnt_ns(); |
2174 | if (!IS_ERR(new_ns)) { |
2175 | mnt->mnt_ns = new_ns; |
2176 | new_ns->root = mnt; |
2177 | list_add(&new_ns->list, &new_ns->root->mnt_list); |
2178 | } |
2179 | return new_ns; |
2180 | } |
2181 | EXPORT_SYMBOL(create_mnt_ns); |
2182 | |
2183 | SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, |
2184 | char __user *, type, unsigned long, flags, void __user *, data) |
2185 | { |
2186 | int ret; |
2187 | char *kernel_type; |
2188 | char *kernel_dir; |
2189 | char *kernel_dev; |
2190 | unsigned long data_page; |
2191 | |
2192 | ret = copy_mount_string(type, &kernel_type); |
2193 | if (ret < 0) |
2194 | goto out_type; |
2195 | |
2196 | kernel_dir = getname(dir_name); |
2197 | if (IS_ERR(kernel_dir)) { |
2198 | ret = PTR_ERR(kernel_dir); |
2199 | goto out_dir; |
2200 | } |
2201 | |
2202 | ret = copy_mount_string(dev_name, &kernel_dev); |
2203 | if (ret < 0) |
2204 | goto out_dev; |
2205 | |
2206 | ret = copy_mount_options(data, &data_page); |
2207 | if (ret < 0) |
2208 | goto out_data; |
2209 | |
2210 | ret = do_mount(kernel_dev, kernel_dir, kernel_type, flags, |
2211 | (void *) data_page); |
2212 | |
2213 | free_page(data_page); |
2214 | out_data: |
2215 | kfree(kernel_dev); |
2216 | out_dev: |
2217 | putname(kernel_dir); |
2218 | out_dir: |
2219 | kfree(kernel_type); |
2220 | out_type: |
2221 | return ret; |
2222 | } |
2223 | |
2224 | /* |
2225 | * pivot_root Semantics: |
2226 | * Moves the root file system of the current process to the directory put_old, |
2227 | * makes new_root as the new root file system of the current process, and sets |
2228 | * root/cwd of all processes which had them on the current root to new_root. |
2229 | * |
2230 | * Restrictions: |
2231 | * The new_root and put_old must be directories, and must not be on the |
2232 | * same file system as the current process root. The put_old must be |
2233 | * underneath new_root, i.e. adding a non-zero number of /.. to the string |
2234 | * pointed to by put_old must yield the same directory as new_root. No other |
2235 | * file system may be mounted on put_old. After all, new_root is a mountpoint. |
2236 | * |
2237 | * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. |
2238 | * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives |
2239 | * in this situation. |
2240 | * |
2241 | * Notes: |
2242 | * - we don't move root/cwd if they are not at the root (reason: if something |
2243 | * cared enough to change them, it's probably wrong to force them elsewhere) |
2244 | * - it's okay to pick a root that isn't the root of a file system, e.g. |
2245 | * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, |
2246 | * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root |
2247 | * first. |
2248 | */ |
2249 | SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, |
2250 | const char __user *, put_old) |
2251 | { |
2252 | struct vfsmount *tmp; |
2253 | struct path new, old, parent_path, root_parent, root; |
2254 | int error; |
2255 | |
2256 | if (!capable(CAP_SYS_ADMIN)) |
2257 | return -EPERM; |
2258 | |
2259 | error = user_path_dir(new_root, &new); |
2260 | if (error) |
2261 | goto out0; |
2262 | error = -EINVAL; |
2263 | if (!check_mnt(new.mnt)) |
2264 | goto out1; |
2265 | |
2266 | error = user_path_dir(put_old, &old); |
2267 | if (error) |
2268 | goto out1; |
2269 | |
2270 | error = security_sb_pivotroot(&old, &new); |
2271 | if (error) { |
2272 | path_put(&old); |
2273 | goto out1; |
2274 | } |
2275 | |
2276 | get_fs_root(current->fs, &root); |
2277 | down_write(&namespace_sem); |
2278 | mutex_lock(&old.dentry->d_inode->i_mutex); |
2279 | error = -EINVAL; |
2280 | if (IS_MNT_SHARED(old.mnt) || |
2281 | IS_MNT_SHARED(new.mnt->mnt_parent) || |
2282 | IS_MNT_SHARED(root.mnt->mnt_parent)) |
2283 | goto out2; |
2284 | if (!check_mnt(root.mnt)) |
2285 | goto out2; |
2286 | error = -ENOENT; |
2287 | if (cant_mount(old.dentry)) |
2288 | goto out2; |
2289 | if (d_unlinked(new.dentry)) |
2290 | goto out2; |
2291 | if (d_unlinked(old.dentry)) |
2292 | goto out2; |
2293 | error = -EBUSY; |
2294 | if (new.mnt == root.mnt || |
2295 | old.mnt == root.mnt) |
2296 | goto out2; /* loop, on the same file system */ |
2297 | error = -EINVAL; |
2298 | if (root.mnt->mnt_root != root.dentry) |
2299 | goto out2; /* not a mountpoint */ |
2300 | if (root.mnt->mnt_parent == root.mnt) |
2301 | goto out2; /* not attached */ |
2302 | if (new.mnt->mnt_root != new.dentry) |
2303 | goto out2; /* not a mountpoint */ |
2304 | if (new.mnt->mnt_parent == new.mnt) |
2305 | goto out2; /* not attached */ |
2306 | /* make sure we can reach put_old from new_root */ |
2307 | tmp = old.mnt; |
2308 | br_write_lock(vfsmount_lock); |
2309 | if (tmp != new.mnt) { |
2310 | for (;;) { |
2311 | if (tmp->mnt_parent == tmp) |
2312 | goto out3; /* already mounted on put_old */ |
2313 | if (tmp->mnt_parent == new.mnt) |
2314 | break; |
2315 | tmp = tmp->mnt_parent; |
2316 | } |
2317 | if (!is_subdir(tmp->mnt_mountpoint, new.dentry)) |
2318 | goto out3; |
2319 | } else if (!is_subdir(old.dentry, new.dentry)) |
2320 | goto out3; |
2321 | detach_mnt(new.mnt, &parent_path); |
2322 | detach_mnt(root.mnt, &root_parent); |
2323 | /* mount old root on put_old */ |
2324 | attach_mnt(root.mnt, &old); |
2325 | /* mount new_root on / */ |
2326 | attach_mnt(new.mnt, &root_parent); |
2327 | touch_mnt_namespace(current->nsproxy->mnt_ns); |
2328 | br_write_unlock(vfsmount_lock); |
2329 | chroot_fs_refs(&root, &new); |
2330 | error = 0; |
2331 | path_put(&root_parent); |
2332 | path_put(&parent_path); |
2333 | out2: |
2334 | mutex_unlock(&old.dentry->d_inode->i_mutex); |
2335 | up_write(&namespace_sem); |
2336 | path_put(&root); |
2337 | path_put(&old); |
2338 | out1: |
2339 | path_put(&new); |
2340 | out0: |
2341 | return error; |
2342 | out3: |
2343 | br_write_unlock(vfsmount_lock); |
2344 | goto out2; |
2345 | } |
2346 | |
2347 | static void __init init_mount_tree(void) |
2348 | { |
2349 | struct vfsmount *mnt; |
2350 | struct mnt_namespace *ns; |
2351 | struct path root; |
2352 | |
2353 | mnt = do_kern_mount("rootfs", 0, "rootfs", NULL); |
2354 | if (IS_ERR(mnt)) |
2355 | panic("Can't create rootfs"); |
2356 | ns = create_mnt_ns(mnt); |
2357 | if (IS_ERR(ns)) |
2358 | panic("Can't allocate initial namespace"); |
2359 | |
2360 | init_task.nsproxy->mnt_ns = ns; |
2361 | get_mnt_ns(ns); |
2362 | |
2363 | root.mnt = ns->root; |
2364 | root.dentry = ns->root->mnt_root; |
2365 | |
2366 | set_fs_pwd(current->fs, &root); |
2367 | set_fs_root(current->fs, &root); |
2368 | } |
2369 | |
2370 | void __init mnt_init(void) |
2371 | { |
2372 | unsigned u; |
2373 | int err; |
2374 | |
2375 | init_rwsem(&namespace_sem); |
2376 | |
2377 | mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount), |
2378 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); |
2379 | |
2380 | mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); |
2381 | |
2382 | if (!mount_hashtable) |
2383 | panic("Failed to allocate mount hash table\n"); |
2384 | |
2385 | printk("Mount-cache hash table entries: %lu\n", HASH_SIZE); |
2386 | |
2387 | for (u = 0; u < HASH_SIZE; u++) |
2388 | INIT_LIST_HEAD(&mount_hashtable[u]); |
2389 | |
2390 | br_lock_init(vfsmount_lock); |
2391 | |
2392 | err = sysfs_init(); |
2393 | if (err) |
2394 | printk(KERN_WARNING "%s: sysfs_init error: %d\n", |
2395 | __func__, err); |
2396 | fs_kobj = kobject_create_and_add("fs", NULL); |
2397 | if (!fs_kobj) |
2398 | printk(KERN_WARNING "%s: kobj create error\n", __func__); |
2399 | init_rootfs(); |
2400 | init_mount_tree(); |
2401 | } |
2402 | |
2403 | void put_mnt_ns(struct mnt_namespace *ns) |
2404 | { |
2405 | LIST_HEAD(umount_list); |
2406 | |
2407 | if (!atomic_dec_and_test(&ns->count)) |
2408 | return; |
2409 | down_write(&namespace_sem); |
2410 | br_write_lock(vfsmount_lock); |
2411 | umount_tree(ns->root, 0, &umount_list); |
2412 | br_write_unlock(vfsmount_lock); |
2413 | up_write(&namespace_sem); |
2414 | release_mounts(&umount_list); |
2415 | kfree(ns); |
2416 | } |
2417 | EXPORT_SYMBOL(put_mnt_ns); |
2418 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
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jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9