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