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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/smp_lock.h> |
15 | #include <linux/init.h> |
16 | #include <linux/kernel.h> |
17 | #include <linux/acct.h> |
18 | #include <linux/capability.h> |
19 | #include <linux/cpumask.h> |
20 | #include <linux/module.h> |
21 | #include <linux/sysfs.h> |
22 | #include <linux/seq_file.h> |
23 | #include <linux/mnt_namespace.h> |
24 | #include <linux/namei.h> |
25 | #include <linux/nsproxy.h> |
26 | #include <linux/security.h> |
27 | #include <linux/mount.h> |
28 | #include <linux/ramfs.h> |
29 | #include <linux/log2.h> |
30 | #include <linux/idr.h> |
31 | #include <linux/fs_struct.h> |
32 | #include <asm/uaccess.h> |
33 | #include <asm/unistd.h> |
34 | #include "pnode.h" |
35 | #include "internal.h" |
36 | |
37 | #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head)) |
38 | #define HASH_SIZE (1UL << HASH_SHIFT) |
39 | |
40 | /* spinlock for vfsmount related operations, inplace of dcache_lock */ |
41 | __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock); |
42 | |
43 | static int event; |
44 | static DEFINE_IDA(mnt_id_ida); |
45 | static DEFINE_IDA(mnt_group_ida); |
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 | static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) |
58 | { |
59 | unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); |
60 | tmp += ((unsigned long)dentry / L1_CACHE_BYTES); |
61 | tmp = tmp + (tmp >> HASH_SHIFT); |
62 | return tmp & (HASH_SIZE - 1); |
63 | } |
64 | |
65 | #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16) |
66 | |
67 | /* allocation is serialized by namespace_sem */ |
68 | static int mnt_alloc_id(struct vfsmount *mnt) |
69 | { |
70 | int res; |
71 | |
72 | retry: |
73 | ida_pre_get(&mnt_id_ida, GFP_KERNEL); |
74 | spin_lock(&vfsmount_lock); |
75 | res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id); |
76 | if (!res) |
77 | mnt_id_start = mnt->mnt_id + 1; |
78 | spin_unlock(&vfsmount_lock); |
79 | if (res == -EAGAIN) |
80 | goto retry; |
81 | |
82 | return res; |
83 | } |
84 | |
85 | static void mnt_free_id(struct vfsmount *mnt) |
86 | { |
87 | int id = mnt->mnt_id; |
88 | spin_lock(&vfsmount_lock); |
89 | ida_remove(&mnt_id_ida, id); |
90 | if (mnt_id_start > id) |
91 | mnt_id_start = id; |
92 | spin_unlock(&vfsmount_lock); |
93 | } |
94 | |
95 | /* |
96 | * Allocate a new peer group ID |
97 | * |
98 | * mnt_group_ida is protected by namespace_sem |
99 | */ |
100 | static int mnt_alloc_group_id(struct vfsmount *mnt) |
101 | { |
102 | int res; |
103 | |
104 | if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL)) |
105 | return -ENOMEM; |
106 | |
107 | res = ida_get_new_above(&mnt_group_ida, |
108 | mnt_group_start, |
109 | &mnt->mnt_group_id); |
110 | if (!res) |
111 | mnt_group_start = mnt->mnt_group_id + 1; |
112 | |
113 | return res; |
114 | } |
115 | |
116 | /* |
117 | * Release a peer group ID |
118 | */ |
119 | void mnt_release_group_id(struct vfsmount *mnt) |
120 | { |
121 | int id = mnt->mnt_group_id; |
122 | ida_remove(&mnt_group_ida, id); |
123 | if (mnt_group_start > id) |
124 | mnt_group_start = id; |
125 | mnt->mnt_group_id = 0; |
126 | } |
127 | |
128 | struct vfsmount *alloc_vfsmnt(const char *name) |
129 | { |
130 | struct vfsmount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); |
131 | if (mnt) { |
132 | int err; |
133 | |
134 | err = mnt_alloc_id(mnt); |
135 | if (err) |
136 | goto out_free_cache; |
137 | |
138 | if (name) { |
139 | mnt->mnt_devname = kstrdup(name, GFP_KERNEL); |
140 | if (!mnt->mnt_devname) |
141 | goto out_free_id; |
142 | } |
143 | |
144 | atomic_set(&mnt->mnt_count, 1); |
145 | INIT_LIST_HEAD(&mnt->mnt_hash); |
146 | INIT_LIST_HEAD(&mnt->mnt_child); |
147 | INIT_LIST_HEAD(&mnt->mnt_mounts); |
148 | INIT_LIST_HEAD(&mnt->mnt_list); |
149 | INIT_LIST_HEAD(&mnt->mnt_expire); |
150 | INIT_LIST_HEAD(&mnt->mnt_share); |
151 | INIT_LIST_HEAD(&mnt->mnt_slave_list); |
152 | INIT_LIST_HEAD(&mnt->mnt_slave); |
153 | #ifdef CONFIG_SMP |
154 | mnt->mnt_writers = alloc_percpu(int); |
155 | if (!mnt->mnt_writers) |
156 | goto out_free_devname; |
157 | #else |
158 | mnt->mnt_writers = 0; |
159 | #endif |
160 | } |
161 | return mnt; |
162 | |
163 | #ifdef CONFIG_SMP |
164 | out_free_devname: |
165 | kfree(mnt->mnt_devname); |
166 | #endif |
167 | out_free_id: |
168 | mnt_free_id(mnt); |
169 | out_free_cache: |
170 | kmem_cache_free(mnt_cache, mnt); |
171 | return NULL; |
172 | } |
173 | |
174 | /* |
175 | * Most r/o checks on a fs are for operations that take |
176 | * discrete amounts of time, like a write() or unlink(). |
177 | * We must keep track of when those operations start |
178 | * (for permission checks) and when they end, so that |
179 | * we can determine when writes are able to occur to |
180 | * a filesystem. |
181 | */ |
182 | /* |
183 | * __mnt_is_readonly: check whether a mount is read-only |
184 | * @mnt: the mount to check for its write status |
185 | * |
186 | * This shouldn't be used directly ouside of the VFS. |
187 | * It does not guarantee that the filesystem will stay |
188 | * r/w, just that it is right *now*. This can not and |
189 | * should not be used in place of IS_RDONLY(inode). |
190 | * mnt_want/drop_write() will _keep_ the filesystem |
191 | * r/w. |
192 | */ |
193 | int __mnt_is_readonly(struct vfsmount *mnt) |
194 | { |
195 | if (mnt->mnt_flags & MNT_READONLY) |
196 | return 1; |
197 | if (mnt->mnt_sb->s_flags & MS_RDONLY) |
198 | return 1; |
199 | return 0; |
200 | } |
201 | EXPORT_SYMBOL_GPL(__mnt_is_readonly); |
202 | |
203 | static inline void inc_mnt_writers(struct vfsmount *mnt) |
204 | { |
205 | #ifdef CONFIG_SMP |
206 | (*per_cpu_ptr(mnt->mnt_writers, smp_processor_id()))++; |
207 | #else |
208 | mnt->mnt_writers++; |
209 | #endif |
210 | } |
211 | |
212 | static inline void dec_mnt_writers(struct vfsmount *mnt) |
213 | { |
214 | #ifdef CONFIG_SMP |
215 | (*per_cpu_ptr(mnt->mnt_writers, smp_processor_id()))--; |
216 | #else |
217 | mnt->mnt_writers--; |
218 | #endif |
219 | } |
220 | |
221 | static unsigned int count_mnt_writers(struct vfsmount *mnt) |
222 | { |
223 | #ifdef CONFIG_SMP |
224 | unsigned int count = 0; |
225 | int cpu; |
226 | |
227 | for_each_possible_cpu(cpu) { |
228 | count += *per_cpu_ptr(mnt->mnt_writers, cpu); |
229 | } |
230 | |
231 | return count; |
232 | #else |
233 | return mnt->mnt_writers; |
234 | #endif |
235 | } |
236 | |
237 | /* |
238 | * Most r/o checks on a fs are for operations that take |
239 | * discrete amounts of time, like a write() or unlink(). |
240 | * We must keep track of when those operations start |
241 | * (for permission checks) and when they end, so that |
242 | * we can determine when writes are able to occur to |
243 | * a filesystem. |
244 | */ |
245 | /** |
246 | * mnt_want_write - get write access to a mount |
247 | * @mnt: the mount on which to take a write |
248 | * |
249 | * This tells the low-level filesystem that a write is |
250 | * about to be performed to it, and makes sure that |
251 | * writes are allowed before returning success. When |
252 | * the write operation is finished, mnt_drop_write() |
253 | * must be called. This is effectively a refcount. |
254 | */ |
255 | int mnt_want_write(struct vfsmount *mnt) |
256 | { |
257 | int ret = 0; |
258 | |
259 | preempt_disable(); |
260 | inc_mnt_writers(mnt); |
261 | /* |
262 | * The store to inc_mnt_writers must be visible before we pass |
263 | * MNT_WRITE_HOLD loop below, so that the slowpath can see our |
264 | * incremented count after it has set MNT_WRITE_HOLD. |
265 | */ |
266 | smp_mb(); |
267 | while (mnt->mnt_flags & MNT_WRITE_HOLD) |
268 | cpu_relax(); |
269 | /* |
270 | * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will |
271 | * be set to match its requirements. So we must not load that until |
272 | * MNT_WRITE_HOLD is cleared. |
273 | */ |
274 | smp_rmb(); |
275 | if (__mnt_is_readonly(mnt)) { |
276 | dec_mnt_writers(mnt); |
277 | ret = -EROFS; |
278 | goto out; |
279 | } |
280 | out: |
281 | preempt_enable(); |
282 | return ret; |
283 | } |
284 | EXPORT_SYMBOL_GPL(mnt_want_write); |
285 | |
286 | /** |
287 | * mnt_clone_write - get write access to a mount |
288 | * @mnt: the mount on which to take a write |
289 | * |
290 | * This is effectively like mnt_want_write, except |
291 | * it must only be used to take an extra write reference |
292 | * on a mountpoint that we already know has a write reference |
293 | * on it. This allows some optimisation. |
294 | * |
295 | * After finished, mnt_drop_write must be called as usual to |
296 | * drop the reference. |
297 | */ |
298 | int mnt_clone_write(struct vfsmount *mnt) |
299 | { |
300 | /* superblock may be r/o */ |
301 | if (__mnt_is_readonly(mnt)) |
302 | return -EROFS; |
303 | preempt_disable(); |
304 | inc_mnt_writers(mnt); |
305 | preempt_enable(); |
306 | return 0; |
307 | } |
308 | EXPORT_SYMBOL_GPL(mnt_clone_write); |
309 | |
310 | /** |
311 | * mnt_want_write_file - get write access to a file's mount |
312 | * @file: the file who's mount on which to take a write |
313 | * |
314 | * This is like mnt_want_write, but it takes a file and can |
315 | * do some optimisations if the file is open for write already |
316 | */ |
317 | int mnt_want_write_file(struct file *file) |
318 | { |
319 | struct inode *inode = file->f_dentry->d_inode; |
320 | if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode)) |
321 | return mnt_want_write(file->f_path.mnt); |
322 | else |
323 | return mnt_clone_write(file->f_path.mnt); |
324 | } |
325 | EXPORT_SYMBOL_GPL(mnt_want_write_file); |
326 | |
327 | /** |
328 | * mnt_drop_write - give up write access to a mount |
329 | * @mnt: the mount on which to give up write access |
330 | * |
331 | * Tells the low-level filesystem that we are done |
332 | * performing writes to it. Must be matched with |
333 | * mnt_want_write() call above. |
334 | */ |
335 | void mnt_drop_write(struct vfsmount *mnt) |
336 | { |
337 | preempt_disable(); |
338 | dec_mnt_writers(mnt); |
339 | preempt_enable(); |
340 | } |
341 | EXPORT_SYMBOL_GPL(mnt_drop_write); |
342 | |
343 | static int mnt_make_readonly(struct vfsmount *mnt) |
344 | { |
345 | int ret = 0; |
346 | |
347 | spin_lock(&vfsmount_lock); |
348 | mnt->mnt_flags |= MNT_WRITE_HOLD; |
349 | /* |
350 | * After storing MNT_WRITE_HOLD, we'll read the counters. This store |
351 | * should be visible before we do. |
352 | */ |
353 | smp_mb(); |
354 | |
355 | /* |
356 | * With writers on hold, if this value is zero, then there are |
357 | * definitely no active writers (although held writers may subsequently |
358 | * increment the count, they'll have to wait, and decrement it after |
359 | * seeing MNT_READONLY). |
360 | * |
361 | * It is OK to have counter incremented on one CPU and decremented on |
362 | * another: the sum will add up correctly. The danger would be when we |
363 | * sum up each counter, if we read a counter before it is incremented, |
364 | * but then read another CPU's count which it has been subsequently |
365 | * decremented from -- we would see more decrements than we should. |
366 | * MNT_WRITE_HOLD protects against this scenario, because |
367 | * mnt_want_write first increments count, then smp_mb, then spins on |
368 | * MNT_WRITE_HOLD, so it can't be decremented by another CPU while |
369 | * we're counting up here. |
370 | */ |
371 | if (count_mnt_writers(mnt) > 0) |
372 | ret = -EBUSY; |
373 | else |
374 | mnt->mnt_flags |= MNT_READONLY; |
375 | /* |
376 | * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers |
377 | * that become unheld will see MNT_READONLY. |
378 | */ |
379 | smp_wmb(); |
380 | mnt->mnt_flags &= ~MNT_WRITE_HOLD; |
381 | spin_unlock(&vfsmount_lock); |
382 | return ret; |
383 | } |
384 | |
385 | static void __mnt_unmake_readonly(struct vfsmount *mnt) |
386 | { |
387 | spin_lock(&vfsmount_lock); |
388 | mnt->mnt_flags &= ~MNT_READONLY; |
389 | spin_unlock(&vfsmount_lock); |
390 | } |
391 | |
392 | void simple_set_mnt(struct vfsmount *mnt, struct super_block *sb) |
393 | { |
394 | mnt->mnt_sb = sb; |
395 | mnt->mnt_root = dget(sb->s_root); |
396 | } |
397 | |
398 | EXPORT_SYMBOL(simple_set_mnt); |
399 | |
400 | void free_vfsmnt(struct vfsmount *mnt) |
401 | { |
402 | kfree(mnt->mnt_devname); |
403 | mnt_free_id(mnt); |
404 | #ifdef CONFIG_SMP |
405 | free_percpu(mnt->mnt_writers); |
406 | #endif |
407 | kmem_cache_free(mnt_cache, mnt); |
408 | } |
409 | |
410 | /* |
411 | * find the first or last mount at @dentry on vfsmount @mnt depending on |
412 | * @dir. If @dir is set return the first mount else return the last mount. |
413 | */ |
414 | struct vfsmount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry, |
415 | int dir) |
416 | { |
417 | struct list_head *head = mount_hashtable + hash(mnt, dentry); |
418 | struct list_head *tmp = head; |
419 | struct vfsmount *p, *found = NULL; |
420 | |
421 | for (;;) { |
422 | tmp = dir ? tmp->next : tmp->prev; |
423 | p = NULL; |
424 | if (tmp == head) |
425 | break; |
426 | p = list_entry(tmp, struct vfsmount, mnt_hash); |
427 | if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) { |
428 | found = p; |
429 | break; |
430 | } |
431 | } |
432 | return found; |
433 | } |
434 | |
435 | /* |
436 | * lookup_mnt increments the ref count before returning |
437 | * the vfsmount struct. |
438 | */ |
439 | struct vfsmount *lookup_mnt(struct path *path) |
440 | { |
441 | struct vfsmount *child_mnt; |
442 | spin_lock(&vfsmount_lock); |
443 | if ((child_mnt = __lookup_mnt(path->mnt, path->dentry, 1))) |
444 | mntget(child_mnt); |
445 | spin_unlock(&vfsmount_lock); |
446 | return child_mnt; |
447 | } |
448 | |
449 | static inline int check_mnt(struct vfsmount *mnt) |
450 | { |
451 | return mnt->mnt_ns == current->nsproxy->mnt_ns; |
452 | } |
453 | |
454 | static void touch_mnt_namespace(struct mnt_namespace *ns) |
455 | { |
456 | if (ns) { |
457 | ns->event = ++event; |
458 | wake_up_interruptible(&ns->poll); |
459 | } |
460 | } |
461 | |
462 | static void __touch_mnt_namespace(struct mnt_namespace *ns) |
463 | { |
464 | if (ns && ns->event != event) { |
465 | ns->event = event; |
466 | wake_up_interruptible(&ns->poll); |
467 | } |
468 | } |
469 | |
470 | static void detach_mnt(struct vfsmount *mnt, struct path *old_path) |
471 | { |
472 | old_path->dentry = mnt->mnt_mountpoint; |
473 | old_path->mnt = mnt->mnt_parent; |
474 | mnt->mnt_parent = mnt; |
475 | mnt->mnt_mountpoint = mnt->mnt_root; |
476 | list_del_init(&mnt->mnt_child); |
477 | list_del_init(&mnt->mnt_hash); |
478 | old_path->dentry->d_mounted--; |
479 | } |
480 | |
481 | void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry, |
482 | struct vfsmount *child_mnt) |
483 | { |
484 | child_mnt->mnt_parent = mntget(mnt); |
485 | child_mnt->mnt_mountpoint = dget(dentry); |
486 | dentry->d_mounted++; |
487 | } |
488 | |
489 | static void attach_mnt(struct vfsmount *mnt, struct path *path) |
490 | { |
491 | mnt_set_mountpoint(path->mnt, path->dentry, mnt); |
492 | list_add_tail(&mnt->mnt_hash, mount_hashtable + |
493 | hash(path->mnt, path->dentry)); |
494 | list_add_tail(&mnt->mnt_child, &path->mnt->mnt_mounts); |
495 | } |
496 | |
497 | /* |
498 | * the caller must hold vfsmount_lock |
499 | */ |
500 | static void commit_tree(struct vfsmount *mnt) |
501 | { |
502 | struct vfsmount *parent = mnt->mnt_parent; |
503 | struct vfsmount *m; |
504 | LIST_HEAD(head); |
505 | struct mnt_namespace *n = parent->mnt_ns; |
506 | |
507 | BUG_ON(parent == mnt); |
508 | |
509 | list_add_tail(&head, &mnt->mnt_list); |
510 | list_for_each_entry(m, &head, mnt_list) |
511 | m->mnt_ns = n; |
512 | list_splice(&head, n->list.prev); |
513 | |
514 | list_add_tail(&mnt->mnt_hash, mount_hashtable + |
515 | hash(parent, mnt->mnt_mountpoint)); |
516 | list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); |
517 | touch_mnt_namespace(n); |
518 | } |
519 | |
520 | static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *root) |
521 | { |
522 | struct list_head *next = p->mnt_mounts.next; |
523 | if (next == &p->mnt_mounts) { |
524 | while (1) { |
525 | if (p == root) |
526 | return NULL; |
527 | next = p->mnt_child.next; |
528 | if (next != &p->mnt_parent->mnt_mounts) |
529 | break; |
530 | p = p->mnt_parent; |
531 | } |
532 | } |
533 | return list_entry(next, struct vfsmount, mnt_child); |
534 | } |
535 | |
536 | static struct vfsmount *skip_mnt_tree(struct vfsmount *p) |
537 | { |
538 | struct list_head *prev = p->mnt_mounts.prev; |
539 | while (prev != &p->mnt_mounts) { |
540 | p = list_entry(prev, struct vfsmount, mnt_child); |
541 | prev = p->mnt_mounts.prev; |
542 | } |
543 | return p; |
544 | } |
545 | |
546 | static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root, |
547 | int flag) |
548 | { |
549 | struct super_block *sb = old->mnt_sb; |
550 | struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname); |
551 | |
552 | if (mnt) { |
553 | if (flag & (CL_SLAVE | CL_PRIVATE)) |
554 | mnt->mnt_group_id = 0; /* not a peer of original */ |
555 | else |
556 | mnt->mnt_group_id = old->mnt_group_id; |
557 | |
558 | if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { |
559 | int err = mnt_alloc_group_id(mnt); |
560 | if (err) |
561 | goto out_free; |
562 | } |
563 | |
564 | mnt->mnt_flags = old->mnt_flags; |
565 | atomic_inc(&sb->s_active); |
566 | mnt->mnt_sb = sb; |
567 | mnt->mnt_root = dget(root); |
568 | mnt->mnt_mountpoint = mnt->mnt_root; |
569 | mnt->mnt_parent = mnt; |
570 | |
571 | if (flag & CL_SLAVE) { |
572 | list_add(&mnt->mnt_slave, &old->mnt_slave_list); |
573 | mnt->mnt_master = old; |
574 | CLEAR_MNT_SHARED(mnt); |
575 | } else if (!(flag & CL_PRIVATE)) { |
576 | if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old)) |
577 | list_add(&mnt->mnt_share, &old->mnt_share); |
578 | if (IS_MNT_SLAVE(old)) |
579 | list_add(&mnt->mnt_slave, &old->mnt_slave); |
580 | mnt->mnt_master = old->mnt_master; |
581 | } |
582 | if (flag & CL_MAKE_SHARED) |
583 | set_mnt_shared(mnt); |
584 | |
585 | /* stick the duplicate mount on the same expiry list |
586 | * as the original if that was on one */ |
587 | if (flag & CL_EXPIRE) { |
588 | if (!list_empty(&old->mnt_expire)) |
589 | list_add(&mnt->mnt_expire, &old->mnt_expire); |
590 | } |
591 | } |
592 | return mnt; |
593 | |
594 | out_free: |
595 | free_vfsmnt(mnt); |
596 | return NULL; |
597 | } |
598 | |
599 | static inline void __mntput(struct vfsmount *mnt) |
600 | { |
601 | struct super_block *sb = mnt->mnt_sb; |
602 | /* |
603 | * This probably indicates that somebody messed |
604 | * up a mnt_want/drop_write() pair. If this |
605 | * happens, the filesystem was probably unable |
606 | * to make r/w->r/o transitions. |
607 | */ |
608 | /* |
609 | * atomic_dec_and_lock() used to deal with ->mnt_count decrements |
610 | * provides barriers, so count_mnt_writers() below is safe. AV |
611 | */ |
612 | WARN_ON(count_mnt_writers(mnt)); |
613 | dput(mnt->mnt_root); |
614 | free_vfsmnt(mnt); |
615 | deactivate_super(sb); |
616 | } |
617 | |
618 | void mntput_no_expire(struct vfsmount *mnt) |
619 | { |
620 | repeat: |
621 | if (atomic_dec_and_lock(&mnt->mnt_count, &vfsmount_lock)) { |
622 | if (likely(!mnt->mnt_pinned)) { |
623 | spin_unlock(&vfsmount_lock); |
624 | __mntput(mnt); |
625 | return; |
626 | } |
627 | atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count); |
628 | mnt->mnt_pinned = 0; |
629 | spin_unlock(&vfsmount_lock); |
630 | acct_auto_close_mnt(mnt); |
631 | security_sb_umount_close(mnt); |
632 | goto repeat; |
633 | } |
634 | } |
635 | |
636 | EXPORT_SYMBOL(mntput_no_expire); |
637 | |
638 | void mnt_pin(struct vfsmount *mnt) |
639 | { |
640 | spin_lock(&vfsmount_lock); |
641 | mnt->mnt_pinned++; |
642 | spin_unlock(&vfsmount_lock); |
643 | } |
644 | |
645 | EXPORT_SYMBOL(mnt_pin); |
646 | |
647 | void mnt_unpin(struct vfsmount *mnt) |
648 | { |
649 | spin_lock(&vfsmount_lock); |
650 | if (mnt->mnt_pinned) { |
651 | atomic_inc(&mnt->mnt_count); |
652 | mnt->mnt_pinned--; |
653 | } |
654 | spin_unlock(&vfsmount_lock); |
655 | } |
656 | |
657 | EXPORT_SYMBOL(mnt_unpin); |
658 | |
659 | static inline void mangle(struct seq_file *m, const char *s) |
660 | { |
661 | seq_escape(m, s, " \t\n\\"); |
662 | } |
663 | |
664 | /* |
665 | * Simple .show_options callback for filesystems which don't want to |
666 | * implement more complex mount option showing. |
667 | * |
668 | * See also save_mount_options(). |
669 | */ |
670 | int generic_show_options(struct seq_file *m, struct vfsmount *mnt) |
671 | { |
672 | const char *options; |
673 | |
674 | rcu_read_lock(); |
675 | options = rcu_dereference(mnt->mnt_sb->s_options); |
676 | |
677 | if (options != NULL && options[0]) { |
678 | seq_putc(m, ','); |
679 | mangle(m, options); |
680 | } |
681 | rcu_read_unlock(); |
682 | |
683 | return 0; |
684 | } |
685 | EXPORT_SYMBOL(generic_show_options); |
686 | |
687 | /* |
688 | * If filesystem uses generic_show_options(), this function should be |
689 | * called from the fill_super() callback. |
690 | * |
691 | * The .remount_fs callback usually needs to be handled in a special |
692 | * way, to make sure, that previous options are not overwritten if the |
693 | * remount fails. |
694 | * |
695 | * Also note, that if the filesystem's .remount_fs function doesn't |
696 | * reset all options to their default value, but changes only newly |
697 | * given options, then the displayed options will not reflect reality |
698 | * any more. |
699 | */ |
700 | void save_mount_options(struct super_block *sb, char *options) |
701 | { |
702 | BUG_ON(sb->s_options); |
703 | rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL)); |
704 | } |
705 | EXPORT_SYMBOL(save_mount_options); |
706 | |
707 | void replace_mount_options(struct super_block *sb, char *options) |
708 | { |
709 | char *old = sb->s_options; |
710 | rcu_assign_pointer(sb->s_options, options); |
711 | if (old) { |
712 | synchronize_rcu(); |
713 | kfree(old); |
714 | } |
715 | } |
716 | EXPORT_SYMBOL(replace_mount_options); |
717 | |
718 | #ifdef CONFIG_PROC_FS |
719 | /* iterator */ |
720 | static void *m_start(struct seq_file *m, loff_t *pos) |
721 | { |
722 | struct proc_mounts *p = m->private; |
723 | |
724 | down_read(&namespace_sem); |
725 | return seq_list_start(&p->ns->list, *pos); |
726 | } |
727 | |
728 | static void *m_next(struct seq_file *m, void *v, loff_t *pos) |
729 | { |
730 | struct proc_mounts *p = m->private; |
731 | |
732 | return seq_list_next(v, &p->ns->list, pos); |
733 | } |
734 | |
735 | static void m_stop(struct seq_file *m, void *v) |
736 | { |
737 | up_read(&namespace_sem); |
738 | } |
739 | |
740 | int mnt_had_events(struct proc_mounts *p) |
741 | { |
742 | struct mnt_namespace *ns = p->ns; |
743 | int res = 0; |
744 | |
745 | spin_lock(&vfsmount_lock); |
746 | if (p->event != ns->event) { |
747 | p->event = ns->event; |
748 | res = 1; |
749 | } |
750 | spin_unlock(&vfsmount_lock); |
751 | |
752 | return res; |
753 | } |
754 | |
755 | struct proc_fs_info { |
756 | int flag; |
757 | const char *str; |
758 | }; |
759 | |
760 | static int show_sb_opts(struct seq_file *m, struct super_block *sb) |
761 | { |
762 | static const struct proc_fs_info fs_info[] = { |
763 | { MS_SYNCHRONOUS, ",sync" }, |
764 | { MS_DIRSYNC, ",dirsync" }, |
765 | { MS_MANDLOCK, ",mand" }, |
766 | { 0, NULL } |
767 | }; |
768 | const struct proc_fs_info *fs_infop; |
769 | |
770 | for (fs_infop = fs_info; fs_infop->flag; fs_infop++) { |
771 | if (sb->s_flags & fs_infop->flag) |
772 | seq_puts(m, fs_infop->str); |
773 | } |
774 | |
775 | return security_sb_show_options(m, sb); |
776 | } |
777 | |
778 | static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt) |
779 | { |
780 | static const struct proc_fs_info mnt_info[] = { |
781 | { MNT_NOSUID, ",nosuid" }, |
782 | { MNT_NODEV, ",nodev" }, |
783 | { MNT_NOEXEC, ",noexec" }, |
784 | { MNT_NOATIME, ",noatime" }, |
785 | { MNT_NODIRATIME, ",nodiratime" }, |
786 | { MNT_RELATIME, ",relatime" }, |
787 | { MNT_STRICTATIME, ",strictatime" }, |
788 | { 0, NULL } |
789 | }; |
790 | const struct proc_fs_info *fs_infop; |
791 | |
792 | for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) { |
793 | if (mnt->mnt_flags & fs_infop->flag) |
794 | seq_puts(m, fs_infop->str); |
795 | } |
796 | } |
797 | |
798 | static void show_type(struct seq_file *m, struct super_block *sb) |
799 | { |
800 | mangle(m, sb->s_type->name); |
801 | if (sb->s_subtype && sb->s_subtype[0]) { |
802 | seq_putc(m, '.'); |
803 | mangle(m, sb->s_subtype); |
804 | } |
805 | } |
806 | |
807 | static int show_vfsmnt(struct seq_file *m, void *v) |
808 | { |
809 | struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); |
810 | int err = 0; |
811 | struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt }; |
812 | |
813 | mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none"); |
814 | seq_putc(m, ' '); |
815 | seq_path(m, &mnt_path, " \t\n\\"); |
816 | seq_putc(m, ' '); |
817 | show_type(m, mnt->mnt_sb); |
818 | seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw"); |
819 | err = show_sb_opts(m, mnt->mnt_sb); |
820 | if (err) |
821 | goto out; |
822 | show_mnt_opts(m, mnt); |
823 | if (mnt->mnt_sb->s_op->show_options) |
824 | err = mnt->mnt_sb->s_op->show_options(m, mnt); |
825 | seq_puts(m, " 0 0\n"); |
826 | out: |
827 | return err; |
828 | } |
829 | |
830 | const struct seq_operations mounts_op = { |
831 | .start = m_start, |
832 | .next = m_next, |
833 | .stop = m_stop, |
834 | .show = show_vfsmnt |
835 | }; |
836 | |
837 | static int show_mountinfo(struct seq_file *m, void *v) |
838 | { |
839 | struct proc_mounts *p = m->private; |
840 | struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); |
841 | struct super_block *sb = mnt->mnt_sb; |
842 | struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt }; |
843 | struct path root = p->root; |
844 | int err = 0; |
845 | |
846 | seq_printf(m, "%i %i %u:%u ", mnt->mnt_id, mnt->mnt_parent->mnt_id, |
847 | MAJOR(sb->s_dev), MINOR(sb->s_dev)); |
848 | seq_dentry(m, mnt->mnt_root, " \t\n\\"); |
849 | seq_putc(m, ' '); |
850 | seq_path_root(m, &mnt_path, &root, " \t\n\\"); |
851 | if (root.mnt != p->root.mnt || root.dentry != p->root.dentry) { |
852 | /* |
853 | * Mountpoint is outside root, discard that one. Ugly, |
854 | * but less so than trying to do that in iterator in a |
855 | * race-free way (due to renames). |
856 | */ |
857 | return SEQ_SKIP; |
858 | } |
859 | seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw"); |
860 | show_mnt_opts(m, mnt); |
861 | |
862 | /* Tagged fields ("foo:X" or "bar") */ |
863 | if (IS_MNT_SHARED(mnt)) |
864 | seq_printf(m, " shared:%i", mnt->mnt_group_id); |
865 | if (IS_MNT_SLAVE(mnt)) { |
866 | int master = mnt->mnt_master->mnt_group_id; |
867 | int dom = get_dominating_id(mnt, &p->root); |
868 | seq_printf(m, " master:%i", master); |
869 | if (dom && dom != master) |
870 | seq_printf(m, " propagate_from:%i", dom); |
871 | } |
872 | if (IS_MNT_UNBINDABLE(mnt)) |
873 | seq_puts(m, " unbindable"); |
874 | |
875 | /* Filesystem specific data */ |
876 | seq_puts(m, " - "); |
877 | show_type(m, sb); |
878 | seq_putc(m, ' '); |
879 | mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none"); |
880 | seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw"); |
881 | err = show_sb_opts(m, sb); |
882 | if (err) |
883 | goto out; |
884 | if (sb->s_op->show_options) |
885 | err = sb->s_op->show_options(m, mnt); |
886 | seq_putc(m, '\n'); |
887 | out: |
888 | return err; |
889 | } |
890 | |
891 | const struct seq_operations mountinfo_op = { |
892 | .start = m_start, |
893 | .next = m_next, |
894 | .stop = m_stop, |
895 | .show = show_mountinfo, |
896 | }; |
897 | |
898 | static int show_vfsstat(struct seq_file *m, void *v) |
899 | { |
900 | struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); |
901 | struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt }; |
902 | int err = 0; |
903 | |
904 | /* device */ |
905 | if (mnt->mnt_devname) { |
906 | seq_puts(m, "device "); |
907 | mangle(m, mnt->mnt_devname); |
908 | } else |
909 | seq_puts(m, "no device"); |
910 | |
911 | /* mount point */ |
912 | seq_puts(m, " mounted on "); |
913 | seq_path(m, &mnt_path, " \t\n\\"); |
914 | seq_putc(m, ' '); |
915 | |
916 | /* file system type */ |
917 | seq_puts(m, "with fstype "); |
918 | show_type(m, mnt->mnt_sb); |
919 | |
920 | /* optional statistics */ |
921 | if (mnt->mnt_sb->s_op->show_stats) { |
922 | seq_putc(m, ' '); |
923 | err = mnt->mnt_sb->s_op->show_stats(m, mnt); |
924 | } |
925 | |
926 | seq_putc(m, '\n'); |
927 | return err; |
928 | } |
929 | |
930 | const struct seq_operations mountstats_op = { |
931 | .start = m_start, |
932 | .next = m_next, |
933 | .stop = m_stop, |
934 | .show = show_vfsstat, |
935 | }; |
936 | #endif /* CONFIG_PROC_FS */ |
937 | |
938 | /** |
939 | * may_umount_tree - check if a mount tree is busy |
940 | * @mnt: root of mount tree |
941 | * |
942 | * This is called to check if a tree of mounts has any |
943 | * open files, pwds, chroots or sub mounts that are |
944 | * busy. |
945 | */ |
946 | int may_umount_tree(struct vfsmount *mnt) |
947 | { |
948 | int actual_refs = 0; |
949 | int minimum_refs = 0; |
950 | struct vfsmount *p; |
951 | |
952 | spin_lock(&vfsmount_lock); |
953 | for (p = mnt; p; p = next_mnt(p, mnt)) { |
954 | actual_refs += atomic_read(&p->mnt_count); |
955 | minimum_refs += 2; |
956 | } |
957 | spin_unlock(&vfsmount_lock); |
958 | |
959 | if (actual_refs > minimum_refs) |
960 | return 0; |
961 | |
962 | return 1; |
963 | } |
964 | |
965 | EXPORT_SYMBOL(may_umount_tree); |
966 | |
967 | /** |
968 | * may_umount - check if a mount point is busy |
969 | * @mnt: root of mount |
970 | * |
971 | * This is called to check if a mount point has any |
972 | * open files, pwds, chroots or sub mounts. If the |
973 | * mount has sub mounts this will return busy |
974 | * regardless of whether the sub mounts are busy. |
975 | * |
976 | * Doesn't take quota and stuff into account. IOW, in some cases it will |
977 | * give false negatives. The main reason why it's here is that we need |
978 | * a non-destructive way to look for easily umountable filesystems. |
979 | */ |
980 | int may_umount(struct vfsmount *mnt) |
981 | { |
982 | int ret = 1; |
983 | down_read(&namespace_sem); |
984 | spin_lock(&vfsmount_lock); |
985 | if (propagate_mount_busy(mnt, 2)) |
986 | ret = 0; |
987 | spin_unlock(&vfsmount_lock); |
988 | up_read(&namespace_sem); |
989 | return ret; |
990 | } |
991 | |
992 | EXPORT_SYMBOL(may_umount); |
993 | |
994 | void release_mounts(struct list_head *head) |
995 | { |
996 | struct vfsmount *mnt; |
997 | while (!list_empty(head)) { |
998 | mnt = list_first_entry(head, struct vfsmount, mnt_hash); |
999 | list_del_init(&mnt->mnt_hash); |
1000 | if (mnt->mnt_parent != mnt) { |
1001 | struct dentry *dentry; |
1002 | struct vfsmount *m; |
1003 | spin_lock(&vfsmount_lock); |
1004 | dentry = mnt->mnt_mountpoint; |
1005 | m = mnt->mnt_parent; |
1006 | mnt->mnt_mountpoint = mnt->mnt_root; |
1007 | mnt->mnt_parent = mnt; |
1008 | m->mnt_ghosts--; |
1009 | spin_unlock(&vfsmount_lock); |
1010 | dput(dentry); |
1011 | mntput(m); |
1012 | } |
1013 | mntput(mnt); |
1014 | } |
1015 | } |
1016 | |
1017 | void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill) |
1018 | { |
1019 | struct vfsmount *p; |
1020 | |
1021 | for (p = mnt; p; p = next_mnt(p, mnt)) |
1022 | list_move(&p->mnt_hash, kill); |
1023 | |
1024 | if (propagate) |
1025 | propagate_umount(kill); |
1026 | |
1027 | list_for_each_entry(p, kill, mnt_hash) { |
1028 | list_del_init(&p->mnt_expire); |
1029 | list_del_init(&p->mnt_list); |
1030 | __touch_mnt_namespace(p->mnt_ns); |
1031 | p->mnt_ns = NULL; |
1032 | list_del_init(&p->mnt_child); |
1033 | if (p->mnt_parent != p) { |
1034 | p->mnt_parent->mnt_ghosts++; |
1035 | p->mnt_mountpoint->d_mounted--; |
1036 | } |
1037 | change_mnt_propagation(p, MS_PRIVATE); |
1038 | } |
1039 | } |
1040 | |
1041 | static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts); |
1042 | |
1043 | static int do_umount(struct vfsmount *mnt, int flags) |
1044 | { |
1045 | struct super_block *sb = mnt->mnt_sb; |
1046 | int retval; |
1047 | LIST_HEAD(umount_list); |
1048 | |
1049 | retval = security_sb_umount(mnt, flags); |
1050 | if (retval) |
1051 | return retval; |
1052 | |
1053 | /* |
1054 | * Allow userspace to request a mountpoint be expired rather than |
1055 | * unmounting unconditionally. Unmount only happens if: |
1056 | * (1) the mark is already set (the mark is cleared by mntput()) |
1057 | * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] |
1058 | */ |
1059 | if (flags & MNT_EXPIRE) { |
1060 | if (mnt == current->fs->root.mnt || |
1061 | flags & (MNT_FORCE | MNT_DETACH)) |
1062 | return -EINVAL; |
1063 | |
1064 | if (atomic_read(&mnt->mnt_count) != 2) |
1065 | return -EBUSY; |
1066 | |
1067 | if (!xchg(&mnt->mnt_expiry_mark, 1)) |
1068 | return -EAGAIN; |
1069 | } |
1070 | |
1071 | /* |
1072 | * If we may have to abort operations to get out of this |
1073 | * mount, and they will themselves hold resources we must |
1074 | * allow the fs to do things. In the Unix tradition of |
1075 | * 'Gee thats tricky lets do it in userspace' the umount_begin |
1076 | * might fail to complete on the first run through as other tasks |
1077 | * must return, and the like. Thats for the mount program to worry |
1078 | * about for the moment. |
1079 | */ |
1080 | |
1081 | if (flags & MNT_FORCE && sb->s_op->umount_begin) { |
1082 | sb->s_op->umount_begin(sb); |
1083 | } |
1084 | |
1085 | /* |
1086 | * No sense to grab the lock for this test, but test itself looks |
1087 | * somewhat bogus. Suggestions for better replacement? |
1088 | * Ho-hum... In principle, we might treat that as umount + switch |
1089 | * to rootfs. GC would eventually take care of the old vfsmount. |
1090 | * Actually it makes sense, especially if rootfs would contain a |
1091 | * /reboot - static binary that would close all descriptors and |
1092 | * call reboot(9). Then init(8) could umount root and exec /reboot. |
1093 | */ |
1094 | if (mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { |
1095 | /* |
1096 | * Special case for "unmounting" root ... |
1097 | * we just try to remount it readonly. |
1098 | */ |
1099 | down_write(&sb->s_umount); |
1100 | if (!(sb->s_flags & MS_RDONLY)) |
1101 | retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); |
1102 | up_write(&sb->s_umount); |
1103 | return retval; |
1104 | } |
1105 | |
1106 | down_write(&namespace_sem); |
1107 | spin_lock(&vfsmount_lock); |
1108 | event++; |
1109 | |
1110 | if (!(flags & MNT_DETACH)) |
1111 | shrink_submounts(mnt, &umount_list); |
1112 | |
1113 | retval = -EBUSY; |
1114 | if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) { |
1115 | if (!list_empty(&mnt->mnt_list)) |
1116 | umount_tree(mnt, 1, &umount_list); |
1117 | retval = 0; |
1118 | } |
1119 | spin_unlock(&vfsmount_lock); |
1120 | if (retval) |
1121 | security_sb_umount_busy(mnt); |
1122 | up_write(&namespace_sem); |
1123 | release_mounts(&umount_list); |
1124 | return retval; |
1125 | } |
1126 | |
1127 | /* |
1128 | * Now umount can handle mount points as well as block devices. |
1129 | * This is important for filesystems which use unnamed block devices. |
1130 | * |
1131 | * We now support a flag for forced unmount like the other 'big iron' |
1132 | * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD |
1133 | */ |
1134 | |
1135 | SYSCALL_DEFINE2(umount, char __user *, name, int, flags) |
1136 | { |
1137 | struct path path; |
1138 | int retval; |
1139 | int lookup_flags = 0; |
1140 | |
1141 | if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) |
1142 | return -EINVAL; |
1143 | |
1144 | if (!(flags & UMOUNT_NOFOLLOW)) |
1145 | lookup_flags |= LOOKUP_FOLLOW; |
1146 | |
1147 | retval = user_path_at(AT_FDCWD, name, lookup_flags, &path); |
1148 | if (retval) |
1149 | goto out; |
1150 | retval = -EINVAL; |
1151 | if (path.dentry != path.mnt->mnt_root) |
1152 | goto dput_and_out; |
1153 | if (!check_mnt(path.mnt)) |
1154 | goto dput_and_out; |
1155 | |
1156 | retval = -EPERM; |
1157 | if (!capable(CAP_SYS_ADMIN)) |
1158 | goto dput_and_out; |
1159 | |
1160 | retval = do_umount(path.mnt, flags); |
1161 | dput_and_out: |
1162 | /* we mustn't call path_put() as that would clear mnt_expiry_mark */ |
1163 | dput(path.dentry); |
1164 | mntput_no_expire(path.mnt); |
1165 | out: |
1166 | return retval; |
1167 | } |
1168 | |
1169 | #ifdef __ARCH_WANT_SYS_OLDUMOUNT |
1170 | |
1171 | /* |
1172 | * The 2.0 compatible umount. No flags. |
1173 | */ |
1174 | SYSCALL_DEFINE1(oldumount, char __user *, name) |
1175 | { |
1176 | return sys_umount(name, 0); |
1177 | } |
1178 | |
1179 | #endif |
1180 | |
1181 | static int mount_is_safe(struct path *path) |
1182 | { |
1183 | if (capable(CAP_SYS_ADMIN)) |
1184 | return 0; |
1185 | return -EPERM; |
1186 | #ifdef notyet |
1187 | if (S_ISLNK(path->dentry->d_inode->i_mode)) |
1188 | return -EPERM; |
1189 | if (path->dentry->d_inode->i_mode & S_ISVTX) { |
1190 | if (current_uid() != path->dentry->d_inode->i_uid) |
1191 | return -EPERM; |
1192 | } |
1193 | if (inode_permission(path->dentry->d_inode, MAY_WRITE)) |
1194 | return -EPERM; |
1195 | return 0; |
1196 | #endif |
1197 | } |
1198 | |
1199 | struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, |
1200 | int flag) |
1201 | { |
1202 | struct vfsmount *res, *p, *q, *r, *s; |
1203 | struct path path; |
1204 | |
1205 | if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt)) |
1206 | return NULL; |
1207 | |
1208 | res = q = clone_mnt(mnt, dentry, flag); |
1209 | if (!q) |
1210 | goto Enomem; |
1211 | q->mnt_mountpoint = mnt->mnt_mountpoint; |
1212 | |
1213 | p = mnt; |
1214 | list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { |
1215 | if (!is_subdir(r->mnt_mountpoint, dentry)) |
1216 | continue; |
1217 | |
1218 | for (s = r; s; s = next_mnt(s, r)) { |
1219 | if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) { |
1220 | s = skip_mnt_tree(s); |
1221 | continue; |
1222 | } |
1223 | while (p != s->mnt_parent) { |
1224 | p = p->mnt_parent; |
1225 | q = q->mnt_parent; |
1226 | } |
1227 | p = s; |
1228 | path.mnt = q; |
1229 | path.dentry = p->mnt_mountpoint; |
1230 | q = clone_mnt(p, p->mnt_root, flag); |
1231 | if (!q) |
1232 | goto Enomem; |
1233 | spin_lock(&vfsmount_lock); |
1234 | list_add_tail(&q->mnt_list, &res->mnt_list); |
1235 | attach_mnt(q, &path); |
1236 | spin_unlock(&vfsmount_lock); |
1237 | } |
1238 | } |
1239 | return res; |
1240 | Enomem: |
1241 | if (res) { |
1242 | LIST_HEAD(umount_list); |
1243 | spin_lock(&vfsmount_lock); |
1244 | umount_tree(res, 0, &umount_list); |
1245 | spin_unlock(&vfsmount_lock); |
1246 | release_mounts(&umount_list); |
1247 | } |
1248 | return NULL; |
1249 | } |
1250 | |
1251 | struct vfsmount *collect_mounts(struct path *path) |
1252 | { |
1253 | struct vfsmount *tree; |
1254 | down_write(&namespace_sem); |
1255 | tree = copy_tree(path->mnt, path->dentry, CL_COPY_ALL | CL_PRIVATE); |
1256 | up_write(&namespace_sem); |
1257 | return tree; |
1258 | } |
1259 | |
1260 | void drop_collected_mounts(struct vfsmount *mnt) |
1261 | { |
1262 | LIST_HEAD(umount_list); |
1263 | down_write(&namespace_sem); |
1264 | spin_lock(&vfsmount_lock); |
1265 | umount_tree(mnt, 0, &umount_list); |
1266 | spin_unlock(&vfsmount_lock); |
1267 | up_write(&namespace_sem); |
1268 | release_mounts(&umount_list); |
1269 | } |
1270 | |
1271 | int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, |
1272 | struct vfsmount *root) |
1273 | { |
1274 | struct vfsmount *mnt; |
1275 | int res = f(root, arg); |
1276 | if (res) |
1277 | return res; |
1278 | list_for_each_entry(mnt, &root->mnt_list, mnt_list) { |
1279 | res = f(mnt, arg); |
1280 | if (res) |
1281 | return res; |
1282 | } |
1283 | return 0; |
1284 | } |
1285 | |
1286 | static void cleanup_group_ids(struct vfsmount *mnt, struct vfsmount *end) |
1287 | { |
1288 | struct vfsmount *p; |
1289 | |
1290 | for (p = mnt; p != end; p = next_mnt(p, mnt)) { |
1291 | if (p->mnt_group_id && !IS_MNT_SHARED(p)) |
1292 | mnt_release_group_id(p); |
1293 | } |
1294 | } |
1295 | |
1296 | static int invent_group_ids(struct vfsmount *mnt, bool recurse) |
1297 | { |
1298 | struct vfsmount *p; |
1299 | |
1300 | for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { |
1301 | if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { |
1302 | int err = mnt_alloc_group_id(p); |
1303 | if (err) { |
1304 | cleanup_group_ids(mnt, p); |
1305 | return err; |
1306 | } |
1307 | } |
1308 | } |
1309 | |
1310 | return 0; |
1311 | } |
1312 | |
1313 | /* |
1314 | * @source_mnt : mount tree to be attached |
1315 | * @nd : place the mount tree @source_mnt is attached |
1316 | * @parent_nd : if non-null, detach the source_mnt from its parent and |
1317 | * store the parent mount and mountpoint dentry. |
1318 | * (done when source_mnt is moved) |
1319 | * |
1320 | * NOTE: in the table below explains the semantics when a source mount |
1321 | * of a given type is attached to a destination mount of a given type. |
1322 | * --------------------------------------------------------------------------- |
1323 | * | BIND MOUNT OPERATION | |
1324 | * |************************************************************************** |
1325 | * | source-->| shared | private | slave | unbindable | |
1326 | * | dest | | | | | |
1327 | * | | | | | | | |
1328 | * | v | | | | | |
1329 | * |************************************************************************** |
1330 | * | shared | shared (++) | shared (+) | shared(+++)| invalid | |
1331 | * | | | | | | |
1332 | * |non-shared| shared (+) | private | slave (*) | invalid | |
1333 | * *************************************************************************** |
1334 | * A bind operation clones the source mount and mounts the clone on the |
1335 | * destination mount. |
1336 | * |
1337 | * (++) the cloned mount is propagated to all the mounts in the propagation |
1338 | * tree of the destination mount and the cloned mount is added to |
1339 | * the peer group of the source mount. |
1340 | * (+) the cloned mount is created under the destination mount and is marked |
1341 | * as shared. The cloned mount is added to the peer group of the source |
1342 | * mount. |
1343 | * (+++) the mount is propagated to all the mounts in the propagation tree |
1344 | * of the destination mount and the cloned mount is made slave |
1345 | * of the same master as that of the source mount. The cloned mount |
1346 | * is marked as 'shared and slave'. |
1347 | * (*) the cloned mount is made a slave of the same master as that of the |
1348 | * source mount. |
1349 | * |
1350 | * --------------------------------------------------------------------------- |
1351 | * | MOVE MOUNT OPERATION | |
1352 | * |************************************************************************** |
1353 | * | source-->| shared | private | slave | unbindable | |
1354 | * | dest | | | | | |
1355 | * | | | | | | | |
1356 | * | v | | | | | |
1357 | * |************************************************************************** |
1358 | * | shared | shared (+) | shared (+) | shared(+++) | invalid | |
1359 | * | | | | | | |
1360 | * |non-shared| shared (+*) | private | slave (*) | unbindable | |
1361 | * *************************************************************************** |
1362 | * |
1363 | * (+) the mount is moved to the destination. And is then propagated to |
1364 | * all the mounts in the propagation tree of the destination mount. |
1365 | * (+*) the mount is moved to the destination. |
1366 | * (+++) the mount is moved to the destination and is then propagated to |
1367 | * all the mounts belonging to the destination mount's propagation tree. |
1368 | * the mount is marked as 'shared and slave'. |
1369 | * (*) the mount continues to be a slave at the new location. |
1370 | * |
1371 | * if the source mount is a tree, the operations explained above is |
1372 | * applied to each mount in the tree. |
1373 | * Must be called without spinlocks held, since this function can sleep |
1374 | * in allocations. |
1375 | */ |
1376 | static int attach_recursive_mnt(struct vfsmount *source_mnt, |
1377 | struct path *path, struct path *parent_path) |
1378 | { |
1379 | LIST_HEAD(tree_list); |
1380 | struct vfsmount *dest_mnt = path->mnt; |
1381 | struct dentry *dest_dentry = path->dentry; |
1382 | struct vfsmount *child, *p; |
1383 | int err; |
1384 | |
1385 | if (IS_MNT_SHARED(dest_mnt)) { |
1386 | err = invent_group_ids(source_mnt, true); |
1387 | if (err) |
1388 | goto out; |
1389 | } |
1390 | err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list); |
1391 | if (err) |
1392 | goto out_cleanup_ids; |
1393 | |
1394 | spin_lock(&vfsmount_lock); |
1395 | |
1396 | if (IS_MNT_SHARED(dest_mnt)) { |
1397 | for (p = source_mnt; p; p = next_mnt(p, source_mnt)) |
1398 | set_mnt_shared(p); |
1399 | } |
1400 | if (parent_path) { |
1401 | detach_mnt(source_mnt, parent_path); |
1402 | attach_mnt(source_mnt, path); |
1403 | touch_mnt_namespace(parent_path->mnt->mnt_ns); |
1404 | } else { |
1405 | mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt); |
1406 | commit_tree(source_mnt); |
1407 | } |
1408 | |
1409 | list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { |
1410 | list_del_init(&child->mnt_hash); |
1411 | commit_tree(child); |
1412 | } |
1413 | spin_unlock(&vfsmount_lock); |
1414 | return 0; |
1415 | |
1416 | out_cleanup_ids: |
1417 | if (IS_MNT_SHARED(dest_mnt)) |
1418 | cleanup_group_ids(source_mnt, NULL); |
1419 | out: |
1420 | return err; |
1421 | } |
1422 | |
1423 | static int graft_tree(struct vfsmount *mnt, struct path *path) |
1424 | { |
1425 | int err; |
1426 | if (mnt->mnt_sb->s_flags & MS_NOUSER) |
1427 | return -EINVAL; |
1428 | |
1429 | if (S_ISDIR(path->dentry->d_inode->i_mode) != |
1430 | S_ISDIR(mnt->mnt_root->d_inode->i_mode)) |
1431 | return -ENOTDIR; |
1432 | |
1433 | err = -ENOENT; |
1434 | mutex_lock(&path->dentry->d_inode->i_mutex); |
1435 | if (IS_DEADDIR(path->dentry->d_inode)) |
1436 | goto out_unlock; |
1437 | |
1438 | err = security_sb_check_sb(mnt, path); |
1439 | if (err) |
1440 | goto out_unlock; |
1441 | |
1442 | err = -ENOENT; |
1443 | if (!d_unlinked(path->dentry)) |
1444 | err = attach_recursive_mnt(mnt, path, NULL); |
1445 | out_unlock: |
1446 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
1447 | if (!err) |
1448 | security_sb_post_addmount(mnt, path); |
1449 | return err; |
1450 | } |
1451 | |
1452 | /* |
1453 | * recursively change the type of the mountpoint. |
1454 | */ |
1455 | static int do_change_type(struct path *path, int flag) |
1456 | { |
1457 | struct vfsmount *m, *mnt = path->mnt; |
1458 | int recurse = flag & MS_REC; |
1459 | int type = flag & ~MS_REC; |
1460 | int err = 0; |
1461 | |
1462 | if (!capable(CAP_SYS_ADMIN)) |
1463 | return -EPERM; |
1464 | |
1465 | if (path->dentry != path->mnt->mnt_root) |
1466 | return -EINVAL; |
1467 | |
1468 | down_write(&namespace_sem); |
1469 | if (type == MS_SHARED) { |
1470 | err = invent_group_ids(mnt, recurse); |
1471 | if (err) |
1472 | goto out_unlock; |
1473 | } |
1474 | |
1475 | spin_lock(&vfsmount_lock); |
1476 | for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) |
1477 | change_mnt_propagation(m, type); |
1478 | spin_unlock(&vfsmount_lock); |
1479 | |
1480 | out_unlock: |
1481 | up_write(&namespace_sem); |
1482 | return err; |
1483 | } |
1484 | |
1485 | /* |
1486 | * do loopback mount. |
1487 | */ |
1488 | static int do_loopback(struct path *path, char *old_name, |
1489 | int recurse) |
1490 | { |
1491 | struct path old_path; |
1492 | struct vfsmount *mnt = NULL; |
1493 | int err = mount_is_safe(path); |
1494 | if (err) |
1495 | return err; |
1496 | if (!old_name || !*old_name) |
1497 | return -EINVAL; |
1498 | err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); |
1499 | if (err) |
1500 | return err; |
1501 | |
1502 | down_write(&namespace_sem); |
1503 | err = -EINVAL; |
1504 | if (IS_MNT_UNBINDABLE(old_path.mnt)) |
1505 | goto out; |
1506 | |
1507 | if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt)) |
1508 | goto out; |
1509 | |
1510 | err = -ENOMEM; |
1511 | if (recurse) |
1512 | mnt = copy_tree(old_path.mnt, old_path.dentry, 0); |
1513 | else |
1514 | mnt = clone_mnt(old_path.mnt, old_path.dentry, 0); |
1515 | |
1516 | if (!mnt) |
1517 | goto out; |
1518 | |
1519 | err = graft_tree(mnt, path); |
1520 | if (err) { |
1521 | LIST_HEAD(umount_list); |
1522 | spin_lock(&vfsmount_lock); |
1523 | umount_tree(mnt, 0, &umount_list); |
1524 | spin_unlock(&vfsmount_lock); |
1525 | release_mounts(&umount_list); |
1526 | } |
1527 | |
1528 | out: |
1529 | up_write(&namespace_sem); |
1530 | path_put(&old_path); |
1531 | return err; |
1532 | } |
1533 | |
1534 | static int change_mount_flags(struct vfsmount *mnt, int ms_flags) |
1535 | { |
1536 | int error = 0; |
1537 | int readonly_request = 0; |
1538 | |
1539 | if (ms_flags & MS_RDONLY) |
1540 | readonly_request = 1; |
1541 | if (readonly_request == __mnt_is_readonly(mnt)) |
1542 | return 0; |
1543 | |
1544 | if (readonly_request) |
1545 | error = mnt_make_readonly(mnt); |
1546 | else |
1547 | __mnt_unmake_readonly(mnt); |
1548 | return error; |
1549 | } |
1550 | |
1551 | /* |
1552 | * change filesystem flags. dir should be a physical root of filesystem. |
1553 | * If you've mounted a non-root directory somewhere and want to do remount |
1554 | * on it - tough luck. |
1555 | */ |
1556 | static int do_remount(struct path *path, int flags, int mnt_flags, |
1557 | void *data) |
1558 | { |
1559 | int err; |
1560 | struct super_block *sb = path->mnt->mnt_sb; |
1561 | |
1562 | if (!capable(CAP_SYS_ADMIN)) |
1563 | return -EPERM; |
1564 | |
1565 | if (!check_mnt(path->mnt)) |
1566 | return -EINVAL; |
1567 | |
1568 | if (path->dentry != path->mnt->mnt_root) |
1569 | return -EINVAL; |
1570 | |
1571 | down_write(&sb->s_umount); |
1572 | if (flags & MS_BIND) |
1573 | err = change_mount_flags(path->mnt, flags); |
1574 | else |
1575 | err = do_remount_sb(sb, flags, data, 0); |
1576 | if (!err) { |
1577 | spin_lock(&vfsmount_lock); |
1578 | mnt_flags |= path->mnt->mnt_flags & MNT_PROPAGATION_MASK; |
1579 | path->mnt->mnt_flags = mnt_flags; |
1580 | spin_unlock(&vfsmount_lock); |
1581 | } |
1582 | up_write(&sb->s_umount); |
1583 | if (!err) { |
1584 | security_sb_post_remount(path->mnt, flags, data); |
1585 | |
1586 | spin_lock(&vfsmount_lock); |
1587 | touch_mnt_namespace(path->mnt->mnt_ns); |
1588 | spin_unlock(&vfsmount_lock); |
1589 | } |
1590 | return err; |
1591 | } |
1592 | |
1593 | static inline int tree_contains_unbindable(struct vfsmount *mnt) |
1594 | { |
1595 | struct vfsmount *p; |
1596 | for (p = mnt; p; p = next_mnt(p, mnt)) { |
1597 | if (IS_MNT_UNBINDABLE(p)) |
1598 | return 1; |
1599 | } |
1600 | return 0; |
1601 | } |
1602 | |
1603 | static int do_move_mount(struct path *path, char *old_name) |
1604 | { |
1605 | struct path old_path, parent_path; |
1606 | struct vfsmount *p; |
1607 | int err = 0; |
1608 | if (!capable(CAP_SYS_ADMIN)) |
1609 | return -EPERM; |
1610 | if (!old_name || !*old_name) |
1611 | return -EINVAL; |
1612 | err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); |
1613 | if (err) |
1614 | return err; |
1615 | |
1616 | down_write(&namespace_sem); |
1617 | while (d_mountpoint(path->dentry) && |
1618 | follow_down(path)) |
1619 | ; |
1620 | err = -EINVAL; |
1621 | if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt)) |
1622 | goto out; |
1623 | |
1624 | err = -ENOENT; |
1625 | mutex_lock(&path->dentry->d_inode->i_mutex); |
1626 | if (IS_DEADDIR(path->dentry->d_inode)) |
1627 | goto out1; |
1628 | |
1629 | if (d_unlinked(path->dentry)) |
1630 | goto out1; |
1631 | |
1632 | err = -EINVAL; |
1633 | if (old_path.dentry != old_path.mnt->mnt_root) |
1634 | goto out1; |
1635 | |
1636 | if (old_path.mnt == old_path.mnt->mnt_parent) |
1637 | goto out1; |
1638 | |
1639 | if (S_ISDIR(path->dentry->d_inode->i_mode) != |
1640 | S_ISDIR(old_path.dentry->d_inode->i_mode)) |
1641 | goto out1; |
1642 | /* |
1643 | * Don't move a mount residing in a shared parent. |
1644 | */ |
1645 | if (old_path.mnt->mnt_parent && |
1646 | IS_MNT_SHARED(old_path.mnt->mnt_parent)) |
1647 | goto out1; |
1648 | /* |
1649 | * Don't move a mount tree containing unbindable mounts to a destination |
1650 | * mount which is shared. |
1651 | */ |
1652 | if (IS_MNT_SHARED(path->mnt) && |
1653 | tree_contains_unbindable(old_path.mnt)) |
1654 | goto out1; |
1655 | err = -ELOOP; |
1656 | for (p = path->mnt; p->mnt_parent != p; p = p->mnt_parent) |
1657 | if (p == old_path.mnt) |
1658 | goto out1; |
1659 | |
1660 | err = attach_recursive_mnt(old_path.mnt, path, &parent_path); |
1661 | if (err) |
1662 | goto out1; |
1663 | |
1664 | /* if the mount is moved, it should no longer be expire |
1665 | * automatically */ |
1666 | list_del_init(&old_path.mnt->mnt_expire); |
1667 | out1: |
1668 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
1669 | out: |
1670 | up_write(&namespace_sem); |
1671 | if (!err) |
1672 | path_put(&parent_path); |
1673 | path_put(&old_path); |
1674 | return err; |
1675 | } |
1676 | |
1677 | /* |
1678 | * create a new mount for userspace and request it to be added into the |
1679 | * namespace's tree |
1680 | */ |
1681 | static int do_new_mount(struct path *path, char *type, int flags, |
1682 | int mnt_flags, char *name, void *data) |
1683 | { |
1684 | struct vfsmount *mnt; |
1685 | |
1686 | if (!type) |
1687 | return -EINVAL; |
1688 | |
1689 | /* we need capabilities... */ |
1690 | if (!capable(CAP_SYS_ADMIN)) |
1691 | return -EPERM; |
1692 | |
1693 | lock_kernel(); |
1694 | mnt = do_kern_mount(type, flags, name, data); |
1695 | unlock_kernel(); |
1696 | if (IS_ERR(mnt)) |
1697 | return PTR_ERR(mnt); |
1698 | |
1699 | return do_add_mount(mnt, path, mnt_flags, NULL); |
1700 | } |
1701 | |
1702 | /* |
1703 | * add a mount into a namespace's mount tree |
1704 | * - provide the option of adding the new mount to an expiration list |
1705 | */ |
1706 | int do_add_mount(struct vfsmount *newmnt, struct path *path, |
1707 | int mnt_flags, struct list_head *fslist) |
1708 | { |
1709 | int err; |
1710 | |
1711 | mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL); |
1712 | |
1713 | down_write(&namespace_sem); |
1714 | /* Something was mounted here while we slept */ |
1715 | while (d_mountpoint(path->dentry) && |
1716 | follow_down(path)) |
1717 | ; |
1718 | err = -EINVAL; |
1719 | if (!(mnt_flags & MNT_SHRINKABLE) && !check_mnt(path->mnt)) |
1720 | goto unlock; |
1721 | |
1722 | /* Refuse the same filesystem on the same mount point */ |
1723 | err = -EBUSY; |
1724 | if (path->mnt->mnt_sb == newmnt->mnt_sb && |
1725 | path->mnt->mnt_root == path->dentry) |
1726 | goto unlock; |
1727 | |
1728 | err = -EINVAL; |
1729 | if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode)) |
1730 | goto unlock; |
1731 | |
1732 | newmnt->mnt_flags = mnt_flags; |
1733 | if ((err = graft_tree(newmnt, path))) |
1734 | goto unlock; |
1735 | |
1736 | if (fslist) /* add to the specified expiration list */ |
1737 | list_add_tail(&newmnt->mnt_expire, fslist); |
1738 | |
1739 | up_write(&namespace_sem); |
1740 | return 0; |
1741 | |
1742 | unlock: |
1743 | up_write(&namespace_sem); |
1744 | mntput(newmnt); |
1745 | return err; |
1746 | } |
1747 | |
1748 | EXPORT_SYMBOL_GPL(do_add_mount); |
1749 | |
1750 | /* |
1751 | * process a list of expirable mountpoints with the intent of discarding any |
1752 | * mountpoints that aren't in use and haven't been touched since last we came |
1753 | * here |
1754 | */ |
1755 | void mark_mounts_for_expiry(struct list_head *mounts) |
1756 | { |
1757 | struct vfsmount *mnt, *next; |
1758 | LIST_HEAD(graveyard); |
1759 | LIST_HEAD(umounts); |
1760 | |
1761 | if (list_empty(mounts)) |
1762 | return; |
1763 | |
1764 | down_write(&namespace_sem); |
1765 | spin_lock(&vfsmount_lock); |
1766 | |
1767 | /* extract from the expiration list every vfsmount that matches the |
1768 | * following criteria: |
1769 | * - only referenced by its parent vfsmount |
1770 | * - still marked for expiry (marked on the last call here; marks are |
1771 | * cleared by mntput()) |
1772 | */ |
1773 | list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { |
1774 | if (!xchg(&mnt->mnt_expiry_mark, 1) || |
1775 | propagate_mount_busy(mnt, 1)) |
1776 | continue; |
1777 | list_move(&mnt->mnt_expire, &graveyard); |
1778 | } |
1779 | while (!list_empty(&graveyard)) { |
1780 | mnt = list_first_entry(&graveyard, struct vfsmount, mnt_expire); |
1781 | touch_mnt_namespace(mnt->mnt_ns); |
1782 | umount_tree(mnt, 1, &umounts); |
1783 | } |
1784 | spin_unlock(&vfsmount_lock); |
1785 | up_write(&namespace_sem); |
1786 | |
1787 | release_mounts(&umounts); |
1788 | } |
1789 | |
1790 | EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); |
1791 | |
1792 | /* |
1793 | * Ripoff of 'select_parent()' |
1794 | * |
1795 | * search the list of submounts for a given mountpoint, and move any |
1796 | * shrinkable submounts to the 'graveyard' list. |
1797 | */ |
1798 | static int select_submounts(struct vfsmount *parent, struct list_head *graveyard) |
1799 | { |
1800 | struct vfsmount *this_parent = parent; |
1801 | struct list_head *next; |
1802 | int found = 0; |
1803 | |
1804 | repeat: |
1805 | next = this_parent->mnt_mounts.next; |
1806 | resume: |
1807 | while (next != &this_parent->mnt_mounts) { |
1808 | struct list_head *tmp = next; |
1809 | struct vfsmount *mnt = list_entry(tmp, struct vfsmount, mnt_child); |
1810 | |
1811 | next = tmp->next; |
1812 | if (!(mnt->mnt_flags & MNT_SHRINKABLE)) |
1813 | continue; |
1814 | /* |
1815 | * Descend a level if the d_mounts list is non-empty. |
1816 | */ |
1817 | if (!list_empty(&mnt->mnt_mounts)) { |
1818 | this_parent = mnt; |
1819 | goto repeat; |
1820 | } |
1821 | |
1822 | if (!propagate_mount_busy(mnt, 1)) { |
1823 | list_move_tail(&mnt->mnt_expire, graveyard); |
1824 | found++; |
1825 | } |
1826 | } |
1827 | /* |
1828 | * All done at this level ... ascend and resume the search |
1829 | */ |
1830 | if (this_parent != parent) { |
1831 | next = this_parent->mnt_child.next; |
1832 | this_parent = this_parent->mnt_parent; |
1833 | goto resume; |
1834 | } |
1835 | return found; |
1836 | } |
1837 | |
1838 | /* |
1839 | * process a list of expirable mountpoints with the intent of discarding any |
1840 | * submounts of a specific parent mountpoint |
1841 | */ |
1842 | static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts) |
1843 | { |
1844 | LIST_HEAD(graveyard); |
1845 | struct vfsmount *m; |
1846 | |
1847 | /* extract submounts of 'mountpoint' from the expiration list */ |
1848 | while (select_submounts(mnt, &graveyard)) { |
1849 | while (!list_empty(&graveyard)) { |
1850 | m = list_first_entry(&graveyard, struct vfsmount, |
1851 | mnt_expire); |
1852 | touch_mnt_namespace(m->mnt_ns); |
1853 | umount_tree(m, 1, umounts); |
1854 | } |
1855 | } |
1856 | } |
1857 | |
1858 | /* |
1859 | * Some copy_from_user() implementations do not return the exact number of |
1860 | * bytes remaining to copy on a fault. But copy_mount_options() requires that. |
1861 | * Note that this function differs from copy_from_user() in that it will oops |
1862 | * on bad values of `to', rather than returning a short copy. |
1863 | */ |
1864 | static long exact_copy_from_user(void *to, const void __user * from, |
1865 | unsigned long n) |
1866 | { |
1867 | char *t = to; |
1868 | const char __user *f = from; |
1869 | char c; |
1870 | |
1871 | if (!access_ok(VERIFY_READ, from, n)) |
1872 | return n; |
1873 | |
1874 | while (n) { |
1875 | if (__get_user(c, f)) { |
1876 | memset(t, 0, n); |
1877 | break; |
1878 | } |
1879 | *t++ = c; |
1880 | f++; |
1881 | n--; |
1882 | } |
1883 | return n; |
1884 | } |
1885 | |
1886 | int copy_mount_options(const void __user * data, unsigned long *where) |
1887 | { |
1888 | int i; |
1889 | unsigned long page; |
1890 | unsigned long size; |
1891 | |
1892 | *where = 0; |
1893 | if (!data) |
1894 | return 0; |
1895 | |
1896 | if (!(page = __get_free_page(GFP_KERNEL))) |
1897 | return -ENOMEM; |
1898 | |
1899 | /* We only care that *some* data at the address the user |
1900 | * gave us is valid. Just in case, we'll zero |
1901 | * the remainder of the page. |
1902 | */ |
1903 | /* copy_from_user cannot cross TASK_SIZE ! */ |
1904 | size = TASK_SIZE - (unsigned long)data; |
1905 | if (size > PAGE_SIZE) |
1906 | size = PAGE_SIZE; |
1907 | |
1908 | i = size - exact_copy_from_user((void *)page, data, size); |
1909 | if (!i) { |
1910 | free_page(page); |
1911 | return -EFAULT; |
1912 | } |
1913 | if (i != PAGE_SIZE) |
1914 | memset((char *)page + i, 0, PAGE_SIZE - i); |
1915 | *where = page; |
1916 | return 0; |
1917 | } |
1918 | |
1919 | int copy_mount_string(const void __user *data, char **where) |
1920 | { |
1921 | char *tmp; |
1922 | |
1923 | if (!data) { |
1924 | *where = NULL; |
1925 | return 0; |
1926 | } |
1927 | |
1928 | tmp = strndup_user(data, PAGE_SIZE); |
1929 | if (IS_ERR(tmp)) |
1930 | return PTR_ERR(tmp); |
1931 | |
1932 | *where = tmp; |
1933 | return 0; |
1934 | } |
1935 | |
1936 | /* |
1937 | * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to |
1938 | * be given to the mount() call (ie: read-only, no-dev, no-suid etc). |
1939 | * |
1940 | * data is a (void *) that can point to any structure up to |
1941 | * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent |
1942 | * information (or be NULL). |
1943 | * |
1944 | * Pre-0.97 versions of mount() didn't have a flags word. |
1945 | * When the flags word was introduced its top half was required |
1946 | * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. |
1947 | * Therefore, if this magic number is present, it carries no information |
1948 | * and must be discarded. |
1949 | */ |
1950 | long do_mount(char *dev_name, char *dir_name, char *type_page, |
1951 | unsigned long flags, void *data_page) |
1952 | { |
1953 | struct path path; |
1954 | int retval = 0; |
1955 | int mnt_flags = 0; |
1956 | |
1957 | /* Discard magic */ |
1958 | if ((flags & MS_MGC_MSK) == MS_MGC_VAL) |
1959 | flags &= ~MS_MGC_MSK; |
1960 | |
1961 | /* Basic sanity checks */ |
1962 | |
1963 | if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) |
1964 | return -EINVAL; |
1965 | |
1966 | if (data_page) |
1967 | ((char *)data_page)[PAGE_SIZE - 1] = 0; |
1968 | |
1969 | /* ... and get the mountpoint */ |
1970 | retval = kern_path(dir_name, LOOKUP_FOLLOW, &path); |
1971 | if (retval) |
1972 | return retval; |
1973 | |
1974 | retval = security_sb_mount(dev_name, &path, |
1975 | type_page, flags, data_page); |
1976 | if (retval) |
1977 | goto dput_out; |
1978 | |
1979 | /* Default to relatime unless overriden */ |
1980 | if (!(flags & MS_NOATIME)) |
1981 | mnt_flags |= MNT_RELATIME; |
1982 | |
1983 | /* Separate the per-mountpoint flags */ |
1984 | if (flags & MS_NOSUID) |
1985 | mnt_flags |= MNT_NOSUID; |
1986 | if (flags & MS_NODEV) |
1987 | mnt_flags |= MNT_NODEV; |
1988 | if (flags & MS_NOEXEC) |
1989 | mnt_flags |= MNT_NOEXEC; |
1990 | if (flags & MS_NOATIME) |
1991 | mnt_flags |= MNT_NOATIME; |
1992 | if (flags & MS_NODIRATIME) |
1993 | mnt_flags |= MNT_NODIRATIME; |
1994 | if (flags & MS_STRICTATIME) |
1995 | mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); |
1996 | if (flags & MS_RDONLY) |
1997 | mnt_flags |= MNT_READONLY; |
1998 | |
1999 | flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | |
2000 | MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT | |
2001 | MS_STRICTATIME); |
2002 | |
2003 | if (flags & MS_REMOUNT) |
2004 | retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags, |
2005 | data_page); |
2006 | else if (flags & MS_BIND) |
2007 | retval = do_loopback(&path, dev_name, flags & MS_REC); |
2008 | else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
2009 | retval = do_change_type(&path, flags); |
2010 | else if (flags & MS_MOVE) |
2011 | retval = do_move_mount(&path, dev_name); |
2012 | else |
2013 | retval = do_new_mount(&path, type_page, flags, mnt_flags, |
2014 | dev_name, data_page); |
2015 | dput_out: |
2016 | path_put(&path); |
2017 | return retval; |
2018 | } |
2019 | |
2020 | static struct mnt_namespace *alloc_mnt_ns(void) |
2021 | { |
2022 | struct mnt_namespace *new_ns; |
2023 | |
2024 | new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); |
2025 | if (!new_ns) |
2026 | return ERR_PTR(-ENOMEM); |
2027 | atomic_set(&new_ns->count, 1); |
2028 | new_ns->root = NULL; |
2029 | INIT_LIST_HEAD(&new_ns->list); |
2030 | init_waitqueue_head(&new_ns->poll); |
2031 | new_ns->event = 0; |
2032 | return new_ns; |
2033 | } |
2034 | |
2035 | /* |
2036 | * Allocate a new namespace structure and populate it with contents |
2037 | * copied from the namespace of the passed in task structure. |
2038 | */ |
2039 | static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns, |
2040 | struct fs_struct *fs) |
2041 | { |
2042 | struct mnt_namespace *new_ns; |
2043 | struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; |
2044 | struct vfsmount *p, *q; |
2045 | |
2046 | new_ns = alloc_mnt_ns(); |
2047 | if (IS_ERR(new_ns)) |
2048 | return new_ns; |
2049 | |
2050 | down_write(&namespace_sem); |
2051 | /* First pass: copy the tree topology */ |
2052 | new_ns->root = copy_tree(mnt_ns->root, mnt_ns->root->mnt_root, |
2053 | CL_COPY_ALL | CL_EXPIRE); |
2054 | if (!new_ns->root) { |
2055 | up_write(&namespace_sem); |
2056 | kfree(new_ns); |
2057 | return ERR_PTR(-ENOMEM); |
2058 | } |
2059 | spin_lock(&vfsmount_lock); |
2060 | list_add_tail(&new_ns->list, &new_ns->root->mnt_list); |
2061 | spin_unlock(&vfsmount_lock); |
2062 | |
2063 | /* |
2064 | * Second pass: switch the tsk->fs->* elements and mark new vfsmounts |
2065 | * as belonging to new namespace. We have already acquired a private |
2066 | * fs_struct, so tsk->fs->lock is not needed. |
2067 | */ |
2068 | p = mnt_ns->root; |
2069 | q = new_ns->root; |
2070 | while (p) { |
2071 | q->mnt_ns = new_ns; |
2072 | if (fs) { |
2073 | if (p == fs->root.mnt) { |
2074 | rootmnt = p; |
2075 | fs->root.mnt = mntget(q); |
2076 | } |
2077 | if (p == fs->pwd.mnt) { |
2078 | pwdmnt = p; |
2079 | fs->pwd.mnt = mntget(q); |
2080 | } |
2081 | } |
2082 | p = next_mnt(p, mnt_ns->root); |
2083 | q = next_mnt(q, new_ns->root); |
2084 | } |
2085 | up_write(&namespace_sem); |
2086 | |
2087 | if (rootmnt) |
2088 | mntput(rootmnt); |
2089 | if (pwdmnt) |
2090 | mntput(pwdmnt); |
2091 | |
2092 | return new_ns; |
2093 | } |
2094 | |
2095 | struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, |
2096 | struct fs_struct *new_fs) |
2097 | { |
2098 | struct mnt_namespace *new_ns; |
2099 | |
2100 | BUG_ON(!ns); |
2101 | get_mnt_ns(ns); |
2102 | |
2103 | if (!(flags & CLONE_NEWNS)) |
2104 | return ns; |
2105 | |
2106 | new_ns = dup_mnt_ns(ns, new_fs); |
2107 | |
2108 | put_mnt_ns(ns); |
2109 | return new_ns; |
2110 | } |
2111 | |
2112 | /** |
2113 | * create_mnt_ns - creates a private namespace and adds a root filesystem |
2114 | * @mnt: pointer to the new root filesystem mountpoint |
2115 | */ |
2116 | struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt) |
2117 | { |
2118 | struct mnt_namespace *new_ns; |
2119 | |
2120 | new_ns = alloc_mnt_ns(); |
2121 | if (!IS_ERR(new_ns)) { |
2122 | mnt->mnt_ns = new_ns; |
2123 | new_ns->root = mnt; |
2124 | list_add(&new_ns->list, &new_ns->root->mnt_list); |
2125 | } |
2126 | return new_ns; |
2127 | } |
2128 | EXPORT_SYMBOL(create_mnt_ns); |
2129 | |
2130 | SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, |
2131 | char __user *, type, unsigned long, flags, void __user *, data) |
2132 | { |
2133 | int ret; |
2134 | char *kernel_type; |
2135 | char *kernel_dir; |
2136 | char *kernel_dev; |
2137 | unsigned long data_page; |
2138 | |
2139 | ret = copy_mount_string(type, &kernel_type); |
2140 | if (ret < 0) |
2141 | goto out_type; |
2142 | |
2143 | kernel_dir = getname(dir_name); |
2144 | if (IS_ERR(kernel_dir)) { |
2145 | ret = PTR_ERR(kernel_dir); |
2146 | goto out_dir; |
2147 | } |
2148 | |
2149 | ret = copy_mount_string(dev_name, &kernel_dev); |
2150 | if (ret < 0) |
2151 | goto out_dev; |
2152 | |
2153 | ret = copy_mount_options(data, &data_page); |
2154 | if (ret < 0) |
2155 | goto out_data; |
2156 | |
2157 | ret = do_mount(kernel_dev, kernel_dir, kernel_type, flags, |
2158 | (void *) data_page); |
2159 | |
2160 | free_page(data_page); |
2161 | out_data: |
2162 | kfree(kernel_dev); |
2163 | out_dev: |
2164 | putname(kernel_dir); |
2165 | out_dir: |
2166 | kfree(kernel_type); |
2167 | out_type: |
2168 | return ret; |
2169 | } |
2170 | |
2171 | /* |
2172 | * pivot_root Semantics: |
2173 | * Moves the root file system of the current process to the directory put_old, |
2174 | * makes new_root as the new root file system of the current process, and sets |
2175 | * root/cwd of all processes which had them on the current root to new_root. |
2176 | * |
2177 | * Restrictions: |
2178 | * The new_root and put_old must be directories, and must not be on the |
2179 | * same file system as the current process root. The put_old must be |
2180 | * underneath new_root, i.e. adding a non-zero number of /.. to the string |
2181 | * pointed to by put_old must yield the same directory as new_root. No other |
2182 | * file system may be mounted on put_old. After all, new_root is a mountpoint. |
2183 | * |
2184 | * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. |
2185 | * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives |
2186 | * in this situation. |
2187 | * |
2188 | * Notes: |
2189 | * - we don't move root/cwd if they are not at the root (reason: if something |
2190 | * cared enough to change them, it's probably wrong to force them elsewhere) |
2191 | * - it's okay to pick a root that isn't the root of a file system, e.g. |
2192 | * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, |
2193 | * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root |
2194 | * first. |
2195 | */ |
2196 | SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, |
2197 | const char __user *, put_old) |
2198 | { |
2199 | struct vfsmount *tmp; |
2200 | struct path new, old, parent_path, root_parent, root; |
2201 | int error; |
2202 | |
2203 | if (!capable(CAP_SYS_ADMIN)) |
2204 | return -EPERM; |
2205 | |
2206 | error = user_path_dir(new_root, &new); |
2207 | if (error) |
2208 | goto out0; |
2209 | error = -EINVAL; |
2210 | if (!check_mnt(new.mnt)) |
2211 | goto out1; |
2212 | |
2213 | error = user_path_dir(put_old, &old); |
2214 | if (error) |
2215 | goto out1; |
2216 | |
2217 | error = security_sb_pivotroot(&old, &new); |
2218 | if (error) { |
2219 | path_put(&old); |
2220 | goto out1; |
2221 | } |
2222 | |
2223 | read_lock(¤t->fs->lock); |
2224 | root = current->fs->root; |
2225 | path_get(¤t->fs->root); |
2226 | read_unlock(¤t->fs->lock); |
2227 | down_write(&namespace_sem); |
2228 | mutex_lock(&old.dentry->d_inode->i_mutex); |
2229 | error = -EINVAL; |
2230 | if (IS_MNT_SHARED(old.mnt) || |
2231 | IS_MNT_SHARED(new.mnt->mnt_parent) || |
2232 | IS_MNT_SHARED(root.mnt->mnt_parent)) |
2233 | goto out2; |
2234 | if (!check_mnt(root.mnt)) |
2235 | goto out2; |
2236 | error = -ENOENT; |
2237 | if (IS_DEADDIR(new.dentry->d_inode)) |
2238 | goto out2; |
2239 | if (d_unlinked(new.dentry)) |
2240 | goto out2; |
2241 | if (d_unlinked(old.dentry)) |
2242 | goto out2; |
2243 | error = -EBUSY; |
2244 | if (new.mnt == root.mnt || |
2245 | old.mnt == root.mnt) |
2246 | goto out2; /* loop, on the same file system */ |
2247 | error = -EINVAL; |
2248 | if (root.mnt->mnt_root != root.dentry) |
2249 | goto out2; /* not a mountpoint */ |
2250 | if (root.mnt->mnt_parent == root.mnt) |
2251 | goto out2; /* not attached */ |
2252 | if (new.mnt->mnt_root != new.dentry) |
2253 | goto out2; /* not a mountpoint */ |
2254 | if (new.mnt->mnt_parent == new.mnt) |
2255 | goto out2; /* not attached */ |
2256 | /* make sure we can reach put_old from new_root */ |
2257 | tmp = old.mnt; |
2258 | spin_lock(&vfsmount_lock); |
2259 | if (tmp != new.mnt) { |
2260 | for (;;) { |
2261 | if (tmp->mnt_parent == tmp) |
2262 | goto out3; /* already mounted on put_old */ |
2263 | if (tmp->mnt_parent == new.mnt) |
2264 | break; |
2265 | tmp = tmp->mnt_parent; |
2266 | } |
2267 | if (!is_subdir(tmp->mnt_mountpoint, new.dentry)) |
2268 | goto out3; |
2269 | } else if (!is_subdir(old.dentry, new.dentry)) |
2270 | goto out3; |
2271 | detach_mnt(new.mnt, &parent_path); |
2272 | detach_mnt(root.mnt, &root_parent); |
2273 | /* mount old root on put_old */ |
2274 | attach_mnt(root.mnt, &old); |
2275 | /* mount new_root on / */ |
2276 | attach_mnt(new.mnt, &root_parent); |
2277 | touch_mnt_namespace(current->nsproxy->mnt_ns); |
2278 | spin_unlock(&vfsmount_lock); |
2279 | chroot_fs_refs(&root, &new); |
2280 | security_sb_post_pivotroot(&root, &new); |
2281 | error = 0; |
2282 | path_put(&root_parent); |
2283 | path_put(&parent_path); |
2284 | out2: |
2285 | mutex_unlock(&old.dentry->d_inode->i_mutex); |
2286 | up_write(&namespace_sem); |
2287 | path_put(&root); |
2288 | path_put(&old); |
2289 | out1: |
2290 | path_put(&new); |
2291 | out0: |
2292 | return error; |
2293 | out3: |
2294 | spin_unlock(&vfsmount_lock); |
2295 | goto out2; |
2296 | } |
2297 | |
2298 | static void __init init_mount_tree(void) |
2299 | { |
2300 | struct vfsmount *mnt; |
2301 | struct mnt_namespace *ns; |
2302 | struct path root; |
2303 | |
2304 | mnt = do_kern_mount("rootfs", 0, "rootfs", NULL); |
2305 | if (IS_ERR(mnt)) |
2306 | panic("Can't create rootfs"); |
2307 | ns = create_mnt_ns(mnt); |
2308 | if (IS_ERR(ns)) |
2309 | panic("Can't allocate initial namespace"); |
2310 | |
2311 | init_task.nsproxy->mnt_ns = ns; |
2312 | get_mnt_ns(ns); |
2313 | |
2314 | root.mnt = ns->root; |
2315 | root.dentry = ns->root->mnt_root; |
2316 | |
2317 | set_fs_pwd(current->fs, &root); |
2318 | set_fs_root(current->fs, &root); |
2319 | } |
2320 | |
2321 | void __init mnt_init(void) |
2322 | { |
2323 | unsigned u; |
2324 | int err; |
2325 | |
2326 | init_rwsem(&namespace_sem); |
2327 | |
2328 | mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount), |
2329 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); |
2330 | |
2331 | mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); |
2332 | |
2333 | if (!mount_hashtable) |
2334 | panic("Failed to allocate mount hash table\n"); |
2335 | |
2336 | printk("Mount-cache hash table entries: %lu\n", HASH_SIZE); |
2337 | |
2338 | for (u = 0; u < HASH_SIZE; u++) |
2339 | INIT_LIST_HEAD(&mount_hashtable[u]); |
2340 | |
2341 | err = sysfs_init(); |
2342 | if (err) |
2343 | printk(KERN_WARNING "%s: sysfs_init error: %d\n", |
2344 | __func__, err); |
2345 | fs_kobj = kobject_create_and_add("fs", NULL); |
2346 | if (!fs_kobj) |
2347 | printk(KERN_WARNING "%s: kobj create error\n", __func__); |
2348 | init_rootfs(); |
2349 | init_mount_tree(); |
2350 | } |
2351 | |
2352 | void put_mnt_ns(struct mnt_namespace *ns) |
2353 | { |
2354 | LIST_HEAD(umount_list); |
2355 | |
2356 | if (!atomic_dec_and_test(&ns->count)) |
2357 | return; |
2358 | down_write(&namespace_sem); |
2359 | spin_lock(&vfsmount_lock); |
2360 | umount_tree(ns->root, 0, &umount_list); |
2361 | spin_unlock(&vfsmount_lock); |
2362 | up_write(&namespace_sem); |
2363 | release_mounts(&umount_list); |
2364 | kfree(ns); |
2365 | } |
2366 | EXPORT_SYMBOL(put_mnt_ns); |
2367 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
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