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1 | // SPDX-License-Identifier: GPL-2.0-only | |
2 | /* | |
3 | * linux/fs/namespace.c | |
4 | * | |
5 | * (C) Copyright Al Viro 2000, 2001 | |
6 | * | |
7 | * Based on code from fs/super.c, copyright Linus Torvalds and others. | |
8 | * Heavily rewritten. | |
9 | */ | |
10 | ||
11 | #include <linux/syscalls.h> | |
12 | #include <linux/export.h> | |
13 | #include <linux/capability.h> | |
14 | #include <linux/mnt_namespace.h> | |
15 | #include <linux/user_namespace.h> | |
16 | #include <linux/namei.h> | |
17 | #include <linux/security.h> | |
18 | #include <linux/cred.h> | |
19 | #include <linux/idr.h> | |
20 | #include <linux/init.h> /* init_rootfs */ | |
21 | #include <linux/fs_struct.h> /* get_fs_root et.al. */ | |
22 | #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */ | |
23 | #include <linux/file.h> | |
24 | #include <linux/uaccess.h> | |
25 | #include <linux/proc_ns.h> | |
26 | #include <linux/magic.h> | |
27 | #include <linux/memblock.h> | |
28 | #include <linux/proc_fs.h> | |
29 | #include <linux/task_work.h> | |
30 | #include <linux/sched/task.h> | |
31 | #include <uapi/linux/mount.h> | |
32 | #include <linux/fs_context.h> | |
33 | #include <linux/shmem_fs.h> | |
34 | ||
35 | #include "pnode.h" | |
36 | #include "internal.h" | |
37 | ||
38 | /* Maximum number of mounts in a mount namespace */ | |
39 | unsigned int sysctl_mount_max __read_mostly = 100000; | |
40 | ||
41 | static unsigned int m_hash_mask __read_mostly; | |
42 | static unsigned int m_hash_shift __read_mostly; | |
43 | static unsigned int mp_hash_mask __read_mostly; | |
44 | static unsigned int mp_hash_shift __read_mostly; | |
45 | ||
46 | static __initdata unsigned long mhash_entries; | |
47 | static int __init set_mhash_entries(char *str) | |
48 | { | |
49 | if (!str) | |
50 | return 0; | |
51 | mhash_entries = simple_strtoul(str, &str, 0); | |
52 | return 1; | |
53 | } | |
54 | __setup("mhash_entries=", set_mhash_entries); | |
55 | ||
56 | static __initdata unsigned long mphash_entries; | |
57 | static int __init set_mphash_entries(char *str) | |
58 | { | |
59 | if (!str) | |
60 | return 0; | |
61 | mphash_entries = simple_strtoul(str, &str, 0); | |
62 | return 1; | |
63 | } | |
64 | __setup("mphash_entries=", set_mphash_entries); | |
65 | ||
66 | static u64 event; | |
67 | static DEFINE_IDA(mnt_id_ida); | |
68 | static DEFINE_IDA(mnt_group_ida); | |
69 | ||
70 | static struct hlist_head *mount_hashtable __read_mostly; | |
71 | static struct hlist_head *mountpoint_hashtable __read_mostly; | |
72 | static struct kmem_cache *mnt_cache __read_mostly; | |
73 | static DECLARE_RWSEM(namespace_sem); | |
74 | static HLIST_HEAD(unmounted); /* protected by namespace_sem */ | |
75 | static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */ | |
76 | ||
77 | struct mount_kattr { | |
78 | unsigned int attr_set; | |
79 | unsigned int attr_clr; | |
80 | unsigned int propagation; | |
81 | unsigned int lookup_flags; | |
82 | bool recurse; | |
83 | struct user_namespace *mnt_userns; | |
84 | }; | |
85 | ||
86 | /* /sys/fs */ | |
87 | struct kobject *fs_kobj; | |
88 | EXPORT_SYMBOL_GPL(fs_kobj); | |
89 | ||
90 | /* | |
91 | * vfsmount lock may be taken for read to prevent changes to the | |
92 | * vfsmount hash, ie. during mountpoint lookups or walking back | |
93 | * up the tree. | |
94 | * | |
95 | * It should be taken for write in all cases where the vfsmount | |
96 | * tree or hash is modified or when a vfsmount structure is modified. | |
97 | */ | |
98 | __cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock); | |
99 | ||
100 | static inline void lock_mount_hash(void) | |
101 | { | |
102 | write_seqlock(&mount_lock); | |
103 | } | |
104 | ||
105 | static inline void unlock_mount_hash(void) | |
106 | { | |
107 | write_sequnlock(&mount_lock); | |
108 | } | |
109 | ||
110 | static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry) | |
111 | { | |
112 | unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); | |
113 | tmp += ((unsigned long)dentry / L1_CACHE_BYTES); | |
114 | tmp = tmp + (tmp >> m_hash_shift); | |
115 | return &mount_hashtable[tmp & m_hash_mask]; | |
116 | } | |
117 | ||
118 | static inline struct hlist_head *mp_hash(struct dentry *dentry) | |
119 | { | |
120 | unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES); | |
121 | tmp = tmp + (tmp >> mp_hash_shift); | |
122 | return &mountpoint_hashtable[tmp & mp_hash_mask]; | |
123 | } | |
124 | ||
125 | static int mnt_alloc_id(struct mount *mnt) | |
126 | { | |
127 | int res = ida_alloc(&mnt_id_ida, GFP_KERNEL); | |
128 | ||
129 | if (res < 0) | |
130 | return res; | |
131 | mnt->mnt_id = res; | |
132 | return 0; | |
133 | } | |
134 | ||
135 | static void mnt_free_id(struct mount *mnt) | |
136 | { | |
137 | ida_free(&mnt_id_ida, mnt->mnt_id); | |
138 | } | |
139 | ||
140 | /* | |
141 | * Allocate a new peer group ID | |
142 | */ | |
143 | static int mnt_alloc_group_id(struct mount *mnt) | |
144 | { | |
145 | int res = ida_alloc_min(&mnt_group_ida, 1, GFP_KERNEL); | |
146 | ||
147 | if (res < 0) | |
148 | return res; | |
149 | mnt->mnt_group_id = res; | |
150 | return 0; | |
151 | } | |
152 | ||
153 | /* | |
154 | * Release a peer group ID | |
155 | */ | |
156 | void mnt_release_group_id(struct mount *mnt) | |
157 | { | |
158 | ida_free(&mnt_group_ida, mnt->mnt_group_id); | |
159 | mnt->mnt_group_id = 0; | |
160 | } | |
161 | ||
162 | /* | |
163 | * vfsmount lock must be held for read | |
164 | */ | |
165 | static inline void mnt_add_count(struct mount *mnt, int n) | |
166 | { | |
167 | #ifdef CONFIG_SMP | |
168 | this_cpu_add(mnt->mnt_pcp->mnt_count, n); | |
169 | #else | |
170 | preempt_disable(); | |
171 | mnt->mnt_count += n; | |
172 | preempt_enable(); | |
173 | #endif | |
174 | } | |
175 | ||
176 | /* | |
177 | * vfsmount lock must be held for write | |
178 | */ | |
179 | int mnt_get_count(struct mount *mnt) | |
180 | { | |
181 | #ifdef CONFIG_SMP | |
182 | int count = 0; | |
183 | int cpu; | |
184 | ||
185 | for_each_possible_cpu(cpu) { | |
186 | count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count; | |
187 | } | |
188 | ||
189 | return count; | |
190 | #else | |
191 | return mnt->mnt_count; | |
192 | #endif | |
193 | } | |
194 | ||
195 | static struct mount *alloc_vfsmnt(const char *name) | |
196 | { | |
197 | struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); | |
198 | if (mnt) { | |
199 | int err; | |
200 | ||
201 | err = mnt_alloc_id(mnt); | |
202 | if (err) | |
203 | goto out_free_cache; | |
204 | ||
205 | if (name) { | |
206 | mnt->mnt_devname = kstrdup_const(name, | |
207 | GFP_KERNEL_ACCOUNT); | |
208 | if (!mnt->mnt_devname) | |
209 | goto out_free_id; | |
210 | } | |
211 | ||
212 | #ifdef CONFIG_SMP | |
213 | mnt->mnt_pcp = alloc_percpu(struct mnt_pcp); | |
214 | if (!mnt->mnt_pcp) | |
215 | goto out_free_devname; | |
216 | ||
217 | this_cpu_add(mnt->mnt_pcp->mnt_count, 1); | |
218 | #else | |
219 | mnt->mnt_count = 1; | |
220 | mnt->mnt_writers = 0; | |
221 | #endif | |
222 | ||
223 | INIT_HLIST_NODE(&mnt->mnt_hash); | |
224 | INIT_LIST_HEAD(&mnt->mnt_child); | |
225 | INIT_LIST_HEAD(&mnt->mnt_mounts); | |
226 | INIT_LIST_HEAD(&mnt->mnt_list); | |
227 | INIT_LIST_HEAD(&mnt->mnt_expire); | |
228 | INIT_LIST_HEAD(&mnt->mnt_share); | |
229 | INIT_LIST_HEAD(&mnt->mnt_slave_list); | |
230 | INIT_LIST_HEAD(&mnt->mnt_slave); | |
231 | INIT_HLIST_NODE(&mnt->mnt_mp_list); | |
232 | INIT_LIST_HEAD(&mnt->mnt_umounting); | |
233 | INIT_HLIST_HEAD(&mnt->mnt_stuck_children); | |
234 | mnt->mnt.mnt_userns = &init_user_ns; | |
235 | } | |
236 | return mnt; | |
237 | ||
238 | #ifdef CONFIG_SMP | |
239 | out_free_devname: | |
240 | kfree_const(mnt->mnt_devname); | |
241 | #endif | |
242 | out_free_id: | |
243 | mnt_free_id(mnt); | |
244 | out_free_cache: | |
245 | kmem_cache_free(mnt_cache, mnt); | |
246 | return NULL; | |
247 | } | |
248 | ||
249 | /* | |
250 | * Most r/o checks on a fs are for operations that take | |
251 | * discrete amounts of time, like a write() or unlink(). | |
252 | * We must keep track of when those operations start | |
253 | * (for permission checks) and when they end, so that | |
254 | * we can determine when writes are able to occur to | |
255 | * a filesystem. | |
256 | */ | |
257 | /* | |
258 | * __mnt_is_readonly: check whether a mount is read-only | |
259 | * @mnt: the mount to check for its write status | |
260 | * | |
261 | * This shouldn't be used directly ouside of the VFS. | |
262 | * It does not guarantee that the filesystem will stay | |
263 | * r/w, just that it is right *now*. This can not and | |
264 | * should not be used in place of IS_RDONLY(inode). | |
265 | * mnt_want/drop_write() will _keep_ the filesystem | |
266 | * r/w. | |
267 | */ | |
268 | bool __mnt_is_readonly(struct vfsmount *mnt) | |
269 | { | |
270 | return (mnt->mnt_flags & MNT_READONLY) || sb_rdonly(mnt->mnt_sb); | |
271 | } | |
272 | EXPORT_SYMBOL_GPL(__mnt_is_readonly); | |
273 | ||
274 | static inline void mnt_inc_writers(struct mount *mnt) | |
275 | { | |
276 | #ifdef CONFIG_SMP | |
277 | this_cpu_inc(mnt->mnt_pcp->mnt_writers); | |
278 | #else | |
279 | mnt->mnt_writers++; | |
280 | #endif | |
281 | } | |
282 | ||
283 | static inline void mnt_dec_writers(struct mount *mnt) | |
284 | { | |
285 | #ifdef CONFIG_SMP | |
286 | this_cpu_dec(mnt->mnt_pcp->mnt_writers); | |
287 | #else | |
288 | mnt->mnt_writers--; | |
289 | #endif | |
290 | } | |
291 | ||
292 | static unsigned int mnt_get_writers(struct mount *mnt) | |
293 | { | |
294 | #ifdef CONFIG_SMP | |
295 | unsigned int count = 0; | |
296 | int cpu; | |
297 | ||
298 | for_each_possible_cpu(cpu) { | |
299 | count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers; | |
300 | } | |
301 | ||
302 | return count; | |
303 | #else | |
304 | return mnt->mnt_writers; | |
305 | #endif | |
306 | } | |
307 | ||
308 | static int mnt_is_readonly(struct vfsmount *mnt) | |
309 | { | |
310 | if (mnt->mnt_sb->s_readonly_remount) | |
311 | return 1; | |
312 | /* Order wrt setting s_flags/s_readonly_remount in do_remount() */ | |
313 | smp_rmb(); | |
314 | return __mnt_is_readonly(mnt); | |
315 | } | |
316 | ||
317 | /* | |
318 | * Most r/o & frozen checks on a fs are for operations that take discrete | |
319 | * amounts of time, like a write() or unlink(). We must keep track of when | |
320 | * those operations start (for permission checks) and when they end, so that we | |
321 | * can determine when writes are able to occur to a filesystem. | |
322 | */ | |
323 | /** | |
324 | * __mnt_want_write - get write access to a mount without freeze protection | |
325 | * @m: the mount on which to take a write | |
326 | * | |
327 | * This tells the low-level filesystem that a write is about to be performed to | |
328 | * it, and makes sure that writes are allowed (mnt it read-write) before | |
329 | * returning success. This operation does not protect against filesystem being | |
330 | * frozen. When the write operation is finished, __mnt_drop_write() must be | |
331 | * called. This is effectively a refcount. | |
332 | */ | |
333 | int __mnt_want_write(struct vfsmount *m) | |
334 | { | |
335 | struct mount *mnt = real_mount(m); | |
336 | int ret = 0; | |
337 | ||
338 | preempt_disable(); | |
339 | mnt_inc_writers(mnt); | |
340 | /* | |
341 | * The store to mnt_inc_writers must be visible before we pass | |
342 | * MNT_WRITE_HOLD loop below, so that the slowpath can see our | |
343 | * incremented count after it has set MNT_WRITE_HOLD. | |
344 | */ | |
345 | smp_mb(); | |
346 | while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) | |
347 | cpu_relax(); | |
348 | /* | |
349 | * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will | |
350 | * be set to match its requirements. So we must not load that until | |
351 | * MNT_WRITE_HOLD is cleared. | |
352 | */ | |
353 | smp_rmb(); | |
354 | if (mnt_is_readonly(m)) { | |
355 | mnt_dec_writers(mnt); | |
356 | ret = -EROFS; | |
357 | } | |
358 | preempt_enable(); | |
359 | ||
360 | return ret; | |
361 | } | |
362 | ||
363 | /** | |
364 | * mnt_want_write - get write access to a mount | |
365 | * @m: the mount on which to take a write | |
366 | * | |
367 | * This tells the low-level filesystem that a write is about to be performed to | |
368 | * it, and makes sure that writes are allowed (mount is read-write, filesystem | |
369 | * is not frozen) before returning success. When the write operation is | |
370 | * finished, mnt_drop_write() must be called. This is effectively a refcount. | |
371 | */ | |
372 | int mnt_want_write(struct vfsmount *m) | |
373 | { | |
374 | int ret; | |
375 | ||
376 | sb_start_write(m->mnt_sb); | |
377 | ret = __mnt_want_write(m); | |
378 | if (ret) | |
379 | sb_end_write(m->mnt_sb); | |
380 | return ret; | |
381 | } | |
382 | EXPORT_SYMBOL_GPL(mnt_want_write); | |
383 | ||
384 | /** | |
385 | * __mnt_want_write_file - get write access to a file's mount | |
386 | * @file: the file who's mount on which to take a write | |
387 | * | |
388 | * This is like __mnt_want_write, but if the file is already open for writing it | |
389 | * skips incrementing mnt_writers (since the open file already has a reference) | |
390 | * and instead only does the check for emergency r/o remounts. This must be | |
391 | * paired with __mnt_drop_write_file. | |
392 | */ | |
393 | int __mnt_want_write_file(struct file *file) | |
394 | { | |
395 | if (file->f_mode & FMODE_WRITER) { | |
396 | /* | |
397 | * Superblock may have become readonly while there are still | |
398 | * writable fd's, e.g. due to a fs error with errors=remount-ro | |
399 | */ | |
400 | if (__mnt_is_readonly(file->f_path.mnt)) | |
401 | return -EROFS; | |
402 | return 0; | |
403 | } | |
404 | return __mnt_want_write(file->f_path.mnt); | |
405 | } | |
406 | ||
407 | /** | |
408 | * mnt_want_write_file - get write access to a file's mount | |
409 | * @file: the file who's mount on which to take a write | |
410 | * | |
411 | * This is like mnt_want_write, but if the file is already open for writing it | |
412 | * skips incrementing mnt_writers (since the open file already has a reference) | |
413 | * and instead only does the freeze protection and the check for emergency r/o | |
414 | * remounts. This must be paired with mnt_drop_write_file. | |
415 | */ | |
416 | int mnt_want_write_file(struct file *file) | |
417 | { | |
418 | int ret; | |
419 | ||
420 | sb_start_write(file_inode(file)->i_sb); | |
421 | ret = __mnt_want_write_file(file); | |
422 | if (ret) | |
423 | sb_end_write(file_inode(file)->i_sb); | |
424 | return ret; | |
425 | } | |
426 | EXPORT_SYMBOL_GPL(mnt_want_write_file); | |
427 | ||
428 | /** | |
429 | * __mnt_drop_write - give up write access to a mount | |
430 | * @mnt: the mount on which to give up write access | |
431 | * | |
432 | * Tells the low-level filesystem that we are done | |
433 | * performing writes to it. Must be matched with | |
434 | * __mnt_want_write() call above. | |
435 | */ | |
436 | void __mnt_drop_write(struct vfsmount *mnt) | |
437 | { | |
438 | preempt_disable(); | |
439 | mnt_dec_writers(real_mount(mnt)); | |
440 | preempt_enable(); | |
441 | } | |
442 | EXPORT_SYMBOL_GPL(__mnt_drop_write); | |
443 | ||
444 | /** | |
445 | * mnt_drop_write - give up write access to a mount | |
446 | * @mnt: the mount on which to give up write access | |
447 | * | |
448 | * Tells the low-level filesystem that we are done performing writes to it and | |
449 | * also allows filesystem to be frozen again. Must be matched with | |
450 | * mnt_want_write() call above. | |
451 | */ | |
452 | void mnt_drop_write(struct vfsmount *mnt) | |
453 | { | |
454 | __mnt_drop_write(mnt); | |
455 | sb_end_write(mnt->mnt_sb); | |
456 | } | |
457 | EXPORT_SYMBOL_GPL(mnt_drop_write); | |
458 | ||
459 | void __mnt_drop_write_file(struct file *file) | |
460 | { | |
461 | if (!(file->f_mode & FMODE_WRITER)) | |
462 | __mnt_drop_write(file->f_path.mnt); | |
463 | } | |
464 | ||
465 | void mnt_drop_write_file(struct file *file) | |
466 | { | |
467 | __mnt_drop_write_file(file); | |
468 | sb_end_write(file_inode(file)->i_sb); | |
469 | } | |
470 | EXPORT_SYMBOL(mnt_drop_write_file); | |
471 | ||
472 | static inline int mnt_hold_writers(struct mount *mnt) | |
473 | { | |
474 | mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; | |
475 | /* | |
476 | * After storing MNT_WRITE_HOLD, we'll read the counters. This store | |
477 | * should be visible before we do. | |
478 | */ | |
479 | smp_mb(); | |
480 | ||
481 | /* | |
482 | * With writers on hold, if this value is zero, then there are | |
483 | * definitely no active writers (although held writers may subsequently | |
484 | * increment the count, they'll have to wait, and decrement it after | |
485 | * seeing MNT_READONLY). | |
486 | * | |
487 | * It is OK to have counter incremented on one CPU and decremented on | |
488 | * another: the sum will add up correctly. The danger would be when we | |
489 | * sum up each counter, if we read a counter before it is incremented, | |
490 | * but then read another CPU's count which it has been subsequently | |
491 | * decremented from -- we would see more decrements than we should. | |
492 | * MNT_WRITE_HOLD protects against this scenario, because | |
493 | * mnt_want_write first increments count, then smp_mb, then spins on | |
494 | * MNT_WRITE_HOLD, so it can't be decremented by another CPU while | |
495 | * we're counting up here. | |
496 | */ | |
497 | if (mnt_get_writers(mnt) > 0) | |
498 | return -EBUSY; | |
499 | ||
500 | return 0; | |
501 | } | |
502 | ||
503 | static inline void mnt_unhold_writers(struct mount *mnt) | |
504 | { | |
505 | /* | |
506 | * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers | |
507 | * that become unheld will see MNT_READONLY. | |
508 | */ | |
509 | smp_wmb(); | |
510 | mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; | |
511 | } | |
512 | ||
513 | static int mnt_make_readonly(struct mount *mnt) | |
514 | { | |
515 | int ret; | |
516 | ||
517 | ret = mnt_hold_writers(mnt); | |
518 | if (!ret) | |
519 | mnt->mnt.mnt_flags |= MNT_READONLY; | |
520 | mnt_unhold_writers(mnt); | |
521 | return ret; | |
522 | } | |
523 | ||
524 | int sb_prepare_remount_readonly(struct super_block *sb) | |
525 | { | |
526 | struct mount *mnt; | |
527 | int err = 0; | |
528 | ||
529 | /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */ | |
530 | if (atomic_long_read(&sb->s_remove_count)) | |
531 | return -EBUSY; | |
532 | ||
533 | lock_mount_hash(); | |
534 | list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { | |
535 | if (!(mnt->mnt.mnt_flags & MNT_READONLY)) { | |
536 | mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; | |
537 | smp_mb(); | |
538 | if (mnt_get_writers(mnt) > 0) { | |
539 | err = -EBUSY; | |
540 | break; | |
541 | } | |
542 | } | |
543 | } | |
544 | if (!err && atomic_long_read(&sb->s_remove_count)) | |
545 | err = -EBUSY; | |
546 | ||
547 | if (!err) { | |
548 | sb->s_readonly_remount = 1; | |
549 | smp_wmb(); | |
550 | } | |
551 | list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { | |
552 | if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD) | |
553 | mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; | |
554 | } | |
555 | unlock_mount_hash(); | |
556 | ||
557 | return err; | |
558 | } | |
559 | ||
560 | static void free_vfsmnt(struct mount *mnt) | |
561 | { | |
562 | struct user_namespace *mnt_userns; | |
563 | ||
564 | mnt_userns = mnt_user_ns(&mnt->mnt); | |
565 | if (mnt_userns != &init_user_ns) | |
566 | put_user_ns(mnt_userns); | |
567 | kfree_const(mnt->mnt_devname); | |
568 | #ifdef CONFIG_SMP | |
569 | free_percpu(mnt->mnt_pcp); | |
570 | #endif | |
571 | kmem_cache_free(mnt_cache, mnt); | |
572 | } | |
573 | ||
574 | static void delayed_free_vfsmnt(struct rcu_head *head) | |
575 | { | |
576 | free_vfsmnt(container_of(head, struct mount, mnt_rcu)); | |
577 | } | |
578 | ||
579 | /* call under rcu_read_lock */ | |
580 | int __legitimize_mnt(struct vfsmount *bastard, unsigned seq) | |
581 | { | |
582 | struct mount *mnt; | |
583 | if (read_seqretry(&mount_lock, seq)) | |
584 | return 1; | |
585 | if (bastard == NULL) | |
586 | return 0; | |
587 | mnt = real_mount(bastard); | |
588 | mnt_add_count(mnt, 1); | |
589 | smp_mb(); // see mntput_no_expire() | |
590 | if (likely(!read_seqretry(&mount_lock, seq))) | |
591 | return 0; | |
592 | if (bastard->mnt_flags & MNT_SYNC_UMOUNT) { | |
593 | mnt_add_count(mnt, -1); | |
594 | return 1; | |
595 | } | |
596 | lock_mount_hash(); | |
597 | if (unlikely(bastard->mnt_flags & MNT_DOOMED)) { | |
598 | mnt_add_count(mnt, -1); | |
599 | unlock_mount_hash(); | |
600 | return 1; | |
601 | } | |
602 | unlock_mount_hash(); | |
603 | /* caller will mntput() */ | |
604 | return -1; | |
605 | } | |
606 | ||
607 | /* call under rcu_read_lock */ | |
608 | bool legitimize_mnt(struct vfsmount *bastard, unsigned seq) | |
609 | { | |
610 | int res = __legitimize_mnt(bastard, seq); | |
611 | if (likely(!res)) | |
612 | return true; | |
613 | if (unlikely(res < 0)) { | |
614 | rcu_read_unlock(); | |
615 | mntput(bastard); | |
616 | rcu_read_lock(); | |
617 | } | |
618 | return false; | |
619 | } | |
620 | ||
621 | /* | |
622 | * find the first mount at @dentry on vfsmount @mnt. | |
623 | * call under rcu_read_lock() | |
624 | */ | |
625 | struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry) | |
626 | { | |
627 | struct hlist_head *head = m_hash(mnt, dentry); | |
628 | struct mount *p; | |
629 | ||
630 | hlist_for_each_entry_rcu(p, head, mnt_hash) | |
631 | if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) | |
632 | return p; | |
633 | return NULL; | |
634 | } | |
635 | ||
636 | /* | |
637 | * lookup_mnt - Return the first child mount mounted at path | |
638 | * | |
639 | * "First" means first mounted chronologically. If you create the | |
640 | * following mounts: | |
641 | * | |
642 | * mount /dev/sda1 /mnt | |
643 | * mount /dev/sda2 /mnt | |
644 | * mount /dev/sda3 /mnt | |
645 | * | |
646 | * Then lookup_mnt() on the base /mnt dentry in the root mount will | |
647 | * return successively the root dentry and vfsmount of /dev/sda1, then | |
648 | * /dev/sda2, then /dev/sda3, then NULL. | |
649 | * | |
650 | * lookup_mnt takes a reference to the found vfsmount. | |
651 | */ | |
652 | struct vfsmount *lookup_mnt(const struct path *path) | |
653 | { | |
654 | struct mount *child_mnt; | |
655 | struct vfsmount *m; | |
656 | unsigned seq; | |
657 | ||
658 | rcu_read_lock(); | |
659 | do { | |
660 | seq = read_seqbegin(&mount_lock); | |
661 | child_mnt = __lookup_mnt(path->mnt, path->dentry); | |
662 | m = child_mnt ? &child_mnt->mnt : NULL; | |
663 | } while (!legitimize_mnt(m, seq)); | |
664 | rcu_read_unlock(); | |
665 | return m; | |
666 | } | |
667 | ||
668 | static inline void lock_ns_list(struct mnt_namespace *ns) | |
669 | { | |
670 | spin_lock(&ns->ns_lock); | |
671 | } | |
672 | ||
673 | static inline void unlock_ns_list(struct mnt_namespace *ns) | |
674 | { | |
675 | spin_unlock(&ns->ns_lock); | |
676 | } | |
677 | ||
678 | static inline bool mnt_is_cursor(struct mount *mnt) | |
679 | { | |
680 | return mnt->mnt.mnt_flags & MNT_CURSOR; | |
681 | } | |
682 | ||
683 | /* | |
684 | * __is_local_mountpoint - Test to see if dentry is a mountpoint in the | |
685 | * current mount namespace. | |
686 | * | |
687 | * The common case is dentries are not mountpoints at all and that | |
688 | * test is handled inline. For the slow case when we are actually | |
689 | * dealing with a mountpoint of some kind, walk through all of the | |
690 | * mounts in the current mount namespace and test to see if the dentry | |
691 | * is a mountpoint. | |
692 | * | |
693 | * The mount_hashtable is not usable in the context because we | |
694 | * need to identify all mounts that may be in the current mount | |
695 | * namespace not just a mount that happens to have some specified | |
696 | * parent mount. | |
697 | */ | |
698 | bool __is_local_mountpoint(struct dentry *dentry) | |
699 | { | |
700 | struct mnt_namespace *ns = current->nsproxy->mnt_ns; | |
701 | struct mount *mnt; | |
702 | bool is_covered = false; | |
703 | ||
704 | down_read(&namespace_sem); | |
705 | lock_ns_list(ns); | |
706 | list_for_each_entry(mnt, &ns->list, mnt_list) { | |
707 | if (mnt_is_cursor(mnt)) | |
708 | continue; | |
709 | is_covered = (mnt->mnt_mountpoint == dentry); | |
710 | if (is_covered) | |
711 | break; | |
712 | } | |
713 | unlock_ns_list(ns); | |
714 | up_read(&namespace_sem); | |
715 | ||
716 | return is_covered; | |
717 | } | |
718 | ||
719 | static struct mountpoint *lookup_mountpoint(struct dentry *dentry) | |
720 | { | |
721 | struct hlist_head *chain = mp_hash(dentry); | |
722 | struct mountpoint *mp; | |
723 | ||
724 | hlist_for_each_entry(mp, chain, m_hash) { | |
725 | if (mp->m_dentry == dentry) { | |
726 | mp->m_count++; | |
727 | return mp; | |
728 | } | |
729 | } | |
730 | return NULL; | |
731 | } | |
732 | ||
733 | static struct mountpoint *get_mountpoint(struct dentry *dentry) | |
734 | { | |
735 | struct mountpoint *mp, *new = NULL; | |
736 | int ret; | |
737 | ||
738 | if (d_mountpoint(dentry)) { | |
739 | /* might be worth a WARN_ON() */ | |
740 | if (d_unlinked(dentry)) | |
741 | return ERR_PTR(-ENOENT); | |
742 | mountpoint: | |
743 | read_seqlock_excl(&mount_lock); | |
744 | mp = lookup_mountpoint(dentry); | |
745 | read_sequnlock_excl(&mount_lock); | |
746 | if (mp) | |
747 | goto done; | |
748 | } | |
749 | ||
750 | if (!new) | |
751 | new = kmalloc(sizeof(struct mountpoint), GFP_KERNEL); | |
752 | if (!new) | |
753 | return ERR_PTR(-ENOMEM); | |
754 | ||
755 | ||
756 | /* Exactly one processes may set d_mounted */ | |
757 | ret = d_set_mounted(dentry); | |
758 | ||
759 | /* Someone else set d_mounted? */ | |
760 | if (ret == -EBUSY) | |
761 | goto mountpoint; | |
762 | ||
763 | /* The dentry is not available as a mountpoint? */ | |
764 | mp = ERR_PTR(ret); | |
765 | if (ret) | |
766 | goto done; | |
767 | ||
768 | /* Add the new mountpoint to the hash table */ | |
769 | read_seqlock_excl(&mount_lock); | |
770 | new->m_dentry = dget(dentry); | |
771 | new->m_count = 1; | |
772 | hlist_add_head(&new->m_hash, mp_hash(dentry)); | |
773 | INIT_HLIST_HEAD(&new->m_list); | |
774 | read_sequnlock_excl(&mount_lock); | |
775 | ||
776 | mp = new; | |
777 | new = NULL; | |
778 | done: | |
779 | kfree(new); | |
780 | return mp; | |
781 | } | |
782 | ||
783 | /* | |
784 | * vfsmount lock must be held. Additionally, the caller is responsible | |
785 | * for serializing calls for given disposal list. | |
786 | */ | |
787 | static void __put_mountpoint(struct mountpoint *mp, struct list_head *list) | |
788 | { | |
789 | if (!--mp->m_count) { | |
790 | struct dentry *dentry = mp->m_dentry; | |
791 | BUG_ON(!hlist_empty(&mp->m_list)); | |
792 | spin_lock(&dentry->d_lock); | |
793 | dentry->d_flags &= ~DCACHE_MOUNTED; | |
794 | spin_unlock(&dentry->d_lock); | |
795 | dput_to_list(dentry, list); | |
796 | hlist_del(&mp->m_hash); | |
797 | kfree(mp); | |
798 | } | |
799 | } | |
800 | ||
801 | /* called with namespace_lock and vfsmount lock */ | |
802 | static void put_mountpoint(struct mountpoint *mp) | |
803 | { | |
804 | __put_mountpoint(mp, &ex_mountpoints); | |
805 | } | |
806 | ||
807 | static inline int check_mnt(struct mount *mnt) | |
808 | { | |
809 | return mnt->mnt_ns == current->nsproxy->mnt_ns; | |
810 | } | |
811 | ||
812 | /* for aufs, CONFIG_AUFS_BR_FUSE */ | |
813 | int is_current_mnt_ns(struct vfsmount *mnt) | |
814 | { | |
815 | return check_mnt(real_mount(mnt)); | |
816 | } | |
817 | EXPORT_SYMBOL_GPL(is_current_mnt_ns); | |
818 | ||
819 | /* | |
820 | * vfsmount lock must be held for write | |
821 | */ | |
822 | static void touch_mnt_namespace(struct mnt_namespace *ns) | |
823 | { | |
824 | if (ns) { | |
825 | ns->event = ++event; | |
826 | wake_up_interruptible(&ns->poll); | |
827 | } | |
828 | } | |
829 | ||
830 | /* | |
831 | * vfsmount lock must be held for write | |
832 | */ | |
833 | static void __touch_mnt_namespace(struct mnt_namespace *ns) | |
834 | { | |
835 | if (ns && ns->event != event) { | |
836 | ns->event = event; | |
837 | wake_up_interruptible(&ns->poll); | |
838 | } | |
839 | } | |
840 | ||
841 | /* | |
842 | * vfsmount lock must be held for write | |
843 | */ | |
844 | static struct mountpoint *unhash_mnt(struct mount *mnt) | |
845 | { | |
846 | struct mountpoint *mp; | |
847 | mnt->mnt_parent = mnt; | |
848 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; | |
849 | list_del_init(&mnt->mnt_child); | |
850 | hlist_del_init_rcu(&mnt->mnt_hash); | |
851 | hlist_del_init(&mnt->mnt_mp_list); | |
852 | mp = mnt->mnt_mp; | |
853 | mnt->mnt_mp = NULL; | |
854 | return mp; | |
855 | } | |
856 | ||
857 | /* | |
858 | * vfsmount lock must be held for write | |
859 | */ | |
860 | static void umount_mnt(struct mount *mnt) | |
861 | { | |
862 | put_mountpoint(unhash_mnt(mnt)); | |
863 | } | |
864 | ||
865 | /* | |
866 | * vfsmount lock must be held for write | |
867 | */ | |
868 | void mnt_set_mountpoint(struct mount *mnt, | |
869 | struct mountpoint *mp, | |
870 | struct mount *child_mnt) | |
871 | { | |
872 | mp->m_count++; | |
873 | mnt_add_count(mnt, 1); /* essentially, that's mntget */ | |
874 | child_mnt->mnt_mountpoint = mp->m_dentry; | |
875 | child_mnt->mnt_parent = mnt; | |
876 | child_mnt->mnt_mp = mp; | |
877 | hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list); | |
878 | } | |
879 | ||
880 | static void __attach_mnt(struct mount *mnt, struct mount *parent) | |
881 | { | |
882 | hlist_add_head_rcu(&mnt->mnt_hash, | |
883 | m_hash(&parent->mnt, mnt->mnt_mountpoint)); | |
884 | list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); | |
885 | } | |
886 | ||
887 | /* | |
888 | * vfsmount lock must be held for write | |
889 | */ | |
890 | static void attach_mnt(struct mount *mnt, | |
891 | struct mount *parent, | |
892 | struct mountpoint *mp) | |
893 | { | |
894 | mnt_set_mountpoint(parent, mp, mnt); | |
895 | __attach_mnt(mnt, parent); | |
896 | } | |
897 | ||
898 | void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp, struct mount *mnt) | |
899 | { | |
900 | struct mountpoint *old_mp = mnt->mnt_mp; | |
901 | struct mount *old_parent = mnt->mnt_parent; | |
902 | ||
903 | list_del_init(&mnt->mnt_child); | |
904 | hlist_del_init(&mnt->mnt_mp_list); | |
905 | hlist_del_init_rcu(&mnt->mnt_hash); | |
906 | ||
907 | attach_mnt(mnt, parent, mp); | |
908 | ||
909 | put_mountpoint(old_mp); | |
910 | mnt_add_count(old_parent, -1); | |
911 | } | |
912 | ||
913 | /* | |
914 | * vfsmount lock must be held for write | |
915 | */ | |
916 | static void commit_tree(struct mount *mnt) | |
917 | { | |
918 | struct mount *parent = mnt->mnt_parent; | |
919 | struct mount *m; | |
920 | LIST_HEAD(head); | |
921 | struct mnt_namespace *n = parent->mnt_ns; | |
922 | ||
923 | BUG_ON(parent == mnt); | |
924 | ||
925 | list_add_tail(&head, &mnt->mnt_list); | |
926 | list_for_each_entry(m, &head, mnt_list) | |
927 | m->mnt_ns = n; | |
928 | ||
929 | list_splice(&head, n->list.prev); | |
930 | ||
931 | n->mounts += n->pending_mounts; | |
932 | n->pending_mounts = 0; | |
933 | ||
934 | __attach_mnt(mnt, parent); | |
935 | touch_mnt_namespace(n); | |
936 | } | |
937 | ||
938 | static struct mount *next_mnt(struct mount *p, struct mount *root) | |
939 | { | |
940 | struct list_head *next = p->mnt_mounts.next; | |
941 | if (next == &p->mnt_mounts) { | |
942 | while (1) { | |
943 | if (p == root) | |
944 | return NULL; | |
945 | next = p->mnt_child.next; | |
946 | if (next != &p->mnt_parent->mnt_mounts) | |
947 | break; | |
948 | p = p->mnt_parent; | |
949 | } | |
950 | } | |
951 | return list_entry(next, struct mount, mnt_child); | |
952 | } | |
953 | ||
954 | static struct mount *skip_mnt_tree(struct mount *p) | |
955 | { | |
956 | struct list_head *prev = p->mnt_mounts.prev; | |
957 | while (prev != &p->mnt_mounts) { | |
958 | p = list_entry(prev, struct mount, mnt_child); | |
959 | prev = p->mnt_mounts.prev; | |
960 | } | |
961 | return p; | |
962 | } | |
963 | ||
964 | /** | |
965 | * vfs_create_mount - Create a mount for a configured superblock | |
966 | * @fc: The configuration context with the superblock attached | |
967 | * | |
968 | * Create a mount to an already configured superblock. If necessary, the | |
969 | * caller should invoke vfs_get_tree() before calling this. | |
970 | * | |
971 | * Note that this does not attach the mount to anything. | |
972 | */ | |
973 | struct vfsmount *vfs_create_mount(struct fs_context *fc) | |
974 | { | |
975 | struct mount *mnt; | |
976 | ||
977 | if (!fc->root) | |
978 | return ERR_PTR(-EINVAL); | |
979 | ||
980 | mnt = alloc_vfsmnt(fc->source ?: "none"); | |
981 | if (!mnt) | |
982 | return ERR_PTR(-ENOMEM); | |
983 | ||
984 | if (fc->sb_flags & SB_KERNMOUNT) | |
985 | mnt->mnt.mnt_flags = MNT_INTERNAL; | |
986 | ||
987 | atomic_inc(&fc->root->d_sb->s_active); | |
988 | mnt->mnt.mnt_sb = fc->root->d_sb; | |
989 | mnt->mnt.mnt_root = dget(fc->root); | |
990 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; | |
991 | mnt->mnt_parent = mnt; | |
992 | ||
993 | lock_mount_hash(); | |
994 | list_add_tail(&mnt->mnt_instance, &mnt->mnt.mnt_sb->s_mounts); | |
995 | unlock_mount_hash(); | |
996 | return &mnt->mnt; | |
997 | } | |
998 | EXPORT_SYMBOL(vfs_create_mount); | |
999 | ||
1000 | struct vfsmount *fc_mount(struct fs_context *fc) | |
1001 | { | |
1002 | int err = vfs_get_tree(fc); | |
1003 | if (!err) { | |
1004 | up_write(&fc->root->d_sb->s_umount); | |
1005 | return vfs_create_mount(fc); | |
1006 | } | |
1007 | return ERR_PTR(err); | |
1008 | } | |
1009 | EXPORT_SYMBOL(fc_mount); | |
1010 | ||
1011 | struct vfsmount *vfs_kern_mount(struct file_system_type *type, | |
1012 | int flags, const char *name, | |
1013 | void *data) | |
1014 | { | |
1015 | struct fs_context *fc; | |
1016 | struct vfsmount *mnt; | |
1017 | int ret = 0; | |
1018 | ||
1019 | if (!type) | |
1020 | return ERR_PTR(-EINVAL); | |
1021 | ||
1022 | fc = fs_context_for_mount(type, flags); | |
1023 | if (IS_ERR(fc)) | |
1024 | return ERR_CAST(fc); | |
1025 | ||
1026 | if (name) | |
1027 | ret = vfs_parse_fs_string(fc, "source", | |
1028 | name, strlen(name)); | |
1029 | if (!ret) | |
1030 | ret = parse_monolithic_mount_data(fc, data); | |
1031 | if (!ret) | |
1032 | mnt = fc_mount(fc); | |
1033 | else | |
1034 | mnt = ERR_PTR(ret); | |
1035 | ||
1036 | put_fs_context(fc); | |
1037 | return mnt; | |
1038 | } | |
1039 | EXPORT_SYMBOL_GPL(vfs_kern_mount); | |
1040 | ||
1041 | struct vfsmount * | |
1042 | vfs_submount(const struct dentry *mountpoint, struct file_system_type *type, | |
1043 | const char *name, void *data) | |
1044 | { | |
1045 | /* Until it is worked out how to pass the user namespace | |
1046 | * through from the parent mount to the submount don't support | |
1047 | * unprivileged mounts with submounts. | |
1048 | */ | |
1049 | if (mountpoint->d_sb->s_user_ns != &init_user_ns) | |
1050 | return ERR_PTR(-EPERM); | |
1051 | ||
1052 | return vfs_kern_mount(type, SB_SUBMOUNT, name, data); | |
1053 | } | |
1054 | EXPORT_SYMBOL_GPL(vfs_submount); | |
1055 | ||
1056 | static struct mount *clone_mnt(struct mount *old, struct dentry *root, | |
1057 | int flag) | |
1058 | { | |
1059 | struct super_block *sb = old->mnt.mnt_sb; | |
1060 | struct mount *mnt; | |
1061 | int err; | |
1062 | ||
1063 | mnt = alloc_vfsmnt(old->mnt_devname); | |
1064 | if (!mnt) | |
1065 | return ERR_PTR(-ENOMEM); | |
1066 | ||
1067 | if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE)) | |
1068 | mnt->mnt_group_id = 0; /* not a peer of original */ | |
1069 | else | |
1070 | mnt->mnt_group_id = old->mnt_group_id; | |
1071 | ||
1072 | if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { | |
1073 | err = mnt_alloc_group_id(mnt); | |
1074 | if (err) | |
1075 | goto out_free; | |
1076 | } | |
1077 | ||
1078 | mnt->mnt.mnt_flags = old->mnt.mnt_flags; | |
1079 | mnt->mnt.mnt_flags &= ~(MNT_WRITE_HOLD|MNT_MARKED|MNT_INTERNAL); | |
1080 | ||
1081 | atomic_inc(&sb->s_active); | |
1082 | mnt->mnt.mnt_userns = mnt_user_ns(&old->mnt); | |
1083 | if (mnt->mnt.mnt_userns != &init_user_ns) | |
1084 | mnt->mnt.mnt_userns = get_user_ns(mnt->mnt.mnt_userns); | |
1085 | mnt->mnt.mnt_sb = sb; | |
1086 | mnt->mnt.mnt_root = dget(root); | |
1087 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; | |
1088 | mnt->mnt_parent = mnt; | |
1089 | lock_mount_hash(); | |
1090 | list_add_tail(&mnt->mnt_instance, &sb->s_mounts); | |
1091 | unlock_mount_hash(); | |
1092 | ||
1093 | if ((flag & CL_SLAVE) || | |
1094 | ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) { | |
1095 | list_add(&mnt->mnt_slave, &old->mnt_slave_list); | |
1096 | mnt->mnt_master = old; | |
1097 | CLEAR_MNT_SHARED(mnt); | |
1098 | } else if (!(flag & CL_PRIVATE)) { | |
1099 | if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old)) | |
1100 | list_add(&mnt->mnt_share, &old->mnt_share); | |
1101 | if (IS_MNT_SLAVE(old)) | |
1102 | list_add(&mnt->mnt_slave, &old->mnt_slave); | |
1103 | mnt->mnt_master = old->mnt_master; | |
1104 | } else { | |
1105 | CLEAR_MNT_SHARED(mnt); | |
1106 | } | |
1107 | if (flag & CL_MAKE_SHARED) | |
1108 | set_mnt_shared(mnt); | |
1109 | ||
1110 | /* stick the duplicate mount on the same expiry list | |
1111 | * as the original if that was on one */ | |
1112 | if (flag & CL_EXPIRE) { | |
1113 | if (!list_empty(&old->mnt_expire)) | |
1114 | list_add(&mnt->mnt_expire, &old->mnt_expire); | |
1115 | } | |
1116 | ||
1117 | return mnt; | |
1118 | ||
1119 | out_free: | |
1120 | mnt_free_id(mnt); | |
1121 | free_vfsmnt(mnt); | |
1122 | return ERR_PTR(err); | |
1123 | } | |
1124 | ||
1125 | static void cleanup_mnt(struct mount *mnt) | |
1126 | { | |
1127 | struct hlist_node *p; | |
1128 | struct mount *m; | |
1129 | /* | |
1130 | * The warning here probably indicates that somebody messed | |
1131 | * up a mnt_want/drop_write() pair. If this happens, the | |
1132 | * filesystem was probably unable to make r/w->r/o transitions. | |
1133 | * The locking used to deal with mnt_count decrement provides barriers, | |
1134 | * so mnt_get_writers() below is safe. | |
1135 | */ | |
1136 | WARN_ON(mnt_get_writers(mnt)); | |
1137 | if (unlikely(mnt->mnt_pins.first)) | |
1138 | mnt_pin_kill(mnt); | |
1139 | hlist_for_each_entry_safe(m, p, &mnt->mnt_stuck_children, mnt_umount) { | |
1140 | hlist_del(&m->mnt_umount); | |
1141 | mntput(&m->mnt); | |
1142 | } | |
1143 | fsnotify_vfsmount_delete(&mnt->mnt); | |
1144 | dput(mnt->mnt.mnt_root); | |
1145 | deactivate_super(mnt->mnt.mnt_sb); | |
1146 | mnt_free_id(mnt); | |
1147 | call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt); | |
1148 | } | |
1149 | ||
1150 | static void __cleanup_mnt(struct rcu_head *head) | |
1151 | { | |
1152 | cleanup_mnt(container_of(head, struct mount, mnt_rcu)); | |
1153 | } | |
1154 | ||
1155 | static LLIST_HEAD(delayed_mntput_list); | |
1156 | static void delayed_mntput(struct work_struct *unused) | |
1157 | { | |
1158 | struct llist_node *node = llist_del_all(&delayed_mntput_list); | |
1159 | struct mount *m, *t; | |
1160 | ||
1161 | llist_for_each_entry_safe(m, t, node, mnt_llist) | |
1162 | cleanup_mnt(m); | |
1163 | } | |
1164 | static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput); | |
1165 | ||
1166 | static void mntput_no_expire(struct mount *mnt) | |
1167 | { | |
1168 | LIST_HEAD(list); | |
1169 | int count; | |
1170 | ||
1171 | rcu_read_lock(); | |
1172 | if (likely(READ_ONCE(mnt->mnt_ns))) { | |
1173 | /* | |
1174 | * Since we don't do lock_mount_hash() here, | |
1175 | * ->mnt_ns can change under us. However, if it's | |
1176 | * non-NULL, then there's a reference that won't | |
1177 | * be dropped until after an RCU delay done after | |
1178 | * turning ->mnt_ns NULL. So if we observe it | |
1179 | * non-NULL under rcu_read_lock(), the reference | |
1180 | * we are dropping is not the final one. | |
1181 | */ | |
1182 | mnt_add_count(mnt, -1); | |
1183 | rcu_read_unlock(); | |
1184 | return; | |
1185 | } | |
1186 | lock_mount_hash(); | |
1187 | /* | |
1188 | * make sure that if __legitimize_mnt() has not seen us grab | |
1189 | * mount_lock, we'll see their refcount increment here. | |
1190 | */ | |
1191 | smp_mb(); | |
1192 | mnt_add_count(mnt, -1); | |
1193 | count = mnt_get_count(mnt); | |
1194 | if (count != 0) { | |
1195 | WARN_ON(count < 0); | |
1196 | rcu_read_unlock(); | |
1197 | unlock_mount_hash(); | |
1198 | return; | |
1199 | } | |
1200 | if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) { | |
1201 | rcu_read_unlock(); | |
1202 | unlock_mount_hash(); | |
1203 | return; | |
1204 | } | |
1205 | mnt->mnt.mnt_flags |= MNT_DOOMED; | |
1206 | rcu_read_unlock(); | |
1207 | ||
1208 | list_del(&mnt->mnt_instance); | |
1209 | ||
1210 | if (unlikely(!list_empty(&mnt->mnt_mounts))) { | |
1211 | struct mount *p, *tmp; | |
1212 | list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) { | |
1213 | __put_mountpoint(unhash_mnt(p), &list); | |
1214 | hlist_add_head(&p->mnt_umount, &mnt->mnt_stuck_children); | |
1215 | } | |
1216 | } | |
1217 | unlock_mount_hash(); | |
1218 | shrink_dentry_list(&list); | |
1219 | ||
1220 | if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) { | |
1221 | struct task_struct *task = current; | |
1222 | if (likely(!(task->flags & PF_KTHREAD))) { | |
1223 | init_task_work(&mnt->mnt_rcu, __cleanup_mnt); | |
1224 | if (!task_work_add(task, &mnt->mnt_rcu, TWA_RESUME)) | |
1225 | return; | |
1226 | } | |
1227 | if (llist_add(&mnt->mnt_llist, &delayed_mntput_list)) | |
1228 | schedule_delayed_work(&delayed_mntput_work, 1); | |
1229 | return; | |
1230 | } | |
1231 | cleanup_mnt(mnt); | |
1232 | } | |
1233 | ||
1234 | void mntput(struct vfsmount *mnt) | |
1235 | { | |
1236 | if (mnt) { | |
1237 | struct mount *m = real_mount(mnt); | |
1238 | /* avoid cacheline pingpong, hope gcc doesn't get "smart" */ | |
1239 | if (unlikely(m->mnt_expiry_mark)) | |
1240 | m->mnt_expiry_mark = 0; | |
1241 | mntput_no_expire(m); | |
1242 | } | |
1243 | } | |
1244 | EXPORT_SYMBOL(mntput); | |
1245 | ||
1246 | struct vfsmount *mntget(struct vfsmount *mnt) | |
1247 | { | |
1248 | if (mnt) | |
1249 | mnt_add_count(real_mount(mnt), 1); | |
1250 | return mnt; | |
1251 | } | |
1252 | EXPORT_SYMBOL(mntget); | |
1253 | ||
1254 | /** | |
1255 | * path_is_mountpoint() - Check if path is a mount in the current namespace. | |
1256 | * @path: path to check | |
1257 | * | |
1258 | * d_mountpoint() can only be used reliably to establish if a dentry is | |
1259 | * not mounted in any namespace and that common case is handled inline. | |
1260 | * d_mountpoint() isn't aware of the possibility there may be multiple | |
1261 | * mounts using a given dentry in a different namespace. This function | |
1262 | * checks if the passed in path is a mountpoint rather than the dentry | |
1263 | * alone. | |
1264 | */ | |
1265 | bool path_is_mountpoint(const struct path *path) | |
1266 | { | |
1267 | unsigned seq; | |
1268 | bool res; | |
1269 | ||
1270 | if (!d_mountpoint(path->dentry)) | |
1271 | return false; | |
1272 | ||
1273 | rcu_read_lock(); | |
1274 | do { | |
1275 | seq = read_seqbegin(&mount_lock); | |
1276 | res = __path_is_mountpoint(path); | |
1277 | } while (read_seqretry(&mount_lock, seq)); | |
1278 | rcu_read_unlock(); | |
1279 | ||
1280 | return res; | |
1281 | } | |
1282 | EXPORT_SYMBOL(path_is_mountpoint); | |
1283 | ||
1284 | struct vfsmount *mnt_clone_internal(const struct path *path) | |
1285 | { | |
1286 | struct mount *p; | |
1287 | p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE); | |
1288 | if (IS_ERR(p)) | |
1289 | return ERR_CAST(p); | |
1290 | p->mnt.mnt_flags |= MNT_INTERNAL; | |
1291 | return &p->mnt; | |
1292 | } | |
1293 | ||
1294 | #ifdef CONFIG_PROC_FS | |
1295 | static struct mount *mnt_list_next(struct mnt_namespace *ns, | |
1296 | struct list_head *p) | |
1297 | { | |
1298 | struct mount *mnt, *ret = NULL; | |
1299 | ||
1300 | lock_ns_list(ns); | |
1301 | list_for_each_continue(p, &ns->list) { | |
1302 | mnt = list_entry(p, typeof(*mnt), mnt_list); | |
1303 | if (!mnt_is_cursor(mnt)) { | |
1304 | ret = mnt; | |
1305 | break; | |
1306 | } | |
1307 | } | |
1308 | unlock_ns_list(ns); | |
1309 | ||
1310 | return ret; | |
1311 | } | |
1312 | ||
1313 | /* iterator; we want it to have access to namespace_sem, thus here... */ | |
1314 | static void *m_start(struct seq_file *m, loff_t *pos) | |
1315 | { | |
1316 | struct proc_mounts *p = m->private; | |
1317 | struct list_head *prev; | |
1318 | ||
1319 | down_read(&namespace_sem); | |
1320 | if (!*pos) { | |
1321 | prev = &p->ns->list; | |
1322 | } else { | |
1323 | prev = &p->cursor.mnt_list; | |
1324 | ||
1325 | /* Read after we'd reached the end? */ | |
1326 | if (list_empty(prev)) | |
1327 | return NULL; | |
1328 | } | |
1329 | ||
1330 | return mnt_list_next(p->ns, prev); | |
1331 | } | |
1332 | ||
1333 | static void *m_next(struct seq_file *m, void *v, loff_t *pos) | |
1334 | { | |
1335 | struct proc_mounts *p = m->private; | |
1336 | struct mount *mnt = v; | |
1337 | ||
1338 | ++*pos; | |
1339 | return mnt_list_next(p->ns, &mnt->mnt_list); | |
1340 | } | |
1341 | ||
1342 | static void m_stop(struct seq_file *m, void *v) | |
1343 | { | |
1344 | struct proc_mounts *p = m->private; | |
1345 | struct mount *mnt = v; | |
1346 | ||
1347 | lock_ns_list(p->ns); | |
1348 | if (mnt) | |
1349 | list_move_tail(&p->cursor.mnt_list, &mnt->mnt_list); | |
1350 | else | |
1351 | list_del_init(&p->cursor.mnt_list); | |
1352 | unlock_ns_list(p->ns); | |
1353 | up_read(&namespace_sem); | |
1354 | } | |
1355 | ||
1356 | static int m_show(struct seq_file *m, void *v) | |
1357 | { | |
1358 | struct proc_mounts *p = m->private; | |
1359 | struct mount *r = v; | |
1360 | return p->show(m, &r->mnt); | |
1361 | } | |
1362 | ||
1363 | const struct seq_operations mounts_op = { | |
1364 | .start = m_start, | |
1365 | .next = m_next, | |
1366 | .stop = m_stop, | |
1367 | .show = m_show, | |
1368 | }; | |
1369 | ||
1370 | void mnt_cursor_del(struct mnt_namespace *ns, struct mount *cursor) | |
1371 | { | |
1372 | down_read(&namespace_sem); | |
1373 | lock_ns_list(ns); | |
1374 | list_del(&cursor->mnt_list); | |
1375 | unlock_ns_list(ns); | |
1376 | up_read(&namespace_sem); | |
1377 | } | |
1378 | #endif /* CONFIG_PROC_FS */ | |
1379 | ||
1380 | /** | |
1381 | * may_umount_tree - check if a mount tree is busy | |
1382 | * @m: root of mount tree | |
1383 | * | |
1384 | * This is called to check if a tree of mounts has any | |
1385 | * open files, pwds, chroots or sub mounts that are | |
1386 | * busy. | |
1387 | */ | |
1388 | int may_umount_tree(struct vfsmount *m) | |
1389 | { | |
1390 | struct mount *mnt = real_mount(m); | |
1391 | int actual_refs = 0; | |
1392 | int minimum_refs = 0; | |
1393 | struct mount *p; | |
1394 | BUG_ON(!m); | |
1395 | ||
1396 | /* write lock needed for mnt_get_count */ | |
1397 | lock_mount_hash(); | |
1398 | for (p = mnt; p; p = next_mnt(p, mnt)) { | |
1399 | actual_refs += mnt_get_count(p); | |
1400 | minimum_refs += 2; | |
1401 | } | |
1402 | unlock_mount_hash(); | |
1403 | ||
1404 | if (actual_refs > minimum_refs) | |
1405 | return 0; | |
1406 | ||
1407 | return 1; | |
1408 | } | |
1409 | ||
1410 | EXPORT_SYMBOL(may_umount_tree); | |
1411 | ||
1412 | /** | |
1413 | * may_umount - check if a mount point is busy | |
1414 | * @mnt: root of mount | |
1415 | * | |
1416 | * This is called to check if a mount point has any | |
1417 | * open files, pwds, chroots or sub mounts. If the | |
1418 | * mount has sub mounts this will return busy | |
1419 | * regardless of whether the sub mounts are busy. | |
1420 | * | |
1421 | * Doesn't take quota and stuff into account. IOW, in some cases it will | |
1422 | * give false negatives. The main reason why it's here is that we need | |
1423 | * a non-destructive way to look for easily umountable filesystems. | |
1424 | */ | |
1425 | int may_umount(struct vfsmount *mnt) | |
1426 | { | |
1427 | int ret = 1; | |
1428 | down_read(&namespace_sem); | |
1429 | lock_mount_hash(); | |
1430 | if (propagate_mount_busy(real_mount(mnt), 2)) | |
1431 | ret = 0; | |
1432 | unlock_mount_hash(); | |
1433 | up_read(&namespace_sem); | |
1434 | return ret; | |
1435 | } | |
1436 | ||
1437 | EXPORT_SYMBOL(may_umount); | |
1438 | ||
1439 | static void namespace_unlock(void) | |
1440 | { | |
1441 | struct hlist_head head; | |
1442 | struct hlist_node *p; | |
1443 | struct mount *m; | |
1444 | LIST_HEAD(list); | |
1445 | ||
1446 | hlist_move_list(&unmounted, &head); | |
1447 | list_splice_init(&ex_mountpoints, &list); | |
1448 | ||
1449 | up_write(&namespace_sem); | |
1450 | ||
1451 | shrink_dentry_list(&list); | |
1452 | ||
1453 | if (likely(hlist_empty(&head))) | |
1454 | return; | |
1455 | ||
1456 | synchronize_rcu_expedited(); | |
1457 | ||
1458 | hlist_for_each_entry_safe(m, p, &head, mnt_umount) { | |
1459 | hlist_del(&m->mnt_umount); | |
1460 | mntput(&m->mnt); | |
1461 | } | |
1462 | } | |
1463 | ||
1464 | static inline void namespace_lock(void) | |
1465 | { | |
1466 | down_write(&namespace_sem); | |
1467 | } | |
1468 | ||
1469 | enum umount_tree_flags { | |
1470 | UMOUNT_SYNC = 1, | |
1471 | UMOUNT_PROPAGATE = 2, | |
1472 | UMOUNT_CONNECTED = 4, | |
1473 | }; | |
1474 | ||
1475 | static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how) | |
1476 | { | |
1477 | /* Leaving mounts connected is only valid for lazy umounts */ | |
1478 | if (how & UMOUNT_SYNC) | |
1479 | return true; | |
1480 | ||
1481 | /* A mount without a parent has nothing to be connected to */ | |
1482 | if (!mnt_has_parent(mnt)) | |
1483 | return true; | |
1484 | ||
1485 | /* Because the reference counting rules change when mounts are | |
1486 | * unmounted and connected, umounted mounts may not be | |
1487 | * connected to mounted mounts. | |
1488 | */ | |
1489 | if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT)) | |
1490 | return true; | |
1491 | ||
1492 | /* Has it been requested that the mount remain connected? */ | |
1493 | if (how & UMOUNT_CONNECTED) | |
1494 | return false; | |
1495 | ||
1496 | /* Is the mount locked such that it needs to remain connected? */ | |
1497 | if (IS_MNT_LOCKED(mnt)) | |
1498 | return false; | |
1499 | ||
1500 | /* By default disconnect the mount */ | |
1501 | return true; | |
1502 | } | |
1503 | ||
1504 | /* | |
1505 | * mount_lock must be held | |
1506 | * namespace_sem must be held for write | |
1507 | */ | |
1508 | static void umount_tree(struct mount *mnt, enum umount_tree_flags how) | |
1509 | { | |
1510 | LIST_HEAD(tmp_list); | |
1511 | struct mount *p; | |
1512 | ||
1513 | if (how & UMOUNT_PROPAGATE) | |
1514 | propagate_mount_unlock(mnt); | |
1515 | ||
1516 | /* Gather the mounts to umount */ | |
1517 | for (p = mnt; p; p = next_mnt(p, mnt)) { | |
1518 | p->mnt.mnt_flags |= MNT_UMOUNT; | |
1519 | list_move(&p->mnt_list, &tmp_list); | |
1520 | } | |
1521 | ||
1522 | /* Hide the mounts from mnt_mounts */ | |
1523 | list_for_each_entry(p, &tmp_list, mnt_list) { | |
1524 | list_del_init(&p->mnt_child); | |
1525 | } | |
1526 | ||
1527 | /* Add propogated mounts to the tmp_list */ | |
1528 | if (how & UMOUNT_PROPAGATE) | |
1529 | propagate_umount(&tmp_list); | |
1530 | ||
1531 | while (!list_empty(&tmp_list)) { | |
1532 | struct mnt_namespace *ns; | |
1533 | bool disconnect; | |
1534 | p = list_first_entry(&tmp_list, struct mount, mnt_list); | |
1535 | list_del_init(&p->mnt_expire); | |
1536 | list_del_init(&p->mnt_list); | |
1537 | ns = p->mnt_ns; | |
1538 | if (ns) { | |
1539 | ns->mounts--; | |
1540 | __touch_mnt_namespace(ns); | |
1541 | } | |
1542 | p->mnt_ns = NULL; | |
1543 | if (how & UMOUNT_SYNC) | |
1544 | p->mnt.mnt_flags |= MNT_SYNC_UMOUNT; | |
1545 | ||
1546 | disconnect = disconnect_mount(p, how); | |
1547 | if (mnt_has_parent(p)) { | |
1548 | mnt_add_count(p->mnt_parent, -1); | |
1549 | if (!disconnect) { | |
1550 | /* Don't forget about p */ | |
1551 | list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts); | |
1552 | } else { | |
1553 | umount_mnt(p); | |
1554 | } | |
1555 | } | |
1556 | change_mnt_propagation(p, MS_PRIVATE); | |
1557 | if (disconnect) | |
1558 | hlist_add_head(&p->mnt_umount, &unmounted); | |
1559 | } | |
1560 | } | |
1561 | ||
1562 | static void shrink_submounts(struct mount *mnt); | |
1563 | ||
1564 | static int do_umount_root(struct super_block *sb) | |
1565 | { | |
1566 | int ret = 0; | |
1567 | ||
1568 | down_write(&sb->s_umount); | |
1569 | if (!sb_rdonly(sb)) { | |
1570 | struct fs_context *fc; | |
1571 | ||
1572 | fc = fs_context_for_reconfigure(sb->s_root, SB_RDONLY, | |
1573 | SB_RDONLY); | |
1574 | if (IS_ERR(fc)) { | |
1575 | ret = PTR_ERR(fc); | |
1576 | } else { | |
1577 | ret = parse_monolithic_mount_data(fc, NULL); | |
1578 | if (!ret) | |
1579 | ret = reconfigure_super(fc); | |
1580 | put_fs_context(fc); | |
1581 | } | |
1582 | } | |
1583 | up_write(&sb->s_umount); | |
1584 | return ret; | |
1585 | } | |
1586 | ||
1587 | static int do_umount(struct mount *mnt, int flags) | |
1588 | { | |
1589 | struct super_block *sb = mnt->mnt.mnt_sb; | |
1590 | int retval; | |
1591 | ||
1592 | retval = security_sb_umount(&mnt->mnt, flags); | |
1593 | if (retval) | |
1594 | return retval; | |
1595 | ||
1596 | /* | |
1597 | * Allow userspace to request a mountpoint be expired rather than | |
1598 | * unmounting unconditionally. Unmount only happens if: | |
1599 | * (1) the mark is already set (the mark is cleared by mntput()) | |
1600 | * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] | |
1601 | */ | |
1602 | if (flags & MNT_EXPIRE) { | |
1603 | if (&mnt->mnt == current->fs->root.mnt || | |
1604 | flags & (MNT_FORCE | MNT_DETACH)) | |
1605 | return -EINVAL; | |
1606 | ||
1607 | /* | |
1608 | * probably don't strictly need the lock here if we examined | |
1609 | * all race cases, but it's a slowpath. | |
1610 | */ | |
1611 | lock_mount_hash(); | |
1612 | if (mnt_get_count(mnt) != 2) { | |
1613 | unlock_mount_hash(); | |
1614 | return -EBUSY; | |
1615 | } | |
1616 | unlock_mount_hash(); | |
1617 | ||
1618 | if (!xchg(&mnt->mnt_expiry_mark, 1)) | |
1619 | return -EAGAIN; | |
1620 | } | |
1621 | ||
1622 | /* | |
1623 | * If we may have to abort operations to get out of this | |
1624 | * mount, and they will themselves hold resources we must | |
1625 | * allow the fs to do things. In the Unix tradition of | |
1626 | * 'Gee thats tricky lets do it in userspace' the umount_begin | |
1627 | * might fail to complete on the first run through as other tasks | |
1628 | * must return, and the like. Thats for the mount program to worry | |
1629 | * about for the moment. | |
1630 | */ | |
1631 | ||
1632 | if (flags & MNT_FORCE && sb->s_op->umount_begin) { | |
1633 | sb->s_op->umount_begin(sb); | |
1634 | } | |
1635 | ||
1636 | /* | |
1637 | * No sense to grab the lock for this test, but test itself looks | |
1638 | * somewhat bogus. Suggestions for better replacement? | |
1639 | * Ho-hum... In principle, we might treat that as umount + switch | |
1640 | * to rootfs. GC would eventually take care of the old vfsmount. | |
1641 | * Actually it makes sense, especially if rootfs would contain a | |
1642 | * /reboot - static binary that would close all descriptors and | |
1643 | * call reboot(9). Then init(8) could umount root and exec /reboot. | |
1644 | */ | |
1645 | if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { | |
1646 | /* | |
1647 | * Special case for "unmounting" root ... | |
1648 | * we just try to remount it readonly. | |
1649 | */ | |
1650 | if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) | |
1651 | return -EPERM; | |
1652 | return do_umount_root(sb); | |
1653 | } | |
1654 | ||
1655 | namespace_lock(); | |
1656 | lock_mount_hash(); | |
1657 | ||
1658 | /* Recheck MNT_LOCKED with the locks held */ | |
1659 | retval = -EINVAL; | |
1660 | if (mnt->mnt.mnt_flags & MNT_LOCKED) | |
1661 | goto out; | |
1662 | ||
1663 | event++; | |
1664 | if (flags & MNT_DETACH) { | |
1665 | if (!list_empty(&mnt->mnt_list)) | |
1666 | umount_tree(mnt, UMOUNT_PROPAGATE); | |
1667 | retval = 0; | |
1668 | } else { | |
1669 | shrink_submounts(mnt); | |
1670 | retval = -EBUSY; | |
1671 | if (!propagate_mount_busy(mnt, 2)) { | |
1672 | if (!list_empty(&mnt->mnt_list)) | |
1673 | umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC); | |
1674 | retval = 0; | |
1675 | } | |
1676 | } | |
1677 | out: | |
1678 | unlock_mount_hash(); | |
1679 | namespace_unlock(); | |
1680 | return retval; | |
1681 | } | |
1682 | ||
1683 | /* | |
1684 | * __detach_mounts - lazily unmount all mounts on the specified dentry | |
1685 | * | |
1686 | * During unlink, rmdir, and d_drop it is possible to loose the path | |
1687 | * to an existing mountpoint, and wind up leaking the mount. | |
1688 | * detach_mounts allows lazily unmounting those mounts instead of | |
1689 | * leaking them. | |
1690 | * | |
1691 | * The caller may hold dentry->d_inode->i_mutex. | |
1692 | */ | |
1693 | void __detach_mounts(struct dentry *dentry) | |
1694 | { | |
1695 | struct mountpoint *mp; | |
1696 | struct mount *mnt; | |
1697 | ||
1698 | namespace_lock(); | |
1699 | lock_mount_hash(); | |
1700 | mp = lookup_mountpoint(dentry); | |
1701 | if (!mp) | |
1702 | goto out_unlock; | |
1703 | ||
1704 | event++; | |
1705 | while (!hlist_empty(&mp->m_list)) { | |
1706 | mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list); | |
1707 | if (mnt->mnt.mnt_flags & MNT_UMOUNT) { | |
1708 | umount_mnt(mnt); | |
1709 | hlist_add_head(&mnt->mnt_umount, &unmounted); | |
1710 | } | |
1711 | else umount_tree(mnt, UMOUNT_CONNECTED); | |
1712 | } | |
1713 | put_mountpoint(mp); | |
1714 | out_unlock: | |
1715 | unlock_mount_hash(); | |
1716 | namespace_unlock(); | |
1717 | } | |
1718 | ||
1719 | /* | |
1720 | * Is the caller allowed to modify his namespace? | |
1721 | */ | |
1722 | static inline bool may_mount(void) | |
1723 | { | |
1724 | return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN); | |
1725 | } | |
1726 | ||
1727 | static void warn_mandlock(void) | |
1728 | { | |
1729 | pr_warn_once("=======================================================\n" | |
1730 | "WARNING: The mand mount option has been deprecated and\n" | |
1731 | " and is ignored by this kernel. Remove the mand\n" | |
1732 | " option from the mount to silence this warning.\n" | |
1733 | "=======================================================\n"); | |
1734 | } | |
1735 | ||
1736 | static int can_umount(const struct path *path, int flags) | |
1737 | { | |
1738 | struct mount *mnt = real_mount(path->mnt); | |
1739 | ||
1740 | if (!may_mount()) | |
1741 | return -EPERM; | |
1742 | if (path->dentry != path->mnt->mnt_root) | |
1743 | return -EINVAL; | |
1744 | if (!check_mnt(mnt)) | |
1745 | return -EINVAL; | |
1746 | if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */ | |
1747 | return -EINVAL; | |
1748 | if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN)) | |
1749 | return -EPERM; | |
1750 | return 0; | |
1751 | } | |
1752 | ||
1753 | // caller is responsible for flags being sane | |
1754 | int path_umount(struct path *path, int flags) | |
1755 | { | |
1756 | struct mount *mnt = real_mount(path->mnt); | |
1757 | int ret; | |
1758 | ||
1759 | ret = can_umount(path, flags); | |
1760 | if (!ret) | |
1761 | ret = do_umount(mnt, flags); | |
1762 | ||
1763 | /* we mustn't call path_put() as that would clear mnt_expiry_mark */ | |
1764 | dput(path->dentry); | |
1765 | mntput_no_expire(mnt); | |
1766 | return ret; | |
1767 | } | |
1768 | ||
1769 | static int ksys_umount(char __user *name, int flags) | |
1770 | { | |
1771 | int lookup_flags = LOOKUP_MOUNTPOINT; | |
1772 | struct path path; | |
1773 | int ret; | |
1774 | ||
1775 | // basic validity checks done first | |
1776 | if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) | |
1777 | return -EINVAL; | |
1778 | ||
1779 | if (!(flags & UMOUNT_NOFOLLOW)) | |
1780 | lookup_flags |= LOOKUP_FOLLOW; | |
1781 | ret = user_path_at(AT_FDCWD, name, lookup_flags, &path); | |
1782 | if (ret) | |
1783 | return ret; | |
1784 | return path_umount(&path, flags); | |
1785 | } | |
1786 | ||
1787 | SYSCALL_DEFINE2(umount, char __user *, name, int, flags) | |
1788 | { | |
1789 | return ksys_umount(name, flags); | |
1790 | } | |
1791 | ||
1792 | #ifdef __ARCH_WANT_SYS_OLDUMOUNT | |
1793 | ||
1794 | /* | |
1795 | * The 2.0 compatible umount. No flags. | |
1796 | */ | |
1797 | SYSCALL_DEFINE1(oldumount, char __user *, name) | |
1798 | { | |
1799 | return ksys_umount(name, 0); | |
1800 | } | |
1801 | ||
1802 | #endif | |
1803 | ||
1804 | static bool is_mnt_ns_file(struct dentry *dentry) | |
1805 | { | |
1806 | /* Is this a proxy for a mount namespace? */ | |
1807 | return dentry->d_op == &ns_dentry_operations && | |
1808 | dentry->d_fsdata == &mntns_operations; | |
1809 | } | |
1810 | ||
1811 | static struct mnt_namespace *to_mnt_ns(struct ns_common *ns) | |
1812 | { | |
1813 | return container_of(ns, struct mnt_namespace, ns); | |
1814 | } | |
1815 | ||
1816 | struct ns_common *from_mnt_ns(struct mnt_namespace *mnt) | |
1817 | { | |
1818 | return &mnt->ns; | |
1819 | } | |
1820 | ||
1821 | static bool mnt_ns_loop(struct dentry *dentry) | |
1822 | { | |
1823 | /* Could bind mounting the mount namespace inode cause a | |
1824 | * mount namespace loop? | |
1825 | */ | |
1826 | struct mnt_namespace *mnt_ns; | |
1827 | if (!is_mnt_ns_file(dentry)) | |
1828 | return false; | |
1829 | ||
1830 | mnt_ns = to_mnt_ns(get_proc_ns(dentry->d_inode)); | |
1831 | return current->nsproxy->mnt_ns->seq >= mnt_ns->seq; | |
1832 | } | |
1833 | ||
1834 | struct mount *copy_tree(struct mount *mnt, struct dentry *dentry, | |
1835 | int flag) | |
1836 | { | |
1837 | struct mount *res, *p, *q, *r, *parent; | |
1838 | ||
1839 | if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt)) | |
1840 | return ERR_PTR(-EINVAL); | |
1841 | ||
1842 | if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry)) | |
1843 | return ERR_PTR(-EINVAL); | |
1844 | ||
1845 | res = q = clone_mnt(mnt, dentry, flag); | |
1846 | if (IS_ERR(q)) | |
1847 | return q; | |
1848 | ||
1849 | q->mnt_mountpoint = mnt->mnt_mountpoint; | |
1850 | ||
1851 | p = mnt; | |
1852 | list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { | |
1853 | struct mount *s; | |
1854 | if (!is_subdir(r->mnt_mountpoint, dentry)) | |
1855 | continue; | |
1856 | ||
1857 | for (s = r; s; s = next_mnt(s, r)) { | |
1858 | if (!(flag & CL_COPY_UNBINDABLE) && | |
1859 | IS_MNT_UNBINDABLE(s)) { | |
1860 | if (s->mnt.mnt_flags & MNT_LOCKED) { | |
1861 | /* Both unbindable and locked. */ | |
1862 | q = ERR_PTR(-EPERM); | |
1863 | goto out; | |
1864 | } else { | |
1865 | s = skip_mnt_tree(s); | |
1866 | continue; | |
1867 | } | |
1868 | } | |
1869 | if (!(flag & CL_COPY_MNT_NS_FILE) && | |
1870 | is_mnt_ns_file(s->mnt.mnt_root)) { | |
1871 | s = skip_mnt_tree(s); | |
1872 | continue; | |
1873 | } | |
1874 | while (p != s->mnt_parent) { | |
1875 | p = p->mnt_parent; | |
1876 | q = q->mnt_parent; | |
1877 | } | |
1878 | p = s; | |
1879 | parent = q; | |
1880 | q = clone_mnt(p, p->mnt.mnt_root, flag); | |
1881 | if (IS_ERR(q)) | |
1882 | goto out; | |
1883 | lock_mount_hash(); | |
1884 | list_add_tail(&q->mnt_list, &res->mnt_list); | |
1885 | attach_mnt(q, parent, p->mnt_mp); | |
1886 | unlock_mount_hash(); | |
1887 | } | |
1888 | } | |
1889 | return res; | |
1890 | out: | |
1891 | if (res) { | |
1892 | lock_mount_hash(); | |
1893 | umount_tree(res, UMOUNT_SYNC); | |
1894 | unlock_mount_hash(); | |
1895 | } | |
1896 | return q; | |
1897 | } | |
1898 | ||
1899 | /* Caller should check returned pointer for errors */ | |
1900 | ||
1901 | struct vfsmount *collect_mounts(const struct path *path) | |
1902 | { | |
1903 | struct mount *tree; | |
1904 | namespace_lock(); | |
1905 | if (!check_mnt(real_mount(path->mnt))) | |
1906 | tree = ERR_PTR(-EINVAL); | |
1907 | else | |
1908 | tree = copy_tree(real_mount(path->mnt), path->dentry, | |
1909 | CL_COPY_ALL | CL_PRIVATE); | |
1910 | namespace_unlock(); | |
1911 | if (IS_ERR(tree)) | |
1912 | return ERR_CAST(tree); | |
1913 | return &tree->mnt; | |
1914 | } | |
1915 | ||
1916 | static void free_mnt_ns(struct mnt_namespace *); | |
1917 | static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *, bool); | |
1918 | ||
1919 | void dissolve_on_fput(struct vfsmount *mnt) | |
1920 | { | |
1921 | struct mnt_namespace *ns; | |
1922 | namespace_lock(); | |
1923 | lock_mount_hash(); | |
1924 | ns = real_mount(mnt)->mnt_ns; | |
1925 | if (ns) { | |
1926 | if (is_anon_ns(ns)) | |
1927 | umount_tree(real_mount(mnt), UMOUNT_CONNECTED); | |
1928 | else | |
1929 | ns = NULL; | |
1930 | } | |
1931 | unlock_mount_hash(); | |
1932 | namespace_unlock(); | |
1933 | if (ns) | |
1934 | free_mnt_ns(ns); | |
1935 | } | |
1936 | ||
1937 | void drop_collected_mounts(struct vfsmount *mnt) | |
1938 | { | |
1939 | namespace_lock(); | |
1940 | lock_mount_hash(); | |
1941 | umount_tree(real_mount(mnt), 0); | |
1942 | unlock_mount_hash(); | |
1943 | namespace_unlock(); | |
1944 | } | |
1945 | ||
1946 | static bool has_locked_children(struct mount *mnt, struct dentry *dentry) | |
1947 | { | |
1948 | struct mount *child; | |
1949 | ||
1950 | list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { | |
1951 | if (!is_subdir(child->mnt_mountpoint, dentry)) | |
1952 | continue; | |
1953 | ||
1954 | if (child->mnt.mnt_flags & MNT_LOCKED) | |
1955 | return true; | |
1956 | } | |
1957 | return false; | |
1958 | } | |
1959 | ||
1960 | /** | |
1961 | * clone_private_mount - create a private clone of a path | |
1962 | * @path: path to clone | |
1963 | * | |
1964 | * This creates a new vfsmount, which will be the clone of @path. The new mount | |
1965 | * will not be attached anywhere in the namespace and will be private (i.e. | |
1966 | * changes to the originating mount won't be propagated into this). | |
1967 | * | |
1968 | * Release with mntput(). | |
1969 | */ | |
1970 | struct vfsmount *clone_private_mount(const struct path *path) | |
1971 | { | |
1972 | struct mount *old_mnt = real_mount(path->mnt); | |
1973 | struct mount *new_mnt; | |
1974 | ||
1975 | down_read(&namespace_sem); | |
1976 | if (IS_MNT_UNBINDABLE(old_mnt)) | |
1977 | goto invalid; | |
1978 | ||
1979 | if (!check_mnt(old_mnt)) | |
1980 | goto invalid; | |
1981 | ||
1982 | if (has_locked_children(old_mnt, path->dentry)) | |
1983 | goto invalid; | |
1984 | ||
1985 | new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE); | |
1986 | up_read(&namespace_sem); | |
1987 | ||
1988 | if (IS_ERR(new_mnt)) | |
1989 | return ERR_CAST(new_mnt); | |
1990 | ||
1991 | /* Longterm mount to be removed by kern_unmount*() */ | |
1992 | new_mnt->mnt_ns = MNT_NS_INTERNAL; | |
1993 | ||
1994 | return &new_mnt->mnt; | |
1995 | ||
1996 | invalid: | |
1997 | up_read(&namespace_sem); | |
1998 | return ERR_PTR(-EINVAL); | |
1999 | } | |
2000 | EXPORT_SYMBOL_GPL(clone_private_mount); | |
2001 | ||
2002 | int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, | |
2003 | struct vfsmount *root) | |
2004 | { | |
2005 | struct mount *mnt; | |
2006 | int res = f(root, arg); | |
2007 | if (res) | |
2008 | return res; | |
2009 | list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) { | |
2010 | res = f(&mnt->mnt, arg); | |
2011 | if (res) | |
2012 | return res; | |
2013 | } | |
2014 | return 0; | |
2015 | } | |
2016 | EXPORT_SYMBOL_GPL(iterate_mounts); | |
2017 | ||
2018 | static void lock_mnt_tree(struct mount *mnt) | |
2019 | { | |
2020 | struct mount *p; | |
2021 | ||
2022 | for (p = mnt; p; p = next_mnt(p, mnt)) { | |
2023 | int flags = p->mnt.mnt_flags; | |
2024 | /* Don't allow unprivileged users to change mount flags */ | |
2025 | flags |= MNT_LOCK_ATIME; | |
2026 | ||
2027 | if (flags & MNT_READONLY) | |
2028 | flags |= MNT_LOCK_READONLY; | |
2029 | ||
2030 | if (flags & MNT_NODEV) | |
2031 | flags |= MNT_LOCK_NODEV; | |
2032 | ||
2033 | if (flags & MNT_NOSUID) | |
2034 | flags |= MNT_LOCK_NOSUID; | |
2035 | ||
2036 | if (flags & MNT_NOEXEC) | |
2037 | flags |= MNT_LOCK_NOEXEC; | |
2038 | /* Don't allow unprivileged users to reveal what is under a mount */ | |
2039 | if (list_empty(&p->mnt_expire)) | |
2040 | flags |= MNT_LOCKED; | |
2041 | p->mnt.mnt_flags = flags; | |
2042 | } | |
2043 | } | |
2044 | ||
2045 | static void cleanup_group_ids(struct mount *mnt, struct mount *end) | |
2046 | { | |
2047 | struct mount *p; | |
2048 | ||
2049 | for (p = mnt; p != end; p = next_mnt(p, mnt)) { | |
2050 | if (p->mnt_group_id && !IS_MNT_SHARED(p)) | |
2051 | mnt_release_group_id(p); | |
2052 | } | |
2053 | } | |
2054 | ||
2055 | static int invent_group_ids(struct mount *mnt, bool recurse) | |
2056 | { | |
2057 | struct mount *p; | |
2058 | ||
2059 | for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { | |
2060 | if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { | |
2061 | int err = mnt_alloc_group_id(p); | |
2062 | if (err) { | |
2063 | cleanup_group_ids(mnt, p); | |
2064 | return err; | |
2065 | } | |
2066 | } | |
2067 | } | |
2068 | ||
2069 | return 0; | |
2070 | } | |
2071 | ||
2072 | int count_mounts(struct mnt_namespace *ns, struct mount *mnt) | |
2073 | { | |
2074 | unsigned int max = READ_ONCE(sysctl_mount_max); | |
2075 | unsigned int mounts = 0, old, pending, sum; | |
2076 | struct mount *p; | |
2077 | ||
2078 | for (p = mnt; p; p = next_mnt(p, mnt)) | |
2079 | mounts++; | |
2080 | ||
2081 | old = ns->mounts; | |
2082 | pending = ns->pending_mounts; | |
2083 | sum = old + pending; | |
2084 | if ((old > sum) || | |
2085 | (pending > sum) || | |
2086 | (max < sum) || | |
2087 | (mounts > (max - sum))) | |
2088 | return -ENOSPC; | |
2089 | ||
2090 | ns->pending_mounts = pending + mounts; | |
2091 | return 0; | |
2092 | } | |
2093 | ||
2094 | /* | |
2095 | * @source_mnt : mount tree to be attached | |
2096 | * @nd : place the mount tree @source_mnt is attached | |
2097 | * @parent_nd : if non-null, detach the source_mnt from its parent and | |
2098 | * store the parent mount and mountpoint dentry. | |
2099 | * (done when source_mnt is moved) | |
2100 | * | |
2101 | * NOTE: in the table below explains the semantics when a source mount | |
2102 | * of a given type is attached to a destination mount of a given type. | |
2103 | * --------------------------------------------------------------------------- | |
2104 | * | BIND MOUNT OPERATION | | |
2105 | * |************************************************************************** | |
2106 | * | source-->| shared | private | slave | unbindable | | |
2107 | * | dest | | | | | | |
2108 | * | | | | | | | | |
2109 | * | v | | | | | | |
2110 | * |************************************************************************** | |
2111 | * | shared | shared (++) | shared (+) | shared(+++)| invalid | | |
2112 | * | | | | | | | |
2113 | * |non-shared| shared (+) | private | slave (*) | invalid | | |
2114 | * *************************************************************************** | |
2115 | * A bind operation clones the source mount and mounts the clone on the | |
2116 | * destination mount. | |
2117 | * | |
2118 | * (++) the cloned mount is propagated to all the mounts in the propagation | |
2119 | * tree of the destination mount and the cloned mount is added to | |
2120 | * the peer group of the source mount. | |
2121 | * (+) the cloned mount is created under the destination mount and is marked | |
2122 | * as shared. The cloned mount is added to the peer group of the source | |
2123 | * mount. | |
2124 | * (+++) the mount is propagated to all the mounts in the propagation tree | |
2125 | * of the destination mount and the cloned mount is made slave | |
2126 | * of the same master as that of the source mount. The cloned mount | |
2127 | * is marked as 'shared and slave'. | |
2128 | * (*) the cloned mount is made a slave of the same master as that of the | |
2129 | * source mount. | |
2130 | * | |
2131 | * --------------------------------------------------------------------------- | |
2132 | * | MOVE MOUNT OPERATION | | |
2133 | * |************************************************************************** | |
2134 | * | source-->| shared | private | slave | unbindable | | |
2135 | * | dest | | | | | | |
2136 | * | | | | | | | | |
2137 | * | v | | | | | | |
2138 | * |************************************************************************** | |
2139 | * | shared | shared (+) | shared (+) | shared(+++) | invalid | | |
2140 | * | | | | | | | |
2141 | * |non-shared| shared (+*) | private | slave (*) | unbindable | | |
2142 | * *************************************************************************** | |
2143 | * | |
2144 | * (+) the mount is moved to the destination. And is then propagated to | |
2145 | * all the mounts in the propagation tree of the destination mount. | |
2146 | * (+*) the mount is moved to the destination. | |
2147 | * (+++) the mount is moved to the destination and is then propagated to | |
2148 | * all the mounts belonging to the destination mount's propagation tree. | |
2149 | * the mount is marked as 'shared and slave'. | |
2150 | * (*) the mount continues to be a slave at the new location. | |
2151 | * | |
2152 | * if the source mount is a tree, the operations explained above is | |
2153 | * applied to each mount in the tree. | |
2154 | * Must be called without spinlocks held, since this function can sleep | |
2155 | * in allocations. | |
2156 | */ | |
2157 | static int attach_recursive_mnt(struct mount *source_mnt, | |
2158 | struct mount *dest_mnt, | |
2159 | struct mountpoint *dest_mp, | |
2160 | bool moving) | |
2161 | { | |
2162 | struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; | |
2163 | HLIST_HEAD(tree_list); | |
2164 | struct mnt_namespace *ns = dest_mnt->mnt_ns; | |
2165 | struct mountpoint *smp; | |
2166 | struct mount *child, *p; | |
2167 | struct hlist_node *n; | |
2168 | int err; | |
2169 | ||
2170 | /* Preallocate a mountpoint in case the new mounts need | |
2171 | * to be tucked under other mounts. | |
2172 | */ | |
2173 | smp = get_mountpoint(source_mnt->mnt.mnt_root); | |
2174 | if (IS_ERR(smp)) | |
2175 | return PTR_ERR(smp); | |
2176 | ||
2177 | /* Is there space to add these mounts to the mount namespace? */ | |
2178 | if (!moving) { | |
2179 | err = count_mounts(ns, source_mnt); | |
2180 | if (err) | |
2181 | goto out; | |
2182 | } | |
2183 | ||
2184 | if (IS_MNT_SHARED(dest_mnt)) { | |
2185 | err = invent_group_ids(source_mnt, true); | |
2186 | if (err) | |
2187 | goto out; | |
2188 | err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list); | |
2189 | lock_mount_hash(); | |
2190 | if (err) | |
2191 | goto out_cleanup_ids; | |
2192 | for (p = source_mnt; p; p = next_mnt(p, source_mnt)) | |
2193 | set_mnt_shared(p); | |
2194 | } else { | |
2195 | lock_mount_hash(); | |
2196 | } | |
2197 | if (moving) { | |
2198 | unhash_mnt(source_mnt); | |
2199 | attach_mnt(source_mnt, dest_mnt, dest_mp); | |
2200 | touch_mnt_namespace(source_mnt->mnt_ns); | |
2201 | } else { | |
2202 | if (source_mnt->mnt_ns) { | |
2203 | /* move from anon - the caller will destroy */ | |
2204 | list_del_init(&source_mnt->mnt_ns->list); | |
2205 | } | |
2206 | mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt); | |
2207 | commit_tree(source_mnt); | |
2208 | } | |
2209 | ||
2210 | hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) { | |
2211 | struct mount *q; | |
2212 | hlist_del_init(&child->mnt_hash); | |
2213 | q = __lookup_mnt(&child->mnt_parent->mnt, | |
2214 | child->mnt_mountpoint); | |
2215 | if (q) | |
2216 | mnt_change_mountpoint(child, smp, q); | |
2217 | /* Notice when we are propagating across user namespaces */ | |
2218 | if (child->mnt_parent->mnt_ns->user_ns != user_ns) | |
2219 | lock_mnt_tree(child); | |
2220 | child->mnt.mnt_flags &= ~MNT_LOCKED; | |
2221 | commit_tree(child); | |
2222 | } | |
2223 | put_mountpoint(smp); | |
2224 | unlock_mount_hash(); | |
2225 | ||
2226 | return 0; | |
2227 | ||
2228 | out_cleanup_ids: | |
2229 | while (!hlist_empty(&tree_list)) { | |
2230 | child = hlist_entry(tree_list.first, struct mount, mnt_hash); | |
2231 | child->mnt_parent->mnt_ns->pending_mounts = 0; | |
2232 | umount_tree(child, UMOUNT_SYNC); | |
2233 | } | |
2234 | unlock_mount_hash(); | |
2235 | cleanup_group_ids(source_mnt, NULL); | |
2236 | out: | |
2237 | ns->pending_mounts = 0; | |
2238 | ||
2239 | read_seqlock_excl(&mount_lock); | |
2240 | put_mountpoint(smp); | |
2241 | read_sequnlock_excl(&mount_lock); | |
2242 | ||
2243 | return err; | |
2244 | } | |
2245 | ||
2246 | static struct mountpoint *lock_mount(struct path *path) | |
2247 | { | |
2248 | struct vfsmount *mnt; | |
2249 | struct dentry *dentry = path->dentry; | |
2250 | retry: | |
2251 | inode_lock(dentry->d_inode); | |
2252 | if (unlikely(cant_mount(dentry))) { | |
2253 | inode_unlock(dentry->d_inode); | |
2254 | return ERR_PTR(-ENOENT); | |
2255 | } | |
2256 | namespace_lock(); | |
2257 | mnt = lookup_mnt(path); | |
2258 | if (likely(!mnt)) { | |
2259 | struct mountpoint *mp = get_mountpoint(dentry); | |
2260 | if (IS_ERR(mp)) { | |
2261 | namespace_unlock(); | |
2262 | inode_unlock(dentry->d_inode); | |
2263 | return mp; | |
2264 | } | |
2265 | return mp; | |
2266 | } | |
2267 | namespace_unlock(); | |
2268 | inode_unlock(path->dentry->d_inode); | |
2269 | path_put(path); | |
2270 | path->mnt = mnt; | |
2271 | dentry = path->dentry = dget(mnt->mnt_root); | |
2272 | goto retry; | |
2273 | } | |
2274 | ||
2275 | static void unlock_mount(struct mountpoint *where) | |
2276 | { | |
2277 | struct dentry *dentry = where->m_dentry; | |
2278 | ||
2279 | read_seqlock_excl(&mount_lock); | |
2280 | put_mountpoint(where); | |
2281 | read_sequnlock_excl(&mount_lock); | |
2282 | ||
2283 | namespace_unlock(); | |
2284 | inode_unlock(dentry->d_inode); | |
2285 | } | |
2286 | ||
2287 | static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp) | |
2288 | { | |
2289 | if (mnt->mnt.mnt_sb->s_flags & SB_NOUSER) | |
2290 | return -EINVAL; | |
2291 | ||
2292 | if (d_is_dir(mp->m_dentry) != | |
2293 | d_is_dir(mnt->mnt.mnt_root)) | |
2294 | return -ENOTDIR; | |
2295 | ||
2296 | return attach_recursive_mnt(mnt, p, mp, false); | |
2297 | } | |
2298 | ||
2299 | /* | |
2300 | * Sanity check the flags to change_mnt_propagation. | |
2301 | */ | |
2302 | ||
2303 | static int flags_to_propagation_type(int ms_flags) | |
2304 | { | |
2305 | int type = ms_flags & ~(MS_REC | MS_SILENT); | |
2306 | ||
2307 | /* Fail if any non-propagation flags are set */ | |
2308 | if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) | |
2309 | return 0; | |
2310 | /* Only one propagation flag should be set */ | |
2311 | if (!is_power_of_2(type)) | |
2312 | return 0; | |
2313 | return type; | |
2314 | } | |
2315 | ||
2316 | /* | |
2317 | * recursively change the type of the mountpoint. | |
2318 | */ | |
2319 | static int do_change_type(struct path *path, int ms_flags) | |
2320 | { | |
2321 | struct mount *m; | |
2322 | struct mount *mnt = real_mount(path->mnt); | |
2323 | int recurse = ms_flags & MS_REC; | |
2324 | int type; | |
2325 | int err = 0; | |
2326 | ||
2327 | if (path->dentry != path->mnt->mnt_root) | |
2328 | return -EINVAL; | |
2329 | ||
2330 | type = flags_to_propagation_type(ms_flags); | |
2331 | if (!type) | |
2332 | return -EINVAL; | |
2333 | ||
2334 | namespace_lock(); | |
2335 | if (type == MS_SHARED) { | |
2336 | err = invent_group_ids(mnt, recurse); | |
2337 | if (err) | |
2338 | goto out_unlock; | |
2339 | } | |
2340 | ||
2341 | lock_mount_hash(); | |
2342 | for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) | |
2343 | change_mnt_propagation(m, type); | |
2344 | unlock_mount_hash(); | |
2345 | ||
2346 | out_unlock: | |
2347 | namespace_unlock(); | |
2348 | return err; | |
2349 | } | |
2350 | ||
2351 | static struct mount *__do_loopback(struct path *old_path, int recurse) | |
2352 | { | |
2353 | struct mount *mnt = ERR_PTR(-EINVAL), *old = real_mount(old_path->mnt); | |
2354 | ||
2355 | if (IS_MNT_UNBINDABLE(old)) | |
2356 | return mnt; | |
2357 | ||
2358 | if (!check_mnt(old) && old_path->dentry->d_op != &ns_dentry_operations) | |
2359 | return mnt; | |
2360 | ||
2361 | if (!recurse && has_locked_children(old, old_path->dentry)) | |
2362 | return mnt; | |
2363 | ||
2364 | if (recurse) | |
2365 | mnt = copy_tree(old, old_path->dentry, CL_COPY_MNT_NS_FILE); | |
2366 | else | |
2367 | mnt = clone_mnt(old, old_path->dentry, 0); | |
2368 | ||
2369 | if (!IS_ERR(mnt)) | |
2370 | mnt->mnt.mnt_flags &= ~MNT_LOCKED; | |
2371 | ||
2372 | return mnt; | |
2373 | } | |
2374 | ||
2375 | /* | |
2376 | * do loopback mount. | |
2377 | */ | |
2378 | static int do_loopback(struct path *path, const char *old_name, | |
2379 | int recurse) | |
2380 | { | |
2381 | struct path old_path; | |
2382 | struct mount *mnt = NULL, *parent; | |
2383 | struct mountpoint *mp; | |
2384 | int err; | |
2385 | if (!old_name || !*old_name) | |
2386 | return -EINVAL; | |
2387 | err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); | |
2388 | if (err) | |
2389 | return err; | |
2390 | ||
2391 | err = -EINVAL; | |
2392 | if (mnt_ns_loop(old_path.dentry)) | |
2393 | goto out; | |
2394 | ||
2395 | mp = lock_mount(path); | |
2396 | if (IS_ERR(mp)) { | |
2397 | err = PTR_ERR(mp); | |
2398 | goto out; | |
2399 | } | |
2400 | ||
2401 | parent = real_mount(path->mnt); | |
2402 | if (!check_mnt(parent)) | |
2403 | goto out2; | |
2404 | ||
2405 | mnt = __do_loopback(&old_path, recurse); | |
2406 | if (IS_ERR(mnt)) { | |
2407 | err = PTR_ERR(mnt); | |
2408 | goto out2; | |
2409 | } | |
2410 | ||
2411 | err = graft_tree(mnt, parent, mp); | |
2412 | if (err) { | |
2413 | lock_mount_hash(); | |
2414 | umount_tree(mnt, UMOUNT_SYNC); | |
2415 | unlock_mount_hash(); | |
2416 | } | |
2417 | out2: | |
2418 | unlock_mount(mp); | |
2419 | out: | |
2420 | path_put(&old_path); | |
2421 | return err; | |
2422 | } | |
2423 | ||
2424 | static struct file *open_detached_copy(struct path *path, bool recursive) | |
2425 | { | |
2426 | struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; | |
2427 | struct mnt_namespace *ns = alloc_mnt_ns(user_ns, true); | |
2428 | struct mount *mnt, *p; | |
2429 | struct file *file; | |
2430 | ||
2431 | if (IS_ERR(ns)) | |
2432 | return ERR_CAST(ns); | |
2433 | ||
2434 | namespace_lock(); | |
2435 | mnt = __do_loopback(path, recursive); | |
2436 | if (IS_ERR(mnt)) { | |
2437 | namespace_unlock(); | |
2438 | free_mnt_ns(ns); | |
2439 | return ERR_CAST(mnt); | |
2440 | } | |
2441 | ||
2442 | lock_mount_hash(); | |
2443 | for (p = mnt; p; p = next_mnt(p, mnt)) { | |
2444 | p->mnt_ns = ns; | |
2445 | ns->mounts++; | |
2446 | } | |
2447 | ns->root = mnt; | |
2448 | list_add_tail(&ns->list, &mnt->mnt_list); | |
2449 | mntget(&mnt->mnt); | |
2450 | unlock_mount_hash(); | |
2451 | namespace_unlock(); | |
2452 | ||
2453 | mntput(path->mnt); | |
2454 | path->mnt = &mnt->mnt; | |
2455 | file = dentry_open(path, O_PATH, current_cred()); | |
2456 | if (IS_ERR(file)) | |
2457 | dissolve_on_fput(path->mnt); | |
2458 | else | |
2459 | file->f_mode |= FMODE_NEED_UNMOUNT; | |
2460 | return file; | |
2461 | } | |
2462 | ||
2463 | SYSCALL_DEFINE3(open_tree, int, dfd, const char __user *, filename, unsigned, flags) | |
2464 | { | |
2465 | struct file *file; | |
2466 | struct path path; | |
2467 | int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW; | |
2468 | bool detached = flags & OPEN_TREE_CLONE; | |
2469 | int error; | |
2470 | int fd; | |
2471 | ||
2472 | BUILD_BUG_ON(OPEN_TREE_CLOEXEC != O_CLOEXEC); | |
2473 | ||
2474 | if (flags & ~(AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_RECURSIVE | | |
2475 | AT_SYMLINK_NOFOLLOW | OPEN_TREE_CLONE | | |
2476 | OPEN_TREE_CLOEXEC)) | |
2477 | return -EINVAL; | |
2478 | ||
2479 | if ((flags & (AT_RECURSIVE | OPEN_TREE_CLONE)) == AT_RECURSIVE) | |
2480 | return -EINVAL; | |
2481 | ||
2482 | if (flags & AT_NO_AUTOMOUNT) | |
2483 | lookup_flags &= ~LOOKUP_AUTOMOUNT; | |
2484 | if (flags & AT_SYMLINK_NOFOLLOW) | |
2485 | lookup_flags &= ~LOOKUP_FOLLOW; | |
2486 | if (flags & AT_EMPTY_PATH) | |
2487 | lookup_flags |= LOOKUP_EMPTY; | |
2488 | ||
2489 | if (detached && !may_mount()) | |
2490 | return -EPERM; | |
2491 | ||
2492 | fd = get_unused_fd_flags(flags & O_CLOEXEC); | |
2493 | if (fd < 0) | |
2494 | return fd; | |
2495 | ||
2496 | error = user_path_at(dfd, filename, lookup_flags, &path); | |
2497 | if (unlikely(error)) { | |
2498 | file = ERR_PTR(error); | |
2499 | } else { | |
2500 | if (detached) | |
2501 | file = open_detached_copy(&path, flags & AT_RECURSIVE); | |
2502 | else | |
2503 | file = dentry_open(&path, O_PATH, current_cred()); | |
2504 | path_put(&path); | |
2505 | } | |
2506 | if (IS_ERR(file)) { | |
2507 | put_unused_fd(fd); | |
2508 | return PTR_ERR(file); | |
2509 | } | |
2510 | fd_install(fd, file); | |
2511 | return fd; | |
2512 | } | |
2513 | ||
2514 | /* | |
2515 | * Don't allow locked mount flags to be cleared. | |
2516 | * | |
2517 | * No locks need to be held here while testing the various MNT_LOCK | |
2518 | * flags because those flags can never be cleared once they are set. | |
2519 | */ | |
2520 | static bool can_change_locked_flags(struct mount *mnt, unsigned int mnt_flags) | |
2521 | { | |
2522 | unsigned int fl = mnt->mnt.mnt_flags; | |
2523 | ||
2524 | if ((fl & MNT_LOCK_READONLY) && | |
2525 | !(mnt_flags & MNT_READONLY)) | |
2526 | return false; | |
2527 | ||
2528 | if ((fl & MNT_LOCK_NODEV) && | |
2529 | !(mnt_flags & MNT_NODEV)) | |
2530 | return false; | |
2531 | ||
2532 | if ((fl & MNT_LOCK_NOSUID) && | |
2533 | !(mnt_flags & MNT_NOSUID)) | |
2534 | return false; | |
2535 | ||
2536 | if ((fl & MNT_LOCK_NOEXEC) && | |
2537 | !(mnt_flags & MNT_NOEXEC)) | |
2538 | return false; | |
2539 | ||
2540 | if ((fl & MNT_LOCK_ATIME) && | |
2541 | ((fl & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK))) | |
2542 | return false; | |
2543 | ||
2544 | return true; | |
2545 | } | |
2546 | ||
2547 | static int change_mount_ro_state(struct mount *mnt, unsigned int mnt_flags) | |
2548 | { | |
2549 | bool readonly_request = (mnt_flags & MNT_READONLY); | |
2550 | ||
2551 | if (readonly_request == __mnt_is_readonly(&mnt->mnt)) | |
2552 | return 0; | |
2553 | ||
2554 | if (readonly_request) | |
2555 | return mnt_make_readonly(mnt); | |
2556 | ||
2557 | mnt->mnt.mnt_flags &= ~MNT_READONLY; | |
2558 | return 0; | |
2559 | } | |
2560 | ||
2561 | static void set_mount_attributes(struct mount *mnt, unsigned int mnt_flags) | |
2562 | { | |
2563 | mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK; | |
2564 | mnt->mnt.mnt_flags = mnt_flags; | |
2565 | touch_mnt_namespace(mnt->mnt_ns); | |
2566 | } | |
2567 | ||
2568 | static void mnt_warn_timestamp_expiry(struct path *mountpoint, struct vfsmount *mnt) | |
2569 | { | |
2570 | struct super_block *sb = mnt->mnt_sb; | |
2571 | ||
2572 | if (!__mnt_is_readonly(mnt) && | |
2573 | (ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX > sb->s_time_max)) { | |
2574 | char *buf = (char *)__get_free_page(GFP_KERNEL); | |
2575 | char *mntpath = buf ? d_path(mountpoint, buf, PAGE_SIZE) : ERR_PTR(-ENOMEM); | |
2576 | struct tm tm; | |
2577 | ||
2578 | time64_to_tm(sb->s_time_max, 0, &tm); | |
2579 | ||
2580 | pr_warn("%s filesystem being %s at %s supports timestamps until %04ld (0x%llx)\n", | |
2581 | sb->s_type->name, | |
2582 | is_mounted(mnt) ? "remounted" : "mounted", | |
2583 | mntpath, | |
2584 | tm.tm_year+1900, (unsigned long long)sb->s_time_max); | |
2585 | ||
2586 | free_page((unsigned long)buf); | |
2587 | } | |
2588 | } | |
2589 | ||
2590 | /* | |
2591 | * Handle reconfiguration of the mountpoint only without alteration of the | |
2592 | * superblock it refers to. This is triggered by specifying MS_REMOUNT|MS_BIND | |
2593 | * to mount(2). | |
2594 | */ | |
2595 | static int do_reconfigure_mnt(struct path *path, unsigned int mnt_flags) | |
2596 | { | |
2597 | struct super_block *sb = path->mnt->mnt_sb; | |
2598 | struct mount *mnt = real_mount(path->mnt); | |
2599 | int ret; | |
2600 | ||
2601 | if (!check_mnt(mnt)) | |
2602 | return -EINVAL; | |
2603 | ||
2604 | if (path->dentry != mnt->mnt.mnt_root) | |
2605 | return -EINVAL; | |
2606 | ||
2607 | if (!can_change_locked_flags(mnt, mnt_flags)) | |
2608 | return -EPERM; | |
2609 | ||
2610 | /* | |
2611 | * We're only checking whether the superblock is read-only not | |
2612 | * changing it, so only take down_read(&sb->s_umount). | |
2613 | */ | |
2614 | down_read(&sb->s_umount); | |
2615 | lock_mount_hash(); | |
2616 | ret = change_mount_ro_state(mnt, mnt_flags); | |
2617 | if (ret == 0) | |
2618 | set_mount_attributes(mnt, mnt_flags); | |
2619 | unlock_mount_hash(); | |
2620 | up_read(&sb->s_umount); | |
2621 | ||
2622 | mnt_warn_timestamp_expiry(path, &mnt->mnt); | |
2623 | ||
2624 | return ret; | |
2625 | } | |
2626 | ||
2627 | /* | |
2628 | * change filesystem flags. dir should be a physical root of filesystem. | |
2629 | * If you've mounted a non-root directory somewhere and want to do remount | |
2630 | * on it - tough luck. | |
2631 | */ | |
2632 | static int do_remount(struct path *path, int ms_flags, int sb_flags, | |
2633 | int mnt_flags, void *data) | |
2634 | { | |
2635 | int err; | |
2636 | struct super_block *sb = path->mnt->mnt_sb; | |
2637 | struct mount *mnt = real_mount(path->mnt); | |
2638 | struct fs_context *fc; | |
2639 | ||
2640 | if (!check_mnt(mnt)) | |
2641 | return -EINVAL; | |
2642 | ||
2643 | if (path->dentry != path->mnt->mnt_root) | |
2644 | return -EINVAL; | |
2645 | ||
2646 | if (!can_change_locked_flags(mnt, mnt_flags)) | |
2647 | return -EPERM; | |
2648 | ||
2649 | fc = fs_context_for_reconfigure(path->dentry, sb_flags, MS_RMT_MASK); | |
2650 | if (IS_ERR(fc)) | |
2651 | return PTR_ERR(fc); | |
2652 | ||
2653 | fc->oldapi = true; | |
2654 | err = parse_monolithic_mount_data(fc, data); | |
2655 | if (!err) { | |
2656 | down_write(&sb->s_umount); | |
2657 | err = -EPERM; | |
2658 | if (ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) { | |
2659 | err = reconfigure_super(fc); | |
2660 | if (!err) { | |
2661 | lock_mount_hash(); | |
2662 | set_mount_attributes(mnt, mnt_flags); | |
2663 | unlock_mount_hash(); | |
2664 | } | |
2665 | } | |
2666 | up_write(&sb->s_umount); | |
2667 | } | |
2668 | ||
2669 | mnt_warn_timestamp_expiry(path, &mnt->mnt); | |
2670 | ||
2671 | put_fs_context(fc); | |
2672 | return err; | |
2673 | } | |
2674 | ||
2675 | static inline int tree_contains_unbindable(struct mount *mnt) | |
2676 | { | |
2677 | struct mount *p; | |
2678 | for (p = mnt; p; p = next_mnt(p, mnt)) { | |
2679 | if (IS_MNT_UNBINDABLE(p)) | |
2680 | return 1; | |
2681 | } | |
2682 | return 0; | |
2683 | } | |
2684 | ||
2685 | /* | |
2686 | * Check that there aren't references to earlier/same mount namespaces in the | |
2687 | * specified subtree. Such references can act as pins for mount namespaces | |
2688 | * that aren't checked by the mount-cycle checking code, thereby allowing | |
2689 | * cycles to be made. | |
2690 | */ | |
2691 | static bool check_for_nsfs_mounts(struct mount *subtree) | |
2692 | { | |
2693 | struct mount *p; | |
2694 | bool ret = false; | |
2695 | ||
2696 | lock_mount_hash(); | |
2697 | for (p = subtree; p; p = next_mnt(p, subtree)) | |
2698 | if (mnt_ns_loop(p->mnt.mnt_root)) | |
2699 | goto out; | |
2700 | ||
2701 | ret = true; | |
2702 | out: | |
2703 | unlock_mount_hash(); | |
2704 | return ret; | |
2705 | } | |
2706 | ||
2707 | static int do_set_group(struct path *from_path, struct path *to_path) | |
2708 | { | |
2709 | struct mount *from, *to; | |
2710 | int err; | |
2711 | ||
2712 | from = real_mount(from_path->mnt); | |
2713 | to = real_mount(to_path->mnt); | |
2714 | ||
2715 | namespace_lock(); | |
2716 | ||
2717 | err = -EINVAL; | |
2718 | /* To and From must be mounted */ | |
2719 | if (!is_mounted(&from->mnt)) | |
2720 | goto out; | |
2721 | if (!is_mounted(&to->mnt)) | |
2722 | goto out; | |
2723 | ||
2724 | err = -EPERM; | |
2725 | /* We should be allowed to modify mount namespaces of both mounts */ | |
2726 | if (!ns_capable(from->mnt_ns->user_ns, CAP_SYS_ADMIN)) | |
2727 | goto out; | |
2728 | if (!ns_capable(to->mnt_ns->user_ns, CAP_SYS_ADMIN)) | |
2729 | goto out; | |
2730 | ||
2731 | err = -EINVAL; | |
2732 | /* To and From paths should be mount roots */ | |
2733 | if (from_path->dentry != from_path->mnt->mnt_root) | |
2734 | goto out; | |
2735 | if (to_path->dentry != to_path->mnt->mnt_root) | |
2736 | goto out; | |
2737 | ||
2738 | /* Setting sharing groups is only allowed across same superblock */ | |
2739 | if (from->mnt.mnt_sb != to->mnt.mnt_sb) | |
2740 | goto out; | |
2741 | ||
2742 | /* From mount root should be wider than To mount root */ | |
2743 | if (!is_subdir(to->mnt.mnt_root, from->mnt.mnt_root)) | |
2744 | goto out; | |
2745 | ||
2746 | /* From mount should not have locked children in place of To's root */ | |
2747 | if (has_locked_children(from, to->mnt.mnt_root)) | |
2748 | goto out; | |
2749 | ||
2750 | /* Setting sharing groups is only allowed on private mounts */ | |
2751 | if (IS_MNT_SHARED(to) || IS_MNT_SLAVE(to)) | |
2752 | goto out; | |
2753 | ||
2754 | /* From should not be private */ | |
2755 | if (!IS_MNT_SHARED(from) && !IS_MNT_SLAVE(from)) | |
2756 | goto out; | |
2757 | ||
2758 | if (IS_MNT_SLAVE(from)) { | |
2759 | struct mount *m = from->mnt_master; | |
2760 | ||
2761 | list_add(&to->mnt_slave, &m->mnt_slave_list); | |
2762 | to->mnt_master = m; | |
2763 | } | |
2764 | ||
2765 | if (IS_MNT_SHARED(from)) { | |
2766 | to->mnt_group_id = from->mnt_group_id; | |
2767 | list_add(&to->mnt_share, &from->mnt_share); | |
2768 | lock_mount_hash(); | |
2769 | set_mnt_shared(to); | |
2770 | unlock_mount_hash(); | |
2771 | } | |
2772 | ||
2773 | err = 0; | |
2774 | out: | |
2775 | namespace_unlock(); | |
2776 | return err; | |
2777 | } | |
2778 | ||
2779 | static int do_move_mount(struct path *old_path, struct path *new_path) | |
2780 | { | |
2781 | struct mnt_namespace *ns; | |
2782 | struct mount *p; | |
2783 | struct mount *old; | |
2784 | struct mount *parent; | |
2785 | struct mountpoint *mp, *old_mp; | |
2786 | int err; | |
2787 | bool attached; | |
2788 | ||
2789 | mp = lock_mount(new_path); | |
2790 | if (IS_ERR(mp)) | |
2791 | return PTR_ERR(mp); | |
2792 | ||
2793 | old = real_mount(old_path->mnt); | |
2794 | p = real_mount(new_path->mnt); | |
2795 | parent = old->mnt_parent; | |
2796 | attached = mnt_has_parent(old); | |
2797 | old_mp = old->mnt_mp; | |
2798 | ns = old->mnt_ns; | |
2799 | ||
2800 | err = -EINVAL; | |
2801 | /* The mountpoint must be in our namespace. */ | |
2802 | if (!check_mnt(p)) | |
2803 | goto out; | |
2804 | ||
2805 | /* The thing moved must be mounted... */ | |
2806 | if (!is_mounted(&old->mnt)) | |
2807 | goto out; | |
2808 | ||
2809 | /* ... and either ours or the root of anon namespace */ | |
2810 | if (!(attached ? check_mnt(old) : is_anon_ns(ns))) | |
2811 | goto out; | |
2812 | ||
2813 | if (old->mnt.mnt_flags & MNT_LOCKED) | |
2814 | goto out; | |
2815 | ||
2816 | if (old_path->dentry != old_path->mnt->mnt_root) | |
2817 | goto out; | |
2818 | ||
2819 | if (d_is_dir(new_path->dentry) != | |
2820 | d_is_dir(old_path->dentry)) | |
2821 | goto out; | |
2822 | /* | |
2823 | * Don't move a mount residing in a shared parent. | |
2824 | */ | |
2825 | if (attached && IS_MNT_SHARED(parent)) | |
2826 | goto out; | |
2827 | /* | |
2828 | * Don't move a mount tree containing unbindable mounts to a destination | |
2829 | * mount which is shared. | |
2830 | */ | |
2831 | if (IS_MNT_SHARED(p) && tree_contains_unbindable(old)) | |
2832 | goto out; | |
2833 | err = -ELOOP; | |
2834 | if (!check_for_nsfs_mounts(old)) | |
2835 | goto out; | |
2836 | for (; mnt_has_parent(p); p = p->mnt_parent) | |
2837 | if (p == old) | |
2838 | goto out; | |
2839 | ||
2840 | err = attach_recursive_mnt(old, real_mount(new_path->mnt), mp, | |
2841 | attached); | |
2842 | if (err) | |
2843 | goto out; | |
2844 | ||
2845 | /* if the mount is moved, it should no longer be expire | |
2846 | * automatically */ | |
2847 | list_del_init(&old->mnt_expire); | |
2848 | if (attached) | |
2849 | put_mountpoint(old_mp); | |
2850 | out: | |
2851 | unlock_mount(mp); | |
2852 | if (!err) { | |
2853 | if (attached) | |
2854 | mntput_no_expire(parent); | |
2855 | else | |
2856 | free_mnt_ns(ns); | |
2857 | } | |
2858 | return err; | |
2859 | } | |
2860 | ||
2861 | static int do_move_mount_old(struct path *path, const char *old_name) | |
2862 | { | |
2863 | struct path old_path; | |
2864 | int err; | |
2865 | ||
2866 | if (!old_name || !*old_name) | |
2867 | return -EINVAL; | |
2868 | ||
2869 | err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); | |
2870 | if (err) | |
2871 | return err; | |
2872 | ||
2873 | err = do_move_mount(&old_path, path); | |
2874 | path_put(&old_path); | |
2875 | return err; | |
2876 | } | |
2877 | ||
2878 | /* | |
2879 | * add a mount into a namespace's mount tree | |
2880 | */ | |
2881 | static int do_add_mount(struct mount *newmnt, struct mountpoint *mp, | |
2882 | struct path *path, int mnt_flags) | |
2883 | { | |
2884 | struct mount *parent = real_mount(path->mnt); | |
2885 | ||
2886 | mnt_flags &= ~MNT_INTERNAL_FLAGS; | |
2887 | ||
2888 | if (unlikely(!check_mnt(parent))) { | |
2889 | /* that's acceptable only for automounts done in private ns */ | |
2890 | if (!(mnt_flags & MNT_SHRINKABLE)) | |
2891 | return -EINVAL; | |
2892 | /* ... and for those we'd better have mountpoint still alive */ | |
2893 | if (!parent->mnt_ns) | |
2894 | return -EINVAL; | |
2895 | } | |
2896 | ||
2897 | /* Refuse the same filesystem on the same mount point */ | |
2898 | if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && | |
2899 | path->mnt->mnt_root == path->dentry) | |
2900 | return -EBUSY; | |
2901 | ||
2902 | if (d_is_symlink(newmnt->mnt.mnt_root)) | |
2903 | return -EINVAL; | |
2904 | ||
2905 | newmnt->mnt.mnt_flags = mnt_flags; | |
2906 | return graft_tree(newmnt, parent, mp); | |
2907 | } | |
2908 | ||
2909 | static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags); | |
2910 | ||
2911 | /* | |
2912 | * Create a new mount using a superblock configuration and request it | |
2913 | * be added to the namespace tree. | |
2914 | */ | |
2915 | static int do_new_mount_fc(struct fs_context *fc, struct path *mountpoint, | |
2916 | unsigned int mnt_flags) | |
2917 | { | |
2918 | struct vfsmount *mnt; | |
2919 | struct mountpoint *mp; | |
2920 | struct super_block *sb = fc->root->d_sb; | |
2921 | int error; | |
2922 | ||
2923 | error = security_sb_kern_mount(sb); | |
2924 | if (!error && mount_too_revealing(sb, &mnt_flags)) | |
2925 | error = -EPERM; | |
2926 | ||
2927 | if (unlikely(error)) { | |
2928 | fc_drop_locked(fc); | |
2929 | return error; | |
2930 | } | |
2931 | ||
2932 | up_write(&sb->s_umount); | |
2933 | ||
2934 | mnt = vfs_create_mount(fc); | |
2935 | if (IS_ERR(mnt)) | |
2936 | return PTR_ERR(mnt); | |
2937 | ||
2938 | mnt_warn_timestamp_expiry(mountpoint, mnt); | |
2939 | ||
2940 | mp = lock_mount(mountpoint); | |
2941 | if (IS_ERR(mp)) { | |
2942 | mntput(mnt); | |
2943 | return PTR_ERR(mp); | |
2944 | } | |
2945 | error = do_add_mount(real_mount(mnt), mp, mountpoint, mnt_flags); | |
2946 | unlock_mount(mp); | |
2947 | if (error < 0) | |
2948 | mntput(mnt); | |
2949 | return error; | |
2950 | } | |
2951 | ||
2952 | /* | |
2953 | * create a new mount for userspace and request it to be added into the | |
2954 | * namespace's tree | |
2955 | */ | |
2956 | static int do_new_mount(struct path *path, const char *fstype, int sb_flags, | |
2957 | int mnt_flags, const char *name, void *data) | |
2958 | { | |
2959 | struct file_system_type *type; | |
2960 | struct fs_context *fc; | |
2961 | const char *subtype = NULL; | |
2962 | int err = 0; | |
2963 | ||
2964 | if (!fstype) | |
2965 | return -EINVAL; | |
2966 | ||
2967 | type = get_fs_type(fstype); | |
2968 | if (!type) | |
2969 | return -ENODEV; | |
2970 | ||
2971 | if (type->fs_flags & FS_HAS_SUBTYPE) { | |
2972 | subtype = strchr(fstype, '.'); | |
2973 | if (subtype) { | |
2974 | subtype++; | |
2975 | if (!*subtype) { | |
2976 | put_filesystem(type); | |
2977 | return -EINVAL; | |
2978 | } | |
2979 | } | |
2980 | } | |
2981 | ||
2982 | fc = fs_context_for_mount(type, sb_flags); | |
2983 | put_filesystem(type); | |
2984 | if (IS_ERR(fc)) | |
2985 | return PTR_ERR(fc); | |
2986 | ||
2987 | if (subtype) | |
2988 | err = vfs_parse_fs_string(fc, "subtype", | |
2989 | subtype, strlen(subtype)); | |
2990 | if (!err && name) | |
2991 | err = vfs_parse_fs_string(fc, "source", name, strlen(name)); | |
2992 | if (!err) | |
2993 | err = parse_monolithic_mount_data(fc, data); | |
2994 | if (!err && !mount_capable(fc)) | |
2995 | err = -EPERM; | |
2996 | if (!err) | |
2997 | err = vfs_get_tree(fc); | |
2998 | if (!err) | |
2999 | err = do_new_mount_fc(fc, path, mnt_flags); | |
3000 | ||
3001 | put_fs_context(fc); | |
3002 | return err; | |
3003 | } | |
3004 | ||
3005 | int finish_automount(struct vfsmount *m, struct path *path) | |
3006 | { | |
3007 | struct dentry *dentry = path->dentry; | |
3008 | struct mountpoint *mp; | |
3009 | struct mount *mnt; | |
3010 | int err; | |
3011 | ||
3012 | if (!m) | |
3013 | return 0; | |
3014 | if (IS_ERR(m)) | |
3015 | return PTR_ERR(m); | |
3016 | ||
3017 | mnt = real_mount(m); | |
3018 | /* The new mount record should have at least 2 refs to prevent it being | |
3019 | * expired before we get a chance to add it | |
3020 | */ | |
3021 | BUG_ON(mnt_get_count(mnt) < 2); | |
3022 | ||
3023 | if (m->mnt_sb == path->mnt->mnt_sb && | |
3024 | m->mnt_root == dentry) { | |
3025 | err = -ELOOP; | |
3026 | goto discard; | |
3027 | } | |
3028 | ||
3029 | /* | |
3030 | * we don't want to use lock_mount() - in this case finding something | |
3031 | * that overmounts our mountpoint to be means "quitely drop what we've | |
3032 | * got", not "try to mount it on top". | |
3033 | */ | |
3034 | inode_lock(dentry->d_inode); | |
3035 | namespace_lock(); | |
3036 | if (unlikely(cant_mount(dentry))) { | |
3037 | err = -ENOENT; | |
3038 | goto discard_locked; | |
3039 | } | |
3040 | rcu_read_lock(); | |
3041 | if (unlikely(__lookup_mnt(path->mnt, dentry))) { | |
3042 | rcu_read_unlock(); | |
3043 | err = 0; | |
3044 | goto discard_locked; | |
3045 | } | |
3046 | rcu_read_unlock(); | |
3047 | mp = get_mountpoint(dentry); | |
3048 | if (IS_ERR(mp)) { | |
3049 | err = PTR_ERR(mp); | |
3050 | goto discard_locked; | |
3051 | } | |
3052 | ||
3053 | err = do_add_mount(mnt, mp, path, path->mnt->mnt_flags | MNT_SHRINKABLE); | |
3054 | unlock_mount(mp); | |
3055 | if (unlikely(err)) | |
3056 | goto discard; | |
3057 | mntput(m); | |
3058 | return 0; | |
3059 | ||
3060 | discard_locked: | |
3061 | namespace_unlock(); | |
3062 | inode_unlock(dentry->d_inode); | |
3063 | discard: | |
3064 | /* remove m from any expiration list it may be on */ | |
3065 | if (!list_empty(&mnt->mnt_expire)) { | |
3066 | namespace_lock(); | |
3067 | list_del_init(&mnt->mnt_expire); | |
3068 | namespace_unlock(); | |
3069 | } | |
3070 | mntput(m); | |
3071 | mntput(m); | |
3072 | return err; | |
3073 | } | |
3074 | ||
3075 | /** | |
3076 | * mnt_set_expiry - Put a mount on an expiration list | |
3077 | * @mnt: The mount to list. | |
3078 | * @expiry_list: The list to add the mount to. | |
3079 | */ | |
3080 | void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list) | |
3081 | { | |
3082 | namespace_lock(); | |
3083 | ||
3084 | list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list); | |
3085 | ||
3086 | namespace_unlock(); | |
3087 | } | |
3088 | EXPORT_SYMBOL(mnt_set_expiry); | |
3089 | ||
3090 | /* | |
3091 | * process a list of expirable mountpoints with the intent of discarding any | |
3092 | * mountpoints that aren't in use and haven't been touched since last we came | |
3093 | * here | |
3094 | */ | |
3095 | void mark_mounts_for_expiry(struct list_head *mounts) | |
3096 | { | |
3097 | struct mount *mnt, *next; | |
3098 | LIST_HEAD(graveyard); | |
3099 | ||
3100 | if (list_empty(mounts)) | |
3101 | return; | |
3102 | ||
3103 | namespace_lock(); | |
3104 | lock_mount_hash(); | |
3105 | ||
3106 | /* extract from the expiration list every vfsmount that matches the | |
3107 | * following criteria: | |
3108 | * - only referenced by its parent vfsmount | |
3109 | * - still marked for expiry (marked on the last call here; marks are | |
3110 | * cleared by mntput()) | |
3111 | */ | |
3112 | list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { | |
3113 | if (!xchg(&mnt->mnt_expiry_mark, 1) || | |
3114 | propagate_mount_busy(mnt, 1)) | |
3115 | continue; | |
3116 | list_move(&mnt->mnt_expire, &graveyard); | |
3117 | } | |
3118 | while (!list_empty(&graveyard)) { | |
3119 | mnt = list_first_entry(&graveyard, struct mount, mnt_expire); | |
3120 | touch_mnt_namespace(mnt->mnt_ns); | |
3121 | umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC); | |
3122 | } | |
3123 | unlock_mount_hash(); | |
3124 | namespace_unlock(); | |
3125 | } | |
3126 | ||
3127 | EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); | |
3128 | ||
3129 | /* | |
3130 | * Ripoff of 'select_parent()' | |
3131 | * | |
3132 | * search the list of submounts for a given mountpoint, and move any | |
3133 | * shrinkable submounts to the 'graveyard' list. | |
3134 | */ | |
3135 | static int select_submounts(struct mount *parent, struct list_head *graveyard) | |
3136 | { | |
3137 | struct mount *this_parent = parent; | |
3138 | struct list_head *next; | |
3139 | int found = 0; | |
3140 | ||
3141 | repeat: | |
3142 | next = this_parent->mnt_mounts.next; | |
3143 | resume: | |
3144 | while (next != &this_parent->mnt_mounts) { | |
3145 | struct list_head *tmp = next; | |
3146 | struct mount *mnt = list_entry(tmp, struct mount, mnt_child); | |
3147 | ||
3148 | next = tmp->next; | |
3149 | if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE)) | |
3150 | continue; | |
3151 | /* | |
3152 | * Descend a level if the d_mounts list is non-empty. | |
3153 | */ | |
3154 | if (!list_empty(&mnt->mnt_mounts)) { | |
3155 | this_parent = mnt; | |
3156 | goto repeat; | |
3157 | } | |
3158 | ||
3159 | if (!propagate_mount_busy(mnt, 1)) { | |
3160 | list_move_tail(&mnt->mnt_expire, graveyard); | |
3161 | found++; | |
3162 | } | |
3163 | } | |
3164 | /* | |
3165 | * All done at this level ... ascend and resume the search | |
3166 | */ | |
3167 | if (this_parent != parent) { | |
3168 | next = this_parent->mnt_child.next; | |
3169 | this_parent = this_parent->mnt_parent; | |
3170 | goto resume; | |
3171 | } | |
3172 | return found; | |
3173 | } | |
3174 | ||
3175 | /* | |
3176 | * process a list of expirable mountpoints with the intent of discarding any | |
3177 | * submounts of a specific parent mountpoint | |
3178 | * | |
3179 | * mount_lock must be held for write | |
3180 | */ | |
3181 | static void shrink_submounts(struct mount *mnt) | |
3182 | { | |
3183 | LIST_HEAD(graveyard); | |
3184 | struct mount *m; | |
3185 | ||
3186 | /* extract submounts of 'mountpoint' from the expiration list */ | |
3187 | while (select_submounts(mnt, &graveyard)) { | |
3188 | while (!list_empty(&graveyard)) { | |
3189 | m = list_first_entry(&graveyard, struct mount, | |
3190 | mnt_expire); | |
3191 | touch_mnt_namespace(m->mnt_ns); | |
3192 | umount_tree(m, UMOUNT_PROPAGATE|UMOUNT_SYNC); | |
3193 | } | |
3194 | } | |
3195 | } | |
3196 | ||
3197 | static void *copy_mount_options(const void __user * data) | |
3198 | { | |
3199 | char *copy; | |
3200 | unsigned left, offset; | |
3201 | ||
3202 | if (!data) | |
3203 | return NULL; | |
3204 | ||
3205 | copy = kmalloc(PAGE_SIZE, GFP_KERNEL); | |
3206 | if (!copy) | |
3207 | return ERR_PTR(-ENOMEM); | |
3208 | ||
3209 | left = copy_from_user(copy, data, PAGE_SIZE); | |
3210 | ||
3211 | /* | |
3212 | * Not all architectures have an exact copy_from_user(). Resort to | |
3213 | * byte at a time. | |
3214 | */ | |
3215 | offset = PAGE_SIZE - left; | |
3216 | while (left) { | |
3217 | char c; | |
3218 | if (get_user(c, (const char __user *)data + offset)) | |
3219 | break; | |
3220 | copy[offset] = c; | |
3221 | left--; | |
3222 | offset++; | |
3223 | } | |
3224 | ||
3225 | if (left == PAGE_SIZE) { | |
3226 | kfree(copy); | |
3227 | return ERR_PTR(-EFAULT); | |
3228 | } | |
3229 | ||
3230 | return copy; | |
3231 | } | |
3232 | ||
3233 | static char *copy_mount_string(const void __user *data) | |
3234 | { | |
3235 | return data ? strndup_user(data, PATH_MAX) : NULL; | |
3236 | } | |
3237 | ||
3238 | /* | |
3239 | * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to | |
3240 | * be given to the mount() call (ie: read-only, no-dev, no-suid etc). | |
3241 | * | |
3242 | * data is a (void *) that can point to any structure up to | |
3243 | * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent | |
3244 | * information (or be NULL). | |
3245 | * | |
3246 | * Pre-0.97 versions of mount() didn't have a flags word. | |
3247 | * When the flags word was introduced its top half was required | |
3248 | * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. | |
3249 | * Therefore, if this magic number is present, it carries no information | |
3250 | * and must be discarded. | |
3251 | */ | |
3252 | int path_mount(const char *dev_name, struct path *path, | |
3253 | const char *type_page, unsigned long flags, void *data_page) | |
3254 | { | |
3255 | unsigned int mnt_flags = 0, sb_flags; | |
3256 | int ret; | |
3257 | ||
3258 | /* Discard magic */ | |
3259 | if ((flags & MS_MGC_MSK) == MS_MGC_VAL) | |
3260 | flags &= ~MS_MGC_MSK; | |
3261 | ||
3262 | /* Basic sanity checks */ | |
3263 | if (data_page) | |
3264 | ((char *)data_page)[PAGE_SIZE - 1] = 0; | |
3265 | ||
3266 | if (flags & MS_NOUSER) | |
3267 | return -EINVAL; | |
3268 | ||
3269 | ret = security_sb_mount(dev_name, path, type_page, flags, data_page); | |
3270 | if (ret) | |
3271 | return ret; | |
3272 | if (!may_mount()) | |
3273 | return -EPERM; | |
3274 | if (flags & SB_MANDLOCK) | |
3275 | warn_mandlock(); | |
3276 | ||
3277 | /* Default to relatime unless overriden */ | |
3278 | if (!(flags & MS_NOATIME)) | |
3279 | mnt_flags |= MNT_RELATIME; | |
3280 | ||
3281 | /* Separate the per-mountpoint flags */ | |
3282 | if (flags & MS_NOSUID) | |
3283 | mnt_flags |= MNT_NOSUID; | |
3284 | if (flags & MS_NODEV) | |
3285 | mnt_flags |= MNT_NODEV; | |
3286 | if (flags & MS_NOEXEC) | |
3287 | mnt_flags |= MNT_NOEXEC; | |
3288 | if (flags & MS_NOATIME) | |
3289 | mnt_flags |= MNT_NOATIME; | |
3290 | if (flags & MS_NODIRATIME) | |
3291 | mnt_flags |= MNT_NODIRATIME; | |
3292 | if (flags & MS_STRICTATIME) | |
3293 | mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); | |
3294 | if (flags & MS_RDONLY) | |
3295 | mnt_flags |= MNT_READONLY; | |
3296 | if (flags & MS_NOSYMFOLLOW) | |
3297 | mnt_flags |= MNT_NOSYMFOLLOW; | |
3298 | ||
3299 | /* The default atime for remount is preservation */ | |
3300 | if ((flags & MS_REMOUNT) && | |
3301 | ((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME | | |
3302 | MS_STRICTATIME)) == 0)) { | |
3303 | mnt_flags &= ~MNT_ATIME_MASK; | |
3304 | mnt_flags |= path->mnt->mnt_flags & MNT_ATIME_MASK; | |
3305 | } | |
3306 | ||
3307 | sb_flags = flags & (SB_RDONLY | | |
3308 | SB_SYNCHRONOUS | | |
3309 | SB_MANDLOCK | | |
3310 | SB_DIRSYNC | | |
3311 | SB_SILENT | | |
3312 | SB_POSIXACL | | |
3313 | SB_LAZYTIME | | |
3314 | SB_I_VERSION); | |
3315 | ||
3316 | if ((flags & (MS_REMOUNT | MS_BIND)) == (MS_REMOUNT | MS_BIND)) | |
3317 | return do_reconfigure_mnt(path, mnt_flags); | |
3318 | if (flags & MS_REMOUNT) | |
3319 | return do_remount(path, flags, sb_flags, mnt_flags, data_page); | |
3320 | if (flags & MS_BIND) | |
3321 | return do_loopback(path, dev_name, flags & MS_REC); | |
3322 | if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) | |
3323 | return do_change_type(path, flags); | |
3324 | if (flags & MS_MOVE) | |
3325 | return do_move_mount_old(path, dev_name); | |
3326 | ||
3327 | return do_new_mount(path, type_page, sb_flags, mnt_flags, dev_name, | |
3328 | data_page); | |
3329 | } | |
3330 | ||
3331 | long do_mount(const char *dev_name, const char __user *dir_name, | |
3332 | const char *type_page, unsigned long flags, void *data_page) | |
3333 | { | |
3334 | struct path path; | |
3335 | int ret; | |
3336 | ||
3337 | ret = user_path_at(AT_FDCWD, dir_name, LOOKUP_FOLLOW, &path); | |
3338 | if (ret) | |
3339 | return ret; | |
3340 | ret = path_mount(dev_name, &path, type_page, flags, data_page); | |
3341 | path_put(&path); | |
3342 | return ret; | |
3343 | } | |
3344 | ||
3345 | static struct ucounts *inc_mnt_namespaces(struct user_namespace *ns) | |
3346 | { | |
3347 | return inc_ucount(ns, current_euid(), UCOUNT_MNT_NAMESPACES); | |
3348 | } | |
3349 | ||
3350 | static void dec_mnt_namespaces(struct ucounts *ucounts) | |
3351 | { | |
3352 | dec_ucount(ucounts, UCOUNT_MNT_NAMESPACES); | |
3353 | } | |
3354 | ||
3355 | static void free_mnt_ns(struct mnt_namespace *ns) | |
3356 | { | |
3357 | if (!is_anon_ns(ns)) | |
3358 | ns_free_inum(&ns->ns); | |
3359 | dec_mnt_namespaces(ns->ucounts); | |
3360 | put_user_ns(ns->user_ns); | |
3361 | kfree(ns); | |
3362 | } | |
3363 | ||
3364 | /* | |
3365 | * Assign a sequence number so we can detect when we attempt to bind | |
3366 | * mount a reference to an older mount namespace into the current | |
3367 | * mount namespace, preventing reference counting loops. A 64bit | |
3368 | * number incrementing at 10Ghz will take 12,427 years to wrap which | |
3369 | * is effectively never, so we can ignore the possibility. | |
3370 | */ | |
3371 | static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1); | |
3372 | ||
3373 | static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool anon) | |
3374 | { | |
3375 | struct mnt_namespace *new_ns; | |
3376 | struct ucounts *ucounts; | |
3377 | int ret; | |
3378 | ||
3379 | ucounts = inc_mnt_namespaces(user_ns); | |
3380 | if (!ucounts) | |
3381 | return ERR_PTR(-ENOSPC); | |
3382 | ||
3383 | new_ns = kzalloc(sizeof(struct mnt_namespace), GFP_KERNEL_ACCOUNT); | |
3384 | if (!new_ns) { | |
3385 | dec_mnt_namespaces(ucounts); | |
3386 | return ERR_PTR(-ENOMEM); | |
3387 | } | |
3388 | if (!anon) { | |
3389 | ret = ns_alloc_inum(&new_ns->ns); | |
3390 | if (ret) { | |
3391 | kfree(new_ns); | |
3392 | dec_mnt_namespaces(ucounts); | |
3393 | return ERR_PTR(ret); | |
3394 | } | |
3395 | } | |
3396 | new_ns->ns.ops = &mntns_operations; | |
3397 | if (!anon) | |
3398 | new_ns->seq = atomic64_add_return(1, &mnt_ns_seq); | |
3399 | refcount_set(&new_ns->ns.count, 1); | |
3400 | INIT_LIST_HEAD(&new_ns->list); | |
3401 | init_waitqueue_head(&new_ns->poll); | |
3402 | spin_lock_init(&new_ns->ns_lock); | |
3403 | new_ns->user_ns = get_user_ns(user_ns); | |
3404 | new_ns->ucounts = ucounts; | |
3405 | return new_ns; | |
3406 | } | |
3407 | ||
3408 | __latent_entropy | |
3409 | struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, | |
3410 | struct user_namespace *user_ns, struct fs_struct *new_fs) | |
3411 | { | |
3412 | struct mnt_namespace *new_ns; | |
3413 | struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; | |
3414 | struct mount *p, *q; | |
3415 | struct mount *old; | |
3416 | struct mount *new; | |
3417 | int copy_flags; | |
3418 | ||
3419 | BUG_ON(!ns); | |
3420 | ||
3421 | if (likely(!(flags & CLONE_NEWNS))) { | |
3422 | get_mnt_ns(ns); | |
3423 | return ns; | |
3424 | } | |
3425 | ||
3426 | old = ns->root; | |
3427 | ||
3428 | new_ns = alloc_mnt_ns(user_ns, false); | |
3429 | if (IS_ERR(new_ns)) | |
3430 | return new_ns; | |
3431 | ||
3432 | namespace_lock(); | |
3433 | /* First pass: copy the tree topology */ | |
3434 | copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE; | |
3435 | if (user_ns != ns->user_ns) | |
3436 | copy_flags |= CL_SHARED_TO_SLAVE; | |
3437 | new = copy_tree(old, old->mnt.mnt_root, copy_flags); | |
3438 | if (IS_ERR(new)) { | |
3439 | namespace_unlock(); | |
3440 | free_mnt_ns(new_ns); | |
3441 | return ERR_CAST(new); | |
3442 | } | |
3443 | if (user_ns != ns->user_ns) { | |
3444 | lock_mount_hash(); | |
3445 | lock_mnt_tree(new); | |
3446 | unlock_mount_hash(); | |
3447 | } | |
3448 | new_ns->root = new; | |
3449 | list_add_tail(&new_ns->list, &new->mnt_list); | |
3450 | ||
3451 | /* | |
3452 | * Second pass: switch the tsk->fs->* elements and mark new vfsmounts | |
3453 | * as belonging to new namespace. We have already acquired a private | |
3454 | * fs_struct, so tsk->fs->lock is not needed. | |
3455 | */ | |
3456 | p = old; | |
3457 | q = new; | |
3458 | while (p) { | |
3459 | q->mnt_ns = new_ns; | |
3460 | new_ns->mounts++; | |
3461 | if (new_fs) { | |
3462 | if (&p->mnt == new_fs->root.mnt) { | |
3463 | new_fs->root.mnt = mntget(&q->mnt); | |
3464 | rootmnt = &p->mnt; | |
3465 | } | |
3466 | if (&p->mnt == new_fs->pwd.mnt) { | |
3467 | new_fs->pwd.mnt = mntget(&q->mnt); | |
3468 | pwdmnt = &p->mnt; | |
3469 | } | |
3470 | } | |
3471 | p = next_mnt(p, old); | |
3472 | q = next_mnt(q, new); | |
3473 | if (!q) | |
3474 | break; | |
3475 | while (p->mnt.mnt_root != q->mnt.mnt_root) | |
3476 | p = next_mnt(p, old); | |
3477 | } | |
3478 | namespace_unlock(); | |
3479 | ||
3480 | if (rootmnt) | |
3481 | mntput(rootmnt); | |
3482 | if (pwdmnt) | |
3483 | mntput(pwdmnt); | |
3484 | ||
3485 | return new_ns; | |
3486 | } | |
3487 | ||
3488 | struct dentry *mount_subtree(struct vfsmount *m, const char *name) | |
3489 | { | |
3490 | struct mount *mnt = real_mount(m); | |
3491 | struct mnt_namespace *ns; | |
3492 | struct super_block *s; | |
3493 | struct path path; | |
3494 | int err; | |
3495 | ||
3496 | ns = alloc_mnt_ns(&init_user_ns, true); | |
3497 | if (IS_ERR(ns)) { | |
3498 | mntput(m); | |
3499 | return ERR_CAST(ns); | |
3500 | } | |
3501 | mnt->mnt_ns = ns; | |
3502 | ns->root = mnt; | |
3503 | ns->mounts++; | |
3504 | list_add(&mnt->mnt_list, &ns->list); | |
3505 | ||
3506 | err = vfs_path_lookup(m->mnt_root, m, | |
3507 | name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); | |
3508 | ||
3509 | put_mnt_ns(ns); | |
3510 | ||
3511 | if (err) | |
3512 | return ERR_PTR(err); | |
3513 | ||
3514 | /* trade a vfsmount reference for active sb one */ | |
3515 | s = path.mnt->mnt_sb; | |
3516 | atomic_inc(&s->s_active); | |
3517 | mntput(path.mnt); | |
3518 | /* lock the sucker */ | |
3519 | down_write(&s->s_umount); | |
3520 | /* ... and return the root of (sub)tree on it */ | |
3521 | return path.dentry; | |
3522 | } | |
3523 | EXPORT_SYMBOL(mount_subtree); | |
3524 | ||
3525 | SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, | |
3526 | char __user *, type, unsigned long, flags, void __user *, data) | |
3527 | { | |
3528 | int ret; | |
3529 | char *kernel_type; | |
3530 | char *kernel_dev; | |
3531 | void *options; | |
3532 | ||
3533 | kernel_type = copy_mount_string(type); | |
3534 | ret = PTR_ERR(kernel_type); | |
3535 | if (IS_ERR(kernel_type)) | |
3536 | goto out_type; | |
3537 | ||
3538 | kernel_dev = copy_mount_string(dev_name); | |
3539 | ret = PTR_ERR(kernel_dev); | |
3540 | if (IS_ERR(kernel_dev)) | |
3541 | goto out_dev; | |
3542 | ||
3543 | options = copy_mount_options(data); | |
3544 | ret = PTR_ERR(options); | |
3545 | if (IS_ERR(options)) | |
3546 | goto out_data; | |
3547 | ||
3548 | ret = do_mount(kernel_dev, dir_name, kernel_type, flags, options); | |
3549 | ||
3550 | kfree(options); | |
3551 | out_data: | |
3552 | kfree(kernel_dev); | |
3553 | out_dev: | |
3554 | kfree(kernel_type); | |
3555 | out_type: | |
3556 | return ret; | |
3557 | } | |
3558 | ||
3559 | #define FSMOUNT_VALID_FLAGS \ | |
3560 | (MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \ | |
3561 | MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME | \ | |
3562 | MOUNT_ATTR_NOSYMFOLLOW) | |
3563 | ||
3564 | #define MOUNT_SETATTR_VALID_FLAGS (FSMOUNT_VALID_FLAGS | MOUNT_ATTR_IDMAP) | |
3565 | ||
3566 | #define MOUNT_SETATTR_PROPAGATION_FLAGS \ | |
3567 | (MS_UNBINDABLE | MS_PRIVATE | MS_SLAVE | MS_SHARED) | |
3568 | ||
3569 | static unsigned int attr_flags_to_mnt_flags(u64 attr_flags) | |
3570 | { | |
3571 | unsigned int mnt_flags = 0; | |
3572 | ||
3573 | if (attr_flags & MOUNT_ATTR_RDONLY) | |
3574 | mnt_flags |= MNT_READONLY; | |
3575 | if (attr_flags & MOUNT_ATTR_NOSUID) | |
3576 | mnt_flags |= MNT_NOSUID; | |
3577 | if (attr_flags & MOUNT_ATTR_NODEV) | |
3578 | mnt_flags |= MNT_NODEV; | |
3579 | if (attr_flags & MOUNT_ATTR_NOEXEC) | |
3580 | mnt_flags |= MNT_NOEXEC; | |
3581 | if (attr_flags & MOUNT_ATTR_NODIRATIME) | |
3582 | mnt_flags |= MNT_NODIRATIME; | |
3583 | if (attr_flags & MOUNT_ATTR_NOSYMFOLLOW) | |
3584 | mnt_flags |= MNT_NOSYMFOLLOW; | |
3585 | ||
3586 | return mnt_flags; | |
3587 | } | |
3588 | ||
3589 | /* | |
3590 | * Create a kernel mount representation for a new, prepared superblock | |
3591 | * (specified by fs_fd) and attach to an open_tree-like file descriptor. | |
3592 | */ | |
3593 | SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags, | |
3594 | unsigned int, attr_flags) | |
3595 | { | |
3596 | struct mnt_namespace *ns; | |
3597 | struct fs_context *fc; | |
3598 | struct file *file; | |
3599 | struct path newmount; | |
3600 | struct mount *mnt; | |
3601 | struct fd f; | |
3602 | unsigned int mnt_flags = 0; | |
3603 | long ret; | |
3604 | ||
3605 | if (!may_mount()) | |
3606 | return -EPERM; | |
3607 | ||
3608 | if ((flags & ~(FSMOUNT_CLOEXEC)) != 0) | |
3609 | return -EINVAL; | |
3610 | ||
3611 | if (attr_flags & ~FSMOUNT_VALID_FLAGS) | |
3612 | return -EINVAL; | |
3613 | ||
3614 | mnt_flags = attr_flags_to_mnt_flags(attr_flags); | |
3615 | ||
3616 | switch (attr_flags & MOUNT_ATTR__ATIME) { | |
3617 | case MOUNT_ATTR_STRICTATIME: | |
3618 | break; | |
3619 | case MOUNT_ATTR_NOATIME: | |
3620 | mnt_flags |= MNT_NOATIME; | |
3621 | break; | |
3622 | case MOUNT_ATTR_RELATIME: | |
3623 | mnt_flags |= MNT_RELATIME; | |
3624 | break; | |
3625 | default: | |
3626 | return -EINVAL; | |
3627 | } | |
3628 | ||
3629 | f = fdget(fs_fd); | |
3630 | if (!f.file) | |
3631 | return -EBADF; | |
3632 | ||
3633 | ret = -EINVAL; | |
3634 | if (f.file->f_op != &fscontext_fops) | |
3635 | goto err_fsfd; | |
3636 | ||
3637 | fc = f.file->private_data; | |
3638 | ||
3639 | ret = mutex_lock_interruptible(&fc->uapi_mutex); | |
3640 | if (ret < 0) | |
3641 | goto err_fsfd; | |
3642 | ||
3643 | /* There must be a valid superblock or we can't mount it */ | |
3644 | ret = -EINVAL; | |
3645 | if (!fc->root) | |
3646 | goto err_unlock; | |
3647 | ||
3648 | ret = -EPERM; | |
3649 | if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) { | |
3650 | pr_warn("VFS: Mount too revealing\n"); | |
3651 | goto err_unlock; | |
3652 | } | |
3653 | ||
3654 | ret = -EBUSY; | |
3655 | if (fc->phase != FS_CONTEXT_AWAITING_MOUNT) | |
3656 | goto err_unlock; | |
3657 | ||
3658 | if (fc->sb_flags & SB_MANDLOCK) | |
3659 | warn_mandlock(); | |
3660 | ||
3661 | newmount.mnt = vfs_create_mount(fc); | |
3662 | if (IS_ERR(newmount.mnt)) { | |
3663 | ret = PTR_ERR(newmount.mnt); | |
3664 | goto err_unlock; | |
3665 | } | |
3666 | newmount.dentry = dget(fc->root); | |
3667 | newmount.mnt->mnt_flags = mnt_flags; | |
3668 | ||
3669 | /* We've done the mount bit - now move the file context into more or | |
3670 | * less the same state as if we'd done an fspick(). We don't want to | |
3671 | * do any memory allocation or anything like that at this point as we | |
3672 | * don't want to have to handle any errors incurred. | |
3673 | */ | |
3674 | vfs_clean_context(fc); | |
3675 | ||
3676 | ns = alloc_mnt_ns(current->nsproxy->mnt_ns->user_ns, true); | |
3677 | if (IS_ERR(ns)) { | |
3678 | ret = PTR_ERR(ns); | |
3679 | goto err_path; | |
3680 | } | |
3681 | mnt = real_mount(newmount.mnt); | |
3682 | mnt->mnt_ns = ns; | |
3683 | ns->root = mnt; | |
3684 | ns->mounts = 1; | |
3685 | list_add(&mnt->mnt_list, &ns->list); | |
3686 | mntget(newmount.mnt); | |
3687 | ||
3688 | /* Attach to an apparent O_PATH fd with a note that we need to unmount | |
3689 | * it, not just simply put it. | |
3690 | */ | |
3691 | file = dentry_open(&newmount, O_PATH, fc->cred); | |
3692 | if (IS_ERR(file)) { | |
3693 | dissolve_on_fput(newmount.mnt); | |
3694 | ret = PTR_ERR(file); | |
3695 | goto err_path; | |
3696 | } | |
3697 | file->f_mode |= FMODE_NEED_UNMOUNT; | |
3698 | ||
3699 | ret = get_unused_fd_flags((flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0); | |
3700 | if (ret >= 0) | |
3701 | fd_install(ret, file); | |
3702 | else | |
3703 | fput(file); | |
3704 | ||
3705 | err_path: | |
3706 | path_put(&newmount); | |
3707 | err_unlock: | |
3708 | mutex_unlock(&fc->uapi_mutex); | |
3709 | err_fsfd: | |
3710 | fdput(f); | |
3711 | return ret; | |
3712 | } | |
3713 | ||
3714 | /* | |
3715 | * Move a mount from one place to another. In combination with | |
3716 | * fsopen()/fsmount() this is used to install a new mount and in combination | |
3717 | * with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy | |
3718 | * a mount subtree. | |
3719 | * | |
3720 | * Note the flags value is a combination of MOVE_MOUNT_* flags. | |
3721 | */ | |
3722 | SYSCALL_DEFINE5(move_mount, | |
3723 | int, from_dfd, const char __user *, from_pathname, | |
3724 | int, to_dfd, const char __user *, to_pathname, | |
3725 | unsigned int, flags) | |
3726 | { | |
3727 | struct path from_path, to_path; | |
3728 | unsigned int lflags; | |
3729 | int ret = 0; | |
3730 | ||
3731 | if (!may_mount()) | |
3732 | return -EPERM; | |
3733 | ||
3734 | if (flags & ~MOVE_MOUNT__MASK) | |
3735 | return -EINVAL; | |
3736 | ||
3737 | /* If someone gives a pathname, they aren't permitted to move | |
3738 | * from an fd that requires unmount as we can't get at the flag | |
3739 | * to clear it afterwards. | |
3740 | */ | |
3741 | lflags = 0; | |
3742 | if (flags & MOVE_MOUNT_F_SYMLINKS) lflags |= LOOKUP_FOLLOW; | |
3743 | if (flags & MOVE_MOUNT_F_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT; | |
3744 | if (flags & MOVE_MOUNT_F_EMPTY_PATH) lflags |= LOOKUP_EMPTY; | |
3745 | ||
3746 | ret = user_path_at(from_dfd, from_pathname, lflags, &from_path); | |
3747 | if (ret < 0) | |
3748 | return ret; | |
3749 | ||
3750 | lflags = 0; | |
3751 | if (flags & MOVE_MOUNT_T_SYMLINKS) lflags |= LOOKUP_FOLLOW; | |
3752 | if (flags & MOVE_MOUNT_T_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT; | |
3753 | if (flags & MOVE_MOUNT_T_EMPTY_PATH) lflags |= LOOKUP_EMPTY; | |
3754 | ||
3755 | ret = user_path_at(to_dfd, to_pathname, lflags, &to_path); | |
3756 | if (ret < 0) | |
3757 | goto out_from; | |
3758 | ||
3759 | ret = security_move_mount(&from_path, &to_path); | |
3760 | if (ret < 0) | |
3761 | goto out_to; | |
3762 | ||
3763 | if (flags & MOVE_MOUNT_SET_GROUP) | |
3764 | ret = do_set_group(&from_path, &to_path); | |
3765 | else | |
3766 | ret = do_move_mount(&from_path, &to_path); | |
3767 | ||
3768 | out_to: | |
3769 | path_put(&to_path); | |
3770 | out_from: | |
3771 | path_put(&from_path); | |
3772 | return ret; | |
3773 | } | |
3774 | ||
3775 | /* | |
3776 | * Return true if path is reachable from root | |
3777 | * | |
3778 | * namespace_sem or mount_lock is held | |
3779 | */ | |
3780 | bool is_path_reachable(struct mount *mnt, struct dentry *dentry, | |
3781 | const struct path *root) | |
3782 | { | |
3783 | while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) { | |
3784 | dentry = mnt->mnt_mountpoint; | |
3785 | mnt = mnt->mnt_parent; | |
3786 | } | |
3787 | return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry); | |
3788 | } | |
3789 | ||
3790 | bool path_is_under(const struct path *path1, const struct path *path2) | |
3791 | { | |
3792 | bool res; | |
3793 | read_seqlock_excl(&mount_lock); | |
3794 | res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2); | |
3795 | read_sequnlock_excl(&mount_lock); | |
3796 | return res; | |
3797 | } | |
3798 | EXPORT_SYMBOL(path_is_under); | |
3799 | ||
3800 | /* | |
3801 | * pivot_root Semantics: | |
3802 | * Moves the root file system of the current process to the directory put_old, | |
3803 | * makes new_root as the new root file system of the current process, and sets | |
3804 | * root/cwd of all processes which had them on the current root to new_root. | |
3805 | * | |
3806 | * Restrictions: | |
3807 | * The new_root and put_old must be directories, and must not be on the | |
3808 | * same file system as the current process root. The put_old must be | |
3809 | * underneath new_root, i.e. adding a non-zero number of /.. to the string | |
3810 | * pointed to by put_old must yield the same directory as new_root. No other | |
3811 | * file system may be mounted on put_old. After all, new_root is a mountpoint. | |
3812 | * | |
3813 | * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. | |
3814 | * See Documentation/filesystems/ramfs-rootfs-initramfs.rst for alternatives | |
3815 | * in this situation. | |
3816 | * | |
3817 | * Notes: | |
3818 | * - we don't move root/cwd if they are not at the root (reason: if something | |
3819 | * cared enough to change them, it's probably wrong to force them elsewhere) | |
3820 | * - it's okay to pick a root that isn't the root of a file system, e.g. | |
3821 | * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, | |
3822 | * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root | |
3823 | * first. | |
3824 | */ | |
3825 | SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, | |
3826 | const char __user *, put_old) | |
3827 | { | |
3828 | struct path new, old, root; | |
3829 | struct mount *new_mnt, *root_mnt, *old_mnt, *root_parent, *ex_parent; | |
3830 | struct mountpoint *old_mp, *root_mp; | |
3831 | int error; | |
3832 | ||
3833 | if (!may_mount()) | |
3834 | return -EPERM; | |
3835 | ||
3836 | error = user_path_at(AT_FDCWD, new_root, | |
3837 | LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &new); | |
3838 | if (error) | |
3839 | goto out0; | |
3840 | ||
3841 | error = user_path_at(AT_FDCWD, put_old, | |
3842 | LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old); | |
3843 | if (error) | |
3844 | goto out1; | |
3845 | ||
3846 | error = security_sb_pivotroot(&old, &new); | |
3847 | if (error) | |
3848 | goto out2; | |
3849 | ||
3850 | get_fs_root(current->fs, &root); | |
3851 | old_mp = lock_mount(&old); | |
3852 | error = PTR_ERR(old_mp); | |
3853 | if (IS_ERR(old_mp)) | |
3854 | goto out3; | |
3855 | ||
3856 | error = -EINVAL; | |
3857 | new_mnt = real_mount(new.mnt); | |
3858 | root_mnt = real_mount(root.mnt); | |
3859 | old_mnt = real_mount(old.mnt); | |
3860 | ex_parent = new_mnt->mnt_parent; | |
3861 | root_parent = root_mnt->mnt_parent; | |
3862 | if (IS_MNT_SHARED(old_mnt) || | |
3863 | IS_MNT_SHARED(ex_parent) || | |
3864 | IS_MNT_SHARED(root_parent)) | |
3865 | goto out4; | |
3866 | if (!check_mnt(root_mnt) || !check_mnt(new_mnt)) | |
3867 | goto out4; | |
3868 | if (new_mnt->mnt.mnt_flags & MNT_LOCKED) | |
3869 | goto out4; | |
3870 | error = -ENOENT; | |
3871 | if (d_unlinked(new.dentry)) | |
3872 | goto out4; | |
3873 | error = -EBUSY; | |
3874 | if (new_mnt == root_mnt || old_mnt == root_mnt) | |
3875 | goto out4; /* loop, on the same file system */ | |
3876 | error = -EINVAL; | |
3877 | if (root.mnt->mnt_root != root.dentry) | |
3878 | goto out4; /* not a mountpoint */ | |
3879 | if (!mnt_has_parent(root_mnt)) | |
3880 | goto out4; /* not attached */ | |
3881 | if (new.mnt->mnt_root != new.dentry) | |
3882 | goto out4; /* not a mountpoint */ | |
3883 | if (!mnt_has_parent(new_mnt)) | |
3884 | goto out4; /* not attached */ | |
3885 | /* make sure we can reach put_old from new_root */ | |
3886 | if (!is_path_reachable(old_mnt, old.dentry, &new)) | |
3887 | goto out4; | |
3888 | /* make certain new is below the root */ | |
3889 | if (!is_path_reachable(new_mnt, new.dentry, &root)) | |
3890 | goto out4; | |
3891 | lock_mount_hash(); | |
3892 | umount_mnt(new_mnt); | |
3893 | root_mp = unhash_mnt(root_mnt); /* we'll need its mountpoint */ | |
3894 | if (root_mnt->mnt.mnt_flags & MNT_LOCKED) { | |
3895 | new_mnt->mnt.mnt_flags |= MNT_LOCKED; | |
3896 | root_mnt->mnt.mnt_flags &= ~MNT_LOCKED; | |
3897 | } | |
3898 | /* mount old root on put_old */ | |
3899 | attach_mnt(root_mnt, old_mnt, old_mp); | |
3900 | /* mount new_root on / */ | |
3901 | attach_mnt(new_mnt, root_parent, root_mp); | |
3902 | mnt_add_count(root_parent, -1); | |
3903 | touch_mnt_namespace(current->nsproxy->mnt_ns); | |
3904 | /* A moved mount should not expire automatically */ | |
3905 | list_del_init(&new_mnt->mnt_expire); | |
3906 | put_mountpoint(root_mp); | |
3907 | unlock_mount_hash(); | |
3908 | chroot_fs_refs(&root, &new); | |
3909 | error = 0; | |
3910 | out4: | |
3911 | unlock_mount(old_mp); | |
3912 | if (!error) | |
3913 | mntput_no_expire(ex_parent); | |
3914 | out3: | |
3915 | path_put(&root); | |
3916 | out2: | |
3917 | path_put(&old); | |
3918 | out1: | |
3919 | path_put(&new); | |
3920 | out0: | |
3921 | return error; | |
3922 | } | |
3923 | ||
3924 | static unsigned int recalc_flags(struct mount_kattr *kattr, struct mount *mnt) | |
3925 | { | |
3926 | unsigned int flags = mnt->mnt.mnt_flags; | |
3927 | ||
3928 | /* flags to clear */ | |
3929 | flags &= ~kattr->attr_clr; | |
3930 | /* flags to raise */ | |
3931 | flags |= kattr->attr_set; | |
3932 | ||
3933 | return flags; | |
3934 | } | |
3935 | ||
3936 | static int can_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt) | |
3937 | { | |
3938 | struct vfsmount *m = &mnt->mnt; | |
3939 | ||
3940 | if (!kattr->mnt_userns) | |
3941 | return 0; | |
3942 | ||
3943 | /* | |
3944 | * Once a mount has been idmapped we don't allow it to change its | |
3945 | * mapping. It makes things simpler and callers can just create | |
3946 | * another bind-mount they can idmap if they want to. | |
3947 | */ | |
3948 | if (mnt_user_ns(m) != &init_user_ns) | |
3949 | return -EPERM; | |
3950 | ||
3951 | /* The underlying filesystem doesn't support idmapped mounts yet. */ | |
3952 | if (!(m->mnt_sb->s_type->fs_flags & FS_ALLOW_IDMAP)) | |
3953 | return -EINVAL; | |
3954 | ||
3955 | /* Don't yet support filesystem mountable in user namespaces. */ | |
3956 | if (m->mnt_sb->s_user_ns != &init_user_ns) | |
3957 | return -EINVAL; | |
3958 | ||
3959 | /* We're not controlling the superblock. */ | |
3960 | if (!capable(CAP_SYS_ADMIN)) | |
3961 | return -EPERM; | |
3962 | ||
3963 | /* Mount has already been visible in the filesystem hierarchy. */ | |
3964 | if (!is_anon_ns(mnt->mnt_ns)) | |
3965 | return -EINVAL; | |
3966 | ||
3967 | return 0; | |
3968 | } | |
3969 | ||
3970 | static struct mount *mount_setattr_prepare(struct mount_kattr *kattr, | |
3971 | struct mount *mnt, int *err) | |
3972 | { | |
3973 | struct mount *m = mnt, *last = NULL; | |
3974 | ||
3975 | if (!is_mounted(&m->mnt)) { | |
3976 | *err = -EINVAL; | |
3977 | goto out; | |
3978 | } | |
3979 | ||
3980 | if (!(mnt_has_parent(m) ? check_mnt(m) : is_anon_ns(m->mnt_ns))) { | |
3981 | *err = -EINVAL; | |
3982 | goto out; | |
3983 | } | |
3984 | ||
3985 | do { | |
3986 | unsigned int flags; | |
3987 | ||
3988 | flags = recalc_flags(kattr, m); | |
3989 | if (!can_change_locked_flags(m, flags)) { | |
3990 | *err = -EPERM; | |
3991 | goto out; | |
3992 | } | |
3993 | ||
3994 | *err = can_idmap_mount(kattr, m); | |
3995 | if (*err) | |
3996 | goto out; | |
3997 | ||
3998 | last = m; | |
3999 | ||
4000 | if ((kattr->attr_set & MNT_READONLY) && | |
4001 | !(m->mnt.mnt_flags & MNT_READONLY)) { | |
4002 | *err = mnt_hold_writers(m); | |
4003 | if (*err) | |
4004 | goto out; | |
4005 | } | |
4006 | } while (kattr->recurse && (m = next_mnt(m, mnt))); | |
4007 | ||
4008 | out: | |
4009 | return last; | |
4010 | } | |
4011 | ||
4012 | static void do_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt) | |
4013 | { | |
4014 | struct user_namespace *mnt_userns; | |
4015 | ||
4016 | if (!kattr->mnt_userns) | |
4017 | return; | |
4018 | ||
4019 | mnt_userns = get_user_ns(kattr->mnt_userns); | |
4020 | /* Pairs with smp_load_acquire() in mnt_user_ns(). */ | |
4021 | smp_store_release(&mnt->mnt.mnt_userns, mnt_userns); | |
4022 | } | |
4023 | ||
4024 | static void mount_setattr_commit(struct mount_kattr *kattr, | |
4025 | struct mount *mnt, struct mount *last, | |
4026 | int err) | |
4027 | { | |
4028 | struct mount *m = mnt; | |
4029 | ||
4030 | do { | |
4031 | if (!err) { | |
4032 | unsigned int flags; | |
4033 | ||
4034 | do_idmap_mount(kattr, m); | |
4035 | flags = recalc_flags(kattr, m); | |
4036 | WRITE_ONCE(m->mnt.mnt_flags, flags); | |
4037 | } | |
4038 | ||
4039 | /* | |
4040 | * We either set MNT_READONLY above so make it visible | |
4041 | * before ~MNT_WRITE_HOLD or we failed to recursively | |
4042 | * apply mount options. | |
4043 | */ | |
4044 | if ((kattr->attr_set & MNT_READONLY) && | |
4045 | (m->mnt.mnt_flags & MNT_WRITE_HOLD)) | |
4046 | mnt_unhold_writers(m); | |
4047 | ||
4048 | if (!err && kattr->propagation) | |
4049 | change_mnt_propagation(m, kattr->propagation); | |
4050 | ||
4051 | /* | |
4052 | * On failure, only cleanup until we found the first mount | |
4053 | * we failed to handle. | |
4054 | */ | |
4055 | if (err && m == last) | |
4056 | break; | |
4057 | } while (kattr->recurse && (m = next_mnt(m, mnt))); | |
4058 | ||
4059 | if (!err) | |
4060 | touch_mnt_namespace(mnt->mnt_ns); | |
4061 | } | |
4062 | ||
4063 | static int do_mount_setattr(struct path *path, struct mount_kattr *kattr) | |
4064 | { | |
4065 | struct mount *mnt = real_mount(path->mnt), *last = NULL; | |
4066 | int err = 0; | |
4067 | ||
4068 | if (path->dentry != mnt->mnt.mnt_root) | |
4069 | return -EINVAL; | |
4070 | ||
4071 | if (kattr->propagation) { | |
4072 | /* | |
4073 | * Only take namespace_lock() if we're actually changing | |
4074 | * propagation. | |
4075 | */ | |
4076 | namespace_lock(); | |
4077 | if (kattr->propagation == MS_SHARED) { | |
4078 | err = invent_group_ids(mnt, kattr->recurse); | |
4079 | if (err) { | |
4080 | namespace_unlock(); | |
4081 | return err; | |
4082 | } | |
4083 | } | |
4084 | } | |
4085 | ||
4086 | lock_mount_hash(); | |
4087 | ||
4088 | /* | |
4089 | * Get the mount tree in a shape where we can change mount | |
4090 | * properties without failure. | |
4091 | */ | |
4092 | last = mount_setattr_prepare(kattr, mnt, &err); | |
4093 | if (last) /* Commit all changes or revert to the old state. */ | |
4094 | mount_setattr_commit(kattr, mnt, last, err); | |
4095 | ||
4096 | unlock_mount_hash(); | |
4097 | ||
4098 | if (kattr->propagation) { | |
4099 | namespace_unlock(); | |
4100 | if (err) | |
4101 | cleanup_group_ids(mnt, NULL); | |
4102 | } | |
4103 | ||
4104 | return err; | |
4105 | } | |
4106 | ||
4107 | static int build_mount_idmapped(const struct mount_attr *attr, size_t usize, | |
4108 | struct mount_kattr *kattr, unsigned int flags) | |
4109 | { | |
4110 | int err = 0; | |
4111 | struct ns_common *ns; | |
4112 | struct user_namespace *mnt_userns; | |
4113 | struct file *file; | |
4114 | ||
4115 | if (!((attr->attr_set | attr->attr_clr) & MOUNT_ATTR_IDMAP)) | |
4116 | return 0; | |
4117 | ||
4118 | /* | |
4119 | * We currently do not support clearing an idmapped mount. If this ever | |
4120 | * is a use-case we can revisit this but for now let's keep it simple | |
4121 | * and not allow it. | |
4122 | */ | |
4123 | if (attr->attr_clr & MOUNT_ATTR_IDMAP) | |
4124 | return -EINVAL; | |
4125 | ||
4126 | if (attr->userns_fd > INT_MAX) | |
4127 | return -EINVAL; | |
4128 | ||
4129 | file = fget(attr->userns_fd); | |
4130 | if (!file) | |
4131 | return -EBADF; | |
4132 | ||
4133 | if (!proc_ns_file(file)) { | |
4134 | err = -EINVAL; | |
4135 | goto out_fput; | |
4136 | } | |
4137 | ||
4138 | ns = get_proc_ns(file_inode(file)); | |
4139 | if (ns->ops->type != CLONE_NEWUSER) { | |
4140 | err = -EINVAL; | |
4141 | goto out_fput; | |
4142 | } | |
4143 | ||
4144 | /* | |
4145 | * The init_user_ns is used to indicate that a vfsmount is not idmapped. | |
4146 | * This is simpler than just having to treat NULL as unmapped. Users | |
4147 | * wanting to idmap a mount to init_user_ns can just use a namespace | |
4148 | * with an identity mapping. | |
4149 | */ | |
4150 | mnt_userns = container_of(ns, struct user_namespace, ns); | |
4151 | if (mnt_userns == &init_user_ns) { | |
4152 | err = -EPERM; | |
4153 | goto out_fput; | |
4154 | } | |
4155 | kattr->mnt_userns = get_user_ns(mnt_userns); | |
4156 | ||
4157 | out_fput: | |
4158 | fput(file); | |
4159 | return err; | |
4160 | } | |
4161 | ||
4162 | static int build_mount_kattr(const struct mount_attr *attr, size_t usize, | |
4163 | struct mount_kattr *kattr, unsigned int flags) | |
4164 | { | |
4165 | unsigned int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW; | |
4166 | ||
4167 | if (flags & AT_NO_AUTOMOUNT) | |
4168 | lookup_flags &= ~LOOKUP_AUTOMOUNT; | |
4169 | if (flags & AT_SYMLINK_NOFOLLOW) | |
4170 | lookup_flags &= ~LOOKUP_FOLLOW; | |
4171 | if (flags & AT_EMPTY_PATH) | |
4172 | lookup_flags |= LOOKUP_EMPTY; | |
4173 | ||
4174 | *kattr = (struct mount_kattr) { | |
4175 | .lookup_flags = lookup_flags, | |
4176 | .recurse = !!(flags & AT_RECURSIVE), | |
4177 | }; | |
4178 | ||
4179 | if (attr->propagation & ~MOUNT_SETATTR_PROPAGATION_FLAGS) | |
4180 | return -EINVAL; | |
4181 | if (hweight32(attr->propagation & MOUNT_SETATTR_PROPAGATION_FLAGS) > 1) | |
4182 | return -EINVAL; | |
4183 | kattr->propagation = attr->propagation; | |
4184 | ||
4185 | if ((attr->attr_set | attr->attr_clr) & ~MOUNT_SETATTR_VALID_FLAGS) | |
4186 | return -EINVAL; | |
4187 | ||
4188 | kattr->attr_set = attr_flags_to_mnt_flags(attr->attr_set); | |
4189 | kattr->attr_clr = attr_flags_to_mnt_flags(attr->attr_clr); | |
4190 | ||
4191 | /* | |
4192 | * Since the MOUNT_ATTR_<atime> values are an enum, not a bitmap, | |
4193 | * users wanting to transition to a different atime setting cannot | |
4194 | * simply specify the atime setting in @attr_set, but must also | |
4195 | * specify MOUNT_ATTR__ATIME in the @attr_clr field. | |
4196 | * So ensure that MOUNT_ATTR__ATIME can't be partially set in | |
4197 | * @attr_clr and that @attr_set can't have any atime bits set if | |
4198 | * MOUNT_ATTR__ATIME isn't set in @attr_clr. | |
4199 | */ | |
4200 | if (attr->attr_clr & MOUNT_ATTR__ATIME) { | |
4201 | if ((attr->attr_clr & MOUNT_ATTR__ATIME) != MOUNT_ATTR__ATIME) | |
4202 | return -EINVAL; | |
4203 | ||
4204 | /* | |
4205 | * Clear all previous time settings as they are mutually | |
4206 | * exclusive. | |
4207 | */ | |
4208 | kattr->attr_clr |= MNT_RELATIME | MNT_NOATIME; | |
4209 | switch (attr->attr_set & MOUNT_ATTR__ATIME) { | |
4210 | case MOUNT_ATTR_RELATIME: | |
4211 | kattr->attr_set |= MNT_RELATIME; | |
4212 | break; | |
4213 | case MOUNT_ATTR_NOATIME: | |
4214 | kattr->attr_set |= MNT_NOATIME; | |
4215 | break; | |
4216 | case MOUNT_ATTR_STRICTATIME: | |
4217 | break; | |
4218 | default: | |
4219 | return -EINVAL; | |
4220 | } | |
4221 | } else { | |
4222 | if (attr->attr_set & MOUNT_ATTR__ATIME) | |
4223 | return -EINVAL; | |
4224 | } | |
4225 | ||
4226 | return build_mount_idmapped(attr, usize, kattr, flags); | |
4227 | } | |
4228 | ||
4229 | static void finish_mount_kattr(struct mount_kattr *kattr) | |
4230 | { | |
4231 | put_user_ns(kattr->mnt_userns); | |
4232 | kattr->mnt_userns = NULL; | |
4233 | } | |
4234 | ||
4235 | SYSCALL_DEFINE5(mount_setattr, int, dfd, const char __user *, path, | |
4236 | unsigned int, flags, struct mount_attr __user *, uattr, | |
4237 | size_t, usize) | |
4238 | { | |
4239 | int err; | |
4240 | struct path target; | |
4241 | struct mount_attr attr; | |
4242 | struct mount_kattr kattr; | |
4243 | ||
4244 | BUILD_BUG_ON(sizeof(struct mount_attr) != MOUNT_ATTR_SIZE_VER0); | |
4245 | ||
4246 | if (flags & ~(AT_EMPTY_PATH | | |
4247 | AT_RECURSIVE | | |
4248 | AT_SYMLINK_NOFOLLOW | | |
4249 | AT_NO_AUTOMOUNT)) | |
4250 | return -EINVAL; | |
4251 | ||
4252 | if (unlikely(usize > PAGE_SIZE)) | |
4253 | return -E2BIG; | |
4254 | if (unlikely(usize < MOUNT_ATTR_SIZE_VER0)) | |
4255 | return -EINVAL; | |
4256 | ||
4257 | if (!may_mount()) | |
4258 | return -EPERM; | |
4259 | ||
4260 | err = copy_struct_from_user(&attr, sizeof(attr), uattr, usize); | |
4261 | if (err) | |
4262 | return err; | |
4263 | ||
4264 | /* Don't bother walking through the mounts if this is a nop. */ | |
4265 | if (attr.attr_set == 0 && | |
4266 | attr.attr_clr == 0 && | |
4267 | attr.propagation == 0) | |
4268 | return 0; | |
4269 | ||
4270 | err = build_mount_kattr(&attr, usize, &kattr, flags); | |
4271 | if (err) | |
4272 | return err; | |
4273 | ||
4274 | err = user_path_at(dfd, path, kattr.lookup_flags, &target); | |
4275 | if (!err) { | |
4276 | err = do_mount_setattr(&target, &kattr); | |
4277 | path_put(&target); | |
4278 | } | |
4279 | finish_mount_kattr(&kattr); | |
4280 | return err; | |
4281 | } | |
4282 | ||
4283 | static void __init init_mount_tree(void) | |
4284 | { | |
4285 | struct vfsmount *mnt; | |
4286 | struct mount *m; | |
4287 | struct mnt_namespace *ns; | |
4288 | struct path root; | |
4289 | ||
4290 | mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", NULL); | |
4291 | if (IS_ERR(mnt)) | |
4292 | panic("Can't create rootfs"); | |
4293 | ||
4294 | ns = alloc_mnt_ns(&init_user_ns, false); | |
4295 | if (IS_ERR(ns)) | |
4296 | panic("Can't allocate initial namespace"); | |
4297 | m = real_mount(mnt); | |
4298 | m->mnt_ns = ns; | |
4299 | ns->root = m; | |
4300 | ns->mounts = 1; | |
4301 | list_add(&m->mnt_list, &ns->list); | |
4302 | init_task.nsproxy->mnt_ns = ns; | |
4303 | get_mnt_ns(ns); | |
4304 | ||
4305 | root.mnt = mnt; | |
4306 | root.dentry = mnt->mnt_root; | |
4307 | mnt->mnt_flags |= MNT_LOCKED; | |
4308 | ||
4309 | set_fs_pwd(current->fs, &root); | |
4310 | set_fs_root(current->fs, &root); | |
4311 | } | |
4312 | ||
4313 | void __init mnt_init(void) | |
4314 | { | |
4315 | int err; | |
4316 | ||
4317 | mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount), | |
4318 | 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL); | |
4319 | ||
4320 | mount_hashtable = alloc_large_system_hash("Mount-cache", | |
4321 | sizeof(struct hlist_head), | |
4322 | mhash_entries, 19, | |
4323 | HASH_ZERO, | |
4324 | &m_hash_shift, &m_hash_mask, 0, 0); | |
4325 | mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache", | |
4326 | sizeof(struct hlist_head), | |
4327 | mphash_entries, 19, | |
4328 | HASH_ZERO, | |
4329 | &mp_hash_shift, &mp_hash_mask, 0, 0); | |
4330 | ||
4331 | if (!mount_hashtable || !mountpoint_hashtable) | |
4332 | panic("Failed to allocate mount hash table\n"); | |
4333 | ||
4334 | kernfs_init(); | |
4335 | ||
4336 | err = sysfs_init(); | |
4337 | if (err) | |
4338 | printk(KERN_WARNING "%s: sysfs_init error: %d\n", | |
4339 | __func__, err); | |
4340 | fs_kobj = kobject_create_and_add("fs", NULL); | |
4341 | if (!fs_kobj) | |
4342 | printk(KERN_WARNING "%s: kobj create error\n", __func__); | |
4343 | shmem_init(); | |
4344 | init_rootfs(); | |
4345 | init_mount_tree(); | |
4346 | } | |
4347 | ||
4348 | void put_mnt_ns(struct mnt_namespace *ns) | |
4349 | { | |
4350 | if (!refcount_dec_and_test(&ns->ns.count)) | |
4351 | return; | |
4352 | drop_collected_mounts(&ns->root->mnt); | |
4353 | free_mnt_ns(ns); | |
4354 | } | |
4355 | ||
4356 | struct vfsmount *kern_mount(struct file_system_type *type) | |
4357 | { | |
4358 | struct vfsmount *mnt; | |
4359 | mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL); | |
4360 | if (!IS_ERR(mnt)) { | |
4361 | /* | |
4362 | * it is a longterm mount, don't release mnt until | |
4363 | * we unmount before file sys is unregistered | |
4364 | */ | |
4365 | real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL; | |
4366 | } | |
4367 | return mnt; | |
4368 | } | |
4369 | EXPORT_SYMBOL_GPL(kern_mount); | |
4370 | ||
4371 | void kern_unmount(struct vfsmount *mnt) | |
4372 | { | |
4373 | /* release long term mount so mount point can be released */ | |
4374 | if (!IS_ERR_OR_NULL(mnt)) { | |
4375 | real_mount(mnt)->mnt_ns = NULL; | |
4376 | synchronize_rcu(); /* yecchhh... */ | |
4377 | mntput(mnt); | |
4378 | } | |
4379 | } | |
4380 | EXPORT_SYMBOL(kern_unmount); | |
4381 | ||
4382 | void kern_unmount_array(struct vfsmount *mnt[], unsigned int num) | |
4383 | { | |
4384 | unsigned int i; | |
4385 | ||
4386 | for (i = 0; i < num; i++) | |
4387 | if (mnt[i]) | |
4388 | real_mount(mnt[i])->mnt_ns = NULL; | |
4389 | synchronize_rcu_expedited(); | |
4390 | for (i = 0; i < num; i++) | |
4391 | mntput(mnt[i]); | |
4392 | } | |
4393 | EXPORT_SYMBOL(kern_unmount_array); | |
4394 | ||
4395 | bool our_mnt(struct vfsmount *mnt) | |
4396 | { | |
4397 | return check_mnt(real_mount(mnt)); | |
4398 | } | |
4399 | ||
4400 | bool current_chrooted(void) | |
4401 | { | |
4402 | /* Does the current process have a non-standard root */ | |
4403 | struct path ns_root; | |
4404 | struct path fs_root; | |
4405 | bool chrooted; | |
4406 | ||
4407 | /* Find the namespace root */ | |
4408 | ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt; | |
4409 | ns_root.dentry = ns_root.mnt->mnt_root; | |
4410 | path_get(&ns_root); | |
4411 | while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root)) | |
4412 | ; | |
4413 | ||
4414 | get_fs_root(current->fs, &fs_root); | |
4415 | ||
4416 | chrooted = !path_equal(&fs_root, &ns_root); | |
4417 | ||
4418 | path_put(&fs_root); | |
4419 | path_put(&ns_root); | |
4420 | ||
4421 | return chrooted; | |
4422 | } | |
4423 | ||
4424 | static bool mnt_already_visible(struct mnt_namespace *ns, | |
4425 | const struct super_block *sb, | |
4426 | int *new_mnt_flags) | |
4427 | { | |
4428 | int new_flags = *new_mnt_flags; | |
4429 | struct mount *mnt; | |
4430 | bool visible = false; | |
4431 | ||
4432 | down_read(&namespace_sem); | |
4433 | lock_ns_list(ns); | |
4434 | list_for_each_entry(mnt, &ns->list, mnt_list) { | |
4435 | struct mount *child; | |
4436 | int mnt_flags; | |
4437 | ||
4438 | if (mnt_is_cursor(mnt)) | |
4439 | continue; | |
4440 | ||
4441 | if (mnt->mnt.mnt_sb->s_type != sb->s_type) | |
4442 | continue; | |
4443 | ||
4444 | /* This mount is not fully visible if it's root directory | |
4445 | * is not the root directory of the filesystem. | |
4446 | */ | |
4447 | if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root) | |
4448 | continue; | |
4449 | ||
4450 | /* A local view of the mount flags */ | |
4451 | mnt_flags = mnt->mnt.mnt_flags; | |
4452 | ||
4453 | /* Don't miss readonly hidden in the superblock flags */ | |
4454 | if (sb_rdonly(mnt->mnt.mnt_sb)) | |
4455 | mnt_flags |= MNT_LOCK_READONLY; | |
4456 | ||
4457 | /* Verify the mount flags are equal to or more permissive | |
4458 | * than the proposed new mount. | |
4459 | */ | |
4460 | if ((mnt_flags & MNT_LOCK_READONLY) && | |
4461 | !(new_flags & MNT_READONLY)) | |
4462 | continue; | |
4463 | if ((mnt_flags & MNT_LOCK_ATIME) && | |
4464 | ((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK))) | |
4465 | continue; | |
4466 | ||
4467 | /* This mount is not fully visible if there are any | |
4468 | * locked child mounts that cover anything except for | |
4469 | * empty directories. | |
4470 | */ | |
4471 | list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { | |
4472 | struct inode *inode = child->mnt_mountpoint->d_inode; | |
4473 | /* Only worry about locked mounts */ | |
4474 | if (!(child->mnt.mnt_flags & MNT_LOCKED)) | |
4475 | continue; | |
4476 | /* Is the directory permanetly empty? */ | |
4477 | if (!is_empty_dir_inode(inode)) | |
4478 | goto next; | |
4479 | } | |
4480 | /* Preserve the locked attributes */ | |
4481 | *new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \ | |
4482 | MNT_LOCK_ATIME); | |
4483 | visible = true; | |
4484 | goto found; | |
4485 | next: ; | |
4486 | } | |
4487 | found: | |
4488 | unlock_ns_list(ns); | |
4489 | up_read(&namespace_sem); | |
4490 | return visible; | |
4491 | } | |
4492 | ||
4493 | static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags) | |
4494 | { | |
4495 | const unsigned long required_iflags = SB_I_NOEXEC | SB_I_NODEV; | |
4496 | struct mnt_namespace *ns = current->nsproxy->mnt_ns; | |
4497 | unsigned long s_iflags; | |
4498 | ||
4499 | if (ns->user_ns == &init_user_ns) | |
4500 | return false; | |
4501 | ||
4502 | /* Can this filesystem be too revealing? */ | |
4503 | s_iflags = sb->s_iflags; | |
4504 | if (!(s_iflags & SB_I_USERNS_VISIBLE)) | |
4505 | return false; | |
4506 | ||
4507 | if ((s_iflags & required_iflags) != required_iflags) { | |
4508 | WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n", | |
4509 | required_iflags); | |
4510 | return true; | |
4511 | } | |
4512 | ||
4513 | return !mnt_already_visible(ns, sb, new_mnt_flags); | |
4514 | } | |
4515 | ||
4516 | bool mnt_may_suid(struct vfsmount *mnt) | |
4517 | { | |
4518 | /* | |
4519 | * Foreign mounts (accessed via fchdir or through /proc | |
4520 | * symlinks) are always treated as if they are nosuid. This | |
4521 | * prevents namespaces from trusting potentially unsafe | |
4522 | * suid/sgid bits, file caps, or security labels that originate | |
4523 | * in other namespaces. | |
4524 | */ | |
4525 | return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) && | |
4526 | current_in_userns(mnt->mnt_sb->s_user_ns); | |
4527 | } | |
4528 | ||
4529 | static struct ns_common *mntns_get(struct task_struct *task) | |
4530 | { | |
4531 | struct ns_common *ns = NULL; | |
4532 | struct nsproxy *nsproxy; | |
4533 | ||
4534 | task_lock(task); | |
4535 | nsproxy = task->nsproxy; | |
4536 | if (nsproxy) { | |
4537 | ns = &nsproxy->mnt_ns->ns; | |
4538 | get_mnt_ns(to_mnt_ns(ns)); | |
4539 | } | |
4540 | task_unlock(task); | |
4541 | ||
4542 | return ns; | |
4543 | } | |
4544 | ||
4545 | static void mntns_put(struct ns_common *ns) | |
4546 | { | |
4547 | put_mnt_ns(to_mnt_ns(ns)); | |
4548 | } | |
4549 | ||
4550 | static int mntns_install(struct nsset *nsset, struct ns_common *ns) | |
4551 | { | |
4552 | struct nsproxy *nsproxy = nsset->nsproxy; | |
4553 | struct fs_struct *fs = nsset->fs; | |
4554 | struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns; | |
4555 | struct user_namespace *user_ns = nsset->cred->user_ns; | |
4556 | struct path root; | |
4557 | int err; | |
4558 | ||
4559 | if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) || | |
4560 | !ns_capable(user_ns, CAP_SYS_CHROOT) || | |
4561 | !ns_capable(user_ns, CAP_SYS_ADMIN)) | |
4562 | return -EPERM; | |
4563 | ||
4564 | if (is_anon_ns(mnt_ns)) | |
4565 | return -EINVAL; | |
4566 | ||
4567 | if (fs->users != 1) | |
4568 | return -EINVAL; | |
4569 | ||
4570 | get_mnt_ns(mnt_ns); | |
4571 | old_mnt_ns = nsproxy->mnt_ns; | |
4572 | nsproxy->mnt_ns = mnt_ns; | |
4573 | ||
4574 | /* Find the root */ | |
4575 | err = vfs_path_lookup(mnt_ns->root->mnt.mnt_root, &mnt_ns->root->mnt, | |
4576 | "/", LOOKUP_DOWN, &root); | |
4577 | if (err) { | |
4578 | /* revert to old namespace */ | |
4579 | nsproxy->mnt_ns = old_mnt_ns; | |
4580 | put_mnt_ns(mnt_ns); | |
4581 | return err; | |
4582 | } | |
4583 | ||
4584 | put_mnt_ns(old_mnt_ns); | |
4585 | ||
4586 | /* Update the pwd and root */ | |
4587 | set_fs_pwd(fs, &root); | |
4588 | set_fs_root(fs, &root); | |
4589 | ||
4590 | path_put(&root); | |
4591 | return 0; | |
4592 | } | |
4593 | ||
4594 | static struct user_namespace *mntns_owner(struct ns_common *ns) | |
4595 | { | |
4596 | return to_mnt_ns(ns)->user_ns; | |
4597 | } | |
4598 | ||
4599 | const struct proc_ns_operations mntns_operations = { | |
4600 | .name = "mnt", | |
4601 | .type = CLONE_NEWNS, | |
4602 | .get = mntns_get, | |
4603 | .put = mntns_put, | |
4604 | .install = mntns_install, | |
4605 | .owner = mntns_owner, | |
4606 | }; |