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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/task_work.h>
29#include <linux/sched/task.h>
30#include <uapi/linux/mount.h>
31#include <linux/fs_context.h>
32#include <linux/shmem_fs.h>
33
34#include "pnode.h"
35#include "internal.h"
36
37/* Maximum number of mounts in a mount namespace */
38unsigned int sysctl_mount_max __read_mostly = 100000;
39
40static unsigned int m_hash_mask __read_mostly;
41static unsigned int m_hash_shift __read_mostly;
42static unsigned int mp_hash_mask __read_mostly;
43static unsigned int mp_hash_shift __read_mostly;
44
45static __initdata unsigned long mhash_entries;
46static int __init set_mhash_entries(char *str)
47{
48 if (!str)
49 return 0;
50 mhash_entries = simple_strtoul(str, &str, 0);
51 return 1;
52}
53__setup("mhash_entries=", set_mhash_entries);
54
55static __initdata unsigned long mphash_entries;
56static int __init set_mphash_entries(char *str)
57{
58 if (!str)
59 return 0;
60 mphash_entries = simple_strtoul(str, &str, 0);
61 return 1;
62}
63__setup("mphash_entries=", set_mphash_entries);
64
65static u64 event;
66static DEFINE_IDA(mnt_id_ida);
67static DEFINE_IDA(mnt_group_ida);
68
69static struct hlist_head *mount_hashtable __read_mostly;
70static struct hlist_head *mountpoint_hashtable __read_mostly;
71static struct kmem_cache *mnt_cache __read_mostly;
72static DECLARE_RWSEM(namespace_sem);
73static HLIST_HEAD(unmounted); /* protected by namespace_sem */
74static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */
75
76/* /sys/fs */
77struct kobject *fs_kobj;
78EXPORT_SYMBOL_GPL(fs_kobj);
79
80/*
81 * vfsmount lock may be taken for read to prevent changes to the
82 * vfsmount hash, ie. during mountpoint lookups or walking back
83 * up the tree.
84 *
85 * It should be taken for write in all cases where the vfsmount
86 * tree or hash is modified or when a vfsmount structure is modified.
87 */
88__cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock);
89
90static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry)
91{
92 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
93 tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
94 tmp = tmp + (tmp >> m_hash_shift);
95 return &mount_hashtable[tmp & m_hash_mask];
96}
97
98static inline struct hlist_head *mp_hash(struct dentry *dentry)
99{
100 unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES);
101 tmp = tmp + (tmp >> mp_hash_shift);
102 return &mountpoint_hashtable[tmp & mp_hash_mask];
103}
104
105static int mnt_alloc_id(struct mount *mnt)
106{
107 int res = ida_alloc(&mnt_id_ida, GFP_KERNEL);
108
109 if (res < 0)
110 return res;
111 mnt->mnt_id = res;
112 return 0;
113}
114
115static void mnt_free_id(struct mount *mnt)
116{
117 ida_free(&mnt_id_ida, mnt->mnt_id);
118}
119
120/*
121 * Allocate a new peer group ID
122 */
123static int mnt_alloc_group_id(struct mount *mnt)
124{
125 int res = ida_alloc_min(&mnt_group_ida, 1, GFP_KERNEL);
126
127 if (res < 0)
128 return res;
129 mnt->mnt_group_id = res;
130 return 0;
131}
132
133/*
134 * Release a peer group ID
135 */
136void mnt_release_group_id(struct mount *mnt)
137{
138 ida_free(&mnt_group_ida, mnt->mnt_group_id);
139 mnt->mnt_group_id = 0;
140}
141
142/*
143 * vfsmount lock must be held for read
144 */
145static inline void mnt_add_count(struct mount *mnt, int n)
146{
147#ifdef CONFIG_SMP
148 this_cpu_add(mnt->mnt_pcp->mnt_count, n);
149#else
150 preempt_disable();
151 mnt->mnt_count += n;
152 preempt_enable();
153#endif
154}
155
156/*
157 * vfsmount lock must be held for write
158 */
159unsigned int mnt_get_count(struct mount *mnt)
160{
161#ifdef CONFIG_SMP
162 unsigned int count = 0;
163 int cpu;
164
165 for_each_possible_cpu(cpu) {
166 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
167 }
168
169 return count;
170#else
171 return mnt->mnt_count;
172#endif
173}
174
175static struct mount *alloc_vfsmnt(const char *name)
176{
177 struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
178 if (mnt) {
179 int err;
180
181 err = mnt_alloc_id(mnt);
182 if (err)
183 goto out_free_cache;
184
185 if (name) {
186 mnt->mnt_devname = kstrdup_const(name, GFP_KERNEL);
187 if (!mnt->mnt_devname)
188 goto out_free_id;
189 }
190
191#ifdef CONFIG_SMP
192 mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
193 if (!mnt->mnt_pcp)
194 goto out_free_devname;
195
196 this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
197#else
198 mnt->mnt_count = 1;
199 mnt->mnt_writers = 0;
200#endif
201
202 INIT_HLIST_NODE(&mnt->mnt_hash);
203 INIT_LIST_HEAD(&mnt->mnt_child);
204 INIT_LIST_HEAD(&mnt->mnt_mounts);
205 INIT_LIST_HEAD(&mnt->mnt_list);
206 INIT_LIST_HEAD(&mnt->mnt_expire);
207 INIT_LIST_HEAD(&mnt->mnt_share);
208 INIT_LIST_HEAD(&mnt->mnt_slave_list);
209 INIT_LIST_HEAD(&mnt->mnt_slave);
210 INIT_HLIST_NODE(&mnt->mnt_mp_list);
211 INIT_LIST_HEAD(&mnt->mnt_umounting);
212 INIT_HLIST_HEAD(&mnt->mnt_stuck_children);
213 }
214 return mnt;
215
216#ifdef CONFIG_SMP
217out_free_devname:
218 kfree_const(mnt->mnt_devname);
219#endif
220out_free_id:
221 mnt_free_id(mnt);
222out_free_cache:
223 kmem_cache_free(mnt_cache, mnt);
224 return NULL;
225}
226
227/*
228 * Most r/o checks on a fs are for operations that take
229 * discrete amounts of time, like a write() or unlink().
230 * We must keep track of when those operations start
231 * (for permission checks) and when they end, so that
232 * we can determine when writes are able to occur to
233 * a filesystem.
234 */
235/*
236 * __mnt_is_readonly: check whether a mount is read-only
237 * @mnt: the mount to check for its write status
238 *
239 * This shouldn't be used directly ouside of the VFS.
240 * It does not guarantee that the filesystem will stay
241 * r/w, just that it is right *now*. This can not and
242 * should not be used in place of IS_RDONLY(inode).
243 * mnt_want/drop_write() will _keep_ the filesystem
244 * r/w.
245 */
246bool __mnt_is_readonly(struct vfsmount *mnt)
247{
248 return (mnt->mnt_flags & MNT_READONLY) || sb_rdonly(mnt->mnt_sb);
249}
250EXPORT_SYMBOL_GPL(__mnt_is_readonly);
251
252static inline void mnt_inc_writers(struct mount *mnt)
253{
254#ifdef CONFIG_SMP
255 this_cpu_inc(mnt->mnt_pcp->mnt_writers);
256#else
257 mnt->mnt_writers++;
258#endif
259}
260
261static inline void mnt_dec_writers(struct mount *mnt)
262{
263#ifdef CONFIG_SMP
264 this_cpu_dec(mnt->mnt_pcp->mnt_writers);
265#else
266 mnt->mnt_writers--;
267#endif
268}
269
270static unsigned int mnt_get_writers(struct mount *mnt)
271{
272#ifdef CONFIG_SMP
273 unsigned int count = 0;
274 int cpu;
275
276 for_each_possible_cpu(cpu) {
277 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
278 }
279
280 return count;
281#else
282 return mnt->mnt_writers;
283#endif
284}
285
286static int mnt_is_readonly(struct vfsmount *mnt)
287{
288 if (mnt->mnt_sb->s_readonly_remount)
289 return 1;
290 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
291 smp_rmb();
292 return __mnt_is_readonly(mnt);
293}
294
295/*
296 * Most r/o & frozen checks on a fs are for operations that take discrete
297 * amounts of time, like a write() or unlink(). We must keep track of when
298 * those operations start (for permission checks) and when they end, so that we
299 * can determine when writes are able to occur to a filesystem.
300 */
301/**
302 * __mnt_want_write - get write access to a mount without freeze protection
303 * @m: the mount on which to take a write
304 *
305 * This tells the low-level filesystem that a write is about to be performed to
306 * it, and makes sure that writes are allowed (mnt it read-write) before
307 * returning success. This operation does not protect against filesystem being
308 * frozen. When the write operation is finished, __mnt_drop_write() must be
309 * called. This is effectively a refcount.
310 */
311int __mnt_want_write(struct vfsmount *m)
312{
313 struct mount *mnt = real_mount(m);
314 int ret = 0;
315
316 preempt_disable();
317 mnt_inc_writers(mnt);
318 /*
319 * The store to mnt_inc_writers must be visible before we pass
320 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
321 * incremented count after it has set MNT_WRITE_HOLD.
322 */
323 smp_mb();
324 while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
325 cpu_relax();
326 /*
327 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
328 * be set to match its requirements. So we must not load that until
329 * MNT_WRITE_HOLD is cleared.
330 */
331 smp_rmb();
332 if (mnt_is_readonly(m)) {
333 mnt_dec_writers(mnt);
334 ret = -EROFS;
335 }
336 preempt_enable();
337
338 return ret;
339}
340
341/**
342 * mnt_want_write - get write access to a mount
343 * @m: the mount on which to take a write
344 *
345 * This tells the low-level filesystem that a write is about to be performed to
346 * it, and makes sure that writes are allowed (mount is read-write, filesystem
347 * is not frozen) before returning success. When the write operation is
348 * finished, mnt_drop_write() must be called. This is effectively a refcount.
349 */
350int mnt_want_write(struct vfsmount *m)
351{
352 int ret;
353
354 sb_start_write(m->mnt_sb);
355 ret = __mnt_want_write(m);
356 if (ret)
357 sb_end_write(m->mnt_sb);
358 return ret;
359}
360EXPORT_SYMBOL_GPL(mnt_want_write);
361
362/**
363 * mnt_clone_write - get write access to a mount
364 * @mnt: the mount on which to take a write
365 *
366 * This is effectively like mnt_want_write, except
367 * it must only be used to take an extra write reference
368 * on a mountpoint that we already know has a write reference
369 * on it. This allows some optimisation.
370 *
371 * After finished, mnt_drop_write must be called as usual to
372 * drop the reference.
373 */
374int mnt_clone_write(struct vfsmount *mnt)
375{
376 /* superblock may be r/o */
377 if (__mnt_is_readonly(mnt))
378 return -EROFS;
379 preempt_disable();
380 mnt_inc_writers(real_mount(mnt));
381 preempt_enable();
382 return 0;
383}
384EXPORT_SYMBOL_GPL(mnt_clone_write);
385
386/**
387 * __mnt_want_write_file - get write access to a file's mount
388 * @file: the file who's mount on which to take a write
389 *
390 * This is like __mnt_want_write, but it takes a file and can
391 * do some optimisations if the file is open for write already
392 */
393int __mnt_want_write_file(struct file *file)
394{
395 if (!(file->f_mode & FMODE_WRITER))
396 return __mnt_want_write(file->f_path.mnt);
397 else
398 return mnt_clone_write(file->f_path.mnt);
399}
400
401/**
402 * mnt_want_write_file - get write access to a file's mount
403 * @file: the file who's mount on which to take a write
404 *
405 * This is like mnt_want_write, but it takes a file and can
406 * do some optimisations if the file is open for write already
407 */
408int mnt_want_write_file(struct file *file)
409{
410 int ret;
411
412 sb_start_write(file_inode(file)->i_sb);
413 ret = __mnt_want_write_file(file);
414 if (ret)
415 sb_end_write(file_inode(file)->i_sb);
416 return ret;
417}
418EXPORT_SYMBOL_GPL(mnt_want_write_file);
419
420/**
421 * __mnt_drop_write - give up write access to a mount
422 * @mnt: the mount on which to give up write access
423 *
424 * Tells the low-level filesystem that we are done
425 * performing writes to it. Must be matched with
426 * __mnt_want_write() call above.
427 */
428void __mnt_drop_write(struct vfsmount *mnt)
429{
430 preempt_disable();
431 mnt_dec_writers(real_mount(mnt));
432 preempt_enable();
433}
434
435/**
436 * mnt_drop_write - give up write access to a mount
437 * @mnt: the mount on which to give up write access
438 *
439 * Tells the low-level filesystem that we are done performing writes to it and
440 * also allows filesystem to be frozen again. Must be matched with
441 * mnt_want_write() call above.
442 */
443void mnt_drop_write(struct vfsmount *mnt)
444{
445 __mnt_drop_write(mnt);
446 sb_end_write(mnt->mnt_sb);
447}
448EXPORT_SYMBOL_GPL(mnt_drop_write);
449
450void __mnt_drop_write_file(struct file *file)
451{
452 __mnt_drop_write(file->f_path.mnt);
453}
454
455void mnt_drop_write_file(struct file *file)
456{
457 __mnt_drop_write_file(file);
458 sb_end_write(file_inode(file)->i_sb);
459}
460EXPORT_SYMBOL(mnt_drop_write_file);
461
462static int mnt_make_readonly(struct mount *mnt)
463{
464 int ret = 0;
465
466 lock_mount_hash();
467 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
468 /*
469 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
470 * should be visible before we do.
471 */
472 smp_mb();
473
474 /*
475 * With writers on hold, if this value is zero, then there are
476 * definitely no active writers (although held writers may subsequently
477 * increment the count, they'll have to wait, and decrement it after
478 * seeing MNT_READONLY).
479 *
480 * It is OK to have counter incremented on one CPU and decremented on
481 * another: the sum will add up correctly. The danger would be when we
482 * sum up each counter, if we read a counter before it is incremented,
483 * but then read another CPU's count which it has been subsequently
484 * decremented from -- we would see more decrements than we should.
485 * MNT_WRITE_HOLD protects against this scenario, because
486 * mnt_want_write first increments count, then smp_mb, then spins on
487 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
488 * we're counting up here.
489 */
490 if (mnt_get_writers(mnt) > 0)
491 ret = -EBUSY;
492 else
493 mnt->mnt.mnt_flags |= MNT_READONLY;
494 /*
495 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
496 * that become unheld will see MNT_READONLY.
497 */
498 smp_wmb();
499 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
500 unlock_mount_hash();
501 return ret;
502}
503
504static int __mnt_unmake_readonly(struct mount *mnt)
505{
506 lock_mount_hash();
507 mnt->mnt.mnt_flags &= ~MNT_READONLY;
508 unlock_mount_hash();
509 return 0;
510}
511
512int sb_prepare_remount_readonly(struct super_block *sb)
513{
514 struct mount *mnt;
515 int err = 0;
516
517 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
518 if (atomic_long_read(&sb->s_remove_count))
519 return -EBUSY;
520
521 lock_mount_hash();
522 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
523 if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
524 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
525 smp_mb();
526 if (mnt_get_writers(mnt) > 0) {
527 err = -EBUSY;
528 break;
529 }
530 }
531 }
532 if (!err && atomic_long_read(&sb->s_remove_count))
533 err = -EBUSY;
534
535 if (!err) {
536 sb->s_readonly_remount = 1;
537 smp_wmb();
538 }
539 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
540 if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
541 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
542 }
543 unlock_mount_hash();
544
545 return err;
546}
547
548static void free_vfsmnt(struct mount *mnt)
549{
550 kfree_const(mnt->mnt_devname);
551#ifdef CONFIG_SMP
552 free_percpu(mnt->mnt_pcp);
553#endif
554 kmem_cache_free(mnt_cache, mnt);
555}
556
557static void delayed_free_vfsmnt(struct rcu_head *head)
558{
559 free_vfsmnt(container_of(head, struct mount, mnt_rcu));
560}
561
562/* call under rcu_read_lock */
563int __legitimize_mnt(struct vfsmount *bastard, unsigned seq)
564{
565 struct mount *mnt;
566 if (read_seqretry(&mount_lock, seq))
567 return 1;
568 if (bastard == NULL)
569 return 0;
570 mnt = real_mount(bastard);
571 mnt_add_count(mnt, 1);
572 smp_mb(); // see mntput_no_expire()
573 if (likely(!read_seqretry(&mount_lock, seq)))
574 return 0;
575 if (bastard->mnt_flags & MNT_SYNC_UMOUNT) {
576 mnt_add_count(mnt, -1);
577 return 1;
578 }
579 lock_mount_hash();
580 if (unlikely(bastard->mnt_flags & MNT_DOOMED)) {
581 mnt_add_count(mnt, -1);
582 unlock_mount_hash();
583 return 1;
584 }
585 unlock_mount_hash();
586 /* caller will mntput() */
587 return -1;
588}
589
590/* call under rcu_read_lock */
591bool legitimize_mnt(struct vfsmount *bastard, unsigned seq)
592{
593 int res = __legitimize_mnt(bastard, seq);
594 if (likely(!res))
595 return true;
596 if (unlikely(res < 0)) {
597 rcu_read_unlock();
598 mntput(bastard);
599 rcu_read_lock();
600 }
601 return false;
602}
603
604/*
605 * find the first mount at @dentry on vfsmount @mnt.
606 * call under rcu_read_lock()
607 */
608struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
609{
610 struct hlist_head *head = m_hash(mnt, dentry);
611 struct mount *p;
612
613 hlist_for_each_entry_rcu(p, head, mnt_hash)
614 if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
615 return p;
616 return NULL;
617}
618
619/*
620 * lookup_mnt - Return the first child mount mounted at path
621 *
622 * "First" means first mounted chronologically. If you create the
623 * following mounts:
624 *
625 * mount /dev/sda1 /mnt
626 * mount /dev/sda2 /mnt
627 * mount /dev/sda3 /mnt
628 *
629 * Then lookup_mnt() on the base /mnt dentry in the root mount will
630 * return successively the root dentry and vfsmount of /dev/sda1, then
631 * /dev/sda2, then /dev/sda3, then NULL.
632 *
633 * lookup_mnt takes a reference to the found vfsmount.
634 */
635struct vfsmount *lookup_mnt(const struct path *path)
636{
637 struct mount *child_mnt;
638 struct vfsmount *m;
639 unsigned seq;
640
641 rcu_read_lock();
642 do {
643 seq = read_seqbegin(&mount_lock);
644 child_mnt = __lookup_mnt(path->mnt, path->dentry);
645 m = child_mnt ? &child_mnt->mnt : NULL;
646 } while (!legitimize_mnt(m, seq));
647 rcu_read_unlock();
648 return m;
649}
650
651/*
652 * __is_local_mountpoint - Test to see if dentry is a mountpoint in the
653 * current mount namespace.
654 *
655 * The common case is dentries are not mountpoints at all and that
656 * test is handled inline. For the slow case when we are actually
657 * dealing with a mountpoint of some kind, walk through all of the
658 * mounts in the current mount namespace and test to see if the dentry
659 * is a mountpoint.
660 *
661 * The mount_hashtable is not usable in the context because we
662 * need to identify all mounts that may be in the current mount
663 * namespace not just a mount that happens to have some specified
664 * parent mount.
665 */
666bool __is_local_mountpoint(struct dentry *dentry)
667{
668 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
669 struct mount *mnt;
670 bool is_covered = false;
671
672 if (!d_mountpoint(dentry))
673 goto out;
674
675 down_read(&namespace_sem);
676 list_for_each_entry(mnt, &ns->list, mnt_list) {
677 is_covered = (mnt->mnt_mountpoint == dentry);
678 if (is_covered)
679 break;
680 }
681 up_read(&namespace_sem);
682out:
683 return is_covered;
684}
685
686static struct mountpoint *lookup_mountpoint(struct dentry *dentry)
687{
688 struct hlist_head *chain = mp_hash(dentry);
689 struct mountpoint *mp;
690
691 hlist_for_each_entry(mp, chain, m_hash) {
692 if (mp->m_dentry == dentry) {
693 mp->m_count++;
694 return mp;
695 }
696 }
697 return NULL;
698}
699
700static struct mountpoint *get_mountpoint(struct dentry *dentry)
701{
702 struct mountpoint *mp, *new = NULL;
703 int ret;
704
705 if (d_mountpoint(dentry)) {
706 /* might be worth a WARN_ON() */
707 if (d_unlinked(dentry))
708 return ERR_PTR(-ENOENT);
709mountpoint:
710 read_seqlock_excl(&mount_lock);
711 mp = lookup_mountpoint(dentry);
712 read_sequnlock_excl(&mount_lock);
713 if (mp)
714 goto done;
715 }
716
717 if (!new)
718 new = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
719 if (!new)
720 return ERR_PTR(-ENOMEM);
721
722
723 /* Exactly one processes may set d_mounted */
724 ret = d_set_mounted(dentry);
725
726 /* Someone else set d_mounted? */
727 if (ret == -EBUSY)
728 goto mountpoint;
729
730 /* The dentry is not available as a mountpoint? */
731 mp = ERR_PTR(ret);
732 if (ret)
733 goto done;
734
735 /* Add the new mountpoint to the hash table */
736 read_seqlock_excl(&mount_lock);
737 new->m_dentry = dget(dentry);
738 new->m_count = 1;
739 hlist_add_head(&new->m_hash, mp_hash(dentry));
740 INIT_HLIST_HEAD(&new->m_list);
741 read_sequnlock_excl(&mount_lock);
742
743 mp = new;
744 new = NULL;
745done:
746 kfree(new);
747 return mp;
748}
749
750/*
751 * vfsmount lock must be held. Additionally, the caller is responsible
752 * for serializing calls for given disposal list.
753 */
754static void __put_mountpoint(struct mountpoint *mp, struct list_head *list)
755{
756 if (!--mp->m_count) {
757 struct dentry *dentry = mp->m_dentry;
758 BUG_ON(!hlist_empty(&mp->m_list));
759 spin_lock(&dentry->d_lock);
760 dentry->d_flags &= ~DCACHE_MOUNTED;
761 spin_unlock(&dentry->d_lock);
762 dput_to_list(dentry, list);
763 hlist_del(&mp->m_hash);
764 kfree(mp);
765 }
766}
767
768/* called with namespace_lock and vfsmount lock */
769static void put_mountpoint(struct mountpoint *mp)
770{
771 __put_mountpoint(mp, &ex_mountpoints);
772}
773
774static inline int check_mnt(struct mount *mnt)
775{
776 return mnt->mnt_ns == current->nsproxy->mnt_ns;
777}
778
779/*
780 * vfsmount lock must be held for write
781 */
782static void touch_mnt_namespace(struct mnt_namespace *ns)
783{
784 if (ns) {
785 ns->event = ++event;
786 wake_up_interruptible(&ns->poll);
787 }
788}
789
790/*
791 * vfsmount lock must be held for write
792 */
793static void __touch_mnt_namespace(struct mnt_namespace *ns)
794{
795 if (ns && ns->event != event) {
796 ns->event = event;
797 wake_up_interruptible(&ns->poll);
798 }
799}
800
801/*
802 * vfsmount lock must be held for write
803 */
804static struct mountpoint *unhash_mnt(struct mount *mnt)
805{
806 struct mountpoint *mp;
807 mnt->mnt_parent = mnt;
808 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
809 list_del_init(&mnt->mnt_child);
810 hlist_del_init_rcu(&mnt->mnt_hash);
811 hlist_del_init(&mnt->mnt_mp_list);
812 mp = mnt->mnt_mp;
813 mnt->mnt_mp = NULL;
814 return mp;
815}
816
817/*
818 * vfsmount lock must be held for write
819 */
820static void umount_mnt(struct mount *mnt)
821{
822 put_mountpoint(unhash_mnt(mnt));
823}
824
825/*
826 * vfsmount lock must be held for write
827 */
828void mnt_set_mountpoint(struct mount *mnt,
829 struct mountpoint *mp,
830 struct mount *child_mnt)
831{
832 mp->m_count++;
833 mnt_add_count(mnt, 1); /* essentially, that's mntget */
834 child_mnt->mnt_mountpoint = mp->m_dentry;
835 child_mnt->mnt_parent = mnt;
836 child_mnt->mnt_mp = mp;
837 hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list);
838}
839
840static void __attach_mnt(struct mount *mnt, struct mount *parent)
841{
842 hlist_add_head_rcu(&mnt->mnt_hash,
843 m_hash(&parent->mnt, mnt->mnt_mountpoint));
844 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
845}
846
847/*
848 * vfsmount lock must be held for write
849 */
850static void attach_mnt(struct mount *mnt,
851 struct mount *parent,
852 struct mountpoint *mp)
853{
854 mnt_set_mountpoint(parent, mp, mnt);
855 __attach_mnt(mnt, parent);
856}
857
858void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp, struct mount *mnt)
859{
860 struct mountpoint *old_mp = mnt->mnt_mp;
861 struct mount *old_parent = mnt->mnt_parent;
862
863 list_del_init(&mnt->mnt_child);
864 hlist_del_init(&mnt->mnt_mp_list);
865 hlist_del_init_rcu(&mnt->mnt_hash);
866
867 attach_mnt(mnt, parent, mp);
868
869 put_mountpoint(old_mp);
870 mnt_add_count(old_parent, -1);
871}
872
873/*
874 * vfsmount lock must be held for write
875 */
876static void commit_tree(struct mount *mnt)
877{
878 struct mount *parent = mnt->mnt_parent;
879 struct mount *m;
880 LIST_HEAD(head);
881 struct mnt_namespace *n = parent->mnt_ns;
882
883 BUG_ON(parent == mnt);
884
885 list_add_tail(&head, &mnt->mnt_list);
886 list_for_each_entry(m, &head, mnt_list)
887 m->mnt_ns = n;
888
889 list_splice(&head, n->list.prev);
890
891 n->mounts += n->pending_mounts;
892 n->pending_mounts = 0;
893
894 __attach_mnt(mnt, parent);
895 touch_mnt_namespace(n);
896}
897
898static struct mount *next_mnt(struct mount *p, struct mount *root)
899{
900 struct list_head *next = p->mnt_mounts.next;
901 if (next == &p->mnt_mounts) {
902 while (1) {
903 if (p == root)
904 return NULL;
905 next = p->mnt_child.next;
906 if (next != &p->mnt_parent->mnt_mounts)
907 break;
908 p = p->mnt_parent;
909 }
910 }
911 return list_entry(next, struct mount, mnt_child);
912}
913
914static struct mount *skip_mnt_tree(struct mount *p)
915{
916 struct list_head *prev = p->mnt_mounts.prev;
917 while (prev != &p->mnt_mounts) {
918 p = list_entry(prev, struct mount, mnt_child);
919 prev = p->mnt_mounts.prev;
920 }
921 return p;
922}
923
924/**
925 * vfs_create_mount - Create a mount for a configured superblock
926 * @fc: The configuration context with the superblock attached
927 *
928 * Create a mount to an already configured superblock. If necessary, the
929 * caller should invoke vfs_get_tree() before calling this.
930 *
931 * Note that this does not attach the mount to anything.
932 */
933struct vfsmount *vfs_create_mount(struct fs_context *fc)
934{
935 struct mount *mnt;
936
937 if (!fc->root)
938 return ERR_PTR(-EINVAL);
939
940 mnt = alloc_vfsmnt(fc->source ?: "none");
941 if (!mnt)
942 return ERR_PTR(-ENOMEM);
943
944 if (fc->sb_flags & SB_KERNMOUNT)
945 mnt->mnt.mnt_flags = MNT_INTERNAL;
946
947 atomic_inc(&fc->root->d_sb->s_active);
948 mnt->mnt.mnt_sb = fc->root->d_sb;
949 mnt->mnt.mnt_root = dget(fc->root);
950 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
951 mnt->mnt_parent = mnt;
952
953 lock_mount_hash();
954 list_add_tail(&mnt->mnt_instance, &mnt->mnt.mnt_sb->s_mounts);
955 unlock_mount_hash();
956 return &mnt->mnt;
957}
958EXPORT_SYMBOL(vfs_create_mount);
959
960struct vfsmount *fc_mount(struct fs_context *fc)
961{
962 int err = vfs_get_tree(fc);
963 if (!err) {
964 up_write(&fc->root->d_sb->s_umount);
965 return vfs_create_mount(fc);
966 }
967 return ERR_PTR(err);
968}
969EXPORT_SYMBOL(fc_mount);
970
971struct vfsmount *vfs_kern_mount(struct file_system_type *type,
972 int flags, const char *name,
973 void *data)
974{
975 struct fs_context *fc;
976 struct vfsmount *mnt;
977 int ret = 0;
978
979 if (!type)
980 return ERR_PTR(-EINVAL);
981
982 fc = fs_context_for_mount(type, flags);
983 if (IS_ERR(fc))
984 return ERR_CAST(fc);
985
986 if (name)
987 ret = vfs_parse_fs_string(fc, "source",
988 name, strlen(name));
989 if (!ret)
990 ret = parse_monolithic_mount_data(fc, data);
991 if (!ret)
992 mnt = fc_mount(fc);
993 else
994 mnt = ERR_PTR(ret);
995
996 put_fs_context(fc);
997 return mnt;
998}
999EXPORT_SYMBOL_GPL(vfs_kern_mount);
1000
1001struct vfsmount *
1002vfs_submount(const struct dentry *mountpoint, struct file_system_type *type,
1003 const char *name, void *data)
1004{
1005 /* Until it is worked out how to pass the user namespace
1006 * through from the parent mount to the submount don't support
1007 * unprivileged mounts with submounts.
1008 */
1009 if (mountpoint->d_sb->s_user_ns != &init_user_ns)
1010 return ERR_PTR(-EPERM);
1011
1012 return vfs_kern_mount(type, SB_SUBMOUNT, name, data);
1013}
1014EXPORT_SYMBOL_GPL(vfs_submount);
1015
1016static struct mount *clone_mnt(struct mount *old, struct dentry *root,
1017 int flag)
1018{
1019 struct super_block *sb = old->mnt.mnt_sb;
1020 struct mount *mnt;
1021 int err;
1022
1023 mnt = alloc_vfsmnt(old->mnt_devname);
1024 if (!mnt)
1025 return ERR_PTR(-ENOMEM);
1026
1027 if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
1028 mnt->mnt_group_id = 0; /* not a peer of original */
1029 else
1030 mnt->mnt_group_id = old->mnt_group_id;
1031
1032 if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
1033 err = mnt_alloc_group_id(mnt);
1034 if (err)
1035 goto out_free;
1036 }
1037
1038 mnt->mnt.mnt_flags = old->mnt.mnt_flags;
1039 mnt->mnt.mnt_flags &= ~(MNT_WRITE_HOLD|MNT_MARKED|MNT_INTERNAL);
1040
1041 atomic_inc(&sb->s_active);
1042 mnt->mnt.mnt_sb = sb;
1043 mnt->mnt.mnt_root = dget(root);
1044 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
1045 mnt->mnt_parent = mnt;
1046 lock_mount_hash();
1047 list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
1048 unlock_mount_hash();
1049
1050 if ((flag & CL_SLAVE) ||
1051 ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
1052 list_add(&mnt->mnt_slave, &old->mnt_slave_list);
1053 mnt->mnt_master = old;
1054 CLEAR_MNT_SHARED(mnt);
1055 } else if (!(flag & CL_PRIVATE)) {
1056 if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
1057 list_add(&mnt->mnt_share, &old->mnt_share);
1058 if (IS_MNT_SLAVE(old))
1059 list_add(&mnt->mnt_slave, &old->mnt_slave);
1060 mnt->mnt_master = old->mnt_master;
1061 } else {
1062 CLEAR_MNT_SHARED(mnt);
1063 }
1064 if (flag & CL_MAKE_SHARED)
1065 set_mnt_shared(mnt);
1066
1067 /* stick the duplicate mount on the same expiry list
1068 * as the original if that was on one */
1069 if (flag & CL_EXPIRE) {
1070 if (!list_empty(&old->mnt_expire))
1071 list_add(&mnt->mnt_expire, &old->mnt_expire);
1072 }
1073
1074 return mnt;
1075
1076 out_free:
1077 mnt_free_id(mnt);
1078 free_vfsmnt(mnt);
1079 return ERR_PTR(err);
1080}
1081
1082static void cleanup_mnt(struct mount *mnt)
1083{
1084 struct hlist_node *p;
1085 struct mount *m;
1086 /*
1087 * The warning here probably indicates that somebody messed
1088 * up a mnt_want/drop_write() pair. If this happens, the
1089 * filesystem was probably unable to make r/w->r/o transitions.
1090 * The locking used to deal with mnt_count decrement provides barriers,
1091 * so mnt_get_writers() below is safe.
1092 */
1093 WARN_ON(mnt_get_writers(mnt));
1094 if (unlikely(mnt->mnt_pins.first))
1095 mnt_pin_kill(mnt);
1096 hlist_for_each_entry_safe(m, p, &mnt->mnt_stuck_children, mnt_umount) {
1097 hlist_del(&m->mnt_umount);
1098 mntput(&m->mnt);
1099 }
1100 fsnotify_vfsmount_delete(&mnt->mnt);
1101 dput(mnt->mnt.mnt_root);
1102 deactivate_super(mnt->mnt.mnt_sb);
1103 mnt_free_id(mnt);
1104 call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt);
1105}
1106
1107static void __cleanup_mnt(struct rcu_head *head)
1108{
1109 cleanup_mnt(container_of(head, struct mount, mnt_rcu));
1110}
1111
1112static LLIST_HEAD(delayed_mntput_list);
1113static void delayed_mntput(struct work_struct *unused)
1114{
1115 struct llist_node *node = llist_del_all(&delayed_mntput_list);
1116 struct mount *m, *t;
1117
1118 llist_for_each_entry_safe(m, t, node, mnt_llist)
1119 cleanup_mnt(m);
1120}
1121static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput);
1122
1123static void mntput_no_expire(struct mount *mnt)
1124{
1125 LIST_HEAD(list);
1126
1127 rcu_read_lock();
1128 if (likely(READ_ONCE(mnt->mnt_ns))) {
1129 /*
1130 * Since we don't do lock_mount_hash() here,
1131 * ->mnt_ns can change under us. However, if it's
1132 * non-NULL, then there's a reference that won't
1133 * be dropped until after an RCU delay done after
1134 * turning ->mnt_ns NULL. So if we observe it
1135 * non-NULL under rcu_read_lock(), the reference
1136 * we are dropping is not the final one.
1137 */
1138 mnt_add_count(mnt, -1);
1139 rcu_read_unlock();
1140 return;
1141 }
1142 lock_mount_hash();
1143 /*
1144 * make sure that if __legitimize_mnt() has not seen us grab
1145 * mount_lock, we'll see their refcount increment here.
1146 */
1147 smp_mb();
1148 mnt_add_count(mnt, -1);
1149 if (mnt_get_count(mnt)) {
1150 rcu_read_unlock();
1151 unlock_mount_hash();
1152 return;
1153 }
1154 if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) {
1155 rcu_read_unlock();
1156 unlock_mount_hash();
1157 return;
1158 }
1159 mnt->mnt.mnt_flags |= MNT_DOOMED;
1160 rcu_read_unlock();
1161
1162 list_del(&mnt->mnt_instance);
1163
1164 if (unlikely(!list_empty(&mnt->mnt_mounts))) {
1165 struct mount *p, *tmp;
1166 list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) {
1167 __put_mountpoint(unhash_mnt(p), &list);
1168 hlist_add_head(&p->mnt_umount, &mnt->mnt_stuck_children);
1169 }
1170 }
1171 unlock_mount_hash();
1172 shrink_dentry_list(&list);
1173
1174 if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) {
1175 struct task_struct *task = current;
1176 if (likely(!(task->flags & PF_KTHREAD))) {
1177 init_task_work(&mnt->mnt_rcu, __cleanup_mnt);
1178 if (!task_work_add(task, &mnt->mnt_rcu, true))
1179 return;
1180 }
1181 if (llist_add(&mnt->mnt_llist, &delayed_mntput_list))
1182 schedule_delayed_work(&delayed_mntput_work, 1);
1183 return;
1184 }
1185 cleanup_mnt(mnt);
1186}
1187
1188void mntput(struct vfsmount *mnt)
1189{
1190 if (mnt) {
1191 struct mount *m = real_mount(mnt);
1192 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
1193 if (unlikely(m->mnt_expiry_mark))
1194 m->mnt_expiry_mark = 0;
1195 mntput_no_expire(m);
1196 }
1197}
1198EXPORT_SYMBOL(mntput);
1199
1200struct vfsmount *mntget(struct vfsmount *mnt)
1201{
1202 if (mnt)
1203 mnt_add_count(real_mount(mnt), 1);
1204 return mnt;
1205}
1206EXPORT_SYMBOL(mntget);
1207
1208/* path_is_mountpoint() - Check if path is a mount in the current
1209 * namespace.
1210 *
1211 * d_mountpoint() can only be used reliably to establish if a dentry is
1212 * not mounted in any namespace and that common case is handled inline.
1213 * d_mountpoint() isn't aware of the possibility there may be multiple
1214 * mounts using a given dentry in a different namespace. This function
1215 * checks if the passed in path is a mountpoint rather than the dentry
1216 * alone.
1217 */
1218bool path_is_mountpoint(const struct path *path)
1219{
1220 unsigned seq;
1221 bool res;
1222
1223 if (!d_mountpoint(path->dentry))
1224 return false;
1225
1226 rcu_read_lock();
1227 do {
1228 seq = read_seqbegin(&mount_lock);
1229 res = __path_is_mountpoint(path);
1230 } while (read_seqretry(&mount_lock, seq));
1231 rcu_read_unlock();
1232
1233 return res;
1234}
1235EXPORT_SYMBOL(path_is_mountpoint);
1236
1237struct vfsmount *mnt_clone_internal(const struct path *path)
1238{
1239 struct mount *p;
1240 p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE);
1241 if (IS_ERR(p))
1242 return ERR_CAST(p);
1243 p->mnt.mnt_flags |= MNT_INTERNAL;
1244 return &p->mnt;
1245}
1246
1247#ifdef CONFIG_PROC_FS
1248/* iterator; we want it to have access to namespace_sem, thus here... */
1249static void *m_start(struct seq_file *m, loff_t *pos)
1250{
1251 struct proc_mounts *p = m->private;
1252
1253 down_read(&namespace_sem);
1254 if (p->cached_event == p->ns->event) {
1255 void *v = p->cached_mount;
1256 if (*pos == p->cached_index)
1257 return v;
1258 if (*pos == p->cached_index + 1) {
1259 v = seq_list_next(v, &p->ns->list, &p->cached_index);
1260 return p->cached_mount = v;
1261 }
1262 }
1263
1264 p->cached_event = p->ns->event;
1265 p->cached_mount = seq_list_start(&p->ns->list, *pos);
1266 p->cached_index = *pos;
1267 return p->cached_mount;
1268}
1269
1270static void *m_next(struct seq_file *m, void *v, loff_t *pos)
1271{
1272 struct proc_mounts *p = m->private;
1273
1274 p->cached_mount = seq_list_next(v, &p->ns->list, pos);
1275 p->cached_index = *pos;
1276 return p->cached_mount;
1277}
1278
1279static void m_stop(struct seq_file *m, void *v)
1280{
1281 up_read(&namespace_sem);
1282}
1283
1284static int m_show(struct seq_file *m, void *v)
1285{
1286 struct proc_mounts *p = m->private;
1287 struct mount *r = list_entry(v, struct mount, mnt_list);
1288 return p->show(m, &r->mnt);
1289}
1290
1291const struct seq_operations mounts_op = {
1292 .start = m_start,
1293 .next = m_next,
1294 .stop = m_stop,
1295 .show = m_show,
1296};
1297#endif /* CONFIG_PROC_FS */
1298
1299/**
1300 * may_umount_tree - check if a mount tree is busy
1301 * @mnt: root of mount tree
1302 *
1303 * This is called to check if a tree of mounts has any
1304 * open files, pwds, chroots or sub mounts that are
1305 * busy.
1306 */
1307int may_umount_tree(struct vfsmount *m)
1308{
1309 struct mount *mnt = real_mount(m);
1310 int actual_refs = 0;
1311 int minimum_refs = 0;
1312 struct mount *p;
1313 BUG_ON(!m);
1314
1315 /* write lock needed for mnt_get_count */
1316 lock_mount_hash();
1317 for (p = mnt; p; p = next_mnt(p, mnt)) {
1318 actual_refs += mnt_get_count(p);
1319 minimum_refs += 2;
1320 }
1321 unlock_mount_hash();
1322
1323 if (actual_refs > minimum_refs)
1324 return 0;
1325
1326 return 1;
1327}
1328
1329EXPORT_SYMBOL(may_umount_tree);
1330
1331/**
1332 * may_umount - check if a mount point is busy
1333 * @mnt: root of mount
1334 *
1335 * This is called to check if a mount point has any
1336 * open files, pwds, chroots or sub mounts. If the
1337 * mount has sub mounts this will return busy
1338 * regardless of whether the sub mounts are busy.
1339 *
1340 * Doesn't take quota and stuff into account. IOW, in some cases it will
1341 * give false negatives. The main reason why it's here is that we need
1342 * a non-destructive way to look for easily umountable filesystems.
1343 */
1344int may_umount(struct vfsmount *mnt)
1345{
1346 int ret = 1;
1347 down_read(&namespace_sem);
1348 lock_mount_hash();
1349 if (propagate_mount_busy(real_mount(mnt), 2))
1350 ret = 0;
1351 unlock_mount_hash();
1352 up_read(&namespace_sem);
1353 return ret;
1354}
1355
1356EXPORT_SYMBOL(may_umount);
1357
1358static void namespace_unlock(void)
1359{
1360 struct hlist_head head;
1361 struct hlist_node *p;
1362 struct mount *m;
1363 LIST_HEAD(list);
1364
1365 hlist_move_list(&unmounted, &head);
1366 list_splice_init(&ex_mountpoints, &list);
1367
1368 up_write(&namespace_sem);
1369
1370 shrink_dentry_list(&list);
1371
1372 if (likely(hlist_empty(&head)))
1373 return;
1374
1375 synchronize_rcu_expedited();
1376
1377 hlist_for_each_entry_safe(m, p, &head, mnt_umount) {
1378 hlist_del(&m->mnt_umount);
1379 mntput(&m->mnt);
1380 }
1381}
1382
1383static inline void namespace_lock(void)
1384{
1385 down_write(&namespace_sem);
1386}
1387
1388enum umount_tree_flags {
1389 UMOUNT_SYNC = 1,
1390 UMOUNT_PROPAGATE = 2,
1391 UMOUNT_CONNECTED = 4,
1392};
1393
1394static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how)
1395{
1396 /* Leaving mounts connected is only valid for lazy umounts */
1397 if (how & UMOUNT_SYNC)
1398 return true;
1399
1400 /* A mount without a parent has nothing to be connected to */
1401 if (!mnt_has_parent(mnt))
1402 return true;
1403
1404 /* Because the reference counting rules change when mounts are
1405 * unmounted and connected, umounted mounts may not be
1406 * connected to mounted mounts.
1407 */
1408 if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT))
1409 return true;
1410
1411 /* Has it been requested that the mount remain connected? */
1412 if (how & UMOUNT_CONNECTED)
1413 return false;
1414
1415 /* Is the mount locked such that it needs to remain connected? */
1416 if (IS_MNT_LOCKED(mnt))
1417 return false;
1418
1419 /* By default disconnect the mount */
1420 return true;
1421}
1422
1423/*
1424 * mount_lock must be held
1425 * namespace_sem must be held for write
1426 */
1427static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
1428{
1429 LIST_HEAD(tmp_list);
1430 struct mount *p;
1431
1432 if (how & UMOUNT_PROPAGATE)
1433 propagate_mount_unlock(mnt);
1434
1435 /* Gather the mounts to umount */
1436 for (p = mnt; p; p = next_mnt(p, mnt)) {
1437 p->mnt.mnt_flags |= MNT_UMOUNT;
1438 list_move(&p->mnt_list, &tmp_list);
1439 }
1440
1441 /* Hide the mounts from mnt_mounts */
1442 list_for_each_entry(p, &tmp_list, mnt_list) {
1443 list_del_init(&p->mnt_child);
1444 }
1445
1446 /* Add propogated mounts to the tmp_list */
1447 if (how & UMOUNT_PROPAGATE)
1448 propagate_umount(&tmp_list);
1449
1450 while (!list_empty(&tmp_list)) {
1451 struct mnt_namespace *ns;
1452 bool disconnect;
1453 p = list_first_entry(&tmp_list, struct mount, mnt_list);
1454 list_del_init(&p->mnt_expire);
1455 list_del_init(&p->mnt_list);
1456 ns = p->mnt_ns;
1457 if (ns) {
1458 ns->mounts--;
1459 __touch_mnt_namespace(ns);
1460 }
1461 p->mnt_ns = NULL;
1462 if (how & UMOUNT_SYNC)
1463 p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
1464
1465 disconnect = disconnect_mount(p, how);
1466 if (mnt_has_parent(p)) {
1467 mnt_add_count(p->mnt_parent, -1);
1468 if (!disconnect) {
1469 /* Don't forget about p */
1470 list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts);
1471 } else {
1472 umount_mnt(p);
1473 }
1474 }
1475 change_mnt_propagation(p, MS_PRIVATE);
1476 if (disconnect)
1477 hlist_add_head(&p->mnt_umount, &unmounted);
1478 }
1479}
1480
1481static void shrink_submounts(struct mount *mnt);
1482
1483static int do_umount_root(struct super_block *sb)
1484{
1485 int ret = 0;
1486
1487 down_write(&sb->s_umount);
1488 if (!sb_rdonly(sb)) {
1489 struct fs_context *fc;
1490
1491 fc = fs_context_for_reconfigure(sb->s_root, SB_RDONLY,
1492 SB_RDONLY);
1493 if (IS_ERR(fc)) {
1494 ret = PTR_ERR(fc);
1495 } else {
1496 ret = parse_monolithic_mount_data(fc, NULL);
1497 if (!ret)
1498 ret = reconfigure_super(fc);
1499 put_fs_context(fc);
1500 }
1501 }
1502 up_write(&sb->s_umount);
1503 return ret;
1504}
1505
1506static int do_umount(struct mount *mnt, int flags)
1507{
1508 struct super_block *sb = mnt->mnt.mnt_sb;
1509 int retval;
1510
1511 retval = security_sb_umount(&mnt->mnt, flags);
1512 if (retval)
1513 return retval;
1514
1515 /*
1516 * Allow userspace to request a mountpoint be expired rather than
1517 * unmounting unconditionally. Unmount only happens if:
1518 * (1) the mark is already set (the mark is cleared by mntput())
1519 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1520 */
1521 if (flags & MNT_EXPIRE) {
1522 if (&mnt->mnt == current->fs->root.mnt ||
1523 flags & (MNT_FORCE | MNT_DETACH))
1524 return -EINVAL;
1525
1526 /*
1527 * probably don't strictly need the lock here if we examined
1528 * all race cases, but it's a slowpath.
1529 */
1530 lock_mount_hash();
1531 if (mnt_get_count(mnt) != 2) {
1532 unlock_mount_hash();
1533 return -EBUSY;
1534 }
1535 unlock_mount_hash();
1536
1537 if (!xchg(&mnt->mnt_expiry_mark, 1))
1538 return -EAGAIN;
1539 }
1540
1541 /*
1542 * If we may have to abort operations to get out of this
1543 * mount, and they will themselves hold resources we must
1544 * allow the fs to do things. In the Unix tradition of
1545 * 'Gee thats tricky lets do it in userspace' the umount_begin
1546 * might fail to complete on the first run through as other tasks
1547 * must return, and the like. Thats for the mount program to worry
1548 * about for the moment.
1549 */
1550
1551 if (flags & MNT_FORCE && sb->s_op->umount_begin) {
1552 sb->s_op->umount_begin(sb);
1553 }
1554
1555 /*
1556 * No sense to grab the lock for this test, but test itself looks
1557 * somewhat bogus. Suggestions for better replacement?
1558 * Ho-hum... In principle, we might treat that as umount + switch
1559 * to rootfs. GC would eventually take care of the old vfsmount.
1560 * Actually it makes sense, especially if rootfs would contain a
1561 * /reboot - static binary that would close all descriptors and
1562 * call reboot(9). Then init(8) could umount root and exec /reboot.
1563 */
1564 if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
1565 /*
1566 * Special case for "unmounting" root ...
1567 * we just try to remount it readonly.
1568 */
1569 if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN))
1570 return -EPERM;
1571 return do_umount_root(sb);
1572 }
1573
1574 namespace_lock();
1575 lock_mount_hash();
1576
1577 /* Recheck MNT_LOCKED with the locks held */
1578 retval = -EINVAL;
1579 if (mnt->mnt.mnt_flags & MNT_LOCKED)
1580 goto out;
1581
1582 event++;
1583 if (flags & MNT_DETACH) {
1584 if (!list_empty(&mnt->mnt_list))
1585 umount_tree(mnt, UMOUNT_PROPAGATE);
1586 retval = 0;
1587 } else {
1588 shrink_submounts(mnt);
1589 retval = -EBUSY;
1590 if (!propagate_mount_busy(mnt, 2)) {
1591 if (!list_empty(&mnt->mnt_list))
1592 umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
1593 retval = 0;
1594 }
1595 }
1596out:
1597 unlock_mount_hash();
1598 namespace_unlock();
1599 return retval;
1600}
1601
1602/*
1603 * __detach_mounts - lazily unmount all mounts on the specified dentry
1604 *
1605 * During unlink, rmdir, and d_drop it is possible to loose the path
1606 * to an existing mountpoint, and wind up leaking the mount.
1607 * detach_mounts allows lazily unmounting those mounts instead of
1608 * leaking them.
1609 *
1610 * The caller may hold dentry->d_inode->i_mutex.
1611 */
1612void __detach_mounts(struct dentry *dentry)
1613{
1614 struct mountpoint *mp;
1615 struct mount *mnt;
1616
1617 namespace_lock();
1618 lock_mount_hash();
1619 mp = lookup_mountpoint(dentry);
1620 if (!mp)
1621 goto out_unlock;
1622
1623 event++;
1624 while (!hlist_empty(&mp->m_list)) {
1625 mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list);
1626 if (mnt->mnt.mnt_flags & MNT_UMOUNT) {
1627 umount_mnt(mnt);
1628 hlist_add_head(&mnt->mnt_umount, &unmounted);
1629 }
1630 else umount_tree(mnt, UMOUNT_CONNECTED);
1631 }
1632 put_mountpoint(mp);
1633out_unlock:
1634 unlock_mount_hash();
1635 namespace_unlock();
1636}
1637
1638/*
1639 * Is the caller allowed to modify his namespace?
1640 */
1641static inline bool may_mount(void)
1642{
1643 return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
1644}
1645
1646#ifdef CONFIG_MANDATORY_FILE_LOCKING
1647static inline bool may_mandlock(void)
1648{
1649 return capable(CAP_SYS_ADMIN);
1650}
1651#else
1652static inline bool may_mandlock(void)
1653{
1654 pr_warn("VFS: \"mand\" mount option not supported");
1655 return false;
1656}
1657#endif
1658
1659/*
1660 * Now umount can handle mount points as well as block devices.
1661 * This is important for filesystems which use unnamed block devices.
1662 *
1663 * We now support a flag for forced unmount like the other 'big iron'
1664 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1665 */
1666
1667int ksys_umount(char __user *name, int flags)
1668{
1669 struct path path;
1670 struct mount *mnt;
1671 int retval;
1672 int lookup_flags = 0;
1673
1674 if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
1675 return -EINVAL;
1676
1677 if (!may_mount())
1678 return -EPERM;
1679
1680 if (!(flags & UMOUNT_NOFOLLOW))
1681 lookup_flags |= LOOKUP_FOLLOW;
1682
1683 retval = user_path_mountpoint_at(AT_FDCWD, name, lookup_flags, &path);
1684 if (retval)
1685 goto out;
1686 mnt = real_mount(path.mnt);
1687 retval = -EINVAL;
1688 if (path.dentry != path.mnt->mnt_root)
1689 goto dput_and_out;
1690 if (!check_mnt(mnt))
1691 goto dput_and_out;
1692 if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */
1693 goto dput_and_out;
1694 retval = -EPERM;
1695 if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))
1696 goto dput_and_out;
1697
1698 retval = do_umount(mnt, flags);
1699dput_and_out:
1700 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1701 dput(path.dentry);
1702 mntput_no_expire(mnt);
1703out:
1704 return retval;
1705}
1706
1707SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1708{
1709 return ksys_umount(name, flags);
1710}
1711
1712#ifdef __ARCH_WANT_SYS_OLDUMOUNT
1713
1714/*
1715 * The 2.0 compatible umount. No flags.
1716 */
1717SYSCALL_DEFINE1(oldumount, char __user *, name)
1718{
1719 return ksys_umount(name, 0);
1720}
1721
1722#endif
1723
1724static bool is_mnt_ns_file(struct dentry *dentry)
1725{
1726 /* Is this a proxy for a mount namespace? */
1727 return dentry->d_op == &ns_dentry_operations &&
1728 dentry->d_fsdata == &mntns_operations;
1729}
1730
1731struct mnt_namespace *to_mnt_ns(struct ns_common *ns)
1732{
1733 return container_of(ns, struct mnt_namespace, ns);
1734}
1735
1736static bool mnt_ns_loop(struct dentry *dentry)
1737{
1738 /* Could bind mounting the mount namespace inode cause a
1739 * mount namespace loop?
1740 */
1741 struct mnt_namespace *mnt_ns;
1742 if (!is_mnt_ns_file(dentry))
1743 return false;
1744
1745 mnt_ns = to_mnt_ns(get_proc_ns(dentry->d_inode));
1746 return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
1747}
1748
1749struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
1750 int flag)
1751{
1752 struct mount *res, *p, *q, *r, *parent;
1753
1754 if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt))
1755 return ERR_PTR(-EINVAL);
1756
1757 if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
1758 return ERR_PTR(-EINVAL);
1759
1760 res = q = clone_mnt(mnt, dentry, flag);
1761 if (IS_ERR(q))
1762 return q;
1763
1764 q->mnt_mountpoint = mnt->mnt_mountpoint;
1765
1766 p = mnt;
1767 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
1768 struct mount *s;
1769 if (!is_subdir(r->mnt_mountpoint, dentry))
1770 continue;
1771
1772 for (s = r; s; s = next_mnt(s, r)) {
1773 if (!(flag & CL_COPY_UNBINDABLE) &&
1774 IS_MNT_UNBINDABLE(s)) {
1775 if (s->mnt.mnt_flags & MNT_LOCKED) {
1776 /* Both unbindable and locked. */
1777 q = ERR_PTR(-EPERM);
1778 goto out;
1779 } else {
1780 s = skip_mnt_tree(s);
1781 continue;
1782 }
1783 }
1784 if (!(flag & CL_COPY_MNT_NS_FILE) &&
1785 is_mnt_ns_file(s->mnt.mnt_root)) {
1786 s = skip_mnt_tree(s);
1787 continue;
1788 }
1789 while (p != s->mnt_parent) {
1790 p = p->mnt_parent;
1791 q = q->mnt_parent;
1792 }
1793 p = s;
1794 parent = q;
1795 q = clone_mnt(p, p->mnt.mnt_root, flag);
1796 if (IS_ERR(q))
1797 goto out;
1798 lock_mount_hash();
1799 list_add_tail(&q->mnt_list, &res->mnt_list);
1800 attach_mnt(q, parent, p->mnt_mp);
1801 unlock_mount_hash();
1802 }
1803 }
1804 return res;
1805out:
1806 if (res) {
1807 lock_mount_hash();
1808 umount_tree(res, UMOUNT_SYNC);
1809 unlock_mount_hash();
1810 }
1811 return q;
1812}
1813
1814/* Caller should check returned pointer for errors */
1815
1816struct vfsmount *collect_mounts(const struct path *path)
1817{
1818 struct mount *tree;
1819 namespace_lock();
1820 if (!check_mnt(real_mount(path->mnt)))
1821 tree = ERR_PTR(-EINVAL);
1822 else
1823 tree = copy_tree(real_mount(path->mnt), path->dentry,
1824 CL_COPY_ALL | CL_PRIVATE);
1825 namespace_unlock();
1826 if (IS_ERR(tree))
1827 return ERR_CAST(tree);
1828 return &tree->mnt;
1829}
1830
1831static void free_mnt_ns(struct mnt_namespace *);
1832static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *, bool);
1833
1834void dissolve_on_fput(struct vfsmount *mnt)
1835{
1836 struct mnt_namespace *ns;
1837 namespace_lock();
1838 lock_mount_hash();
1839 ns = real_mount(mnt)->mnt_ns;
1840 if (ns) {
1841 if (is_anon_ns(ns))
1842 umount_tree(real_mount(mnt), UMOUNT_CONNECTED);
1843 else
1844 ns = NULL;
1845 }
1846 unlock_mount_hash();
1847 namespace_unlock();
1848 if (ns)
1849 free_mnt_ns(ns);
1850}
1851
1852void drop_collected_mounts(struct vfsmount *mnt)
1853{
1854 namespace_lock();
1855 lock_mount_hash();
1856 umount_tree(real_mount(mnt), 0);
1857 unlock_mount_hash();
1858 namespace_unlock();
1859}
1860
1861/**
1862 * clone_private_mount - create a private clone of a path
1863 *
1864 * This creates a new vfsmount, which will be the clone of @path. The new will
1865 * not be attached anywhere in the namespace and will be private (i.e. changes
1866 * to the originating mount won't be propagated into this).
1867 *
1868 * Release with mntput().
1869 */
1870struct vfsmount *clone_private_mount(const struct path *path)
1871{
1872 struct mount *old_mnt = real_mount(path->mnt);
1873 struct mount *new_mnt;
1874
1875 if (IS_MNT_UNBINDABLE(old_mnt))
1876 return ERR_PTR(-EINVAL);
1877
1878 new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE);
1879 if (IS_ERR(new_mnt))
1880 return ERR_CAST(new_mnt);
1881
1882 return &new_mnt->mnt;
1883}
1884EXPORT_SYMBOL_GPL(clone_private_mount);
1885
1886int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
1887 struct vfsmount *root)
1888{
1889 struct mount *mnt;
1890 int res = f(root, arg);
1891 if (res)
1892 return res;
1893 list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
1894 res = f(&mnt->mnt, arg);
1895 if (res)
1896 return res;
1897 }
1898 return 0;
1899}
1900
1901static void lock_mnt_tree(struct mount *mnt)
1902{
1903 struct mount *p;
1904
1905 for (p = mnt; p; p = next_mnt(p, mnt)) {
1906 int flags = p->mnt.mnt_flags;
1907 /* Don't allow unprivileged users to change mount flags */
1908 flags |= MNT_LOCK_ATIME;
1909
1910 if (flags & MNT_READONLY)
1911 flags |= MNT_LOCK_READONLY;
1912
1913 if (flags & MNT_NODEV)
1914 flags |= MNT_LOCK_NODEV;
1915
1916 if (flags & MNT_NOSUID)
1917 flags |= MNT_LOCK_NOSUID;
1918
1919 if (flags & MNT_NOEXEC)
1920 flags |= MNT_LOCK_NOEXEC;
1921 /* Don't allow unprivileged users to reveal what is under a mount */
1922 if (list_empty(&p->mnt_expire))
1923 flags |= MNT_LOCKED;
1924 p->mnt.mnt_flags = flags;
1925 }
1926}
1927
1928static void cleanup_group_ids(struct mount *mnt, struct mount *end)
1929{
1930 struct mount *p;
1931
1932 for (p = mnt; p != end; p = next_mnt(p, mnt)) {
1933 if (p->mnt_group_id && !IS_MNT_SHARED(p))
1934 mnt_release_group_id(p);
1935 }
1936}
1937
1938static int invent_group_ids(struct mount *mnt, bool recurse)
1939{
1940 struct mount *p;
1941
1942 for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
1943 if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
1944 int err = mnt_alloc_group_id(p);
1945 if (err) {
1946 cleanup_group_ids(mnt, p);
1947 return err;
1948 }
1949 }
1950 }
1951
1952 return 0;
1953}
1954
1955int count_mounts(struct mnt_namespace *ns, struct mount *mnt)
1956{
1957 unsigned int max = READ_ONCE(sysctl_mount_max);
1958 unsigned int mounts = 0, old, pending, sum;
1959 struct mount *p;
1960
1961 for (p = mnt; p; p = next_mnt(p, mnt))
1962 mounts++;
1963
1964 old = ns->mounts;
1965 pending = ns->pending_mounts;
1966 sum = old + pending;
1967 if ((old > sum) ||
1968 (pending > sum) ||
1969 (max < sum) ||
1970 (mounts > (max - sum)))
1971 return -ENOSPC;
1972
1973 ns->pending_mounts = pending + mounts;
1974 return 0;
1975}
1976
1977/*
1978 * @source_mnt : mount tree to be attached
1979 * @nd : place the mount tree @source_mnt is attached
1980 * @parent_nd : if non-null, detach the source_mnt from its parent and
1981 * store the parent mount and mountpoint dentry.
1982 * (done when source_mnt is moved)
1983 *
1984 * NOTE: in the table below explains the semantics when a source mount
1985 * of a given type is attached to a destination mount of a given type.
1986 * ---------------------------------------------------------------------------
1987 * | BIND MOUNT OPERATION |
1988 * |**************************************************************************
1989 * | source-->| shared | private | slave | unbindable |
1990 * | dest | | | | |
1991 * | | | | | | |
1992 * | v | | | | |
1993 * |**************************************************************************
1994 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1995 * | | | | | |
1996 * |non-shared| shared (+) | private | slave (*) | invalid |
1997 * ***************************************************************************
1998 * A bind operation clones the source mount and mounts the clone on the
1999 * destination mount.
2000 *
2001 * (++) the cloned mount is propagated to all the mounts in the propagation
2002 * tree of the destination mount and the cloned mount is added to
2003 * the peer group of the source mount.
2004 * (+) the cloned mount is created under the destination mount and is marked
2005 * as shared. The cloned mount is added to the peer group of the source
2006 * mount.
2007 * (+++) the mount is propagated to all the mounts in the propagation tree
2008 * of the destination mount and the cloned mount is made slave
2009 * of the same master as that of the source mount. The cloned mount
2010 * is marked as 'shared and slave'.
2011 * (*) the cloned mount is made a slave of the same master as that of the
2012 * source mount.
2013 *
2014 * ---------------------------------------------------------------------------
2015 * | MOVE MOUNT OPERATION |
2016 * |**************************************************************************
2017 * | source-->| shared | private | slave | unbindable |
2018 * | dest | | | | |
2019 * | | | | | | |
2020 * | v | | | | |
2021 * |**************************************************************************
2022 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
2023 * | | | | | |
2024 * |non-shared| shared (+*) | private | slave (*) | unbindable |
2025 * ***************************************************************************
2026 *
2027 * (+) the mount is moved to the destination. And is then propagated to
2028 * all the mounts in the propagation tree of the destination mount.
2029 * (+*) the mount is moved to the destination.
2030 * (+++) the mount is moved to the destination and is then propagated to
2031 * all the mounts belonging to the destination mount's propagation tree.
2032 * the mount is marked as 'shared and slave'.
2033 * (*) the mount continues to be a slave at the new location.
2034 *
2035 * if the source mount is a tree, the operations explained above is
2036 * applied to each mount in the tree.
2037 * Must be called without spinlocks held, since this function can sleep
2038 * in allocations.
2039 */
2040static int attach_recursive_mnt(struct mount *source_mnt,
2041 struct mount *dest_mnt,
2042 struct mountpoint *dest_mp,
2043 bool moving)
2044{
2045 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2046 HLIST_HEAD(tree_list);
2047 struct mnt_namespace *ns = dest_mnt->mnt_ns;
2048 struct mountpoint *smp;
2049 struct mount *child, *p;
2050 struct hlist_node *n;
2051 int err;
2052
2053 /* Preallocate a mountpoint in case the new mounts need
2054 * to be tucked under other mounts.
2055 */
2056 smp = get_mountpoint(source_mnt->mnt.mnt_root);
2057 if (IS_ERR(smp))
2058 return PTR_ERR(smp);
2059
2060 /* Is there space to add these mounts to the mount namespace? */
2061 if (!moving) {
2062 err = count_mounts(ns, source_mnt);
2063 if (err)
2064 goto out;
2065 }
2066
2067 if (IS_MNT_SHARED(dest_mnt)) {
2068 err = invent_group_ids(source_mnt, true);
2069 if (err)
2070 goto out;
2071 err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
2072 lock_mount_hash();
2073 if (err)
2074 goto out_cleanup_ids;
2075 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
2076 set_mnt_shared(p);
2077 } else {
2078 lock_mount_hash();
2079 }
2080 if (moving) {
2081 unhash_mnt(source_mnt);
2082 attach_mnt(source_mnt, dest_mnt, dest_mp);
2083 touch_mnt_namespace(source_mnt->mnt_ns);
2084 } else {
2085 if (source_mnt->mnt_ns) {
2086 /* move from anon - the caller will destroy */
2087 list_del_init(&source_mnt->mnt_ns->list);
2088 }
2089 mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
2090 commit_tree(source_mnt);
2091 }
2092
2093 hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) {
2094 struct mount *q;
2095 hlist_del_init(&child->mnt_hash);
2096 q = __lookup_mnt(&child->mnt_parent->mnt,
2097 child->mnt_mountpoint);
2098 if (q)
2099 mnt_change_mountpoint(child, smp, q);
2100 /* Notice when we are propagating across user namespaces */
2101 if (child->mnt_parent->mnt_ns->user_ns != user_ns)
2102 lock_mnt_tree(child);
2103 child->mnt.mnt_flags &= ~MNT_LOCKED;
2104 commit_tree(child);
2105 }
2106 put_mountpoint(smp);
2107 unlock_mount_hash();
2108
2109 return 0;
2110
2111 out_cleanup_ids:
2112 while (!hlist_empty(&tree_list)) {
2113 child = hlist_entry(tree_list.first, struct mount, mnt_hash);
2114 child->mnt_parent->mnt_ns->pending_mounts = 0;
2115 umount_tree(child, UMOUNT_SYNC);
2116 }
2117 unlock_mount_hash();
2118 cleanup_group_ids(source_mnt, NULL);
2119 out:
2120 ns->pending_mounts = 0;
2121
2122 read_seqlock_excl(&mount_lock);
2123 put_mountpoint(smp);
2124 read_sequnlock_excl(&mount_lock);
2125
2126 return err;
2127}
2128
2129static struct mountpoint *lock_mount(struct path *path)
2130{
2131 struct vfsmount *mnt;
2132 struct dentry *dentry = path->dentry;
2133retry:
2134 inode_lock(dentry->d_inode);
2135 if (unlikely(cant_mount(dentry))) {
2136 inode_unlock(dentry->d_inode);
2137 return ERR_PTR(-ENOENT);
2138 }
2139 namespace_lock();
2140 mnt = lookup_mnt(path);
2141 if (likely(!mnt)) {
2142 struct mountpoint *mp = get_mountpoint(dentry);
2143 if (IS_ERR(mp)) {
2144 namespace_unlock();
2145 inode_unlock(dentry->d_inode);
2146 return mp;
2147 }
2148 return mp;
2149 }
2150 namespace_unlock();
2151 inode_unlock(path->dentry->d_inode);
2152 path_put(path);
2153 path->mnt = mnt;
2154 dentry = path->dentry = dget(mnt->mnt_root);
2155 goto retry;
2156}
2157
2158static void unlock_mount(struct mountpoint *where)
2159{
2160 struct dentry *dentry = where->m_dentry;
2161
2162 read_seqlock_excl(&mount_lock);
2163 put_mountpoint(where);
2164 read_sequnlock_excl(&mount_lock);
2165
2166 namespace_unlock();
2167 inode_unlock(dentry->d_inode);
2168}
2169
2170static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
2171{
2172 if (mnt->mnt.mnt_sb->s_flags & SB_NOUSER)
2173 return -EINVAL;
2174
2175 if (d_is_dir(mp->m_dentry) !=
2176 d_is_dir(mnt->mnt.mnt_root))
2177 return -ENOTDIR;
2178
2179 return attach_recursive_mnt(mnt, p, mp, false);
2180}
2181
2182/*
2183 * Sanity check the flags to change_mnt_propagation.
2184 */
2185
2186static int flags_to_propagation_type(int ms_flags)
2187{
2188 int type = ms_flags & ~(MS_REC | MS_SILENT);
2189
2190 /* Fail if any non-propagation flags are set */
2191 if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2192 return 0;
2193 /* Only one propagation flag should be set */
2194 if (!is_power_of_2(type))
2195 return 0;
2196 return type;
2197}
2198
2199/*
2200 * recursively change the type of the mountpoint.
2201 */
2202static int do_change_type(struct path *path, int ms_flags)
2203{
2204 struct mount *m;
2205 struct mount *mnt = real_mount(path->mnt);
2206 int recurse = ms_flags & MS_REC;
2207 int type;
2208 int err = 0;
2209
2210 if (path->dentry != path->mnt->mnt_root)
2211 return -EINVAL;
2212
2213 type = flags_to_propagation_type(ms_flags);
2214 if (!type)
2215 return -EINVAL;
2216
2217 namespace_lock();
2218 if (type == MS_SHARED) {
2219 err = invent_group_ids(mnt, recurse);
2220 if (err)
2221 goto out_unlock;
2222 }
2223
2224 lock_mount_hash();
2225 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
2226 change_mnt_propagation(m, type);
2227 unlock_mount_hash();
2228
2229 out_unlock:
2230 namespace_unlock();
2231 return err;
2232}
2233
2234static bool has_locked_children(struct mount *mnt, struct dentry *dentry)
2235{
2236 struct mount *child;
2237 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
2238 if (!is_subdir(child->mnt_mountpoint, dentry))
2239 continue;
2240
2241 if (child->mnt.mnt_flags & MNT_LOCKED)
2242 return true;
2243 }
2244 return false;
2245}
2246
2247static struct mount *__do_loopback(struct path *old_path, int recurse)
2248{
2249 struct mount *mnt = ERR_PTR(-EINVAL), *old = real_mount(old_path->mnt);
2250
2251 if (IS_MNT_UNBINDABLE(old))
2252 return mnt;
2253
2254 if (!check_mnt(old) && old_path->dentry->d_op != &ns_dentry_operations)
2255 return mnt;
2256
2257 if (!recurse && has_locked_children(old, old_path->dentry))
2258 return mnt;
2259
2260 if (recurse)
2261 mnt = copy_tree(old, old_path->dentry, CL_COPY_MNT_NS_FILE);
2262 else
2263 mnt = clone_mnt(old, old_path->dentry, 0);
2264
2265 if (!IS_ERR(mnt))
2266 mnt->mnt.mnt_flags &= ~MNT_LOCKED;
2267
2268 return mnt;
2269}
2270
2271/*
2272 * do loopback mount.
2273 */
2274static int do_loopback(struct path *path, const char *old_name,
2275 int recurse)
2276{
2277 struct path old_path;
2278 struct mount *mnt = NULL, *parent;
2279 struct mountpoint *mp;
2280 int err;
2281 if (!old_name || !*old_name)
2282 return -EINVAL;
2283 err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
2284 if (err)
2285 return err;
2286
2287 err = -EINVAL;
2288 if (mnt_ns_loop(old_path.dentry))
2289 goto out;
2290
2291 mp = lock_mount(path);
2292 if (IS_ERR(mp)) {
2293 err = PTR_ERR(mp);
2294 goto out;
2295 }
2296
2297 parent = real_mount(path->mnt);
2298 if (!check_mnt(parent))
2299 goto out2;
2300
2301 mnt = __do_loopback(&old_path, recurse);
2302 if (IS_ERR(mnt)) {
2303 err = PTR_ERR(mnt);
2304 goto out2;
2305 }
2306
2307 err = graft_tree(mnt, parent, mp);
2308 if (err) {
2309 lock_mount_hash();
2310 umount_tree(mnt, UMOUNT_SYNC);
2311 unlock_mount_hash();
2312 }
2313out2:
2314 unlock_mount(mp);
2315out:
2316 path_put(&old_path);
2317 return err;
2318}
2319
2320static struct file *open_detached_copy(struct path *path, bool recursive)
2321{
2322 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2323 struct mnt_namespace *ns = alloc_mnt_ns(user_ns, true);
2324 struct mount *mnt, *p;
2325 struct file *file;
2326
2327 if (IS_ERR(ns))
2328 return ERR_CAST(ns);
2329
2330 namespace_lock();
2331 mnt = __do_loopback(path, recursive);
2332 if (IS_ERR(mnt)) {
2333 namespace_unlock();
2334 free_mnt_ns(ns);
2335 return ERR_CAST(mnt);
2336 }
2337
2338 lock_mount_hash();
2339 for (p = mnt; p; p = next_mnt(p, mnt)) {
2340 p->mnt_ns = ns;
2341 ns->mounts++;
2342 }
2343 ns->root = mnt;
2344 list_add_tail(&ns->list, &mnt->mnt_list);
2345 mntget(&mnt->mnt);
2346 unlock_mount_hash();
2347 namespace_unlock();
2348
2349 mntput(path->mnt);
2350 path->mnt = &mnt->mnt;
2351 file = dentry_open(path, O_PATH, current_cred());
2352 if (IS_ERR(file))
2353 dissolve_on_fput(path->mnt);
2354 else
2355 file->f_mode |= FMODE_NEED_UNMOUNT;
2356 return file;
2357}
2358
2359SYSCALL_DEFINE3(open_tree, int, dfd, const char *, filename, unsigned, flags)
2360{
2361 struct file *file;
2362 struct path path;
2363 int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW;
2364 bool detached = flags & OPEN_TREE_CLONE;
2365 int error;
2366 int fd;
2367
2368 BUILD_BUG_ON(OPEN_TREE_CLOEXEC != O_CLOEXEC);
2369
2370 if (flags & ~(AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_RECURSIVE |
2371 AT_SYMLINK_NOFOLLOW | OPEN_TREE_CLONE |
2372 OPEN_TREE_CLOEXEC))
2373 return -EINVAL;
2374
2375 if ((flags & (AT_RECURSIVE | OPEN_TREE_CLONE)) == AT_RECURSIVE)
2376 return -EINVAL;
2377
2378 if (flags & AT_NO_AUTOMOUNT)
2379 lookup_flags &= ~LOOKUP_AUTOMOUNT;
2380 if (flags & AT_SYMLINK_NOFOLLOW)
2381 lookup_flags &= ~LOOKUP_FOLLOW;
2382 if (flags & AT_EMPTY_PATH)
2383 lookup_flags |= LOOKUP_EMPTY;
2384
2385 if (detached && !may_mount())
2386 return -EPERM;
2387
2388 fd = get_unused_fd_flags(flags & O_CLOEXEC);
2389 if (fd < 0)
2390 return fd;
2391
2392 error = user_path_at(dfd, filename, lookup_flags, &path);
2393 if (unlikely(error)) {
2394 file = ERR_PTR(error);
2395 } else {
2396 if (detached)
2397 file = open_detached_copy(&path, flags & AT_RECURSIVE);
2398 else
2399 file = dentry_open(&path, O_PATH, current_cred());
2400 path_put(&path);
2401 }
2402 if (IS_ERR(file)) {
2403 put_unused_fd(fd);
2404 return PTR_ERR(file);
2405 }
2406 fd_install(fd, file);
2407 return fd;
2408}
2409
2410/*
2411 * Don't allow locked mount flags to be cleared.
2412 *
2413 * No locks need to be held here while testing the various MNT_LOCK
2414 * flags because those flags can never be cleared once they are set.
2415 */
2416static bool can_change_locked_flags(struct mount *mnt, unsigned int mnt_flags)
2417{
2418 unsigned int fl = mnt->mnt.mnt_flags;
2419
2420 if ((fl & MNT_LOCK_READONLY) &&
2421 !(mnt_flags & MNT_READONLY))
2422 return false;
2423
2424 if ((fl & MNT_LOCK_NODEV) &&
2425 !(mnt_flags & MNT_NODEV))
2426 return false;
2427
2428 if ((fl & MNT_LOCK_NOSUID) &&
2429 !(mnt_flags & MNT_NOSUID))
2430 return false;
2431
2432 if ((fl & MNT_LOCK_NOEXEC) &&
2433 !(mnt_flags & MNT_NOEXEC))
2434 return false;
2435
2436 if ((fl & MNT_LOCK_ATIME) &&
2437 ((fl & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK)))
2438 return false;
2439
2440 return true;
2441}
2442
2443static int change_mount_ro_state(struct mount *mnt, unsigned int mnt_flags)
2444{
2445 bool readonly_request = (mnt_flags & MNT_READONLY);
2446
2447 if (readonly_request == __mnt_is_readonly(&mnt->mnt))
2448 return 0;
2449
2450 if (readonly_request)
2451 return mnt_make_readonly(mnt);
2452
2453 return __mnt_unmake_readonly(mnt);
2454}
2455
2456/*
2457 * Update the user-settable attributes on a mount. The caller must hold
2458 * sb->s_umount for writing.
2459 */
2460static void set_mount_attributes(struct mount *mnt, unsigned int mnt_flags)
2461{
2462 lock_mount_hash();
2463 mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;
2464 mnt->mnt.mnt_flags = mnt_flags;
2465 touch_mnt_namespace(mnt->mnt_ns);
2466 unlock_mount_hash();
2467}
2468
2469static void mnt_warn_timestamp_expiry(struct path *mountpoint, struct vfsmount *mnt)
2470{
2471 struct super_block *sb = mnt->mnt_sb;
2472
2473 if (!__mnt_is_readonly(mnt) &&
2474 (ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX > sb->s_time_max)) {
2475 char *buf = (char *)__get_free_page(GFP_KERNEL);
2476 char *mntpath = buf ? d_path(mountpoint, buf, PAGE_SIZE) : ERR_PTR(-ENOMEM);
2477 struct tm tm;
2478
2479 time64_to_tm(sb->s_time_max, 0, &tm);
2480
2481 pr_warn("%s filesystem being %s at %s supports timestamps until %04ld (0x%llx)\n",
2482 sb->s_type->name,
2483 is_mounted(mnt) ? "remounted" : "mounted",
2484 mntpath,
2485 tm.tm_year+1900, (unsigned long long)sb->s_time_max);
2486
2487 free_page((unsigned long)buf);
2488 }
2489}
2490
2491/*
2492 * Handle reconfiguration of the mountpoint only without alteration of the
2493 * superblock it refers to. This is triggered by specifying MS_REMOUNT|MS_BIND
2494 * to mount(2).
2495 */
2496static int do_reconfigure_mnt(struct path *path, unsigned int mnt_flags)
2497{
2498 struct super_block *sb = path->mnt->mnt_sb;
2499 struct mount *mnt = real_mount(path->mnt);
2500 int ret;
2501
2502 if (!check_mnt(mnt))
2503 return -EINVAL;
2504
2505 if (path->dentry != mnt->mnt.mnt_root)
2506 return -EINVAL;
2507
2508 if (!can_change_locked_flags(mnt, mnt_flags))
2509 return -EPERM;
2510
2511 down_write(&sb->s_umount);
2512 ret = change_mount_ro_state(mnt, mnt_flags);
2513 if (ret == 0)
2514 set_mount_attributes(mnt, mnt_flags);
2515 up_write(&sb->s_umount);
2516
2517 mnt_warn_timestamp_expiry(path, &mnt->mnt);
2518
2519 return ret;
2520}
2521
2522/*
2523 * change filesystem flags. dir should be a physical root of filesystem.
2524 * If you've mounted a non-root directory somewhere and want to do remount
2525 * on it - tough luck.
2526 */
2527static int do_remount(struct path *path, int ms_flags, int sb_flags,
2528 int mnt_flags, void *data)
2529{
2530 int err;
2531 struct super_block *sb = path->mnt->mnt_sb;
2532 struct mount *mnt = real_mount(path->mnt);
2533 struct fs_context *fc;
2534
2535 if (!check_mnt(mnt))
2536 return -EINVAL;
2537
2538 if (path->dentry != path->mnt->mnt_root)
2539 return -EINVAL;
2540
2541 if (!can_change_locked_flags(mnt, mnt_flags))
2542 return -EPERM;
2543
2544 fc = fs_context_for_reconfigure(path->dentry, sb_flags, MS_RMT_MASK);
2545 if (IS_ERR(fc))
2546 return PTR_ERR(fc);
2547
2548 err = parse_monolithic_mount_data(fc, data);
2549 if (!err) {
2550 down_write(&sb->s_umount);
2551 err = -EPERM;
2552 if (ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) {
2553 err = reconfigure_super(fc);
2554 if (!err)
2555 set_mount_attributes(mnt, mnt_flags);
2556 }
2557 up_write(&sb->s_umount);
2558 }
2559
2560 mnt_warn_timestamp_expiry(path, &mnt->mnt);
2561
2562 put_fs_context(fc);
2563 return err;
2564}
2565
2566static inline int tree_contains_unbindable(struct mount *mnt)
2567{
2568 struct mount *p;
2569 for (p = mnt; p; p = next_mnt(p, mnt)) {
2570 if (IS_MNT_UNBINDABLE(p))
2571 return 1;
2572 }
2573 return 0;
2574}
2575
2576/*
2577 * Check that there aren't references to earlier/same mount namespaces in the
2578 * specified subtree. Such references can act as pins for mount namespaces
2579 * that aren't checked by the mount-cycle checking code, thereby allowing
2580 * cycles to be made.
2581 */
2582static bool check_for_nsfs_mounts(struct mount *subtree)
2583{
2584 struct mount *p;
2585 bool ret = false;
2586
2587 lock_mount_hash();
2588 for (p = subtree; p; p = next_mnt(p, subtree))
2589 if (mnt_ns_loop(p->mnt.mnt_root))
2590 goto out;
2591
2592 ret = true;
2593out:
2594 unlock_mount_hash();
2595 return ret;
2596}
2597
2598static int do_move_mount(struct path *old_path, struct path *new_path)
2599{
2600 struct mnt_namespace *ns;
2601 struct mount *p;
2602 struct mount *old;
2603 struct mount *parent;
2604 struct mountpoint *mp, *old_mp;
2605 int err;
2606 bool attached;
2607
2608 mp = lock_mount(new_path);
2609 if (IS_ERR(mp))
2610 return PTR_ERR(mp);
2611
2612 old = real_mount(old_path->mnt);
2613 p = real_mount(new_path->mnt);
2614 parent = old->mnt_parent;
2615 attached = mnt_has_parent(old);
2616 old_mp = old->mnt_mp;
2617 ns = old->mnt_ns;
2618
2619 err = -EINVAL;
2620 /* The mountpoint must be in our namespace. */
2621 if (!check_mnt(p))
2622 goto out;
2623
2624 /* The thing moved must be mounted... */
2625 if (!is_mounted(&old->mnt))
2626 goto out;
2627
2628 /* ... and either ours or the root of anon namespace */
2629 if (!(attached ? check_mnt(old) : is_anon_ns(ns)))
2630 goto out;
2631
2632 if (old->mnt.mnt_flags & MNT_LOCKED)
2633 goto out;
2634
2635 if (old_path->dentry != old_path->mnt->mnt_root)
2636 goto out;
2637
2638 if (d_is_dir(new_path->dentry) !=
2639 d_is_dir(old_path->dentry))
2640 goto out;
2641 /*
2642 * Don't move a mount residing in a shared parent.
2643 */
2644 if (attached && IS_MNT_SHARED(parent))
2645 goto out;
2646 /*
2647 * Don't move a mount tree containing unbindable mounts to a destination
2648 * mount which is shared.
2649 */
2650 if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
2651 goto out;
2652 err = -ELOOP;
2653 if (!check_for_nsfs_mounts(old))
2654 goto out;
2655 for (; mnt_has_parent(p); p = p->mnt_parent)
2656 if (p == old)
2657 goto out;
2658
2659 err = attach_recursive_mnt(old, real_mount(new_path->mnt), mp,
2660 attached);
2661 if (err)
2662 goto out;
2663
2664 /* if the mount is moved, it should no longer be expire
2665 * automatically */
2666 list_del_init(&old->mnt_expire);
2667 if (attached)
2668 put_mountpoint(old_mp);
2669out:
2670 unlock_mount(mp);
2671 if (!err) {
2672 if (attached)
2673 mntput_no_expire(parent);
2674 else
2675 free_mnt_ns(ns);
2676 }
2677 return err;
2678}
2679
2680static int do_move_mount_old(struct path *path, const char *old_name)
2681{
2682 struct path old_path;
2683 int err;
2684
2685 if (!old_name || !*old_name)
2686 return -EINVAL;
2687
2688 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
2689 if (err)
2690 return err;
2691
2692 err = do_move_mount(&old_path, path);
2693 path_put(&old_path);
2694 return err;
2695}
2696
2697/*
2698 * add a mount into a namespace's mount tree
2699 */
2700static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
2701{
2702 struct mountpoint *mp;
2703 struct mount *parent;
2704 int err;
2705
2706 mnt_flags &= ~MNT_INTERNAL_FLAGS;
2707
2708 mp = lock_mount(path);
2709 if (IS_ERR(mp))
2710 return PTR_ERR(mp);
2711
2712 parent = real_mount(path->mnt);
2713 err = -EINVAL;
2714 if (unlikely(!check_mnt(parent))) {
2715 /* that's acceptable only for automounts done in private ns */
2716 if (!(mnt_flags & MNT_SHRINKABLE))
2717 goto unlock;
2718 /* ... and for those we'd better have mountpoint still alive */
2719 if (!parent->mnt_ns)
2720 goto unlock;
2721 }
2722
2723 /* Refuse the same filesystem on the same mount point */
2724 err = -EBUSY;
2725 if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb &&
2726 path->mnt->mnt_root == path->dentry)
2727 goto unlock;
2728
2729 err = -EINVAL;
2730 if (d_is_symlink(newmnt->mnt.mnt_root))
2731 goto unlock;
2732
2733 newmnt->mnt.mnt_flags = mnt_flags;
2734 err = graft_tree(newmnt, parent, mp);
2735
2736unlock:
2737 unlock_mount(mp);
2738 return err;
2739}
2740
2741static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags);
2742
2743/*
2744 * Create a new mount using a superblock configuration and request it
2745 * be added to the namespace tree.
2746 */
2747static int do_new_mount_fc(struct fs_context *fc, struct path *mountpoint,
2748 unsigned int mnt_flags)
2749{
2750 struct vfsmount *mnt;
2751 struct super_block *sb = fc->root->d_sb;
2752 int error;
2753
2754 error = security_sb_kern_mount(sb);
2755 if (!error && mount_too_revealing(sb, &mnt_flags))
2756 error = -EPERM;
2757
2758 if (unlikely(error)) {
2759 fc_drop_locked(fc);
2760 return error;
2761 }
2762
2763 up_write(&sb->s_umount);
2764
2765 mnt = vfs_create_mount(fc);
2766 if (IS_ERR(mnt))
2767 return PTR_ERR(mnt);
2768
2769 mnt_warn_timestamp_expiry(mountpoint, mnt);
2770
2771 error = do_add_mount(real_mount(mnt), mountpoint, mnt_flags);
2772 if (error < 0)
2773 mntput(mnt);
2774 return error;
2775}
2776
2777/*
2778 * create a new mount for userspace and request it to be added into the
2779 * namespace's tree
2780 */
2781static int do_new_mount(struct path *path, const char *fstype, int sb_flags,
2782 int mnt_flags, const char *name, void *data)
2783{
2784 struct file_system_type *type;
2785 struct fs_context *fc;
2786 const char *subtype = NULL;
2787 int err = 0;
2788
2789 if (!fstype)
2790 return -EINVAL;
2791
2792 type = get_fs_type(fstype);
2793 if (!type)
2794 return -ENODEV;
2795
2796 if (type->fs_flags & FS_HAS_SUBTYPE) {
2797 subtype = strchr(fstype, '.');
2798 if (subtype) {
2799 subtype++;
2800 if (!*subtype) {
2801 put_filesystem(type);
2802 return -EINVAL;
2803 }
2804 }
2805 }
2806
2807 fc = fs_context_for_mount(type, sb_flags);
2808 put_filesystem(type);
2809 if (IS_ERR(fc))
2810 return PTR_ERR(fc);
2811
2812 if (subtype)
2813 err = vfs_parse_fs_string(fc, "subtype",
2814 subtype, strlen(subtype));
2815 if (!err && name)
2816 err = vfs_parse_fs_string(fc, "source", name, strlen(name));
2817 if (!err)
2818 err = parse_monolithic_mount_data(fc, data);
2819 if (!err && !mount_capable(fc))
2820 err = -EPERM;
2821 if (!err)
2822 err = vfs_get_tree(fc);
2823 if (!err)
2824 err = do_new_mount_fc(fc, path, mnt_flags);
2825
2826 put_fs_context(fc);
2827 return err;
2828}
2829
2830int finish_automount(struct vfsmount *m, struct path *path)
2831{
2832 struct mount *mnt = real_mount(m);
2833 int err;
2834 /* The new mount record should have at least 2 refs to prevent it being
2835 * expired before we get a chance to add it
2836 */
2837 BUG_ON(mnt_get_count(mnt) < 2);
2838
2839 if (m->mnt_sb == path->mnt->mnt_sb &&
2840 m->mnt_root == path->dentry) {
2841 err = -ELOOP;
2842 goto fail;
2843 }
2844
2845 err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
2846 if (!err)
2847 return 0;
2848fail:
2849 /* remove m from any expiration list it may be on */
2850 if (!list_empty(&mnt->mnt_expire)) {
2851 namespace_lock();
2852 list_del_init(&mnt->mnt_expire);
2853 namespace_unlock();
2854 }
2855 mntput(m);
2856 mntput(m);
2857 return err;
2858}
2859
2860/**
2861 * mnt_set_expiry - Put a mount on an expiration list
2862 * @mnt: The mount to list.
2863 * @expiry_list: The list to add the mount to.
2864 */
2865void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
2866{
2867 namespace_lock();
2868
2869 list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
2870
2871 namespace_unlock();
2872}
2873EXPORT_SYMBOL(mnt_set_expiry);
2874
2875/*
2876 * process a list of expirable mountpoints with the intent of discarding any
2877 * mountpoints that aren't in use and haven't been touched since last we came
2878 * here
2879 */
2880void mark_mounts_for_expiry(struct list_head *mounts)
2881{
2882 struct mount *mnt, *next;
2883 LIST_HEAD(graveyard);
2884
2885 if (list_empty(mounts))
2886 return;
2887
2888 namespace_lock();
2889 lock_mount_hash();
2890
2891 /* extract from the expiration list every vfsmount that matches the
2892 * following criteria:
2893 * - only referenced by its parent vfsmount
2894 * - still marked for expiry (marked on the last call here; marks are
2895 * cleared by mntput())
2896 */
2897 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
2898 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
2899 propagate_mount_busy(mnt, 1))
2900 continue;
2901 list_move(&mnt->mnt_expire, &graveyard);
2902 }
2903 while (!list_empty(&graveyard)) {
2904 mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
2905 touch_mnt_namespace(mnt->mnt_ns);
2906 umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
2907 }
2908 unlock_mount_hash();
2909 namespace_unlock();
2910}
2911
2912EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
2913
2914/*
2915 * Ripoff of 'select_parent()'
2916 *
2917 * search the list of submounts for a given mountpoint, and move any
2918 * shrinkable submounts to the 'graveyard' list.
2919 */
2920static int select_submounts(struct mount *parent, struct list_head *graveyard)
2921{
2922 struct mount *this_parent = parent;
2923 struct list_head *next;
2924 int found = 0;
2925
2926repeat:
2927 next = this_parent->mnt_mounts.next;
2928resume:
2929 while (next != &this_parent->mnt_mounts) {
2930 struct list_head *tmp = next;
2931 struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
2932
2933 next = tmp->next;
2934 if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
2935 continue;
2936 /*
2937 * Descend a level if the d_mounts list is non-empty.
2938 */
2939 if (!list_empty(&mnt->mnt_mounts)) {
2940 this_parent = mnt;
2941 goto repeat;
2942 }
2943
2944 if (!propagate_mount_busy(mnt, 1)) {
2945 list_move_tail(&mnt->mnt_expire, graveyard);
2946 found++;
2947 }
2948 }
2949 /*
2950 * All done at this level ... ascend and resume the search
2951 */
2952 if (this_parent != parent) {
2953 next = this_parent->mnt_child.next;
2954 this_parent = this_parent->mnt_parent;
2955 goto resume;
2956 }
2957 return found;
2958}
2959
2960/*
2961 * process a list of expirable mountpoints with the intent of discarding any
2962 * submounts of a specific parent mountpoint
2963 *
2964 * mount_lock must be held for write
2965 */
2966static void shrink_submounts(struct mount *mnt)
2967{
2968 LIST_HEAD(graveyard);
2969 struct mount *m;
2970
2971 /* extract submounts of 'mountpoint' from the expiration list */
2972 while (select_submounts(mnt, &graveyard)) {
2973 while (!list_empty(&graveyard)) {
2974 m = list_first_entry(&graveyard, struct mount,
2975 mnt_expire);
2976 touch_mnt_namespace(m->mnt_ns);
2977 umount_tree(m, UMOUNT_PROPAGATE|UMOUNT_SYNC);
2978 }
2979 }
2980}
2981
2982/*
2983 * Some copy_from_user() implementations do not return the exact number of
2984 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2985 * Note that this function differs from copy_from_user() in that it will oops
2986 * on bad values of `to', rather than returning a short copy.
2987 */
2988static long exact_copy_from_user(void *to, const void __user * from,
2989 unsigned long n)
2990{
2991 char *t = to;
2992 const char __user *f = from;
2993 char c;
2994
2995 if (!access_ok(from, n))
2996 return n;
2997
2998 while (n) {
2999 if (__get_user(c, f)) {
3000 memset(t, 0, n);
3001 break;
3002 }
3003 *t++ = c;
3004 f++;
3005 n--;
3006 }
3007 return n;
3008}
3009
3010void *copy_mount_options(const void __user * data)
3011{
3012 int i;
3013 unsigned long size;
3014 char *copy;
3015
3016 if (!data)
3017 return NULL;
3018
3019 copy = kmalloc(PAGE_SIZE, GFP_KERNEL);
3020 if (!copy)
3021 return ERR_PTR(-ENOMEM);
3022
3023 /* We only care that *some* data at the address the user
3024 * gave us is valid. Just in case, we'll zero
3025 * the remainder of the page.
3026 */
3027 /* copy_from_user cannot cross TASK_SIZE ! */
3028 size = TASK_SIZE - (unsigned long)untagged_addr(data);
3029 if (size > PAGE_SIZE)
3030 size = PAGE_SIZE;
3031
3032 i = size - exact_copy_from_user(copy, data, size);
3033 if (!i) {
3034 kfree(copy);
3035 return ERR_PTR(-EFAULT);
3036 }
3037 if (i != PAGE_SIZE)
3038 memset(copy + i, 0, PAGE_SIZE - i);
3039 return copy;
3040}
3041
3042char *copy_mount_string(const void __user *data)
3043{
3044 return data ? strndup_user(data, PATH_MAX) : NULL;
3045}
3046
3047/*
3048 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
3049 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
3050 *
3051 * data is a (void *) that can point to any structure up to
3052 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
3053 * information (or be NULL).
3054 *
3055 * Pre-0.97 versions of mount() didn't have a flags word.
3056 * When the flags word was introduced its top half was required
3057 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
3058 * Therefore, if this magic number is present, it carries no information
3059 * and must be discarded.
3060 */
3061long do_mount(const char *dev_name, const char __user *dir_name,
3062 const char *type_page, unsigned long flags, void *data_page)
3063{
3064 struct path path;
3065 unsigned int mnt_flags = 0, sb_flags;
3066 int retval = 0;
3067
3068 /* Discard magic */
3069 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
3070 flags &= ~MS_MGC_MSK;
3071
3072 /* Basic sanity checks */
3073 if (data_page)
3074 ((char *)data_page)[PAGE_SIZE - 1] = 0;
3075
3076 if (flags & MS_NOUSER)
3077 return -EINVAL;
3078
3079 /* ... and get the mountpoint */
3080 retval = user_path_at(AT_FDCWD, dir_name, LOOKUP_FOLLOW, &path);
3081 if (retval)
3082 return retval;
3083
3084 retval = security_sb_mount(dev_name, &path,
3085 type_page, flags, data_page);
3086 if (!retval && !may_mount())
3087 retval = -EPERM;
3088 if (!retval && (flags & SB_MANDLOCK) && !may_mandlock())
3089 retval = -EPERM;
3090 if (retval)
3091 goto dput_out;
3092
3093 /* Default to relatime unless overriden */
3094 if (!(flags & MS_NOATIME))
3095 mnt_flags |= MNT_RELATIME;
3096
3097 /* Separate the per-mountpoint flags */
3098 if (flags & MS_NOSUID)
3099 mnt_flags |= MNT_NOSUID;
3100 if (flags & MS_NODEV)
3101 mnt_flags |= MNT_NODEV;
3102 if (flags & MS_NOEXEC)
3103 mnt_flags |= MNT_NOEXEC;
3104 if (flags & MS_NOATIME)
3105 mnt_flags |= MNT_NOATIME;
3106 if (flags & MS_NODIRATIME)
3107 mnt_flags |= MNT_NODIRATIME;
3108 if (flags & MS_STRICTATIME)
3109 mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
3110 if (flags & MS_RDONLY)
3111 mnt_flags |= MNT_READONLY;
3112
3113 /* The default atime for remount is preservation */
3114 if ((flags & MS_REMOUNT) &&
3115 ((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME |
3116 MS_STRICTATIME)) == 0)) {
3117 mnt_flags &= ~MNT_ATIME_MASK;
3118 mnt_flags |= path.mnt->mnt_flags & MNT_ATIME_MASK;
3119 }
3120
3121 sb_flags = flags & (SB_RDONLY |
3122 SB_SYNCHRONOUS |
3123 SB_MANDLOCK |
3124 SB_DIRSYNC |
3125 SB_SILENT |
3126 SB_POSIXACL |
3127 SB_LAZYTIME |
3128 SB_I_VERSION);
3129
3130 if ((flags & (MS_REMOUNT | MS_BIND)) == (MS_REMOUNT | MS_BIND))
3131 retval = do_reconfigure_mnt(&path, mnt_flags);
3132 else if (flags & MS_REMOUNT)
3133 retval = do_remount(&path, flags, sb_flags, mnt_flags,
3134 data_page);
3135 else if (flags & MS_BIND)
3136 retval = do_loopback(&path, dev_name, flags & MS_REC);
3137 else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
3138 retval = do_change_type(&path, flags);
3139 else if (flags & MS_MOVE)
3140 retval = do_move_mount_old(&path, dev_name);
3141 else
3142 retval = do_new_mount(&path, type_page, sb_flags, mnt_flags,
3143 dev_name, data_page);
3144dput_out:
3145 path_put(&path);
3146 return retval;
3147}
3148
3149static struct ucounts *inc_mnt_namespaces(struct user_namespace *ns)
3150{
3151 return inc_ucount(ns, current_euid(), UCOUNT_MNT_NAMESPACES);
3152}
3153
3154static void dec_mnt_namespaces(struct ucounts *ucounts)
3155{
3156 dec_ucount(ucounts, UCOUNT_MNT_NAMESPACES);
3157}
3158
3159static void free_mnt_ns(struct mnt_namespace *ns)
3160{
3161 if (!is_anon_ns(ns))
3162 ns_free_inum(&ns->ns);
3163 dec_mnt_namespaces(ns->ucounts);
3164 put_user_ns(ns->user_ns);
3165 kfree(ns);
3166}
3167
3168/*
3169 * Assign a sequence number so we can detect when we attempt to bind
3170 * mount a reference to an older mount namespace into the current
3171 * mount namespace, preventing reference counting loops. A 64bit
3172 * number incrementing at 10Ghz will take 12,427 years to wrap which
3173 * is effectively never, so we can ignore the possibility.
3174 */
3175static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
3176
3177static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool anon)
3178{
3179 struct mnt_namespace *new_ns;
3180 struct ucounts *ucounts;
3181 int ret;
3182
3183 ucounts = inc_mnt_namespaces(user_ns);
3184 if (!ucounts)
3185 return ERR_PTR(-ENOSPC);
3186
3187 new_ns = kzalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
3188 if (!new_ns) {
3189 dec_mnt_namespaces(ucounts);
3190 return ERR_PTR(-ENOMEM);
3191 }
3192 if (!anon) {
3193 ret = ns_alloc_inum(&new_ns->ns);
3194 if (ret) {
3195 kfree(new_ns);
3196 dec_mnt_namespaces(ucounts);
3197 return ERR_PTR(ret);
3198 }
3199 }
3200 new_ns->ns.ops = &mntns_operations;
3201 if (!anon)
3202 new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
3203 atomic_set(&new_ns->count, 1);
3204 INIT_LIST_HEAD(&new_ns->list);
3205 init_waitqueue_head(&new_ns->poll);
3206 new_ns->user_ns = get_user_ns(user_ns);
3207 new_ns->ucounts = ucounts;
3208 return new_ns;
3209}
3210
3211__latent_entropy
3212struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
3213 struct user_namespace *user_ns, struct fs_struct *new_fs)
3214{
3215 struct mnt_namespace *new_ns;
3216 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
3217 struct mount *p, *q;
3218 struct mount *old;
3219 struct mount *new;
3220 int copy_flags;
3221
3222 BUG_ON(!ns);
3223
3224 if (likely(!(flags & CLONE_NEWNS))) {
3225 get_mnt_ns(ns);
3226 return ns;
3227 }
3228
3229 old = ns->root;
3230
3231 new_ns = alloc_mnt_ns(user_ns, false);
3232 if (IS_ERR(new_ns))
3233 return new_ns;
3234
3235 namespace_lock();
3236 /* First pass: copy the tree topology */
3237 copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
3238 if (user_ns != ns->user_ns)
3239 copy_flags |= CL_SHARED_TO_SLAVE;
3240 new = copy_tree(old, old->mnt.mnt_root, copy_flags);
3241 if (IS_ERR(new)) {
3242 namespace_unlock();
3243 free_mnt_ns(new_ns);
3244 return ERR_CAST(new);
3245 }
3246 if (user_ns != ns->user_ns) {
3247 lock_mount_hash();
3248 lock_mnt_tree(new);
3249 unlock_mount_hash();
3250 }
3251 new_ns->root = new;
3252 list_add_tail(&new_ns->list, &new->mnt_list);
3253
3254 /*
3255 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
3256 * as belonging to new namespace. We have already acquired a private
3257 * fs_struct, so tsk->fs->lock is not needed.
3258 */
3259 p = old;
3260 q = new;
3261 while (p) {
3262 q->mnt_ns = new_ns;
3263 new_ns->mounts++;
3264 if (new_fs) {
3265 if (&p->mnt == new_fs->root.mnt) {
3266 new_fs->root.mnt = mntget(&q->mnt);
3267 rootmnt = &p->mnt;
3268 }
3269 if (&p->mnt == new_fs->pwd.mnt) {
3270 new_fs->pwd.mnt = mntget(&q->mnt);
3271 pwdmnt = &p->mnt;
3272 }
3273 }
3274 p = next_mnt(p, old);
3275 q = next_mnt(q, new);
3276 if (!q)
3277 break;
3278 while (p->mnt.mnt_root != q->mnt.mnt_root)
3279 p = next_mnt(p, old);
3280 }
3281 namespace_unlock();
3282
3283 if (rootmnt)
3284 mntput(rootmnt);
3285 if (pwdmnt)
3286 mntput(pwdmnt);
3287
3288 return new_ns;
3289}
3290
3291struct dentry *mount_subtree(struct vfsmount *m, const char *name)
3292{
3293 struct mount *mnt = real_mount(m);
3294 struct mnt_namespace *ns;
3295 struct super_block *s;
3296 struct path path;
3297 int err;
3298
3299 ns = alloc_mnt_ns(&init_user_ns, true);
3300 if (IS_ERR(ns)) {
3301 mntput(m);
3302 return ERR_CAST(ns);
3303 }
3304 mnt->mnt_ns = ns;
3305 ns->root = mnt;
3306 ns->mounts++;
3307 list_add(&mnt->mnt_list, &ns->list);
3308
3309 err = vfs_path_lookup(m->mnt_root, m,
3310 name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
3311
3312 put_mnt_ns(ns);
3313
3314 if (err)
3315 return ERR_PTR(err);
3316
3317 /* trade a vfsmount reference for active sb one */
3318 s = path.mnt->mnt_sb;
3319 atomic_inc(&s->s_active);
3320 mntput(path.mnt);
3321 /* lock the sucker */
3322 down_write(&s->s_umount);
3323 /* ... and return the root of (sub)tree on it */
3324 return path.dentry;
3325}
3326EXPORT_SYMBOL(mount_subtree);
3327
3328int ksys_mount(const char __user *dev_name, const char __user *dir_name,
3329 const char __user *type, unsigned long flags, void __user *data)
3330{
3331 int ret;
3332 char *kernel_type;
3333 char *kernel_dev;
3334 void *options;
3335
3336 kernel_type = copy_mount_string(type);
3337 ret = PTR_ERR(kernel_type);
3338 if (IS_ERR(kernel_type))
3339 goto out_type;
3340
3341 kernel_dev = copy_mount_string(dev_name);
3342 ret = PTR_ERR(kernel_dev);
3343 if (IS_ERR(kernel_dev))
3344 goto out_dev;
3345
3346 options = copy_mount_options(data);
3347 ret = PTR_ERR(options);
3348 if (IS_ERR(options))
3349 goto out_data;
3350
3351 ret = do_mount(kernel_dev, dir_name, kernel_type, flags, options);
3352
3353 kfree(options);
3354out_data:
3355 kfree(kernel_dev);
3356out_dev:
3357 kfree(kernel_type);
3358out_type:
3359 return ret;
3360}
3361
3362SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
3363 char __user *, type, unsigned long, flags, void __user *, data)
3364{
3365 return ksys_mount(dev_name, dir_name, type, flags, data);
3366}
3367
3368/*
3369 * Create a kernel mount representation for a new, prepared superblock
3370 * (specified by fs_fd) and attach to an open_tree-like file descriptor.
3371 */
3372SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
3373 unsigned int, attr_flags)
3374{
3375 struct mnt_namespace *ns;
3376 struct fs_context *fc;
3377 struct file *file;
3378 struct path newmount;
3379 struct mount *mnt;
3380 struct fd f;
3381 unsigned int mnt_flags = 0;
3382 long ret;
3383
3384 if (!may_mount())
3385 return -EPERM;
3386
3387 if ((flags & ~(FSMOUNT_CLOEXEC)) != 0)
3388 return -EINVAL;
3389
3390 if (attr_flags & ~(MOUNT_ATTR_RDONLY |
3391 MOUNT_ATTR_NOSUID |
3392 MOUNT_ATTR_NODEV |
3393 MOUNT_ATTR_NOEXEC |
3394 MOUNT_ATTR__ATIME |
3395 MOUNT_ATTR_NODIRATIME))
3396 return -EINVAL;
3397
3398 if (attr_flags & MOUNT_ATTR_RDONLY)
3399 mnt_flags |= MNT_READONLY;
3400 if (attr_flags & MOUNT_ATTR_NOSUID)
3401 mnt_flags |= MNT_NOSUID;
3402 if (attr_flags & MOUNT_ATTR_NODEV)
3403 mnt_flags |= MNT_NODEV;
3404 if (attr_flags & MOUNT_ATTR_NOEXEC)
3405 mnt_flags |= MNT_NOEXEC;
3406 if (attr_flags & MOUNT_ATTR_NODIRATIME)
3407 mnt_flags |= MNT_NODIRATIME;
3408
3409 switch (attr_flags & MOUNT_ATTR__ATIME) {
3410 case MOUNT_ATTR_STRICTATIME:
3411 break;
3412 case MOUNT_ATTR_NOATIME:
3413 mnt_flags |= MNT_NOATIME;
3414 break;
3415 case MOUNT_ATTR_RELATIME:
3416 mnt_flags |= MNT_RELATIME;
3417 break;
3418 default:
3419 return -EINVAL;
3420 }
3421
3422 f = fdget(fs_fd);
3423 if (!f.file)
3424 return -EBADF;
3425
3426 ret = -EINVAL;
3427 if (f.file->f_op != &fscontext_fops)
3428 goto err_fsfd;
3429
3430 fc = f.file->private_data;
3431
3432 ret = mutex_lock_interruptible(&fc->uapi_mutex);
3433 if (ret < 0)
3434 goto err_fsfd;
3435
3436 /* There must be a valid superblock or we can't mount it */
3437 ret = -EINVAL;
3438 if (!fc->root)
3439 goto err_unlock;
3440
3441 ret = -EPERM;
3442 if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) {
3443 pr_warn("VFS: Mount too revealing\n");
3444 goto err_unlock;
3445 }
3446
3447 ret = -EBUSY;
3448 if (fc->phase != FS_CONTEXT_AWAITING_MOUNT)
3449 goto err_unlock;
3450
3451 ret = -EPERM;
3452 if ((fc->sb_flags & SB_MANDLOCK) && !may_mandlock())
3453 goto err_unlock;
3454
3455 newmount.mnt = vfs_create_mount(fc);
3456 if (IS_ERR(newmount.mnt)) {
3457 ret = PTR_ERR(newmount.mnt);
3458 goto err_unlock;
3459 }
3460 newmount.dentry = dget(fc->root);
3461 newmount.mnt->mnt_flags = mnt_flags;
3462
3463 /* We've done the mount bit - now move the file context into more or
3464 * less the same state as if we'd done an fspick(). We don't want to
3465 * do any memory allocation or anything like that at this point as we
3466 * don't want to have to handle any errors incurred.
3467 */
3468 vfs_clean_context(fc);
3469
3470 ns = alloc_mnt_ns(current->nsproxy->mnt_ns->user_ns, true);
3471 if (IS_ERR(ns)) {
3472 ret = PTR_ERR(ns);
3473 goto err_path;
3474 }
3475 mnt = real_mount(newmount.mnt);
3476 mnt->mnt_ns = ns;
3477 ns->root = mnt;
3478 ns->mounts = 1;
3479 list_add(&mnt->mnt_list, &ns->list);
3480 mntget(newmount.mnt);
3481
3482 /* Attach to an apparent O_PATH fd with a note that we need to unmount
3483 * it, not just simply put it.
3484 */
3485 file = dentry_open(&newmount, O_PATH, fc->cred);
3486 if (IS_ERR(file)) {
3487 dissolve_on_fput(newmount.mnt);
3488 ret = PTR_ERR(file);
3489 goto err_path;
3490 }
3491 file->f_mode |= FMODE_NEED_UNMOUNT;
3492
3493 ret = get_unused_fd_flags((flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0);
3494 if (ret >= 0)
3495 fd_install(ret, file);
3496 else
3497 fput(file);
3498
3499err_path:
3500 path_put(&newmount);
3501err_unlock:
3502 mutex_unlock(&fc->uapi_mutex);
3503err_fsfd:
3504 fdput(f);
3505 return ret;
3506}
3507
3508/*
3509 * Move a mount from one place to another. In combination with
3510 * fsopen()/fsmount() this is used to install a new mount and in combination
3511 * with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy
3512 * a mount subtree.
3513 *
3514 * Note the flags value is a combination of MOVE_MOUNT_* flags.
3515 */
3516SYSCALL_DEFINE5(move_mount,
3517 int, from_dfd, const char *, from_pathname,
3518 int, to_dfd, const char *, to_pathname,
3519 unsigned int, flags)
3520{
3521 struct path from_path, to_path;
3522 unsigned int lflags;
3523 int ret = 0;
3524
3525 if (!may_mount())
3526 return -EPERM;
3527
3528 if (flags & ~MOVE_MOUNT__MASK)
3529 return -EINVAL;
3530
3531 /* If someone gives a pathname, they aren't permitted to move
3532 * from an fd that requires unmount as we can't get at the flag
3533 * to clear it afterwards.
3534 */
3535 lflags = 0;
3536 if (flags & MOVE_MOUNT_F_SYMLINKS) lflags |= LOOKUP_FOLLOW;
3537 if (flags & MOVE_MOUNT_F_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT;
3538 if (flags & MOVE_MOUNT_F_EMPTY_PATH) lflags |= LOOKUP_EMPTY;
3539
3540 ret = user_path_at(from_dfd, from_pathname, lflags, &from_path);
3541 if (ret < 0)
3542 return ret;
3543
3544 lflags = 0;
3545 if (flags & MOVE_MOUNT_T_SYMLINKS) lflags |= LOOKUP_FOLLOW;
3546 if (flags & MOVE_MOUNT_T_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT;
3547 if (flags & MOVE_MOUNT_T_EMPTY_PATH) lflags |= LOOKUP_EMPTY;
3548
3549 ret = user_path_at(to_dfd, to_pathname, lflags, &to_path);
3550 if (ret < 0)
3551 goto out_from;
3552
3553 ret = security_move_mount(&from_path, &to_path);
3554 if (ret < 0)
3555 goto out_to;
3556
3557 ret = do_move_mount(&from_path, &to_path);
3558
3559out_to:
3560 path_put(&to_path);
3561out_from:
3562 path_put(&from_path);
3563 return ret;
3564}
3565
3566/*
3567 * Return true if path is reachable from root
3568 *
3569 * namespace_sem or mount_lock is held
3570 */
3571bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
3572 const struct path *root)
3573{
3574 while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
3575 dentry = mnt->mnt_mountpoint;
3576 mnt = mnt->mnt_parent;
3577 }
3578 return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
3579}
3580
3581bool path_is_under(const struct path *path1, const struct path *path2)
3582{
3583 bool res;
3584 read_seqlock_excl(&mount_lock);
3585 res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2);
3586 read_sequnlock_excl(&mount_lock);
3587 return res;
3588}
3589EXPORT_SYMBOL(path_is_under);
3590
3591/*
3592 * pivot_root Semantics:
3593 * Moves the root file system of the current process to the directory put_old,
3594 * makes new_root as the new root file system of the current process, and sets
3595 * root/cwd of all processes which had them on the current root to new_root.
3596 *
3597 * Restrictions:
3598 * The new_root and put_old must be directories, and must not be on the
3599 * same file system as the current process root. The put_old must be
3600 * underneath new_root, i.e. adding a non-zero number of /.. to the string
3601 * pointed to by put_old must yield the same directory as new_root. No other
3602 * file system may be mounted on put_old. After all, new_root is a mountpoint.
3603 *
3604 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
3605 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
3606 * in this situation.
3607 *
3608 * Notes:
3609 * - we don't move root/cwd if they are not at the root (reason: if something
3610 * cared enough to change them, it's probably wrong to force them elsewhere)
3611 * - it's okay to pick a root that isn't the root of a file system, e.g.
3612 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
3613 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
3614 * first.
3615 */
3616SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
3617 const char __user *, put_old)
3618{
3619 struct path new, old, root;
3620 struct mount *new_mnt, *root_mnt, *old_mnt, *root_parent, *ex_parent;
3621 struct mountpoint *old_mp, *root_mp;
3622 int error;
3623
3624 if (!may_mount())
3625 return -EPERM;
3626
3627 error = user_path_at(AT_FDCWD, new_root,
3628 LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &new);
3629 if (error)
3630 goto out0;
3631
3632 error = user_path_at(AT_FDCWD, put_old,
3633 LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old);
3634 if (error)
3635 goto out1;
3636
3637 error = security_sb_pivotroot(&old, &new);
3638 if (error)
3639 goto out2;
3640
3641 get_fs_root(current->fs, &root);
3642 old_mp = lock_mount(&old);
3643 error = PTR_ERR(old_mp);
3644 if (IS_ERR(old_mp))
3645 goto out3;
3646
3647 error = -EINVAL;
3648 new_mnt = real_mount(new.mnt);
3649 root_mnt = real_mount(root.mnt);
3650 old_mnt = real_mount(old.mnt);
3651 ex_parent = new_mnt->mnt_parent;
3652 root_parent = root_mnt->mnt_parent;
3653 if (IS_MNT_SHARED(old_mnt) ||
3654 IS_MNT_SHARED(ex_parent) ||
3655 IS_MNT_SHARED(root_parent))
3656 goto out4;
3657 if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
3658 goto out4;
3659 if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
3660 goto out4;
3661 error = -ENOENT;
3662 if (d_unlinked(new.dentry))
3663 goto out4;
3664 error = -EBUSY;
3665 if (new_mnt == root_mnt || old_mnt == root_mnt)
3666 goto out4; /* loop, on the same file system */
3667 error = -EINVAL;
3668 if (root.mnt->mnt_root != root.dentry)
3669 goto out4; /* not a mountpoint */
3670 if (!mnt_has_parent(root_mnt))
3671 goto out4; /* not attached */
3672 if (new.mnt->mnt_root != new.dentry)
3673 goto out4; /* not a mountpoint */
3674 if (!mnt_has_parent(new_mnt))
3675 goto out4; /* not attached */
3676 /* make sure we can reach put_old from new_root */
3677 if (!is_path_reachable(old_mnt, old.dentry, &new))
3678 goto out4;
3679 /* make certain new is below the root */
3680 if (!is_path_reachable(new_mnt, new.dentry, &root))
3681 goto out4;
3682 lock_mount_hash();
3683 umount_mnt(new_mnt);
3684 root_mp = unhash_mnt(root_mnt); /* we'll need its mountpoint */
3685 if (root_mnt->mnt.mnt_flags & MNT_LOCKED) {
3686 new_mnt->mnt.mnt_flags |= MNT_LOCKED;
3687 root_mnt->mnt.mnt_flags &= ~MNT_LOCKED;
3688 }
3689 /* mount old root on put_old */
3690 attach_mnt(root_mnt, old_mnt, old_mp);
3691 /* mount new_root on / */
3692 attach_mnt(new_mnt, root_parent, root_mp);
3693 mnt_add_count(root_parent, -1);
3694 touch_mnt_namespace(current->nsproxy->mnt_ns);
3695 /* A moved mount should not expire automatically */
3696 list_del_init(&new_mnt->mnt_expire);
3697 put_mountpoint(root_mp);
3698 unlock_mount_hash();
3699 chroot_fs_refs(&root, &new);
3700 error = 0;
3701out4:
3702 unlock_mount(old_mp);
3703 if (!error)
3704 mntput_no_expire(ex_parent);
3705out3:
3706 path_put(&root);
3707out2:
3708 path_put(&old);
3709out1:
3710 path_put(&new);
3711out0:
3712 return error;
3713}
3714
3715static void __init init_mount_tree(void)
3716{
3717 struct vfsmount *mnt;
3718 struct mount *m;
3719 struct mnt_namespace *ns;
3720 struct path root;
3721
3722 mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", NULL);
3723 if (IS_ERR(mnt))
3724 panic("Can't create rootfs");
3725
3726 ns = alloc_mnt_ns(&init_user_ns, false);
3727 if (IS_ERR(ns))
3728 panic("Can't allocate initial namespace");
3729 m = real_mount(mnt);
3730 m->mnt_ns = ns;
3731 ns->root = m;
3732 ns->mounts = 1;
3733 list_add(&m->mnt_list, &ns->list);
3734 init_task.nsproxy->mnt_ns = ns;
3735 get_mnt_ns(ns);
3736
3737 root.mnt = mnt;
3738 root.dentry = mnt->mnt_root;
3739 mnt->mnt_flags |= MNT_LOCKED;
3740
3741 set_fs_pwd(current->fs, &root);
3742 set_fs_root(current->fs, &root);
3743}
3744
3745void __init mnt_init(void)
3746{
3747 int err;
3748
3749 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
3750 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
3751
3752 mount_hashtable = alloc_large_system_hash("Mount-cache",
3753 sizeof(struct hlist_head),
3754 mhash_entries, 19,
3755 HASH_ZERO,
3756 &m_hash_shift, &m_hash_mask, 0, 0);
3757 mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache",
3758 sizeof(struct hlist_head),
3759 mphash_entries, 19,
3760 HASH_ZERO,
3761 &mp_hash_shift, &mp_hash_mask, 0, 0);
3762
3763 if (!mount_hashtable || !mountpoint_hashtable)
3764 panic("Failed to allocate mount hash table\n");
3765
3766 kernfs_init();
3767
3768 err = sysfs_init();
3769 if (err)
3770 printk(KERN_WARNING "%s: sysfs_init error: %d\n",
3771 __func__, err);
3772 fs_kobj = kobject_create_and_add("fs", NULL);
3773 if (!fs_kobj)
3774 printk(KERN_WARNING "%s: kobj create error\n", __func__);
3775 shmem_init();
3776 init_rootfs();
3777 init_mount_tree();
3778}
3779
3780void put_mnt_ns(struct mnt_namespace *ns)
3781{
3782 if (!atomic_dec_and_test(&ns->count))
3783 return;
3784 drop_collected_mounts(&ns->root->mnt);
3785 free_mnt_ns(ns);
3786}
3787
3788struct vfsmount *kern_mount(struct file_system_type *type)
3789{
3790 struct vfsmount *mnt;
3791 mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
3792 if (!IS_ERR(mnt)) {
3793 /*
3794 * it is a longterm mount, don't release mnt until
3795 * we unmount before file sys is unregistered
3796 */
3797 real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
3798 }
3799 return mnt;
3800}
3801EXPORT_SYMBOL_GPL(kern_mount);
3802
3803void kern_unmount(struct vfsmount *mnt)
3804{
3805 /* release long term mount so mount point can be released */
3806 if (!IS_ERR_OR_NULL(mnt)) {
3807 real_mount(mnt)->mnt_ns = NULL;
3808 synchronize_rcu(); /* yecchhh... */
3809 mntput(mnt);
3810 }
3811}
3812EXPORT_SYMBOL(kern_unmount);
3813
3814bool our_mnt(struct vfsmount *mnt)
3815{
3816 return check_mnt(real_mount(mnt));
3817}
3818
3819bool current_chrooted(void)
3820{
3821 /* Does the current process have a non-standard root */
3822 struct path ns_root;
3823 struct path fs_root;
3824 bool chrooted;
3825
3826 /* Find the namespace root */
3827 ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt;
3828 ns_root.dentry = ns_root.mnt->mnt_root;
3829 path_get(&ns_root);
3830 while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root))
3831 ;
3832
3833 get_fs_root(current->fs, &fs_root);
3834
3835 chrooted = !path_equal(&fs_root, &ns_root);
3836
3837 path_put(&fs_root);
3838 path_put(&ns_root);
3839
3840 return chrooted;
3841}
3842
3843static bool mnt_already_visible(struct mnt_namespace *ns,
3844 const struct super_block *sb,
3845 int *new_mnt_flags)
3846{
3847 int new_flags = *new_mnt_flags;
3848 struct mount *mnt;
3849 bool visible = false;
3850
3851 down_read(&namespace_sem);
3852 list_for_each_entry(mnt, &ns->list, mnt_list) {
3853 struct mount *child;
3854 int mnt_flags;
3855
3856 if (mnt->mnt.mnt_sb->s_type != sb->s_type)
3857 continue;
3858
3859 /* This mount is not fully visible if it's root directory
3860 * is not the root directory of the filesystem.
3861 */
3862 if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root)
3863 continue;
3864
3865 /* A local view of the mount flags */
3866 mnt_flags = mnt->mnt.mnt_flags;
3867
3868 /* Don't miss readonly hidden in the superblock flags */
3869 if (sb_rdonly(mnt->mnt.mnt_sb))
3870 mnt_flags |= MNT_LOCK_READONLY;
3871
3872 /* Verify the mount flags are equal to or more permissive
3873 * than the proposed new mount.
3874 */
3875 if ((mnt_flags & MNT_LOCK_READONLY) &&
3876 !(new_flags & MNT_READONLY))
3877 continue;
3878 if ((mnt_flags & MNT_LOCK_ATIME) &&
3879 ((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK)))
3880 continue;
3881
3882 /* This mount is not fully visible if there are any
3883 * locked child mounts that cover anything except for
3884 * empty directories.
3885 */
3886 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
3887 struct inode *inode = child->mnt_mountpoint->d_inode;
3888 /* Only worry about locked mounts */
3889 if (!(child->mnt.mnt_flags & MNT_LOCKED))
3890 continue;
3891 /* Is the directory permanetly empty? */
3892 if (!is_empty_dir_inode(inode))
3893 goto next;
3894 }
3895 /* Preserve the locked attributes */
3896 *new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \
3897 MNT_LOCK_ATIME);
3898 visible = true;
3899 goto found;
3900 next: ;
3901 }
3902found:
3903 up_read(&namespace_sem);
3904 return visible;
3905}
3906
3907static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags)
3908{
3909 const unsigned long required_iflags = SB_I_NOEXEC | SB_I_NODEV;
3910 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
3911 unsigned long s_iflags;
3912
3913 if (ns->user_ns == &init_user_ns)
3914 return false;
3915
3916 /* Can this filesystem be too revealing? */
3917 s_iflags = sb->s_iflags;
3918 if (!(s_iflags & SB_I_USERNS_VISIBLE))
3919 return false;
3920
3921 if ((s_iflags & required_iflags) != required_iflags) {
3922 WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n",
3923 required_iflags);
3924 return true;
3925 }
3926
3927 return !mnt_already_visible(ns, sb, new_mnt_flags);
3928}
3929
3930bool mnt_may_suid(struct vfsmount *mnt)
3931{
3932 /*
3933 * Foreign mounts (accessed via fchdir or through /proc
3934 * symlinks) are always treated as if they are nosuid. This
3935 * prevents namespaces from trusting potentially unsafe
3936 * suid/sgid bits, file caps, or security labels that originate
3937 * in other namespaces.
3938 */
3939 return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) &&
3940 current_in_userns(mnt->mnt_sb->s_user_ns);
3941}
3942
3943static struct ns_common *mntns_get(struct task_struct *task)
3944{
3945 struct ns_common *ns = NULL;
3946 struct nsproxy *nsproxy;
3947
3948 task_lock(task);
3949 nsproxy = task->nsproxy;
3950 if (nsproxy) {
3951 ns = &nsproxy->mnt_ns->ns;
3952 get_mnt_ns(to_mnt_ns(ns));
3953 }
3954 task_unlock(task);
3955
3956 return ns;
3957}
3958
3959static void mntns_put(struct ns_common *ns)
3960{
3961 put_mnt_ns(to_mnt_ns(ns));
3962}
3963
3964static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns)
3965{
3966 struct fs_struct *fs = current->fs;
3967 struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns;
3968 struct path root;
3969 int err;
3970
3971 if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
3972 !ns_capable(current_user_ns(), CAP_SYS_CHROOT) ||
3973 !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
3974 return -EPERM;
3975
3976 if (is_anon_ns(mnt_ns))
3977 return -EINVAL;
3978
3979 if (fs->users != 1)
3980 return -EINVAL;
3981
3982 get_mnt_ns(mnt_ns);
3983 old_mnt_ns = nsproxy->mnt_ns;
3984 nsproxy->mnt_ns = mnt_ns;
3985
3986 /* Find the root */
3987 err = vfs_path_lookup(mnt_ns->root->mnt.mnt_root, &mnt_ns->root->mnt,
3988 "/", LOOKUP_DOWN, &root);
3989 if (err) {
3990 /* revert to old namespace */
3991 nsproxy->mnt_ns = old_mnt_ns;
3992 put_mnt_ns(mnt_ns);
3993 return err;
3994 }
3995
3996 put_mnt_ns(old_mnt_ns);
3997
3998 /* Update the pwd and root */
3999 set_fs_pwd(fs, &root);
4000 set_fs_root(fs, &root);
4001
4002 path_put(&root);
4003 return 0;
4004}
4005
4006static struct user_namespace *mntns_owner(struct ns_common *ns)
4007{
4008 return to_mnt_ns(ns)->user_ns;
4009}
4010
4011const struct proc_ns_operations mntns_operations = {
4012 .name = "mnt",
4013 .type = CLONE_NEWNS,
4014 .get = mntns_get,
4015 .put = mntns_put,
4016 .install = mntns_install,
4017 .owner = mntns_owner,
4018};
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#include <linux/mnt_idmapping.h>
35#include <linux/nospec.h>
36
37#include "pnode.h"
38#include "internal.h"
39
40/* Maximum number of mounts in a mount namespace */
41static unsigned int sysctl_mount_max __read_mostly = 100000;
42
43static unsigned int m_hash_mask __ro_after_init;
44static unsigned int m_hash_shift __ro_after_init;
45static unsigned int mp_hash_mask __ro_after_init;
46static unsigned int mp_hash_shift __ro_after_init;
47
48static __initdata unsigned long mhash_entries;
49static int __init set_mhash_entries(char *str)
50{
51 if (!str)
52 return 0;
53 mhash_entries = simple_strtoul(str, &str, 0);
54 return 1;
55}
56__setup("mhash_entries=", set_mhash_entries);
57
58static __initdata unsigned long mphash_entries;
59static int __init set_mphash_entries(char *str)
60{
61 if (!str)
62 return 0;
63 mphash_entries = simple_strtoul(str, &str, 0);
64 return 1;
65}
66__setup("mphash_entries=", set_mphash_entries);
67
68static u64 event;
69static DEFINE_IDA(mnt_id_ida);
70static DEFINE_IDA(mnt_group_ida);
71
72/* Don't allow confusion with old 32bit mount ID */
73static atomic64_t mnt_id_ctr = ATOMIC64_INIT(1ULL << 32);
74
75static struct hlist_head *mount_hashtable __ro_after_init;
76static struct hlist_head *mountpoint_hashtable __ro_after_init;
77static struct kmem_cache *mnt_cache __ro_after_init;
78static DECLARE_RWSEM(namespace_sem);
79static HLIST_HEAD(unmounted); /* protected by namespace_sem */
80static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */
81
82struct mount_kattr {
83 unsigned int attr_set;
84 unsigned int attr_clr;
85 unsigned int propagation;
86 unsigned int lookup_flags;
87 bool recurse;
88 struct user_namespace *mnt_userns;
89 struct mnt_idmap *mnt_idmap;
90};
91
92/* /sys/fs */
93struct kobject *fs_kobj __ro_after_init;
94EXPORT_SYMBOL_GPL(fs_kobj);
95
96/*
97 * vfsmount lock may be taken for read to prevent changes to the
98 * vfsmount hash, ie. during mountpoint lookups or walking back
99 * up the tree.
100 *
101 * It should be taken for write in all cases where the vfsmount
102 * tree or hash is modified or when a vfsmount structure is modified.
103 */
104__cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock);
105
106static inline void lock_mount_hash(void)
107{
108 write_seqlock(&mount_lock);
109}
110
111static inline void unlock_mount_hash(void)
112{
113 write_sequnlock(&mount_lock);
114}
115
116static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry)
117{
118 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
119 tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
120 tmp = tmp + (tmp >> m_hash_shift);
121 return &mount_hashtable[tmp & m_hash_mask];
122}
123
124static inline struct hlist_head *mp_hash(struct dentry *dentry)
125{
126 unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES);
127 tmp = tmp + (tmp >> mp_hash_shift);
128 return &mountpoint_hashtable[tmp & mp_hash_mask];
129}
130
131static int mnt_alloc_id(struct mount *mnt)
132{
133 int res = ida_alloc(&mnt_id_ida, GFP_KERNEL);
134
135 if (res < 0)
136 return res;
137 mnt->mnt_id = res;
138 mnt->mnt_id_unique = atomic64_inc_return(&mnt_id_ctr);
139 return 0;
140}
141
142static void mnt_free_id(struct mount *mnt)
143{
144 ida_free(&mnt_id_ida, mnt->mnt_id);
145}
146
147/*
148 * Allocate a new peer group ID
149 */
150static int mnt_alloc_group_id(struct mount *mnt)
151{
152 int res = ida_alloc_min(&mnt_group_ida, 1, GFP_KERNEL);
153
154 if (res < 0)
155 return res;
156 mnt->mnt_group_id = res;
157 return 0;
158}
159
160/*
161 * Release a peer group ID
162 */
163void mnt_release_group_id(struct mount *mnt)
164{
165 ida_free(&mnt_group_ida, mnt->mnt_group_id);
166 mnt->mnt_group_id = 0;
167}
168
169/*
170 * vfsmount lock must be held for read
171 */
172static inline void mnt_add_count(struct mount *mnt, int n)
173{
174#ifdef CONFIG_SMP
175 this_cpu_add(mnt->mnt_pcp->mnt_count, n);
176#else
177 preempt_disable();
178 mnt->mnt_count += n;
179 preempt_enable();
180#endif
181}
182
183/*
184 * vfsmount lock must be held for write
185 */
186int mnt_get_count(struct mount *mnt)
187{
188#ifdef CONFIG_SMP
189 int count = 0;
190 int cpu;
191
192 for_each_possible_cpu(cpu) {
193 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
194 }
195
196 return count;
197#else
198 return mnt->mnt_count;
199#endif
200}
201
202static struct mount *alloc_vfsmnt(const char *name)
203{
204 struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
205 if (mnt) {
206 int err;
207
208 err = mnt_alloc_id(mnt);
209 if (err)
210 goto out_free_cache;
211
212 if (name) {
213 mnt->mnt_devname = kstrdup_const(name,
214 GFP_KERNEL_ACCOUNT);
215 if (!mnt->mnt_devname)
216 goto out_free_id;
217 }
218
219#ifdef CONFIG_SMP
220 mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
221 if (!mnt->mnt_pcp)
222 goto out_free_devname;
223
224 this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
225#else
226 mnt->mnt_count = 1;
227 mnt->mnt_writers = 0;
228#endif
229
230 INIT_HLIST_NODE(&mnt->mnt_hash);
231 INIT_LIST_HEAD(&mnt->mnt_child);
232 INIT_LIST_HEAD(&mnt->mnt_mounts);
233 INIT_LIST_HEAD(&mnt->mnt_list);
234 INIT_LIST_HEAD(&mnt->mnt_expire);
235 INIT_LIST_HEAD(&mnt->mnt_share);
236 INIT_LIST_HEAD(&mnt->mnt_slave_list);
237 INIT_LIST_HEAD(&mnt->mnt_slave);
238 INIT_HLIST_NODE(&mnt->mnt_mp_list);
239 INIT_LIST_HEAD(&mnt->mnt_umounting);
240 INIT_HLIST_HEAD(&mnt->mnt_stuck_children);
241 mnt->mnt.mnt_idmap = &nop_mnt_idmap;
242 }
243 return mnt;
244
245#ifdef CONFIG_SMP
246out_free_devname:
247 kfree_const(mnt->mnt_devname);
248#endif
249out_free_id:
250 mnt_free_id(mnt);
251out_free_cache:
252 kmem_cache_free(mnt_cache, mnt);
253 return NULL;
254}
255
256/*
257 * Most r/o checks on a fs are for operations that take
258 * discrete amounts of time, like a write() or unlink().
259 * We must keep track of when those operations start
260 * (for permission checks) and when they end, so that
261 * we can determine when writes are able to occur to
262 * a filesystem.
263 */
264/*
265 * __mnt_is_readonly: check whether a mount is read-only
266 * @mnt: the mount to check for its write status
267 *
268 * This shouldn't be used directly ouside of the VFS.
269 * It does not guarantee that the filesystem will stay
270 * r/w, just that it is right *now*. This can not and
271 * should not be used in place of IS_RDONLY(inode).
272 * mnt_want/drop_write() will _keep_ the filesystem
273 * r/w.
274 */
275bool __mnt_is_readonly(struct vfsmount *mnt)
276{
277 return (mnt->mnt_flags & MNT_READONLY) || sb_rdonly(mnt->mnt_sb);
278}
279EXPORT_SYMBOL_GPL(__mnt_is_readonly);
280
281static inline void mnt_inc_writers(struct mount *mnt)
282{
283#ifdef CONFIG_SMP
284 this_cpu_inc(mnt->mnt_pcp->mnt_writers);
285#else
286 mnt->mnt_writers++;
287#endif
288}
289
290static inline void mnt_dec_writers(struct mount *mnt)
291{
292#ifdef CONFIG_SMP
293 this_cpu_dec(mnt->mnt_pcp->mnt_writers);
294#else
295 mnt->mnt_writers--;
296#endif
297}
298
299static unsigned int mnt_get_writers(struct mount *mnt)
300{
301#ifdef CONFIG_SMP
302 unsigned int count = 0;
303 int cpu;
304
305 for_each_possible_cpu(cpu) {
306 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
307 }
308
309 return count;
310#else
311 return mnt->mnt_writers;
312#endif
313}
314
315static int mnt_is_readonly(struct vfsmount *mnt)
316{
317 if (READ_ONCE(mnt->mnt_sb->s_readonly_remount))
318 return 1;
319 /*
320 * The barrier pairs with the barrier in sb_start_ro_state_change()
321 * making sure if we don't see s_readonly_remount set yet, we also will
322 * not see any superblock / mount flag changes done by remount.
323 * It also pairs with the barrier in sb_end_ro_state_change()
324 * assuring that if we see s_readonly_remount already cleared, we will
325 * see the values of superblock / mount flags updated by remount.
326 */
327 smp_rmb();
328 return __mnt_is_readonly(mnt);
329}
330
331/*
332 * Most r/o & frozen checks on a fs are for operations that take discrete
333 * amounts of time, like a write() or unlink(). We must keep track of when
334 * those operations start (for permission checks) and when they end, so that we
335 * can determine when writes are able to occur to a filesystem.
336 */
337/**
338 * mnt_get_write_access - get write access to a mount without freeze protection
339 * @m: the mount on which to take a write
340 *
341 * This tells the low-level filesystem that a write is about to be performed to
342 * it, and makes sure that writes are allowed (mnt it read-write) before
343 * returning success. This operation does not protect against filesystem being
344 * frozen. When the write operation is finished, mnt_put_write_access() must be
345 * called. This is effectively a refcount.
346 */
347int mnt_get_write_access(struct vfsmount *m)
348{
349 struct mount *mnt = real_mount(m);
350 int ret = 0;
351
352 preempt_disable();
353 mnt_inc_writers(mnt);
354 /*
355 * The store to mnt_inc_writers must be visible before we pass
356 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
357 * incremented count after it has set MNT_WRITE_HOLD.
358 */
359 smp_mb();
360 might_lock(&mount_lock.lock);
361 while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) {
362 if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
363 cpu_relax();
364 } else {
365 /*
366 * This prevents priority inversion, if the task
367 * setting MNT_WRITE_HOLD got preempted on a remote
368 * CPU, and it prevents life lock if the task setting
369 * MNT_WRITE_HOLD has a lower priority and is bound to
370 * the same CPU as the task that is spinning here.
371 */
372 preempt_enable();
373 lock_mount_hash();
374 unlock_mount_hash();
375 preempt_disable();
376 }
377 }
378 /*
379 * The barrier pairs with the barrier sb_start_ro_state_change() making
380 * sure that if we see MNT_WRITE_HOLD cleared, we will also see
381 * s_readonly_remount set (or even SB_RDONLY / MNT_READONLY flags) in
382 * mnt_is_readonly() and bail in case we are racing with remount
383 * read-only.
384 */
385 smp_rmb();
386 if (mnt_is_readonly(m)) {
387 mnt_dec_writers(mnt);
388 ret = -EROFS;
389 }
390 preempt_enable();
391
392 return ret;
393}
394EXPORT_SYMBOL_GPL(mnt_get_write_access);
395
396/**
397 * mnt_want_write - get write access to a mount
398 * @m: the mount on which to take a write
399 *
400 * This tells the low-level filesystem that a write is about to be performed to
401 * it, and makes sure that writes are allowed (mount is read-write, filesystem
402 * is not frozen) before returning success. When the write operation is
403 * finished, mnt_drop_write() must be called. This is effectively a refcount.
404 */
405int mnt_want_write(struct vfsmount *m)
406{
407 int ret;
408
409 sb_start_write(m->mnt_sb);
410 ret = mnt_get_write_access(m);
411 if (ret)
412 sb_end_write(m->mnt_sb);
413 return ret;
414}
415EXPORT_SYMBOL_GPL(mnt_want_write);
416
417/**
418 * mnt_get_write_access_file - get write access to a file's mount
419 * @file: the file who's mount on which to take a write
420 *
421 * This is like mnt_get_write_access, but if @file is already open for write it
422 * skips incrementing mnt_writers (since the open file already has a reference)
423 * and instead only does the check for emergency r/o remounts. This must be
424 * paired with mnt_put_write_access_file.
425 */
426int mnt_get_write_access_file(struct file *file)
427{
428 if (file->f_mode & FMODE_WRITER) {
429 /*
430 * Superblock may have become readonly while there are still
431 * writable fd's, e.g. due to a fs error with errors=remount-ro
432 */
433 if (__mnt_is_readonly(file->f_path.mnt))
434 return -EROFS;
435 return 0;
436 }
437 return mnt_get_write_access(file->f_path.mnt);
438}
439
440/**
441 * mnt_want_write_file - get write access to a file's mount
442 * @file: the file who's mount on which to take a write
443 *
444 * This is like mnt_want_write, but if the file is already open for writing it
445 * skips incrementing mnt_writers (since the open file already has a reference)
446 * and instead only does the freeze protection and the check for emergency r/o
447 * remounts. This must be paired with mnt_drop_write_file.
448 */
449int mnt_want_write_file(struct file *file)
450{
451 int ret;
452
453 sb_start_write(file_inode(file)->i_sb);
454 ret = mnt_get_write_access_file(file);
455 if (ret)
456 sb_end_write(file_inode(file)->i_sb);
457 return ret;
458}
459EXPORT_SYMBOL_GPL(mnt_want_write_file);
460
461/**
462 * mnt_put_write_access - give up write access to a mount
463 * @mnt: the mount on which to give up write access
464 *
465 * Tells the low-level filesystem that we are done
466 * performing writes to it. Must be matched with
467 * mnt_get_write_access() call above.
468 */
469void mnt_put_write_access(struct vfsmount *mnt)
470{
471 preempt_disable();
472 mnt_dec_writers(real_mount(mnt));
473 preempt_enable();
474}
475EXPORT_SYMBOL_GPL(mnt_put_write_access);
476
477/**
478 * mnt_drop_write - give up write access to a mount
479 * @mnt: the mount on which to give up write access
480 *
481 * Tells the low-level filesystem that we are done performing writes to it and
482 * also allows filesystem to be frozen again. Must be matched with
483 * mnt_want_write() call above.
484 */
485void mnt_drop_write(struct vfsmount *mnt)
486{
487 mnt_put_write_access(mnt);
488 sb_end_write(mnt->mnt_sb);
489}
490EXPORT_SYMBOL_GPL(mnt_drop_write);
491
492void mnt_put_write_access_file(struct file *file)
493{
494 if (!(file->f_mode & FMODE_WRITER))
495 mnt_put_write_access(file->f_path.mnt);
496}
497
498void mnt_drop_write_file(struct file *file)
499{
500 mnt_put_write_access_file(file);
501 sb_end_write(file_inode(file)->i_sb);
502}
503EXPORT_SYMBOL(mnt_drop_write_file);
504
505/**
506 * mnt_hold_writers - prevent write access to the given mount
507 * @mnt: mnt to prevent write access to
508 *
509 * Prevents write access to @mnt if there are no active writers for @mnt.
510 * This function needs to be called and return successfully before changing
511 * properties of @mnt that need to remain stable for callers with write access
512 * to @mnt.
513 *
514 * After this functions has been called successfully callers must pair it with
515 * a call to mnt_unhold_writers() in order to stop preventing write access to
516 * @mnt.
517 *
518 * Context: This function expects lock_mount_hash() to be held serializing
519 * setting MNT_WRITE_HOLD.
520 * Return: On success 0 is returned.
521 * On error, -EBUSY is returned.
522 */
523static inline int mnt_hold_writers(struct mount *mnt)
524{
525 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
526 /*
527 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
528 * should be visible before we do.
529 */
530 smp_mb();
531
532 /*
533 * With writers on hold, if this value is zero, then there are
534 * definitely no active writers (although held writers may subsequently
535 * increment the count, they'll have to wait, and decrement it after
536 * seeing MNT_READONLY).
537 *
538 * It is OK to have counter incremented on one CPU and decremented on
539 * another: the sum will add up correctly. The danger would be when we
540 * sum up each counter, if we read a counter before it is incremented,
541 * but then read another CPU's count which it has been subsequently
542 * decremented from -- we would see more decrements than we should.
543 * MNT_WRITE_HOLD protects against this scenario, because
544 * mnt_want_write first increments count, then smp_mb, then spins on
545 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
546 * we're counting up here.
547 */
548 if (mnt_get_writers(mnt) > 0)
549 return -EBUSY;
550
551 return 0;
552}
553
554/**
555 * mnt_unhold_writers - stop preventing write access to the given mount
556 * @mnt: mnt to stop preventing write access to
557 *
558 * Stop preventing write access to @mnt allowing callers to gain write access
559 * to @mnt again.
560 *
561 * This function can only be called after a successful call to
562 * mnt_hold_writers().
563 *
564 * Context: This function expects lock_mount_hash() to be held.
565 */
566static inline void mnt_unhold_writers(struct mount *mnt)
567{
568 /*
569 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
570 * that become unheld will see MNT_READONLY.
571 */
572 smp_wmb();
573 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
574}
575
576static int mnt_make_readonly(struct mount *mnt)
577{
578 int ret;
579
580 ret = mnt_hold_writers(mnt);
581 if (!ret)
582 mnt->mnt.mnt_flags |= MNT_READONLY;
583 mnt_unhold_writers(mnt);
584 return ret;
585}
586
587int sb_prepare_remount_readonly(struct super_block *sb)
588{
589 struct mount *mnt;
590 int err = 0;
591
592 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
593 if (atomic_long_read(&sb->s_remove_count))
594 return -EBUSY;
595
596 lock_mount_hash();
597 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
598 if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
599 err = mnt_hold_writers(mnt);
600 if (err)
601 break;
602 }
603 }
604 if (!err && atomic_long_read(&sb->s_remove_count))
605 err = -EBUSY;
606
607 if (!err)
608 sb_start_ro_state_change(sb);
609 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
610 if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
611 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
612 }
613 unlock_mount_hash();
614
615 return err;
616}
617
618static void free_vfsmnt(struct mount *mnt)
619{
620 mnt_idmap_put(mnt_idmap(&mnt->mnt));
621 kfree_const(mnt->mnt_devname);
622#ifdef CONFIG_SMP
623 free_percpu(mnt->mnt_pcp);
624#endif
625 kmem_cache_free(mnt_cache, mnt);
626}
627
628static void delayed_free_vfsmnt(struct rcu_head *head)
629{
630 free_vfsmnt(container_of(head, struct mount, mnt_rcu));
631}
632
633/* call under rcu_read_lock */
634int __legitimize_mnt(struct vfsmount *bastard, unsigned seq)
635{
636 struct mount *mnt;
637 if (read_seqretry(&mount_lock, seq))
638 return 1;
639 if (bastard == NULL)
640 return 0;
641 mnt = real_mount(bastard);
642 mnt_add_count(mnt, 1);
643 smp_mb(); // see mntput_no_expire()
644 if (likely(!read_seqretry(&mount_lock, seq)))
645 return 0;
646 if (bastard->mnt_flags & MNT_SYNC_UMOUNT) {
647 mnt_add_count(mnt, -1);
648 return 1;
649 }
650 lock_mount_hash();
651 if (unlikely(bastard->mnt_flags & MNT_DOOMED)) {
652 mnt_add_count(mnt, -1);
653 unlock_mount_hash();
654 return 1;
655 }
656 unlock_mount_hash();
657 /* caller will mntput() */
658 return -1;
659}
660
661/* call under rcu_read_lock */
662static bool legitimize_mnt(struct vfsmount *bastard, unsigned seq)
663{
664 int res = __legitimize_mnt(bastard, seq);
665 if (likely(!res))
666 return true;
667 if (unlikely(res < 0)) {
668 rcu_read_unlock();
669 mntput(bastard);
670 rcu_read_lock();
671 }
672 return false;
673}
674
675/**
676 * __lookup_mnt - find first child mount
677 * @mnt: parent mount
678 * @dentry: mountpoint
679 *
680 * If @mnt has a child mount @c mounted @dentry find and return it.
681 *
682 * Note that the child mount @c need not be unique. There are cases
683 * where shadow mounts are created. For example, during mount
684 * propagation when a source mount @mnt whose root got overmounted by a
685 * mount @o after path lookup but before @namespace_sem could be
686 * acquired gets copied and propagated. So @mnt gets copied including
687 * @o. When @mnt is propagated to a destination mount @d that already
688 * has another mount @n mounted at the same mountpoint then the source
689 * mount @mnt will be tucked beneath @n, i.e., @n will be mounted on
690 * @mnt and @mnt mounted on @d. Now both @n and @o are mounted at @mnt
691 * on @dentry.
692 *
693 * Return: The first child of @mnt mounted @dentry or NULL.
694 */
695struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
696{
697 struct hlist_head *head = m_hash(mnt, dentry);
698 struct mount *p;
699
700 hlist_for_each_entry_rcu(p, head, mnt_hash)
701 if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
702 return p;
703 return NULL;
704}
705
706/*
707 * lookup_mnt - Return the first child mount mounted at path
708 *
709 * "First" means first mounted chronologically. If you create the
710 * following mounts:
711 *
712 * mount /dev/sda1 /mnt
713 * mount /dev/sda2 /mnt
714 * mount /dev/sda3 /mnt
715 *
716 * Then lookup_mnt() on the base /mnt dentry in the root mount will
717 * return successively the root dentry and vfsmount of /dev/sda1, then
718 * /dev/sda2, then /dev/sda3, then NULL.
719 *
720 * lookup_mnt takes a reference to the found vfsmount.
721 */
722struct vfsmount *lookup_mnt(const struct path *path)
723{
724 struct mount *child_mnt;
725 struct vfsmount *m;
726 unsigned seq;
727
728 rcu_read_lock();
729 do {
730 seq = read_seqbegin(&mount_lock);
731 child_mnt = __lookup_mnt(path->mnt, path->dentry);
732 m = child_mnt ? &child_mnt->mnt : NULL;
733 } while (!legitimize_mnt(m, seq));
734 rcu_read_unlock();
735 return m;
736}
737
738/*
739 * __is_local_mountpoint - Test to see if dentry is a mountpoint in the
740 * current mount namespace.
741 *
742 * The common case is dentries are not mountpoints at all and that
743 * test is handled inline. For the slow case when we are actually
744 * dealing with a mountpoint of some kind, walk through all of the
745 * mounts in the current mount namespace and test to see if the dentry
746 * is a mountpoint.
747 *
748 * The mount_hashtable is not usable in the context because we
749 * need to identify all mounts that may be in the current mount
750 * namespace not just a mount that happens to have some specified
751 * parent mount.
752 */
753bool __is_local_mountpoint(struct dentry *dentry)
754{
755 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
756 struct mount *mnt, *n;
757 bool is_covered = false;
758
759 down_read(&namespace_sem);
760 rbtree_postorder_for_each_entry_safe(mnt, n, &ns->mounts, mnt_node) {
761 is_covered = (mnt->mnt_mountpoint == dentry);
762 if (is_covered)
763 break;
764 }
765 up_read(&namespace_sem);
766
767 return is_covered;
768}
769
770static struct mountpoint *lookup_mountpoint(struct dentry *dentry)
771{
772 struct hlist_head *chain = mp_hash(dentry);
773 struct mountpoint *mp;
774
775 hlist_for_each_entry(mp, chain, m_hash) {
776 if (mp->m_dentry == dentry) {
777 mp->m_count++;
778 return mp;
779 }
780 }
781 return NULL;
782}
783
784static struct mountpoint *get_mountpoint(struct dentry *dentry)
785{
786 struct mountpoint *mp, *new = NULL;
787 int ret;
788
789 if (d_mountpoint(dentry)) {
790 /* might be worth a WARN_ON() */
791 if (d_unlinked(dentry))
792 return ERR_PTR(-ENOENT);
793mountpoint:
794 read_seqlock_excl(&mount_lock);
795 mp = lookup_mountpoint(dentry);
796 read_sequnlock_excl(&mount_lock);
797 if (mp)
798 goto done;
799 }
800
801 if (!new)
802 new = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
803 if (!new)
804 return ERR_PTR(-ENOMEM);
805
806
807 /* Exactly one processes may set d_mounted */
808 ret = d_set_mounted(dentry);
809
810 /* Someone else set d_mounted? */
811 if (ret == -EBUSY)
812 goto mountpoint;
813
814 /* The dentry is not available as a mountpoint? */
815 mp = ERR_PTR(ret);
816 if (ret)
817 goto done;
818
819 /* Add the new mountpoint to the hash table */
820 read_seqlock_excl(&mount_lock);
821 new->m_dentry = dget(dentry);
822 new->m_count = 1;
823 hlist_add_head(&new->m_hash, mp_hash(dentry));
824 INIT_HLIST_HEAD(&new->m_list);
825 read_sequnlock_excl(&mount_lock);
826
827 mp = new;
828 new = NULL;
829done:
830 kfree(new);
831 return mp;
832}
833
834/*
835 * vfsmount lock must be held. Additionally, the caller is responsible
836 * for serializing calls for given disposal list.
837 */
838static void __put_mountpoint(struct mountpoint *mp, struct list_head *list)
839{
840 if (!--mp->m_count) {
841 struct dentry *dentry = mp->m_dentry;
842 BUG_ON(!hlist_empty(&mp->m_list));
843 spin_lock(&dentry->d_lock);
844 dentry->d_flags &= ~DCACHE_MOUNTED;
845 spin_unlock(&dentry->d_lock);
846 dput_to_list(dentry, list);
847 hlist_del(&mp->m_hash);
848 kfree(mp);
849 }
850}
851
852/* called with namespace_lock and vfsmount lock */
853static void put_mountpoint(struct mountpoint *mp)
854{
855 __put_mountpoint(mp, &ex_mountpoints);
856}
857
858static inline int check_mnt(struct mount *mnt)
859{
860 return mnt->mnt_ns == current->nsproxy->mnt_ns;
861}
862
863/*
864 * vfsmount lock must be held for write
865 */
866static void touch_mnt_namespace(struct mnt_namespace *ns)
867{
868 if (ns) {
869 ns->event = ++event;
870 wake_up_interruptible(&ns->poll);
871 }
872}
873
874/*
875 * vfsmount lock must be held for write
876 */
877static void __touch_mnt_namespace(struct mnt_namespace *ns)
878{
879 if (ns && ns->event != event) {
880 ns->event = event;
881 wake_up_interruptible(&ns->poll);
882 }
883}
884
885/*
886 * vfsmount lock must be held for write
887 */
888static struct mountpoint *unhash_mnt(struct mount *mnt)
889{
890 struct mountpoint *mp;
891 mnt->mnt_parent = mnt;
892 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
893 list_del_init(&mnt->mnt_child);
894 hlist_del_init_rcu(&mnt->mnt_hash);
895 hlist_del_init(&mnt->mnt_mp_list);
896 mp = mnt->mnt_mp;
897 mnt->mnt_mp = NULL;
898 return mp;
899}
900
901/*
902 * vfsmount lock must be held for write
903 */
904static void umount_mnt(struct mount *mnt)
905{
906 put_mountpoint(unhash_mnt(mnt));
907}
908
909/*
910 * vfsmount lock must be held for write
911 */
912void mnt_set_mountpoint(struct mount *mnt,
913 struct mountpoint *mp,
914 struct mount *child_mnt)
915{
916 mp->m_count++;
917 mnt_add_count(mnt, 1); /* essentially, that's mntget */
918 child_mnt->mnt_mountpoint = mp->m_dentry;
919 child_mnt->mnt_parent = mnt;
920 child_mnt->mnt_mp = mp;
921 hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list);
922}
923
924/**
925 * mnt_set_mountpoint_beneath - mount a mount beneath another one
926 *
927 * @new_parent: the source mount
928 * @top_mnt: the mount beneath which @new_parent is mounted
929 * @new_mp: the new mountpoint of @top_mnt on @new_parent
930 *
931 * Remove @top_mnt from its current mountpoint @top_mnt->mnt_mp and
932 * parent @top_mnt->mnt_parent and mount it on top of @new_parent at
933 * @new_mp. And mount @new_parent on the old parent and old
934 * mountpoint of @top_mnt.
935 *
936 * Context: This function expects namespace_lock() and lock_mount_hash()
937 * to have been acquired in that order.
938 */
939static void mnt_set_mountpoint_beneath(struct mount *new_parent,
940 struct mount *top_mnt,
941 struct mountpoint *new_mp)
942{
943 struct mount *old_top_parent = top_mnt->mnt_parent;
944 struct mountpoint *old_top_mp = top_mnt->mnt_mp;
945
946 mnt_set_mountpoint(old_top_parent, old_top_mp, new_parent);
947 mnt_change_mountpoint(new_parent, new_mp, top_mnt);
948}
949
950
951static void __attach_mnt(struct mount *mnt, struct mount *parent)
952{
953 hlist_add_head_rcu(&mnt->mnt_hash,
954 m_hash(&parent->mnt, mnt->mnt_mountpoint));
955 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
956}
957
958/**
959 * attach_mnt - mount a mount, attach to @mount_hashtable and parent's
960 * list of child mounts
961 * @parent: the parent
962 * @mnt: the new mount
963 * @mp: the new mountpoint
964 * @beneath: whether to mount @mnt beneath or on top of @parent
965 *
966 * If @beneath is false, mount @mnt at @mp on @parent. Then attach @mnt
967 * to @parent's child mount list and to @mount_hashtable.
968 *
969 * If @beneath is true, remove @mnt from its current parent and
970 * mountpoint and mount it on @mp on @parent, and mount @parent on the
971 * old parent and old mountpoint of @mnt. Finally, attach @parent to
972 * @mnt_hashtable and @parent->mnt_parent->mnt_mounts.
973 *
974 * Note, when __attach_mnt() is called @mnt->mnt_parent already points
975 * to the correct parent.
976 *
977 * Context: This function expects namespace_lock() and lock_mount_hash()
978 * to have been acquired in that order.
979 */
980static void attach_mnt(struct mount *mnt, struct mount *parent,
981 struct mountpoint *mp, bool beneath)
982{
983 if (beneath)
984 mnt_set_mountpoint_beneath(mnt, parent, mp);
985 else
986 mnt_set_mountpoint(parent, mp, mnt);
987 /*
988 * Note, @mnt->mnt_parent has to be used. If @mnt was mounted
989 * beneath @parent then @mnt will need to be attached to
990 * @parent's old parent, not @parent. IOW, @mnt->mnt_parent
991 * isn't the same mount as @parent.
992 */
993 __attach_mnt(mnt, mnt->mnt_parent);
994}
995
996void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp, struct mount *mnt)
997{
998 struct mountpoint *old_mp = mnt->mnt_mp;
999 struct mount *old_parent = mnt->mnt_parent;
1000
1001 list_del_init(&mnt->mnt_child);
1002 hlist_del_init(&mnt->mnt_mp_list);
1003 hlist_del_init_rcu(&mnt->mnt_hash);
1004
1005 attach_mnt(mnt, parent, mp, false);
1006
1007 put_mountpoint(old_mp);
1008 mnt_add_count(old_parent, -1);
1009}
1010
1011static inline struct mount *node_to_mount(struct rb_node *node)
1012{
1013 return node ? rb_entry(node, struct mount, mnt_node) : NULL;
1014}
1015
1016static void mnt_add_to_ns(struct mnt_namespace *ns, struct mount *mnt)
1017{
1018 struct rb_node **link = &ns->mounts.rb_node;
1019 struct rb_node *parent = NULL;
1020
1021 WARN_ON(mnt->mnt.mnt_flags & MNT_ONRB);
1022 mnt->mnt_ns = ns;
1023 while (*link) {
1024 parent = *link;
1025 if (mnt->mnt_id_unique < node_to_mount(parent)->mnt_id_unique)
1026 link = &parent->rb_left;
1027 else
1028 link = &parent->rb_right;
1029 }
1030 rb_link_node(&mnt->mnt_node, parent, link);
1031 rb_insert_color(&mnt->mnt_node, &ns->mounts);
1032 mnt->mnt.mnt_flags |= MNT_ONRB;
1033}
1034
1035/*
1036 * vfsmount lock must be held for write
1037 */
1038static void commit_tree(struct mount *mnt)
1039{
1040 struct mount *parent = mnt->mnt_parent;
1041 struct mount *m;
1042 LIST_HEAD(head);
1043 struct mnt_namespace *n = parent->mnt_ns;
1044
1045 BUG_ON(parent == mnt);
1046
1047 list_add_tail(&head, &mnt->mnt_list);
1048 while (!list_empty(&head)) {
1049 m = list_first_entry(&head, typeof(*m), mnt_list);
1050 list_del(&m->mnt_list);
1051
1052 mnt_add_to_ns(n, m);
1053 }
1054 n->nr_mounts += n->pending_mounts;
1055 n->pending_mounts = 0;
1056
1057 __attach_mnt(mnt, parent);
1058 touch_mnt_namespace(n);
1059}
1060
1061static struct mount *next_mnt(struct mount *p, struct mount *root)
1062{
1063 struct list_head *next = p->mnt_mounts.next;
1064 if (next == &p->mnt_mounts) {
1065 while (1) {
1066 if (p == root)
1067 return NULL;
1068 next = p->mnt_child.next;
1069 if (next != &p->mnt_parent->mnt_mounts)
1070 break;
1071 p = p->mnt_parent;
1072 }
1073 }
1074 return list_entry(next, struct mount, mnt_child);
1075}
1076
1077static struct mount *skip_mnt_tree(struct mount *p)
1078{
1079 struct list_head *prev = p->mnt_mounts.prev;
1080 while (prev != &p->mnt_mounts) {
1081 p = list_entry(prev, struct mount, mnt_child);
1082 prev = p->mnt_mounts.prev;
1083 }
1084 return p;
1085}
1086
1087/**
1088 * vfs_create_mount - Create a mount for a configured superblock
1089 * @fc: The configuration context with the superblock attached
1090 *
1091 * Create a mount to an already configured superblock. If necessary, the
1092 * caller should invoke vfs_get_tree() before calling this.
1093 *
1094 * Note that this does not attach the mount to anything.
1095 */
1096struct vfsmount *vfs_create_mount(struct fs_context *fc)
1097{
1098 struct mount *mnt;
1099
1100 if (!fc->root)
1101 return ERR_PTR(-EINVAL);
1102
1103 mnt = alloc_vfsmnt(fc->source ?: "none");
1104 if (!mnt)
1105 return ERR_PTR(-ENOMEM);
1106
1107 if (fc->sb_flags & SB_KERNMOUNT)
1108 mnt->mnt.mnt_flags = MNT_INTERNAL;
1109
1110 atomic_inc(&fc->root->d_sb->s_active);
1111 mnt->mnt.mnt_sb = fc->root->d_sb;
1112 mnt->mnt.mnt_root = dget(fc->root);
1113 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
1114 mnt->mnt_parent = mnt;
1115
1116 lock_mount_hash();
1117 list_add_tail(&mnt->mnt_instance, &mnt->mnt.mnt_sb->s_mounts);
1118 unlock_mount_hash();
1119 return &mnt->mnt;
1120}
1121EXPORT_SYMBOL(vfs_create_mount);
1122
1123struct vfsmount *fc_mount(struct fs_context *fc)
1124{
1125 int err = vfs_get_tree(fc);
1126 if (!err) {
1127 up_write(&fc->root->d_sb->s_umount);
1128 return vfs_create_mount(fc);
1129 }
1130 return ERR_PTR(err);
1131}
1132EXPORT_SYMBOL(fc_mount);
1133
1134struct vfsmount *vfs_kern_mount(struct file_system_type *type,
1135 int flags, const char *name,
1136 void *data)
1137{
1138 struct fs_context *fc;
1139 struct vfsmount *mnt;
1140 int ret = 0;
1141
1142 if (!type)
1143 return ERR_PTR(-EINVAL);
1144
1145 fc = fs_context_for_mount(type, flags);
1146 if (IS_ERR(fc))
1147 return ERR_CAST(fc);
1148
1149 if (name)
1150 ret = vfs_parse_fs_string(fc, "source",
1151 name, strlen(name));
1152 if (!ret)
1153 ret = parse_monolithic_mount_data(fc, data);
1154 if (!ret)
1155 mnt = fc_mount(fc);
1156 else
1157 mnt = ERR_PTR(ret);
1158
1159 put_fs_context(fc);
1160 return mnt;
1161}
1162EXPORT_SYMBOL_GPL(vfs_kern_mount);
1163
1164struct vfsmount *
1165vfs_submount(const struct dentry *mountpoint, struct file_system_type *type,
1166 const char *name, void *data)
1167{
1168 /* Until it is worked out how to pass the user namespace
1169 * through from the parent mount to the submount don't support
1170 * unprivileged mounts with submounts.
1171 */
1172 if (mountpoint->d_sb->s_user_ns != &init_user_ns)
1173 return ERR_PTR(-EPERM);
1174
1175 return vfs_kern_mount(type, SB_SUBMOUNT, name, data);
1176}
1177EXPORT_SYMBOL_GPL(vfs_submount);
1178
1179static struct mount *clone_mnt(struct mount *old, struct dentry *root,
1180 int flag)
1181{
1182 struct super_block *sb = old->mnt.mnt_sb;
1183 struct mount *mnt;
1184 int err;
1185
1186 mnt = alloc_vfsmnt(old->mnt_devname);
1187 if (!mnt)
1188 return ERR_PTR(-ENOMEM);
1189
1190 if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
1191 mnt->mnt_group_id = 0; /* not a peer of original */
1192 else
1193 mnt->mnt_group_id = old->mnt_group_id;
1194
1195 if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
1196 err = mnt_alloc_group_id(mnt);
1197 if (err)
1198 goto out_free;
1199 }
1200
1201 mnt->mnt.mnt_flags = old->mnt.mnt_flags;
1202 mnt->mnt.mnt_flags &= ~(MNT_WRITE_HOLD|MNT_MARKED|MNT_INTERNAL|MNT_ONRB);
1203
1204 atomic_inc(&sb->s_active);
1205 mnt->mnt.mnt_idmap = mnt_idmap_get(mnt_idmap(&old->mnt));
1206
1207 mnt->mnt.mnt_sb = sb;
1208 mnt->mnt.mnt_root = dget(root);
1209 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
1210 mnt->mnt_parent = mnt;
1211 lock_mount_hash();
1212 list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
1213 unlock_mount_hash();
1214
1215 if ((flag & CL_SLAVE) ||
1216 ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
1217 list_add(&mnt->mnt_slave, &old->mnt_slave_list);
1218 mnt->mnt_master = old;
1219 CLEAR_MNT_SHARED(mnt);
1220 } else if (!(flag & CL_PRIVATE)) {
1221 if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
1222 list_add(&mnt->mnt_share, &old->mnt_share);
1223 if (IS_MNT_SLAVE(old))
1224 list_add(&mnt->mnt_slave, &old->mnt_slave);
1225 mnt->mnt_master = old->mnt_master;
1226 } else {
1227 CLEAR_MNT_SHARED(mnt);
1228 }
1229 if (flag & CL_MAKE_SHARED)
1230 set_mnt_shared(mnt);
1231
1232 /* stick the duplicate mount on the same expiry list
1233 * as the original if that was on one */
1234 if (flag & CL_EXPIRE) {
1235 if (!list_empty(&old->mnt_expire))
1236 list_add(&mnt->mnt_expire, &old->mnt_expire);
1237 }
1238
1239 return mnt;
1240
1241 out_free:
1242 mnt_free_id(mnt);
1243 free_vfsmnt(mnt);
1244 return ERR_PTR(err);
1245}
1246
1247static void cleanup_mnt(struct mount *mnt)
1248{
1249 struct hlist_node *p;
1250 struct mount *m;
1251 /*
1252 * The warning here probably indicates that somebody messed
1253 * up a mnt_want/drop_write() pair. If this happens, the
1254 * filesystem was probably unable to make r/w->r/o transitions.
1255 * The locking used to deal with mnt_count decrement provides barriers,
1256 * so mnt_get_writers() below is safe.
1257 */
1258 WARN_ON(mnt_get_writers(mnt));
1259 if (unlikely(mnt->mnt_pins.first))
1260 mnt_pin_kill(mnt);
1261 hlist_for_each_entry_safe(m, p, &mnt->mnt_stuck_children, mnt_umount) {
1262 hlist_del(&m->mnt_umount);
1263 mntput(&m->mnt);
1264 }
1265 fsnotify_vfsmount_delete(&mnt->mnt);
1266 dput(mnt->mnt.mnt_root);
1267 deactivate_super(mnt->mnt.mnt_sb);
1268 mnt_free_id(mnt);
1269 call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt);
1270}
1271
1272static void __cleanup_mnt(struct rcu_head *head)
1273{
1274 cleanup_mnt(container_of(head, struct mount, mnt_rcu));
1275}
1276
1277static LLIST_HEAD(delayed_mntput_list);
1278static void delayed_mntput(struct work_struct *unused)
1279{
1280 struct llist_node *node = llist_del_all(&delayed_mntput_list);
1281 struct mount *m, *t;
1282
1283 llist_for_each_entry_safe(m, t, node, mnt_llist)
1284 cleanup_mnt(m);
1285}
1286static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput);
1287
1288static void mntput_no_expire(struct mount *mnt)
1289{
1290 LIST_HEAD(list);
1291 int count;
1292
1293 rcu_read_lock();
1294 if (likely(READ_ONCE(mnt->mnt_ns))) {
1295 /*
1296 * Since we don't do lock_mount_hash() here,
1297 * ->mnt_ns can change under us. However, if it's
1298 * non-NULL, then there's a reference that won't
1299 * be dropped until after an RCU delay done after
1300 * turning ->mnt_ns NULL. So if we observe it
1301 * non-NULL under rcu_read_lock(), the reference
1302 * we are dropping is not the final one.
1303 */
1304 mnt_add_count(mnt, -1);
1305 rcu_read_unlock();
1306 return;
1307 }
1308 lock_mount_hash();
1309 /*
1310 * make sure that if __legitimize_mnt() has not seen us grab
1311 * mount_lock, we'll see their refcount increment here.
1312 */
1313 smp_mb();
1314 mnt_add_count(mnt, -1);
1315 count = mnt_get_count(mnt);
1316 if (count != 0) {
1317 WARN_ON(count < 0);
1318 rcu_read_unlock();
1319 unlock_mount_hash();
1320 return;
1321 }
1322 if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) {
1323 rcu_read_unlock();
1324 unlock_mount_hash();
1325 return;
1326 }
1327 mnt->mnt.mnt_flags |= MNT_DOOMED;
1328 rcu_read_unlock();
1329
1330 list_del(&mnt->mnt_instance);
1331
1332 if (unlikely(!list_empty(&mnt->mnt_mounts))) {
1333 struct mount *p, *tmp;
1334 list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) {
1335 __put_mountpoint(unhash_mnt(p), &list);
1336 hlist_add_head(&p->mnt_umount, &mnt->mnt_stuck_children);
1337 }
1338 }
1339 unlock_mount_hash();
1340 shrink_dentry_list(&list);
1341
1342 if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) {
1343 struct task_struct *task = current;
1344 if (likely(!(task->flags & PF_KTHREAD))) {
1345 init_task_work(&mnt->mnt_rcu, __cleanup_mnt);
1346 if (!task_work_add(task, &mnt->mnt_rcu, TWA_RESUME))
1347 return;
1348 }
1349 if (llist_add(&mnt->mnt_llist, &delayed_mntput_list))
1350 schedule_delayed_work(&delayed_mntput_work, 1);
1351 return;
1352 }
1353 cleanup_mnt(mnt);
1354}
1355
1356void mntput(struct vfsmount *mnt)
1357{
1358 if (mnt) {
1359 struct mount *m = real_mount(mnt);
1360 /* avoid cacheline pingpong */
1361 if (unlikely(m->mnt_expiry_mark))
1362 WRITE_ONCE(m->mnt_expiry_mark, 0);
1363 mntput_no_expire(m);
1364 }
1365}
1366EXPORT_SYMBOL(mntput);
1367
1368struct vfsmount *mntget(struct vfsmount *mnt)
1369{
1370 if (mnt)
1371 mnt_add_count(real_mount(mnt), 1);
1372 return mnt;
1373}
1374EXPORT_SYMBOL(mntget);
1375
1376/*
1377 * Make a mount point inaccessible to new lookups.
1378 * Because there may still be current users, the caller MUST WAIT
1379 * for an RCU grace period before destroying the mount point.
1380 */
1381void mnt_make_shortterm(struct vfsmount *mnt)
1382{
1383 if (mnt)
1384 real_mount(mnt)->mnt_ns = NULL;
1385}
1386
1387/**
1388 * path_is_mountpoint() - Check if path is a mount in the current namespace.
1389 * @path: path to check
1390 *
1391 * d_mountpoint() can only be used reliably to establish if a dentry is
1392 * not mounted in any namespace and that common case is handled inline.
1393 * d_mountpoint() isn't aware of the possibility there may be multiple
1394 * mounts using a given dentry in a different namespace. This function
1395 * checks if the passed in path is a mountpoint rather than the dentry
1396 * alone.
1397 */
1398bool path_is_mountpoint(const struct path *path)
1399{
1400 unsigned seq;
1401 bool res;
1402
1403 if (!d_mountpoint(path->dentry))
1404 return false;
1405
1406 rcu_read_lock();
1407 do {
1408 seq = read_seqbegin(&mount_lock);
1409 res = __path_is_mountpoint(path);
1410 } while (read_seqretry(&mount_lock, seq));
1411 rcu_read_unlock();
1412
1413 return res;
1414}
1415EXPORT_SYMBOL(path_is_mountpoint);
1416
1417struct vfsmount *mnt_clone_internal(const struct path *path)
1418{
1419 struct mount *p;
1420 p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE);
1421 if (IS_ERR(p))
1422 return ERR_CAST(p);
1423 p->mnt.mnt_flags |= MNT_INTERNAL;
1424 return &p->mnt;
1425}
1426
1427/*
1428 * Returns the mount which either has the specified mnt_id, or has the next
1429 * smallest id afer the specified one.
1430 */
1431static struct mount *mnt_find_id_at(struct mnt_namespace *ns, u64 mnt_id)
1432{
1433 struct rb_node *node = ns->mounts.rb_node;
1434 struct mount *ret = NULL;
1435
1436 while (node) {
1437 struct mount *m = node_to_mount(node);
1438
1439 if (mnt_id <= m->mnt_id_unique) {
1440 ret = node_to_mount(node);
1441 if (mnt_id == m->mnt_id_unique)
1442 break;
1443 node = node->rb_left;
1444 } else {
1445 node = node->rb_right;
1446 }
1447 }
1448 return ret;
1449}
1450
1451#ifdef CONFIG_PROC_FS
1452
1453/* iterator; we want it to have access to namespace_sem, thus here... */
1454static void *m_start(struct seq_file *m, loff_t *pos)
1455{
1456 struct proc_mounts *p = m->private;
1457
1458 down_read(&namespace_sem);
1459
1460 return mnt_find_id_at(p->ns, *pos);
1461}
1462
1463static void *m_next(struct seq_file *m, void *v, loff_t *pos)
1464{
1465 struct mount *next = NULL, *mnt = v;
1466 struct rb_node *node = rb_next(&mnt->mnt_node);
1467
1468 ++*pos;
1469 if (node) {
1470 next = node_to_mount(node);
1471 *pos = next->mnt_id_unique;
1472 }
1473 return next;
1474}
1475
1476static void m_stop(struct seq_file *m, void *v)
1477{
1478 up_read(&namespace_sem);
1479}
1480
1481static int m_show(struct seq_file *m, void *v)
1482{
1483 struct proc_mounts *p = m->private;
1484 struct mount *r = v;
1485 return p->show(m, &r->mnt);
1486}
1487
1488const struct seq_operations mounts_op = {
1489 .start = m_start,
1490 .next = m_next,
1491 .stop = m_stop,
1492 .show = m_show,
1493};
1494
1495#endif /* CONFIG_PROC_FS */
1496
1497/**
1498 * may_umount_tree - check if a mount tree is busy
1499 * @m: root of mount tree
1500 *
1501 * This is called to check if a tree of mounts has any
1502 * open files, pwds, chroots or sub mounts that are
1503 * busy.
1504 */
1505int may_umount_tree(struct vfsmount *m)
1506{
1507 struct mount *mnt = real_mount(m);
1508 int actual_refs = 0;
1509 int minimum_refs = 0;
1510 struct mount *p;
1511 BUG_ON(!m);
1512
1513 /* write lock needed for mnt_get_count */
1514 lock_mount_hash();
1515 for (p = mnt; p; p = next_mnt(p, mnt)) {
1516 actual_refs += mnt_get_count(p);
1517 minimum_refs += 2;
1518 }
1519 unlock_mount_hash();
1520
1521 if (actual_refs > minimum_refs)
1522 return 0;
1523
1524 return 1;
1525}
1526
1527EXPORT_SYMBOL(may_umount_tree);
1528
1529/**
1530 * may_umount - check if a mount point is busy
1531 * @mnt: root of mount
1532 *
1533 * This is called to check if a mount point has any
1534 * open files, pwds, chroots or sub mounts. If the
1535 * mount has sub mounts this will return busy
1536 * regardless of whether the sub mounts are busy.
1537 *
1538 * Doesn't take quota and stuff into account. IOW, in some cases it will
1539 * give false negatives. The main reason why it's here is that we need
1540 * a non-destructive way to look for easily umountable filesystems.
1541 */
1542int may_umount(struct vfsmount *mnt)
1543{
1544 int ret = 1;
1545 down_read(&namespace_sem);
1546 lock_mount_hash();
1547 if (propagate_mount_busy(real_mount(mnt), 2))
1548 ret = 0;
1549 unlock_mount_hash();
1550 up_read(&namespace_sem);
1551 return ret;
1552}
1553
1554EXPORT_SYMBOL(may_umount);
1555
1556static void namespace_unlock(void)
1557{
1558 struct hlist_head head;
1559 struct hlist_node *p;
1560 struct mount *m;
1561 LIST_HEAD(list);
1562
1563 hlist_move_list(&unmounted, &head);
1564 list_splice_init(&ex_mountpoints, &list);
1565
1566 up_write(&namespace_sem);
1567
1568 shrink_dentry_list(&list);
1569
1570 if (likely(hlist_empty(&head)))
1571 return;
1572
1573 synchronize_rcu_expedited();
1574
1575 hlist_for_each_entry_safe(m, p, &head, mnt_umount) {
1576 hlist_del(&m->mnt_umount);
1577 mntput(&m->mnt);
1578 }
1579}
1580
1581static inline void namespace_lock(void)
1582{
1583 down_write(&namespace_sem);
1584}
1585
1586enum umount_tree_flags {
1587 UMOUNT_SYNC = 1,
1588 UMOUNT_PROPAGATE = 2,
1589 UMOUNT_CONNECTED = 4,
1590};
1591
1592static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how)
1593{
1594 /* Leaving mounts connected is only valid for lazy umounts */
1595 if (how & UMOUNT_SYNC)
1596 return true;
1597
1598 /* A mount without a parent has nothing to be connected to */
1599 if (!mnt_has_parent(mnt))
1600 return true;
1601
1602 /* Because the reference counting rules change when mounts are
1603 * unmounted and connected, umounted mounts may not be
1604 * connected to mounted mounts.
1605 */
1606 if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT))
1607 return true;
1608
1609 /* Has it been requested that the mount remain connected? */
1610 if (how & UMOUNT_CONNECTED)
1611 return false;
1612
1613 /* Is the mount locked such that it needs to remain connected? */
1614 if (IS_MNT_LOCKED(mnt))
1615 return false;
1616
1617 /* By default disconnect the mount */
1618 return true;
1619}
1620
1621/*
1622 * mount_lock must be held
1623 * namespace_sem must be held for write
1624 */
1625static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
1626{
1627 LIST_HEAD(tmp_list);
1628 struct mount *p;
1629
1630 if (how & UMOUNT_PROPAGATE)
1631 propagate_mount_unlock(mnt);
1632
1633 /* Gather the mounts to umount */
1634 for (p = mnt; p; p = next_mnt(p, mnt)) {
1635 p->mnt.mnt_flags |= MNT_UMOUNT;
1636 if (p->mnt.mnt_flags & MNT_ONRB)
1637 move_from_ns(p, &tmp_list);
1638 else
1639 list_move(&p->mnt_list, &tmp_list);
1640 }
1641
1642 /* Hide the mounts from mnt_mounts */
1643 list_for_each_entry(p, &tmp_list, mnt_list) {
1644 list_del_init(&p->mnt_child);
1645 }
1646
1647 /* Add propogated mounts to the tmp_list */
1648 if (how & UMOUNT_PROPAGATE)
1649 propagate_umount(&tmp_list);
1650
1651 while (!list_empty(&tmp_list)) {
1652 struct mnt_namespace *ns;
1653 bool disconnect;
1654 p = list_first_entry(&tmp_list, struct mount, mnt_list);
1655 list_del_init(&p->mnt_expire);
1656 list_del_init(&p->mnt_list);
1657 ns = p->mnt_ns;
1658 if (ns) {
1659 ns->nr_mounts--;
1660 __touch_mnt_namespace(ns);
1661 }
1662 p->mnt_ns = NULL;
1663 if (how & UMOUNT_SYNC)
1664 p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
1665
1666 disconnect = disconnect_mount(p, how);
1667 if (mnt_has_parent(p)) {
1668 mnt_add_count(p->mnt_parent, -1);
1669 if (!disconnect) {
1670 /* Don't forget about p */
1671 list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts);
1672 } else {
1673 umount_mnt(p);
1674 }
1675 }
1676 change_mnt_propagation(p, MS_PRIVATE);
1677 if (disconnect)
1678 hlist_add_head(&p->mnt_umount, &unmounted);
1679 }
1680}
1681
1682static void shrink_submounts(struct mount *mnt);
1683
1684static int do_umount_root(struct super_block *sb)
1685{
1686 int ret = 0;
1687
1688 down_write(&sb->s_umount);
1689 if (!sb_rdonly(sb)) {
1690 struct fs_context *fc;
1691
1692 fc = fs_context_for_reconfigure(sb->s_root, SB_RDONLY,
1693 SB_RDONLY);
1694 if (IS_ERR(fc)) {
1695 ret = PTR_ERR(fc);
1696 } else {
1697 ret = parse_monolithic_mount_data(fc, NULL);
1698 if (!ret)
1699 ret = reconfigure_super(fc);
1700 put_fs_context(fc);
1701 }
1702 }
1703 up_write(&sb->s_umount);
1704 return ret;
1705}
1706
1707static int do_umount(struct mount *mnt, int flags)
1708{
1709 struct super_block *sb = mnt->mnt.mnt_sb;
1710 int retval;
1711
1712 retval = security_sb_umount(&mnt->mnt, flags);
1713 if (retval)
1714 return retval;
1715
1716 /*
1717 * Allow userspace to request a mountpoint be expired rather than
1718 * unmounting unconditionally. Unmount only happens if:
1719 * (1) the mark is already set (the mark is cleared by mntput())
1720 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1721 */
1722 if (flags & MNT_EXPIRE) {
1723 if (&mnt->mnt == current->fs->root.mnt ||
1724 flags & (MNT_FORCE | MNT_DETACH))
1725 return -EINVAL;
1726
1727 /*
1728 * probably don't strictly need the lock here if we examined
1729 * all race cases, but it's a slowpath.
1730 */
1731 lock_mount_hash();
1732 if (mnt_get_count(mnt) != 2) {
1733 unlock_mount_hash();
1734 return -EBUSY;
1735 }
1736 unlock_mount_hash();
1737
1738 if (!xchg(&mnt->mnt_expiry_mark, 1))
1739 return -EAGAIN;
1740 }
1741
1742 /*
1743 * If we may have to abort operations to get out of this
1744 * mount, and they will themselves hold resources we must
1745 * allow the fs to do things. In the Unix tradition of
1746 * 'Gee thats tricky lets do it in userspace' the umount_begin
1747 * might fail to complete on the first run through as other tasks
1748 * must return, and the like. Thats for the mount program to worry
1749 * about for the moment.
1750 */
1751
1752 if (flags & MNT_FORCE && sb->s_op->umount_begin) {
1753 sb->s_op->umount_begin(sb);
1754 }
1755
1756 /*
1757 * No sense to grab the lock for this test, but test itself looks
1758 * somewhat bogus. Suggestions for better replacement?
1759 * Ho-hum... In principle, we might treat that as umount + switch
1760 * to rootfs. GC would eventually take care of the old vfsmount.
1761 * Actually it makes sense, especially if rootfs would contain a
1762 * /reboot - static binary that would close all descriptors and
1763 * call reboot(9). Then init(8) could umount root and exec /reboot.
1764 */
1765 if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
1766 /*
1767 * Special case for "unmounting" root ...
1768 * we just try to remount it readonly.
1769 */
1770 if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN))
1771 return -EPERM;
1772 return do_umount_root(sb);
1773 }
1774
1775 namespace_lock();
1776 lock_mount_hash();
1777
1778 /* Recheck MNT_LOCKED with the locks held */
1779 retval = -EINVAL;
1780 if (mnt->mnt.mnt_flags & MNT_LOCKED)
1781 goto out;
1782
1783 event++;
1784 if (flags & MNT_DETACH) {
1785 if (mnt->mnt.mnt_flags & MNT_ONRB ||
1786 !list_empty(&mnt->mnt_list))
1787 umount_tree(mnt, UMOUNT_PROPAGATE);
1788 retval = 0;
1789 } else {
1790 shrink_submounts(mnt);
1791 retval = -EBUSY;
1792 if (!propagate_mount_busy(mnt, 2)) {
1793 if (mnt->mnt.mnt_flags & MNT_ONRB ||
1794 !list_empty(&mnt->mnt_list))
1795 umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
1796 retval = 0;
1797 }
1798 }
1799out:
1800 unlock_mount_hash();
1801 namespace_unlock();
1802 return retval;
1803}
1804
1805/*
1806 * __detach_mounts - lazily unmount all mounts on the specified dentry
1807 *
1808 * During unlink, rmdir, and d_drop it is possible to loose the path
1809 * to an existing mountpoint, and wind up leaking the mount.
1810 * detach_mounts allows lazily unmounting those mounts instead of
1811 * leaking them.
1812 *
1813 * The caller may hold dentry->d_inode->i_mutex.
1814 */
1815void __detach_mounts(struct dentry *dentry)
1816{
1817 struct mountpoint *mp;
1818 struct mount *mnt;
1819
1820 namespace_lock();
1821 lock_mount_hash();
1822 mp = lookup_mountpoint(dentry);
1823 if (!mp)
1824 goto out_unlock;
1825
1826 event++;
1827 while (!hlist_empty(&mp->m_list)) {
1828 mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list);
1829 if (mnt->mnt.mnt_flags & MNT_UMOUNT) {
1830 umount_mnt(mnt);
1831 hlist_add_head(&mnt->mnt_umount, &unmounted);
1832 }
1833 else umount_tree(mnt, UMOUNT_CONNECTED);
1834 }
1835 put_mountpoint(mp);
1836out_unlock:
1837 unlock_mount_hash();
1838 namespace_unlock();
1839}
1840
1841/*
1842 * Is the caller allowed to modify his namespace?
1843 */
1844bool may_mount(void)
1845{
1846 return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
1847}
1848
1849/**
1850 * path_mounted - check whether path is mounted
1851 * @path: path to check
1852 *
1853 * Determine whether @path refers to the root of a mount.
1854 *
1855 * Return: true if @path is the root of a mount, false if not.
1856 */
1857static inline bool path_mounted(const struct path *path)
1858{
1859 return path->mnt->mnt_root == path->dentry;
1860}
1861
1862static void warn_mandlock(void)
1863{
1864 pr_warn_once("=======================================================\n"
1865 "WARNING: The mand mount option has been deprecated and\n"
1866 " and is ignored by this kernel. Remove the mand\n"
1867 " option from the mount to silence this warning.\n"
1868 "=======================================================\n");
1869}
1870
1871static int can_umount(const struct path *path, int flags)
1872{
1873 struct mount *mnt = real_mount(path->mnt);
1874
1875 if (!may_mount())
1876 return -EPERM;
1877 if (!path_mounted(path))
1878 return -EINVAL;
1879 if (!check_mnt(mnt))
1880 return -EINVAL;
1881 if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */
1882 return -EINVAL;
1883 if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))
1884 return -EPERM;
1885 return 0;
1886}
1887
1888// caller is responsible for flags being sane
1889int path_umount(struct path *path, int flags)
1890{
1891 struct mount *mnt = real_mount(path->mnt);
1892 int ret;
1893
1894 ret = can_umount(path, flags);
1895 if (!ret)
1896 ret = do_umount(mnt, flags);
1897
1898 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1899 dput(path->dentry);
1900 mntput_no_expire(mnt);
1901 return ret;
1902}
1903
1904static int ksys_umount(char __user *name, int flags)
1905{
1906 int lookup_flags = LOOKUP_MOUNTPOINT;
1907 struct path path;
1908 int ret;
1909
1910 // basic validity checks done first
1911 if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
1912 return -EINVAL;
1913
1914 if (!(flags & UMOUNT_NOFOLLOW))
1915 lookup_flags |= LOOKUP_FOLLOW;
1916 ret = user_path_at(AT_FDCWD, name, lookup_flags, &path);
1917 if (ret)
1918 return ret;
1919 return path_umount(&path, flags);
1920}
1921
1922SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1923{
1924 return ksys_umount(name, flags);
1925}
1926
1927#ifdef __ARCH_WANT_SYS_OLDUMOUNT
1928
1929/*
1930 * The 2.0 compatible umount. No flags.
1931 */
1932SYSCALL_DEFINE1(oldumount, char __user *, name)
1933{
1934 return ksys_umount(name, 0);
1935}
1936
1937#endif
1938
1939static bool is_mnt_ns_file(struct dentry *dentry)
1940{
1941 /* Is this a proxy for a mount namespace? */
1942 return dentry->d_op == &ns_dentry_operations &&
1943 dentry->d_fsdata == &mntns_operations;
1944}
1945
1946static struct mnt_namespace *to_mnt_ns(struct ns_common *ns)
1947{
1948 return container_of(ns, struct mnt_namespace, ns);
1949}
1950
1951struct ns_common *from_mnt_ns(struct mnt_namespace *mnt)
1952{
1953 return &mnt->ns;
1954}
1955
1956static bool mnt_ns_loop(struct dentry *dentry)
1957{
1958 /* Could bind mounting the mount namespace inode cause a
1959 * mount namespace loop?
1960 */
1961 struct mnt_namespace *mnt_ns;
1962 if (!is_mnt_ns_file(dentry))
1963 return false;
1964
1965 mnt_ns = to_mnt_ns(get_proc_ns(dentry->d_inode));
1966 return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
1967}
1968
1969struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
1970 int flag)
1971{
1972 struct mount *res, *p, *q, *r, *parent;
1973
1974 if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt))
1975 return ERR_PTR(-EINVAL);
1976
1977 if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
1978 return ERR_PTR(-EINVAL);
1979
1980 res = q = clone_mnt(mnt, dentry, flag);
1981 if (IS_ERR(q))
1982 return q;
1983
1984 q->mnt_mountpoint = mnt->mnt_mountpoint;
1985
1986 p = mnt;
1987 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
1988 struct mount *s;
1989 if (!is_subdir(r->mnt_mountpoint, dentry))
1990 continue;
1991
1992 for (s = r; s; s = next_mnt(s, r)) {
1993 if (!(flag & CL_COPY_UNBINDABLE) &&
1994 IS_MNT_UNBINDABLE(s)) {
1995 if (s->mnt.mnt_flags & MNT_LOCKED) {
1996 /* Both unbindable and locked. */
1997 q = ERR_PTR(-EPERM);
1998 goto out;
1999 } else {
2000 s = skip_mnt_tree(s);
2001 continue;
2002 }
2003 }
2004 if (!(flag & CL_COPY_MNT_NS_FILE) &&
2005 is_mnt_ns_file(s->mnt.mnt_root)) {
2006 s = skip_mnt_tree(s);
2007 continue;
2008 }
2009 while (p != s->mnt_parent) {
2010 p = p->mnt_parent;
2011 q = q->mnt_parent;
2012 }
2013 p = s;
2014 parent = q;
2015 q = clone_mnt(p, p->mnt.mnt_root, flag);
2016 if (IS_ERR(q))
2017 goto out;
2018 lock_mount_hash();
2019 list_add_tail(&q->mnt_list, &res->mnt_list);
2020 attach_mnt(q, parent, p->mnt_mp, false);
2021 unlock_mount_hash();
2022 }
2023 }
2024 return res;
2025out:
2026 if (res) {
2027 lock_mount_hash();
2028 umount_tree(res, UMOUNT_SYNC);
2029 unlock_mount_hash();
2030 }
2031 return q;
2032}
2033
2034/* Caller should check returned pointer for errors */
2035
2036struct vfsmount *collect_mounts(const struct path *path)
2037{
2038 struct mount *tree;
2039 namespace_lock();
2040 if (!check_mnt(real_mount(path->mnt)))
2041 tree = ERR_PTR(-EINVAL);
2042 else
2043 tree = copy_tree(real_mount(path->mnt), path->dentry,
2044 CL_COPY_ALL | CL_PRIVATE);
2045 namespace_unlock();
2046 if (IS_ERR(tree))
2047 return ERR_CAST(tree);
2048 return &tree->mnt;
2049}
2050
2051static void free_mnt_ns(struct mnt_namespace *);
2052static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *, bool);
2053
2054void dissolve_on_fput(struct vfsmount *mnt)
2055{
2056 struct mnt_namespace *ns;
2057 namespace_lock();
2058 lock_mount_hash();
2059 ns = real_mount(mnt)->mnt_ns;
2060 if (ns) {
2061 if (is_anon_ns(ns))
2062 umount_tree(real_mount(mnt), UMOUNT_CONNECTED);
2063 else
2064 ns = NULL;
2065 }
2066 unlock_mount_hash();
2067 namespace_unlock();
2068 if (ns)
2069 free_mnt_ns(ns);
2070}
2071
2072void drop_collected_mounts(struct vfsmount *mnt)
2073{
2074 namespace_lock();
2075 lock_mount_hash();
2076 umount_tree(real_mount(mnt), 0);
2077 unlock_mount_hash();
2078 namespace_unlock();
2079}
2080
2081static bool has_locked_children(struct mount *mnt, struct dentry *dentry)
2082{
2083 struct mount *child;
2084
2085 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
2086 if (!is_subdir(child->mnt_mountpoint, dentry))
2087 continue;
2088
2089 if (child->mnt.mnt_flags & MNT_LOCKED)
2090 return true;
2091 }
2092 return false;
2093}
2094
2095/**
2096 * clone_private_mount - create a private clone of a path
2097 * @path: path to clone
2098 *
2099 * This creates a new vfsmount, which will be the clone of @path. The new mount
2100 * will not be attached anywhere in the namespace and will be private (i.e.
2101 * changes to the originating mount won't be propagated into this).
2102 *
2103 * Release with mntput().
2104 */
2105struct vfsmount *clone_private_mount(const struct path *path)
2106{
2107 struct mount *old_mnt = real_mount(path->mnt);
2108 struct mount *new_mnt;
2109
2110 down_read(&namespace_sem);
2111 if (IS_MNT_UNBINDABLE(old_mnt))
2112 goto invalid;
2113
2114 if (!check_mnt(old_mnt))
2115 goto invalid;
2116
2117 if (has_locked_children(old_mnt, path->dentry))
2118 goto invalid;
2119
2120 new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE);
2121 up_read(&namespace_sem);
2122
2123 if (IS_ERR(new_mnt))
2124 return ERR_CAST(new_mnt);
2125
2126 /* Longterm mount to be removed by kern_unmount*() */
2127 new_mnt->mnt_ns = MNT_NS_INTERNAL;
2128
2129 return &new_mnt->mnt;
2130
2131invalid:
2132 up_read(&namespace_sem);
2133 return ERR_PTR(-EINVAL);
2134}
2135EXPORT_SYMBOL_GPL(clone_private_mount);
2136
2137int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
2138 struct vfsmount *root)
2139{
2140 struct mount *mnt;
2141 int res = f(root, arg);
2142 if (res)
2143 return res;
2144 list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
2145 res = f(&mnt->mnt, arg);
2146 if (res)
2147 return res;
2148 }
2149 return 0;
2150}
2151
2152static void lock_mnt_tree(struct mount *mnt)
2153{
2154 struct mount *p;
2155
2156 for (p = mnt; p; p = next_mnt(p, mnt)) {
2157 int flags = p->mnt.mnt_flags;
2158 /* Don't allow unprivileged users to change mount flags */
2159 flags |= MNT_LOCK_ATIME;
2160
2161 if (flags & MNT_READONLY)
2162 flags |= MNT_LOCK_READONLY;
2163
2164 if (flags & MNT_NODEV)
2165 flags |= MNT_LOCK_NODEV;
2166
2167 if (flags & MNT_NOSUID)
2168 flags |= MNT_LOCK_NOSUID;
2169
2170 if (flags & MNT_NOEXEC)
2171 flags |= MNT_LOCK_NOEXEC;
2172 /* Don't allow unprivileged users to reveal what is under a mount */
2173 if (list_empty(&p->mnt_expire))
2174 flags |= MNT_LOCKED;
2175 p->mnt.mnt_flags = flags;
2176 }
2177}
2178
2179static void cleanup_group_ids(struct mount *mnt, struct mount *end)
2180{
2181 struct mount *p;
2182
2183 for (p = mnt; p != end; p = next_mnt(p, mnt)) {
2184 if (p->mnt_group_id && !IS_MNT_SHARED(p))
2185 mnt_release_group_id(p);
2186 }
2187}
2188
2189static int invent_group_ids(struct mount *mnt, bool recurse)
2190{
2191 struct mount *p;
2192
2193 for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
2194 if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
2195 int err = mnt_alloc_group_id(p);
2196 if (err) {
2197 cleanup_group_ids(mnt, p);
2198 return err;
2199 }
2200 }
2201 }
2202
2203 return 0;
2204}
2205
2206int count_mounts(struct mnt_namespace *ns, struct mount *mnt)
2207{
2208 unsigned int max = READ_ONCE(sysctl_mount_max);
2209 unsigned int mounts = 0;
2210 struct mount *p;
2211
2212 if (ns->nr_mounts >= max)
2213 return -ENOSPC;
2214 max -= ns->nr_mounts;
2215 if (ns->pending_mounts >= max)
2216 return -ENOSPC;
2217 max -= ns->pending_mounts;
2218
2219 for (p = mnt; p; p = next_mnt(p, mnt))
2220 mounts++;
2221
2222 if (mounts > max)
2223 return -ENOSPC;
2224
2225 ns->pending_mounts += mounts;
2226 return 0;
2227}
2228
2229enum mnt_tree_flags_t {
2230 MNT_TREE_MOVE = BIT(0),
2231 MNT_TREE_BENEATH = BIT(1),
2232};
2233
2234/**
2235 * attach_recursive_mnt - attach a source mount tree
2236 * @source_mnt: mount tree to be attached
2237 * @top_mnt: mount that @source_mnt will be mounted on or mounted beneath
2238 * @dest_mp: the mountpoint @source_mnt will be mounted at
2239 * @flags: modify how @source_mnt is supposed to be attached
2240 *
2241 * NOTE: in the table below explains the semantics when a source mount
2242 * of a given type is attached to a destination mount of a given type.
2243 * ---------------------------------------------------------------------------
2244 * | BIND MOUNT OPERATION |
2245 * |**************************************************************************
2246 * | source-->| shared | private | slave | unbindable |
2247 * | dest | | | | |
2248 * | | | | | | |
2249 * | v | | | | |
2250 * |**************************************************************************
2251 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
2252 * | | | | | |
2253 * |non-shared| shared (+) | private | slave (*) | invalid |
2254 * ***************************************************************************
2255 * A bind operation clones the source mount and mounts the clone on the
2256 * destination mount.
2257 *
2258 * (++) the cloned mount is propagated to all the mounts in the propagation
2259 * tree of the destination mount and the cloned mount is added to
2260 * the peer group of the source mount.
2261 * (+) the cloned mount is created under the destination mount and is marked
2262 * as shared. The cloned mount is added to the peer group of the source
2263 * mount.
2264 * (+++) the mount is propagated to all the mounts in the propagation tree
2265 * of the destination mount and the cloned mount is made slave
2266 * of the same master as that of the source mount. The cloned mount
2267 * is marked as 'shared and slave'.
2268 * (*) the cloned mount is made a slave of the same master as that of the
2269 * source mount.
2270 *
2271 * ---------------------------------------------------------------------------
2272 * | MOVE MOUNT OPERATION |
2273 * |**************************************************************************
2274 * | source-->| shared | private | slave | unbindable |
2275 * | dest | | | | |
2276 * | | | | | | |
2277 * | v | | | | |
2278 * |**************************************************************************
2279 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
2280 * | | | | | |
2281 * |non-shared| shared (+*) | private | slave (*) | unbindable |
2282 * ***************************************************************************
2283 *
2284 * (+) the mount is moved to the destination. And is then propagated to
2285 * all the mounts in the propagation tree of the destination mount.
2286 * (+*) the mount is moved to the destination.
2287 * (+++) the mount is moved to the destination and is then propagated to
2288 * all the mounts belonging to the destination mount's propagation tree.
2289 * the mount is marked as 'shared and slave'.
2290 * (*) the mount continues to be a slave at the new location.
2291 *
2292 * if the source mount is a tree, the operations explained above is
2293 * applied to each mount in the tree.
2294 * Must be called without spinlocks held, since this function can sleep
2295 * in allocations.
2296 *
2297 * Context: The function expects namespace_lock() to be held.
2298 * Return: If @source_mnt was successfully attached 0 is returned.
2299 * Otherwise a negative error code is returned.
2300 */
2301static int attach_recursive_mnt(struct mount *source_mnt,
2302 struct mount *top_mnt,
2303 struct mountpoint *dest_mp,
2304 enum mnt_tree_flags_t flags)
2305{
2306 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2307 HLIST_HEAD(tree_list);
2308 struct mnt_namespace *ns = top_mnt->mnt_ns;
2309 struct mountpoint *smp;
2310 struct mount *child, *dest_mnt, *p;
2311 struct hlist_node *n;
2312 int err = 0;
2313 bool moving = flags & MNT_TREE_MOVE, beneath = flags & MNT_TREE_BENEATH;
2314
2315 /*
2316 * Preallocate a mountpoint in case the new mounts need to be
2317 * mounted beneath mounts on the same mountpoint.
2318 */
2319 smp = get_mountpoint(source_mnt->mnt.mnt_root);
2320 if (IS_ERR(smp))
2321 return PTR_ERR(smp);
2322
2323 /* Is there space to add these mounts to the mount namespace? */
2324 if (!moving) {
2325 err = count_mounts(ns, source_mnt);
2326 if (err)
2327 goto out;
2328 }
2329
2330 if (beneath)
2331 dest_mnt = top_mnt->mnt_parent;
2332 else
2333 dest_mnt = top_mnt;
2334
2335 if (IS_MNT_SHARED(dest_mnt)) {
2336 err = invent_group_ids(source_mnt, true);
2337 if (err)
2338 goto out;
2339 err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
2340 }
2341 lock_mount_hash();
2342 if (err)
2343 goto out_cleanup_ids;
2344
2345 if (IS_MNT_SHARED(dest_mnt)) {
2346 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
2347 set_mnt_shared(p);
2348 }
2349
2350 if (moving) {
2351 if (beneath)
2352 dest_mp = smp;
2353 unhash_mnt(source_mnt);
2354 attach_mnt(source_mnt, top_mnt, dest_mp, beneath);
2355 touch_mnt_namespace(source_mnt->mnt_ns);
2356 } else {
2357 if (source_mnt->mnt_ns) {
2358 LIST_HEAD(head);
2359
2360 /* move from anon - the caller will destroy */
2361 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
2362 move_from_ns(p, &head);
2363 list_del_init(&head);
2364 }
2365 if (beneath)
2366 mnt_set_mountpoint_beneath(source_mnt, top_mnt, smp);
2367 else
2368 mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
2369 commit_tree(source_mnt);
2370 }
2371
2372 hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) {
2373 struct mount *q;
2374 hlist_del_init(&child->mnt_hash);
2375 q = __lookup_mnt(&child->mnt_parent->mnt,
2376 child->mnt_mountpoint);
2377 if (q)
2378 mnt_change_mountpoint(child, smp, q);
2379 /* Notice when we are propagating across user namespaces */
2380 if (child->mnt_parent->mnt_ns->user_ns != user_ns)
2381 lock_mnt_tree(child);
2382 child->mnt.mnt_flags &= ~MNT_LOCKED;
2383 commit_tree(child);
2384 }
2385 put_mountpoint(smp);
2386 unlock_mount_hash();
2387
2388 return 0;
2389
2390 out_cleanup_ids:
2391 while (!hlist_empty(&tree_list)) {
2392 child = hlist_entry(tree_list.first, struct mount, mnt_hash);
2393 child->mnt_parent->mnt_ns->pending_mounts = 0;
2394 umount_tree(child, UMOUNT_SYNC);
2395 }
2396 unlock_mount_hash();
2397 cleanup_group_ids(source_mnt, NULL);
2398 out:
2399 ns->pending_mounts = 0;
2400
2401 read_seqlock_excl(&mount_lock);
2402 put_mountpoint(smp);
2403 read_sequnlock_excl(&mount_lock);
2404
2405 return err;
2406}
2407
2408/**
2409 * do_lock_mount - lock mount and mountpoint
2410 * @path: target path
2411 * @beneath: whether the intention is to mount beneath @path
2412 *
2413 * Follow the mount stack on @path until the top mount @mnt is found. If
2414 * the initial @path->{mnt,dentry} is a mountpoint lookup the first
2415 * mount stacked on top of it. Then simply follow @{mnt,mnt->mnt_root}
2416 * until nothing is stacked on top of it anymore.
2417 *
2418 * Acquire the inode_lock() on the top mount's ->mnt_root to protect
2419 * against concurrent removal of the new mountpoint from another mount
2420 * namespace.
2421 *
2422 * If @beneath is requested, acquire inode_lock() on @mnt's mountpoint
2423 * @mp on @mnt->mnt_parent must be acquired. This protects against a
2424 * concurrent unlink of @mp->mnt_dentry from another mount namespace
2425 * where @mnt doesn't have a child mount mounted @mp. A concurrent
2426 * removal of @mnt->mnt_root doesn't matter as nothing will be mounted
2427 * on top of it for @beneath.
2428 *
2429 * In addition, @beneath needs to make sure that @mnt hasn't been
2430 * unmounted or moved from its current mountpoint in between dropping
2431 * @mount_lock and acquiring @namespace_sem. For the !@beneath case @mnt
2432 * being unmounted would be detected later by e.g., calling
2433 * check_mnt(mnt) in the function it's called from. For the @beneath
2434 * case however, it's useful to detect it directly in do_lock_mount().
2435 * If @mnt hasn't been unmounted then @mnt->mnt_mountpoint still points
2436 * to @mnt->mnt_mp->m_dentry. But if @mnt has been unmounted it will
2437 * point to @mnt->mnt_root and @mnt->mnt_mp will be NULL.
2438 *
2439 * Return: Either the target mountpoint on the top mount or the top
2440 * mount's mountpoint.
2441 */
2442static struct mountpoint *do_lock_mount(struct path *path, bool beneath)
2443{
2444 struct vfsmount *mnt = path->mnt;
2445 struct dentry *dentry;
2446 struct mountpoint *mp = ERR_PTR(-ENOENT);
2447
2448 for (;;) {
2449 struct mount *m;
2450
2451 if (beneath) {
2452 m = real_mount(mnt);
2453 read_seqlock_excl(&mount_lock);
2454 dentry = dget(m->mnt_mountpoint);
2455 read_sequnlock_excl(&mount_lock);
2456 } else {
2457 dentry = path->dentry;
2458 }
2459
2460 inode_lock(dentry->d_inode);
2461 if (unlikely(cant_mount(dentry))) {
2462 inode_unlock(dentry->d_inode);
2463 goto out;
2464 }
2465
2466 namespace_lock();
2467
2468 if (beneath && (!is_mounted(mnt) || m->mnt_mountpoint != dentry)) {
2469 namespace_unlock();
2470 inode_unlock(dentry->d_inode);
2471 goto out;
2472 }
2473
2474 mnt = lookup_mnt(path);
2475 if (likely(!mnt))
2476 break;
2477
2478 namespace_unlock();
2479 inode_unlock(dentry->d_inode);
2480 if (beneath)
2481 dput(dentry);
2482 path_put(path);
2483 path->mnt = mnt;
2484 path->dentry = dget(mnt->mnt_root);
2485 }
2486
2487 mp = get_mountpoint(dentry);
2488 if (IS_ERR(mp)) {
2489 namespace_unlock();
2490 inode_unlock(dentry->d_inode);
2491 }
2492
2493out:
2494 if (beneath)
2495 dput(dentry);
2496
2497 return mp;
2498}
2499
2500static inline struct mountpoint *lock_mount(struct path *path)
2501{
2502 return do_lock_mount(path, false);
2503}
2504
2505static void unlock_mount(struct mountpoint *where)
2506{
2507 struct dentry *dentry = where->m_dentry;
2508
2509 read_seqlock_excl(&mount_lock);
2510 put_mountpoint(where);
2511 read_sequnlock_excl(&mount_lock);
2512
2513 namespace_unlock();
2514 inode_unlock(dentry->d_inode);
2515}
2516
2517static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
2518{
2519 if (mnt->mnt.mnt_sb->s_flags & SB_NOUSER)
2520 return -EINVAL;
2521
2522 if (d_is_dir(mp->m_dentry) !=
2523 d_is_dir(mnt->mnt.mnt_root))
2524 return -ENOTDIR;
2525
2526 return attach_recursive_mnt(mnt, p, mp, 0);
2527}
2528
2529/*
2530 * Sanity check the flags to change_mnt_propagation.
2531 */
2532
2533static int flags_to_propagation_type(int ms_flags)
2534{
2535 int type = ms_flags & ~(MS_REC | MS_SILENT);
2536
2537 /* Fail if any non-propagation flags are set */
2538 if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2539 return 0;
2540 /* Only one propagation flag should be set */
2541 if (!is_power_of_2(type))
2542 return 0;
2543 return type;
2544}
2545
2546/*
2547 * recursively change the type of the mountpoint.
2548 */
2549static int do_change_type(struct path *path, int ms_flags)
2550{
2551 struct mount *m;
2552 struct mount *mnt = real_mount(path->mnt);
2553 int recurse = ms_flags & MS_REC;
2554 int type;
2555 int err = 0;
2556
2557 if (!path_mounted(path))
2558 return -EINVAL;
2559
2560 type = flags_to_propagation_type(ms_flags);
2561 if (!type)
2562 return -EINVAL;
2563
2564 namespace_lock();
2565 if (type == MS_SHARED) {
2566 err = invent_group_ids(mnt, recurse);
2567 if (err)
2568 goto out_unlock;
2569 }
2570
2571 lock_mount_hash();
2572 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
2573 change_mnt_propagation(m, type);
2574 unlock_mount_hash();
2575
2576 out_unlock:
2577 namespace_unlock();
2578 return err;
2579}
2580
2581static struct mount *__do_loopback(struct path *old_path, int recurse)
2582{
2583 struct mount *mnt = ERR_PTR(-EINVAL), *old = real_mount(old_path->mnt);
2584
2585 if (IS_MNT_UNBINDABLE(old))
2586 return mnt;
2587
2588 if (!check_mnt(old) && old_path->dentry->d_op != &ns_dentry_operations)
2589 return mnt;
2590
2591 if (!recurse && has_locked_children(old, old_path->dentry))
2592 return mnt;
2593
2594 if (recurse)
2595 mnt = copy_tree(old, old_path->dentry, CL_COPY_MNT_NS_FILE);
2596 else
2597 mnt = clone_mnt(old, old_path->dentry, 0);
2598
2599 if (!IS_ERR(mnt))
2600 mnt->mnt.mnt_flags &= ~MNT_LOCKED;
2601
2602 return mnt;
2603}
2604
2605/*
2606 * do loopback mount.
2607 */
2608static int do_loopback(struct path *path, const char *old_name,
2609 int recurse)
2610{
2611 struct path old_path;
2612 struct mount *mnt = NULL, *parent;
2613 struct mountpoint *mp;
2614 int err;
2615 if (!old_name || !*old_name)
2616 return -EINVAL;
2617 err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
2618 if (err)
2619 return err;
2620
2621 err = -EINVAL;
2622 if (mnt_ns_loop(old_path.dentry))
2623 goto out;
2624
2625 mp = lock_mount(path);
2626 if (IS_ERR(mp)) {
2627 err = PTR_ERR(mp);
2628 goto out;
2629 }
2630
2631 parent = real_mount(path->mnt);
2632 if (!check_mnt(parent))
2633 goto out2;
2634
2635 mnt = __do_loopback(&old_path, recurse);
2636 if (IS_ERR(mnt)) {
2637 err = PTR_ERR(mnt);
2638 goto out2;
2639 }
2640
2641 err = graft_tree(mnt, parent, mp);
2642 if (err) {
2643 lock_mount_hash();
2644 umount_tree(mnt, UMOUNT_SYNC);
2645 unlock_mount_hash();
2646 }
2647out2:
2648 unlock_mount(mp);
2649out:
2650 path_put(&old_path);
2651 return err;
2652}
2653
2654static struct file *open_detached_copy(struct path *path, bool recursive)
2655{
2656 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2657 struct mnt_namespace *ns = alloc_mnt_ns(user_ns, true);
2658 struct mount *mnt, *p;
2659 struct file *file;
2660
2661 if (IS_ERR(ns))
2662 return ERR_CAST(ns);
2663
2664 namespace_lock();
2665 mnt = __do_loopback(path, recursive);
2666 if (IS_ERR(mnt)) {
2667 namespace_unlock();
2668 free_mnt_ns(ns);
2669 return ERR_CAST(mnt);
2670 }
2671
2672 lock_mount_hash();
2673 for (p = mnt; p; p = next_mnt(p, mnt)) {
2674 mnt_add_to_ns(ns, p);
2675 ns->nr_mounts++;
2676 }
2677 ns->root = mnt;
2678 mntget(&mnt->mnt);
2679 unlock_mount_hash();
2680 namespace_unlock();
2681
2682 mntput(path->mnt);
2683 path->mnt = &mnt->mnt;
2684 file = dentry_open(path, O_PATH, current_cred());
2685 if (IS_ERR(file))
2686 dissolve_on_fput(path->mnt);
2687 else
2688 file->f_mode |= FMODE_NEED_UNMOUNT;
2689 return file;
2690}
2691
2692SYSCALL_DEFINE3(open_tree, int, dfd, const char __user *, filename, unsigned, flags)
2693{
2694 struct file *file;
2695 struct path path;
2696 int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW;
2697 bool detached = flags & OPEN_TREE_CLONE;
2698 int error;
2699 int fd;
2700
2701 BUILD_BUG_ON(OPEN_TREE_CLOEXEC != O_CLOEXEC);
2702
2703 if (flags & ~(AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_RECURSIVE |
2704 AT_SYMLINK_NOFOLLOW | OPEN_TREE_CLONE |
2705 OPEN_TREE_CLOEXEC))
2706 return -EINVAL;
2707
2708 if ((flags & (AT_RECURSIVE | OPEN_TREE_CLONE)) == AT_RECURSIVE)
2709 return -EINVAL;
2710
2711 if (flags & AT_NO_AUTOMOUNT)
2712 lookup_flags &= ~LOOKUP_AUTOMOUNT;
2713 if (flags & AT_SYMLINK_NOFOLLOW)
2714 lookup_flags &= ~LOOKUP_FOLLOW;
2715 if (flags & AT_EMPTY_PATH)
2716 lookup_flags |= LOOKUP_EMPTY;
2717
2718 if (detached && !may_mount())
2719 return -EPERM;
2720
2721 fd = get_unused_fd_flags(flags & O_CLOEXEC);
2722 if (fd < 0)
2723 return fd;
2724
2725 error = user_path_at(dfd, filename, lookup_flags, &path);
2726 if (unlikely(error)) {
2727 file = ERR_PTR(error);
2728 } else {
2729 if (detached)
2730 file = open_detached_copy(&path, flags & AT_RECURSIVE);
2731 else
2732 file = dentry_open(&path, O_PATH, current_cred());
2733 path_put(&path);
2734 }
2735 if (IS_ERR(file)) {
2736 put_unused_fd(fd);
2737 return PTR_ERR(file);
2738 }
2739 fd_install(fd, file);
2740 return fd;
2741}
2742
2743/*
2744 * Don't allow locked mount flags to be cleared.
2745 *
2746 * No locks need to be held here while testing the various MNT_LOCK
2747 * flags because those flags can never be cleared once they are set.
2748 */
2749static bool can_change_locked_flags(struct mount *mnt, unsigned int mnt_flags)
2750{
2751 unsigned int fl = mnt->mnt.mnt_flags;
2752
2753 if ((fl & MNT_LOCK_READONLY) &&
2754 !(mnt_flags & MNT_READONLY))
2755 return false;
2756
2757 if ((fl & MNT_LOCK_NODEV) &&
2758 !(mnt_flags & MNT_NODEV))
2759 return false;
2760
2761 if ((fl & MNT_LOCK_NOSUID) &&
2762 !(mnt_flags & MNT_NOSUID))
2763 return false;
2764
2765 if ((fl & MNT_LOCK_NOEXEC) &&
2766 !(mnt_flags & MNT_NOEXEC))
2767 return false;
2768
2769 if ((fl & MNT_LOCK_ATIME) &&
2770 ((fl & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK)))
2771 return false;
2772
2773 return true;
2774}
2775
2776static int change_mount_ro_state(struct mount *mnt, unsigned int mnt_flags)
2777{
2778 bool readonly_request = (mnt_flags & MNT_READONLY);
2779
2780 if (readonly_request == __mnt_is_readonly(&mnt->mnt))
2781 return 0;
2782
2783 if (readonly_request)
2784 return mnt_make_readonly(mnt);
2785
2786 mnt->mnt.mnt_flags &= ~MNT_READONLY;
2787 return 0;
2788}
2789
2790static void set_mount_attributes(struct mount *mnt, unsigned int mnt_flags)
2791{
2792 mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;
2793 mnt->mnt.mnt_flags = mnt_flags;
2794 touch_mnt_namespace(mnt->mnt_ns);
2795}
2796
2797static void mnt_warn_timestamp_expiry(struct path *mountpoint, struct vfsmount *mnt)
2798{
2799 struct super_block *sb = mnt->mnt_sb;
2800
2801 if (!__mnt_is_readonly(mnt) &&
2802 (!(sb->s_iflags & SB_I_TS_EXPIRY_WARNED)) &&
2803 (ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX > sb->s_time_max)) {
2804 char *buf = (char *)__get_free_page(GFP_KERNEL);
2805 char *mntpath = buf ? d_path(mountpoint, buf, PAGE_SIZE) : ERR_PTR(-ENOMEM);
2806
2807 pr_warn("%s filesystem being %s at %s supports timestamps until %ptTd (0x%llx)\n",
2808 sb->s_type->name,
2809 is_mounted(mnt) ? "remounted" : "mounted",
2810 mntpath, &sb->s_time_max,
2811 (unsigned long long)sb->s_time_max);
2812
2813 free_page((unsigned long)buf);
2814 sb->s_iflags |= SB_I_TS_EXPIRY_WARNED;
2815 }
2816}
2817
2818/*
2819 * Handle reconfiguration of the mountpoint only without alteration of the
2820 * superblock it refers to. This is triggered by specifying MS_REMOUNT|MS_BIND
2821 * to mount(2).
2822 */
2823static int do_reconfigure_mnt(struct path *path, unsigned int mnt_flags)
2824{
2825 struct super_block *sb = path->mnt->mnt_sb;
2826 struct mount *mnt = real_mount(path->mnt);
2827 int ret;
2828
2829 if (!check_mnt(mnt))
2830 return -EINVAL;
2831
2832 if (!path_mounted(path))
2833 return -EINVAL;
2834
2835 if (!can_change_locked_flags(mnt, mnt_flags))
2836 return -EPERM;
2837
2838 /*
2839 * We're only checking whether the superblock is read-only not
2840 * changing it, so only take down_read(&sb->s_umount).
2841 */
2842 down_read(&sb->s_umount);
2843 lock_mount_hash();
2844 ret = change_mount_ro_state(mnt, mnt_flags);
2845 if (ret == 0)
2846 set_mount_attributes(mnt, mnt_flags);
2847 unlock_mount_hash();
2848 up_read(&sb->s_umount);
2849
2850 mnt_warn_timestamp_expiry(path, &mnt->mnt);
2851
2852 return ret;
2853}
2854
2855/*
2856 * change filesystem flags. dir should be a physical root of filesystem.
2857 * If you've mounted a non-root directory somewhere and want to do remount
2858 * on it - tough luck.
2859 */
2860static int do_remount(struct path *path, int ms_flags, int sb_flags,
2861 int mnt_flags, void *data)
2862{
2863 int err;
2864 struct super_block *sb = path->mnt->mnt_sb;
2865 struct mount *mnt = real_mount(path->mnt);
2866 struct fs_context *fc;
2867
2868 if (!check_mnt(mnt))
2869 return -EINVAL;
2870
2871 if (!path_mounted(path))
2872 return -EINVAL;
2873
2874 if (!can_change_locked_flags(mnt, mnt_flags))
2875 return -EPERM;
2876
2877 fc = fs_context_for_reconfigure(path->dentry, sb_flags, MS_RMT_MASK);
2878 if (IS_ERR(fc))
2879 return PTR_ERR(fc);
2880
2881 /*
2882 * Indicate to the filesystem that the remount request is coming
2883 * from the legacy mount system call.
2884 */
2885 fc->oldapi = true;
2886
2887 err = parse_monolithic_mount_data(fc, data);
2888 if (!err) {
2889 down_write(&sb->s_umount);
2890 err = -EPERM;
2891 if (ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) {
2892 err = reconfigure_super(fc);
2893 if (!err) {
2894 lock_mount_hash();
2895 set_mount_attributes(mnt, mnt_flags);
2896 unlock_mount_hash();
2897 }
2898 }
2899 up_write(&sb->s_umount);
2900 }
2901
2902 mnt_warn_timestamp_expiry(path, &mnt->mnt);
2903
2904 put_fs_context(fc);
2905 return err;
2906}
2907
2908static inline int tree_contains_unbindable(struct mount *mnt)
2909{
2910 struct mount *p;
2911 for (p = mnt; p; p = next_mnt(p, mnt)) {
2912 if (IS_MNT_UNBINDABLE(p))
2913 return 1;
2914 }
2915 return 0;
2916}
2917
2918/*
2919 * Check that there aren't references to earlier/same mount namespaces in the
2920 * specified subtree. Such references can act as pins for mount namespaces
2921 * that aren't checked by the mount-cycle checking code, thereby allowing
2922 * cycles to be made.
2923 */
2924static bool check_for_nsfs_mounts(struct mount *subtree)
2925{
2926 struct mount *p;
2927 bool ret = false;
2928
2929 lock_mount_hash();
2930 for (p = subtree; p; p = next_mnt(p, subtree))
2931 if (mnt_ns_loop(p->mnt.mnt_root))
2932 goto out;
2933
2934 ret = true;
2935out:
2936 unlock_mount_hash();
2937 return ret;
2938}
2939
2940static int do_set_group(struct path *from_path, struct path *to_path)
2941{
2942 struct mount *from, *to;
2943 int err;
2944
2945 from = real_mount(from_path->mnt);
2946 to = real_mount(to_path->mnt);
2947
2948 namespace_lock();
2949
2950 err = -EINVAL;
2951 /* To and From must be mounted */
2952 if (!is_mounted(&from->mnt))
2953 goto out;
2954 if (!is_mounted(&to->mnt))
2955 goto out;
2956
2957 err = -EPERM;
2958 /* We should be allowed to modify mount namespaces of both mounts */
2959 if (!ns_capable(from->mnt_ns->user_ns, CAP_SYS_ADMIN))
2960 goto out;
2961 if (!ns_capable(to->mnt_ns->user_ns, CAP_SYS_ADMIN))
2962 goto out;
2963
2964 err = -EINVAL;
2965 /* To and From paths should be mount roots */
2966 if (!path_mounted(from_path))
2967 goto out;
2968 if (!path_mounted(to_path))
2969 goto out;
2970
2971 /* Setting sharing groups is only allowed across same superblock */
2972 if (from->mnt.mnt_sb != to->mnt.mnt_sb)
2973 goto out;
2974
2975 /* From mount root should be wider than To mount root */
2976 if (!is_subdir(to->mnt.mnt_root, from->mnt.mnt_root))
2977 goto out;
2978
2979 /* From mount should not have locked children in place of To's root */
2980 if (has_locked_children(from, to->mnt.mnt_root))
2981 goto out;
2982
2983 /* Setting sharing groups is only allowed on private mounts */
2984 if (IS_MNT_SHARED(to) || IS_MNT_SLAVE(to))
2985 goto out;
2986
2987 /* From should not be private */
2988 if (!IS_MNT_SHARED(from) && !IS_MNT_SLAVE(from))
2989 goto out;
2990
2991 if (IS_MNT_SLAVE(from)) {
2992 struct mount *m = from->mnt_master;
2993
2994 list_add(&to->mnt_slave, &m->mnt_slave_list);
2995 to->mnt_master = m;
2996 }
2997
2998 if (IS_MNT_SHARED(from)) {
2999 to->mnt_group_id = from->mnt_group_id;
3000 list_add(&to->mnt_share, &from->mnt_share);
3001 lock_mount_hash();
3002 set_mnt_shared(to);
3003 unlock_mount_hash();
3004 }
3005
3006 err = 0;
3007out:
3008 namespace_unlock();
3009 return err;
3010}
3011
3012/**
3013 * path_overmounted - check if path is overmounted
3014 * @path: path to check
3015 *
3016 * Check if path is overmounted, i.e., if there's a mount on top of
3017 * @path->mnt with @path->dentry as mountpoint.
3018 *
3019 * Context: This function expects namespace_lock() to be held.
3020 * Return: If path is overmounted true is returned, false if not.
3021 */
3022static inline bool path_overmounted(const struct path *path)
3023{
3024 rcu_read_lock();
3025 if (unlikely(__lookup_mnt(path->mnt, path->dentry))) {
3026 rcu_read_unlock();
3027 return true;
3028 }
3029 rcu_read_unlock();
3030 return false;
3031}
3032
3033/**
3034 * can_move_mount_beneath - check that we can mount beneath the top mount
3035 * @from: mount to mount beneath
3036 * @to: mount under which to mount
3037 * @mp: mountpoint of @to
3038 *
3039 * - Make sure that @to->dentry is actually the root of a mount under
3040 * which we can mount another mount.
3041 * - Make sure that nothing can be mounted beneath the caller's current
3042 * root or the rootfs of the namespace.
3043 * - Make sure that the caller can unmount the topmost mount ensuring
3044 * that the caller could reveal the underlying mountpoint.
3045 * - Ensure that nothing has been mounted on top of @from before we
3046 * grabbed @namespace_sem to avoid creating pointless shadow mounts.
3047 * - Prevent mounting beneath a mount if the propagation relationship
3048 * between the source mount, parent mount, and top mount would lead to
3049 * nonsensical mount trees.
3050 *
3051 * Context: This function expects namespace_lock() to be held.
3052 * Return: On success 0, and on error a negative error code is returned.
3053 */
3054static int can_move_mount_beneath(const struct path *from,
3055 const struct path *to,
3056 const struct mountpoint *mp)
3057{
3058 struct mount *mnt_from = real_mount(from->mnt),
3059 *mnt_to = real_mount(to->mnt),
3060 *parent_mnt_to = mnt_to->mnt_parent;
3061
3062 if (!mnt_has_parent(mnt_to))
3063 return -EINVAL;
3064
3065 if (!path_mounted(to))
3066 return -EINVAL;
3067
3068 if (IS_MNT_LOCKED(mnt_to))
3069 return -EINVAL;
3070
3071 /* Avoid creating shadow mounts during mount propagation. */
3072 if (path_overmounted(from))
3073 return -EINVAL;
3074
3075 /*
3076 * Mounting beneath the rootfs only makes sense when the
3077 * semantics of pivot_root(".", ".") are used.
3078 */
3079 if (&mnt_to->mnt == current->fs->root.mnt)
3080 return -EINVAL;
3081 if (parent_mnt_to == current->nsproxy->mnt_ns->root)
3082 return -EINVAL;
3083
3084 for (struct mount *p = mnt_from; mnt_has_parent(p); p = p->mnt_parent)
3085 if (p == mnt_to)
3086 return -EINVAL;
3087
3088 /*
3089 * If the parent mount propagates to the child mount this would
3090 * mean mounting @mnt_from on @mnt_to->mnt_parent and then
3091 * propagating a copy @c of @mnt_from on top of @mnt_to. This
3092 * defeats the whole purpose of mounting beneath another mount.
3093 */
3094 if (propagation_would_overmount(parent_mnt_to, mnt_to, mp))
3095 return -EINVAL;
3096
3097 /*
3098 * If @mnt_to->mnt_parent propagates to @mnt_from this would
3099 * mean propagating a copy @c of @mnt_from on top of @mnt_from.
3100 * Afterwards @mnt_from would be mounted on top of
3101 * @mnt_to->mnt_parent and @mnt_to would be unmounted from
3102 * @mnt->mnt_parent and remounted on @mnt_from. But since @c is
3103 * already mounted on @mnt_from, @mnt_to would ultimately be
3104 * remounted on top of @c. Afterwards, @mnt_from would be
3105 * covered by a copy @c of @mnt_from and @c would be covered by
3106 * @mnt_from itself. This defeats the whole purpose of mounting
3107 * @mnt_from beneath @mnt_to.
3108 */
3109 if (propagation_would_overmount(parent_mnt_to, mnt_from, mp))
3110 return -EINVAL;
3111
3112 return 0;
3113}
3114
3115static int do_move_mount(struct path *old_path, struct path *new_path,
3116 bool beneath)
3117{
3118 struct mnt_namespace *ns;
3119 struct mount *p;
3120 struct mount *old;
3121 struct mount *parent;
3122 struct mountpoint *mp, *old_mp;
3123 int err;
3124 bool attached;
3125 enum mnt_tree_flags_t flags = 0;
3126
3127 mp = do_lock_mount(new_path, beneath);
3128 if (IS_ERR(mp))
3129 return PTR_ERR(mp);
3130
3131 old = real_mount(old_path->mnt);
3132 p = real_mount(new_path->mnt);
3133 parent = old->mnt_parent;
3134 attached = mnt_has_parent(old);
3135 if (attached)
3136 flags |= MNT_TREE_MOVE;
3137 old_mp = old->mnt_mp;
3138 ns = old->mnt_ns;
3139
3140 err = -EINVAL;
3141 /* The mountpoint must be in our namespace. */
3142 if (!check_mnt(p))
3143 goto out;
3144
3145 /* The thing moved must be mounted... */
3146 if (!is_mounted(&old->mnt))
3147 goto out;
3148
3149 /* ... and either ours or the root of anon namespace */
3150 if (!(attached ? check_mnt(old) : is_anon_ns(ns)))
3151 goto out;
3152
3153 if (old->mnt.mnt_flags & MNT_LOCKED)
3154 goto out;
3155
3156 if (!path_mounted(old_path))
3157 goto out;
3158
3159 if (d_is_dir(new_path->dentry) !=
3160 d_is_dir(old_path->dentry))
3161 goto out;
3162 /*
3163 * Don't move a mount residing in a shared parent.
3164 */
3165 if (attached && IS_MNT_SHARED(parent))
3166 goto out;
3167
3168 if (beneath) {
3169 err = can_move_mount_beneath(old_path, new_path, mp);
3170 if (err)
3171 goto out;
3172
3173 err = -EINVAL;
3174 p = p->mnt_parent;
3175 flags |= MNT_TREE_BENEATH;
3176 }
3177
3178 /*
3179 * Don't move a mount tree containing unbindable mounts to a destination
3180 * mount which is shared.
3181 */
3182 if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
3183 goto out;
3184 err = -ELOOP;
3185 if (!check_for_nsfs_mounts(old))
3186 goto out;
3187 for (; mnt_has_parent(p); p = p->mnt_parent)
3188 if (p == old)
3189 goto out;
3190
3191 err = attach_recursive_mnt(old, real_mount(new_path->mnt), mp, flags);
3192 if (err)
3193 goto out;
3194
3195 /* if the mount is moved, it should no longer be expire
3196 * automatically */
3197 list_del_init(&old->mnt_expire);
3198 if (attached)
3199 put_mountpoint(old_mp);
3200out:
3201 unlock_mount(mp);
3202 if (!err) {
3203 if (attached)
3204 mntput_no_expire(parent);
3205 else
3206 free_mnt_ns(ns);
3207 }
3208 return err;
3209}
3210
3211static int do_move_mount_old(struct path *path, const char *old_name)
3212{
3213 struct path old_path;
3214 int err;
3215
3216 if (!old_name || !*old_name)
3217 return -EINVAL;
3218
3219 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
3220 if (err)
3221 return err;
3222
3223 err = do_move_mount(&old_path, path, false);
3224 path_put(&old_path);
3225 return err;
3226}
3227
3228/*
3229 * add a mount into a namespace's mount tree
3230 */
3231static int do_add_mount(struct mount *newmnt, struct mountpoint *mp,
3232 const struct path *path, int mnt_flags)
3233{
3234 struct mount *parent = real_mount(path->mnt);
3235
3236 mnt_flags &= ~MNT_INTERNAL_FLAGS;
3237
3238 if (unlikely(!check_mnt(parent))) {
3239 /* that's acceptable only for automounts done in private ns */
3240 if (!(mnt_flags & MNT_SHRINKABLE))
3241 return -EINVAL;
3242 /* ... and for those we'd better have mountpoint still alive */
3243 if (!parent->mnt_ns)
3244 return -EINVAL;
3245 }
3246
3247 /* Refuse the same filesystem on the same mount point */
3248 if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && path_mounted(path))
3249 return -EBUSY;
3250
3251 if (d_is_symlink(newmnt->mnt.mnt_root))
3252 return -EINVAL;
3253
3254 newmnt->mnt.mnt_flags = mnt_flags;
3255 return graft_tree(newmnt, parent, mp);
3256}
3257
3258static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags);
3259
3260/*
3261 * Create a new mount using a superblock configuration and request it
3262 * be added to the namespace tree.
3263 */
3264static int do_new_mount_fc(struct fs_context *fc, struct path *mountpoint,
3265 unsigned int mnt_flags)
3266{
3267 struct vfsmount *mnt;
3268 struct mountpoint *mp;
3269 struct super_block *sb = fc->root->d_sb;
3270 int error;
3271
3272 error = security_sb_kern_mount(sb);
3273 if (!error && mount_too_revealing(sb, &mnt_flags))
3274 error = -EPERM;
3275
3276 if (unlikely(error)) {
3277 fc_drop_locked(fc);
3278 return error;
3279 }
3280
3281 up_write(&sb->s_umount);
3282
3283 mnt = vfs_create_mount(fc);
3284 if (IS_ERR(mnt))
3285 return PTR_ERR(mnt);
3286
3287 mnt_warn_timestamp_expiry(mountpoint, mnt);
3288
3289 mp = lock_mount(mountpoint);
3290 if (IS_ERR(mp)) {
3291 mntput(mnt);
3292 return PTR_ERR(mp);
3293 }
3294 error = do_add_mount(real_mount(mnt), mp, mountpoint, mnt_flags);
3295 unlock_mount(mp);
3296 if (error < 0)
3297 mntput(mnt);
3298 return error;
3299}
3300
3301/*
3302 * create a new mount for userspace and request it to be added into the
3303 * namespace's tree
3304 */
3305static int do_new_mount(struct path *path, const char *fstype, int sb_flags,
3306 int mnt_flags, const char *name, void *data)
3307{
3308 struct file_system_type *type;
3309 struct fs_context *fc;
3310 const char *subtype = NULL;
3311 int err = 0;
3312
3313 if (!fstype)
3314 return -EINVAL;
3315
3316 type = get_fs_type(fstype);
3317 if (!type)
3318 return -ENODEV;
3319
3320 if (type->fs_flags & FS_HAS_SUBTYPE) {
3321 subtype = strchr(fstype, '.');
3322 if (subtype) {
3323 subtype++;
3324 if (!*subtype) {
3325 put_filesystem(type);
3326 return -EINVAL;
3327 }
3328 }
3329 }
3330
3331 fc = fs_context_for_mount(type, sb_flags);
3332 put_filesystem(type);
3333 if (IS_ERR(fc))
3334 return PTR_ERR(fc);
3335
3336 /*
3337 * Indicate to the filesystem that the mount request is coming
3338 * from the legacy mount system call.
3339 */
3340 fc->oldapi = true;
3341
3342 if (subtype)
3343 err = vfs_parse_fs_string(fc, "subtype",
3344 subtype, strlen(subtype));
3345 if (!err && name)
3346 err = vfs_parse_fs_string(fc, "source", name, strlen(name));
3347 if (!err)
3348 err = parse_monolithic_mount_data(fc, data);
3349 if (!err && !mount_capable(fc))
3350 err = -EPERM;
3351 if (!err)
3352 err = vfs_get_tree(fc);
3353 if (!err)
3354 err = do_new_mount_fc(fc, path, mnt_flags);
3355
3356 put_fs_context(fc);
3357 return err;
3358}
3359
3360int finish_automount(struct vfsmount *m, const struct path *path)
3361{
3362 struct dentry *dentry = path->dentry;
3363 struct mountpoint *mp;
3364 struct mount *mnt;
3365 int err;
3366
3367 if (!m)
3368 return 0;
3369 if (IS_ERR(m))
3370 return PTR_ERR(m);
3371
3372 mnt = real_mount(m);
3373 /* The new mount record should have at least 2 refs to prevent it being
3374 * expired before we get a chance to add it
3375 */
3376 BUG_ON(mnt_get_count(mnt) < 2);
3377
3378 if (m->mnt_sb == path->mnt->mnt_sb &&
3379 m->mnt_root == dentry) {
3380 err = -ELOOP;
3381 goto discard;
3382 }
3383
3384 /*
3385 * we don't want to use lock_mount() - in this case finding something
3386 * that overmounts our mountpoint to be means "quitely drop what we've
3387 * got", not "try to mount it on top".
3388 */
3389 inode_lock(dentry->d_inode);
3390 namespace_lock();
3391 if (unlikely(cant_mount(dentry))) {
3392 err = -ENOENT;
3393 goto discard_locked;
3394 }
3395 if (path_overmounted(path)) {
3396 err = 0;
3397 goto discard_locked;
3398 }
3399 mp = get_mountpoint(dentry);
3400 if (IS_ERR(mp)) {
3401 err = PTR_ERR(mp);
3402 goto discard_locked;
3403 }
3404
3405 err = do_add_mount(mnt, mp, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
3406 unlock_mount(mp);
3407 if (unlikely(err))
3408 goto discard;
3409 mntput(m);
3410 return 0;
3411
3412discard_locked:
3413 namespace_unlock();
3414 inode_unlock(dentry->d_inode);
3415discard:
3416 /* remove m from any expiration list it may be on */
3417 if (!list_empty(&mnt->mnt_expire)) {
3418 namespace_lock();
3419 list_del_init(&mnt->mnt_expire);
3420 namespace_unlock();
3421 }
3422 mntput(m);
3423 mntput(m);
3424 return err;
3425}
3426
3427/**
3428 * mnt_set_expiry - Put a mount on an expiration list
3429 * @mnt: The mount to list.
3430 * @expiry_list: The list to add the mount to.
3431 */
3432void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
3433{
3434 namespace_lock();
3435
3436 list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
3437
3438 namespace_unlock();
3439}
3440EXPORT_SYMBOL(mnt_set_expiry);
3441
3442/*
3443 * process a list of expirable mountpoints with the intent of discarding any
3444 * mountpoints that aren't in use and haven't been touched since last we came
3445 * here
3446 */
3447void mark_mounts_for_expiry(struct list_head *mounts)
3448{
3449 struct mount *mnt, *next;
3450 LIST_HEAD(graveyard);
3451
3452 if (list_empty(mounts))
3453 return;
3454
3455 namespace_lock();
3456 lock_mount_hash();
3457
3458 /* extract from the expiration list every vfsmount that matches the
3459 * following criteria:
3460 * - only referenced by its parent vfsmount
3461 * - still marked for expiry (marked on the last call here; marks are
3462 * cleared by mntput())
3463 */
3464 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
3465 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
3466 propagate_mount_busy(mnt, 1))
3467 continue;
3468 list_move(&mnt->mnt_expire, &graveyard);
3469 }
3470 while (!list_empty(&graveyard)) {
3471 mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
3472 touch_mnt_namespace(mnt->mnt_ns);
3473 umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
3474 }
3475 unlock_mount_hash();
3476 namespace_unlock();
3477}
3478
3479EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
3480
3481/*
3482 * Ripoff of 'select_parent()'
3483 *
3484 * search the list of submounts for a given mountpoint, and move any
3485 * shrinkable submounts to the 'graveyard' list.
3486 */
3487static int select_submounts(struct mount *parent, struct list_head *graveyard)
3488{
3489 struct mount *this_parent = parent;
3490 struct list_head *next;
3491 int found = 0;
3492
3493repeat:
3494 next = this_parent->mnt_mounts.next;
3495resume:
3496 while (next != &this_parent->mnt_mounts) {
3497 struct list_head *tmp = next;
3498 struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
3499
3500 next = tmp->next;
3501 if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
3502 continue;
3503 /*
3504 * Descend a level if the d_mounts list is non-empty.
3505 */
3506 if (!list_empty(&mnt->mnt_mounts)) {
3507 this_parent = mnt;
3508 goto repeat;
3509 }
3510
3511 if (!propagate_mount_busy(mnt, 1)) {
3512 list_move_tail(&mnt->mnt_expire, graveyard);
3513 found++;
3514 }
3515 }
3516 /*
3517 * All done at this level ... ascend and resume the search
3518 */
3519 if (this_parent != parent) {
3520 next = this_parent->mnt_child.next;
3521 this_parent = this_parent->mnt_parent;
3522 goto resume;
3523 }
3524 return found;
3525}
3526
3527/*
3528 * process a list of expirable mountpoints with the intent of discarding any
3529 * submounts of a specific parent mountpoint
3530 *
3531 * mount_lock must be held for write
3532 */
3533static void shrink_submounts(struct mount *mnt)
3534{
3535 LIST_HEAD(graveyard);
3536 struct mount *m;
3537
3538 /* extract submounts of 'mountpoint' from the expiration list */
3539 while (select_submounts(mnt, &graveyard)) {
3540 while (!list_empty(&graveyard)) {
3541 m = list_first_entry(&graveyard, struct mount,
3542 mnt_expire);
3543 touch_mnt_namespace(m->mnt_ns);
3544 umount_tree(m, UMOUNT_PROPAGATE|UMOUNT_SYNC);
3545 }
3546 }
3547}
3548
3549static void *copy_mount_options(const void __user * data)
3550{
3551 char *copy;
3552 unsigned left, offset;
3553
3554 if (!data)
3555 return NULL;
3556
3557 copy = kmalloc(PAGE_SIZE, GFP_KERNEL);
3558 if (!copy)
3559 return ERR_PTR(-ENOMEM);
3560
3561 left = copy_from_user(copy, data, PAGE_SIZE);
3562
3563 /*
3564 * Not all architectures have an exact copy_from_user(). Resort to
3565 * byte at a time.
3566 */
3567 offset = PAGE_SIZE - left;
3568 while (left) {
3569 char c;
3570 if (get_user(c, (const char __user *)data + offset))
3571 break;
3572 copy[offset] = c;
3573 left--;
3574 offset++;
3575 }
3576
3577 if (left == PAGE_SIZE) {
3578 kfree(copy);
3579 return ERR_PTR(-EFAULT);
3580 }
3581
3582 return copy;
3583}
3584
3585static char *copy_mount_string(const void __user *data)
3586{
3587 return data ? strndup_user(data, PATH_MAX) : NULL;
3588}
3589
3590/*
3591 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
3592 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
3593 *
3594 * data is a (void *) that can point to any structure up to
3595 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
3596 * information (or be NULL).
3597 *
3598 * Pre-0.97 versions of mount() didn't have a flags word.
3599 * When the flags word was introduced its top half was required
3600 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
3601 * Therefore, if this magic number is present, it carries no information
3602 * and must be discarded.
3603 */
3604int path_mount(const char *dev_name, struct path *path,
3605 const char *type_page, unsigned long flags, void *data_page)
3606{
3607 unsigned int mnt_flags = 0, sb_flags;
3608 int ret;
3609
3610 /* Discard magic */
3611 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
3612 flags &= ~MS_MGC_MSK;
3613
3614 /* Basic sanity checks */
3615 if (data_page)
3616 ((char *)data_page)[PAGE_SIZE - 1] = 0;
3617
3618 if (flags & MS_NOUSER)
3619 return -EINVAL;
3620
3621 ret = security_sb_mount(dev_name, path, type_page, flags, data_page);
3622 if (ret)
3623 return ret;
3624 if (!may_mount())
3625 return -EPERM;
3626 if (flags & SB_MANDLOCK)
3627 warn_mandlock();
3628
3629 /* Default to relatime unless overriden */
3630 if (!(flags & MS_NOATIME))
3631 mnt_flags |= MNT_RELATIME;
3632
3633 /* Separate the per-mountpoint flags */
3634 if (flags & MS_NOSUID)
3635 mnt_flags |= MNT_NOSUID;
3636 if (flags & MS_NODEV)
3637 mnt_flags |= MNT_NODEV;
3638 if (flags & MS_NOEXEC)
3639 mnt_flags |= MNT_NOEXEC;
3640 if (flags & MS_NOATIME)
3641 mnt_flags |= MNT_NOATIME;
3642 if (flags & MS_NODIRATIME)
3643 mnt_flags |= MNT_NODIRATIME;
3644 if (flags & MS_STRICTATIME)
3645 mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
3646 if (flags & MS_RDONLY)
3647 mnt_flags |= MNT_READONLY;
3648 if (flags & MS_NOSYMFOLLOW)
3649 mnt_flags |= MNT_NOSYMFOLLOW;
3650
3651 /* The default atime for remount is preservation */
3652 if ((flags & MS_REMOUNT) &&
3653 ((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME |
3654 MS_STRICTATIME)) == 0)) {
3655 mnt_flags &= ~MNT_ATIME_MASK;
3656 mnt_flags |= path->mnt->mnt_flags & MNT_ATIME_MASK;
3657 }
3658
3659 sb_flags = flags & (SB_RDONLY |
3660 SB_SYNCHRONOUS |
3661 SB_MANDLOCK |
3662 SB_DIRSYNC |
3663 SB_SILENT |
3664 SB_POSIXACL |
3665 SB_LAZYTIME |
3666 SB_I_VERSION);
3667
3668 if ((flags & (MS_REMOUNT | MS_BIND)) == (MS_REMOUNT | MS_BIND))
3669 return do_reconfigure_mnt(path, mnt_flags);
3670 if (flags & MS_REMOUNT)
3671 return do_remount(path, flags, sb_flags, mnt_flags, data_page);
3672 if (flags & MS_BIND)
3673 return do_loopback(path, dev_name, flags & MS_REC);
3674 if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
3675 return do_change_type(path, flags);
3676 if (flags & MS_MOVE)
3677 return do_move_mount_old(path, dev_name);
3678
3679 return do_new_mount(path, type_page, sb_flags, mnt_flags, dev_name,
3680 data_page);
3681}
3682
3683long do_mount(const char *dev_name, const char __user *dir_name,
3684 const char *type_page, unsigned long flags, void *data_page)
3685{
3686 struct path path;
3687 int ret;
3688
3689 ret = user_path_at(AT_FDCWD, dir_name, LOOKUP_FOLLOW, &path);
3690 if (ret)
3691 return ret;
3692 ret = path_mount(dev_name, &path, type_page, flags, data_page);
3693 path_put(&path);
3694 return ret;
3695}
3696
3697static struct ucounts *inc_mnt_namespaces(struct user_namespace *ns)
3698{
3699 return inc_ucount(ns, current_euid(), UCOUNT_MNT_NAMESPACES);
3700}
3701
3702static void dec_mnt_namespaces(struct ucounts *ucounts)
3703{
3704 dec_ucount(ucounts, UCOUNT_MNT_NAMESPACES);
3705}
3706
3707static void free_mnt_ns(struct mnt_namespace *ns)
3708{
3709 if (!is_anon_ns(ns))
3710 ns_free_inum(&ns->ns);
3711 dec_mnt_namespaces(ns->ucounts);
3712 put_user_ns(ns->user_ns);
3713 kfree(ns);
3714}
3715
3716/*
3717 * Assign a sequence number so we can detect when we attempt to bind
3718 * mount a reference to an older mount namespace into the current
3719 * mount namespace, preventing reference counting loops. A 64bit
3720 * number incrementing at 10Ghz will take 12,427 years to wrap which
3721 * is effectively never, so we can ignore the possibility.
3722 */
3723static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
3724
3725static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool anon)
3726{
3727 struct mnt_namespace *new_ns;
3728 struct ucounts *ucounts;
3729 int ret;
3730
3731 ucounts = inc_mnt_namespaces(user_ns);
3732 if (!ucounts)
3733 return ERR_PTR(-ENOSPC);
3734
3735 new_ns = kzalloc(sizeof(struct mnt_namespace), GFP_KERNEL_ACCOUNT);
3736 if (!new_ns) {
3737 dec_mnt_namespaces(ucounts);
3738 return ERR_PTR(-ENOMEM);
3739 }
3740 if (!anon) {
3741 ret = ns_alloc_inum(&new_ns->ns);
3742 if (ret) {
3743 kfree(new_ns);
3744 dec_mnt_namespaces(ucounts);
3745 return ERR_PTR(ret);
3746 }
3747 }
3748 new_ns->ns.ops = &mntns_operations;
3749 if (!anon)
3750 new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
3751 refcount_set(&new_ns->ns.count, 1);
3752 new_ns->mounts = RB_ROOT;
3753 init_waitqueue_head(&new_ns->poll);
3754 new_ns->user_ns = get_user_ns(user_ns);
3755 new_ns->ucounts = ucounts;
3756 return new_ns;
3757}
3758
3759__latent_entropy
3760struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
3761 struct user_namespace *user_ns, struct fs_struct *new_fs)
3762{
3763 struct mnt_namespace *new_ns;
3764 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
3765 struct mount *p, *q;
3766 struct mount *old;
3767 struct mount *new;
3768 int copy_flags;
3769
3770 BUG_ON(!ns);
3771
3772 if (likely(!(flags & CLONE_NEWNS))) {
3773 get_mnt_ns(ns);
3774 return ns;
3775 }
3776
3777 old = ns->root;
3778
3779 new_ns = alloc_mnt_ns(user_ns, false);
3780 if (IS_ERR(new_ns))
3781 return new_ns;
3782
3783 namespace_lock();
3784 /* First pass: copy the tree topology */
3785 copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
3786 if (user_ns != ns->user_ns)
3787 copy_flags |= CL_SHARED_TO_SLAVE;
3788 new = copy_tree(old, old->mnt.mnt_root, copy_flags);
3789 if (IS_ERR(new)) {
3790 namespace_unlock();
3791 free_mnt_ns(new_ns);
3792 return ERR_CAST(new);
3793 }
3794 if (user_ns != ns->user_ns) {
3795 lock_mount_hash();
3796 lock_mnt_tree(new);
3797 unlock_mount_hash();
3798 }
3799 new_ns->root = new;
3800
3801 /*
3802 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
3803 * as belonging to new namespace. We have already acquired a private
3804 * fs_struct, so tsk->fs->lock is not needed.
3805 */
3806 p = old;
3807 q = new;
3808 while (p) {
3809 mnt_add_to_ns(new_ns, q);
3810 new_ns->nr_mounts++;
3811 if (new_fs) {
3812 if (&p->mnt == new_fs->root.mnt) {
3813 new_fs->root.mnt = mntget(&q->mnt);
3814 rootmnt = &p->mnt;
3815 }
3816 if (&p->mnt == new_fs->pwd.mnt) {
3817 new_fs->pwd.mnt = mntget(&q->mnt);
3818 pwdmnt = &p->mnt;
3819 }
3820 }
3821 p = next_mnt(p, old);
3822 q = next_mnt(q, new);
3823 if (!q)
3824 break;
3825 // an mntns binding we'd skipped?
3826 while (p->mnt.mnt_root != q->mnt.mnt_root)
3827 p = next_mnt(skip_mnt_tree(p), old);
3828 }
3829 namespace_unlock();
3830
3831 if (rootmnt)
3832 mntput(rootmnt);
3833 if (pwdmnt)
3834 mntput(pwdmnt);
3835
3836 return new_ns;
3837}
3838
3839struct dentry *mount_subtree(struct vfsmount *m, const char *name)
3840{
3841 struct mount *mnt = real_mount(m);
3842 struct mnt_namespace *ns;
3843 struct super_block *s;
3844 struct path path;
3845 int err;
3846
3847 ns = alloc_mnt_ns(&init_user_ns, true);
3848 if (IS_ERR(ns)) {
3849 mntput(m);
3850 return ERR_CAST(ns);
3851 }
3852 ns->root = mnt;
3853 ns->nr_mounts++;
3854 mnt_add_to_ns(ns, mnt);
3855
3856 err = vfs_path_lookup(m->mnt_root, m,
3857 name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
3858
3859 put_mnt_ns(ns);
3860
3861 if (err)
3862 return ERR_PTR(err);
3863
3864 /* trade a vfsmount reference for active sb one */
3865 s = path.mnt->mnt_sb;
3866 atomic_inc(&s->s_active);
3867 mntput(path.mnt);
3868 /* lock the sucker */
3869 down_write(&s->s_umount);
3870 /* ... and return the root of (sub)tree on it */
3871 return path.dentry;
3872}
3873EXPORT_SYMBOL(mount_subtree);
3874
3875SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
3876 char __user *, type, unsigned long, flags, void __user *, data)
3877{
3878 int ret;
3879 char *kernel_type;
3880 char *kernel_dev;
3881 void *options;
3882
3883 kernel_type = copy_mount_string(type);
3884 ret = PTR_ERR(kernel_type);
3885 if (IS_ERR(kernel_type))
3886 goto out_type;
3887
3888 kernel_dev = copy_mount_string(dev_name);
3889 ret = PTR_ERR(kernel_dev);
3890 if (IS_ERR(kernel_dev))
3891 goto out_dev;
3892
3893 options = copy_mount_options(data);
3894 ret = PTR_ERR(options);
3895 if (IS_ERR(options))
3896 goto out_data;
3897
3898 ret = do_mount(kernel_dev, dir_name, kernel_type, flags, options);
3899
3900 kfree(options);
3901out_data:
3902 kfree(kernel_dev);
3903out_dev:
3904 kfree(kernel_type);
3905out_type:
3906 return ret;
3907}
3908
3909#define FSMOUNT_VALID_FLAGS \
3910 (MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \
3911 MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME | \
3912 MOUNT_ATTR_NOSYMFOLLOW)
3913
3914#define MOUNT_SETATTR_VALID_FLAGS (FSMOUNT_VALID_FLAGS | MOUNT_ATTR_IDMAP)
3915
3916#define MOUNT_SETATTR_PROPAGATION_FLAGS \
3917 (MS_UNBINDABLE | MS_PRIVATE | MS_SLAVE | MS_SHARED)
3918
3919static unsigned int attr_flags_to_mnt_flags(u64 attr_flags)
3920{
3921 unsigned int mnt_flags = 0;
3922
3923 if (attr_flags & MOUNT_ATTR_RDONLY)
3924 mnt_flags |= MNT_READONLY;
3925 if (attr_flags & MOUNT_ATTR_NOSUID)
3926 mnt_flags |= MNT_NOSUID;
3927 if (attr_flags & MOUNT_ATTR_NODEV)
3928 mnt_flags |= MNT_NODEV;
3929 if (attr_flags & MOUNT_ATTR_NOEXEC)
3930 mnt_flags |= MNT_NOEXEC;
3931 if (attr_flags & MOUNT_ATTR_NODIRATIME)
3932 mnt_flags |= MNT_NODIRATIME;
3933 if (attr_flags & MOUNT_ATTR_NOSYMFOLLOW)
3934 mnt_flags |= MNT_NOSYMFOLLOW;
3935
3936 return mnt_flags;
3937}
3938
3939/*
3940 * Create a kernel mount representation for a new, prepared superblock
3941 * (specified by fs_fd) and attach to an open_tree-like file descriptor.
3942 */
3943SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
3944 unsigned int, attr_flags)
3945{
3946 struct mnt_namespace *ns;
3947 struct fs_context *fc;
3948 struct file *file;
3949 struct path newmount;
3950 struct mount *mnt;
3951 struct fd f;
3952 unsigned int mnt_flags = 0;
3953 long ret;
3954
3955 if (!may_mount())
3956 return -EPERM;
3957
3958 if ((flags & ~(FSMOUNT_CLOEXEC)) != 0)
3959 return -EINVAL;
3960
3961 if (attr_flags & ~FSMOUNT_VALID_FLAGS)
3962 return -EINVAL;
3963
3964 mnt_flags = attr_flags_to_mnt_flags(attr_flags);
3965
3966 switch (attr_flags & MOUNT_ATTR__ATIME) {
3967 case MOUNT_ATTR_STRICTATIME:
3968 break;
3969 case MOUNT_ATTR_NOATIME:
3970 mnt_flags |= MNT_NOATIME;
3971 break;
3972 case MOUNT_ATTR_RELATIME:
3973 mnt_flags |= MNT_RELATIME;
3974 break;
3975 default:
3976 return -EINVAL;
3977 }
3978
3979 f = fdget(fs_fd);
3980 if (!f.file)
3981 return -EBADF;
3982
3983 ret = -EINVAL;
3984 if (f.file->f_op != &fscontext_fops)
3985 goto err_fsfd;
3986
3987 fc = f.file->private_data;
3988
3989 ret = mutex_lock_interruptible(&fc->uapi_mutex);
3990 if (ret < 0)
3991 goto err_fsfd;
3992
3993 /* There must be a valid superblock or we can't mount it */
3994 ret = -EINVAL;
3995 if (!fc->root)
3996 goto err_unlock;
3997
3998 ret = -EPERM;
3999 if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) {
4000 pr_warn("VFS: Mount too revealing\n");
4001 goto err_unlock;
4002 }
4003
4004 ret = -EBUSY;
4005 if (fc->phase != FS_CONTEXT_AWAITING_MOUNT)
4006 goto err_unlock;
4007
4008 if (fc->sb_flags & SB_MANDLOCK)
4009 warn_mandlock();
4010
4011 newmount.mnt = vfs_create_mount(fc);
4012 if (IS_ERR(newmount.mnt)) {
4013 ret = PTR_ERR(newmount.mnt);
4014 goto err_unlock;
4015 }
4016 newmount.dentry = dget(fc->root);
4017 newmount.mnt->mnt_flags = mnt_flags;
4018
4019 /* We've done the mount bit - now move the file context into more or
4020 * less the same state as if we'd done an fspick(). We don't want to
4021 * do any memory allocation or anything like that at this point as we
4022 * don't want to have to handle any errors incurred.
4023 */
4024 vfs_clean_context(fc);
4025
4026 ns = alloc_mnt_ns(current->nsproxy->mnt_ns->user_ns, true);
4027 if (IS_ERR(ns)) {
4028 ret = PTR_ERR(ns);
4029 goto err_path;
4030 }
4031 mnt = real_mount(newmount.mnt);
4032 ns->root = mnt;
4033 ns->nr_mounts = 1;
4034 mnt_add_to_ns(ns, mnt);
4035 mntget(newmount.mnt);
4036
4037 /* Attach to an apparent O_PATH fd with a note that we need to unmount
4038 * it, not just simply put it.
4039 */
4040 file = dentry_open(&newmount, O_PATH, fc->cred);
4041 if (IS_ERR(file)) {
4042 dissolve_on_fput(newmount.mnt);
4043 ret = PTR_ERR(file);
4044 goto err_path;
4045 }
4046 file->f_mode |= FMODE_NEED_UNMOUNT;
4047
4048 ret = get_unused_fd_flags((flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0);
4049 if (ret >= 0)
4050 fd_install(ret, file);
4051 else
4052 fput(file);
4053
4054err_path:
4055 path_put(&newmount);
4056err_unlock:
4057 mutex_unlock(&fc->uapi_mutex);
4058err_fsfd:
4059 fdput(f);
4060 return ret;
4061}
4062
4063/*
4064 * Move a mount from one place to another. In combination with
4065 * fsopen()/fsmount() this is used to install a new mount and in combination
4066 * with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy
4067 * a mount subtree.
4068 *
4069 * Note the flags value is a combination of MOVE_MOUNT_* flags.
4070 */
4071SYSCALL_DEFINE5(move_mount,
4072 int, from_dfd, const char __user *, from_pathname,
4073 int, to_dfd, const char __user *, to_pathname,
4074 unsigned int, flags)
4075{
4076 struct path from_path, to_path;
4077 unsigned int lflags;
4078 int ret = 0;
4079
4080 if (!may_mount())
4081 return -EPERM;
4082
4083 if (flags & ~MOVE_MOUNT__MASK)
4084 return -EINVAL;
4085
4086 if ((flags & (MOVE_MOUNT_BENEATH | MOVE_MOUNT_SET_GROUP)) ==
4087 (MOVE_MOUNT_BENEATH | MOVE_MOUNT_SET_GROUP))
4088 return -EINVAL;
4089
4090 /* If someone gives a pathname, they aren't permitted to move
4091 * from an fd that requires unmount as we can't get at the flag
4092 * to clear it afterwards.
4093 */
4094 lflags = 0;
4095 if (flags & MOVE_MOUNT_F_SYMLINKS) lflags |= LOOKUP_FOLLOW;
4096 if (flags & MOVE_MOUNT_F_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT;
4097 if (flags & MOVE_MOUNT_F_EMPTY_PATH) lflags |= LOOKUP_EMPTY;
4098
4099 ret = user_path_at(from_dfd, from_pathname, lflags, &from_path);
4100 if (ret < 0)
4101 return ret;
4102
4103 lflags = 0;
4104 if (flags & MOVE_MOUNT_T_SYMLINKS) lflags |= LOOKUP_FOLLOW;
4105 if (flags & MOVE_MOUNT_T_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT;
4106 if (flags & MOVE_MOUNT_T_EMPTY_PATH) lflags |= LOOKUP_EMPTY;
4107
4108 ret = user_path_at(to_dfd, to_pathname, lflags, &to_path);
4109 if (ret < 0)
4110 goto out_from;
4111
4112 ret = security_move_mount(&from_path, &to_path);
4113 if (ret < 0)
4114 goto out_to;
4115
4116 if (flags & MOVE_MOUNT_SET_GROUP)
4117 ret = do_set_group(&from_path, &to_path);
4118 else
4119 ret = do_move_mount(&from_path, &to_path,
4120 (flags & MOVE_MOUNT_BENEATH));
4121
4122out_to:
4123 path_put(&to_path);
4124out_from:
4125 path_put(&from_path);
4126 return ret;
4127}
4128
4129/*
4130 * Return true if path is reachable from root
4131 *
4132 * namespace_sem or mount_lock is held
4133 */
4134bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
4135 const struct path *root)
4136{
4137 while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
4138 dentry = mnt->mnt_mountpoint;
4139 mnt = mnt->mnt_parent;
4140 }
4141 return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
4142}
4143
4144bool path_is_under(const struct path *path1, const struct path *path2)
4145{
4146 bool res;
4147 read_seqlock_excl(&mount_lock);
4148 res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2);
4149 read_sequnlock_excl(&mount_lock);
4150 return res;
4151}
4152EXPORT_SYMBOL(path_is_under);
4153
4154/*
4155 * pivot_root Semantics:
4156 * Moves the root file system of the current process to the directory put_old,
4157 * makes new_root as the new root file system of the current process, and sets
4158 * root/cwd of all processes which had them on the current root to new_root.
4159 *
4160 * Restrictions:
4161 * The new_root and put_old must be directories, and must not be on the
4162 * same file system as the current process root. The put_old must be
4163 * underneath new_root, i.e. adding a non-zero number of /.. to the string
4164 * pointed to by put_old must yield the same directory as new_root. No other
4165 * file system may be mounted on put_old. After all, new_root is a mountpoint.
4166 *
4167 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
4168 * See Documentation/filesystems/ramfs-rootfs-initramfs.rst for alternatives
4169 * in this situation.
4170 *
4171 * Notes:
4172 * - we don't move root/cwd if they are not at the root (reason: if something
4173 * cared enough to change them, it's probably wrong to force them elsewhere)
4174 * - it's okay to pick a root that isn't the root of a file system, e.g.
4175 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
4176 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
4177 * first.
4178 */
4179SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
4180 const char __user *, put_old)
4181{
4182 struct path new, old, root;
4183 struct mount *new_mnt, *root_mnt, *old_mnt, *root_parent, *ex_parent;
4184 struct mountpoint *old_mp, *root_mp;
4185 int error;
4186
4187 if (!may_mount())
4188 return -EPERM;
4189
4190 error = user_path_at(AT_FDCWD, new_root,
4191 LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &new);
4192 if (error)
4193 goto out0;
4194
4195 error = user_path_at(AT_FDCWD, put_old,
4196 LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old);
4197 if (error)
4198 goto out1;
4199
4200 error = security_sb_pivotroot(&old, &new);
4201 if (error)
4202 goto out2;
4203
4204 get_fs_root(current->fs, &root);
4205 old_mp = lock_mount(&old);
4206 error = PTR_ERR(old_mp);
4207 if (IS_ERR(old_mp))
4208 goto out3;
4209
4210 error = -EINVAL;
4211 new_mnt = real_mount(new.mnt);
4212 root_mnt = real_mount(root.mnt);
4213 old_mnt = real_mount(old.mnt);
4214 ex_parent = new_mnt->mnt_parent;
4215 root_parent = root_mnt->mnt_parent;
4216 if (IS_MNT_SHARED(old_mnt) ||
4217 IS_MNT_SHARED(ex_parent) ||
4218 IS_MNT_SHARED(root_parent))
4219 goto out4;
4220 if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
4221 goto out4;
4222 if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
4223 goto out4;
4224 error = -ENOENT;
4225 if (d_unlinked(new.dentry))
4226 goto out4;
4227 error = -EBUSY;
4228 if (new_mnt == root_mnt || old_mnt == root_mnt)
4229 goto out4; /* loop, on the same file system */
4230 error = -EINVAL;
4231 if (!path_mounted(&root))
4232 goto out4; /* not a mountpoint */
4233 if (!mnt_has_parent(root_mnt))
4234 goto out4; /* not attached */
4235 if (!path_mounted(&new))
4236 goto out4; /* not a mountpoint */
4237 if (!mnt_has_parent(new_mnt))
4238 goto out4; /* not attached */
4239 /* make sure we can reach put_old from new_root */
4240 if (!is_path_reachable(old_mnt, old.dentry, &new))
4241 goto out4;
4242 /* make certain new is below the root */
4243 if (!is_path_reachable(new_mnt, new.dentry, &root))
4244 goto out4;
4245 lock_mount_hash();
4246 umount_mnt(new_mnt);
4247 root_mp = unhash_mnt(root_mnt); /* we'll need its mountpoint */
4248 if (root_mnt->mnt.mnt_flags & MNT_LOCKED) {
4249 new_mnt->mnt.mnt_flags |= MNT_LOCKED;
4250 root_mnt->mnt.mnt_flags &= ~MNT_LOCKED;
4251 }
4252 /* mount old root on put_old */
4253 attach_mnt(root_mnt, old_mnt, old_mp, false);
4254 /* mount new_root on / */
4255 attach_mnt(new_mnt, root_parent, root_mp, false);
4256 mnt_add_count(root_parent, -1);
4257 touch_mnt_namespace(current->nsproxy->mnt_ns);
4258 /* A moved mount should not expire automatically */
4259 list_del_init(&new_mnt->mnt_expire);
4260 put_mountpoint(root_mp);
4261 unlock_mount_hash();
4262 chroot_fs_refs(&root, &new);
4263 error = 0;
4264out4:
4265 unlock_mount(old_mp);
4266 if (!error)
4267 mntput_no_expire(ex_parent);
4268out3:
4269 path_put(&root);
4270out2:
4271 path_put(&old);
4272out1:
4273 path_put(&new);
4274out0:
4275 return error;
4276}
4277
4278static unsigned int recalc_flags(struct mount_kattr *kattr, struct mount *mnt)
4279{
4280 unsigned int flags = mnt->mnt.mnt_flags;
4281
4282 /* flags to clear */
4283 flags &= ~kattr->attr_clr;
4284 /* flags to raise */
4285 flags |= kattr->attr_set;
4286
4287 return flags;
4288}
4289
4290static int can_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
4291{
4292 struct vfsmount *m = &mnt->mnt;
4293 struct user_namespace *fs_userns = m->mnt_sb->s_user_ns;
4294
4295 if (!kattr->mnt_idmap)
4296 return 0;
4297
4298 /*
4299 * Creating an idmapped mount with the filesystem wide idmapping
4300 * doesn't make sense so block that. We don't allow mushy semantics.
4301 */
4302 if (kattr->mnt_userns == m->mnt_sb->s_user_ns)
4303 return -EINVAL;
4304
4305 /*
4306 * Once a mount has been idmapped we don't allow it to change its
4307 * mapping. It makes things simpler and callers can just create
4308 * another bind-mount they can idmap if they want to.
4309 */
4310 if (is_idmapped_mnt(m))
4311 return -EPERM;
4312
4313 /* The underlying filesystem doesn't support idmapped mounts yet. */
4314 if (!(m->mnt_sb->s_type->fs_flags & FS_ALLOW_IDMAP))
4315 return -EINVAL;
4316
4317 /* We're not controlling the superblock. */
4318 if (!ns_capable(fs_userns, CAP_SYS_ADMIN))
4319 return -EPERM;
4320
4321 /* Mount has already been visible in the filesystem hierarchy. */
4322 if (!is_anon_ns(mnt->mnt_ns))
4323 return -EINVAL;
4324
4325 return 0;
4326}
4327
4328/**
4329 * mnt_allow_writers() - check whether the attribute change allows writers
4330 * @kattr: the new mount attributes
4331 * @mnt: the mount to which @kattr will be applied
4332 *
4333 * Check whether thew new mount attributes in @kattr allow concurrent writers.
4334 *
4335 * Return: true if writers need to be held, false if not
4336 */
4337static inline bool mnt_allow_writers(const struct mount_kattr *kattr,
4338 const struct mount *mnt)
4339{
4340 return (!(kattr->attr_set & MNT_READONLY) ||
4341 (mnt->mnt.mnt_flags & MNT_READONLY)) &&
4342 !kattr->mnt_idmap;
4343}
4344
4345static int mount_setattr_prepare(struct mount_kattr *kattr, struct mount *mnt)
4346{
4347 struct mount *m;
4348 int err;
4349
4350 for (m = mnt; m; m = next_mnt(m, mnt)) {
4351 if (!can_change_locked_flags(m, recalc_flags(kattr, m))) {
4352 err = -EPERM;
4353 break;
4354 }
4355
4356 err = can_idmap_mount(kattr, m);
4357 if (err)
4358 break;
4359
4360 if (!mnt_allow_writers(kattr, m)) {
4361 err = mnt_hold_writers(m);
4362 if (err)
4363 break;
4364 }
4365
4366 if (!kattr->recurse)
4367 return 0;
4368 }
4369
4370 if (err) {
4371 struct mount *p;
4372
4373 /*
4374 * If we had to call mnt_hold_writers() MNT_WRITE_HOLD will
4375 * be set in @mnt_flags. The loop unsets MNT_WRITE_HOLD for all
4376 * mounts and needs to take care to include the first mount.
4377 */
4378 for (p = mnt; p; p = next_mnt(p, mnt)) {
4379 /* If we had to hold writers unblock them. */
4380 if (p->mnt.mnt_flags & MNT_WRITE_HOLD)
4381 mnt_unhold_writers(p);
4382
4383 /*
4384 * We're done once the first mount we changed got
4385 * MNT_WRITE_HOLD unset.
4386 */
4387 if (p == m)
4388 break;
4389 }
4390 }
4391 return err;
4392}
4393
4394static void do_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
4395{
4396 if (!kattr->mnt_idmap)
4397 return;
4398
4399 /*
4400 * Pairs with smp_load_acquire() in mnt_idmap().
4401 *
4402 * Since we only allow a mount to change the idmapping once and
4403 * verified this in can_idmap_mount() we know that the mount has
4404 * @nop_mnt_idmap attached to it. So there's no need to drop any
4405 * references.
4406 */
4407 smp_store_release(&mnt->mnt.mnt_idmap, mnt_idmap_get(kattr->mnt_idmap));
4408}
4409
4410static void mount_setattr_commit(struct mount_kattr *kattr, struct mount *mnt)
4411{
4412 struct mount *m;
4413
4414 for (m = mnt; m; m = next_mnt(m, mnt)) {
4415 unsigned int flags;
4416
4417 do_idmap_mount(kattr, m);
4418 flags = recalc_flags(kattr, m);
4419 WRITE_ONCE(m->mnt.mnt_flags, flags);
4420
4421 /* If we had to hold writers unblock them. */
4422 if (m->mnt.mnt_flags & MNT_WRITE_HOLD)
4423 mnt_unhold_writers(m);
4424
4425 if (kattr->propagation)
4426 change_mnt_propagation(m, kattr->propagation);
4427 if (!kattr->recurse)
4428 break;
4429 }
4430 touch_mnt_namespace(mnt->mnt_ns);
4431}
4432
4433static int do_mount_setattr(struct path *path, struct mount_kattr *kattr)
4434{
4435 struct mount *mnt = real_mount(path->mnt);
4436 int err = 0;
4437
4438 if (!path_mounted(path))
4439 return -EINVAL;
4440
4441 if (kattr->mnt_userns) {
4442 struct mnt_idmap *mnt_idmap;
4443
4444 mnt_idmap = alloc_mnt_idmap(kattr->mnt_userns);
4445 if (IS_ERR(mnt_idmap))
4446 return PTR_ERR(mnt_idmap);
4447 kattr->mnt_idmap = mnt_idmap;
4448 }
4449
4450 if (kattr->propagation) {
4451 /*
4452 * Only take namespace_lock() if we're actually changing
4453 * propagation.
4454 */
4455 namespace_lock();
4456 if (kattr->propagation == MS_SHARED) {
4457 err = invent_group_ids(mnt, kattr->recurse);
4458 if (err) {
4459 namespace_unlock();
4460 return err;
4461 }
4462 }
4463 }
4464
4465 err = -EINVAL;
4466 lock_mount_hash();
4467
4468 /* Ensure that this isn't anything purely vfs internal. */
4469 if (!is_mounted(&mnt->mnt))
4470 goto out;
4471
4472 /*
4473 * If this is an attached mount make sure it's located in the callers
4474 * mount namespace. If it's not don't let the caller interact with it.
4475 *
4476 * If this mount doesn't have a parent it's most often simply a
4477 * detached mount with an anonymous mount namespace. IOW, something
4478 * that's simply not attached yet. But there are apparently also users
4479 * that do change mount properties on the rootfs itself. That obviously
4480 * neither has a parent nor is it a detached mount so we cannot
4481 * unconditionally check for detached mounts.
4482 */
4483 if ((mnt_has_parent(mnt) || !is_anon_ns(mnt->mnt_ns)) && !check_mnt(mnt))
4484 goto out;
4485
4486 /*
4487 * First, we get the mount tree in a shape where we can change mount
4488 * properties without failure. If we succeeded to do so we commit all
4489 * changes and if we failed we clean up.
4490 */
4491 err = mount_setattr_prepare(kattr, mnt);
4492 if (!err)
4493 mount_setattr_commit(kattr, mnt);
4494
4495out:
4496 unlock_mount_hash();
4497
4498 if (kattr->propagation) {
4499 if (err)
4500 cleanup_group_ids(mnt, NULL);
4501 namespace_unlock();
4502 }
4503
4504 return err;
4505}
4506
4507static int build_mount_idmapped(const struct mount_attr *attr, size_t usize,
4508 struct mount_kattr *kattr, unsigned int flags)
4509{
4510 int err = 0;
4511 struct ns_common *ns;
4512 struct user_namespace *mnt_userns;
4513 struct fd f;
4514
4515 if (!((attr->attr_set | attr->attr_clr) & MOUNT_ATTR_IDMAP))
4516 return 0;
4517
4518 /*
4519 * We currently do not support clearing an idmapped mount. If this ever
4520 * is a use-case we can revisit this but for now let's keep it simple
4521 * and not allow it.
4522 */
4523 if (attr->attr_clr & MOUNT_ATTR_IDMAP)
4524 return -EINVAL;
4525
4526 if (attr->userns_fd > INT_MAX)
4527 return -EINVAL;
4528
4529 f = fdget(attr->userns_fd);
4530 if (!f.file)
4531 return -EBADF;
4532
4533 if (!proc_ns_file(f.file)) {
4534 err = -EINVAL;
4535 goto out_fput;
4536 }
4537
4538 ns = get_proc_ns(file_inode(f.file));
4539 if (ns->ops->type != CLONE_NEWUSER) {
4540 err = -EINVAL;
4541 goto out_fput;
4542 }
4543
4544 /*
4545 * The initial idmapping cannot be used to create an idmapped
4546 * mount. We use the initial idmapping as an indicator of a mount
4547 * that is not idmapped. It can simply be passed into helpers that
4548 * are aware of idmapped mounts as a convenient shortcut. A user
4549 * can just create a dedicated identity mapping to achieve the same
4550 * result.
4551 */
4552 mnt_userns = container_of(ns, struct user_namespace, ns);
4553 if (mnt_userns == &init_user_ns) {
4554 err = -EPERM;
4555 goto out_fput;
4556 }
4557
4558 /* We're not controlling the target namespace. */
4559 if (!ns_capable(mnt_userns, CAP_SYS_ADMIN)) {
4560 err = -EPERM;
4561 goto out_fput;
4562 }
4563
4564 kattr->mnt_userns = get_user_ns(mnt_userns);
4565
4566out_fput:
4567 fdput(f);
4568 return err;
4569}
4570
4571static int build_mount_kattr(const struct mount_attr *attr, size_t usize,
4572 struct mount_kattr *kattr, unsigned int flags)
4573{
4574 unsigned int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW;
4575
4576 if (flags & AT_NO_AUTOMOUNT)
4577 lookup_flags &= ~LOOKUP_AUTOMOUNT;
4578 if (flags & AT_SYMLINK_NOFOLLOW)
4579 lookup_flags &= ~LOOKUP_FOLLOW;
4580 if (flags & AT_EMPTY_PATH)
4581 lookup_flags |= LOOKUP_EMPTY;
4582
4583 *kattr = (struct mount_kattr) {
4584 .lookup_flags = lookup_flags,
4585 .recurse = !!(flags & AT_RECURSIVE),
4586 };
4587
4588 if (attr->propagation & ~MOUNT_SETATTR_PROPAGATION_FLAGS)
4589 return -EINVAL;
4590 if (hweight32(attr->propagation & MOUNT_SETATTR_PROPAGATION_FLAGS) > 1)
4591 return -EINVAL;
4592 kattr->propagation = attr->propagation;
4593
4594 if ((attr->attr_set | attr->attr_clr) & ~MOUNT_SETATTR_VALID_FLAGS)
4595 return -EINVAL;
4596
4597 kattr->attr_set = attr_flags_to_mnt_flags(attr->attr_set);
4598 kattr->attr_clr = attr_flags_to_mnt_flags(attr->attr_clr);
4599
4600 /*
4601 * Since the MOUNT_ATTR_<atime> values are an enum, not a bitmap,
4602 * users wanting to transition to a different atime setting cannot
4603 * simply specify the atime setting in @attr_set, but must also
4604 * specify MOUNT_ATTR__ATIME in the @attr_clr field.
4605 * So ensure that MOUNT_ATTR__ATIME can't be partially set in
4606 * @attr_clr and that @attr_set can't have any atime bits set if
4607 * MOUNT_ATTR__ATIME isn't set in @attr_clr.
4608 */
4609 if (attr->attr_clr & MOUNT_ATTR__ATIME) {
4610 if ((attr->attr_clr & MOUNT_ATTR__ATIME) != MOUNT_ATTR__ATIME)
4611 return -EINVAL;
4612
4613 /*
4614 * Clear all previous time settings as they are mutually
4615 * exclusive.
4616 */
4617 kattr->attr_clr |= MNT_RELATIME | MNT_NOATIME;
4618 switch (attr->attr_set & MOUNT_ATTR__ATIME) {
4619 case MOUNT_ATTR_RELATIME:
4620 kattr->attr_set |= MNT_RELATIME;
4621 break;
4622 case MOUNT_ATTR_NOATIME:
4623 kattr->attr_set |= MNT_NOATIME;
4624 break;
4625 case MOUNT_ATTR_STRICTATIME:
4626 break;
4627 default:
4628 return -EINVAL;
4629 }
4630 } else {
4631 if (attr->attr_set & MOUNT_ATTR__ATIME)
4632 return -EINVAL;
4633 }
4634
4635 return build_mount_idmapped(attr, usize, kattr, flags);
4636}
4637
4638static void finish_mount_kattr(struct mount_kattr *kattr)
4639{
4640 put_user_ns(kattr->mnt_userns);
4641 kattr->mnt_userns = NULL;
4642
4643 if (kattr->mnt_idmap)
4644 mnt_idmap_put(kattr->mnt_idmap);
4645}
4646
4647SYSCALL_DEFINE5(mount_setattr, int, dfd, const char __user *, path,
4648 unsigned int, flags, struct mount_attr __user *, uattr,
4649 size_t, usize)
4650{
4651 int err;
4652 struct path target;
4653 struct mount_attr attr;
4654 struct mount_kattr kattr;
4655
4656 BUILD_BUG_ON(sizeof(struct mount_attr) != MOUNT_ATTR_SIZE_VER0);
4657
4658 if (flags & ~(AT_EMPTY_PATH |
4659 AT_RECURSIVE |
4660 AT_SYMLINK_NOFOLLOW |
4661 AT_NO_AUTOMOUNT))
4662 return -EINVAL;
4663
4664 if (unlikely(usize > PAGE_SIZE))
4665 return -E2BIG;
4666 if (unlikely(usize < MOUNT_ATTR_SIZE_VER0))
4667 return -EINVAL;
4668
4669 if (!may_mount())
4670 return -EPERM;
4671
4672 err = copy_struct_from_user(&attr, sizeof(attr), uattr, usize);
4673 if (err)
4674 return err;
4675
4676 /* Don't bother walking through the mounts if this is a nop. */
4677 if (attr.attr_set == 0 &&
4678 attr.attr_clr == 0 &&
4679 attr.propagation == 0)
4680 return 0;
4681
4682 err = build_mount_kattr(&attr, usize, &kattr, flags);
4683 if (err)
4684 return err;
4685
4686 err = user_path_at(dfd, path, kattr.lookup_flags, &target);
4687 if (!err) {
4688 err = do_mount_setattr(&target, &kattr);
4689 path_put(&target);
4690 }
4691 finish_mount_kattr(&kattr);
4692 return err;
4693}
4694
4695int show_path(struct seq_file *m, struct dentry *root)
4696{
4697 if (root->d_sb->s_op->show_path)
4698 return root->d_sb->s_op->show_path(m, root);
4699
4700 seq_dentry(m, root, " \t\n\\");
4701 return 0;
4702}
4703
4704static struct vfsmount *lookup_mnt_in_ns(u64 id, struct mnt_namespace *ns)
4705{
4706 struct mount *mnt = mnt_find_id_at(ns, id);
4707
4708 if (!mnt || mnt->mnt_id_unique != id)
4709 return NULL;
4710
4711 return &mnt->mnt;
4712}
4713
4714struct kstatmount {
4715 struct statmount __user *buf;
4716 size_t bufsize;
4717 struct vfsmount *mnt;
4718 u64 mask;
4719 struct path root;
4720 struct statmount sm;
4721 struct seq_file seq;
4722};
4723
4724static u64 mnt_to_attr_flags(struct vfsmount *mnt)
4725{
4726 unsigned int mnt_flags = READ_ONCE(mnt->mnt_flags);
4727 u64 attr_flags = 0;
4728
4729 if (mnt_flags & MNT_READONLY)
4730 attr_flags |= MOUNT_ATTR_RDONLY;
4731 if (mnt_flags & MNT_NOSUID)
4732 attr_flags |= MOUNT_ATTR_NOSUID;
4733 if (mnt_flags & MNT_NODEV)
4734 attr_flags |= MOUNT_ATTR_NODEV;
4735 if (mnt_flags & MNT_NOEXEC)
4736 attr_flags |= MOUNT_ATTR_NOEXEC;
4737 if (mnt_flags & MNT_NODIRATIME)
4738 attr_flags |= MOUNT_ATTR_NODIRATIME;
4739 if (mnt_flags & MNT_NOSYMFOLLOW)
4740 attr_flags |= MOUNT_ATTR_NOSYMFOLLOW;
4741
4742 if (mnt_flags & MNT_NOATIME)
4743 attr_flags |= MOUNT_ATTR_NOATIME;
4744 else if (mnt_flags & MNT_RELATIME)
4745 attr_flags |= MOUNT_ATTR_RELATIME;
4746 else
4747 attr_flags |= MOUNT_ATTR_STRICTATIME;
4748
4749 if (is_idmapped_mnt(mnt))
4750 attr_flags |= MOUNT_ATTR_IDMAP;
4751
4752 return attr_flags;
4753}
4754
4755static u64 mnt_to_propagation_flags(struct mount *m)
4756{
4757 u64 propagation = 0;
4758
4759 if (IS_MNT_SHARED(m))
4760 propagation |= MS_SHARED;
4761 if (IS_MNT_SLAVE(m))
4762 propagation |= MS_SLAVE;
4763 if (IS_MNT_UNBINDABLE(m))
4764 propagation |= MS_UNBINDABLE;
4765 if (!propagation)
4766 propagation |= MS_PRIVATE;
4767
4768 return propagation;
4769}
4770
4771static void statmount_sb_basic(struct kstatmount *s)
4772{
4773 struct super_block *sb = s->mnt->mnt_sb;
4774
4775 s->sm.mask |= STATMOUNT_SB_BASIC;
4776 s->sm.sb_dev_major = MAJOR(sb->s_dev);
4777 s->sm.sb_dev_minor = MINOR(sb->s_dev);
4778 s->sm.sb_magic = sb->s_magic;
4779 s->sm.sb_flags = sb->s_flags & (SB_RDONLY|SB_SYNCHRONOUS|SB_DIRSYNC|SB_LAZYTIME);
4780}
4781
4782static void statmount_mnt_basic(struct kstatmount *s)
4783{
4784 struct mount *m = real_mount(s->mnt);
4785
4786 s->sm.mask |= STATMOUNT_MNT_BASIC;
4787 s->sm.mnt_id = m->mnt_id_unique;
4788 s->sm.mnt_parent_id = m->mnt_parent->mnt_id_unique;
4789 s->sm.mnt_id_old = m->mnt_id;
4790 s->sm.mnt_parent_id_old = m->mnt_parent->mnt_id;
4791 s->sm.mnt_attr = mnt_to_attr_flags(&m->mnt);
4792 s->sm.mnt_propagation = mnt_to_propagation_flags(m);
4793 s->sm.mnt_peer_group = IS_MNT_SHARED(m) ? m->mnt_group_id : 0;
4794 s->sm.mnt_master = IS_MNT_SLAVE(m) ? m->mnt_master->mnt_group_id : 0;
4795}
4796
4797static void statmount_propagate_from(struct kstatmount *s)
4798{
4799 struct mount *m = real_mount(s->mnt);
4800
4801 s->sm.mask |= STATMOUNT_PROPAGATE_FROM;
4802 if (IS_MNT_SLAVE(m))
4803 s->sm.propagate_from = get_dominating_id(m, ¤t->fs->root);
4804}
4805
4806static int statmount_mnt_root(struct kstatmount *s, struct seq_file *seq)
4807{
4808 int ret;
4809 size_t start = seq->count;
4810
4811 ret = show_path(seq, s->mnt->mnt_root);
4812 if (ret)
4813 return ret;
4814
4815 if (unlikely(seq_has_overflowed(seq)))
4816 return -EAGAIN;
4817
4818 /*
4819 * Unescape the result. It would be better if supplied string was not
4820 * escaped in the first place, but that's a pretty invasive change.
4821 */
4822 seq->buf[seq->count] = '\0';
4823 seq->count = start;
4824 seq_commit(seq, string_unescape_inplace(seq->buf + start, UNESCAPE_OCTAL));
4825 return 0;
4826}
4827
4828static int statmount_mnt_point(struct kstatmount *s, struct seq_file *seq)
4829{
4830 struct vfsmount *mnt = s->mnt;
4831 struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
4832 int err;
4833
4834 err = seq_path_root(seq, &mnt_path, &s->root, "");
4835 return err == SEQ_SKIP ? 0 : err;
4836}
4837
4838static int statmount_fs_type(struct kstatmount *s, struct seq_file *seq)
4839{
4840 struct super_block *sb = s->mnt->mnt_sb;
4841
4842 seq_puts(seq, sb->s_type->name);
4843 return 0;
4844}
4845
4846static int statmount_string(struct kstatmount *s, u64 flag)
4847{
4848 int ret;
4849 size_t kbufsize;
4850 struct seq_file *seq = &s->seq;
4851 struct statmount *sm = &s->sm;
4852
4853 switch (flag) {
4854 case STATMOUNT_FS_TYPE:
4855 sm->fs_type = seq->count;
4856 ret = statmount_fs_type(s, seq);
4857 break;
4858 case STATMOUNT_MNT_ROOT:
4859 sm->mnt_root = seq->count;
4860 ret = statmount_mnt_root(s, seq);
4861 break;
4862 case STATMOUNT_MNT_POINT:
4863 sm->mnt_point = seq->count;
4864 ret = statmount_mnt_point(s, seq);
4865 break;
4866 default:
4867 WARN_ON_ONCE(true);
4868 return -EINVAL;
4869 }
4870
4871 if (unlikely(check_add_overflow(sizeof(*sm), seq->count, &kbufsize)))
4872 return -EOVERFLOW;
4873 if (kbufsize >= s->bufsize)
4874 return -EOVERFLOW;
4875
4876 /* signal a retry */
4877 if (unlikely(seq_has_overflowed(seq)))
4878 return -EAGAIN;
4879
4880 if (ret)
4881 return ret;
4882
4883 seq->buf[seq->count++] = '\0';
4884 sm->mask |= flag;
4885 return 0;
4886}
4887
4888static int copy_statmount_to_user(struct kstatmount *s)
4889{
4890 struct statmount *sm = &s->sm;
4891 struct seq_file *seq = &s->seq;
4892 char __user *str = ((char __user *)s->buf) + sizeof(*sm);
4893 size_t copysize = min_t(size_t, s->bufsize, sizeof(*sm));
4894
4895 if (seq->count && copy_to_user(str, seq->buf, seq->count))
4896 return -EFAULT;
4897
4898 /* Return the number of bytes copied to the buffer */
4899 sm->size = copysize + seq->count;
4900 if (copy_to_user(s->buf, sm, copysize))
4901 return -EFAULT;
4902
4903 return 0;
4904}
4905
4906static int do_statmount(struct kstatmount *s)
4907{
4908 struct mount *m = real_mount(s->mnt);
4909 int err;
4910
4911 /*
4912 * Don't trigger audit denials. We just want to determine what
4913 * mounts to show users.
4914 */
4915 if (!is_path_reachable(m, m->mnt.mnt_root, &s->root) &&
4916 !ns_capable_noaudit(&init_user_ns, CAP_SYS_ADMIN))
4917 return -EPERM;
4918
4919 err = security_sb_statfs(s->mnt->mnt_root);
4920 if (err)
4921 return err;
4922
4923 if (s->mask & STATMOUNT_SB_BASIC)
4924 statmount_sb_basic(s);
4925
4926 if (s->mask & STATMOUNT_MNT_BASIC)
4927 statmount_mnt_basic(s);
4928
4929 if (s->mask & STATMOUNT_PROPAGATE_FROM)
4930 statmount_propagate_from(s);
4931
4932 if (s->mask & STATMOUNT_FS_TYPE)
4933 err = statmount_string(s, STATMOUNT_FS_TYPE);
4934
4935 if (!err && s->mask & STATMOUNT_MNT_ROOT)
4936 err = statmount_string(s, STATMOUNT_MNT_ROOT);
4937
4938 if (!err && s->mask & STATMOUNT_MNT_POINT)
4939 err = statmount_string(s, STATMOUNT_MNT_POINT);
4940
4941 if (err)
4942 return err;
4943
4944 return 0;
4945}
4946
4947static inline bool retry_statmount(const long ret, size_t *seq_size)
4948{
4949 if (likely(ret != -EAGAIN))
4950 return false;
4951 if (unlikely(check_mul_overflow(*seq_size, 2, seq_size)))
4952 return false;
4953 if (unlikely(*seq_size > MAX_RW_COUNT))
4954 return false;
4955 return true;
4956}
4957
4958static int prepare_kstatmount(struct kstatmount *ks, struct mnt_id_req *kreq,
4959 struct statmount __user *buf, size_t bufsize,
4960 size_t seq_size)
4961{
4962 if (!access_ok(buf, bufsize))
4963 return -EFAULT;
4964
4965 memset(ks, 0, sizeof(*ks));
4966 ks->mask = kreq->param;
4967 ks->buf = buf;
4968 ks->bufsize = bufsize;
4969 ks->seq.size = seq_size;
4970 ks->seq.buf = kvmalloc(seq_size, GFP_KERNEL_ACCOUNT);
4971 if (!ks->seq.buf)
4972 return -ENOMEM;
4973 return 0;
4974}
4975
4976static int copy_mnt_id_req(const struct mnt_id_req __user *req,
4977 struct mnt_id_req *kreq)
4978{
4979 int ret;
4980 size_t usize;
4981
4982 BUILD_BUG_ON(sizeof(struct mnt_id_req) != MNT_ID_REQ_SIZE_VER0);
4983
4984 ret = get_user(usize, &req->size);
4985 if (ret)
4986 return -EFAULT;
4987 if (unlikely(usize > PAGE_SIZE))
4988 return -E2BIG;
4989 if (unlikely(usize < MNT_ID_REQ_SIZE_VER0))
4990 return -EINVAL;
4991 memset(kreq, 0, sizeof(*kreq));
4992 ret = copy_struct_from_user(kreq, sizeof(*kreq), req, usize);
4993 if (ret)
4994 return ret;
4995 if (kreq->spare != 0)
4996 return -EINVAL;
4997 return 0;
4998}
4999
5000SYSCALL_DEFINE4(statmount, const struct mnt_id_req __user *, req,
5001 struct statmount __user *, buf, size_t, bufsize,
5002 unsigned int, flags)
5003{
5004 struct vfsmount *mnt;
5005 struct mnt_id_req kreq;
5006 struct kstatmount ks;
5007 /* We currently support retrieval of 3 strings. */
5008 size_t seq_size = 3 * PATH_MAX;
5009 int ret;
5010
5011 if (flags)
5012 return -EINVAL;
5013
5014 ret = copy_mnt_id_req(req, &kreq);
5015 if (ret)
5016 return ret;
5017
5018retry:
5019 ret = prepare_kstatmount(&ks, &kreq, buf, bufsize, seq_size);
5020 if (ret)
5021 return ret;
5022
5023 down_read(&namespace_sem);
5024 mnt = lookup_mnt_in_ns(kreq.mnt_id, current->nsproxy->mnt_ns);
5025 if (!mnt) {
5026 up_read(&namespace_sem);
5027 kvfree(ks.seq.buf);
5028 return -ENOENT;
5029 }
5030
5031 ks.mnt = mnt;
5032 get_fs_root(current->fs, &ks.root);
5033 ret = do_statmount(&ks);
5034 path_put(&ks.root);
5035 up_read(&namespace_sem);
5036
5037 if (!ret)
5038 ret = copy_statmount_to_user(&ks);
5039 kvfree(ks.seq.buf);
5040 if (retry_statmount(ret, &seq_size))
5041 goto retry;
5042 return ret;
5043}
5044
5045static struct mount *listmnt_next(struct mount *curr)
5046{
5047 return node_to_mount(rb_next(&curr->mnt_node));
5048}
5049
5050static ssize_t do_listmount(struct mount *first, struct path *orig,
5051 u64 mnt_parent_id, u64 __user *mnt_ids,
5052 size_t nr_mnt_ids, const struct path *root)
5053{
5054 struct mount *r;
5055 ssize_t ret;
5056
5057 /*
5058 * Don't trigger audit denials. We just want to determine what
5059 * mounts to show users.
5060 */
5061 if (!is_path_reachable(real_mount(orig->mnt), orig->dentry, root) &&
5062 !ns_capable_noaudit(&init_user_ns, CAP_SYS_ADMIN))
5063 return -EPERM;
5064
5065 ret = security_sb_statfs(orig->dentry);
5066 if (ret)
5067 return ret;
5068
5069 for (ret = 0, r = first; r && nr_mnt_ids; r = listmnt_next(r)) {
5070 if (r->mnt_id_unique == mnt_parent_id)
5071 continue;
5072 if (!is_path_reachable(r, r->mnt.mnt_root, orig))
5073 continue;
5074 if (put_user(r->mnt_id_unique, mnt_ids))
5075 return -EFAULT;
5076 mnt_ids++;
5077 nr_mnt_ids--;
5078 ret++;
5079 }
5080 return ret;
5081}
5082
5083SYSCALL_DEFINE4(listmount, const struct mnt_id_req __user *, req, u64 __user *,
5084 mnt_ids, size_t, nr_mnt_ids, unsigned int, flags)
5085{
5086 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
5087 struct mnt_id_req kreq;
5088 struct mount *first;
5089 struct path root, orig;
5090 u64 mnt_parent_id, last_mnt_id;
5091 const size_t maxcount = (size_t)-1 >> 3;
5092 ssize_t ret;
5093
5094 if (flags)
5095 return -EINVAL;
5096
5097 if (unlikely(nr_mnt_ids > maxcount))
5098 return -EFAULT;
5099
5100 if (!access_ok(mnt_ids, nr_mnt_ids * sizeof(*mnt_ids)))
5101 return -EFAULT;
5102
5103 ret = copy_mnt_id_req(req, &kreq);
5104 if (ret)
5105 return ret;
5106 mnt_parent_id = kreq.mnt_id;
5107 last_mnt_id = kreq.param;
5108
5109 down_read(&namespace_sem);
5110 get_fs_root(current->fs, &root);
5111 if (mnt_parent_id == LSMT_ROOT) {
5112 orig = root;
5113 } else {
5114 ret = -ENOENT;
5115 orig.mnt = lookup_mnt_in_ns(mnt_parent_id, ns);
5116 if (!orig.mnt)
5117 goto err;
5118 orig.dentry = orig.mnt->mnt_root;
5119 }
5120 if (!last_mnt_id)
5121 first = node_to_mount(rb_first(&ns->mounts));
5122 else
5123 first = mnt_find_id_at(ns, last_mnt_id + 1);
5124
5125 ret = do_listmount(first, &orig, mnt_parent_id, mnt_ids, nr_mnt_ids, &root);
5126err:
5127 path_put(&root);
5128 up_read(&namespace_sem);
5129 return ret;
5130}
5131
5132
5133static void __init init_mount_tree(void)
5134{
5135 struct vfsmount *mnt;
5136 struct mount *m;
5137 struct mnt_namespace *ns;
5138 struct path root;
5139
5140 mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", NULL);
5141 if (IS_ERR(mnt))
5142 panic("Can't create rootfs");
5143
5144 ns = alloc_mnt_ns(&init_user_ns, false);
5145 if (IS_ERR(ns))
5146 panic("Can't allocate initial namespace");
5147 m = real_mount(mnt);
5148 ns->root = m;
5149 ns->nr_mounts = 1;
5150 mnt_add_to_ns(ns, m);
5151 init_task.nsproxy->mnt_ns = ns;
5152 get_mnt_ns(ns);
5153
5154 root.mnt = mnt;
5155 root.dentry = mnt->mnt_root;
5156 mnt->mnt_flags |= MNT_LOCKED;
5157
5158 set_fs_pwd(current->fs, &root);
5159 set_fs_root(current->fs, &root);
5160}
5161
5162void __init mnt_init(void)
5163{
5164 int err;
5165
5166 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
5167 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
5168
5169 mount_hashtable = alloc_large_system_hash("Mount-cache",
5170 sizeof(struct hlist_head),
5171 mhash_entries, 19,
5172 HASH_ZERO,
5173 &m_hash_shift, &m_hash_mask, 0, 0);
5174 mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache",
5175 sizeof(struct hlist_head),
5176 mphash_entries, 19,
5177 HASH_ZERO,
5178 &mp_hash_shift, &mp_hash_mask, 0, 0);
5179
5180 if (!mount_hashtable || !mountpoint_hashtable)
5181 panic("Failed to allocate mount hash table\n");
5182
5183 kernfs_init();
5184
5185 err = sysfs_init();
5186 if (err)
5187 printk(KERN_WARNING "%s: sysfs_init error: %d\n",
5188 __func__, err);
5189 fs_kobj = kobject_create_and_add("fs", NULL);
5190 if (!fs_kobj)
5191 printk(KERN_WARNING "%s: kobj create error\n", __func__);
5192 shmem_init();
5193 init_rootfs();
5194 init_mount_tree();
5195}
5196
5197void put_mnt_ns(struct mnt_namespace *ns)
5198{
5199 if (!refcount_dec_and_test(&ns->ns.count))
5200 return;
5201 drop_collected_mounts(&ns->root->mnt);
5202 free_mnt_ns(ns);
5203}
5204
5205struct vfsmount *kern_mount(struct file_system_type *type)
5206{
5207 struct vfsmount *mnt;
5208 mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
5209 if (!IS_ERR(mnt)) {
5210 /*
5211 * it is a longterm mount, don't release mnt until
5212 * we unmount before file sys is unregistered
5213 */
5214 real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
5215 }
5216 return mnt;
5217}
5218EXPORT_SYMBOL_GPL(kern_mount);
5219
5220void kern_unmount(struct vfsmount *mnt)
5221{
5222 /* release long term mount so mount point can be released */
5223 if (!IS_ERR(mnt)) {
5224 mnt_make_shortterm(mnt);
5225 synchronize_rcu(); /* yecchhh... */
5226 mntput(mnt);
5227 }
5228}
5229EXPORT_SYMBOL(kern_unmount);
5230
5231void kern_unmount_array(struct vfsmount *mnt[], unsigned int num)
5232{
5233 unsigned int i;
5234
5235 for (i = 0; i < num; i++)
5236 mnt_make_shortterm(mnt[i]);
5237 synchronize_rcu_expedited();
5238 for (i = 0; i < num; i++)
5239 mntput(mnt[i]);
5240}
5241EXPORT_SYMBOL(kern_unmount_array);
5242
5243bool our_mnt(struct vfsmount *mnt)
5244{
5245 return check_mnt(real_mount(mnt));
5246}
5247
5248bool current_chrooted(void)
5249{
5250 /* Does the current process have a non-standard root */
5251 struct path ns_root;
5252 struct path fs_root;
5253 bool chrooted;
5254
5255 /* Find the namespace root */
5256 ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt;
5257 ns_root.dentry = ns_root.mnt->mnt_root;
5258 path_get(&ns_root);
5259 while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root))
5260 ;
5261
5262 get_fs_root(current->fs, &fs_root);
5263
5264 chrooted = !path_equal(&fs_root, &ns_root);
5265
5266 path_put(&fs_root);
5267 path_put(&ns_root);
5268
5269 return chrooted;
5270}
5271
5272static bool mnt_already_visible(struct mnt_namespace *ns,
5273 const struct super_block *sb,
5274 int *new_mnt_flags)
5275{
5276 int new_flags = *new_mnt_flags;
5277 struct mount *mnt, *n;
5278 bool visible = false;
5279
5280 down_read(&namespace_sem);
5281 rbtree_postorder_for_each_entry_safe(mnt, n, &ns->mounts, mnt_node) {
5282 struct mount *child;
5283 int mnt_flags;
5284
5285 if (mnt->mnt.mnt_sb->s_type != sb->s_type)
5286 continue;
5287
5288 /* This mount is not fully visible if it's root directory
5289 * is not the root directory of the filesystem.
5290 */
5291 if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root)
5292 continue;
5293
5294 /* A local view of the mount flags */
5295 mnt_flags = mnt->mnt.mnt_flags;
5296
5297 /* Don't miss readonly hidden in the superblock flags */
5298 if (sb_rdonly(mnt->mnt.mnt_sb))
5299 mnt_flags |= MNT_LOCK_READONLY;
5300
5301 /* Verify the mount flags are equal to or more permissive
5302 * than the proposed new mount.
5303 */
5304 if ((mnt_flags & MNT_LOCK_READONLY) &&
5305 !(new_flags & MNT_READONLY))
5306 continue;
5307 if ((mnt_flags & MNT_LOCK_ATIME) &&
5308 ((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK)))
5309 continue;
5310
5311 /* This mount is not fully visible if there are any
5312 * locked child mounts that cover anything except for
5313 * empty directories.
5314 */
5315 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
5316 struct inode *inode = child->mnt_mountpoint->d_inode;
5317 /* Only worry about locked mounts */
5318 if (!(child->mnt.mnt_flags & MNT_LOCKED))
5319 continue;
5320 /* Is the directory permanetly empty? */
5321 if (!is_empty_dir_inode(inode))
5322 goto next;
5323 }
5324 /* Preserve the locked attributes */
5325 *new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \
5326 MNT_LOCK_ATIME);
5327 visible = true;
5328 goto found;
5329 next: ;
5330 }
5331found:
5332 up_read(&namespace_sem);
5333 return visible;
5334}
5335
5336static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags)
5337{
5338 const unsigned long required_iflags = SB_I_NOEXEC | SB_I_NODEV;
5339 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
5340 unsigned long s_iflags;
5341
5342 if (ns->user_ns == &init_user_ns)
5343 return false;
5344
5345 /* Can this filesystem be too revealing? */
5346 s_iflags = sb->s_iflags;
5347 if (!(s_iflags & SB_I_USERNS_VISIBLE))
5348 return false;
5349
5350 if ((s_iflags & required_iflags) != required_iflags) {
5351 WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n",
5352 required_iflags);
5353 return true;
5354 }
5355
5356 return !mnt_already_visible(ns, sb, new_mnt_flags);
5357}
5358
5359bool mnt_may_suid(struct vfsmount *mnt)
5360{
5361 /*
5362 * Foreign mounts (accessed via fchdir or through /proc
5363 * symlinks) are always treated as if they are nosuid. This
5364 * prevents namespaces from trusting potentially unsafe
5365 * suid/sgid bits, file caps, or security labels that originate
5366 * in other namespaces.
5367 */
5368 return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) &&
5369 current_in_userns(mnt->mnt_sb->s_user_ns);
5370}
5371
5372static struct ns_common *mntns_get(struct task_struct *task)
5373{
5374 struct ns_common *ns = NULL;
5375 struct nsproxy *nsproxy;
5376
5377 task_lock(task);
5378 nsproxy = task->nsproxy;
5379 if (nsproxy) {
5380 ns = &nsproxy->mnt_ns->ns;
5381 get_mnt_ns(to_mnt_ns(ns));
5382 }
5383 task_unlock(task);
5384
5385 return ns;
5386}
5387
5388static void mntns_put(struct ns_common *ns)
5389{
5390 put_mnt_ns(to_mnt_ns(ns));
5391}
5392
5393static int mntns_install(struct nsset *nsset, struct ns_common *ns)
5394{
5395 struct nsproxy *nsproxy = nsset->nsproxy;
5396 struct fs_struct *fs = nsset->fs;
5397 struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns;
5398 struct user_namespace *user_ns = nsset->cred->user_ns;
5399 struct path root;
5400 int err;
5401
5402 if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
5403 !ns_capable(user_ns, CAP_SYS_CHROOT) ||
5404 !ns_capable(user_ns, CAP_SYS_ADMIN))
5405 return -EPERM;
5406
5407 if (is_anon_ns(mnt_ns))
5408 return -EINVAL;
5409
5410 if (fs->users != 1)
5411 return -EINVAL;
5412
5413 get_mnt_ns(mnt_ns);
5414 old_mnt_ns = nsproxy->mnt_ns;
5415 nsproxy->mnt_ns = mnt_ns;
5416
5417 /* Find the root */
5418 err = vfs_path_lookup(mnt_ns->root->mnt.mnt_root, &mnt_ns->root->mnt,
5419 "/", LOOKUP_DOWN, &root);
5420 if (err) {
5421 /* revert to old namespace */
5422 nsproxy->mnt_ns = old_mnt_ns;
5423 put_mnt_ns(mnt_ns);
5424 return err;
5425 }
5426
5427 put_mnt_ns(old_mnt_ns);
5428
5429 /* Update the pwd and root */
5430 set_fs_pwd(fs, &root);
5431 set_fs_root(fs, &root);
5432
5433 path_put(&root);
5434 return 0;
5435}
5436
5437static struct user_namespace *mntns_owner(struct ns_common *ns)
5438{
5439 return to_mnt_ns(ns)->user_ns;
5440}
5441
5442const struct proc_ns_operations mntns_operations = {
5443 .name = "mnt",
5444 .type = CLONE_NEWNS,
5445 .get = mntns_get,
5446 .put = mntns_put,
5447 .install = mntns_install,
5448 .owner = mntns_owner,
5449};
5450
5451#ifdef CONFIG_SYSCTL
5452static struct ctl_table fs_namespace_sysctls[] = {
5453 {
5454 .procname = "mount-max",
5455 .data = &sysctl_mount_max,
5456 .maxlen = sizeof(unsigned int),
5457 .mode = 0644,
5458 .proc_handler = proc_dointvec_minmax,
5459 .extra1 = SYSCTL_ONE,
5460 },
5461};
5462
5463static int __init init_fs_namespace_sysctls(void)
5464{
5465 register_sysctl_init("fs", fs_namespace_sysctls);
5466 return 0;
5467}
5468fs_initcall(init_fs_namespace_sysctls);
5469
5470#endif /* CONFIG_SYSCTL */