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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/fs/namespace.c
4 *
5 * (C) Copyright Al Viro 2000, 2001
6 *
7 * Based on code from fs/super.c, copyright Linus Torvalds and others.
8 * Heavily rewritten.
9 */
10
11#include <linux/syscalls.h>
12#include <linux/export.h>
13#include <linux/capability.h>
14#include <linux/mnt_namespace.h>
15#include <linux/user_namespace.h>
16#include <linux/namei.h>
17#include <linux/security.h>
18#include <linux/cred.h>
19#include <linux/idr.h>
20#include <linux/init.h> /* init_rootfs */
21#include <linux/fs_struct.h> /* get_fs_root et.al. */
22#include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */
23#include <linux/file.h>
24#include <linux/uaccess.h>
25#include <linux/proc_ns.h>
26#include <linux/magic.h>
27#include <linux/memblock.h>
28#include <linux/proc_fs.h>
29#include <linux/task_work.h>
30#include <linux/sched/task.h>
31#include <uapi/linux/mount.h>
32#include <linux/fs_context.h>
33#include <linux/shmem_fs.h>
34
35#include "pnode.h"
36#include "internal.h"
37
38/* Maximum number of mounts in a mount namespace */
39unsigned int sysctl_mount_max __read_mostly = 100000;
40
41static unsigned int m_hash_mask __read_mostly;
42static unsigned int m_hash_shift __read_mostly;
43static unsigned int mp_hash_mask __read_mostly;
44static unsigned int mp_hash_shift __read_mostly;
45
46static __initdata unsigned long mhash_entries;
47static int __init set_mhash_entries(char *str)
48{
49 if (!str)
50 return 0;
51 mhash_entries = simple_strtoul(str, &str, 0);
52 return 1;
53}
54__setup("mhash_entries=", set_mhash_entries);
55
56static __initdata unsigned long mphash_entries;
57static int __init set_mphash_entries(char *str)
58{
59 if (!str)
60 return 0;
61 mphash_entries = simple_strtoul(str, &str, 0);
62 return 1;
63}
64__setup("mphash_entries=", set_mphash_entries);
65
66static u64 event;
67static DEFINE_IDA(mnt_id_ida);
68static DEFINE_IDA(mnt_group_ida);
69
70static struct hlist_head *mount_hashtable __read_mostly;
71static struct hlist_head *mountpoint_hashtable __read_mostly;
72static struct kmem_cache *mnt_cache __read_mostly;
73static DECLARE_RWSEM(namespace_sem);
74static HLIST_HEAD(unmounted); /* protected by namespace_sem */
75static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */
76
77struct mount_kattr {
78 unsigned int attr_set;
79 unsigned int attr_clr;
80 unsigned int propagation;
81 unsigned int lookup_flags;
82 bool recurse;
83 struct user_namespace *mnt_userns;
84};
85
86/* /sys/fs */
87struct kobject *fs_kobj;
88EXPORT_SYMBOL_GPL(fs_kobj);
89
90/*
91 * vfsmount lock may be taken for read to prevent changes to the
92 * vfsmount hash, ie. during mountpoint lookups or walking back
93 * up the tree.
94 *
95 * It should be taken for write in all cases where the vfsmount
96 * tree or hash is modified or when a vfsmount structure is modified.
97 */
98__cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock);
99
100static inline void lock_mount_hash(void)
101{
102 write_seqlock(&mount_lock);
103}
104
105static inline void unlock_mount_hash(void)
106{
107 write_sequnlock(&mount_lock);
108}
109
110static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry)
111{
112 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
113 tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
114 tmp = tmp + (tmp >> m_hash_shift);
115 return &mount_hashtable[tmp & m_hash_mask];
116}
117
118static inline struct hlist_head *mp_hash(struct dentry *dentry)
119{
120 unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES);
121 tmp = tmp + (tmp >> mp_hash_shift);
122 return &mountpoint_hashtable[tmp & mp_hash_mask];
123}
124
125static int mnt_alloc_id(struct mount *mnt)
126{
127 int res = ida_alloc(&mnt_id_ida, GFP_KERNEL);
128
129 if (res < 0)
130 return res;
131 mnt->mnt_id = res;
132 return 0;
133}
134
135static void mnt_free_id(struct mount *mnt)
136{
137 ida_free(&mnt_id_ida, mnt->mnt_id);
138}
139
140/*
141 * Allocate a new peer group ID
142 */
143static int mnt_alloc_group_id(struct mount *mnt)
144{
145 int res = ida_alloc_min(&mnt_group_ida, 1, GFP_KERNEL);
146
147 if (res < 0)
148 return res;
149 mnt->mnt_group_id = res;
150 return 0;
151}
152
153/*
154 * Release a peer group ID
155 */
156void mnt_release_group_id(struct mount *mnt)
157{
158 ida_free(&mnt_group_ida, mnt->mnt_group_id);
159 mnt->mnt_group_id = 0;
160}
161
162/*
163 * vfsmount lock must be held for read
164 */
165static inline void mnt_add_count(struct mount *mnt, int n)
166{
167#ifdef CONFIG_SMP
168 this_cpu_add(mnt->mnt_pcp->mnt_count, n);
169#else
170 preempt_disable();
171 mnt->mnt_count += n;
172 preempt_enable();
173#endif
174}
175
176/*
177 * vfsmount lock must be held for write
178 */
179int mnt_get_count(struct mount *mnt)
180{
181#ifdef CONFIG_SMP
182 int count = 0;
183 int cpu;
184
185 for_each_possible_cpu(cpu) {
186 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
187 }
188
189 return count;
190#else
191 return mnt->mnt_count;
192#endif
193}
194
195static struct mount *alloc_vfsmnt(const char *name)
196{
197 struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
198 if (mnt) {
199 int err;
200
201 err = mnt_alloc_id(mnt);
202 if (err)
203 goto out_free_cache;
204
205 if (name) {
206 mnt->mnt_devname = kstrdup_const(name, GFP_KERNEL);
207 if (!mnt->mnt_devname)
208 goto out_free_id;
209 }
210
211#ifdef CONFIG_SMP
212 mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
213 if (!mnt->mnt_pcp)
214 goto out_free_devname;
215
216 this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
217#else
218 mnt->mnt_count = 1;
219 mnt->mnt_writers = 0;
220#endif
221
222 INIT_HLIST_NODE(&mnt->mnt_hash);
223 INIT_LIST_HEAD(&mnt->mnt_child);
224 INIT_LIST_HEAD(&mnt->mnt_mounts);
225 INIT_LIST_HEAD(&mnt->mnt_list);
226 INIT_LIST_HEAD(&mnt->mnt_expire);
227 INIT_LIST_HEAD(&mnt->mnt_share);
228 INIT_LIST_HEAD(&mnt->mnt_slave_list);
229 INIT_LIST_HEAD(&mnt->mnt_slave);
230 INIT_HLIST_NODE(&mnt->mnt_mp_list);
231 INIT_LIST_HEAD(&mnt->mnt_umounting);
232 INIT_HLIST_HEAD(&mnt->mnt_stuck_children);
233 mnt->mnt.mnt_userns = &init_user_ns;
234 }
235 return mnt;
236
237#ifdef CONFIG_SMP
238out_free_devname:
239 kfree_const(mnt->mnt_devname);
240#endif
241out_free_id:
242 mnt_free_id(mnt);
243out_free_cache:
244 kmem_cache_free(mnt_cache, mnt);
245 return NULL;
246}
247
248/*
249 * Most r/o checks on a fs are for operations that take
250 * discrete amounts of time, like a write() or unlink().
251 * We must keep track of when those operations start
252 * (for permission checks) and when they end, so that
253 * we can determine when writes are able to occur to
254 * a filesystem.
255 */
256/*
257 * __mnt_is_readonly: check whether a mount is read-only
258 * @mnt: the mount to check for its write status
259 *
260 * This shouldn't be used directly ouside of the VFS.
261 * It does not guarantee that the filesystem will stay
262 * r/w, just that it is right *now*. This can not and
263 * should not be used in place of IS_RDONLY(inode).
264 * mnt_want/drop_write() will _keep_ the filesystem
265 * r/w.
266 */
267bool __mnt_is_readonly(struct vfsmount *mnt)
268{
269 return (mnt->mnt_flags & MNT_READONLY) || sb_rdonly(mnt->mnt_sb);
270}
271EXPORT_SYMBOL_GPL(__mnt_is_readonly);
272
273static inline void mnt_inc_writers(struct mount *mnt)
274{
275#ifdef CONFIG_SMP
276 this_cpu_inc(mnt->mnt_pcp->mnt_writers);
277#else
278 mnt->mnt_writers++;
279#endif
280}
281
282static inline void mnt_dec_writers(struct mount *mnt)
283{
284#ifdef CONFIG_SMP
285 this_cpu_dec(mnt->mnt_pcp->mnt_writers);
286#else
287 mnt->mnt_writers--;
288#endif
289}
290
291static unsigned int mnt_get_writers(struct mount *mnt)
292{
293#ifdef CONFIG_SMP
294 unsigned int count = 0;
295 int cpu;
296
297 for_each_possible_cpu(cpu) {
298 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
299 }
300
301 return count;
302#else
303 return mnt->mnt_writers;
304#endif
305}
306
307static int mnt_is_readonly(struct vfsmount *mnt)
308{
309 if (mnt->mnt_sb->s_readonly_remount)
310 return 1;
311 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
312 smp_rmb();
313 return __mnt_is_readonly(mnt);
314}
315
316/*
317 * Most r/o & frozen checks on a fs are for operations that take discrete
318 * amounts of time, like a write() or unlink(). We must keep track of when
319 * those operations start (for permission checks) and when they end, so that we
320 * can determine when writes are able to occur to a filesystem.
321 */
322/**
323 * __mnt_want_write - get write access to a mount without freeze protection
324 * @m: the mount on which to take a write
325 *
326 * This tells the low-level filesystem that a write is about to be performed to
327 * it, and makes sure that writes are allowed (mnt it read-write) before
328 * returning success. This operation does not protect against filesystem being
329 * frozen. When the write operation is finished, __mnt_drop_write() must be
330 * called. This is effectively a refcount.
331 */
332int __mnt_want_write(struct vfsmount *m)
333{
334 struct mount *mnt = real_mount(m);
335 int ret = 0;
336
337 preempt_disable();
338 mnt_inc_writers(mnt);
339 /*
340 * The store to mnt_inc_writers must be visible before we pass
341 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
342 * incremented count after it has set MNT_WRITE_HOLD.
343 */
344 smp_mb();
345 while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
346 cpu_relax();
347 /*
348 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
349 * be set to match its requirements. So we must not load that until
350 * MNT_WRITE_HOLD is cleared.
351 */
352 smp_rmb();
353 if (mnt_is_readonly(m)) {
354 mnt_dec_writers(mnt);
355 ret = -EROFS;
356 }
357 preempt_enable();
358
359 return ret;
360}
361
362/**
363 * mnt_want_write - get write access to a mount
364 * @m: the mount on which to take a write
365 *
366 * This tells the low-level filesystem that a write is about to be performed to
367 * it, and makes sure that writes are allowed (mount is read-write, filesystem
368 * is not frozen) before returning success. When the write operation is
369 * finished, mnt_drop_write() must be called. This is effectively a refcount.
370 */
371int mnt_want_write(struct vfsmount *m)
372{
373 int ret;
374
375 sb_start_write(m->mnt_sb);
376 ret = __mnt_want_write(m);
377 if (ret)
378 sb_end_write(m->mnt_sb);
379 return ret;
380}
381EXPORT_SYMBOL_GPL(mnt_want_write);
382
383/**
384 * __mnt_want_write_file - get write access to a file's mount
385 * @file: the file who's mount on which to take a write
386 *
387 * This is like __mnt_want_write, but if the file is already open for writing it
388 * skips incrementing mnt_writers (since the open file already has a reference)
389 * and instead only does the check for emergency r/o remounts. This must be
390 * paired with __mnt_drop_write_file.
391 */
392int __mnt_want_write_file(struct file *file)
393{
394 if (file->f_mode & FMODE_WRITER) {
395 /*
396 * Superblock may have become readonly while there are still
397 * writable fd's, e.g. due to a fs error with errors=remount-ro
398 */
399 if (__mnt_is_readonly(file->f_path.mnt))
400 return -EROFS;
401 return 0;
402 }
403 return __mnt_want_write(file->f_path.mnt);
404}
405
406/**
407 * mnt_want_write_file - get write access to a file's mount
408 * @file: the file who's mount on which to take a write
409 *
410 * This is like mnt_want_write, but if the file is already open for writing it
411 * skips incrementing mnt_writers (since the open file already has a reference)
412 * and instead only does the freeze protection and the check for emergency r/o
413 * remounts. This must be paired with mnt_drop_write_file.
414 */
415int mnt_want_write_file(struct file *file)
416{
417 int ret;
418
419 sb_start_write(file_inode(file)->i_sb);
420 ret = __mnt_want_write_file(file);
421 if (ret)
422 sb_end_write(file_inode(file)->i_sb);
423 return ret;
424}
425EXPORT_SYMBOL_GPL(mnt_want_write_file);
426
427/**
428 * __mnt_drop_write - give up write access to a mount
429 * @mnt: the mount on which to give up write access
430 *
431 * Tells the low-level filesystem that we are done
432 * performing writes to it. Must be matched with
433 * __mnt_want_write() call above.
434 */
435void __mnt_drop_write(struct vfsmount *mnt)
436{
437 preempt_disable();
438 mnt_dec_writers(real_mount(mnt));
439 preempt_enable();
440}
441
442/**
443 * mnt_drop_write - give up write access to a mount
444 * @mnt: the mount on which to give up write access
445 *
446 * Tells the low-level filesystem that we are done performing writes to it and
447 * also allows filesystem to be frozen again. Must be matched with
448 * mnt_want_write() call above.
449 */
450void mnt_drop_write(struct vfsmount *mnt)
451{
452 __mnt_drop_write(mnt);
453 sb_end_write(mnt->mnt_sb);
454}
455EXPORT_SYMBOL_GPL(mnt_drop_write);
456
457void __mnt_drop_write_file(struct file *file)
458{
459 if (!(file->f_mode & FMODE_WRITER))
460 __mnt_drop_write(file->f_path.mnt);
461}
462
463void mnt_drop_write_file(struct file *file)
464{
465 __mnt_drop_write_file(file);
466 sb_end_write(file_inode(file)->i_sb);
467}
468EXPORT_SYMBOL(mnt_drop_write_file);
469
470static inline int mnt_hold_writers(struct mount *mnt)
471{
472 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
473 /*
474 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
475 * should be visible before we do.
476 */
477 smp_mb();
478
479 /*
480 * With writers on hold, if this value is zero, then there are
481 * definitely no active writers (although held writers may subsequently
482 * increment the count, they'll have to wait, and decrement it after
483 * seeing MNT_READONLY).
484 *
485 * It is OK to have counter incremented on one CPU and decremented on
486 * another: the sum will add up correctly. The danger would be when we
487 * sum up each counter, if we read a counter before it is incremented,
488 * but then read another CPU's count which it has been subsequently
489 * decremented from -- we would see more decrements than we should.
490 * MNT_WRITE_HOLD protects against this scenario, because
491 * mnt_want_write first increments count, then smp_mb, then spins on
492 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
493 * we're counting up here.
494 */
495 if (mnt_get_writers(mnt) > 0)
496 return -EBUSY;
497
498 return 0;
499}
500
501static inline void mnt_unhold_writers(struct mount *mnt)
502{
503 /*
504 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
505 * that become unheld will see MNT_READONLY.
506 */
507 smp_wmb();
508 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
509}
510
511static int mnt_make_readonly(struct mount *mnt)
512{
513 int ret;
514
515 ret = mnt_hold_writers(mnt);
516 if (!ret)
517 mnt->mnt.mnt_flags |= MNT_READONLY;
518 mnt_unhold_writers(mnt);
519 return ret;
520}
521
522int sb_prepare_remount_readonly(struct super_block *sb)
523{
524 struct mount *mnt;
525 int err = 0;
526
527 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
528 if (atomic_long_read(&sb->s_remove_count))
529 return -EBUSY;
530
531 lock_mount_hash();
532 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
533 if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
534 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
535 smp_mb();
536 if (mnt_get_writers(mnt) > 0) {
537 err = -EBUSY;
538 break;
539 }
540 }
541 }
542 if (!err && atomic_long_read(&sb->s_remove_count))
543 err = -EBUSY;
544
545 if (!err) {
546 sb->s_readonly_remount = 1;
547 smp_wmb();
548 }
549 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
550 if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
551 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
552 }
553 unlock_mount_hash();
554
555 return err;
556}
557
558static void free_vfsmnt(struct mount *mnt)
559{
560 struct user_namespace *mnt_userns;
561
562 mnt_userns = mnt_user_ns(&mnt->mnt);
563 if (mnt_userns != &init_user_ns)
564 put_user_ns(mnt_userns);
565 kfree_const(mnt->mnt_devname);
566#ifdef CONFIG_SMP
567 free_percpu(mnt->mnt_pcp);
568#endif
569 kmem_cache_free(mnt_cache, mnt);
570}
571
572static void delayed_free_vfsmnt(struct rcu_head *head)
573{
574 free_vfsmnt(container_of(head, struct mount, mnt_rcu));
575}
576
577/* call under rcu_read_lock */
578int __legitimize_mnt(struct vfsmount *bastard, unsigned seq)
579{
580 struct mount *mnt;
581 if (read_seqretry(&mount_lock, seq))
582 return 1;
583 if (bastard == NULL)
584 return 0;
585 mnt = real_mount(bastard);
586 mnt_add_count(mnt, 1);
587 smp_mb(); // see mntput_no_expire()
588 if (likely(!read_seqretry(&mount_lock, seq)))
589 return 0;
590 if (bastard->mnt_flags & MNT_SYNC_UMOUNT) {
591 mnt_add_count(mnt, -1);
592 return 1;
593 }
594 lock_mount_hash();
595 if (unlikely(bastard->mnt_flags & MNT_DOOMED)) {
596 mnt_add_count(mnt, -1);
597 unlock_mount_hash();
598 return 1;
599 }
600 unlock_mount_hash();
601 /* caller will mntput() */
602 return -1;
603}
604
605/* call under rcu_read_lock */
606bool legitimize_mnt(struct vfsmount *bastard, unsigned seq)
607{
608 int res = __legitimize_mnt(bastard, seq);
609 if (likely(!res))
610 return true;
611 if (unlikely(res < 0)) {
612 rcu_read_unlock();
613 mntput(bastard);
614 rcu_read_lock();
615 }
616 return false;
617}
618
619/*
620 * find the first mount at @dentry on vfsmount @mnt.
621 * call under rcu_read_lock()
622 */
623struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
624{
625 struct hlist_head *head = m_hash(mnt, dentry);
626 struct mount *p;
627
628 hlist_for_each_entry_rcu(p, head, mnt_hash)
629 if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
630 return p;
631 return NULL;
632}
633
634/*
635 * lookup_mnt - Return the first child mount mounted at path
636 *
637 * "First" means first mounted chronologically. If you create the
638 * following mounts:
639 *
640 * mount /dev/sda1 /mnt
641 * mount /dev/sda2 /mnt
642 * mount /dev/sda3 /mnt
643 *
644 * Then lookup_mnt() on the base /mnt dentry in the root mount will
645 * return successively the root dentry and vfsmount of /dev/sda1, then
646 * /dev/sda2, then /dev/sda3, then NULL.
647 *
648 * lookup_mnt takes a reference to the found vfsmount.
649 */
650struct vfsmount *lookup_mnt(const struct path *path)
651{
652 struct mount *child_mnt;
653 struct vfsmount *m;
654 unsigned seq;
655
656 rcu_read_lock();
657 do {
658 seq = read_seqbegin(&mount_lock);
659 child_mnt = __lookup_mnt(path->mnt, path->dentry);
660 m = child_mnt ? &child_mnt->mnt : NULL;
661 } while (!legitimize_mnt(m, seq));
662 rcu_read_unlock();
663 return m;
664}
665
666static inline void lock_ns_list(struct mnt_namespace *ns)
667{
668 spin_lock(&ns->ns_lock);
669}
670
671static inline void unlock_ns_list(struct mnt_namespace *ns)
672{
673 spin_unlock(&ns->ns_lock);
674}
675
676static inline bool mnt_is_cursor(struct mount *mnt)
677{
678 return mnt->mnt.mnt_flags & MNT_CURSOR;
679}
680
681/*
682 * __is_local_mountpoint - Test to see if dentry is a mountpoint in the
683 * current mount namespace.
684 *
685 * The common case is dentries are not mountpoints at all and that
686 * test is handled inline. For the slow case when we are actually
687 * dealing with a mountpoint of some kind, walk through all of the
688 * mounts in the current mount namespace and test to see if the dentry
689 * is a mountpoint.
690 *
691 * The mount_hashtable is not usable in the context because we
692 * need to identify all mounts that may be in the current mount
693 * namespace not just a mount that happens to have some specified
694 * parent mount.
695 */
696bool __is_local_mountpoint(struct dentry *dentry)
697{
698 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
699 struct mount *mnt;
700 bool is_covered = false;
701
702 down_read(&namespace_sem);
703 lock_ns_list(ns);
704 list_for_each_entry(mnt, &ns->list, mnt_list) {
705 if (mnt_is_cursor(mnt))
706 continue;
707 is_covered = (mnt->mnt_mountpoint == dentry);
708 if (is_covered)
709 break;
710 }
711 unlock_ns_list(ns);
712 up_read(&namespace_sem);
713
714 return is_covered;
715}
716
717static struct mountpoint *lookup_mountpoint(struct dentry *dentry)
718{
719 struct hlist_head *chain = mp_hash(dentry);
720 struct mountpoint *mp;
721
722 hlist_for_each_entry(mp, chain, m_hash) {
723 if (mp->m_dentry == dentry) {
724 mp->m_count++;
725 return mp;
726 }
727 }
728 return NULL;
729}
730
731static struct mountpoint *get_mountpoint(struct dentry *dentry)
732{
733 struct mountpoint *mp, *new = NULL;
734 int ret;
735
736 if (d_mountpoint(dentry)) {
737 /* might be worth a WARN_ON() */
738 if (d_unlinked(dentry))
739 return ERR_PTR(-ENOENT);
740mountpoint:
741 read_seqlock_excl(&mount_lock);
742 mp = lookup_mountpoint(dentry);
743 read_sequnlock_excl(&mount_lock);
744 if (mp)
745 goto done;
746 }
747
748 if (!new)
749 new = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
750 if (!new)
751 return ERR_PTR(-ENOMEM);
752
753
754 /* Exactly one processes may set d_mounted */
755 ret = d_set_mounted(dentry);
756
757 /* Someone else set d_mounted? */
758 if (ret == -EBUSY)
759 goto mountpoint;
760
761 /* The dentry is not available as a mountpoint? */
762 mp = ERR_PTR(ret);
763 if (ret)
764 goto done;
765
766 /* Add the new mountpoint to the hash table */
767 read_seqlock_excl(&mount_lock);
768 new->m_dentry = dget(dentry);
769 new->m_count = 1;
770 hlist_add_head(&new->m_hash, mp_hash(dentry));
771 INIT_HLIST_HEAD(&new->m_list);
772 read_sequnlock_excl(&mount_lock);
773
774 mp = new;
775 new = NULL;
776done:
777 kfree(new);
778 return mp;
779}
780
781/*
782 * vfsmount lock must be held. Additionally, the caller is responsible
783 * for serializing calls for given disposal list.
784 */
785static void __put_mountpoint(struct mountpoint *mp, struct list_head *list)
786{
787 if (!--mp->m_count) {
788 struct dentry *dentry = mp->m_dentry;
789 BUG_ON(!hlist_empty(&mp->m_list));
790 spin_lock(&dentry->d_lock);
791 dentry->d_flags &= ~DCACHE_MOUNTED;
792 spin_unlock(&dentry->d_lock);
793 dput_to_list(dentry, list);
794 hlist_del(&mp->m_hash);
795 kfree(mp);
796 }
797}
798
799/* called with namespace_lock and vfsmount lock */
800static void put_mountpoint(struct mountpoint *mp)
801{
802 __put_mountpoint(mp, &ex_mountpoints);
803}
804
805static inline int check_mnt(struct mount *mnt)
806{
807 return mnt->mnt_ns == current->nsproxy->mnt_ns;
808}
809
810/*
811 * vfsmount lock must be held for write
812 */
813static void touch_mnt_namespace(struct mnt_namespace *ns)
814{
815 if (ns) {
816 ns->event = ++event;
817 wake_up_interruptible(&ns->poll);
818 }
819}
820
821/*
822 * vfsmount lock must be held for write
823 */
824static void __touch_mnt_namespace(struct mnt_namespace *ns)
825{
826 if (ns && ns->event != event) {
827 ns->event = event;
828 wake_up_interruptible(&ns->poll);
829 }
830}
831
832/*
833 * vfsmount lock must be held for write
834 */
835static struct mountpoint *unhash_mnt(struct mount *mnt)
836{
837 struct mountpoint *mp;
838 mnt->mnt_parent = mnt;
839 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
840 list_del_init(&mnt->mnt_child);
841 hlist_del_init_rcu(&mnt->mnt_hash);
842 hlist_del_init(&mnt->mnt_mp_list);
843 mp = mnt->mnt_mp;
844 mnt->mnt_mp = NULL;
845 return mp;
846}
847
848/*
849 * vfsmount lock must be held for write
850 */
851static void umount_mnt(struct mount *mnt)
852{
853 put_mountpoint(unhash_mnt(mnt));
854}
855
856/*
857 * vfsmount lock must be held for write
858 */
859void mnt_set_mountpoint(struct mount *mnt,
860 struct mountpoint *mp,
861 struct mount *child_mnt)
862{
863 mp->m_count++;
864 mnt_add_count(mnt, 1); /* essentially, that's mntget */
865 child_mnt->mnt_mountpoint = mp->m_dentry;
866 child_mnt->mnt_parent = mnt;
867 child_mnt->mnt_mp = mp;
868 hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list);
869}
870
871static void __attach_mnt(struct mount *mnt, struct mount *parent)
872{
873 hlist_add_head_rcu(&mnt->mnt_hash,
874 m_hash(&parent->mnt, mnt->mnt_mountpoint));
875 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
876}
877
878/*
879 * vfsmount lock must be held for write
880 */
881static void attach_mnt(struct mount *mnt,
882 struct mount *parent,
883 struct mountpoint *mp)
884{
885 mnt_set_mountpoint(parent, mp, mnt);
886 __attach_mnt(mnt, parent);
887}
888
889void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp, struct mount *mnt)
890{
891 struct mountpoint *old_mp = mnt->mnt_mp;
892 struct mount *old_parent = mnt->mnt_parent;
893
894 list_del_init(&mnt->mnt_child);
895 hlist_del_init(&mnt->mnt_mp_list);
896 hlist_del_init_rcu(&mnt->mnt_hash);
897
898 attach_mnt(mnt, parent, mp);
899
900 put_mountpoint(old_mp);
901 mnt_add_count(old_parent, -1);
902}
903
904/*
905 * vfsmount lock must be held for write
906 */
907static void commit_tree(struct mount *mnt)
908{
909 struct mount *parent = mnt->mnt_parent;
910 struct mount *m;
911 LIST_HEAD(head);
912 struct mnt_namespace *n = parent->mnt_ns;
913
914 BUG_ON(parent == mnt);
915
916 list_add_tail(&head, &mnt->mnt_list);
917 list_for_each_entry(m, &head, mnt_list)
918 m->mnt_ns = n;
919
920 list_splice(&head, n->list.prev);
921
922 n->mounts += n->pending_mounts;
923 n->pending_mounts = 0;
924
925 __attach_mnt(mnt, parent);
926 touch_mnt_namespace(n);
927}
928
929static struct mount *next_mnt(struct mount *p, struct mount *root)
930{
931 struct list_head *next = p->mnt_mounts.next;
932 if (next == &p->mnt_mounts) {
933 while (1) {
934 if (p == root)
935 return NULL;
936 next = p->mnt_child.next;
937 if (next != &p->mnt_parent->mnt_mounts)
938 break;
939 p = p->mnt_parent;
940 }
941 }
942 return list_entry(next, struct mount, mnt_child);
943}
944
945static struct mount *skip_mnt_tree(struct mount *p)
946{
947 struct list_head *prev = p->mnt_mounts.prev;
948 while (prev != &p->mnt_mounts) {
949 p = list_entry(prev, struct mount, mnt_child);
950 prev = p->mnt_mounts.prev;
951 }
952 return p;
953}
954
955/**
956 * vfs_create_mount - Create a mount for a configured superblock
957 * @fc: The configuration context with the superblock attached
958 *
959 * Create a mount to an already configured superblock. If necessary, the
960 * caller should invoke vfs_get_tree() before calling this.
961 *
962 * Note that this does not attach the mount to anything.
963 */
964struct vfsmount *vfs_create_mount(struct fs_context *fc)
965{
966 struct mount *mnt;
967
968 if (!fc->root)
969 return ERR_PTR(-EINVAL);
970
971 mnt = alloc_vfsmnt(fc->source ?: "none");
972 if (!mnt)
973 return ERR_PTR(-ENOMEM);
974
975 if (fc->sb_flags & SB_KERNMOUNT)
976 mnt->mnt.mnt_flags = MNT_INTERNAL;
977
978 atomic_inc(&fc->root->d_sb->s_active);
979 mnt->mnt.mnt_sb = fc->root->d_sb;
980 mnt->mnt.mnt_root = dget(fc->root);
981 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
982 mnt->mnt_parent = mnt;
983
984 lock_mount_hash();
985 list_add_tail(&mnt->mnt_instance, &mnt->mnt.mnt_sb->s_mounts);
986 unlock_mount_hash();
987 return &mnt->mnt;
988}
989EXPORT_SYMBOL(vfs_create_mount);
990
991struct vfsmount *fc_mount(struct fs_context *fc)
992{
993 int err = vfs_get_tree(fc);
994 if (!err) {
995 up_write(&fc->root->d_sb->s_umount);
996 return vfs_create_mount(fc);
997 }
998 return ERR_PTR(err);
999}
1000EXPORT_SYMBOL(fc_mount);
1001
1002struct vfsmount *vfs_kern_mount(struct file_system_type *type,
1003 int flags, const char *name,
1004 void *data)
1005{
1006 struct fs_context *fc;
1007 struct vfsmount *mnt;
1008 int ret = 0;
1009
1010 if (!type)
1011 return ERR_PTR(-EINVAL);
1012
1013 fc = fs_context_for_mount(type, flags);
1014 if (IS_ERR(fc))
1015 return ERR_CAST(fc);
1016
1017 if (name)
1018 ret = vfs_parse_fs_string(fc, "source",
1019 name, strlen(name));
1020 if (!ret)
1021 ret = parse_monolithic_mount_data(fc, data);
1022 if (!ret)
1023 mnt = fc_mount(fc);
1024 else
1025 mnt = ERR_PTR(ret);
1026
1027 put_fs_context(fc);
1028 return mnt;
1029}
1030EXPORT_SYMBOL_GPL(vfs_kern_mount);
1031
1032struct vfsmount *
1033vfs_submount(const struct dentry *mountpoint, struct file_system_type *type,
1034 const char *name, void *data)
1035{
1036 /* Until it is worked out how to pass the user namespace
1037 * through from the parent mount to the submount don't support
1038 * unprivileged mounts with submounts.
1039 */
1040 if (mountpoint->d_sb->s_user_ns != &init_user_ns)
1041 return ERR_PTR(-EPERM);
1042
1043 return vfs_kern_mount(type, SB_SUBMOUNT, name, data);
1044}
1045EXPORT_SYMBOL_GPL(vfs_submount);
1046
1047static struct mount *clone_mnt(struct mount *old, struct dentry *root,
1048 int flag)
1049{
1050 struct super_block *sb = old->mnt.mnt_sb;
1051 struct mount *mnt;
1052 int err;
1053
1054 mnt = alloc_vfsmnt(old->mnt_devname);
1055 if (!mnt)
1056 return ERR_PTR(-ENOMEM);
1057
1058 if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
1059 mnt->mnt_group_id = 0; /* not a peer of original */
1060 else
1061 mnt->mnt_group_id = old->mnt_group_id;
1062
1063 if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
1064 err = mnt_alloc_group_id(mnt);
1065 if (err)
1066 goto out_free;
1067 }
1068
1069 mnt->mnt.mnt_flags = old->mnt.mnt_flags;
1070 mnt->mnt.mnt_flags &= ~(MNT_WRITE_HOLD|MNT_MARKED|MNT_INTERNAL);
1071
1072 atomic_inc(&sb->s_active);
1073 mnt->mnt.mnt_userns = mnt_user_ns(&old->mnt);
1074 if (mnt->mnt.mnt_userns != &init_user_ns)
1075 mnt->mnt.mnt_userns = get_user_ns(mnt->mnt.mnt_userns);
1076 mnt->mnt.mnt_sb = sb;
1077 mnt->mnt.mnt_root = dget(root);
1078 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
1079 mnt->mnt_parent = mnt;
1080 lock_mount_hash();
1081 list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
1082 unlock_mount_hash();
1083
1084 if ((flag & CL_SLAVE) ||
1085 ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
1086 list_add(&mnt->mnt_slave, &old->mnt_slave_list);
1087 mnt->mnt_master = old;
1088 CLEAR_MNT_SHARED(mnt);
1089 } else if (!(flag & CL_PRIVATE)) {
1090 if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
1091 list_add(&mnt->mnt_share, &old->mnt_share);
1092 if (IS_MNT_SLAVE(old))
1093 list_add(&mnt->mnt_slave, &old->mnt_slave);
1094 mnt->mnt_master = old->mnt_master;
1095 } else {
1096 CLEAR_MNT_SHARED(mnt);
1097 }
1098 if (flag & CL_MAKE_SHARED)
1099 set_mnt_shared(mnt);
1100
1101 /* stick the duplicate mount on the same expiry list
1102 * as the original if that was on one */
1103 if (flag & CL_EXPIRE) {
1104 if (!list_empty(&old->mnt_expire))
1105 list_add(&mnt->mnt_expire, &old->mnt_expire);
1106 }
1107
1108 return mnt;
1109
1110 out_free:
1111 mnt_free_id(mnt);
1112 free_vfsmnt(mnt);
1113 return ERR_PTR(err);
1114}
1115
1116static void cleanup_mnt(struct mount *mnt)
1117{
1118 struct hlist_node *p;
1119 struct mount *m;
1120 /*
1121 * The warning here probably indicates that somebody messed
1122 * up a mnt_want/drop_write() pair. If this happens, the
1123 * filesystem was probably unable to make r/w->r/o transitions.
1124 * The locking used to deal with mnt_count decrement provides barriers,
1125 * so mnt_get_writers() below is safe.
1126 */
1127 WARN_ON(mnt_get_writers(mnt));
1128 if (unlikely(mnt->mnt_pins.first))
1129 mnt_pin_kill(mnt);
1130 hlist_for_each_entry_safe(m, p, &mnt->mnt_stuck_children, mnt_umount) {
1131 hlist_del(&m->mnt_umount);
1132 mntput(&m->mnt);
1133 }
1134 fsnotify_vfsmount_delete(&mnt->mnt);
1135 dput(mnt->mnt.mnt_root);
1136 deactivate_super(mnt->mnt.mnt_sb);
1137 mnt_free_id(mnt);
1138 call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt);
1139}
1140
1141static void __cleanup_mnt(struct rcu_head *head)
1142{
1143 cleanup_mnt(container_of(head, struct mount, mnt_rcu));
1144}
1145
1146static LLIST_HEAD(delayed_mntput_list);
1147static void delayed_mntput(struct work_struct *unused)
1148{
1149 struct llist_node *node = llist_del_all(&delayed_mntput_list);
1150 struct mount *m, *t;
1151
1152 llist_for_each_entry_safe(m, t, node, mnt_llist)
1153 cleanup_mnt(m);
1154}
1155static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput);
1156
1157static void mntput_no_expire(struct mount *mnt)
1158{
1159 LIST_HEAD(list);
1160 int count;
1161
1162 rcu_read_lock();
1163 if (likely(READ_ONCE(mnt->mnt_ns))) {
1164 /*
1165 * Since we don't do lock_mount_hash() here,
1166 * ->mnt_ns can change under us. However, if it's
1167 * non-NULL, then there's a reference that won't
1168 * be dropped until after an RCU delay done after
1169 * turning ->mnt_ns NULL. So if we observe it
1170 * non-NULL under rcu_read_lock(), the reference
1171 * we are dropping is not the final one.
1172 */
1173 mnt_add_count(mnt, -1);
1174 rcu_read_unlock();
1175 return;
1176 }
1177 lock_mount_hash();
1178 /*
1179 * make sure that if __legitimize_mnt() has not seen us grab
1180 * mount_lock, we'll see their refcount increment here.
1181 */
1182 smp_mb();
1183 mnt_add_count(mnt, -1);
1184 count = mnt_get_count(mnt);
1185 if (count != 0) {
1186 WARN_ON(count < 0);
1187 rcu_read_unlock();
1188 unlock_mount_hash();
1189 return;
1190 }
1191 if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) {
1192 rcu_read_unlock();
1193 unlock_mount_hash();
1194 return;
1195 }
1196 mnt->mnt.mnt_flags |= MNT_DOOMED;
1197 rcu_read_unlock();
1198
1199 list_del(&mnt->mnt_instance);
1200
1201 if (unlikely(!list_empty(&mnt->mnt_mounts))) {
1202 struct mount *p, *tmp;
1203 list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) {
1204 __put_mountpoint(unhash_mnt(p), &list);
1205 hlist_add_head(&p->mnt_umount, &mnt->mnt_stuck_children);
1206 }
1207 }
1208 unlock_mount_hash();
1209 shrink_dentry_list(&list);
1210
1211 if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) {
1212 struct task_struct *task = current;
1213 if (likely(!(task->flags & PF_KTHREAD))) {
1214 init_task_work(&mnt->mnt_rcu, __cleanup_mnt);
1215 if (!task_work_add(task, &mnt->mnt_rcu, TWA_RESUME))
1216 return;
1217 }
1218 if (llist_add(&mnt->mnt_llist, &delayed_mntput_list))
1219 schedule_delayed_work(&delayed_mntput_work, 1);
1220 return;
1221 }
1222 cleanup_mnt(mnt);
1223}
1224
1225void mntput(struct vfsmount *mnt)
1226{
1227 if (mnt) {
1228 struct mount *m = real_mount(mnt);
1229 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
1230 if (unlikely(m->mnt_expiry_mark))
1231 m->mnt_expiry_mark = 0;
1232 mntput_no_expire(m);
1233 }
1234}
1235EXPORT_SYMBOL(mntput);
1236
1237struct vfsmount *mntget(struct vfsmount *mnt)
1238{
1239 if (mnt)
1240 mnt_add_count(real_mount(mnt), 1);
1241 return mnt;
1242}
1243EXPORT_SYMBOL(mntget);
1244
1245/**
1246 * path_is_mountpoint() - Check if path is a mount in the current namespace.
1247 * @path: path to check
1248 *
1249 * d_mountpoint() can only be used reliably to establish if a dentry is
1250 * not mounted in any namespace and that common case is handled inline.
1251 * d_mountpoint() isn't aware of the possibility there may be multiple
1252 * mounts using a given dentry in a different namespace. This function
1253 * checks if the passed in path is a mountpoint rather than the dentry
1254 * alone.
1255 */
1256bool path_is_mountpoint(const struct path *path)
1257{
1258 unsigned seq;
1259 bool res;
1260
1261 if (!d_mountpoint(path->dentry))
1262 return false;
1263
1264 rcu_read_lock();
1265 do {
1266 seq = read_seqbegin(&mount_lock);
1267 res = __path_is_mountpoint(path);
1268 } while (read_seqretry(&mount_lock, seq));
1269 rcu_read_unlock();
1270
1271 return res;
1272}
1273EXPORT_SYMBOL(path_is_mountpoint);
1274
1275struct vfsmount *mnt_clone_internal(const struct path *path)
1276{
1277 struct mount *p;
1278 p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE);
1279 if (IS_ERR(p))
1280 return ERR_CAST(p);
1281 p->mnt.mnt_flags |= MNT_INTERNAL;
1282 return &p->mnt;
1283}
1284
1285#ifdef CONFIG_PROC_FS
1286static struct mount *mnt_list_next(struct mnt_namespace *ns,
1287 struct list_head *p)
1288{
1289 struct mount *mnt, *ret = NULL;
1290
1291 lock_ns_list(ns);
1292 list_for_each_continue(p, &ns->list) {
1293 mnt = list_entry(p, typeof(*mnt), mnt_list);
1294 if (!mnt_is_cursor(mnt)) {
1295 ret = mnt;
1296 break;
1297 }
1298 }
1299 unlock_ns_list(ns);
1300
1301 return ret;
1302}
1303
1304/* iterator; we want it to have access to namespace_sem, thus here... */
1305static void *m_start(struct seq_file *m, loff_t *pos)
1306{
1307 struct proc_mounts *p = m->private;
1308 struct list_head *prev;
1309
1310 down_read(&namespace_sem);
1311 if (!*pos) {
1312 prev = &p->ns->list;
1313 } else {
1314 prev = &p->cursor.mnt_list;
1315
1316 /* Read after we'd reached the end? */
1317 if (list_empty(prev))
1318 return NULL;
1319 }
1320
1321 return mnt_list_next(p->ns, prev);
1322}
1323
1324static void *m_next(struct seq_file *m, void *v, loff_t *pos)
1325{
1326 struct proc_mounts *p = m->private;
1327 struct mount *mnt = v;
1328
1329 ++*pos;
1330 return mnt_list_next(p->ns, &mnt->mnt_list);
1331}
1332
1333static void m_stop(struct seq_file *m, void *v)
1334{
1335 struct proc_mounts *p = m->private;
1336 struct mount *mnt = v;
1337
1338 lock_ns_list(p->ns);
1339 if (mnt)
1340 list_move_tail(&p->cursor.mnt_list, &mnt->mnt_list);
1341 else
1342 list_del_init(&p->cursor.mnt_list);
1343 unlock_ns_list(p->ns);
1344 up_read(&namespace_sem);
1345}
1346
1347static int m_show(struct seq_file *m, void *v)
1348{
1349 struct proc_mounts *p = m->private;
1350 struct mount *r = v;
1351 return p->show(m, &r->mnt);
1352}
1353
1354const struct seq_operations mounts_op = {
1355 .start = m_start,
1356 .next = m_next,
1357 .stop = m_stop,
1358 .show = m_show,
1359};
1360
1361void mnt_cursor_del(struct mnt_namespace *ns, struct mount *cursor)
1362{
1363 down_read(&namespace_sem);
1364 lock_ns_list(ns);
1365 list_del(&cursor->mnt_list);
1366 unlock_ns_list(ns);
1367 up_read(&namespace_sem);
1368}
1369#endif /* CONFIG_PROC_FS */
1370
1371/**
1372 * may_umount_tree - check if a mount tree is busy
1373 * @m: root of mount tree
1374 *
1375 * This is called to check if a tree of mounts has any
1376 * open files, pwds, chroots or sub mounts that are
1377 * busy.
1378 */
1379int may_umount_tree(struct vfsmount *m)
1380{
1381 struct mount *mnt = real_mount(m);
1382 int actual_refs = 0;
1383 int minimum_refs = 0;
1384 struct mount *p;
1385 BUG_ON(!m);
1386
1387 /* write lock needed for mnt_get_count */
1388 lock_mount_hash();
1389 for (p = mnt; p; p = next_mnt(p, mnt)) {
1390 actual_refs += mnt_get_count(p);
1391 minimum_refs += 2;
1392 }
1393 unlock_mount_hash();
1394
1395 if (actual_refs > minimum_refs)
1396 return 0;
1397
1398 return 1;
1399}
1400
1401EXPORT_SYMBOL(may_umount_tree);
1402
1403/**
1404 * may_umount - check if a mount point is busy
1405 * @mnt: root of mount
1406 *
1407 * This is called to check if a mount point has any
1408 * open files, pwds, chroots or sub mounts. If the
1409 * mount has sub mounts this will return busy
1410 * regardless of whether the sub mounts are busy.
1411 *
1412 * Doesn't take quota and stuff into account. IOW, in some cases it will
1413 * give false negatives. The main reason why it's here is that we need
1414 * a non-destructive way to look for easily umountable filesystems.
1415 */
1416int may_umount(struct vfsmount *mnt)
1417{
1418 int ret = 1;
1419 down_read(&namespace_sem);
1420 lock_mount_hash();
1421 if (propagate_mount_busy(real_mount(mnt), 2))
1422 ret = 0;
1423 unlock_mount_hash();
1424 up_read(&namespace_sem);
1425 return ret;
1426}
1427
1428EXPORT_SYMBOL(may_umount);
1429
1430static void namespace_unlock(void)
1431{
1432 struct hlist_head head;
1433 struct hlist_node *p;
1434 struct mount *m;
1435 LIST_HEAD(list);
1436
1437 hlist_move_list(&unmounted, &head);
1438 list_splice_init(&ex_mountpoints, &list);
1439
1440 up_write(&namespace_sem);
1441
1442 shrink_dentry_list(&list);
1443
1444 if (likely(hlist_empty(&head)))
1445 return;
1446
1447 synchronize_rcu_expedited();
1448
1449 hlist_for_each_entry_safe(m, p, &head, mnt_umount) {
1450 hlist_del(&m->mnt_umount);
1451 mntput(&m->mnt);
1452 }
1453}
1454
1455static inline void namespace_lock(void)
1456{
1457 down_write(&namespace_sem);
1458}
1459
1460enum umount_tree_flags {
1461 UMOUNT_SYNC = 1,
1462 UMOUNT_PROPAGATE = 2,
1463 UMOUNT_CONNECTED = 4,
1464};
1465
1466static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how)
1467{
1468 /* Leaving mounts connected is only valid for lazy umounts */
1469 if (how & UMOUNT_SYNC)
1470 return true;
1471
1472 /* A mount without a parent has nothing to be connected to */
1473 if (!mnt_has_parent(mnt))
1474 return true;
1475
1476 /* Because the reference counting rules change when mounts are
1477 * unmounted and connected, umounted mounts may not be
1478 * connected to mounted mounts.
1479 */
1480 if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT))
1481 return true;
1482
1483 /* Has it been requested that the mount remain connected? */
1484 if (how & UMOUNT_CONNECTED)
1485 return false;
1486
1487 /* Is the mount locked such that it needs to remain connected? */
1488 if (IS_MNT_LOCKED(mnt))
1489 return false;
1490
1491 /* By default disconnect the mount */
1492 return true;
1493}
1494
1495/*
1496 * mount_lock must be held
1497 * namespace_sem must be held for write
1498 */
1499static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
1500{
1501 LIST_HEAD(tmp_list);
1502 struct mount *p;
1503
1504 if (how & UMOUNT_PROPAGATE)
1505 propagate_mount_unlock(mnt);
1506
1507 /* Gather the mounts to umount */
1508 for (p = mnt; p; p = next_mnt(p, mnt)) {
1509 p->mnt.mnt_flags |= MNT_UMOUNT;
1510 list_move(&p->mnt_list, &tmp_list);
1511 }
1512
1513 /* Hide the mounts from mnt_mounts */
1514 list_for_each_entry(p, &tmp_list, mnt_list) {
1515 list_del_init(&p->mnt_child);
1516 }
1517
1518 /* Add propogated mounts to the tmp_list */
1519 if (how & UMOUNT_PROPAGATE)
1520 propagate_umount(&tmp_list);
1521
1522 while (!list_empty(&tmp_list)) {
1523 struct mnt_namespace *ns;
1524 bool disconnect;
1525 p = list_first_entry(&tmp_list, struct mount, mnt_list);
1526 list_del_init(&p->mnt_expire);
1527 list_del_init(&p->mnt_list);
1528 ns = p->mnt_ns;
1529 if (ns) {
1530 ns->mounts--;
1531 __touch_mnt_namespace(ns);
1532 }
1533 p->mnt_ns = NULL;
1534 if (how & UMOUNT_SYNC)
1535 p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
1536
1537 disconnect = disconnect_mount(p, how);
1538 if (mnt_has_parent(p)) {
1539 mnt_add_count(p->mnt_parent, -1);
1540 if (!disconnect) {
1541 /* Don't forget about p */
1542 list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts);
1543 } else {
1544 umount_mnt(p);
1545 }
1546 }
1547 change_mnt_propagation(p, MS_PRIVATE);
1548 if (disconnect)
1549 hlist_add_head(&p->mnt_umount, &unmounted);
1550 }
1551}
1552
1553static void shrink_submounts(struct mount *mnt);
1554
1555static int do_umount_root(struct super_block *sb)
1556{
1557 int ret = 0;
1558
1559 down_write(&sb->s_umount);
1560 if (!sb_rdonly(sb)) {
1561 struct fs_context *fc;
1562
1563 fc = fs_context_for_reconfigure(sb->s_root, SB_RDONLY,
1564 SB_RDONLY);
1565 if (IS_ERR(fc)) {
1566 ret = PTR_ERR(fc);
1567 } else {
1568 ret = parse_monolithic_mount_data(fc, NULL);
1569 if (!ret)
1570 ret = reconfigure_super(fc);
1571 put_fs_context(fc);
1572 }
1573 }
1574 up_write(&sb->s_umount);
1575 return ret;
1576}
1577
1578static int do_umount(struct mount *mnt, int flags)
1579{
1580 struct super_block *sb = mnt->mnt.mnt_sb;
1581 int retval;
1582
1583 retval = security_sb_umount(&mnt->mnt, flags);
1584 if (retval)
1585 return retval;
1586
1587 /*
1588 * Allow userspace to request a mountpoint be expired rather than
1589 * unmounting unconditionally. Unmount only happens if:
1590 * (1) the mark is already set (the mark is cleared by mntput())
1591 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1592 */
1593 if (flags & MNT_EXPIRE) {
1594 if (&mnt->mnt == current->fs->root.mnt ||
1595 flags & (MNT_FORCE | MNT_DETACH))
1596 return -EINVAL;
1597
1598 /*
1599 * probably don't strictly need the lock here if we examined
1600 * all race cases, but it's a slowpath.
1601 */
1602 lock_mount_hash();
1603 if (mnt_get_count(mnt) != 2) {
1604 unlock_mount_hash();
1605 return -EBUSY;
1606 }
1607 unlock_mount_hash();
1608
1609 if (!xchg(&mnt->mnt_expiry_mark, 1))
1610 return -EAGAIN;
1611 }
1612
1613 /*
1614 * If we may have to abort operations to get out of this
1615 * mount, and they will themselves hold resources we must
1616 * allow the fs to do things. In the Unix tradition of
1617 * 'Gee thats tricky lets do it in userspace' the umount_begin
1618 * might fail to complete on the first run through as other tasks
1619 * must return, and the like. Thats for the mount program to worry
1620 * about for the moment.
1621 */
1622
1623 if (flags & MNT_FORCE && sb->s_op->umount_begin) {
1624 sb->s_op->umount_begin(sb);
1625 }
1626
1627 /*
1628 * No sense to grab the lock for this test, but test itself looks
1629 * somewhat bogus. Suggestions for better replacement?
1630 * Ho-hum... In principle, we might treat that as umount + switch
1631 * to rootfs. GC would eventually take care of the old vfsmount.
1632 * Actually it makes sense, especially if rootfs would contain a
1633 * /reboot - static binary that would close all descriptors and
1634 * call reboot(9). Then init(8) could umount root and exec /reboot.
1635 */
1636 if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
1637 /*
1638 * Special case for "unmounting" root ...
1639 * we just try to remount it readonly.
1640 */
1641 if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN))
1642 return -EPERM;
1643 return do_umount_root(sb);
1644 }
1645
1646 namespace_lock();
1647 lock_mount_hash();
1648
1649 /* Recheck MNT_LOCKED with the locks held */
1650 retval = -EINVAL;
1651 if (mnt->mnt.mnt_flags & MNT_LOCKED)
1652 goto out;
1653
1654 event++;
1655 if (flags & MNT_DETACH) {
1656 if (!list_empty(&mnt->mnt_list))
1657 umount_tree(mnt, UMOUNT_PROPAGATE);
1658 retval = 0;
1659 } else {
1660 shrink_submounts(mnt);
1661 retval = -EBUSY;
1662 if (!propagate_mount_busy(mnt, 2)) {
1663 if (!list_empty(&mnt->mnt_list))
1664 umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
1665 retval = 0;
1666 }
1667 }
1668out:
1669 unlock_mount_hash();
1670 namespace_unlock();
1671 return retval;
1672}
1673
1674/*
1675 * __detach_mounts - lazily unmount all mounts on the specified dentry
1676 *
1677 * During unlink, rmdir, and d_drop it is possible to loose the path
1678 * to an existing mountpoint, and wind up leaking the mount.
1679 * detach_mounts allows lazily unmounting those mounts instead of
1680 * leaking them.
1681 *
1682 * The caller may hold dentry->d_inode->i_mutex.
1683 */
1684void __detach_mounts(struct dentry *dentry)
1685{
1686 struct mountpoint *mp;
1687 struct mount *mnt;
1688
1689 namespace_lock();
1690 lock_mount_hash();
1691 mp = lookup_mountpoint(dentry);
1692 if (!mp)
1693 goto out_unlock;
1694
1695 event++;
1696 while (!hlist_empty(&mp->m_list)) {
1697 mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list);
1698 if (mnt->mnt.mnt_flags & MNT_UMOUNT) {
1699 umount_mnt(mnt);
1700 hlist_add_head(&mnt->mnt_umount, &unmounted);
1701 }
1702 else umount_tree(mnt, UMOUNT_CONNECTED);
1703 }
1704 put_mountpoint(mp);
1705out_unlock:
1706 unlock_mount_hash();
1707 namespace_unlock();
1708}
1709
1710/*
1711 * Is the caller allowed to modify his namespace?
1712 */
1713static inline bool may_mount(void)
1714{
1715 return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
1716}
1717
1718#ifdef CONFIG_MANDATORY_FILE_LOCKING
1719static bool may_mandlock(void)
1720{
1721 pr_warn_once("======================================================\n"
1722 "WARNING: the mand mount option is being deprecated and\n"
1723 " will be removed in v5.15!\n"
1724 "======================================================\n");
1725 return capable(CAP_SYS_ADMIN);
1726}
1727#else
1728static inline bool may_mandlock(void)
1729{
1730 pr_warn("VFS: \"mand\" mount option not supported");
1731 return false;
1732}
1733#endif
1734
1735static int can_umount(const struct path *path, int flags)
1736{
1737 struct mount *mnt = real_mount(path->mnt);
1738
1739 if (!may_mount())
1740 return -EPERM;
1741 if (path->dentry != path->mnt->mnt_root)
1742 return -EINVAL;
1743 if (!check_mnt(mnt))
1744 return -EINVAL;
1745 if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */
1746 return -EINVAL;
1747 if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))
1748 return -EPERM;
1749 return 0;
1750}
1751
1752// caller is responsible for flags being sane
1753int path_umount(struct path *path, int flags)
1754{
1755 struct mount *mnt = real_mount(path->mnt);
1756 int ret;
1757
1758 ret = can_umount(path, flags);
1759 if (!ret)
1760 ret = do_umount(mnt, flags);
1761
1762 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1763 dput(path->dentry);
1764 mntput_no_expire(mnt);
1765 return ret;
1766}
1767
1768static int ksys_umount(char __user *name, int flags)
1769{
1770 int lookup_flags = LOOKUP_MOUNTPOINT;
1771 struct path path;
1772 int ret;
1773
1774 // basic validity checks done first
1775 if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
1776 return -EINVAL;
1777
1778 if (!(flags & UMOUNT_NOFOLLOW))
1779 lookup_flags |= LOOKUP_FOLLOW;
1780 ret = user_path_at(AT_FDCWD, name, lookup_flags, &path);
1781 if (ret)
1782 return ret;
1783 return path_umount(&path, flags);
1784}
1785
1786SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1787{
1788 return ksys_umount(name, flags);
1789}
1790
1791#ifdef __ARCH_WANT_SYS_OLDUMOUNT
1792
1793/*
1794 * The 2.0 compatible umount. No flags.
1795 */
1796SYSCALL_DEFINE1(oldumount, char __user *, name)
1797{
1798 return ksys_umount(name, 0);
1799}
1800
1801#endif
1802
1803static bool is_mnt_ns_file(struct dentry *dentry)
1804{
1805 /* Is this a proxy for a mount namespace? */
1806 return dentry->d_op == &ns_dentry_operations &&
1807 dentry->d_fsdata == &mntns_operations;
1808}
1809
1810static struct mnt_namespace *to_mnt_ns(struct ns_common *ns)
1811{
1812 return container_of(ns, struct mnt_namespace, ns);
1813}
1814
1815struct ns_common *from_mnt_ns(struct mnt_namespace *mnt)
1816{
1817 return &mnt->ns;
1818}
1819
1820static bool mnt_ns_loop(struct dentry *dentry)
1821{
1822 /* Could bind mounting the mount namespace inode cause a
1823 * mount namespace loop?
1824 */
1825 struct mnt_namespace *mnt_ns;
1826 if (!is_mnt_ns_file(dentry))
1827 return false;
1828
1829 mnt_ns = to_mnt_ns(get_proc_ns(dentry->d_inode));
1830 return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
1831}
1832
1833struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
1834 int flag)
1835{
1836 struct mount *res, *p, *q, *r, *parent;
1837
1838 if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt))
1839 return ERR_PTR(-EINVAL);
1840
1841 if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
1842 return ERR_PTR(-EINVAL);
1843
1844 res = q = clone_mnt(mnt, dentry, flag);
1845 if (IS_ERR(q))
1846 return q;
1847
1848 q->mnt_mountpoint = mnt->mnt_mountpoint;
1849
1850 p = mnt;
1851 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
1852 struct mount *s;
1853 if (!is_subdir(r->mnt_mountpoint, dentry))
1854 continue;
1855
1856 for (s = r; s; s = next_mnt(s, r)) {
1857 if (!(flag & CL_COPY_UNBINDABLE) &&
1858 IS_MNT_UNBINDABLE(s)) {
1859 if (s->mnt.mnt_flags & MNT_LOCKED) {
1860 /* Both unbindable and locked. */
1861 q = ERR_PTR(-EPERM);
1862 goto out;
1863 } else {
1864 s = skip_mnt_tree(s);
1865 continue;
1866 }
1867 }
1868 if (!(flag & CL_COPY_MNT_NS_FILE) &&
1869 is_mnt_ns_file(s->mnt.mnt_root)) {
1870 s = skip_mnt_tree(s);
1871 continue;
1872 }
1873 while (p != s->mnt_parent) {
1874 p = p->mnt_parent;
1875 q = q->mnt_parent;
1876 }
1877 p = s;
1878 parent = q;
1879 q = clone_mnt(p, p->mnt.mnt_root, flag);
1880 if (IS_ERR(q))
1881 goto out;
1882 lock_mount_hash();
1883 list_add_tail(&q->mnt_list, &res->mnt_list);
1884 attach_mnt(q, parent, p->mnt_mp);
1885 unlock_mount_hash();
1886 }
1887 }
1888 return res;
1889out:
1890 if (res) {
1891 lock_mount_hash();
1892 umount_tree(res, UMOUNT_SYNC);
1893 unlock_mount_hash();
1894 }
1895 return q;
1896}
1897
1898/* Caller should check returned pointer for errors */
1899
1900struct vfsmount *collect_mounts(const struct path *path)
1901{
1902 struct mount *tree;
1903 namespace_lock();
1904 if (!check_mnt(real_mount(path->mnt)))
1905 tree = ERR_PTR(-EINVAL);
1906 else
1907 tree = copy_tree(real_mount(path->mnt), path->dentry,
1908 CL_COPY_ALL | CL_PRIVATE);
1909 namespace_unlock();
1910 if (IS_ERR(tree))
1911 return ERR_CAST(tree);
1912 return &tree->mnt;
1913}
1914
1915static void free_mnt_ns(struct mnt_namespace *);
1916static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *, bool);
1917
1918void dissolve_on_fput(struct vfsmount *mnt)
1919{
1920 struct mnt_namespace *ns;
1921 namespace_lock();
1922 lock_mount_hash();
1923 ns = real_mount(mnt)->mnt_ns;
1924 if (ns) {
1925 if (is_anon_ns(ns))
1926 umount_tree(real_mount(mnt), UMOUNT_CONNECTED);
1927 else
1928 ns = NULL;
1929 }
1930 unlock_mount_hash();
1931 namespace_unlock();
1932 if (ns)
1933 free_mnt_ns(ns);
1934}
1935
1936void drop_collected_mounts(struct vfsmount *mnt)
1937{
1938 namespace_lock();
1939 lock_mount_hash();
1940 umount_tree(real_mount(mnt), 0);
1941 unlock_mount_hash();
1942 namespace_unlock();
1943}
1944
1945static bool has_locked_children(struct mount *mnt, struct dentry *dentry)
1946{
1947 struct mount *child;
1948
1949 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
1950 if (!is_subdir(child->mnt_mountpoint, dentry))
1951 continue;
1952
1953 if (child->mnt.mnt_flags & MNT_LOCKED)
1954 return true;
1955 }
1956 return false;
1957}
1958
1959/**
1960 * clone_private_mount - create a private clone of a path
1961 * @path: path to clone
1962 *
1963 * This creates a new vfsmount, which will be the clone of @path. The new mount
1964 * will not be attached anywhere in the namespace and will be private (i.e.
1965 * changes to the originating mount won't be propagated into this).
1966 *
1967 * Release with mntput().
1968 */
1969struct vfsmount *clone_private_mount(const struct path *path)
1970{
1971 struct mount *old_mnt = real_mount(path->mnt);
1972 struct mount *new_mnt;
1973
1974 down_read(&namespace_sem);
1975 if (IS_MNT_UNBINDABLE(old_mnt))
1976 goto invalid;
1977
1978 if (!check_mnt(old_mnt))
1979 goto invalid;
1980
1981 if (has_locked_children(old_mnt, path->dentry))
1982 goto invalid;
1983
1984 new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE);
1985 up_read(&namespace_sem);
1986
1987 if (IS_ERR(new_mnt))
1988 return ERR_CAST(new_mnt);
1989
1990 /* Longterm mount to be removed by kern_unmount*() */
1991 new_mnt->mnt_ns = MNT_NS_INTERNAL;
1992
1993 return &new_mnt->mnt;
1994
1995invalid:
1996 up_read(&namespace_sem);
1997 return ERR_PTR(-EINVAL);
1998}
1999EXPORT_SYMBOL_GPL(clone_private_mount);
2000
2001int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
2002 struct vfsmount *root)
2003{
2004 struct mount *mnt;
2005 int res = f(root, arg);
2006 if (res)
2007 return res;
2008 list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
2009 res = f(&mnt->mnt, arg);
2010 if (res)
2011 return res;
2012 }
2013 return 0;
2014}
2015
2016static void lock_mnt_tree(struct mount *mnt)
2017{
2018 struct mount *p;
2019
2020 for (p = mnt; p; p = next_mnt(p, mnt)) {
2021 int flags = p->mnt.mnt_flags;
2022 /* Don't allow unprivileged users to change mount flags */
2023 flags |= MNT_LOCK_ATIME;
2024
2025 if (flags & MNT_READONLY)
2026 flags |= MNT_LOCK_READONLY;
2027
2028 if (flags & MNT_NODEV)
2029 flags |= MNT_LOCK_NODEV;
2030
2031 if (flags & MNT_NOSUID)
2032 flags |= MNT_LOCK_NOSUID;
2033
2034 if (flags & MNT_NOEXEC)
2035 flags |= MNT_LOCK_NOEXEC;
2036 /* Don't allow unprivileged users to reveal what is under a mount */
2037 if (list_empty(&p->mnt_expire))
2038 flags |= MNT_LOCKED;
2039 p->mnt.mnt_flags = flags;
2040 }
2041}
2042
2043static void cleanup_group_ids(struct mount *mnt, struct mount *end)
2044{
2045 struct mount *p;
2046
2047 for (p = mnt; p != end; p = next_mnt(p, mnt)) {
2048 if (p->mnt_group_id && !IS_MNT_SHARED(p))
2049 mnt_release_group_id(p);
2050 }
2051}
2052
2053static int invent_group_ids(struct mount *mnt, bool recurse)
2054{
2055 struct mount *p;
2056
2057 for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
2058 if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
2059 int err = mnt_alloc_group_id(p);
2060 if (err) {
2061 cleanup_group_ids(mnt, p);
2062 return err;
2063 }
2064 }
2065 }
2066
2067 return 0;
2068}
2069
2070int count_mounts(struct mnt_namespace *ns, struct mount *mnt)
2071{
2072 unsigned int max = READ_ONCE(sysctl_mount_max);
2073 unsigned int mounts = 0, old, pending, sum;
2074 struct mount *p;
2075
2076 for (p = mnt; p; p = next_mnt(p, mnt))
2077 mounts++;
2078
2079 old = ns->mounts;
2080 pending = ns->pending_mounts;
2081 sum = old + pending;
2082 if ((old > sum) ||
2083 (pending > sum) ||
2084 (max < sum) ||
2085 (mounts > (max - sum)))
2086 return -ENOSPC;
2087
2088 ns->pending_mounts = pending + mounts;
2089 return 0;
2090}
2091
2092/*
2093 * @source_mnt : mount tree to be attached
2094 * @nd : place the mount tree @source_mnt is attached
2095 * @parent_nd : if non-null, detach the source_mnt from its parent and
2096 * store the parent mount and mountpoint dentry.
2097 * (done when source_mnt is moved)
2098 *
2099 * NOTE: in the table below explains the semantics when a source mount
2100 * of a given type is attached to a destination mount of a given type.
2101 * ---------------------------------------------------------------------------
2102 * | BIND MOUNT OPERATION |
2103 * |**************************************************************************
2104 * | source-->| shared | private | slave | unbindable |
2105 * | dest | | | | |
2106 * | | | | | | |
2107 * | v | | | | |
2108 * |**************************************************************************
2109 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
2110 * | | | | | |
2111 * |non-shared| shared (+) | private | slave (*) | invalid |
2112 * ***************************************************************************
2113 * A bind operation clones the source mount and mounts the clone on the
2114 * destination mount.
2115 *
2116 * (++) the cloned mount is propagated to all the mounts in the propagation
2117 * tree of the destination mount and the cloned mount is added to
2118 * the peer group of the source mount.
2119 * (+) the cloned mount is created under the destination mount and is marked
2120 * as shared. The cloned mount is added to the peer group of the source
2121 * mount.
2122 * (+++) the mount is propagated to all the mounts in the propagation tree
2123 * of the destination mount and the cloned mount is made slave
2124 * of the same master as that of the source mount. The cloned mount
2125 * is marked as 'shared and slave'.
2126 * (*) the cloned mount is made a slave of the same master as that of the
2127 * source mount.
2128 *
2129 * ---------------------------------------------------------------------------
2130 * | MOVE MOUNT OPERATION |
2131 * |**************************************************************************
2132 * | source-->| shared | private | slave | unbindable |
2133 * | dest | | | | |
2134 * | | | | | | |
2135 * | v | | | | |
2136 * |**************************************************************************
2137 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
2138 * | | | | | |
2139 * |non-shared| shared (+*) | private | slave (*) | unbindable |
2140 * ***************************************************************************
2141 *
2142 * (+) the mount is moved to the destination. And is then propagated to
2143 * all the mounts in the propagation tree of the destination mount.
2144 * (+*) the mount is moved to the destination.
2145 * (+++) the mount is moved to the destination and is then propagated to
2146 * all the mounts belonging to the destination mount's propagation tree.
2147 * the mount is marked as 'shared and slave'.
2148 * (*) the mount continues to be a slave at the new location.
2149 *
2150 * if the source mount is a tree, the operations explained above is
2151 * applied to each mount in the tree.
2152 * Must be called without spinlocks held, since this function can sleep
2153 * in allocations.
2154 */
2155static int attach_recursive_mnt(struct mount *source_mnt,
2156 struct mount *dest_mnt,
2157 struct mountpoint *dest_mp,
2158 bool moving)
2159{
2160 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2161 HLIST_HEAD(tree_list);
2162 struct mnt_namespace *ns = dest_mnt->mnt_ns;
2163 struct mountpoint *smp;
2164 struct mount *child, *p;
2165 struct hlist_node *n;
2166 int err;
2167
2168 /* Preallocate a mountpoint in case the new mounts need
2169 * to be tucked under other mounts.
2170 */
2171 smp = get_mountpoint(source_mnt->mnt.mnt_root);
2172 if (IS_ERR(smp))
2173 return PTR_ERR(smp);
2174
2175 /* Is there space to add these mounts to the mount namespace? */
2176 if (!moving) {
2177 err = count_mounts(ns, source_mnt);
2178 if (err)
2179 goto out;
2180 }
2181
2182 if (IS_MNT_SHARED(dest_mnt)) {
2183 err = invent_group_ids(source_mnt, true);
2184 if (err)
2185 goto out;
2186 err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
2187 lock_mount_hash();
2188 if (err)
2189 goto out_cleanup_ids;
2190 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
2191 set_mnt_shared(p);
2192 } else {
2193 lock_mount_hash();
2194 }
2195 if (moving) {
2196 unhash_mnt(source_mnt);
2197 attach_mnt(source_mnt, dest_mnt, dest_mp);
2198 touch_mnt_namespace(source_mnt->mnt_ns);
2199 } else {
2200 if (source_mnt->mnt_ns) {
2201 /* move from anon - the caller will destroy */
2202 list_del_init(&source_mnt->mnt_ns->list);
2203 }
2204 mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
2205 commit_tree(source_mnt);
2206 }
2207
2208 hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) {
2209 struct mount *q;
2210 hlist_del_init(&child->mnt_hash);
2211 q = __lookup_mnt(&child->mnt_parent->mnt,
2212 child->mnt_mountpoint);
2213 if (q)
2214 mnt_change_mountpoint(child, smp, q);
2215 /* Notice when we are propagating across user namespaces */
2216 if (child->mnt_parent->mnt_ns->user_ns != user_ns)
2217 lock_mnt_tree(child);
2218 child->mnt.mnt_flags &= ~MNT_LOCKED;
2219 commit_tree(child);
2220 }
2221 put_mountpoint(smp);
2222 unlock_mount_hash();
2223
2224 return 0;
2225
2226 out_cleanup_ids:
2227 while (!hlist_empty(&tree_list)) {
2228 child = hlist_entry(tree_list.first, struct mount, mnt_hash);
2229 child->mnt_parent->mnt_ns->pending_mounts = 0;
2230 umount_tree(child, UMOUNT_SYNC);
2231 }
2232 unlock_mount_hash();
2233 cleanup_group_ids(source_mnt, NULL);
2234 out:
2235 ns->pending_mounts = 0;
2236
2237 read_seqlock_excl(&mount_lock);
2238 put_mountpoint(smp);
2239 read_sequnlock_excl(&mount_lock);
2240
2241 return err;
2242}
2243
2244static struct mountpoint *lock_mount(struct path *path)
2245{
2246 struct vfsmount *mnt;
2247 struct dentry *dentry = path->dentry;
2248retry:
2249 inode_lock(dentry->d_inode);
2250 if (unlikely(cant_mount(dentry))) {
2251 inode_unlock(dentry->d_inode);
2252 return ERR_PTR(-ENOENT);
2253 }
2254 namespace_lock();
2255 mnt = lookup_mnt(path);
2256 if (likely(!mnt)) {
2257 struct mountpoint *mp = get_mountpoint(dentry);
2258 if (IS_ERR(mp)) {
2259 namespace_unlock();
2260 inode_unlock(dentry->d_inode);
2261 return mp;
2262 }
2263 return mp;
2264 }
2265 namespace_unlock();
2266 inode_unlock(path->dentry->d_inode);
2267 path_put(path);
2268 path->mnt = mnt;
2269 dentry = path->dentry = dget(mnt->mnt_root);
2270 goto retry;
2271}
2272
2273static void unlock_mount(struct mountpoint *where)
2274{
2275 struct dentry *dentry = where->m_dentry;
2276
2277 read_seqlock_excl(&mount_lock);
2278 put_mountpoint(where);
2279 read_sequnlock_excl(&mount_lock);
2280
2281 namespace_unlock();
2282 inode_unlock(dentry->d_inode);
2283}
2284
2285static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
2286{
2287 if (mnt->mnt.mnt_sb->s_flags & SB_NOUSER)
2288 return -EINVAL;
2289
2290 if (d_is_dir(mp->m_dentry) !=
2291 d_is_dir(mnt->mnt.mnt_root))
2292 return -ENOTDIR;
2293
2294 return attach_recursive_mnt(mnt, p, mp, false);
2295}
2296
2297/*
2298 * Sanity check the flags to change_mnt_propagation.
2299 */
2300
2301static int flags_to_propagation_type(int ms_flags)
2302{
2303 int type = ms_flags & ~(MS_REC | MS_SILENT);
2304
2305 /* Fail if any non-propagation flags are set */
2306 if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2307 return 0;
2308 /* Only one propagation flag should be set */
2309 if (!is_power_of_2(type))
2310 return 0;
2311 return type;
2312}
2313
2314/*
2315 * recursively change the type of the mountpoint.
2316 */
2317static int do_change_type(struct path *path, int ms_flags)
2318{
2319 struct mount *m;
2320 struct mount *mnt = real_mount(path->mnt);
2321 int recurse = ms_flags & MS_REC;
2322 int type;
2323 int err = 0;
2324
2325 if (path->dentry != path->mnt->mnt_root)
2326 return -EINVAL;
2327
2328 type = flags_to_propagation_type(ms_flags);
2329 if (!type)
2330 return -EINVAL;
2331
2332 namespace_lock();
2333 if (type == MS_SHARED) {
2334 err = invent_group_ids(mnt, recurse);
2335 if (err)
2336 goto out_unlock;
2337 }
2338
2339 lock_mount_hash();
2340 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
2341 change_mnt_propagation(m, type);
2342 unlock_mount_hash();
2343
2344 out_unlock:
2345 namespace_unlock();
2346 return err;
2347}
2348
2349static struct mount *__do_loopback(struct path *old_path, int recurse)
2350{
2351 struct mount *mnt = ERR_PTR(-EINVAL), *old = real_mount(old_path->mnt);
2352
2353 if (IS_MNT_UNBINDABLE(old))
2354 return mnt;
2355
2356 if (!check_mnt(old) && old_path->dentry->d_op != &ns_dentry_operations)
2357 return mnt;
2358
2359 if (!recurse && has_locked_children(old, old_path->dentry))
2360 return mnt;
2361
2362 if (recurse)
2363 mnt = copy_tree(old, old_path->dentry, CL_COPY_MNT_NS_FILE);
2364 else
2365 mnt = clone_mnt(old, old_path->dentry, 0);
2366
2367 if (!IS_ERR(mnt))
2368 mnt->mnt.mnt_flags &= ~MNT_LOCKED;
2369
2370 return mnt;
2371}
2372
2373/*
2374 * do loopback mount.
2375 */
2376static int do_loopback(struct path *path, const char *old_name,
2377 int recurse)
2378{
2379 struct path old_path;
2380 struct mount *mnt = NULL, *parent;
2381 struct mountpoint *mp;
2382 int err;
2383 if (!old_name || !*old_name)
2384 return -EINVAL;
2385 err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
2386 if (err)
2387 return err;
2388
2389 err = -EINVAL;
2390 if (mnt_ns_loop(old_path.dentry))
2391 goto out;
2392
2393 mp = lock_mount(path);
2394 if (IS_ERR(mp)) {
2395 err = PTR_ERR(mp);
2396 goto out;
2397 }
2398
2399 parent = real_mount(path->mnt);
2400 if (!check_mnt(parent))
2401 goto out2;
2402
2403 mnt = __do_loopback(&old_path, recurse);
2404 if (IS_ERR(mnt)) {
2405 err = PTR_ERR(mnt);
2406 goto out2;
2407 }
2408
2409 err = graft_tree(mnt, parent, mp);
2410 if (err) {
2411 lock_mount_hash();
2412 umount_tree(mnt, UMOUNT_SYNC);
2413 unlock_mount_hash();
2414 }
2415out2:
2416 unlock_mount(mp);
2417out:
2418 path_put(&old_path);
2419 return err;
2420}
2421
2422static struct file *open_detached_copy(struct path *path, bool recursive)
2423{
2424 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2425 struct mnt_namespace *ns = alloc_mnt_ns(user_ns, true);
2426 struct mount *mnt, *p;
2427 struct file *file;
2428
2429 if (IS_ERR(ns))
2430 return ERR_CAST(ns);
2431
2432 namespace_lock();
2433 mnt = __do_loopback(path, recursive);
2434 if (IS_ERR(mnt)) {
2435 namespace_unlock();
2436 free_mnt_ns(ns);
2437 return ERR_CAST(mnt);
2438 }
2439
2440 lock_mount_hash();
2441 for (p = mnt; p; p = next_mnt(p, mnt)) {
2442 p->mnt_ns = ns;
2443 ns->mounts++;
2444 }
2445 ns->root = mnt;
2446 list_add_tail(&ns->list, &mnt->mnt_list);
2447 mntget(&mnt->mnt);
2448 unlock_mount_hash();
2449 namespace_unlock();
2450
2451 mntput(path->mnt);
2452 path->mnt = &mnt->mnt;
2453 file = dentry_open(path, O_PATH, current_cred());
2454 if (IS_ERR(file))
2455 dissolve_on_fput(path->mnt);
2456 else
2457 file->f_mode |= FMODE_NEED_UNMOUNT;
2458 return file;
2459}
2460
2461SYSCALL_DEFINE3(open_tree, int, dfd, const char __user *, filename, unsigned, flags)
2462{
2463 struct file *file;
2464 struct path path;
2465 int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW;
2466 bool detached = flags & OPEN_TREE_CLONE;
2467 int error;
2468 int fd;
2469
2470 BUILD_BUG_ON(OPEN_TREE_CLOEXEC != O_CLOEXEC);
2471
2472 if (flags & ~(AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_RECURSIVE |
2473 AT_SYMLINK_NOFOLLOW | OPEN_TREE_CLONE |
2474 OPEN_TREE_CLOEXEC))
2475 return -EINVAL;
2476
2477 if ((flags & (AT_RECURSIVE | OPEN_TREE_CLONE)) == AT_RECURSIVE)
2478 return -EINVAL;
2479
2480 if (flags & AT_NO_AUTOMOUNT)
2481 lookup_flags &= ~LOOKUP_AUTOMOUNT;
2482 if (flags & AT_SYMLINK_NOFOLLOW)
2483 lookup_flags &= ~LOOKUP_FOLLOW;
2484 if (flags & AT_EMPTY_PATH)
2485 lookup_flags |= LOOKUP_EMPTY;
2486
2487 if (detached && !may_mount())
2488 return -EPERM;
2489
2490 fd = get_unused_fd_flags(flags & O_CLOEXEC);
2491 if (fd < 0)
2492 return fd;
2493
2494 error = user_path_at(dfd, filename, lookup_flags, &path);
2495 if (unlikely(error)) {
2496 file = ERR_PTR(error);
2497 } else {
2498 if (detached)
2499 file = open_detached_copy(&path, flags & AT_RECURSIVE);
2500 else
2501 file = dentry_open(&path, O_PATH, current_cred());
2502 path_put(&path);
2503 }
2504 if (IS_ERR(file)) {
2505 put_unused_fd(fd);
2506 return PTR_ERR(file);
2507 }
2508 fd_install(fd, file);
2509 return fd;
2510}
2511
2512/*
2513 * Don't allow locked mount flags to be cleared.
2514 *
2515 * No locks need to be held here while testing the various MNT_LOCK
2516 * flags because those flags can never be cleared once they are set.
2517 */
2518static bool can_change_locked_flags(struct mount *mnt, unsigned int mnt_flags)
2519{
2520 unsigned int fl = mnt->mnt.mnt_flags;
2521
2522 if ((fl & MNT_LOCK_READONLY) &&
2523 !(mnt_flags & MNT_READONLY))
2524 return false;
2525
2526 if ((fl & MNT_LOCK_NODEV) &&
2527 !(mnt_flags & MNT_NODEV))
2528 return false;
2529
2530 if ((fl & MNT_LOCK_NOSUID) &&
2531 !(mnt_flags & MNT_NOSUID))
2532 return false;
2533
2534 if ((fl & MNT_LOCK_NOEXEC) &&
2535 !(mnt_flags & MNT_NOEXEC))
2536 return false;
2537
2538 if ((fl & MNT_LOCK_ATIME) &&
2539 ((fl & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK)))
2540 return false;
2541
2542 return true;
2543}
2544
2545static int change_mount_ro_state(struct mount *mnt, unsigned int mnt_flags)
2546{
2547 bool readonly_request = (mnt_flags & MNT_READONLY);
2548
2549 if (readonly_request == __mnt_is_readonly(&mnt->mnt))
2550 return 0;
2551
2552 if (readonly_request)
2553 return mnt_make_readonly(mnt);
2554
2555 mnt->mnt.mnt_flags &= ~MNT_READONLY;
2556 return 0;
2557}
2558
2559static void set_mount_attributes(struct mount *mnt, unsigned int mnt_flags)
2560{
2561 mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;
2562 mnt->mnt.mnt_flags = mnt_flags;
2563 touch_mnt_namespace(mnt->mnt_ns);
2564}
2565
2566static void mnt_warn_timestamp_expiry(struct path *mountpoint, struct vfsmount *mnt)
2567{
2568 struct super_block *sb = mnt->mnt_sb;
2569
2570 if (!__mnt_is_readonly(mnt) &&
2571 (ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX > sb->s_time_max)) {
2572 char *buf = (char *)__get_free_page(GFP_KERNEL);
2573 char *mntpath = buf ? d_path(mountpoint, buf, PAGE_SIZE) : ERR_PTR(-ENOMEM);
2574 struct tm tm;
2575
2576 time64_to_tm(sb->s_time_max, 0, &tm);
2577
2578 pr_warn("%s filesystem being %s at %s supports timestamps until %04ld (0x%llx)\n",
2579 sb->s_type->name,
2580 is_mounted(mnt) ? "remounted" : "mounted",
2581 mntpath,
2582 tm.tm_year+1900, (unsigned long long)sb->s_time_max);
2583
2584 free_page((unsigned long)buf);
2585 }
2586}
2587
2588/*
2589 * Handle reconfiguration of the mountpoint only without alteration of the
2590 * superblock it refers to. This is triggered by specifying MS_REMOUNT|MS_BIND
2591 * to mount(2).
2592 */
2593static int do_reconfigure_mnt(struct path *path, unsigned int mnt_flags)
2594{
2595 struct super_block *sb = path->mnt->mnt_sb;
2596 struct mount *mnt = real_mount(path->mnt);
2597 int ret;
2598
2599 if (!check_mnt(mnt))
2600 return -EINVAL;
2601
2602 if (path->dentry != mnt->mnt.mnt_root)
2603 return -EINVAL;
2604
2605 if (!can_change_locked_flags(mnt, mnt_flags))
2606 return -EPERM;
2607
2608 /*
2609 * We're only checking whether the superblock is read-only not
2610 * changing it, so only take down_read(&sb->s_umount).
2611 */
2612 down_read(&sb->s_umount);
2613 lock_mount_hash();
2614 ret = change_mount_ro_state(mnt, mnt_flags);
2615 if (ret == 0)
2616 set_mount_attributes(mnt, mnt_flags);
2617 unlock_mount_hash();
2618 up_read(&sb->s_umount);
2619
2620 mnt_warn_timestamp_expiry(path, &mnt->mnt);
2621
2622 return ret;
2623}
2624
2625/*
2626 * change filesystem flags. dir should be a physical root of filesystem.
2627 * If you've mounted a non-root directory somewhere and want to do remount
2628 * on it - tough luck.
2629 */
2630static int do_remount(struct path *path, int ms_flags, int sb_flags,
2631 int mnt_flags, void *data)
2632{
2633 int err;
2634 struct super_block *sb = path->mnt->mnt_sb;
2635 struct mount *mnt = real_mount(path->mnt);
2636 struct fs_context *fc;
2637
2638 if (!check_mnt(mnt))
2639 return -EINVAL;
2640
2641 if (path->dentry != path->mnt->mnt_root)
2642 return -EINVAL;
2643
2644 if (!can_change_locked_flags(mnt, mnt_flags))
2645 return -EPERM;
2646
2647 fc = fs_context_for_reconfigure(path->dentry, sb_flags, MS_RMT_MASK);
2648 if (IS_ERR(fc))
2649 return PTR_ERR(fc);
2650
2651 fc->oldapi = true;
2652 err = parse_monolithic_mount_data(fc, data);
2653 if (!err) {
2654 down_write(&sb->s_umount);
2655 err = -EPERM;
2656 if (ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) {
2657 err = reconfigure_super(fc);
2658 if (!err) {
2659 lock_mount_hash();
2660 set_mount_attributes(mnt, mnt_flags);
2661 unlock_mount_hash();
2662 }
2663 }
2664 up_write(&sb->s_umount);
2665 }
2666
2667 mnt_warn_timestamp_expiry(path, &mnt->mnt);
2668
2669 put_fs_context(fc);
2670 return err;
2671}
2672
2673static inline int tree_contains_unbindable(struct mount *mnt)
2674{
2675 struct mount *p;
2676 for (p = mnt; p; p = next_mnt(p, mnt)) {
2677 if (IS_MNT_UNBINDABLE(p))
2678 return 1;
2679 }
2680 return 0;
2681}
2682
2683/*
2684 * Check that there aren't references to earlier/same mount namespaces in the
2685 * specified subtree. Such references can act as pins for mount namespaces
2686 * that aren't checked by the mount-cycle checking code, thereby allowing
2687 * cycles to be made.
2688 */
2689static bool check_for_nsfs_mounts(struct mount *subtree)
2690{
2691 struct mount *p;
2692 bool ret = false;
2693
2694 lock_mount_hash();
2695 for (p = subtree; p; p = next_mnt(p, subtree))
2696 if (mnt_ns_loop(p->mnt.mnt_root))
2697 goto out;
2698
2699 ret = true;
2700out:
2701 unlock_mount_hash();
2702 return ret;
2703}
2704
2705static int do_move_mount(struct path *old_path, struct path *new_path)
2706{
2707 struct mnt_namespace *ns;
2708 struct mount *p;
2709 struct mount *old;
2710 struct mount *parent;
2711 struct mountpoint *mp, *old_mp;
2712 int err;
2713 bool attached;
2714
2715 mp = lock_mount(new_path);
2716 if (IS_ERR(mp))
2717 return PTR_ERR(mp);
2718
2719 old = real_mount(old_path->mnt);
2720 p = real_mount(new_path->mnt);
2721 parent = old->mnt_parent;
2722 attached = mnt_has_parent(old);
2723 old_mp = old->mnt_mp;
2724 ns = old->mnt_ns;
2725
2726 err = -EINVAL;
2727 /* The mountpoint must be in our namespace. */
2728 if (!check_mnt(p))
2729 goto out;
2730
2731 /* The thing moved must be mounted... */
2732 if (!is_mounted(&old->mnt))
2733 goto out;
2734
2735 /* ... and either ours or the root of anon namespace */
2736 if (!(attached ? check_mnt(old) : is_anon_ns(ns)))
2737 goto out;
2738
2739 if (old->mnt.mnt_flags & MNT_LOCKED)
2740 goto out;
2741
2742 if (old_path->dentry != old_path->mnt->mnt_root)
2743 goto out;
2744
2745 if (d_is_dir(new_path->dentry) !=
2746 d_is_dir(old_path->dentry))
2747 goto out;
2748 /*
2749 * Don't move a mount residing in a shared parent.
2750 */
2751 if (attached && IS_MNT_SHARED(parent))
2752 goto out;
2753 /*
2754 * Don't move a mount tree containing unbindable mounts to a destination
2755 * mount which is shared.
2756 */
2757 if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
2758 goto out;
2759 err = -ELOOP;
2760 if (!check_for_nsfs_mounts(old))
2761 goto out;
2762 for (; mnt_has_parent(p); p = p->mnt_parent)
2763 if (p == old)
2764 goto out;
2765
2766 err = attach_recursive_mnt(old, real_mount(new_path->mnt), mp,
2767 attached);
2768 if (err)
2769 goto out;
2770
2771 /* if the mount is moved, it should no longer be expire
2772 * automatically */
2773 list_del_init(&old->mnt_expire);
2774 if (attached)
2775 put_mountpoint(old_mp);
2776out:
2777 unlock_mount(mp);
2778 if (!err) {
2779 if (attached)
2780 mntput_no_expire(parent);
2781 else
2782 free_mnt_ns(ns);
2783 }
2784 return err;
2785}
2786
2787static int do_move_mount_old(struct path *path, const char *old_name)
2788{
2789 struct path old_path;
2790 int err;
2791
2792 if (!old_name || !*old_name)
2793 return -EINVAL;
2794
2795 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
2796 if (err)
2797 return err;
2798
2799 err = do_move_mount(&old_path, path);
2800 path_put(&old_path);
2801 return err;
2802}
2803
2804/*
2805 * add a mount into a namespace's mount tree
2806 */
2807static int do_add_mount(struct mount *newmnt, struct mountpoint *mp,
2808 struct path *path, int mnt_flags)
2809{
2810 struct mount *parent = real_mount(path->mnt);
2811
2812 mnt_flags &= ~MNT_INTERNAL_FLAGS;
2813
2814 if (unlikely(!check_mnt(parent))) {
2815 /* that's acceptable only for automounts done in private ns */
2816 if (!(mnt_flags & MNT_SHRINKABLE))
2817 return -EINVAL;
2818 /* ... and for those we'd better have mountpoint still alive */
2819 if (!parent->mnt_ns)
2820 return -EINVAL;
2821 }
2822
2823 /* Refuse the same filesystem on the same mount point */
2824 if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb &&
2825 path->mnt->mnt_root == path->dentry)
2826 return -EBUSY;
2827
2828 if (d_is_symlink(newmnt->mnt.mnt_root))
2829 return -EINVAL;
2830
2831 newmnt->mnt.mnt_flags = mnt_flags;
2832 return graft_tree(newmnt, parent, mp);
2833}
2834
2835static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags);
2836
2837/*
2838 * Create a new mount using a superblock configuration and request it
2839 * be added to the namespace tree.
2840 */
2841static int do_new_mount_fc(struct fs_context *fc, struct path *mountpoint,
2842 unsigned int mnt_flags)
2843{
2844 struct vfsmount *mnt;
2845 struct mountpoint *mp;
2846 struct super_block *sb = fc->root->d_sb;
2847 int error;
2848
2849 error = security_sb_kern_mount(sb);
2850 if (!error && mount_too_revealing(sb, &mnt_flags))
2851 error = -EPERM;
2852
2853 if (unlikely(error)) {
2854 fc_drop_locked(fc);
2855 return error;
2856 }
2857
2858 up_write(&sb->s_umount);
2859
2860 mnt = vfs_create_mount(fc);
2861 if (IS_ERR(mnt))
2862 return PTR_ERR(mnt);
2863
2864 mnt_warn_timestamp_expiry(mountpoint, mnt);
2865
2866 mp = lock_mount(mountpoint);
2867 if (IS_ERR(mp)) {
2868 mntput(mnt);
2869 return PTR_ERR(mp);
2870 }
2871 error = do_add_mount(real_mount(mnt), mp, mountpoint, mnt_flags);
2872 unlock_mount(mp);
2873 if (error < 0)
2874 mntput(mnt);
2875 return error;
2876}
2877
2878/*
2879 * create a new mount for userspace and request it to be added into the
2880 * namespace's tree
2881 */
2882static int do_new_mount(struct path *path, const char *fstype, int sb_flags,
2883 int mnt_flags, const char *name, void *data)
2884{
2885 struct file_system_type *type;
2886 struct fs_context *fc;
2887 const char *subtype = NULL;
2888 int err = 0;
2889
2890 if (!fstype)
2891 return -EINVAL;
2892
2893 type = get_fs_type(fstype);
2894 if (!type)
2895 return -ENODEV;
2896
2897 if (type->fs_flags & FS_HAS_SUBTYPE) {
2898 subtype = strchr(fstype, '.');
2899 if (subtype) {
2900 subtype++;
2901 if (!*subtype) {
2902 put_filesystem(type);
2903 return -EINVAL;
2904 }
2905 }
2906 }
2907
2908 fc = fs_context_for_mount(type, sb_flags);
2909 put_filesystem(type);
2910 if (IS_ERR(fc))
2911 return PTR_ERR(fc);
2912
2913 if (subtype)
2914 err = vfs_parse_fs_string(fc, "subtype",
2915 subtype, strlen(subtype));
2916 if (!err && name)
2917 err = vfs_parse_fs_string(fc, "source", name, strlen(name));
2918 if (!err)
2919 err = parse_monolithic_mount_data(fc, data);
2920 if (!err && !mount_capable(fc))
2921 err = -EPERM;
2922 if (!err)
2923 err = vfs_get_tree(fc);
2924 if (!err)
2925 err = do_new_mount_fc(fc, path, mnt_flags);
2926
2927 put_fs_context(fc);
2928 return err;
2929}
2930
2931int finish_automount(struct vfsmount *m, struct path *path)
2932{
2933 struct dentry *dentry = path->dentry;
2934 struct mountpoint *mp;
2935 struct mount *mnt;
2936 int err;
2937
2938 if (!m)
2939 return 0;
2940 if (IS_ERR(m))
2941 return PTR_ERR(m);
2942
2943 mnt = real_mount(m);
2944 /* The new mount record should have at least 2 refs to prevent it being
2945 * expired before we get a chance to add it
2946 */
2947 BUG_ON(mnt_get_count(mnt) < 2);
2948
2949 if (m->mnt_sb == path->mnt->mnt_sb &&
2950 m->mnt_root == dentry) {
2951 err = -ELOOP;
2952 goto discard;
2953 }
2954
2955 /*
2956 * we don't want to use lock_mount() - in this case finding something
2957 * that overmounts our mountpoint to be means "quitely drop what we've
2958 * got", not "try to mount it on top".
2959 */
2960 inode_lock(dentry->d_inode);
2961 namespace_lock();
2962 if (unlikely(cant_mount(dentry))) {
2963 err = -ENOENT;
2964 goto discard_locked;
2965 }
2966 rcu_read_lock();
2967 if (unlikely(__lookup_mnt(path->mnt, dentry))) {
2968 rcu_read_unlock();
2969 err = 0;
2970 goto discard_locked;
2971 }
2972 rcu_read_unlock();
2973 mp = get_mountpoint(dentry);
2974 if (IS_ERR(mp)) {
2975 err = PTR_ERR(mp);
2976 goto discard_locked;
2977 }
2978
2979 err = do_add_mount(mnt, mp, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
2980 unlock_mount(mp);
2981 if (unlikely(err))
2982 goto discard;
2983 mntput(m);
2984 return 0;
2985
2986discard_locked:
2987 namespace_unlock();
2988 inode_unlock(dentry->d_inode);
2989discard:
2990 /* remove m from any expiration list it may be on */
2991 if (!list_empty(&mnt->mnt_expire)) {
2992 namespace_lock();
2993 list_del_init(&mnt->mnt_expire);
2994 namespace_unlock();
2995 }
2996 mntput(m);
2997 mntput(m);
2998 return err;
2999}
3000
3001/**
3002 * mnt_set_expiry - Put a mount on an expiration list
3003 * @mnt: The mount to list.
3004 * @expiry_list: The list to add the mount to.
3005 */
3006void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
3007{
3008 namespace_lock();
3009
3010 list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
3011
3012 namespace_unlock();
3013}
3014EXPORT_SYMBOL(mnt_set_expiry);
3015
3016/*
3017 * process a list of expirable mountpoints with the intent of discarding any
3018 * mountpoints that aren't in use and haven't been touched since last we came
3019 * here
3020 */
3021void mark_mounts_for_expiry(struct list_head *mounts)
3022{
3023 struct mount *mnt, *next;
3024 LIST_HEAD(graveyard);
3025
3026 if (list_empty(mounts))
3027 return;
3028
3029 namespace_lock();
3030 lock_mount_hash();
3031
3032 /* extract from the expiration list every vfsmount that matches the
3033 * following criteria:
3034 * - only referenced by its parent vfsmount
3035 * - still marked for expiry (marked on the last call here; marks are
3036 * cleared by mntput())
3037 */
3038 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
3039 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
3040 propagate_mount_busy(mnt, 1))
3041 continue;
3042 list_move(&mnt->mnt_expire, &graveyard);
3043 }
3044 while (!list_empty(&graveyard)) {
3045 mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
3046 touch_mnt_namespace(mnt->mnt_ns);
3047 umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
3048 }
3049 unlock_mount_hash();
3050 namespace_unlock();
3051}
3052
3053EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
3054
3055/*
3056 * Ripoff of 'select_parent()'
3057 *
3058 * search the list of submounts for a given mountpoint, and move any
3059 * shrinkable submounts to the 'graveyard' list.
3060 */
3061static int select_submounts(struct mount *parent, struct list_head *graveyard)
3062{
3063 struct mount *this_parent = parent;
3064 struct list_head *next;
3065 int found = 0;
3066
3067repeat:
3068 next = this_parent->mnt_mounts.next;
3069resume:
3070 while (next != &this_parent->mnt_mounts) {
3071 struct list_head *tmp = next;
3072 struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
3073
3074 next = tmp->next;
3075 if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
3076 continue;
3077 /*
3078 * Descend a level if the d_mounts list is non-empty.
3079 */
3080 if (!list_empty(&mnt->mnt_mounts)) {
3081 this_parent = mnt;
3082 goto repeat;
3083 }
3084
3085 if (!propagate_mount_busy(mnt, 1)) {
3086 list_move_tail(&mnt->mnt_expire, graveyard);
3087 found++;
3088 }
3089 }
3090 /*
3091 * All done at this level ... ascend and resume the search
3092 */
3093 if (this_parent != parent) {
3094 next = this_parent->mnt_child.next;
3095 this_parent = this_parent->mnt_parent;
3096 goto resume;
3097 }
3098 return found;
3099}
3100
3101/*
3102 * process a list of expirable mountpoints with the intent of discarding any
3103 * submounts of a specific parent mountpoint
3104 *
3105 * mount_lock must be held for write
3106 */
3107static void shrink_submounts(struct mount *mnt)
3108{
3109 LIST_HEAD(graveyard);
3110 struct mount *m;
3111
3112 /* extract submounts of 'mountpoint' from the expiration list */
3113 while (select_submounts(mnt, &graveyard)) {
3114 while (!list_empty(&graveyard)) {
3115 m = list_first_entry(&graveyard, struct mount,
3116 mnt_expire);
3117 touch_mnt_namespace(m->mnt_ns);
3118 umount_tree(m, UMOUNT_PROPAGATE|UMOUNT_SYNC);
3119 }
3120 }
3121}
3122
3123static void *copy_mount_options(const void __user * data)
3124{
3125 char *copy;
3126 unsigned left, offset;
3127
3128 if (!data)
3129 return NULL;
3130
3131 copy = kmalloc(PAGE_SIZE, GFP_KERNEL);
3132 if (!copy)
3133 return ERR_PTR(-ENOMEM);
3134
3135 left = copy_from_user(copy, data, PAGE_SIZE);
3136
3137 /*
3138 * Not all architectures have an exact copy_from_user(). Resort to
3139 * byte at a time.
3140 */
3141 offset = PAGE_SIZE - left;
3142 while (left) {
3143 char c;
3144 if (get_user(c, (const char __user *)data + offset))
3145 break;
3146 copy[offset] = c;
3147 left--;
3148 offset++;
3149 }
3150
3151 if (left == PAGE_SIZE) {
3152 kfree(copy);
3153 return ERR_PTR(-EFAULT);
3154 }
3155
3156 return copy;
3157}
3158
3159static char *copy_mount_string(const void __user *data)
3160{
3161 return data ? strndup_user(data, PATH_MAX) : NULL;
3162}
3163
3164/*
3165 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
3166 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
3167 *
3168 * data is a (void *) that can point to any structure up to
3169 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
3170 * information (or be NULL).
3171 *
3172 * Pre-0.97 versions of mount() didn't have a flags word.
3173 * When the flags word was introduced its top half was required
3174 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
3175 * Therefore, if this magic number is present, it carries no information
3176 * and must be discarded.
3177 */
3178int path_mount(const char *dev_name, struct path *path,
3179 const char *type_page, unsigned long flags, void *data_page)
3180{
3181 unsigned int mnt_flags = 0, sb_flags;
3182 int ret;
3183
3184 /* Discard magic */
3185 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
3186 flags &= ~MS_MGC_MSK;
3187
3188 /* Basic sanity checks */
3189 if (data_page)
3190 ((char *)data_page)[PAGE_SIZE - 1] = 0;
3191
3192 if (flags & MS_NOUSER)
3193 return -EINVAL;
3194
3195 ret = security_sb_mount(dev_name, path, type_page, flags, data_page);
3196 if (ret)
3197 return ret;
3198 if (!may_mount())
3199 return -EPERM;
3200 if ((flags & SB_MANDLOCK) && !may_mandlock())
3201 return -EPERM;
3202
3203 /* Default to relatime unless overriden */
3204 if (!(flags & MS_NOATIME))
3205 mnt_flags |= MNT_RELATIME;
3206
3207 /* Separate the per-mountpoint flags */
3208 if (flags & MS_NOSUID)
3209 mnt_flags |= MNT_NOSUID;
3210 if (flags & MS_NODEV)
3211 mnt_flags |= MNT_NODEV;
3212 if (flags & MS_NOEXEC)
3213 mnt_flags |= MNT_NOEXEC;
3214 if (flags & MS_NOATIME)
3215 mnt_flags |= MNT_NOATIME;
3216 if (flags & MS_NODIRATIME)
3217 mnt_flags |= MNT_NODIRATIME;
3218 if (flags & MS_STRICTATIME)
3219 mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
3220 if (flags & MS_RDONLY)
3221 mnt_flags |= MNT_READONLY;
3222 if (flags & MS_NOSYMFOLLOW)
3223 mnt_flags |= MNT_NOSYMFOLLOW;
3224
3225 /* The default atime for remount is preservation */
3226 if ((flags & MS_REMOUNT) &&
3227 ((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME |
3228 MS_STRICTATIME)) == 0)) {
3229 mnt_flags &= ~MNT_ATIME_MASK;
3230 mnt_flags |= path->mnt->mnt_flags & MNT_ATIME_MASK;
3231 }
3232
3233 sb_flags = flags & (SB_RDONLY |
3234 SB_SYNCHRONOUS |
3235 SB_MANDLOCK |
3236 SB_DIRSYNC |
3237 SB_SILENT |
3238 SB_POSIXACL |
3239 SB_LAZYTIME |
3240 SB_I_VERSION);
3241
3242 if ((flags & (MS_REMOUNT | MS_BIND)) == (MS_REMOUNT | MS_BIND))
3243 return do_reconfigure_mnt(path, mnt_flags);
3244 if (flags & MS_REMOUNT)
3245 return do_remount(path, flags, sb_flags, mnt_flags, data_page);
3246 if (flags & MS_BIND)
3247 return do_loopback(path, dev_name, flags & MS_REC);
3248 if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
3249 return do_change_type(path, flags);
3250 if (flags & MS_MOVE)
3251 return do_move_mount_old(path, dev_name);
3252
3253 return do_new_mount(path, type_page, sb_flags, mnt_flags, dev_name,
3254 data_page);
3255}
3256
3257long do_mount(const char *dev_name, const char __user *dir_name,
3258 const char *type_page, unsigned long flags, void *data_page)
3259{
3260 struct path path;
3261 int ret;
3262
3263 ret = user_path_at(AT_FDCWD, dir_name, LOOKUP_FOLLOW, &path);
3264 if (ret)
3265 return ret;
3266 ret = path_mount(dev_name, &path, type_page, flags, data_page);
3267 path_put(&path);
3268 return ret;
3269}
3270
3271static struct ucounts *inc_mnt_namespaces(struct user_namespace *ns)
3272{
3273 return inc_ucount(ns, current_euid(), UCOUNT_MNT_NAMESPACES);
3274}
3275
3276static void dec_mnt_namespaces(struct ucounts *ucounts)
3277{
3278 dec_ucount(ucounts, UCOUNT_MNT_NAMESPACES);
3279}
3280
3281static void free_mnt_ns(struct mnt_namespace *ns)
3282{
3283 if (!is_anon_ns(ns))
3284 ns_free_inum(&ns->ns);
3285 dec_mnt_namespaces(ns->ucounts);
3286 put_user_ns(ns->user_ns);
3287 kfree(ns);
3288}
3289
3290/*
3291 * Assign a sequence number so we can detect when we attempt to bind
3292 * mount a reference to an older mount namespace into the current
3293 * mount namespace, preventing reference counting loops. A 64bit
3294 * number incrementing at 10Ghz will take 12,427 years to wrap which
3295 * is effectively never, so we can ignore the possibility.
3296 */
3297static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
3298
3299static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool anon)
3300{
3301 struct mnt_namespace *new_ns;
3302 struct ucounts *ucounts;
3303 int ret;
3304
3305 ucounts = inc_mnt_namespaces(user_ns);
3306 if (!ucounts)
3307 return ERR_PTR(-ENOSPC);
3308
3309 new_ns = kzalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
3310 if (!new_ns) {
3311 dec_mnt_namespaces(ucounts);
3312 return ERR_PTR(-ENOMEM);
3313 }
3314 if (!anon) {
3315 ret = ns_alloc_inum(&new_ns->ns);
3316 if (ret) {
3317 kfree(new_ns);
3318 dec_mnt_namespaces(ucounts);
3319 return ERR_PTR(ret);
3320 }
3321 }
3322 new_ns->ns.ops = &mntns_operations;
3323 if (!anon)
3324 new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
3325 refcount_set(&new_ns->ns.count, 1);
3326 INIT_LIST_HEAD(&new_ns->list);
3327 init_waitqueue_head(&new_ns->poll);
3328 spin_lock_init(&new_ns->ns_lock);
3329 new_ns->user_ns = get_user_ns(user_ns);
3330 new_ns->ucounts = ucounts;
3331 return new_ns;
3332}
3333
3334__latent_entropy
3335struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
3336 struct user_namespace *user_ns, struct fs_struct *new_fs)
3337{
3338 struct mnt_namespace *new_ns;
3339 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
3340 struct mount *p, *q;
3341 struct mount *old;
3342 struct mount *new;
3343 int copy_flags;
3344
3345 BUG_ON(!ns);
3346
3347 if (likely(!(flags & CLONE_NEWNS))) {
3348 get_mnt_ns(ns);
3349 return ns;
3350 }
3351
3352 old = ns->root;
3353
3354 new_ns = alloc_mnt_ns(user_ns, false);
3355 if (IS_ERR(new_ns))
3356 return new_ns;
3357
3358 namespace_lock();
3359 /* First pass: copy the tree topology */
3360 copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
3361 if (user_ns != ns->user_ns)
3362 copy_flags |= CL_SHARED_TO_SLAVE;
3363 new = copy_tree(old, old->mnt.mnt_root, copy_flags);
3364 if (IS_ERR(new)) {
3365 namespace_unlock();
3366 free_mnt_ns(new_ns);
3367 return ERR_CAST(new);
3368 }
3369 if (user_ns != ns->user_ns) {
3370 lock_mount_hash();
3371 lock_mnt_tree(new);
3372 unlock_mount_hash();
3373 }
3374 new_ns->root = new;
3375 list_add_tail(&new_ns->list, &new->mnt_list);
3376
3377 /*
3378 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
3379 * as belonging to new namespace. We have already acquired a private
3380 * fs_struct, so tsk->fs->lock is not needed.
3381 */
3382 p = old;
3383 q = new;
3384 while (p) {
3385 q->mnt_ns = new_ns;
3386 new_ns->mounts++;
3387 if (new_fs) {
3388 if (&p->mnt == new_fs->root.mnt) {
3389 new_fs->root.mnt = mntget(&q->mnt);
3390 rootmnt = &p->mnt;
3391 }
3392 if (&p->mnt == new_fs->pwd.mnt) {
3393 new_fs->pwd.mnt = mntget(&q->mnt);
3394 pwdmnt = &p->mnt;
3395 }
3396 }
3397 p = next_mnt(p, old);
3398 q = next_mnt(q, new);
3399 if (!q)
3400 break;
3401 while (p->mnt.mnt_root != q->mnt.mnt_root)
3402 p = next_mnt(p, old);
3403 }
3404 namespace_unlock();
3405
3406 if (rootmnt)
3407 mntput(rootmnt);
3408 if (pwdmnt)
3409 mntput(pwdmnt);
3410
3411 return new_ns;
3412}
3413
3414struct dentry *mount_subtree(struct vfsmount *m, const char *name)
3415{
3416 struct mount *mnt = real_mount(m);
3417 struct mnt_namespace *ns;
3418 struct super_block *s;
3419 struct path path;
3420 int err;
3421
3422 ns = alloc_mnt_ns(&init_user_ns, true);
3423 if (IS_ERR(ns)) {
3424 mntput(m);
3425 return ERR_CAST(ns);
3426 }
3427 mnt->mnt_ns = ns;
3428 ns->root = mnt;
3429 ns->mounts++;
3430 list_add(&mnt->mnt_list, &ns->list);
3431
3432 err = vfs_path_lookup(m->mnt_root, m,
3433 name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
3434
3435 put_mnt_ns(ns);
3436
3437 if (err)
3438 return ERR_PTR(err);
3439
3440 /* trade a vfsmount reference for active sb one */
3441 s = path.mnt->mnt_sb;
3442 atomic_inc(&s->s_active);
3443 mntput(path.mnt);
3444 /* lock the sucker */
3445 down_write(&s->s_umount);
3446 /* ... and return the root of (sub)tree on it */
3447 return path.dentry;
3448}
3449EXPORT_SYMBOL(mount_subtree);
3450
3451SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
3452 char __user *, type, unsigned long, flags, void __user *, data)
3453{
3454 int ret;
3455 char *kernel_type;
3456 char *kernel_dev;
3457 void *options;
3458
3459 kernel_type = copy_mount_string(type);
3460 ret = PTR_ERR(kernel_type);
3461 if (IS_ERR(kernel_type))
3462 goto out_type;
3463
3464 kernel_dev = copy_mount_string(dev_name);
3465 ret = PTR_ERR(kernel_dev);
3466 if (IS_ERR(kernel_dev))
3467 goto out_dev;
3468
3469 options = copy_mount_options(data);
3470 ret = PTR_ERR(options);
3471 if (IS_ERR(options))
3472 goto out_data;
3473
3474 ret = do_mount(kernel_dev, dir_name, kernel_type, flags, options);
3475
3476 kfree(options);
3477out_data:
3478 kfree(kernel_dev);
3479out_dev:
3480 kfree(kernel_type);
3481out_type:
3482 return ret;
3483}
3484
3485#define FSMOUNT_VALID_FLAGS \
3486 (MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \
3487 MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME | \
3488 MOUNT_ATTR_NOSYMFOLLOW)
3489
3490#define MOUNT_SETATTR_VALID_FLAGS (FSMOUNT_VALID_FLAGS | MOUNT_ATTR_IDMAP)
3491
3492#define MOUNT_SETATTR_PROPAGATION_FLAGS \
3493 (MS_UNBINDABLE | MS_PRIVATE | MS_SLAVE | MS_SHARED)
3494
3495static unsigned int attr_flags_to_mnt_flags(u64 attr_flags)
3496{
3497 unsigned int mnt_flags = 0;
3498
3499 if (attr_flags & MOUNT_ATTR_RDONLY)
3500 mnt_flags |= MNT_READONLY;
3501 if (attr_flags & MOUNT_ATTR_NOSUID)
3502 mnt_flags |= MNT_NOSUID;
3503 if (attr_flags & MOUNT_ATTR_NODEV)
3504 mnt_flags |= MNT_NODEV;
3505 if (attr_flags & MOUNT_ATTR_NOEXEC)
3506 mnt_flags |= MNT_NOEXEC;
3507 if (attr_flags & MOUNT_ATTR_NODIRATIME)
3508 mnt_flags |= MNT_NODIRATIME;
3509 if (attr_flags & MOUNT_ATTR_NOSYMFOLLOW)
3510 mnt_flags |= MNT_NOSYMFOLLOW;
3511
3512 return mnt_flags;
3513}
3514
3515/*
3516 * Create a kernel mount representation for a new, prepared superblock
3517 * (specified by fs_fd) and attach to an open_tree-like file descriptor.
3518 */
3519SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
3520 unsigned int, attr_flags)
3521{
3522 struct mnt_namespace *ns;
3523 struct fs_context *fc;
3524 struct file *file;
3525 struct path newmount;
3526 struct mount *mnt;
3527 struct fd f;
3528 unsigned int mnt_flags = 0;
3529 long ret;
3530
3531 if (!may_mount())
3532 return -EPERM;
3533
3534 if ((flags & ~(FSMOUNT_CLOEXEC)) != 0)
3535 return -EINVAL;
3536
3537 if (attr_flags & ~FSMOUNT_VALID_FLAGS)
3538 return -EINVAL;
3539
3540 mnt_flags = attr_flags_to_mnt_flags(attr_flags);
3541
3542 switch (attr_flags & MOUNT_ATTR__ATIME) {
3543 case MOUNT_ATTR_STRICTATIME:
3544 break;
3545 case MOUNT_ATTR_NOATIME:
3546 mnt_flags |= MNT_NOATIME;
3547 break;
3548 case MOUNT_ATTR_RELATIME:
3549 mnt_flags |= MNT_RELATIME;
3550 break;
3551 default:
3552 return -EINVAL;
3553 }
3554
3555 f = fdget(fs_fd);
3556 if (!f.file)
3557 return -EBADF;
3558
3559 ret = -EINVAL;
3560 if (f.file->f_op != &fscontext_fops)
3561 goto err_fsfd;
3562
3563 fc = f.file->private_data;
3564
3565 ret = mutex_lock_interruptible(&fc->uapi_mutex);
3566 if (ret < 0)
3567 goto err_fsfd;
3568
3569 /* There must be a valid superblock or we can't mount it */
3570 ret = -EINVAL;
3571 if (!fc->root)
3572 goto err_unlock;
3573
3574 ret = -EPERM;
3575 if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) {
3576 pr_warn("VFS: Mount too revealing\n");
3577 goto err_unlock;
3578 }
3579
3580 ret = -EBUSY;
3581 if (fc->phase != FS_CONTEXT_AWAITING_MOUNT)
3582 goto err_unlock;
3583
3584 ret = -EPERM;
3585 if ((fc->sb_flags & SB_MANDLOCK) && !may_mandlock())
3586 goto err_unlock;
3587
3588 newmount.mnt = vfs_create_mount(fc);
3589 if (IS_ERR(newmount.mnt)) {
3590 ret = PTR_ERR(newmount.mnt);
3591 goto err_unlock;
3592 }
3593 newmount.dentry = dget(fc->root);
3594 newmount.mnt->mnt_flags = mnt_flags;
3595
3596 /* We've done the mount bit - now move the file context into more or
3597 * less the same state as if we'd done an fspick(). We don't want to
3598 * do any memory allocation or anything like that at this point as we
3599 * don't want to have to handle any errors incurred.
3600 */
3601 vfs_clean_context(fc);
3602
3603 ns = alloc_mnt_ns(current->nsproxy->mnt_ns->user_ns, true);
3604 if (IS_ERR(ns)) {
3605 ret = PTR_ERR(ns);
3606 goto err_path;
3607 }
3608 mnt = real_mount(newmount.mnt);
3609 mnt->mnt_ns = ns;
3610 ns->root = mnt;
3611 ns->mounts = 1;
3612 list_add(&mnt->mnt_list, &ns->list);
3613 mntget(newmount.mnt);
3614
3615 /* Attach to an apparent O_PATH fd with a note that we need to unmount
3616 * it, not just simply put it.
3617 */
3618 file = dentry_open(&newmount, O_PATH, fc->cred);
3619 if (IS_ERR(file)) {
3620 dissolve_on_fput(newmount.mnt);
3621 ret = PTR_ERR(file);
3622 goto err_path;
3623 }
3624 file->f_mode |= FMODE_NEED_UNMOUNT;
3625
3626 ret = get_unused_fd_flags((flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0);
3627 if (ret >= 0)
3628 fd_install(ret, file);
3629 else
3630 fput(file);
3631
3632err_path:
3633 path_put(&newmount);
3634err_unlock:
3635 mutex_unlock(&fc->uapi_mutex);
3636err_fsfd:
3637 fdput(f);
3638 return ret;
3639}
3640
3641/*
3642 * Move a mount from one place to another. In combination with
3643 * fsopen()/fsmount() this is used to install a new mount and in combination
3644 * with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy
3645 * a mount subtree.
3646 *
3647 * Note the flags value is a combination of MOVE_MOUNT_* flags.
3648 */
3649SYSCALL_DEFINE5(move_mount,
3650 int, from_dfd, const char __user *, from_pathname,
3651 int, to_dfd, const char __user *, to_pathname,
3652 unsigned int, flags)
3653{
3654 struct path from_path, to_path;
3655 unsigned int lflags;
3656 int ret = 0;
3657
3658 if (!may_mount())
3659 return -EPERM;
3660
3661 if (flags & ~MOVE_MOUNT__MASK)
3662 return -EINVAL;
3663
3664 /* If someone gives a pathname, they aren't permitted to move
3665 * from an fd that requires unmount as we can't get at the flag
3666 * to clear it afterwards.
3667 */
3668 lflags = 0;
3669 if (flags & MOVE_MOUNT_F_SYMLINKS) lflags |= LOOKUP_FOLLOW;
3670 if (flags & MOVE_MOUNT_F_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT;
3671 if (flags & MOVE_MOUNT_F_EMPTY_PATH) lflags |= LOOKUP_EMPTY;
3672
3673 ret = user_path_at(from_dfd, from_pathname, lflags, &from_path);
3674 if (ret < 0)
3675 return ret;
3676
3677 lflags = 0;
3678 if (flags & MOVE_MOUNT_T_SYMLINKS) lflags |= LOOKUP_FOLLOW;
3679 if (flags & MOVE_MOUNT_T_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT;
3680 if (flags & MOVE_MOUNT_T_EMPTY_PATH) lflags |= LOOKUP_EMPTY;
3681
3682 ret = user_path_at(to_dfd, to_pathname, lflags, &to_path);
3683 if (ret < 0)
3684 goto out_from;
3685
3686 ret = security_move_mount(&from_path, &to_path);
3687 if (ret < 0)
3688 goto out_to;
3689
3690 ret = do_move_mount(&from_path, &to_path);
3691
3692out_to:
3693 path_put(&to_path);
3694out_from:
3695 path_put(&from_path);
3696 return ret;
3697}
3698
3699/*
3700 * Return true if path is reachable from root
3701 *
3702 * namespace_sem or mount_lock is held
3703 */
3704bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
3705 const struct path *root)
3706{
3707 while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
3708 dentry = mnt->mnt_mountpoint;
3709 mnt = mnt->mnt_parent;
3710 }
3711 return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
3712}
3713
3714bool path_is_under(const struct path *path1, const struct path *path2)
3715{
3716 bool res;
3717 read_seqlock_excl(&mount_lock);
3718 res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2);
3719 read_sequnlock_excl(&mount_lock);
3720 return res;
3721}
3722EXPORT_SYMBOL(path_is_under);
3723
3724/*
3725 * pivot_root Semantics:
3726 * Moves the root file system of the current process to the directory put_old,
3727 * makes new_root as the new root file system of the current process, and sets
3728 * root/cwd of all processes which had them on the current root to new_root.
3729 *
3730 * Restrictions:
3731 * The new_root and put_old must be directories, and must not be on the
3732 * same file system as the current process root. The put_old must be
3733 * underneath new_root, i.e. adding a non-zero number of /.. to the string
3734 * pointed to by put_old must yield the same directory as new_root. No other
3735 * file system may be mounted on put_old. After all, new_root is a mountpoint.
3736 *
3737 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
3738 * See Documentation/filesystems/ramfs-rootfs-initramfs.rst for alternatives
3739 * in this situation.
3740 *
3741 * Notes:
3742 * - we don't move root/cwd if they are not at the root (reason: if something
3743 * cared enough to change them, it's probably wrong to force them elsewhere)
3744 * - it's okay to pick a root that isn't the root of a file system, e.g.
3745 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
3746 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
3747 * first.
3748 */
3749SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
3750 const char __user *, put_old)
3751{
3752 struct path new, old, root;
3753 struct mount *new_mnt, *root_mnt, *old_mnt, *root_parent, *ex_parent;
3754 struct mountpoint *old_mp, *root_mp;
3755 int error;
3756
3757 if (!may_mount())
3758 return -EPERM;
3759
3760 error = user_path_at(AT_FDCWD, new_root,
3761 LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &new);
3762 if (error)
3763 goto out0;
3764
3765 error = user_path_at(AT_FDCWD, put_old,
3766 LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old);
3767 if (error)
3768 goto out1;
3769
3770 error = security_sb_pivotroot(&old, &new);
3771 if (error)
3772 goto out2;
3773
3774 get_fs_root(current->fs, &root);
3775 old_mp = lock_mount(&old);
3776 error = PTR_ERR(old_mp);
3777 if (IS_ERR(old_mp))
3778 goto out3;
3779
3780 error = -EINVAL;
3781 new_mnt = real_mount(new.mnt);
3782 root_mnt = real_mount(root.mnt);
3783 old_mnt = real_mount(old.mnt);
3784 ex_parent = new_mnt->mnt_parent;
3785 root_parent = root_mnt->mnt_parent;
3786 if (IS_MNT_SHARED(old_mnt) ||
3787 IS_MNT_SHARED(ex_parent) ||
3788 IS_MNT_SHARED(root_parent))
3789 goto out4;
3790 if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
3791 goto out4;
3792 if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
3793 goto out4;
3794 error = -ENOENT;
3795 if (d_unlinked(new.dentry))
3796 goto out4;
3797 error = -EBUSY;
3798 if (new_mnt == root_mnt || old_mnt == root_mnt)
3799 goto out4; /* loop, on the same file system */
3800 error = -EINVAL;
3801 if (root.mnt->mnt_root != root.dentry)
3802 goto out4; /* not a mountpoint */
3803 if (!mnt_has_parent(root_mnt))
3804 goto out4; /* not attached */
3805 if (new.mnt->mnt_root != new.dentry)
3806 goto out4; /* not a mountpoint */
3807 if (!mnt_has_parent(new_mnt))
3808 goto out4; /* not attached */
3809 /* make sure we can reach put_old from new_root */
3810 if (!is_path_reachable(old_mnt, old.dentry, &new))
3811 goto out4;
3812 /* make certain new is below the root */
3813 if (!is_path_reachable(new_mnt, new.dentry, &root))
3814 goto out4;
3815 lock_mount_hash();
3816 umount_mnt(new_mnt);
3817 root_mp = unhash_mnt(root_mnt); /* we'll need its mountpoint */
3818 if (root_mnt->mnt.mnt_flags & MNT_LOCKED) {
3819 new_mnt->mnt.mnt_flags |= MNT_LOCKED;
3820 root_mnt->mnt.mnt_flags &= ~MNT_LOCKED;
3821 }
3822 /* mount old root on put_old */
3823 attach_mnt(root_mnt, old_mnt, old_mp);
3824 /* mount new_root on / */
3825 attach_mnt(new_mnt, root_parent, root_mp);
3826 mnt_add_count(root_parent, -1);
3827 touch_mnt_namespace(current->nsproxy->mnt_ns);
3828 /* A moved mount should not expire automatically */
3829 list_del_init(&new_mnt->mnt_expire);
3830 put_mountpoint(root_mp);
3831 unlock_mount_hash();
3832 chroot_fs_refs(&root, &new);
3833 error = 0;
3834out4:
3835 unlock_mount(old_mp);
3836 if (!error)
3837 mntput_no_expire(ex_parent);
3838out3:
3839 path_put(&root);
3840out2:
3841 path_put(&old);
3842out1:
3843 path_put(&new);
3844out0:
3845 return error;
3846}
3847
3848static unsigned int recalc_flags(struct mount_kattr *kattr, struct mount *mnt)
3849{
3850 unsigned int flags = mnt->mnt.mnt_flags;
3851
3852 /* flags to clear */
3853 flags &= ~kattr->attr_clr;
3854 /* flags to raise */
3855 flags |= kattr->attr_set;
3856
3857 return flags;
3858}
3859
3860static int can_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
3861{
3862 struct vfsmount *m = &mnt->mnt;
3863
3864 if (!kattr->mnt_userns)
3865 return 0;
3866
3867 /*
3868 * Once a mount has been idmapped we don't allow it to change its
3869 * mapping. It makes things simpler and callers can just create
3870 * another bind-mount they can idmap if they want to.
3871 */
3872 if (mnt_user_ns(m) != &init_user_ns)
3873 return -EPERM;
3874
3875 /* The underlying filesystem doesn't support idmapped mounts yet. */
3876 if (!(m->mnt_sb->s_type->fs_flags & FS_ALLOW_IDMAP))
3877 return -EINVAL;
3878
3879 /* Don't yet support filesystem mountable in user namespaces. */
3880 if (m->mnt_sb->s_user_ns != &init_user_ns)
3881 return -EINVAL;
3882
3883 /* We're not controlling the superblock. */
3884 if (!capable(CAP_SYS_ADMIN))
3885 return -EPERM;
3886
3887 /* Mount has already been visible in the filesystem hierarchy. */
3888 if (!is_anon_ns(mnt->mnt_ns))
3889 return -EINVAL;
3890
3891 return 0;
3892}
3893
3894static struct mount *mount_setattr_prepare(struct mount_kattr *kattr,
3895 struct mount *mnt, int *err)
3896{
3897 struct mount *m = mnt, *last = NULL;
3898
3899 if (!is_mounted(&m->mnt)) {
3900 *err = -EINVAL;
3901 goto out;
3902 }
3903
3904 if (!(mnt_has_parent(m) ? check_mnt(m) : is_anon_ns(m->mnt_ns))) {
3905 *err = -EINVAL;
3906 goto out;
3907 }
3908
3909 do {
3910 unsigned int flags;
3911
3912 flags = recalc_flags(kattr, m);
3913 if (!can_change_locked_flags(m, flags)) {
3914 *err = -EPERM;
3915 goto out;
3916 }
3917
3918 *err = can_idmap_mount(kattr, m);
3919 if (*err)
3920 goto out;
3921
3922 last = m;
3923
3924 if ((kattr->attr_set & MNT_READONLY) &&
3925 !(m->mnt.mnt_flags & MNT_READONLY)) {
3926 *err = mnt_hold_writers(m);
3927 if (*err)
3928 goto out;
3929 }
3930 } while (kattr->recurse && (m = next_mnt(m, mnt)));
3931
3932out:
3933 return last;
3934}
3935
3936static void do_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
3937{
3938 struct user_namespace *mnt_userns;
3939
3940 if (!kattr->mnt_userns)
3941 return;
3942
3943 mnt_userns = get_user_ns(kattr->mnt_userns);
3944 /* Pairs with smp_load_acquire() in mnt_user_ns(). */
3945 smp_store_release(&mnt->mnt.mnt_userns, mnt_userns);
3946}
3947
3948static void mount_setattr_commit(struct mount_kattr *kattr,
3949 struct mount *mnt, struct mount *last,
3950 int err)
3951{
3952 struct mount *m = mnt;
3953
3954 do {
3955 if (!err) {
3956 unsigned int flags;
3957
3958 do_idmap_mount(kattr, m);
3959 flags = recalc_flags(kattr, m);
3960 WRITE_ONCE(m->mnt.mnt_flags, flags);
3961 }
3962
3963 /*
3964 * We either set MNT_READONLY above so make it visible
3965 * before ~MNT_WRITE_HOLD or we failed to recursively
3966 * apply mount options.
3967 */
3968 if ((kattr->attr_set & MNT_READONLY) &&
3969 (m->mnt.mnt_flags & MNT_WRITE_HOLD))
3970 mnt_unhold_writers(m);
3971
3972 if (!err && kattr->propagation)
3973 change_mnt_propagation(m, kattr->propagation);
3974
3975 /*
3976 * On failure, only cleanup until we found the first mount
3977 * we failed to handle.
3978 */
3979 if (err && m == last)
3980 break;
3981 } while (kattr->recurse && (m = next_mnt(m, mnt)));
3982
3983 if (!err)
3984 touch_mnt_namespace(mnt->mnt_ns);
3985}
3986
3987static int do_mount_setattr(struct path *path, struct mount_kattr *kattr)
3988{
3989 struct mount *mnt = real_mount(path->mnt), *last = NULL;
3990 int err = 0;
3991
3992 if (path->dentry != mnt->mnt.mnt_root)
3993 return -EINVAL;
3994
3995 if (kattr->propagation) {
3996 /*
3997 * Only take namespace_lock() if we're actually changing
3998 * propagation.
3999 */
4000 namespace_lock();
4001 if (kattr->propagation == MS_SHARED) {
4002 err = invent_group_ids(mnt, kattr->recurse);
4003 if (err) {
4004 namespace_unlock();
4005 return err;
4006 }
4007 }
4008 }
4009
4010 lock_mount_hash();
4011
4012 /*
4013 * Get the mount tree in a shape where we can change mount
4014 * properties without failure.
4015 */
4016 last = mount_setattr_prepare(kattr, mnt, &err);
4017 if (last) /* Commit all changes or revert to the old state. */
4018 mount_setattr_commit(kattr, mnt, last, err);
4019
4020 unlock_mount_hash();
4021
4022 if (kattr->propagation) {
4023 namespace_unlock();
4024 if (err)
4025 cleanup_group_ids(mnt, NULL);
4026 }
4027
4028 return err;
4029}
4030
4031static int build_mount_idmapped(const struct mount_attr *attr, size_t usize,
4032 struct mount_kattr *kattr, unsigned int flags)
4033{
4034 int err = 0;
4035 struct ns_common *ns;
4036 struct user_namespace *mnt_userns;
4037 struct file *file;
4038
4039 if (!((attr->attr_set | attr->attr_clr) & MOUNT_ATTR_IDMAP))
4040 return 0;
4041
4042 /*
4043 * We currently do not support clearing an idmapped mount. If this ever
4044 * is a use-case we can revisit this but for now let's keep it simple
4045 * and not allow it.
4046 */
4047 if (attr->attr_clr & MOUNT_ATTR_IDMAP)
4048 return -EINVAL;
4049
4050 if (attr->userns_fd > INT_MAX)
4051 return -EINVAL;
4052
4053 file = fget(attr->userns_fd);
4054 if (!file)
4055 return -EBADF;
4056
4057 if (!proc_ns_file(file)) {
4058 err = -EINVAL;
4059 goto out_fput;
4060 }
4061
4062 ns = get_proc_ns(file_inode(file));
4063 if (ns->ops->type != CLONE_NEWUSER) {
4064 err = -EINVAL;
4065 goto out_fput;
4066 }
4067
4068 /*
4069 * The init_user_ns is used to indicate that a vfsmount is not idmapped.
4070 * This is simpler than just having to treat NULL as unmapped. Users
4071 * wanting to idmap a mount to init_user_ns can just use a namespace
4072 * with an identity mapping.
4073 */
4074 mnt_userns = container_of(ns, struct user_namespace, ns);
4075 if (mnt_userns == &init_user_ns) {
4076 err = -EPERM;
4077 goto out_fput;
4078 }
4079 kattr->mnt_userns = get_user_ns(mnt_userns);
4080
4081out_fput:
4082 fput(file);
4083 return err;
4084}
4085
4086static int build_mount_kattr(const struct mount_attr *attr, size_t usize,
4087 struct mount_kattr *kattr, unsigned int flags)
4088{
4089 unsigned int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW;
4090
4091 if (flags & AT_NO_AUTOMOUNT)
4092 lookup_flags &= ~LOOKUP_AUTOMOUNT;
4093 if (flags & AT_SYMLINK_NOFOLLOW)
4094 lookup_flags &= ~LOOKUP_FOLLOW;
4095 if (flags & AT_EMPTY_PATH)
4096 lookup_flags |= LOOKUP_EMPTY;
4097
4098 *kattr = (struct mount_kattr) {
4099 .lookup_flags = lookup_flags,
4100 .recurse = !!(flags & AT_RECURSIVE),
4101 };
4102
4103 if (attr->propagation & ~MOUNT_SETATTR_PROPAGATION_FLAGS)
4104 return -EINVAL;
4105 if (hweight32(attr->propagation & MOUNT_SETATTR_PROPAGATION_FLAGS) > 1)
4106 return -EINVAL;
4107 kattr->propagation = attr->propagation;
4108
4109 if ((attr->attr_set | attr->attr_clr) & ~MOUNT_SETATTR_VALID_FLAGS)
4110 return -EINVAL;
4111
4112 kattr->attr_set = attr_flags_to_mnt_flags(attr->attr_set);
4113 kattr->attr_clr = attr_flags_to_mnt_flags(attr->attr_clr);
4114
4115 /*
4116 * Since the MOUNT_ATTR_<atime> values are an enum, not a bitmap,
4117 * users wanting to transition to a different atime setting cannot
4118 * simply specify the atime setting in @attr_set, but must also
4119 * specify MOUNT_ATTR__ATIME in the @attr_clr field.
4120 * So ensure that MOUNT_ATTR__ATIME can't be partially set in
4121 * @attr_clr and that @attr_set can't have any atime bits set if
4122 * MOUNT_ATTR__ATIME isn't set in @attr_clr.
4123 */
4124 if (attr->attr_clr & MOUNT_ATTR__ATIME) {
4125 if ((attr->attr_clr & MOUNT_ATTR__ATIME) != MOUNT_ATTR__ATIME)
4126 return -EINVAL;
4127
4128 /*
4129 * Clear all previous time settings as they are mutually
4130 * exclusive.
4131 */
4132 kattr->attr_clr |= MNT_RELATIME | MNT_NOATIME;
4133 switch (attr->attr_set & MOUNT_ATTR__ATIME) {
4134 case MOUNT_ATTR_RELATIME:
4135 kattr->attr_set |= MNT_RELATIME;
4136 break;
4137 case MOUNT_ATTR_NOATIME:
4138 kattr->attr_set |= MNT_NOATIME;
4139 break;
4140 case MOUNT_ATTR_STRICTATIME:
4141 break;
4142 default:
4143 return -EINVAL;
4144 }
4145 } else {
4146 if (attr->attr_set & MOUNT_ATTR__ATIME)
4147 return -EINVAL;
4148 }
4149
4150 return build_mount_idmapped(attr, usize, kattr, flags);
4151}
4152
4153static void finish_mount_kattr(struct mount_kattr *kattr)
4154{
4155 put_user_ns(kattr->mnt_userns);
4156 kattr->mnt_userns = NULL;
4157}
4158
4159SYSCALL_DEFINE5(mount_setattr, int, dfd, const char __user *, path,
4160 unsigned int, flags, struct mount_attr __user *, uattr,
4161 size_t, usize)
4162{
4163 int err;
4164 struct path target;
4165 struct mount_attr attr;
4166 struct mount_kattr kattr;
4167
4168 BUILD_BUG_ON(sizeof(struct mount_attr) != MOUNT_ATTR_SIZE_VER0);
4169
4170 if (flags & ~(AT_EMPTY_PATH |
4171 AT_RECURSIVE |
4172 AT_SYMLINK_NOFOLLOW |
4173 AT_NO_AUTOMOUNT))
4174 return -EINVAL;
4175
4176 if (unlikely(usize > PAGE_SIZE))
4177 return -E2BIG;
4178 if (unlikely(usize < MOUNT_ATTR_SIZE_VER0))
4179 return -EINVAL;
4180
4181 if (!may_mount())
4182 return -EPERM;
4183
4184 err = copy_struct_from_user(&attr, sizeof(attr), uattr, usize);
4185 if (err)
4186 return err;
4187
4188 /* Don't bother walking through the mounts if this is a nop. */
4189 if (attr.attr_set == 0 &&
4190 attr.attr_clr == 0 &&
4191 attr.propagation == 0)
4192 return 0;
4193
4194 err = build_mount_kattr(&attr, usize, &kattr, flags);
4195 if (err)
4196 return err;
4197
4198 err = user_path_at(dfd, path, kattr.lookup_flags, &target);
4199 if (err)
4200 return err;
4201
4202 err = do_mount_setattr(&target, &kattr);
4203 finish_mount_kattr(&kattr);
4204 path_put(&target);
4205 return err;
4206}
4207
4208static void __init init_mount_tree(void)
4209{
4210 struct vfsmount *mnt;
4211 struct mount *m;
4212 struct mnt_namespace *ns;
4213 struct path root;
4214
4215 mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", NULL);
4216 if (IS_ERR(mnt))
4217 panic("Can't create rootfs");
4218
4219 ns = alloc_mnt_ns(&init_user_ns, false);
4220 if (IS_ERR(ns))
4221 panic("Can't allocate initial namespace");
4222 m = real_mount(mnt);
4223 m->mnt_ns = ns;
4224 ns->root = m;
4225 ns->mounts = 1;
4226 list_add(&m->mnt_list, &ns->list);
4227 init_task.nsproxy->mnt_ns = ns;
4228 get_mnt_ns(ns);
4229
4230 root.mnt = mnt;
4231 root.dentry = mnt->mnt_root;
4232 mnt->mnt_flags |= MNT_LOCKED;
4233
4234 set_fs_pwd(current->fs, &root);
4235 set_fs_root(current->fs, &root);
4236}
4237
4238void __init mnt_init(void)
4239{
4240 int err;
4241
4242 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
4243 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
4244
4245 mount_hashtable = alloc_large_system_hash("Mount-cache",
4246 sizeof(struct hlist_head),
4247 mhash_entries, 19,
4248 HASH_ZERO,
4249 &m_hash_shift, &m_hash_mask, 0, 0);
4250 mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache",
4251 sizeof(struct hlist_head),
4252 mphash_entries, 19,
4253 HASH_ZERO,
4254 &mp_hash_shift, &mp_hash_mask, 0, 0);
4255
4256 if (!mount_hashtable || !mountpoint_hashtable)
4257 panic("Failed to allocate mount hash table\n");
4258
4259 kernfs_init();
4260
4261 err = sysfs_init();
4262 if (err)
4263 printk(KERN_WARNING "%s: sysfs_init error: %d\n",
4264 __func__, err);
4265 fs_kobj = kobject_create_and_add("fs", NULL);
4266 if (!fs_kobj)
4267 printk(KERN_WARNING "%s: kobj create error\n", __func__);
4268 shmem_init();
4269 init_rootfs();
4270 init_mount_tree();
4271}
4272
4273void put_mnt_ns(struct mnt_namespace *ns)
4274{
4275 if (!refcount_dec_and_test(&ns->ns.count))
4276 return;
4277 drop_collected_mounts(&ns->root->mnt);
4278 free_mnt_ns(ns);
4279}
4280
4281struct vfsmount *kern_mount(struct file_system_type *type)
4282{
4283 struct vfsmount *mnt;
4284 mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
4285 if (!IS_ERR(mnt)) {
4286 /*
4287 * it is a longterm mount, don't release mnt until
4288 * we unmount before file sys is unregistered
4289 */
4290 real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
4291 }
4292 return mnt;
4293}
4294EXPORT_SYMBOL_GPL(kern_mount);
4295
4296void kern_unmount(struct vfsmount *mnt)
4297{
4298 /* release long term mount so mount point can be released */
4299 if (!IS_ERR_OR_NULL(mnt)) {
4300 real_mount(mnt)->mnt_ns = NULL;
4301 synchronize_rcu(); /* yecchhh... */
4302 mntput(mnt);
4303 }
4304}
4305EXPORT_SYMBOL(kern_unmount);
4306
4307void kern_unmount_array(struct vfsmount *mnt[], unsigned int num)
4308{
4309 unsigned int i;
4310
4311 for (i = 0; i < num; i++)
4312 if (mnt[i])
4313 real_mount(mnt[i])->mnt_ns = NULL;
4314 synchronize_rcu_expedited();
4315 for (i = 0; i < num; i++)
4316 mntput(mnt[i]);
4317}
4318EXPORT_SYMBOL(kern_unmount_array);
4319
4320bool our_mnt(struct vfsmount *mnt)
4321{
4322 return check_mnt(real_mount(mnt));
4323}
4324
4325bool current_chrooted(void)
4326{
4327 /* Does the current process have a non-standard root */
4328 struct path ns_root;
4329 struct path fs_root;
4330 bool chrooted;
4331
4332 /* Find the namespace root */
4333 ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt;
4334 ns_root.dentry = ns_root.mnt->mnt_root;
4335 path_get(&ns_root);
4336 while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root))
4337 ;
4338
4339 get_fs_root(current->fs, &fs_root);
4340
4341 chrooted = !path_equal(&fs_root, &ns_root);
4342
4343 path_put(&fs_root);
4344 path_put(&ns_root);
4345
4346 return chrooted;
4347}
4348
4349static bool mnt_already_visible(struct mnt_namespace *ns,
4350 const struct super_block *sb,
4351 int *new_mnt_flags)
4352{
4353 int new_flags = *new_mnt_flags;
4354 struct mount *mnt;
4355 bool visible = false;
4356
4357 down_read(&namespace_sem);
4358 lock_ns_list(ns);
4359 list_for_each_entry(mnt, &ns->list, mnt_list) {
4360 struct mount *child;
4361 int mnt_flags;
4362
4363 if (mnt_is_cursor(mnt))
4364 continue;
4365
4366 if (mnt->mnt.mnt_sb->s_type != sb->s_type)
4367 continue;
4368
4369 /* This mount is not fully visible if it's root directory
4370 * is not the root directory of the filesystem.
4371 */
4372 if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root)
4373 continue;
4374
4375 /* A local view of the mount flags */
4376 mnt_flags = mnt->mnt.mnt_flags;
4377
4378 /* Don't miss readonly hidden in the superblock flags */
4379 if (sb_rdonly(mnt->mnt.mnt_sb))
4380 mnt_flags |= MNT_LOCK_READONLY;
4381
4382 /* Verify the mount flags are equal to or more permissive
4383 * than the proposed new mount.
4384 */
4385 if ((mnt_flags & MNT_LOCK_READONLY) &&
4386 !(new_flags & MNT_READONLY))
4387 continue;
4388 if ((mnt_flags & MNT_LOCK_ATIME) &&
4389 ((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK)))
4390 continue;
4391
4392 /* This mount is not fully visible if there are any
4393 * locked child mounts that cover anything except for
4394 * empty directories.
4395 */
4396 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
4397 struct inode *inode = child->mnt_mountpoint->d_inode;
4398 /* Only worry about locked mounts */
4399 if (!(child->mnt.mnt_flags & MNT_LOCKED))
4400 continue;
4401 /* Is the directory permanetly empty? */
4402 if (!is_empty_dir_inode(inode))
4403 goto next;
4404 }
4405 /* Preserve the locked attributes */
4406 *new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \
4407 MNT_LOCK_ATIME);
4408 visible = true;
4409 goto found;
4410 next: ;
4411 }
4412found:
4413 unlock_ns_list(ns);
4414 up_read(&namespace_sem);
4415 return visible;
4416}
4417
4418static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags)
4419{
4420 const unsigned long required_iflags = SB_I_NOEXEC | SB_I_NODEV;
4421 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
4422 unsigned long s_iflags;
4423
4424 if (ns->user_ns == &init_user_ns)
4425 return false;
4426
4427 /* Can this filesystem be too revealing? */
4428 s_iflags = sb->s_iflags;
4429 if (!(s_iflags & SB_I_USERNS_VISIBLE))
4430 return false;
4431
4432 if ((s_iflags & required_iflags) != required_iflags) {
4433 WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n",
4434 required_iflags);
4435 return true;
4436 }
4437
4438 return !mnt_already_visible(ns, sb, new_mnt_flags);
4439}
4440
4441bool mnt_may_suid(struct vfsmount *mnt)
4442{
4443 /*
4444 * Foreign mounts (accessed via fchdir or through /proc
4445 * symlinks) are always treated as if they are nosuid. This
4446 * prevents namespaces from trusting potentially unsafe
4447 * suid/sgid bits, file caps, or security labels that originate
4448 * in other namespaces.
4449 */
4450 return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) &&
4451 current_in_userns(mnt->mnt_sb->s_user_ns);
4452}
4453
4454static struct ns_common *mntns_get(struct task_struct *task)
4455{
4456 struct ns_common *ns = NULL;
4457 struct nsproxy *nsproxy;
4458
4459 task_lock(task);
4460 nsproxy = task->nsproxy;
4461 if (nsproxy) {
4462 ns = &nsproxy->mnt_ns->ns;
4463 get_mnt_ns(to_mnt_ns(ns));
4464 }
4465 task_unlock(task);
4466
4467 return ns;
4468}
4469
4470static void mntns_put(struct ns_common *ns)
4471{
4472 put_mnt_ns(to_mnt_ns(ns));
4473}
4474
4475static int mntns_install(struct nsset *nsset, struct ns_common *ns)
4476{
4477 struct nsproxy *nsproxy = nsset->nsproxy;
4478 struct fs_struct *fs = nsset->fs;
4479 struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns;
4480 struct user_namespace *user_ns = nsset->cred->user_ns;
4481 struct path root;
4482 int err;
4483
4484 if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
4485 !ns_capable(user_ns, CAP_SYS_CHROOT) ||
4486 !ns_capable(user_ns, CAP_SYS_ADMIN))
4487 return -EPERM;
4488
4489 if (is_anon_ns(mnt_ns))
4490 return -EINVAL;
4491
4492 if (fs->users != 1)
4493 return -EINVAL;
4494
4495 get_mnt_ns(mnt_ns);
4496 old_mnt_ns = nsproxy->mnt_ns;
4497 nsproxy->mnt_ns = mnt_ns;
4498
4499 /* Find the root */
4500 err = vfs_path_lookup(mnt_ns->root->mnt.mnt_root, &mnt_ns->root->mnt,
4501 "/", LOOKUP_DOWN, &root);
4502 if (err) {
4503 /* revert to old namespace */
4504 nsproxy->mnt_ns = old_mnt_ns;
4505 put_mnt_ns(mnt_ns);
4506 return err;
4507 }
4508
4509 put_mnt_ns(old_mnt_ns);
4510
4511 /* Update the pwd and root */
4512 set_fs_pwd(fs, &root);
4513 set_fs_root(fs, &root);
4514
4515 path_put(&root);
4516 return 0;
4517}
4518
4519static struct user_namespace *mntns_owner(struct ns_common *ns)
4520{
4521 return to_mnt_ns(ns)->user_ns;
4522}
4523
4524const struct proc_ns_operations mntns_operations = {
4525 .name = "mnt",
4526 .type = CLONE_NEWNS,
4527 .get = mntns_get,
4528 .put = mntns_put,
4529 .install = mntns_install,
4530 .owner = mntns_owner,
4531};
1/*
2 * linux/fs/namespace.c
3 *
4 * (C) Copyright Al Viro 2000, 2001
5 * Released under GPL v2.
6 *
7 * Based on code from fs/super.c, copyright Linus Torvalds and others.
8 * Heavily rewritten.
9 */
10
11#include <linux/syscalls.h>
12#include <linux/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/idr.h>
19#include <linux/acct.h> /* acct_auto_close_mnt */
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/uaccess.h>
24#include <linux/proc_ns.h>
25#include <linux/magic.h>
26#include <linux/bootmem.h>
27#include "pnode.h"
28#include "internal.h"
29
30static unsigned int m_hash_mask __read_mostly;
31static unsigned int m_hash_shift __read_mostly;
32static unsigned int mp_hash_mask __read_mostly;
33static unsigned int mp_hash_shift __read_mostly;
34
35static __initdata unsigned long mhash_entries;
36static int __init set_mhash_entries(char *str)
37{
38 if (!str)
39 return 0;
40 mhash_entries = simple_strtoul(str, &str, 0);
41 return 1;
42}
43__setup("mhash_entries=", set_mhash_entries);
44
45static __initdata unsigned long mphash_entries;
46static int __init set_mphash_entries(char *str)
47{
48 if (!str)
49 return 0;
50 mphash_entries = simple_strtoul(str, &str, 0);
51 return 1;
52}
53__setup("mphash_entries=", set_mphash_entries);
54
55static u64 event;
56static DEFINE_IDA(mnt_id_ida);
57static DEFINE_IDA(mnt_group_ida);
58static DEFINE_SPINLOCK(mnt_id_lock);
59static int mnt_id_start = 0;
60static int mnt_group_start = 1;
61
62static struct hlist_head *mount_hashtable __read_mostly;
63static struct hlist_head *mountpoint_hashtable __read_mostly;
64static struct kmem_cache *mnt_cache __read_mostly;
65static DECLARE_RWSEM(namespace_sem);
66
67/* /sys/fs */
68struct kobject *fs_kobj;
69EXPORT_SYMBOL_GPL(fs_kobj);
70
71/*
72 * vfsmount lock may be taken for read to prevent changes to the
73 * vfsmount hash, ie. during mountpoint lookups or walking back
74 * up the tree.
75 *
76 * It should be taken for write in all cases where the vfsmount
77 * tree or hash is modified or when a vfsmount structure is modified.
78 */
79__cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock);
80
81static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry)
82{
83 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
84 tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
85 tmp = tmp + (tmp >> m_hash_shift);
86 return &mount_hashtable[tmp & m_hash_mask];
87}
88
89static inline struct hlist_head *mp_hash(struct dentry *dentry)
90{
91 unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES);
92 tmp = tmp + (tmp >> mp_hash_shift);
93 return &mountpoint_hashtable[tmp & mp_hash_mask];
94}
95
96/*
97 * allocation is serialized by namespace_sem, but we need the spinlock to
98 * serialize with freeing.
99 */
100static int mnt_alloc_id(struct mount *mnt)
101{
102 int res;
103
104retry:
105 ida_pre_get(&mnt_id_ida, GFP_KERNEL);
106 spin_lock(&mnt_id_lock);
107 res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id);
108 if (!res)
109 mnt_id_start = mnt->mnt_id + 1;
110 spin_unlock(&mnt_id_lock);
111 if (res == -EAGAIN)
112 goto retry;
113
114 return res;
115}
116
117static void mnt_free_id(struct mount *mnt)
118{
119 int id = mnt->mnt_id;
120 spin_lock(&mnt_id_lock);
121 ida_remove(&mnt_id_ida, id);
122 if (mnt_id_start > id)
123 mnt_id_start = id;
124 spin_unlock(&mnt_id_lock);
125}
126
127/*
128 * Allocate a new peer group ID
129 *
130 * mnt_group_ida is protected by namespace_sem
131 */
132static int mnt_alloc_group_id(struct mount *mnt)
133{
134 int res;
135
136 if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
137 return -ENOMEM;
138
139 res = ida_get_new_above(&mnt_group_ida,
140 mnt_group_start,
141 &mnt->mnt_group_id);
142 if (!res)
143 mnt_group_start = mnt->mnt_group_id + 1;
144
145 return res;
146}
147
148/*
149 * Release a peer group ID
150 */
151void mnt_release_group_id(struct mount *mnt)
152{
153 int id = mnt->mnt_group_id;
154 ida_remove(&mnt_group_ida, id);
155 if (mnt_group_start > id)
156 mnt_group_start = id;
157 mnt->mnt_group_id = 0;
158}
159
160/*
161 * vfsmount lock must be held for read
162 */
163static inline void mnt_add_count(struct mount *mnt, int n)
164{
165#ifdef CONFIG_SMP
166 this_cpu_add(mnt->mnt_pcp->mnt_count, n);
167#else
168 preempt_disable();
169 mnt->mnt_count += n;
170 preempt_enable();
171#endif
172}
173
174/*
175 * vfsmount lock must be held for write
176 */
177unsigned int mnt_get_count(struct mount *mnt)
178{
179#ifdef CONFIG_SMP
180 unsigned int count = 0;
181 int cpu;
182
183 for_each_possible_cpu(cpu) {
184 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
185 }
186
187 return count;
188#else
189 return mnt->mnt_count;
190#endif
191}
192
193static struct mount *alloc_vfsmnt(const char *name)
194{
195 struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
196 if (mnt) {
197 int err;
198
199 err = mnt_alloc_id(mnt);
200 if (err)
201 goto out_free_cache;
202
203 if (name) {
204 mnt->mnt_devname = kstrdup(name, GFP_KERNEL);
205 if (!mnt->mnt_devname)
206 goto out_free_id;
207 }
208
209#ifdef CONFIG_SMP
210 mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
211 if (!mnt->mnt_pcp)
212 goto out_free_devname;
213
214 this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
215#else
216 mnt->mnt_count = 1;
217 mnt->mnt_writers = 0;
218#endif
219
220 INIT_HLIST_NODE(&mnt->mnt_hash);
221 INIT_LIST_HEAD(&mnt->mnt_child);
222 INIT_LIST_HEAD(&mnt->mnt_mounts);
223 INIT_LIST_HEAD(&mnt->mnt_list);
224 INIT_LIST_HEAD(&mnt->mnt_expire);
225 INIT_LIST_HEAD(&mnt->mnt_share);
226 INIT_LIST_HEAD(&mnt->mnt_slave_list);
227 INIT_LIST_HEAD(&mnt->mnt_slave);
228#ifdef CONFIG_FSNOTIFY
229 INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);
230#endif
231 }
232 return mnt;
233
234#ifdef CONFIG_SMP
235out_free_devname:
236 kfree(mnt->mnt_devname);
237#endif
238out_free_id:
239 mnt_free_id(mnt);
240out_free_cache:
241 kmem_cache_free(mnt_cache, mnt);
242 return NULL;
243}
244
245/*
246 * Most r/o checks on a fs are for operations that take
247 * discrete amounts of time, like a write() or unlink().
248 * We must keep track of when those operations start
249 * (for permission checks) and when they end, so that
250 * we can determine when writes are able to occur to
251 * a filesystem.
252 */
253/*
254 * __mnt_is_readonly: check whether a mount is read-only
255 * @mnt: the mount to check for its write status
256 *
257 * This shouldn't be used directly ouside of the VFS.
258 * It does not guarantee that the filesystem will stay
259 * r/w, just that it is right *now*. This can not and
260 * should not be used in place of IS_RDONLY(inode).
261 * mnt_want/drop_write() will _keep_ the filesystem
262 * r/w.
263 */
264int __mnt_is_readonly(struct vfsmount *mnt)
265{
266 if (mnt->mnt_flags & MNT_READONLY)
267 return 1;
268 if (mnt->mnt_sb->s_flags & MS_RDONLY)
269 return 1;
270 return 0;
271}
272EXPORT_SYMBOL_GPL(__mnt_is_readonly);
273
274static inline void mnt_inc_writers(struct mount *mnt)
275{
276#ifdef CONFIG_SMP
277 this_cpu_inc(mnt->mnt_pcp->mnt_writers);
278#else
279 mnt->mnt_writers++;
280#endif
281}
282
283static inline void mnt_dec_writers(struct mount *mnt)
284{
285#ifdef CONFIG_SMP
286 this_cpu_dec(mnt->mnt_pcp->mnt_writers);
287#else
288 mnt->mnt_writers--;
289#endif
290}
291
292static unsigned int mnt_get_writers(struct mount *mnt)
293{
294#ifdef CONFIG_SMP
295 unsigned int count = 0;
296 int cpu;
297
298 for_each_possible_cpu(cpu) {
299 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
300 }
301
302 return count;
303#else
304 return mnt->mnt_writers;
305#endif
306}
307
308static int mnt_is_readonly(struct vfsmount *mnt)
309{
310 if (mnt->mnt_sb->s_readonly_remount)
311 return 1;
312 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
313 smp_rmb();
314 return __mnt_is_readonly(mnt);
315}
316
317/*
318 * Most r/o & frozen checks on a fs are for operations that take discrete
319 * amounts of time, like a write() or unlink(). We must keep track of when
320 * those operations start (for permission checks) and when they end, so that we
321 * can determine when writes are able to occur to a filesystem.
322 */
323/**
324 * __mnt_want_write - get write access to a mount without freeze protection
325 * @m: the mount on which to take a write
326 *
327 * This tells the low-level filesystem that a write is about to be performed to
328 * it, and makes sure that writes are allowed (mnt it read-write) before
329 * returning success. This operation does not protect against filesystem being
330 * frozen. When the write operation is finished, __mnt_drop_write() must be
331 * called. This is effectively a refcount.
332 */
333int __mnt_want_write(struct vfsmount *m)
334{
335 struct mount *mnt = real_mount(m);
336 int ret = 0;
337
338 preempt_disable();
339 mnt_inc_writers(mnt);
340 /*
341 * The store to mnt_inc_writers must be visible before we pass
342 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
343 * incremented count after it has set MNT_WRITE_HOLD.
344 */
345 smp_mb();
346 while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
347 cpu_relax();
348 /*
349 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
350 * be set to match its requirements. So we must not load that until
351 * MNT_WRITE_HOLD is cleared.
352 */
353 smp_rmb();
354 if (mnt_is_readonly(m)) {
355 mnt_dec_writers(mnt);
356 ret = -EROFS;
357 }
358 preempt_enable();
359
360 return ret;
361}
362
363/**
364 * mnt_want_write - get write access to a mount
365 * @m: the mount on which to take a write
366 *
367 * This tells the low-level filesystem that a write is about to be performed to
368 * it, and makes sure that writes are allowed (mount is read-write, filesystem
369 * is not frozen) before returning success. When the write operation is
370 * finished, mnt_drop_write() must be called. This is effectively a refcount.
371 */
372int mnt_want_write(struct vfsmount *m)
373{
374 int ret;
375
376 sb_start_write(m->mnt_sb);
377 ret = __mnt_want_write(m);
378 if (ret)
379 sb_end_write(m->mnt_sb);
380 return ret;
381}
382EXPORT_SYMBOL_GPL(mnt_want_write);
383
384/**
385 * mnt_clone_write - get write access to a mount
386 * @mnt: the mount on which to take a write
387 *
388 * This is effectively like mnt_want_write, except
389 * it must only be used to take an extra write reference
390 * on a mountpoint that we already know has a write reference
391 * on it. This allows some optimisation.
392 *
393 * After finished, mnt_drop_write must be called as usual to
394 * drop the reference.
395 */
396int mnt_clone_write(struct vfsmount *mnt)
397{
398 /* superblock may be r/o */
399 if (__mnt_is_readonly(mnt))
400 return -EROFS;
401 preempt_disable();
402 mnt_inc_writers(real_mount(mnt));
403 preempt_enable();
404 return 0;
405}
406EXPORT_SYMBOL_GPL(mnt_clone_write);
407
408/**
409 * __mnt_want_write_file - get write access to a file's mount
410 * @file: the file who's mount on which to take a write
411 *
412 * This is like __mnt_want_write, but it takes a file and can
413 * do some optimisations if the file is open for write already
414 */
415int __mnt_want_write_file(struct file *file)
416{
417 if (!(file->f_mode & FMODE_WRITER))
418 return __mnt_want_write(file->f_path.mnt);
419 else
420 return mnt_clone_write(file->f_path.mnt);
421}
422
423/**
424 * mnt_want_write_file - get write access to a file's mount
425 * @file: the file who's mount on which to take a write
426 *
427 * This is like mnt_want_write, but it takes a file and can
428 * do some optimisations if the file is open for write already
429 */
430int mnt_want_write_file(struct file *file)
431{
432 int ret;
433
434 sb_start_write(file->f_path.mnt->mnt_sb);
435 ret = __mnt_want_write_file(file);
436 if (ret)
437 sb_end_write(file->f_path.mnt->mnt_sb);
438 return ret;
439}
440EXPORT_SYMBOL_GPL(mnt_want_write_file);
441
442/**
443 * __mnt_drop_write - give up write access to a mount
444 * @mnt: the mount on which to give up write access
445 *
446 * Tells the low-level filesystem that we are done
447 * performing writes to it. Must be matched with
448 * __mnt_want_write() call above.
449 */
450void __mnt_drop_write(struct vfsmount *mnt)
451{
452 preempt_disable();
453 mnt_dec_writers(real_mount(mnt));
454 preempt_enable();
455}
456
457/**
458 * mnt_drop_write - give up write access to a mount
459 * @mnt: the mount on which to give up write access
460 *
461 * Tells the low-level filesystem that we are done performing writes to it and
462 * also allows filesystem to be frozen again. Must be matched with
463 * mnt_want_write() call above.
464 */
465void mnt_drop_write(struct vfsmount *mnt)
466{
467 __mnt_drop_write(mnt);
468 sb_end_write(mnt->mnt_sb);
469}
470EXPORT_SYMBOL_GPL(mnt_drop_write);
471
472void __mnt_drop_write_file(struct file *file)
473{
474 __mnt_drop_write(file->f_path.mnt);
475}
476
477void mnt_drop_write_file(struct file *file)
478{
479 mnt_drop_write(file->f_path.mnt);
480}
481EXPORT_SYMBOL(mnt_drop_write_file);
482
483static int mnt_make_readonly(struct mount *mnt)
484{
485 int ret = 0;
486
487 lock_mount_hash();
488 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
489 /*
490 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
491 * should be visible before we do.
492 */
493 smp_mb();
494
495 /*
496 * With writers on hold, if this value is zero, then there are
497 * definitely no active writers (although held writers may subsequently
498 * increment the count, they'll have to wait, and decrement it after
499 * seeing MNT_READONLY).
500 *
501 * It is OK to have counter incremented on one CPU and decremented on
502 * another: the sum will add up correctly. The danger would be when we
503 * sum up each counter, if we read a counter before it is incremented,
504 * but then read another CPU's count which it has been subsequently
505 * decremented from -- we would see more decrements than we should.
506 * MNT_WRITE_HOLD protects against this scenario, because
507 * mnt_want_write first increments count, then smp_mb, then spins on
508 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
509 * we're counting up here.
510 */
511 if (mnt_get_writers(mnt) > 0)
512 ret = -EBUSY;
513 else
514 mnt->mnt.mnt_flags |= MNT_READONLY;
515 /*
516 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
517 * that become unheld will see MNT_READONLY.
518 */
519 smp_wmb();
520 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
521 unlock_mount_hash();
522 return ret;
523}
524
525static void __mnt_unmake_readonly(struct mount *mnt)
526{
527 lock_mount_hash();
528 mnt->mnt.mnt_flags &= ~MNT_READONLY;
529 unlock_mount_hash();
530}
531
532int sb_prepare_remount_readonly(struct super_block *sb)
533{
534 struct mount *mnt;
535 int err = 0;
536
537 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
538 if (atomic_long_read(&sb->s_remove_count))
539 return -EBUSY;
540
541 lock_mount_hash();
542 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
543 if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
544 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
545 smp_mb();
546 if (mnt_get_writers(mnt) > 0) {
547 err = -EBUSY;
548 break;
549 }
550 }
551 }
552 if (!err && atomic_long_read(&sb->s_remove_count))
553 err = -EBUSY;
554
555 if (!err) {
556 sb->s_readonly_remount = 1;
557 smp_wmb();
558 }
559 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
560 if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
561 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
562 }
563 unlock_mount_hash();
564
565 return err;
566}
567
568static void free_vfsmnt(struct mount *mnt)
569{
570 kfree(mnt->mnt_devname);
571#ifdef CONFIG_SMP
572 free_percpu(mnt->mnt_pcp);
573#endif
574 kmem_cache_free(mnt_cache, mnt);
575}
576
577static void delayed_free_vfsmnt(struct rcu_head *head)
578{
579 free_vfsmnt(container_of(head, struct mount, mnt_rcu));
580}
581
582/* call under rcu_read_lock */
583bool legitimize_mnt(struct vfsmount *bastard, unsigned seq)
584{
585 struct mount *mnt;
586 if (read_seqretry(&mount_lock, seq))
587 return false;
588 if (bastard == NULL)
589 return true;
590 mnt = real_mount(bastard);
591 mnt_add_count(mnt, 1);
592 if (likely(!read_seqretry(&mount_lock, seq)))
593 return true;
594 if (bastard->mnt_flags & MNT_SYNC_UMOUNT) {
595 mnt_add_count(mnt, -1);
596 return false;
597 }
598 rcu_read_unlock();
599 mntput(bastard);
600 rcu_read_lock();
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 * find the last mount at @dentry on vfsmount @mnt.
621 * mount_lock must be held.
622 */
623struct mount *__lookup_mnt_last(struct vfsmount *mnt, struct dentry *dentry)
624{
625 struct mount *p, *res;
626 res = p = __lookup_mnt(mnt, dentry);
627 if (!p)
628 goto out;
629 hlist_for_each_entry_continue(p, mnt_hash) {
630 if (&p->mnt_parent->mnt != mnt || p->mnt_mountpoint != dentry)
631 break;
632 res = p;
633 }
634out:
635 return res;
636}
637
638/*
639 * lookup_mnt - Return the first child mount mounted at path
640 *
641 * "First" means first mounted chronologically. If you create the
642 * following mounts:
643 *
644 * mount /dev/sda1 /mnt
645 * mount /dev/sda2 /mnt
646 * mount /dev/sda3 /mnt
647 *
648 * Then lookup_mnt() on the base /mnt dentry in the root mount will
649 * return successively the root dentry and vfsmount of /dev/sda1, then
650 * /dev/sda2, then /dev/sda3, then NULL.
651 *
652 * lookup_mnt takes a reference to the found vfsmount.
653 */
654struct vfsmount *lookup_mnt(struct path *path)
655{
656 struct mount *child_mnt;
657 struct vfsmount *m;
658 unsigned seq;
659
660 rcu_read_lock();
661 do {
662 seq = read_seqbegin(&mount_lock);
663 child_mnt = __lookup_mnt(path->mnt, path->dentry);
664 m = child_mnt ? &child_mnt->mnt : NULL;
665 } while (!legitimize_mnt(m, seq));
666 rcu_read_unlock();
667 return m;
668}
669
670static struct mountpoint *new_mountpoint(struct dentry *dentry)
671{
672 struct hlist_head *chain = mp_hash(dentry);
673 struct mountpoint *mp;
674 int ret;
675
676 hlist_for_each_entry(mp, chain, m_hash) {
677 if (mp->m_dentry == dentry) {
678 /* might be worth a WARN_ON() */
679 if (d_unlinked(dentry))
680 return ERR_PTR(-ENOENT);
681 mp->m_count++;
682 return mp;
683 }
684 }
685
686 mp = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
687 if (!mp)
688 return ERR_PTR(-ENOMEM);
689
690 ret = d_set_mounted(dentry);
691 if (ret) {
692 kfree(mp);
693 return ERR_PTR(ret);
694 }
695
696 mp->m_dentry = dentry;
697 mp->m_count = 1;
698 hlist_add_head(&mp->m_hash, chain);
699 return mp;
700}
701
702static void put_mountpoint(struct mountpoint *mp)
703{
704 if (!--mp->m_count) {
705 struct dentry *dentry = mp->m_dentry;
706 spin_lock(&dentry->d_lock);
707 dentry->d_flags &= ~DCACHE_MOUNTED;
708 spin_unlock(&dentry->d_lock);
709 hlist_del(&mp->m_hash);
710 kfree(mp);
711 }
712}
713
714static inline int check_mnt(struct mount *mnt)
715{
716 return mnt->mnt_ns == current->nsproxy->mnt_ns;
717}
718
719/*
720 * vfsmount lock must be held for write
721 */
722static void touch_mnt_namespace(struct mnt_namespace *ns)
723{
724 if (ns) {
725 ns->event = ++event;
726 wake_up_interruptible(&ns->poll);
727 }
728}
729
730/*
731 * vfsmount lock must be held for write
732 */
733static void __touch_mnt_namespace(struct mnt_namespace *ns)
734{
735 if (ns && ns->event != event) {
736 ns->event = event;
737 wake_up_interruptible(&ns->poll);
738 }
739}
740
741/*
742 * vfsmount lock must be held for write
743 */
744static void detach_mnt(struct mount *mnt, struct path *old_path)
745{
746 old_path->dentry = mnt->mnt_mountpoint;
747 old_path->mnt = &mnt->mnt_parent->mnt;
748 mnt->mnt_parent = mnt;
749 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
750 list_del_init(&mnt->mnt_child);
751 hlist_del_init_rcu(&mnt->mnt_hash);
752 put_mountpoint(mnt->mnt_mp);
753 mnt->mnt_mp = NULL;
754}
755
756/*
757 * vfsmount lock must be held for write
758 */
759void mnt_set_mountpoint(struct mount *mnt,
760 struct mountpoint *mp,
761 struct mount *child_mnt)
762{
763 mp->m_count++;
764 mnt_add_count(mnt, 1); /* essentially, that's mntget */
765 child_mnt->mnt_mountpoint = dget(mp->m_dentry);
766 child_mnt->mnt_parent = mnt;
767 child_mnt->mnt_mp = mp;
768}
769
770/*
771 * vfsmount lock must be held for write
772 */
773static void attach_mnt(struct mount *mnt,
774 struct mount *parent,
775 struct mountpoint *mp)
776{
777 mnt_set_mountpoint(parent, mp, mnt);
778 hlist_add_head_rcu(&mnt->mnt_hash, m_hash(&parent->mnt, mp->m_dentry));
779 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
780}
781
782/*
783 * vfsmount lock must be held for write
784 */
785static void commit_tree(struct mount *mnt, struct mount *shadows)
786{
787 struct mount *parent = mnt->mnt_parent;
788 struct mount *m;
789 LIST_HEAD(head);
790 struct mnt_namespace *n = parent->mnt_ns;
791
792 BUG_ON(parent == mnt);
793
794 list_add_tail(&head, &mnt->mnt_list);
795 list_for_each_entry(m, &head, mnt_list)
796 m->mnt_ns = n;
797
798 list_splice(&head, n->list.prev);
799
800 if (shadows)
801 hlist_add_after_rcu(&shadows->mnt_hash, &mnt->mnt_hash);
802 else
803 hlist_add_head_rcu(&mnt->mnt_hash,
804 m_hash(&parent->mnt, mnt->mnt_mountpoint));
805 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
806 touch_mnt_namespace(n);
807}
808
809static struct mount *next_mnt(struct mount *p, struct mount *root)
810{
811 struct list_head *next = p->mnt_mounts.next;
812 if (next == &p->mnt_mounts) {
813 while (1) {
814 if (p == root)
815 return NULL;
816 next = p->mnt_child.next;
817 if (next != &p->mnt_parent->mnt_mounts)
818 break;
819 p = p->mnt_parent;
820 }
821 }
822 return list_entry(next, struct mount, mnt_child);
823}
824
825static struct mount *skip_mnt_tree(struct mount *p)
826{
827 struct list_head *prev = p->mnt_mounts.prev;
828 while (prev != &p->mnt_mounts) {
829 p = list_entry(prev, struct mount, mnt_child);
830 prev = p->mnt_mounts.prev;
831 }
832 return p;
833}
834
835struct vfsmount *
836vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
837{
838 struct mount *mnt;
839 struct dentry *root;
840
841 if (!type)
842 return ERR_PTR(-ENODEV);
843
844 mnt = alloc_vfsmnt(name);
845 if (!mnt)
846 return ERR_PTR(-ENOMEM);
847
848 if (flags & MS_KERNMOUNT)
849 mnt->mnt.mnt_flags = MNT_INTERNAL;
850
851 root = mount_fs(type, flags, name, data);
852 if (IS_ERR(root)) {
853 mnt_free_id(mnt);
854 free_vfsmnt(mnt);
855 return ERR_CAST(root);
856 }
857
858 mnt->mnt.mnt_root = root;
859 mnt->mnt.mnt_sb = root->d_sb;
860 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
861 mnt->mnt_parent = mnt;
862 lock_mount_hash();
863 list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts);
864 unlock_mount_hash();
865 return &mnt->mnt;
866}
867EXPORT_SYMBOL_GPL(vfs_kern_mount);
868
869static struct mount *clone_mnt(struct mount *old, struct dentry *root,
870 int flag)
871{
872 struct super_block *sb = old->mnt.mnt_sb;
873 struct mount *mnt;
874 int err;
875
876 mnt = alloc_vfsmnt(old->mnt_devname);
877 if (!mnt)
878 return ERR_PTR(-ENOMEM);
879
880 if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
881 mnt->mnt_group_id = 0; /* not a peer of original */
882 else
883 mnt->mnt_group_id = old->mnt_group_id;
884
885 if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
886 err = mnt_alloc_group_id(mnt);
887 if (err)
888 goto out_free;
889 }
890
891 mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~(MNT_WRITE_HOLD|MNT_MARKED);
892 /* Don't allow unprivileged users to change mount flags */
893 if ((flag & CL_UNPRIVILEGED) && (mnt->mnt.mnt_flags & MNT_READONLY))
894 mnt->mnt.mnt_flags |= MNT_LOCK_READONLY;
895
896 /* Don't allow unprivileged users to reveal what is under a mount */
897 if ((flag & CL_UNPRIVILEGED) && list_empty(&old->mnt_expire))
898 mnt->mnt.mnt_flags |= MNT_LOCKED;
899
900 atomic_inc(&sb->s_active);
901 mnt->mnt.mnt_sb = sb;
902 mnt->mnt.mnt_root = dget(root);
903 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
904 mnt->mnt_parent = mnt;
905 lock_mount_hash();
906 list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
907 unlock_mount_hash();
908
909 if ((flag & CL_SLAVE) ||
910 ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
911 list_add(&mnt->mnt_slave, &old->mnt_slave_list);
912 mnt->mnt_master = old;
913 CLEAR_MNT_SHARED(mnt);
914 } else if (!(flag & CL_PRIVATE)) {
915 if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
916 list_add(&mnt->mnt_share, &old->mnt_share);
917 if (IS_MNT_SLAVE(old))
918 list_add(&mnt->mnt_slave, &old->mnt_slave);
919 mnt->mnt_master = old->mnt_master;
920 }
921 if (flag & CL_MAKE_SHARED)
922 set_mnt_shared(mnt);
923
924 /* stick the duplicate mount on the same expiry list
925 * as the original if that was on one */
926 if (flag & CL_EXPIRE) {
927 if (!list_empty(&old->mnt_expire))
928 list_add(&mnt->mnt_expire, &old->mnt_expire);
929 }
930
931 return mnt;
932
933 out_free:
934 mnt_free_id(mnt);
935 free_vfsmnt(mnt);
936 return ERR_PTR(err);
937}
938
939static void mntput_no_expire(struct mount *mnt)
940{
941put_again:
942 rcu_read_lock();
943 mnt_add_count(mnt, -1);
944 if (likely(mnt->mnt_ns)) { /* shouldn't be the last one */
945 rcu_read_unlock();
946 return;
947 }
948 lock_mount_hash();
949 if (mnt_get_count(mnt)) {
950 rcu_read_unlock();
951 unlock_mount_hash();
952 return;
953 }
954 if (unlikely(mnt->mnt_pinned)) {
955 mnt_add_count(mnt, mnt->mnt_pinned + 1);
956 mnt->mnt_pinned = 0;
957 rcu_read_unlock();
958 unlock_mount_hash();
959 acct_auto_close_mnt(&mnt->mnt);
960 goto put_again;
961 }
962 if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) {
963 rcu_read_unlock();
964 unlock_mount_hash();
965 return;
966 }
967 mnt->mnt.mnt_flags |= MNT_DOOMED;
968 rcu_read_unlock();
969
970 list_del(&mnt->mnt_instance);
971 unlock_mount_hash();
972
973 /*
974 * This probably indicates that somebody messed
975 * up a mnt_want/drop_write() pair. If this
976 * happens, the filesystem was probably unable
977 * to make r/w->r/o transitions.
978 */
979 /*
980 * The locking used to deal with mnt_count decrement provides barriers,
981 * so mnt_get_writers() below is safe.
982 */
983 WARN_ON(mnt_get_writers(mnt));
984 fsnotify_vfsmount_delete(&mnt->mnt);
985 dput(mnt->mnt.mnt_root);
986 deactivate_super(mnt->mnt.mnt_sb);
987 mnt_free_id(mnt);
988 call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt);
989}
990
991void mntput(struct vfsmount *mnt)
992{
993 if (mnt) {
994 struct mount *m = real_mount(mnt);
995 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
996 if (unlikely(m->mnt_expiry_mark))
997 m->mnt_expiry_mark = 0;
998 mntput_no_expire(m);
999 }
1000}
1001EXPORT_SYMBOL(mntput);
1002
1003struct vfsmount *mntget(struct vfsmount *mnt)
1004{
1005 if (mnt)
1006 mnt_add_count(real_mount(mnt), 1);
1007 return mnt;
1008}
1009EXPORT_SYMBOL(mntget);
1010
1011void mnt_pin(struct vfsmount *mnt)
1012{
1013 lock_mount_hash();
1014 real_mount(mnt)->mnt_pinned++;
1015 unlock_mount_hash();
1016}
1017EXPORT_SYMBOL(mnt_pin);
1018
1019void mnt_unpin(struct vfsmount *m)
1020{
1021 struct mount *mnt = real_mount(m);
1022 lock_mount_hash();
1023 if (mnt->mnt_pinned) {
1024 mnt_add_count(mnt, 1);
1025 mnt->mnt_pinned--;
1026 }
1027 unlock_mount_hash();
1028}
1029EXPORT_SYMBOL(mnt_unpin);
1030
1031static inline void mangle(struct seq_file *m, const char *s)
1032{
1033 seq_escape(m, s, " \t\n\\");
1034}
1035
1036/*
1037 * Simple .show_options callback for filesystems which don't want to
1038 * implement more complex mount option showing.
1039 *
1040 * See also save_mount_options().
1041 */
1042int generic_show_options(struct seq_file *m, struct dentry *root)
1043{
1044 const char *options;
1045
1046 rcu_read_lock();
1047 options = rcu_dereference(root->d_sb->s_options);
1048
1049 if (options != NULL && options[0]) {
1050 seq_putc(m, ',');
1051 mangle(m, options);
1052 }
1053 rcu_read_unlock();
1054
1055 return 0;
1056}
1057EXPORT_SYMBOL(generic_show_options);
1058
1059/*
1060 * If filesystem uses generic_show_options(), this function should be
1061 * called from the fill_super() callback.
1062 *
1063 * The .remount_fs callback usually needs to be handled in a special
1064 * way, to make sure, that previous options are not overwritten if the
1065 * remount fails.
1066 *
1067 * Also note, that if the filesystem's .remount_fs function doesn't
1068 * reset all options to their default value, but changes only newly
1069 * given options, then the displayed options will not reflect reality
1070 * any more.
1071 */
1072void save_mount_options(struct super_block *sb, char *options)
1073{
1074 BUG_ON(sb->s_options);
1075 rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL));
1076}
1077EXPORT_SYMBOL(save_mount_options);
1078
1079void replace_mount_options(struct super_block *sb, char *options)
1080{
1081 char *old = sb->s_options;
1082 rcu_assign_pointer(sb->s_options, options);
1083 if (old) {
1084 synchronize_rcu();
1085 kfree(old);
1086 }
1087}
1088EXPORT_SYMBOL(replace_mount_options);
1089
1090#ifdef CONFIG_PROC_FS
1091/* iterator; we want it to have access to namespace_sem, thus here... */
1092static void *m_start(struct seq_file *m, loff_t *pos)
1093{
1094 struct proc_mounts *p = proc_mounts(m);
1095
1096 down_read(&namespace_sem);
1097 if (p->cached_event == p->ns->event) {
1098 void *v = p->cached_mount;
1099 if (*pos == p->cached_index)
1100 return v;
1101 if (*pos == p->cached_index + 1) {
1102 v = seq_list_next(v, &p->ns->list, &p->cached_index);
1103 return p->cached_mount = v;
1104 }
1105 }
1106
1107 p->cached_event = p->ns->event;
1108 p->cached_mount = seq_list_start(&p->ns->list, *pos);
1109 p->cached_index = *pos;
1110 return p->cached_mount;
1111}
1112
1113static void *m_next(struct seq_file *m, void *v, loff_t *pos)
1114{
1115 struct proc_mounts *p = proc_mounts(m);
1116
1117 p->cached_mount = seq_list_next(v, &p->ns->list, pos);
1118 p->cached_index = *pos;
1119 return p->cached_mount;
1120}
1121
1122static void m_stop(struct seq_file *m, void *v)
1123{
1124 up_read(&namespace_sem);
1125}
1126
1127static int m_show(struct seq_file *m, void *v)
1128{
1129 struct proc_mounts *p = proc_mounts(m);
1130 struct mount *r = list_entry(v, struct mount, mnt_list);
1131 return p->show(m, &r->mnt);
1132}
1133
1134const struct seq_operations mounts_op = {
1135 .start = m_start,
1136 .next = m_next,
1137 .stop = m_stop,
1138 .show = m_show,
1139};
1140#endif /* CONFIG_PROC_FS */
1141
1142/**
1143 * may_umount_tree - check if a mount tree is busy
1144 * @mnt: root of mount tree
1145 *
1146 * This is called to check if a tree of mounts has any
1147 * open files, pwds, chroots or sub mounts that are
1148 * busy.
1149 */
1150int may_umount_tree(struct vfsmount *m)
1151{
1152 struct mount *mnt = real_mount(m);
1153 int actual_refs = 0;
1154 int minimum_refs = 0;
1155 struct mount *p;
1156 BUG_ON(!m);
1157
1158 /* write lock needed for mnt_get_count */
1159 lock_mount_hash();
1160 for (p = mnt; p; p = next_mnt(p, mnt)) {
1161 actual_refs += mnt_get_count(p);
1162 minimum_refs += 2;
1163 }
1164 unlock_mount_hash();
1165
1166 if (actual_refs > minimum_refs)
1167 return 0;
1168
1169 return 1;
1170}
1171
1172EXPORT_SYMBOL(may_umount_tree);
1173
1174/**
1175 * may_umount - check if a mount point is busy
1176 * @mnt: root of mount
1177 *
1178 * This is called to check if a mount point has any
1179 * open files, pwds, chroots or sub mounts. If the
1180 * mount has sub mounts this will return busy
1181 * regardless of whether the sub mounts are busy.
1182 *
1183 * Doesn't take quota and stuff into account. IOW, in some cases it will
1184 * give false negatives. The main reason why it's here is that we need
1185 * a non-destructive way to look for easily umountable filesystems.
1186 */
1187int may_umount(struct vfsmount *mnt)
1188{
1189 int ret = 1;
1190 down_read(&namespace_sem);
1191 lock_mount_hash();
1192 if (propagate_mount_busy(real_mount(mnt), 2))
1193 ret = 0;
1194 unlock_mount_hash();
1195 up_read(&namespace_sem);
1196 return ret;
1197}
1198
1199EXPORT_SYMBOL(may_umount);
1200
1201static HLIST_HEAD(unmounted); /* protected by namespace_sem */
1202
1203static void namespace_unlock(void)
1204{
1205 struct mount *mnt;
1206 struct hlist_head head = unmounted;
1207
1208 if (likely(hlist_empty(&head))) {
1209 up_write(&namespace_sem);
1210 return;
1211 }
1212
1213 head.first->pprev = &head.first;
1214 INIT_HLIST_HEAD(&unmounted);
1215
1216 up_write(&namespace_sem);
1217
1218 synchronize_rcu();
1219
1220 while (!hlist_empty(&head)) {
1221 mnt = hlist_entry(head.first, struct mount, mnt_hash);
1222 hlist_del_init(&mnt->mnt_hash);
1223 if (mnt->mnt_ex_mountpoint.mnt)
1224 path_put(&mnt->mnt_ex_mountpoint);
1225 mntput(&mnt->mnt);
1226 }
1227}
1228
1229static inline void namespace_lock(void)
1230{
1231 down_write(&namespace_sem);
1232}
1233
1234/*
1235 * mount_lock must be held
1236 * namespace_sem must be held for write
1237 * how = 0 => just this tree, don't propagate
1238 * how = 1 => propagate; we know that nobody else has reference to any victims
1239 * how = 2 => lazy umount
1240 */
1241void umount_tree(struct mount *mnt, int how)
1242{
1243 HLIST_HEAD(tmp_list);
1244 struct mount *p;
1245 struct mount *last = NULL;
1246
1247 for (p = mnt; p; p = next_mnt(p, mnt)) {
1248 hlist_del_init_rcu(&p->mnt_hash);
1249 hlist_add_head(&p->mnt_hash, &tmp_list);
1250 }
1251
1252 if (how)
1253 propagate_umount(&tmp_list);
1254
1255 hlist_for_each_entry(p, &tmp_list, mnt_hash) {
1256 list_del_init(&p->mnt_expire);
1257 list_del_init(&p->mnt_list);
1258 __touch_mnt_namespace(p->mnt_ns);
1259 p->mnt_ns = NULL;
1260 if (how < 2)
1261 p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
1262 list_del_init(&p->mnt_child);
1263 if (mnt_has_parent(p)) {
1264 put_mountpoint(p->mnt_mp);
1265 /* move the reference to mountpoint into ->mnt_ex_mountpoint */
1266 p->mnt_ex_mountpoint.dentry = p->mnt_mountpoint;
1267 p->mnt_ex_mountpoint.mnt = &p->mnt_parent->mnt;
1268 p->mnt_mountpoint = p->mnt.mnt_root;
1269 p->mnt_parent = p;
1270 p->mnt_mp = NULL;
1271 }
1272 change_mnt_propagation(p, MS_PRIVATE);
1273 last = p;
1274 }
1275 if (last) {
1276 last->mnt_hash.next = unmounted.first;
1277 unmounted.first = tmp_list.first;
1278 unmounted.first->pprev = &unmounted.first;
1279 }
1280}
1281
1282static void shrink_submounts(struct mount *mnt);
1283
1284static int do_umount(struct mount *mnt, int flags)
1285{
1286 struct super_block *sb = mnt->mnt.mnt_sb;
1287 int retval;
1288
1289 retval = security_sb_umount(&mnt->mnt, flags);
1290 if (retval)
1291 return retval;
1292
1293 /*
1294 * Allow userspace to request a mountpoint be expired rather than
1295 * unmounting unconditionally. Unmount only happens if:
1296 * (1) the mark is already set (the mark is cleared by mntput())
1297 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1298 */
1299 if (flags & MNT_EXPIRE) {
1300 if (&mnt->mnt == current->fs->root.mnt ||
1301 flags & (MNT_FORCE | MNT_DETACH))
1302 return -EINVAL;
1303
1304 /*
1305 * probably don't strictly need the lock here if we examined
1306 * all race cases, but it's a slowpath.
1307 */
1308 lock_mount_hash();
1309 if (mnt_get_count(mnt) != 2) {
1310 unlock_mount_hash();
1311 return -EBUSY;
1312 }
1313 unlock_mount_hash();
1314
1315 if (!xchg(&mnt->mnt_expiry_mark, 1))
1316 return -EAGAIN;
1317 }
1318
1319 /*
1320 * If we may have to abort operations to get out of this
1321 * mount, and they will themselves hold resources we must
1322 * allow the fs to do things. In the Unix tradition of
1323 * 'Gee thats tricky lets do it in userspace' the umount_begin
1324 * might fail to complete on the first run through as other tasks
1325 * must return, and the like. Thats for the mount program to worry
1326 * about for the moment.
1327 */
1328
1329 if (flags & MNT_FORCE && sb->s_op->umount_begin) {
1330 sb->s_op->umount_begin(sb);
1331 }
1332
1333 /*
1334 * No sense to grab the lock for this test, but test itself looks
1335 * somewhat bogus. Suggestions for better replacement?
1336 * Ho-hum... In principle, we might treat that as umount + switch
1337 * to rootfs. GC would eventually take care of the old vfsmount.
1338 * Actually it makes sense, especially if rootfs would contain a
1339 * /reboot - static binary that would close all descriptors and
1340 * call reboot(9). Then init(8) could umount root and exec /reboot.
1341 */
1342 if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
1343 /*
1344 * Special case for "unmounting" root ...
1345 * we just try to remount it readonly.
1346 */
1347 down_write(&sb->s_umount);
1348 if (!(sb->s_flags & MS_RDONLY))
1349 retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
1350 up_write(&sb->s_umount);
1351 return retval;
1352 }
1353
1354 namespace_lock();
1355 lock_mount_hash();
1356 event++;
1357
1358 if (flags & MNT_DETACH) {
1359 if (!list_empty(&mnt->mnt_list))
1360 umount_tree(mnt, 2);
1361 retval = 0;
1362 } else {
1363 shrink_submounts(mnt);
1364 retval = -EBUSY;
1365 if (!propagate_mount_busy(mnt, 2)) {
1366 if (!list_empty(&mnt->mnt_list))
1367 umount_tree(mnt, 1);
1368 retval = 0;
1369 }
1370 }
1371 unlock_mount_hash();
1372 namespace_unlock();
1373 return retval;
1374}
1375
1376/*
1377 * Is the caller allowed to modify his namespace?
1378 */
1379static inline bool may_mount(void)
1380{
1381 return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
1382}
1383
1384/*
1385 * Now umount can handle mount points as well as block devices.
1386 * This is important for filesystems which use unnamed block devices.
1387 *
1388 * We now support a flag for forced unmount like the other 'big iron'
1389 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1390 */
1391
1392SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1393{
1394 struct path path;
1395 struct mount *mnt;
1396 int retval;
1397 int lookup_flags = 0;
1398
1399 if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
1400 return -EINVAL;
1401
1402 if (!may_mount())
1403 return -EPERM;
1404
1405 if (!(flags & UMOUNT_NOFOLLOW))
1406 lookup_flags |= LOOKUP_FOLLOW;
1407
1408 retval = user_path_mountpoint_at(AT_FDCWD, name, lookup_flags, &path);
1409 if (retval)
1410 goto out;
1411 mnt = real_mount(path.mnt);
1412 retval = -EINVAL;
1413 if (path.dentry != path.mnt->mnt_root)
1414 goto dput_and_out;
1415 if (!check_mnt(mnt))
1416 goto dput_and_out;
1417 if (mnt->mnt.mnt_flags & MNT_LOCKED)
1418 goto dput_and_out;
1419
1420 retval = do_umount(mnt, flags);
1421dput_and_out:
1422 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1423 dput(path.dentry);
1424 mntput_no_expire(mnt);
1425out:
1426 return retval;
1427}
1428
1429#ifdef __ARCH_WANT_SYS_OLDUMOUNT
1430
1431/*
1432 * The 2.0 compatible umount. No flags.
1433 */
1434SYSCALL_DEFINE1(oldumount, char __user *, name)
1435{
1436 return sys_umount(name, 0);
1437}
1438
1439#endif
1440
1441static bool is_mnt_ns_file(struct dentry *dentry)
1442{
1443 /* Is this a proxy for a mount namespace? */
1444 struct inode *inode = dentry->d_inode;
1445 struct proc_ns *ei;
1446
1447 if (!proc_ns_inode(inode))
1448 return false;
1449
1450 ei = get_proc_ns(inode);
1451 if (ei->ns_ops != &mntns_operations)
1452 return false;
1453
1454 return true;
1455}
1456
1457static bool mnt_ns_loop(struct dentry *dentry)
1458{
1459 /* Could bind mounting the mount namespace inode cause a
1460 * mount namespace loop?
1461 */
1462 struct mnt_namespace *mnt_ns;
1463 if (!is_mnt_ns_file(dentry))
1464 return false;
1465
1466 mnt_ns = get_proc_ns(dentry->d_inode)->ns;
1467 return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
1468}
1469
1470struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
1471 int flag)
1472{
1473 struct mount *res, *p, *q, *r, *parent;
1474
1475 if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt))
1476 return ERR_PTR(-EINVAL);
1477
1478 if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
1479 return ERR_PTR(-EINVAL);
1480
1481 res = q = clone_mnt(mnt, dentry, flag);
1482 if (IS_ERR(q))
1483 return q;
1484
1485 q->mnt.mnt_flags &= ~MNT_LOCKED;
1486 q->mnt_mountpoint = mnt->mnt_mountpoint;
1487
1488 p = mnt;
1489 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
1490 struct mount *s;
1491 if (!is_subdir(r->mnt_mountpoint, dentry))
1492 continue;
1493
1494 for (s = r; s; s = next_mnt(s, r)) {
1495 if (!(flag & CL_COPY_UNBINDABLE) &&
1496 IS_MNT_UNBINDABLE(s)) {
1497 s = skip_mnt_tree(s);
1498 continue;
1499 }
1500 if (!(flag & CL_COPY_MNT_NS_FILE) &&
1501 is_mnt_ns_file(s->mnt.mnt_root)) {
1502 s = skip_mnt_tree(s);
1503 continue;
1504 }
1505 while (p != s->mnt_parent) {
1506 p = p->mnt_parent;
1507 q = q->mnt_parent;
1508 }
1509 p = s;
1510 parent = q;
1511 q = clone_mnt(p, p->mnt.mnt_root, flag);
1512 if (IS_ERR(q))
1513 goto out;
1514 lock_mount_hash();
1515 list_add_tail(&q->mnt_list, &res->mnt_list);
1516 attach_mnt(q, parent, p->mnt_mp);
1517 unlock_mount_hash();
1518 }
1519 }
1520 return res;
1521out:
1522 if (res) {
1523 lock_mount_hash();
1524 umount_tree(res, 0);
1525 unlock_mount_hash();
1526 }
1527 return q;
1528}
1529
1530/* Caller should check returned pointer for errors */
1531
1532struct vfsmount *collect_mounts(struct path *path)
1533{
1534 struct mount *tree;
1535 namespace_lock();
1536 tree = copy_tree(real_mount(path->mnt), path->dentry,
1537 CL_COPY_ALL | CL_PRIVATE);
1538 namespace_unlock();
1539 if (IS_ERR(tree))
1540 return ERR_CAST(tree);
1541 return &tree->mnt;
1542}
1543
1544void drop_collected_mounts(struct vfsmount *mnt)
1545{
1546 namespace_lock();
1547 lock_mount_hash();
1548 umount_tree(real_mount(mnt), 0);
1549 unlock_mount_hash();
1550 namespace_unlock();
1551}
1552
1553int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
1554 struct vfsmount *root)
1555{
1556 struct mount *mnt;
1557 int res = f(root, arg);
1558 if (res)
1559 return res;
1560 list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
1561 res = f(&mnt->mnt, arg);
1562 if (res)
1563 return res;
1564 }
1565 return 0;
1566}
1567
1568static void cleanup_group_ids(struct mount *mnt, struct mount *end)
1569{
1570 struct mount *p;
1571
1572 for (p = mnt; p != end; p = next_mnt(p, mnt)) {
1573 if (p->mnt_group_id && !IS_MNT_SHARED(p))
1574 mnt_release_group_id(p);
1575 }
1576}
1577
1578static int invent_group_ids(struct mount *mnt, bool recurse)
1579{
1580 struct mount *p;
1581
1582 for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
1583 if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
1584 int err = mnt_alloc_group_id(p);
1585 if (err) {
1586 cleanup_group_ids(mnt, p);
1587 return err;
1588 }
1589 }
1590 }
1591
1592 return 0;
1593}
1594
1595/*
1596 * @source_mnt : mount tree to be attached
1597 * @nd : place the mount tree @source_mnt is attached
1598 * @parent_nd : if non-null, detach the source_mnt from its parent and
1599 * store the parent mount and mountpoint dentry.
1600 * (done when source_mnt is moved)
1601 *
1602 * NOTE: in the table below explains the semantics when a source mount
1603 * of a given type is attached to a destination mount of a given type.
1604 * ---------------------------------------------------------------------------
1605 * | BIND MOUNT OPERATION |
1606 * |**************************************************************************
1607 * | source-->| shared | private | slave | unbindable |
1608 * | dest | | | | |
1609 * | | | | | | |
1610 * | v | | | | |
1611 * |**************************************************************************
1612 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1613 * | | | | | |
1614 * |non-shared| shared (+) | private | slave (*) | invalid |
1615 * ***************************************************************************
1616 * A bind operation clones the source mount and mounts the clone on the
1617 * destination mount.
1618 *
1619 * (++) the cloned mount is propagated to all the mounts in the propagation
1620 * tree of the destination mount and the cloned mount is added to
1621 * the peer group of the source mount.
1622 * (+) the cloned mount is created under the destination mount and is marked
1623 * as shared. The cloned mount is added to the peer group of the source
1624 * mount.
1625 * (+++) the mount is propagated to all the mounts in the propagation tree
1626 * of the destination mount and the cloned mount is made slave
1627 * of the same master as that of the source mount. The cloned mount
1628 * is marked as 'shared and slave'.
1629 * (*) the cloned mount is made a slave of the same master as that of the
1630 * source mount.
1631 *
1632 * ---------------------------------------------------------------------------
1633 * | MOVE MOUNT OPERATION |
1634 * |**************************************************************************
1635 * | source-->| shared | private | slave | unbindable |
1636 * | dest | | | | |
1637 * | | | | | | |
1638 * | v | | | | |
1639 * |**************************************************************************
1640 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1641 * | | | | | |
1642 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1643 * ***************************************************************************
1644 *
1645 * (+) the mount is moved to the destination. And is then propagated to
1646 * all the mounts in the propagation tree of the destination mount.
1647 * (+*) the mount is moved to the destination.
1648 * (+++) the mount is moved to the destination and is then propagated to
1649 * all the mounts belonging to the destination mount's propagation tree.
1650 * the mount is marked as 'shared and slave'.
1651 * (*) the mount continues to be a slave at the new location.
1652 *
1653 * if the source mount is a tree, the operations explained above is
1654 * applied to each mount in the tree.
1655 * Must be called without spinlocks held, since this function can sleep
1656 * in allocations.
1657 */
1658static int attach_recursive_mnt(struct mount *source_mnt,
1659 struct mount *dest_mnt,
1660 struct mountpoint *dest_mp,
1661 struct path *parent_path)
1662{
1663 HLIST_HEAD(tree_list);
1664 struct mount *child, *p;
1665 struct hlist_node *n;
1666 int err;
1667
1668 if (IS_MNT_SHARED(dest_mnt)) {
1669 err = invent_group_ids(source_mnt, true);
1670 if (err)
1671 goto out;
1672 err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
1673 lock_mount_hash();
1674 if (err)
1675 goto out_cleanup_ids;
1676 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
1677 set_mnt_shared(p);
1678 } else {
1679 lock_mount_hash();
1680 }
1681 if (parent_path) {
1682 detach_mnt(source_mnt, parent_path);
1683 attach_mnt(source_mnt, dest_mnt, dest_mp);
1684 touch_mnt_namespace(source_mnt->mnt_ns);
1685 } else {
1686 mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
1687 commit_tree(source_mnt, NULL);
1688 }
1689
1690 hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) {
1691 struct mount *q;
1692 hlist_del_init(&child->mnt_hash);
1693 q = __lookup_mnt_last(&child->mnt_parent->mnt,
1694 child->mnt_mountpoint);
1695 commit_tree(child, q);
1696 }
1697 unlock_mount_hash();
1698
1699 return 0;
1700
1701 out_cleanup_ids:
1702 while (!hlist_empty(&tree_list)) {
1703 child = hlist_entry(tree_list.first, struct mount, mnt_hash);
1704 umount_tree(child, 0);
1705 }
1706 unlock_mount_hash();
1707 cleanup_group_ids(source_mnt, NULL);
1708 out:
1709 return err;
1710}
1711
1712static struct mountpoint *lock_mount(struct path *path)
1713{
1714 struct vfsmount *mnt;
1715 struct dentry *dentry = path->dentry;
1716retry:
1717 mutex_lock(&dentry->d_inode->i_mutex);
1718 if (unlikely(cant_mount(dentry))) {
1719 mutex_unlock(&dentry->d_inode->i_mutex);
1720 return ERR_PTR(-ENOENT);
1721 }
1722 namespace_lock();
1723 mnt = lookup_mnt(path);
1724 if (likely(!mnt)) {
1725 struct mountpoint *mp = new_mountpoint(dentry);
1726 if (IS_ERR(mp)) {
1727 namespace_unlock();
1728 mutex_unlock(&dentry->d_inode->i_mutex);
1729 return mp;
1730 }
1731 return mp;
1732 }
1733 namespace_unlock();
1734 mutex_unlock(&path->dentry->d_inode->i_mutex);
1735 path_put(path);
1736 path->mnt = mnt;
1737 dentry = path->dentry = dget(mnt->mnt_root);
1738 goto retry;
1739}
1740
1741static void unlock_mount(struct mountpoint *where)
1742{
1743 struct dentry *dentry = where->m_dentry;
1744 put_mountpoint(where);
1745 namespace_unlock();
1746 mutex_unlock(&dentry->d_inode->i_mutex);
1747}
1748
1749static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
1750{
1751 if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER)
1752 return -EINVAL;
1753
1754 if (S_ISDIR(mp->m_dentry->d_inode->i_mode) !=
1755 S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode))
1756 return -ENOTDIR;
1757
1758 return attach_recursive_mnt(mnt, p, mp, NULL);
1759}
1760
1761/*
1762 * Sanity check the flags to change_mnt_propagation.
1763 */
1764
1765static int flags_to_propagation_type(int flags)
1766{
1767 int type = flags & ~(MS_REC | MS_SILENT);
1768
1769 /* Fail if any non-propagation flags are set */
1770 if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
1771 return 0;
1772 /* Only one propagation flag should be set */
1773 if (!is_power_of_2(type))
1774 return 0;
1775 return type;
1776}
1777
1778/*
1779 * recursively change the type of the mountpoint.
1780 */
1781static int do_change_type(struct path *path, int flag)
1782{
1783 struct mount *m;
1784 struct mount *mnt = real_mount(path->mnt);
1785 int recurse = flag & MS_REC;
1786 int type;
1787 int err = 0;
1788
1789 if (path->dentry != path->mnt->mnt_root)
1790 return -EINVAL;
1791
1792 type = flags_to_propagation_type(flag);
1793 if (!type)
1794 return -EINVAL;
1795
1796 namespace_lock();
1797 if (type == MS_SHARED) {
1798 err = invent_group_ids(mnt, recurse);
1799 if (err)
1800 goto out_unlock;
1801 }
1802
1803 lock_mount_hash();
1804 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
1805 change_mnt_propagation(m, type);
1806 unlock_mount_hash();
1807
1808 out_unlock:
1809 namespace_unlock();
1810 return err;
1811}
1812
1813static bool has_locked_children(struct mount *mnt, struct dentry *dentry)
1814{
1815 struct mount *child;
1816 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
1817 if (!is_subdir(child->mnt_mountpoint, dentry))
1818 continue;
1819
1820 if (child->mnt.mnt_flags & MNT_LOCKED)
1821 return true;
1822 }
1823 return false;
1824}
1825
1826/*
1827 * do loopback mount.
1828 */
1829static int do_loopback(struct path *path, const char *old_name,
1830 int recurse)
1831{
1832 struct path old_path;
1833 struct mount *mnt = NULL, *old, *parent;
1834 struct mountpoint *mp;
1835 int err;
1836 if (!old_name || !*old_name)
1837 return -EINVAL;
1838 err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
1839 if (err)
1840 return err;
1841
1842 err = -EINVAL;
1843 if (mnt_ns_loop(old_path.dentry))
1844 goto out;
1845
1846 mp = lock_mount(path);
1847 err = PTR_ERR(mp);
1848 if (IS_ERR(mp))
1849 goto out;
1850
1851 old = real_mount(old_path.mnt);
1852 parent = real_mount(path->mnt);
1853
1854 err = -EINVAL;
1855 if (IS_MNT_UNBINDABLE(old))
1856 goto out2;
1857
1858 if (!check_mnt(parent) || !check_mnt(old))
1859 goto out2;
1860
1861 if (!recurse && has_locked_children(old, old_path.dentry))
1862 goto out2;
1863
1864 if (recurse)
1865 mnt = copy_tree(old, old_path.dentry, CL_COPY_MNT_NS_FILE);
1866 else
1867 mnt = clone_mnt(old, old_path.dentry, 0);
1868
1869 if (IS_ERR(mnt)) {
1870 err = PTR_ERR(mnt);
1871 goto out2;
1872 }
1873
1874 mnt->mnt.mnt_flags &= ~MNT_LOCKED;
1875
1876 err = graft_tree(mnt, parent, mp);
1877 if (err) {
1878 lock_mount_hash();
1879 umount_tree(mnt, 0);
1880 unlock_mount_hash();
1881 }
1882out2:
1883 unlock_mount(mp);
1884out:
1885 path_put(&old_path);
1886 return err;
1887}
1888
1889static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
1890{
1891 int error = 0;
1892 int readonly_request = 0;
1893
1894 if (ms_flags & MS_RDONLY)
1895 readonly_request = 1;
1896 if (readonly_request == __mnt_is_readonly(mnt))
1897 return 0;
1898
1899 if (mnt->mnt_flags & MNT_LOCK_READONLY)
1900 return -EPERM;
1901
1902 if (readonly_request)
1903 error = mnt_make_readonly(real_mount(mnt));
1904 else
1905 __mnt_unmake_readonly(real_mount(mnt));
1906 return error;
1907}
1908
1909/*
1910 * change filesystem flags. dir should be a physical root of filesystem.
1911 * If you've mounted a non-root directory somewhere and want to do remount
1912 * on it - tough luck.
1913 */
1914static int do_remount(struct path *path, int flags, int mnt_flags,
1915 void *data)
1916{
1917 int err;
1918 struct super_block *sb = path->mnt->mnt_sb;
1919 struct mount *mnt = real_mount(path->mnt);
1920
1921 if (!check_mnt(mnt))
1922 return -EINVAL;
1923
1924 if (path->dentry != path->mnt->mnt_root)
1925 return -EINVAL;
1926
1927 err = security_sb_remount(sb, data);
1928 if (err)
1929 return err;
1930
1931 down_write(&sb->s_umount);
1932 if (flags & MS_BIND)
1933 err = change_mount_flags(path->mnt, flags);
1934 else if (!capable(CAP_SYS_ADMIN))
1935 err = -EPERM;
1936 else
1937 err = do_remount_sb(sb, flags, data, 0);
1938 if (!err) {
1939 lock_mount_hash();
1940 mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK;
1941 mnt->mnt.mnt_flags = mnt_flags;
1942 touch_mnt_namespace(mnt->mnt_ns);
1943 unlock_mount_hash();
1944 }
1945 up_write(&sb->s_umount);
1946 return err;
1947}
1948
1949static inline int tree_contains_unbindable(struct mount *mnt)
1950{
1951 struct mount *p;
1952 for (p = mnt; p; p = next_mnt(p, mnt)) {
1953 if (IS_MNT_UNBINDABLE(p))
1954 return 1;
1955 }
1956 return 0;
1957}
1958
1959static int do_move_mount(struct path *path, const char *old_name)
1960{
1961 struct path old_path, parent_path;
1962 struct mount *p;
1963 struct mount *old;
1964 struct mountpoint *mp;
1965 int err;
1966 if (!old_name || !*old_name)
1967 return -EINVAL;
1968 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
1969 if (err)
1970 return err;
1971
1972 mp = lock_mount(path);
1973 err = PTR_ERR(mp);
1974 if (IS_ERR(mp))
1975 goto out;
1976
1977 old = real_mount(old_path.mnt);
1978 p = real_mount(path->mnt);
1979
1980 err = -EINVAL;
1981 if (!check_mnt(p) || !check_mnt(old))
1982 goto out1;
1983
1984 if (old->mnt.mnt_flags & MNT_LOCKED)
1985 goto out1;
1986
1987 err = -EINVAL;
1988 if (old_path.dentry != old_path.mnt->mnt_root)
1989 goto out1;
1990
1991 if (!mnt_has_parent(old))
1992 goto out1;
1993
1994 if (S_ISDIR(path->dentry->d_inode->i_mode) !=
1995 S_ISDIR(old_path.dentry->d_inode->i_mode))
1996 goto out1;
1997 /*
1998 * Don't move a mount residing in a shared parent.
1999 */
2000 if (IS_MNT_SHARED(old->mnt_parent))
2001 goto out1;
2002 /*
2003 * Don't move a mount tree containing unbindable mounts to a destination
2004 * mount which is shared.
2005 */
2006 if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
2007 goto out1;
2008 err = -ELOOP;
2009 for (; mnt_has_parent(p); p = p->mnt_parent)
2010 if (p == old)
2011 goto out1;
2012
2013 err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path);
2014 if (err)
2015 goto out1;
2016
2017 /* if the mount is moved, it should no longer be expire
2018 * automatically */
2019 list_del_init(&old->mnt_expire);
2020out1:
2021 unlock_mount(mp);
2022out:
2023 if (!err)
2024 path_put(&parent_path);
2025 path_put(&old_path);
2026 return err;
2027}
2028
2029static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
2030{
2031 int err;
2032 const char *subtype = strchr(fstype, '.');
2033 if (subtype) {
2034 subtype++;
2035 err = -EINVAL;
2036 if (!subtype[0])
2037 goto err;
2038 } else
2039 subtype = "";
2040
2041 mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
2042 err = -ENOMEM;
2043 if (!mnt->mnt_sb->s_subtype)
2044 goto err;
2045 return mnt;
2046
2047 err:
2048 mntput(mnt);
2049 return ERR_PTR(err);
2050}
2051
2052/*
2053 * add a mount into a namespace's mount tree
2054 */
2055static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
2056{
2057 struct mountpoint *mp;
2058 struct mount *parent;
2059 int err;
2060
2061 mnt_flags &= ~MNT_INTERNAL_FLAGS;
2062
2063 mp = lock_mount(path);
2064 if (IS_ERR(mp))
2065 return PTR_ERR(mp);
2066
2067 parent = real_mount(path->mnt);
2068 err = -EINVAL;
2069 if (unlikely(!check_mnt(parent))) {
2070 /* that's acceptable only for automounts done in private ns */
2071 if (!(mnt_flags & MNT_SHRINKABLE))
2072 goto unlock;
2073 /* ... and for those we'd better have mountpoint still alive */
2074 if (!parent->mnt_ns)
2075 goto unlock;
2076 }
2077
2078 /* Refuse the same filesystem on the same mount point */
2079 err = -EBUSY;
2080 if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb &&
2081 path->mnt->mnt_root == path->dentry)
2082 goto unlock;
2083
2084 err = -EINVAL;
2085 if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode))
2086 goto unlock;
2087
2088 newmnt->mnt.mnt_flags = mnt_flags;
2089 err = graft_tree(newmnt, parent, mp);
2090
2091unlock:
2092 unlock_mount(mp);
2093 return err;
2094}
2095
2096/*
2097 * create a new mount for userspace and request it to be added into the
2098 * namespace's tree
2099 */
2100static int do_new_mount(struct path *path, const char *fstype, int flags,
2101 int mnt_flags, const char *name, void *data)
2102{
2103 struct file_system_type *type;
2104 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2105 struct vfsmount *mnt;
2106 int err;
2107
2108 if (!fstype)
2109 return -EINVAL;
2110
2111 type = get_fs_type(fstype);
2112 if (!type)
2113 return -ENODEV;
2114
2115 if (user_ns != &init_user_ns) {
2116 if (!(type->fs_flags & FS_USERNS_MOUNT)) {
2117 put_filesystem(type);
2118 return -EPERM;
2119 }
2120 /* Only in special cases allow devices from mounts
2121 * created outside the initial user namespace.
2122 */
2123 if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) {
2124 flags |= MS_NODEV;
2125 mnt_flags |= MNT_NODEV;
2126 }
2127 }
2128
2129 mnt = vfs_kern_mount(type, flags, name, data);
2130 if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
2131 !mnt->mnt_sb->s_subtype)
2132 mnt = fs_set_subtype(mnt, fstype);
2133
2134 put_filesystem(type);
2135 if (IS_ERR(mnt))
2136 return PTR_ERR(mnt);
2137
2138 err = do_add_mount(real_mount(mnt), path, mnt_flags);
2139 if (err)
2140 mntput(mnt);
2141 return err;
2142}
2143
2144int finish_automount(struct vfsmount *m, struct path *path)
2145{
2146 struct mount *mnt = real_mount(m);
2147 int err;
2148 /* The new mount record should have at least 2 refs to prevent it being
2149 * expired before we get a chance to add it
2150 */
2151 BUG_ON(mnt_get_count(mnt) < 2);
2152
2153 if (m->mnt_sb == path->mnt->mnt_sb &&
2154 m->mnt_root == path->dentry) {
2155 err = -ELOOP;
2156 goto fail;
2157 }
2158
2159 err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
2160 if (!err)
2161 return 0;
2162fail:
2163 /* remove m from any expiration list it may be on */
2164 if (!list_empty(&mnt->mnt_expire)) {
2165 namespace_lock();
2166 list_del_init(&mnt->mnt_expire);
2167 namespace_unlock();
2168 }
2169 mntput(m);
2170 mntput(m);
2171 return err;
2172}
2173
2174/**
2175 * mnt_set_expiry - Put a mount on an expiration list
2176 * @mnt: The mount to list.
2177 * @expiry_list: The list to add the mount to.
2178 */
2179void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
2180{
2181 namespace_lock();
2182
2183 list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
2184
2185 namespace_unlock();
2186}
2187EXPORT_SYMBOL(mnt_set_expiry);
2188
2189/*
2190 * process a list of expirable mountpoints with the intent of discarding any
2191 * mountpoints that aren't in use and haven't been touched since last we came
2192 * here
2193 */
2194void mark_mounts_for_expiry(struct list_head *mounts)
2195{
2196 struct mount *mnt, *next;
2197 LIST_HEAD(graveyard);
2198
2199 if (list_empty(mounts))
2200 return;
2201
2202 namespace_lock();
2203 lock_mount_hash();
2204
2205 /* extract from the expiration list every vfsmount that matches the
2206 * following criteria:
2207 * - only referenced by its parent vfsmount
2208 * - still marked for expiry (marked on the last call here; marks are
2209 * cleared by mntput())
2210 */
2211 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
2212 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
2213 propagate_mount_busy(mnt, 1))
2214 continue;
2215 list_move(&mnt->mnt_expire, &graveyard);
2216 }
2217 while (!list_empty(&graveyard)) {
2218 mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
2219 touch_mnt_namespace(mnt->mnt_ns);
2220 umount_tree(mnt, 1);
2221 }
2222 unlock_mount_hash();
2223 namespace_unlock();
2224}
2225
2226EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
2227
2228/*
2229 * Ripoff of 'select_parent()'
2230 *
2231 * search the list of submounts for a given mountpoint, and move any
2232 * shrinkable submounts to the 'graveyard' list.
2233 */
2234static int select_submounts(struct mount *parent, struct list_head *graveyard)
2235{
2236 struct mount *this_parent = parent;
2237 struct list_head *next;
2238 int found = 0;
2239
2240repeat:
2241 next = this_parent->mnt_mounts.next;
2242resume:
2243 while (next != &this_parent->mnt_mounts) {
2244 struct list_head *tmp = next;
2245 struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
2246
2247 next = tmp->next;
2248 if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
2249 continue;
2250 /*
2251 * Descend a level if the d_mounts list is non-empty.
2252 */
2253 if (!list_empty(&mnt->mnt_mounts)) {
2254 this_parent = mnt;
2255 goto repeat;
2256 }
2257
2258 if (!propagate_mount_busy(mnt, 1)) {
2259 list_move_tail(&mnt->mnt_expire, graveyard);
2260 found++;
2261 }
2262 }
2263 /*
2264 * All done at this level ... ascend and resume the search
2265 */
2266 if (this_parent != parent) {
2267 next = this_parent->mnt_child.next;
2268 this_parent = this_parent->mnt_parent;
2269 goto resume;
2270 }
2271 return found;
2272}
2273
2274/*
2275 * process a list of expirable mountpoints with the intent of discarding any
2276 * submounts of a specific parent mountpoint
2277 *
2278 * mount_lock must be held for write
2279 */
2280static void shrink_submounts(struct mount *mnt)
2281{
2282 LIST_HEAD(graveyard);
2283 struct mount *m;
2284
2285 /* extract submounts of 'mountpoint' from the expiration list */
2286 while (select_submounts(mnt, &graveyard)) {
2287 while (!list_empty(&graveyard)) {
2288 m = list_first_entry(&graveyard, struct mount,
2289 mnt_expire);
2290 touch_mnt_namespace(m->mnt_ns);
2291 umount_tree(m, 1);
2292 }
2293 }
2294}
2295
2296/*
2297 * Some copy_from_user() implementations do not return the exact number of
2298 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2299 * Note that this function differs from copy_from_user() in that it will oops
2300 * on bad values of `to', rather than returning a short copy.
2301 */
2302static long exact_copy_from_user(void *to, const void __user * from,
2303 unsigned long n)
2304{
2305 char *t = to;
2306 const char __user *f = from;
2307 char c;
2308
2309 if (!access_ok(VERIFY_READ, from, n))
2310 return n;
2311
2312 while (n) {
2313 if (__get_user(c, f)) {
2314 memset(t, 0, n);
2315 break;
2316 }
2317 *t++ = c;
2318 f++;
2319 n--;
2320 }
2321 return n;
2322}
2323
2324int copy_mount_options(const void __user * data, unsigned long *where)
2325{
2326 int i;
2327 unsigned long page;
2328 unsigned long size;
2329
2330 *where = 0;
2331 if (!data)
2332 return 0;
2333
2334 if (!(page = __get_free_page(GFP_KERNEL)))
2335 return -ENOMEM;
2336
2337 /* We only care that *some* data at the address the user
2338 * gave us is valid. Just in case, we'll zero
2339 * the remainder of the page.
2340 */
2341 /* copy_from_user cannot cross TASK_SIZE ! */
2342 size = TASK_SIZE - (unsigned long)data;
2343 if (size > PAGE_SIZE)
2344 size = PAGE_SIZE;
2345
2346 i = size - exact_copy_from_user((void *)page, data, size);
2347 if (!i) {
2348 free_page(page);
2349 return -EFAULT;
2350 }
2351 if (i != PAGE_SIZE)
2352 memset((char *)page + i, 0, PAGE_SIZE - i);
2353 *where = page;
2354 return 0;
2355}
2356
2357int copy_mount_string(const void __user *data, char **where)
2358{
2359 char *tmp;
2360
2361 if (!data) {
2362 *where = NULL;
2363 return 0;
2364 }
2365
2366 tmp = strndup_user(data, PAGE_SIZE);
2367 if (IS_ERR(tmp))
2368 return PTR_ERR(tmp);
2369
2370 *where = tmp;
2371 return 0;
2372}
2373
2374/*
2375 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2376 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2377 *
2378 * data is a (void *) that can point to any structure up to
2379 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2380 * information (or be NULL).
2381 *
2382 * Pre-0.97 versions of mount() didn't have a flags word.
2383 * When the flags word was introduced its top half was required
2384 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2385 * Therefore, if this magic number is present, it carries no information
2386 * and must be discarded.
2387 */
2388long do_mount(const char *dev_name, const char *dir_name,
2389 const char *type_page, unsigned long flags, void *data_page)
2390{
2391 struct path path;
2392 int retval = 0;
2393 int mnt_flags = 0;
2394
2395 /* Discard magic */
2396 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
2397 flags &= ~MS_MGC_MSK;
2398
2399 /* Basic sanity checks */
2400
2401 if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
2402 return -EINVAL;
2403
2404 if (data_page)
2405 ((char *)data_page)[PAGE_SIZE - 1] = 0;
2406
2407 /* ... and get the mountpoint */
2408 retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);
2409 if (retval)
2410 return retval;
2411
2412 retval = security_sb_mount(dev_name, &path,
2413 type_page, flags, data_page);
2414 if (!retval && !may_mount())
2415 retval = -EPERM;
2416 if (retval)
2417 goto dput_out;
2418
2419 /* Default to relatime unless overriden */
2420 if (!(flags & MS_NOATIME))
2421 mnt_flags |= MNT_RELATIME;
2422
2423 /* Separate the per-mountpoint flags */
2424 if (flags & MS_NOSUID)
2425 mnt_flags |= MNT_NOSUID;
2426 if (flags & MS_NODEV)
2427 mnt_flags |= MNT_NODEV;
2428 if (flags & MS_NOEXEC)
2429 mnt_flags |= MNT_NOEXEC;
2430 if (flags & MS_NOATIME)
2431 mnt_flags |= MNT_NOATIME;
2432 if (flags & MS_NODIRATIME)
2433 mnt_flags |= MNT_NODIRATIME;
2434 if (flags & MS_STRICTATIME)
2435 mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
2436 if (flags & MS_RDONLY)
2437 mnt_flags |= MNT_READONLY;
2438
2439 flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN |
2440 MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
2441 MS_STRICTATIME);
2442
2443 if (flags & MS_REMOUNT)
2444 retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
2445 data_page);
2446 else if (flags & MS_BIND)
2447 retval = do_loopback(&path, dev_name, flags & MS_REC);
2448 else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2449 retval = do_change_type(&path, flags);
2450 else if (flags & MS_MOVE)
2451 retval = do_move_mount(&path, dev_name);
2452 else
2453 retval = do_new_mount(&path, type_page, flags, mnt_flags,
2454 dev_name, data_page);
2455dput_out:
2456 path_put(&path);
2457 return retval;
2458}
2459
2460static void free_mnt_ns(struct mnt_namespace *ns)
2461{
2462 proc_free_inum(ns->proc_inum);
2463 put_user_ns(ns->user_ns);
2464 kfree(ns);
2465}
2466
2467/*
2468 * Assign a sequence number so we can detect when we attempt to bind
2469 * mount a reference to an older mount namespace into the current
2470 * mount namespace, preventing reference counting loops. A 64bit
2471 * number incrementing at 10Ghz will take 12,427 years to wrap which
2472 * is effectively never, so we can ignore the possibility.
2473 */
2474static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
2475
2476static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
2477{
2478 struct mnt_namespace *new_ns;
2479 int ret;
2480
2481 new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
2482 if (!new_ns)
2483 return ERR_PTR(-ENOMEM);
2484 ret = proc_alloc_inum(&new_ns->proc_inum);
2485 if (ret) {
2486 kfree(new_ns);
2487 return ERR_PTR(ret);
2488 }
2489 new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
2490 atomic_set(&new_ns->count, 1);
2491 new_ns->root = NULL;
2492 INIT_LIST_HEAD(&new_ns->list);
2493 init_waitqueue_head(&new_ns->poll);
2494 new_ns->event = 0;
2495 new_ns->user_ns = get_user_ns(user_ns);
2496 return new_ns;
2497}
2498
2499struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
2500 struct user_namespace *user_ns, struct fs_struct *new_fs)
2501{
2502 struct mnt_namespace *new_ns;
2503 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
2504 struct mount *p, *q;
2505 struct mount *old;
2506 struct mount *new;
2507 int copy_flags;
2508
2509 BUG_ON(!ns);
2510
2511 if (likely(!(flags & CLONE_NEWNS))) {
2512 get_mnt_ns(ns);
2513 return ns;
2514 }
2515
2516 old = ns->root;
2517
2518 new_ns = alloc_mnt_ns(user_ns);
2519 if (IS_ERR(new_ns))
2520 return new_ns;
2521
2522 namespace_lock();
2523 /* First pass: copy the tree topology */
2524 copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
2525 if (user_ns != ns->user_ns)
2526 copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED;
2527 new = copy_tree(old, old->mnt.mnt_root, copy_flags);
2528 if (IS_ERR(new)) {
2529 namespace_unlock();
2530 free_mnt_ns(new_ns);
2531 return ERR_CAST(new);
2532 }
2533 new_ns->root = new;
2534 list_add_tail(&new_ns->list, &new->mnt_list);
2535
2536 /*
2537 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2538 * as belonging to new namespace. We have already acquired a private
2539 * fs_struct, so tsk->fs->lock is not needed.
2540 */
2541 p = old;
2542 q = new;
2543 while (p) {
2544 q->mnt_ns = new_ns;
2545 if (new_fs) {
2546 if (&p->mnt == new_fs->root.mnt) {
2547 new_fs->root.mnt = mntget(&q->mnt);
2548 rootmnt = &p->mnt;
2549 }
2550 if (&p->mnt == new_fs->pwd.mnt) {
2551 new_fs->pwd.mnt = mntget(&q->mnt);
2552 pwdmnt = &p->mnt;
2553 }
2554 }
2555 p = next_mnt(p, old);
2556 q = next_mnt(q, new);
2557 if (!q)
2558 break;
2559 while (p->mnt.mnt_root != q->mnt.mnt_root)
2560 p = next_mnt(p, old);
2561 }
2562 namespace_unlock();
2563
2564 if (rootmnt)
2565 mntput(rootmnt);
2566 if (pwdmnt)
2567 mntput(pwdmnt);
2568
2569 return new_ns;
2570}
2571
2572/**
2573 * create_mnt_ns - creates a private namespace and adds a root filesystem
2574 * @mnt: pointer to the new root filesystem mountpoint
2575 */
2576static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
2577{
2578 struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns);
2579 if (!IS_ERR(new_ns)) {
2580 struct mount *mnt = real_mount(m);
2581 mnt->mnt_ns = new_ns;
2582 new_ns->root = mnt;
2583 list_add(&mnt->mnt_list, &new_ns->list);
2584 } else {
2585 mntput(m);
2586 }
2587 return new_ns;
2588}
2589
2590struct dentry *mount_subtree(struct vfsmount *mnt, const char *name)
2591{
2592 struct mnt_namespace *ns;
2593 struct super_block *s;
2594 struct path path;
2595 int err;
2596
2597 ns = create_mnt_ns(mnt);
2598 if (IS_ERR(ns))
2599 return ERR_CAST(ns);
2600
2601 err = vfs_path_lookup(mnt->mnt_root, mnt,
2602 name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
2603
2604 put_mnt_ns(ns);
2605
2606 if (err)
2607 return ERR_PTR(err);
2608
2609 /* trade a vfsmount reference for active sb one */
2610 s = path.mnt->mnt_sb;
2611 atomic_inc(&s->s_active);
2612 mntput(path.mnt);
2613 /* lock the sucker */
2614 down_write(&s->s_umount);
2615 /* ... and return the root of (sub)tree on it */
2616 return path.dentry;
2617}
2618EXPORT_SYMBOL(mount_subtree);
2619
2620SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
2621 char __user *, type, unsigned long, flags, void __user *, data)
2622{
2623 int ret;
2624 char *kernel_type;
2625 struct filename *kernel_dir;
2626 char *kernel_dev;
2627 unsigned long data_page;
2628
2629 ret = copy_mount_string(type, &kernel_type);
2630 if (ret < 0)
2631 goto out_type;
2632
2633 kernel_dir = getname(dir_name);
2634 if (IS_ERR(kernel_dir)) {
2635 ret = PTR_ERR(kernel_dir);
2636 goto out_dir;
2637 }
2638
2639 ret = copy_mount_string(dev_name, &kernel_dev);
2640 if (ret < 0)
2641 goto out_dev;
2642
2643 ret = copy_mount_options(data, &data_page);
2644 if (ret < 0)
2645 goto out_data;
2646
2647 ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags,
2648 (void *) data_page);
2649
2650 free_page(data_page);
2651out_data:
2652 kfree(kernel_dev);
2653out_dev:
2654 putname(kernel_dir);
2655out_dir:
2656 kfree(kernel_type);
2657out_type:
2658 return ret;
2659}
2660
2661/*
2662 * Return true if path is reachable from root
2663 *
2664 * namespace_sem or mount_lock is held
2665 */
2666bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
2667 const struct path *root)
2668{
2669 while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
2670 dentry = mnt->mnt_mountpoint;
2671 mnt = mnt->mnt_parent;
2672 }
2673 return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
2674}
2675
2676int path_is_under(struct path *path1, struct path *path2)
2677{
2678 int res;
2679 read_seqlock_excl(&mount_lock);
2680 res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2);
2681 read_sequnlock_excl(&mount_lock);
2682 return res;
2683}
2684EXPORT_SYMBOL(path_is_under);
2685
2686/*
2687 * pivot_root Semantics:
2688 * Moves the root file system of the current process to the directory put_old,
2689 * makes new_root as the new root file system of the current process, and sets
2690 * root/cwd of all processes which had them on the current root to new_root.
2691 *
2692 * Restrictions:
2693 * The new_root and put_old must be directories, and must not be on the
2694 * same file system as the current process root. The put_old must be
2695 * underneath new_root, i.e. adding a non-zero number of /.. to the string
2696 * pointed to by put_old must yield the same directory as new_root. No other
2697 * file system may be mounted on put_old. After all, new_root is a mountpoint.
2698 *
2699 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
2700 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
2701 * in this situation.
2702 *
2703 * Notes:
2704 * - we don't move root/cwd if they are not at the root (reason: if something
2705 * cared enough to change them, it's probably wrong to force them elsewhere)
2706 * - it's okay to pick a root that isn't the root of a file system, e.g.
2707 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
2708 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
2709 * first.
2710 */
2711SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
2712 const char __user *, put_old)
2713{
2714 struct path new, old, parent_path, root_parent, root;
2715 struct mount *new_mnt, *root_mnt, *old_mnt;
2716 struct mountpoint *old_mp, *root_mp;
2717 int error;
2718
2719 if (!may_mount())
2720 return -EPERM;
2721
2722 error = user_path_dir(new_root, &new);
2723 if (error)
2724 goto out0;
2725
2726 error = user_path_dir(put_old, &old);
2727 if (error)
2728 goto out1;
2729
2730 error = security_sb_pivotroot(&old, &new);
2731 if (error)
2732 goto out2;
2733
2734 get_fs_root(current->fs, &root);
2735 old_mp = lock_mount(&old);
2736 error = PTR_ERR(old_mp);
2737 if (IS_ERR(old_mp))
2738 goto out3;
2739
2740 error = -EINVAL;
2741 new_mnt = real_mount(new.mnt);
2742 root_mnt = real_mount(root.mnt);
2743 old_mnt = real_mount(old.mnt);
2744 if (IS_MNT_SHARED(old_mnt) ||
2745 IS_MNT_SHARED(new_mnt->mnt_parent) ||
2746 IS_MNT_SHARED(root_mnt->mnt_parent))
2747 goto out4;
2748 if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
2749 goto out4;
2750 if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
2751 goto out4;
2752 error = -ENOENT;
2753 if (d_unlinked(new.dentry))
2754 goto out4;
2755 error = -EBUSY;
2756 if (new_mnt == root_mnt || old_mnt == root_mnt)
2757 goto out4; /* loop, on the same file system */
2758 error = -EINVAL;
2759 if (root.mnt->mnt_root != root.dentry)
2760 goto out4; /* not a mountpoint */
2761 if (!mnt_has_parent(root_mnt))
2762 goto out4; /* not attached */
2763 root_mp = root_mnt->mnt_mp;
2764 if (new.mnt->mnt_root != new.dentry)
2765 goto out4; /* not a mountpoint */
2766 if (!mnt_has_parent(new_mnt))
2767 goto out4; /* not attached */
2768 /* make sure we can reach put_old from new_root */
2769 if (!is_path_reachable(old_mnt, old.dentry, &new))
2770 goto out4;
2771 root_mp->m_count++; /* pin it so it won't go away */
2772 lock_mount_hash();
2773 detach_mnt(new_mnt, &parent_path);
2774 detach_mnt(root_mnt, &root_parent);
2775 if (root_mnt->mnt.mnt_flags & MNT_LOCKED) {
2776 new_mnt->mnt.mnt_flags |= MNT_LOCKED;
2777 root_mnt->mnt.mnt_flags &= ~MNT_LOCKED;
2778 }
2779 /* mount old root on put_old */
2780 attach_mnt(root_mnt, old_mnt, old_mp);
2781 /* mount new_root on / */
2782 attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp);
2783 touch_mnt_namespace(current->nsproxy->mnt_ns);
2784 unlock_mount_hash();
2785 chroot_fs_refs(&root, &new);
2786 put_mountpoint(root_mp);
2787 error = 0;
2788out4:
2789 unlock_mount(old_mp);
2790 if (!error) {
2791 path_put(&root_parent);
2792 path_put(&parent_path);
2793 }
2794out3:
2795 path_put(&root);
2796out2:
2797 path_put(&old);
2798out1:
2799 path_put(&new);
2800out0:
2801 return error;
2802}
2803
2804static void __init init_mount_tree(void)
2805{
2806 struct vfsmount *mnt;
2807 struct mnt_namespace *ns;
2808 struct path root;
2809 struct file_system_type *type;
2810
2811 type = get_fs_type("rootfs");
2812 if (!type)
2813 panic("Can't find rootfs type");
2814 mnt = vfs_kern_mount(type, 0, "rootfs", NULL);
2815 put_filesystem(type);
2816 if (IS_ERR(mnt))
2817 panic("Can't create rootfs");
2818
2819 ns = create_mnt_ns(mnt);
2820 if (IS_ERR(ns))
2821 panic("Can't allocate initial namespace");
2822
2823 init_task.nsproxy->mnt_ns = ns;
2824 get_mnt_ns(ns);
2825
2826 root.mnt = mnt;
2827 root.dentry = mnt->mnt_root;
2828
2829 set_fs_pwd(current->fs, &root);
2830 set_fs_root(current->fs, &root);
2831}
2832
2833void __init mnt_init(void)
2834{
2835 unsigned u;
2836 int err;
2837
2838 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
2839 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
2840
2841 mount_hashtable = alloc_large_system_hash("Mount-cache",
2842 sizeof(struct hlist_head),
2843 mhash_entries, 19,
2844 0,
2845 &m_hash_shift, &m_hash_mask, 0, 0);
2846 mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache",
2847 sizeof(struct hlist_head),
2848 mphash_entries, 19,
2849 0,
2850 &mp_hash_shift, &mp_hash_mask, 0, 0);
2851
2852 if (!mount_hashtable || !mountpoint_hashtable)
2853 panic("Failed to allocate mount hash table\n");
2854
2855 for (u = 0; u <= m_hash_mask; u++)
2856 INIT_HLIST_HEAD(&mount_hashtable[u]);
2857 for (u = 0; u <= mp_hash_mask; u++)
2858 INIT_HLIST_HEAD(&mountpoint_hashtable[u]);
2859
2860 kernfs_init();
2861
2862 err = sysfs_init();
2863 if (err)
2864 printk(KERN_WARNING "%s: sysfs_init error: %d\n",
2865 __func__, err);
2866 fs_kobj = kobject_create_and_add("fs", NULL);
2867 if (!fs_kobj)
2868 printk(KERN_WARNING "%s: kobj create error\n", __func__);
2869 init_rootfs();
2870 init_mount_tree();
2871}
2872
2873void put_mnt_ns(struct mnt_namespace *ns)
2874{
2875 if (!atomic_dec_and_test(&ns->count))
2876 return;
2877 drop_collected_mounts(&ns->root->mnt);
2878 free_mnt_ns(ns);
2879}
2880
2881struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
2882{
2883 struct vfsmount *mnt;
2884 mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
2885 if (!IS_ERR(mnt)) {
2886 /*
2887 * it is a longterm mount, don't release mnt until
2888 * we unmount before file sys is unregistered
2889 */
2890 real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
2891 }
2892 return mnt;
2893}
2894EXPORT_SYMBOL_GPL(kern_mount_data);
2895
2896void kern_unmount(struct vfsmount *mnt)
2897{
2898 /* release long term mount so mount point can be released */
2899 if (!IS_ERR_OR_NULL(mnt)) {
2900 real_mount(mnt)->mnt_ns = NULL;
2901 synchronize_rcu(); /* yecchhh... */
2902 mntput(mnt);
2903 }
2904}
2905EXPORT_SYMBOL(kern_unmount);
2906
2907bool our_mnt(struct vfsmount *mnt)
2908{
2909 return check_mnt(real_mount(mnt));
2910}
2911
2912bool current_chrooted(void)
2913{
2914 /* Does the current process have a non-standard root */
2915 struct path ns_root;
2916 struct path fs_root;
2917 bool chrooted;
2918
2919 /* Find the namespace root */
2920 ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt;
2921 ns_root.dentry = ns_root.mnt->mnt_root;
2922 path_get(&ns_root);
2923 while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root))
2924 ;
2925
2926 get_fs_root(current->fs, &fs_root);
2927
2928 chrooted = !path_equal(&fs_root, &ns_root);
2929
2930 path_put(&fs_root);
2931 path_put(&ns_root);
2932
2933 return chrooted;
2934}
2935
2936bool fs_fully_visible(struct file_system_type *type)
2937{
2938 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
2939 struct mount *mnt;
2940 bool visible = false;
2941
2942 if (unlikely(!ns))
2943 return false;
2944
2945 down_read(&namespace_sem);
2946 list_for_each_entry(mnt, &ns->list, mnt_list) {
2947 struct mount *child;
2948 if (mnt->mnt.mnt_sb->s_type != type)
2949 continue;
2950
2951 /* This mount is not fully visible if there are any child mounts
2952 * that cover anything except for empty directories.
2953 */
2954 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
2955 struct inode *inode = child->mnt_mountpoint->d_inode;
2956 if (!S_ISDIR(inode->i_mode))
2957 goto next;
2958 if (inode->i_nlink > 2)
2959 goto next;
2960 }
2961 visible = true;
2962 goto found;
2963 next: ;
2964 }
2965found:
2966 up_read(&namespace_sem);
2967 return visible;
2968}
2969
2970static void *mntns_get(struct task_struct *task)
2971{
2972 struct mnt_namespace *ns = NULL;
2973 struct nsproxy *nsproxy;
2974
2975 rcu_read_lock();
2976 nsproxy = task_nsproxy(task);
2977 if (nsproxy) {
2978 ns = nsproxy->mnt_ns;
2979 get_mnt_ns(ns);
2980 }
2981 rcu_read_unlock();
2982
2983 return ns;
2984}
2985
2986static void mntns_put(void *ns)
2987{
2988 put_mnt_ns(ns);
2989}
2990
2991static int mntns_install(struct nsproxy *nsproxy, void *ns)
2992{
2993 struct fs_struct *fs = current->fs;
2994 struct mnt_namespace *mnt_ns = ns;
2995 struct path root;
2996
2997 if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
2998 !ns_capable(current_user_ns(), CAP_SYS_CHROOT) ||
2999 !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
3000 return -EPERM;
3001
3002 if (fs->users != 1)
3003 return -EINVAL;
3004
3005 get_mnt_ns(mnt_ns);
3006 put_mnt_ns(nsproxy->mnt_ns);
3007 nsproxy->mnt_ns = mnt_ns;
3008
3009 /* Find the root */
3010 root.mnt = &mnt_ns->root->mnt;
3011 root.dentry = mnt_ns->root->mnt.mnt_root;
3012 path_get(&root);
3013 while(d_mountpoint(root.dentry) && follow_down_one(&root))
3014 ;
3015
3016 /* Update the pwd and root */
3017 set_fs_pwd(fs, &root);
3018 set_fs_root(fs, &root);
3019
3020 path_put(&root);
3021 return 0;
3022}
3023
3024static unsigned int mntns_inum(void *ns)
3025{
3026 struct mnt_namespace *mnt_ns = ns;
3027 return mnt_ns->proc_inum;
3028}
3029
3030const struct proc_ns_operations mntns_operations = {
3031 .name = "mnt",
3032 .type = CLONE_NEWNS,
3033 .get = mntns_get,
3034 .put = mntns_put,
3035 .install = mntns_install,
3036 .inum = mntns_inum,
3037};