4 * (C) Copyright Al Viro 2000, 2001
5 * Released under GPL v2.
7 * Based on code from fs/super.c, copyright Linus Torvalds and others.
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/init.h> /* init_rootfs */
20 #include <linux/fs_struct.h> /* get_fs_root et.al. */
21 #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */
22 #include <linux/uaccess.h>
23 #include <linux/proc_ns.h>
24 #include <linux/magic.h>
25 #include <linux/bootmem.h>
26 #include <linux/task_work.h>
30 /* Maximum number of mounts in a mount namespace */
31 unsigned int sysctl_mount_max __read_mostly = 100000;
33 static unsigned int m_hash_mask __read_mostly;
34 static unsigned int m_hash_shift __read_mostly;
35 static unsigned int mp_hash_mask __read_mostly;
36 static unsigned int mp_hash_shift __read_mostly;
38 static __initdata unsigned long mhash_entries;
39 static int __init set_mhash_entries(char *str)
43 mhash_entries = simple_strtoul(str, &str, 0);
46 __setup("mhash_entries=", set_mhash_entries);
48 static __initdata unsigned long mphash_entries;
49 static int __init set_mphash_entries(char *str)
53 mphash_entries = simple_strtoul(str, &str, 0);
56 __setup("mphash_entries=", set_mphash_entries);
59 static DEFINE_IDA(mnt_id_ida);
60 static DEFINE_IDA(mnt_group_ida);
61 static DEFINE_SPINLOCK(mnt_id_lock);
62 static int mnt_id_start = 0;
63 static int mnt_group_start = 1;
65 static struct hlist_head *mount_hashtable __read_mostly;
66 static struct hlist_head *mountpoint_hashtable __read_mostly;
67 static struct kmem_cache *mnt_cache __read_mostly;
68 static DECLARE_RWSEM(namespace_sem);
71 struct kobject *fs_kobj;
72 EXPORT_SYMBOL_GPL(fs_kobj);
75 * vfsmount lock may be taken for read to prevent changes to the
76 * vfsmount hash, ie. during mountpoint lookups or walking back
79 * It should be taken for write in all cases where the vfsmount
80 * tree or hash is modified or when a vfsmount structure is modified.
82 __cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock);
84 static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry)
86 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
87 tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
88 tmp = tmp + (tmp >> m_hash_shift);
89 return &mount_hashtable[tmp & m_hash_mask];
92 static inline struct hlist_head *mp_hash(struct dentry *dentry)
94 unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES);
95 tmp = tmp + (tmp >> mp_hash_shift);
96 return &mountpoint_hashtable[tmp & mp_hash_mask];
100 * allocation is serialized by namespace_sem, but we need the spinlock to
101 * serialize with freeing.
103 static int mnt_alloc_id(struct mount *mnt)
108 ida_pre_get(&mnt_id_ida, GFP_KERNEL);
109 spin_lock(&mnt_id_lock);
110 res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id);
112 mnt_id_start = mnt->mnt_id + 1;
113 spin_unlock(&mnt_id_lock);
120 static void mnt_free_id(struct mount *mnt)
122 int id = mnt->mnt_id;
123 spin_lock(&mnt_id_lock);
124 ida_remove(&mnt_id_ida, id);
125 if (mnt_id_start > id)
127 spin_unlock(&mnt_id_lock);
131 * Allocate a new peer group ID
133 * mnt_group_ida is protected by namespace_sem
135 static int mnt_alloc_group_id(struct mount *mnt)
139 if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
142 res = ida_get_new_above(&mnt_group_ida,
146 mnt_group_start = mnt->mnt_group_id + 1;
152 * Release a peer group ID
154 void mnt_release_group_id(struct mount *mnt)
156 int id = mnt->mnt_group_id;
157 ida_remove(&mnt_group_ida, id);
158 if (mnt_group_start > id)
159 mnt_group_start = id;
160 mnt->mnt_group_id = 0;
164 * vfsmount lock must be held for read
166 static inline void mnt_add_count(struct mount *mnt, int n)
169 this_cpu_add(mnt->mnt_pcp->mnt_count, n);
178 * vfsmount lock must be held for write
180 unsigned int mnt_get_count(struct mount *mnt)
183 unsigned int count = 0;
186 for_each_possible_cpu(cpu) {
187 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
192 return mnt->mnt_count;
196 static void drop_mountpoint(struct fs_pin *p)
198 struct mount *m = container_of(p, struct mount, mnt_umount);
199 dput(m->mnt_ex_mountpoint);
204 static struct mount *alloc_vfsmnt(const char *name)
206 struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
210 err = mnt_alloc_id(mnt);
215 mnt->mnt_devname = kstrdup_const(name, GFP_KERNEL);
216 if (!mnt->mnt_devname)
221 mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
223 goto out_free_devname;
225 this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
228 mnt->mnt_writers = 0;
230 mnt->mnt.data = NULL;
232 INIT_HLIST_NODE(&mnt->mnt_hash);
233 INIT_LIST_HEAD(&mnt->mnt_child);
234 INIT_LIST_HEAD(&mnt->mnt_mounts);
235 INIT_LIST_HEAD(&mnt->mnt_list);
236 INIT_LIST_HEAD(&mnt->mnt_expire);
237 INIT_LIST_HEAD(&mnt->mnt_share);
238 INIT_LIST_HEAD(&mnt->mnt_slave_list);
239 INIT_LIST_HEAD(&mnt->mnt_slave);
240 INIT_HLIST_NODE(&mnt->mnt_mp_list);
241 INIT_LIST_HEAD(&mnt->mnt_umounting);
242 #ifdef CONFIG_FSNOTIFY
243 INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);
245 init_fs_pin(&mnt->mnt_umount, drop_mountpoint);
251 kfree_const(mnt->mnt_devname);
256 kmem_cache_free(mnt_cache, mnt);
261 * Most r/o checks on a fs are for operations that take
262 * discrete amounts of time, like a write() or unlink().
263 * We must keep track of when those operations start
264 * (for permission checks) and when they end, so that
265 * we can determine when writes are able to occur to
269 * __mnt_is_readonly: check whether a mount is read-only
270 * @mnt: the mount to check for its write status
272 * This shouldn't be used directly ouside of the VFS.
273 * It does not guarantee that the filesystem will stay
274 * r/w, just that it is right *now*. This can not and
275 * should not be used in place of IS_RDONLY(inode).
276 * mnt_want/drop_write() will _keep_ the filesystem
279 int __mnt_is_readonly(struct vfsmount *mnt)
281 if (mnt->mnt_flags & MNT_READONLY)
283 if (mnt->mnt_sb->s_flags & MS_RDONLY)
287 EXPORT_SYMBOL_GPL(__mnt_is_readonly);
289 static inline void mnt_inc_writers(struct mount *mnt)
292 this_cpu_inc(mnt->mnt_pcp->mnt_writers);
298 static inline void mnt_dec_writers(struct mount *mnt)
301 this_cpu_dec(mnt->mnt_pcp->mnt_writers);
307 static unsigned int mnt_get_writers(struct mount *mnt)
310 unsigned int count = 0;
313 for_each_possible_cpu(cpu) {
314 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
319 return mnt->mnt_writers;
323 static int mnt_is_readonly(struct vfsmount *mnt)
325 if (mnt->mnt_sb->s_readonly_remount)
327 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
329 return __mnt_is_readonly(mnt);
333 * Most r/o & frozen checks on a fs are for operations that take discrete
334 * amounts of time, like a write() or unlink(). We must keep track of when
335 * those operations start (for permission checks) and when they end, so that we
336 * can determine when writes are able to occur to a filesystem.
339 * __mnt_want_write - get write access to a mount without freeze protection
340 * @m: the mount on which to take a write
342 * This tells the low-level filesystem that a write is about to be performed to
343 * it, and makes sure that writes are allowed (mnt it read-write) before
344 * returning success. This operation does not protect against filesystem being
345 * frozen. When the write operation is finished, __mnt_drop_write() must be
346 * called. This is effectively a refcount.
348 int __mnt_want_write(struct vfsmount *m)
350 struct mount *mnt = real_mount(m);
354 mnt_inc_writers(mnt);
356 * The store to mnt_inc_writers must be visible before we pass
357 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
358 * incremented count after it has set MNT_WRITE_HOLD.
361 while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
364 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
365 * be set to match its requirements. So we must not load that until
366 * MNT_WRITE_HOLD is cleared.
369 if (mnt_is_readonly(m)) {
370 mnt_dec_writers(mnt);
379 * mnt_want_write - get write access to a mount
380 * @m: the mount on which to take a write
382 * This tells the low-level filesystem that a write is about to be performed to
383 * it, and makes sure that writes are allowed (mount is read-write, filesystem
384 * is not frozen) before returning success. When the write operation is
385 * finished, mnt_drop_write() must be called. This is effectively a refcount.
387 int mnt_want_write(struct vfsmount *m)
391 sb_start_write(m->mnt_sb);
392 ret = __mnt_want_write(m);
394 sb_end_write(m->mnt_sb);
397 EXPORT_SYMBOL_GPL(mnt_want_write);
400 * mnt_clone_write - get write access to a mount
401 * @mnt: the mount on which to take a write
403 * This is effectively like mnt_want_write, except
404 * it must only be used to take an extra write reference
405 * on a mountpoint that we already know has a write reference
406 * on it. This allows some optimisation.
408 * After finished, mnt_drop_write must be called as usual to
409 * drop the reference.
411 int mnt_clone_write(struct vfsmount *mnt)
413 /* superblock may be r/o */
414 if (__mnt_is_readonly(mnt))
417 mnt_inc_writers(real_mount(mnt));
421 EXPORT_SYMBOL_GPL(mnt_clone_write);
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
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
430 int __mnt_want_write_file(struct file *file)
432 if (!(file->f_mode & FMODE_WRITER))
433 return __mnt_want_write(file->f_path.mnt);
435 return mnt_clone_write(file->f_path.mnt);
439 * mnt_want_write_file - get write access to a file's mount
440 * @file: the file who's mount on which to take a write
442 * This is like mnt_want_write, but it takes a file and can
443 * do some optimisations if the file is open for write already
445 int mnt_want_write_file(struct file *file)
449 sb_start_write(file->f_path.mnt->mnt_sb);
450 ret = __mnt_want_write_file(file);
452 sb_end_write(file->f_path.mnt->mnt_sb);
455 EXPORT_SYMBOL_GPL(mnt_want_write_file);
458 * __mnt_drop_write - give up write access to a mount
459 * @mnt: the mount on which to give up write access
461 * Tells the low-level filesystem that we are done
462 * performing writes to it. Must be matched with
463 * __mnt_want_write() call above.
465 void __mnt_drop_write(struct vfsmount *mnt)
468 mnt_dec_writers(real_mount(mnt));
473 * mnt_drop_write - give up write access to a mount
474 * @mnt: the mount on which to give up write access
476 * Tells the low-level filesystem that we are done performing writes to it and
477 * also allows filesystem to be frozen again. Must be matched with
478 * mnt_want_write() call above.
480 void mnt_drop_write(struct vfsmount *mnt)
482 __mnt_drop_write(mnt);
483 sb_end_write(mnt->mnt_sb);
485 EXPORT_SYMBOL_GPL(mnt_drop_write);
487 void __mnt_drop_write_file(struct file *file)
489 __mnt_drop_write(file->f_path.mnt);
492 void mnt_drop_write_file(struct file *file)
494 mnt_drop_write(file->f_path.mnt);
496 EXPORT_SYMBOL(mnt_drop_write_file);
498 static int mnt_make_readonly(struct mount *mnt)
503 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
505 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
506 * should be visible before we do.
511 * With writers on hold, if this value is zero, then there are
512 * definitely no active writers (although held writers may subsequently
513 * increment the count, they'll have to wait, and decrement it after
514 * seeing MNT_READONLY).
516 * It is OK to have counter incremented on one CPU and decremented on
517 * another: the sum will add up correctly. The danger would be when we
518 * sum up each counter, if we read a counter before it is incremented,
519 * but then read another CPU's count which it has been subsequently
520 * decremented from -- we would see more decrements than we should.
521 * MNT_WRITE_HOLD protects against this scenario, because
522 * mnt_want_write first increments count, then smp_mb, then spins on
523 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
524 * we're counting up here.
526 if (mnt_get_writers(mnt) > 0)
529 mnt->mnt.mnt_flags |= MNT_READONLY;
531 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
532 * that become unheld will see MNT_READONLY.
535 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
540 static void __mnt_unmake_readonly(struct mount *mnt)
543 mnt->mnt.mnt_flags &= ~MNT_READONLY;
547 int sb_prepare_remount_readonly(struct super_block *sb)
552 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
553 if (atomic_long_read(&sb->s_remove_count))
557 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
558 if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
559 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
561 if (mnt_get_writers(mnt) > 0) {
567 if (!err && atomic_long_read(&sb->s_remove_count))
571 sb->s_readonly_remount = 1;
574 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
575 if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
576 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
583 static void free_vfsmnt(struct mount *mnt)
585 kfree(mnt->mnt.data);
586 kfree_const(mnt->mnt_devname);
588 free_percpu(mnt->mnt_pcp);
590 kmem_cache_free(mnt_cache, mnt);
593 static void delayed_free_vfsmnt(struct rcu_head *head)
595 free_vfsmnt(container_of(head, struct mount, mnt_rcu));
598 /* call under rcu_read_lock */
599 int __legitimize_mnt(struct vfsmount *bastard, unsigned seq)
602 if (read_seqretry(&mount_lock, seq))
606 mnt = real_mount(bastard);
607 mnt_add_count(mnt, 1);
608 smp_mb(); // see mntput_no_expire()
609 if (likely(!read_seqretry(&mount_lock, seq)))
611 if (bastard->mnt_flags & MNT_SYNC_UMOUNT) {
612 mnt_add_count(mnt, -1);
616 if (unlikely(bastard->mnt_flags & MNT_DOOMED)) {
617 mnt_add_count(mnt, -1);
622 /* caller will mntput() */
626 /* call under rcu_read_lock */
627 bool legitimize_mnt(struct vfsmount *bastard, unsigned seq)
629 int res = __legitimize_mnt(bastard, seq);
632 if (unlikely(res < 0)) {
641 * find the first mount at @dentry on vfsmount @mnt.
642 * call under rcu_read_lock()
644 struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
646 struct hlist_head *head = m_hash(mnt, dentry);
649 hlist_for_each_entry_rcu(p, head, mnt_hash)
650 if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
656 * lookup_mnt - Return the first child mount mounted at path
658 * "First" means first mounted chronologically. If you create the
661 * mount /dev/sda1 /mnt
662 * mount /dev/sda2 /mnt
663 * mount /dev/sda3 /mnt
665 * Then lookup_mnt() on the base /mnt dentry in the root mount will
666 * return successively the root dentry and vfsmount of /dev/sda1, then
667 * /dev/sda2, then /dev/sda3, then NULL.
669 * lookup_mnt takes a reference to the found vfsmount.
671 struct vfsmount *lookup_mnt(struct path *path)
673 struct mount *child_mnt;
679 seq = read_seqbegin(&mount_lock);
680 child_mnt = __lookup_mnt(path->mnt, path->dentry);
681 m = child_mnt ? &child_mnt->mnt : NULL;
682 } while (!legitimize_mnt(m, seq));
688 * __is_local_mountpoint - Test to see if dentry is a mountpoint in the
689 * current mount namespace.
691 * The common case is dentries are not mountpoints at all and that
692 * test is handled inline. For the slow case when we are actually
693 * dealing with a mountpoint of some kind, walk through all of the
694 * mounts in the current mount namespace and test to see if the dentry
697 * The mount_hashtable is not usable in the context because we
698 * need to identify all mounts that may be in the current mount
699 * namespace not just a mount that happens to have some specified
702 bool __is_local_mountpoint(struct dentry *dentry)
704 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
706 bool is_covered = false;
708 if (!d_mountpoint(dentry))
711 down_read(&namespace_sem);
712 list_for_each_entry(mnt, &ns->list, mnt_list) {
713 is_covered = (mnt->mnt_mountpoint == dentry);
717 up_read(&namespace_sem);
722 static struct mountpoint *lookup_mountpoint(struct dentry *dentry)
724 struct hlist_head *chain = mp_hash(dentry);
725 struct mountpoint *mp;
727 hlist_for_each_entry(mp, chain, m_hash) {
728 if (mp->m_dentry == dentry) {
729 /* might be worth a WARN_ON() */
730 if (d_unlinked(dentry))
731 return ERR_PTR(-ENOENT);
739 static struct mountpoint *get_mountpoint(struct dentry *dentry)
741 struct mountpoint *mp, *new = NULL;
744 if (d_mountpoint(dentry)) {
746 read_seqlock_excl(&mount_lock);
747 mp = lookup_mountpoint(dentry);
748 read_sequnlock_excl(&mount_lock);
754 new = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
756 return ERR_PTR(-ENOMEM);
759 /* Exactly one processes may set d_mounted */
760 ret = d_set_mounted(dentry);
762 /* Someone else set d_mounted? */
766 /* The dentry is not available as a mountpoint? */
771 /* Add the new mountpoint to the hash table */
772 read_seqlock_excl(&mount_lock);
773 new->m_dentry = dentry;
775 hlist_add_head(&new->m_hash, mp_hash(dentry));
776 INIT_HLIST_HEAD(&new->m_list);
777 read_sequnlock_excl(&mount_lock);
786 static void put_mountpoint(struct mountpoint *mp)
788 if (!--mp->m_count) {
789 struct dentry *dentry = mp->m_dentry;
790 BUG_ON(!hlist_empty(&mp->m_list));
791 spin_lock(&dentry->d_lock);
792 dentry->d_flags &= ~DCACHE_MOUNTED;
793 spin_unlock(&dentry->d_lock);
794 hlist_del(&mp->m_hash);
799 static inline int check_mnt(struct mount *mnt)
801 return mnt->mnt_ns == current->nsproxy->mnt_ns;
805 * vfsmount lock must be held for write
807 static void touch_mnt_namespace(struct mnt_namespace *ns)
811 wake_up_interruptible(&ns->poll);
816 * vfsmount lock must be held for write
818 static void __touch_mnt_namespace(struct mnt_namespace *ns)
820 if (ns && ns->event != event) {
822 wake_up_interruptible(&ns->poll);
827 * vfsmount lock must be held for write
829 static void unhash_mnt(struct mount *mnt)
831 mnt->mnt_parent = mnt;
832 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
833 list_del_init(&mnt->mnt_child);
834 hlist_del_init_rcu(&mnt->mnt_hash);
835 hlist_del_init(&mnt->mnt_mp_list);
836 put_mountpoint(mnt->mnt_mp);
841 * vfsmount lock must be held for write
843 static void detach_mnt(struct mount *mnt, struct path *old_path)
845 old_path->dentry = mnt->mnt_mountpoint;
846 old_path->mnt = &mnt->mnt_parent->mnt;
851 * vfsmount lock must be held for write
853 static void umount_mnt(struct mount *mnt)
855 /* old mountpoint will be dropped when we can do that */
856 mnt->mnt_ex_mountpoint = mnt->mnt_mountpoint;
861 * vfsmount lock must be held for write
863 void mnt_set_mountpoint(struct mount *mnt,
864 struct mountpoint *mp,
865 struct mount *child_mnt)
868 mnt_add_count(mnt, 1); /* essentially, that's mntget */
869 child_mnt->mnt_mountpoint = dget(mp->m_dentry);
870 child_mnt->mnt_parent = mnt;
871 child_mnt->mnt_mp = mp;
872 hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list);
875 static void __attach_mnt(struct mount *mnt, struct mount *parent)
877 hlist_add_head_rcu(&mnt->mnt_hash,
878 m_hash(&parent->mnt, mnt->mnt_mountpoint));
879 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
883 * vfsmount lock must be held for write
885 static void attach_mnt(struct mount *mnt,
886 struct mount *parent,
887 struct mountpoint *mp)
889 mnt_set_mountpoint(parent, mp, mnt);
890 __attach_mnt(mnt, parent);
893 void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp, struct mount *mnt)
895 struct mountpoint *old_mp = mnt->mnt_mp;
896 struct dentry *old_mountpoint = mnt->mnt_mountpoint;
897 struct mount *old_parent = mnt->mnt_parent;
899 list_del_init(&mnt->mnt_child);
900 hlist_del_init(&mnt->mnt_mp_list);
901 hlist_del_init_rcu(&mnt->mnt_hash);
903 attach_mnt(mnt, parent, mp);
905 put_mountpoint(old_mp);
908 * Safely avoid even the suggestion this code might sleep or
909 * lock the mount hash by taking advantage of the knowledge that
910 * mnt_change_mountpoint will not release the final reference
913 * During mounting, the mount passed in as the parent mount will
914 * continue to use the old mountpoint and during unmounting, the
915 * old mountpoint will continue to exist until namespace_unlock,
916 * which happens well after mnt_change_mountpoint.
918 spin_lock(&old_mountpoint->d_lock);
919 old_mountpoint->d_lockref.count--;
920 spin_unlock(&old_mountpoint->d_lock);
922 mnt_add_count(old_parent, -1);
926 * vfsmount lock must be held for write
928 static void commit_tree(struct mount *mnt)
930 struct mount *parent = mnt->mnt_parent;
933 struct mnt_namespace *n = parent->mnt_ns;
935 BUG_ON(parent == mnt);
937 list_add_tail(&head, &mnt->mnt_list);
938 list_for_each_entry(m, &head, mnt_list)
941 list_splice(&head, n->list.prev);
943 n->mounts += n->pending_mounts;
944 n->pending_mounts = 0;
946 __attach_mnt(mnt, parent);
947 touch_mnt_namespace(n);
950 static struct mount *next_mnt(struct mount *p, struct mount *root)
952 struct list_head *next = p->mnt_mounts.next;
953 if (next == &p->mnt_mounts) {
957 next = p->mnt_child.next;
958 if (next != &p->mnt_parent->mnt_mounts)
963 return list_entry(next, struct mount, mnt_child);
966 static struct mount *skip_mnt_tree(struct mount *p)
968 struct list_head *prev = p->mnt_mounts.prev;
969 while (prev != &p->mnt_mounts) {
970 p = list_entry(prev, struct mount, mnt_child);
971 prev = p->mnt_mounts.prev;
977 vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
983 return ERR_PTR(-ENODEV);
985 mnt = alloc_vfsmnt(name);
987 return ERR_PTR(-ENOMEM);
989 if (type->alloc_mnt_data) {
990 mnt->mnt.data = type->alloc_mnt_data();
991 if (!mnt->mnt.data) {
994 return ERR_PTR(-ENOMEM);
997 if (flags & MS_KERNMOUNT)
998 mnt->mnt.mnt_flags = MNT_INTERNAL;
1000 root = mount_fs(type, flags, name, &mnt->mnt, data);
1004 return ERR_CAST(root);
1007 mnt->mnt.mnt_root = root;
1008 mnt->mnt.mnt_sb = root->d_sb;
1009 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
1010 mnt->mnt_parent = mnt;
1012 list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts);
1013 unlock_mount_hash();
1016 EXPORT_SYMBOL_GPL(vfs_kern_mount);
1018 static struct mount *clone_mnt(struct mount *old, struct dentry *root,
1021 struct super_block *sb = old->mnt.mnt_sb;
1025 mnt = alloc_vfsmnt(old->mnt_devname);
1027 return ERR_PTR(-ENOMEM);
1029 if (sb->s_op->clone_mnt_data) {
1030 mnt->mnt.data = sb->s_op->clone_mnt_data(old->mnt.data);
1031 if (!mnt->mnt.data) {
1037 if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
1038 mnt->mnt_group_id = 0; /* not a peer of original */
1040 mnt->mnt_group_id = old->mnt_group_id;
1042 if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
1043 err = mnt_alloc_group_id(mnt);
1048 mnt->mnt.mnt_flags = old->mnt.mnt_flags;
1049 mnt->mnt.mnt_flags &= ~(MNT_WRITE_HOLD|MNT_MARKED|MNT_INTERNAL);
1050 /* Don't allow unprivileged users to change mount flags */
1051 if (flag & CL_UNPRIVILEGED) {
1052 mnt->mnt.mnt_flags |= MNT_LOCK_ATIME;
1054 if (mnt->mnt.mnt_flags & MNT_READONLY)
1055 mnt->mnt.mnt_flags |= MNT_LOCK_READONLY;
1057 if (mnt->mnt.mnt_flags & MNT_NODEV)
1058 mnt->mnt.mnt_flags |= MNT_LOCK_NODEV;
1060 if (mnt->mnt.mnt_flags & MNT_NOSUID)
1061 mnt->mnt.mnt_flags |= MNT_LOCK_NOSUID;
1063 if (mnt->mnt.mnt_flags & MNT_NOEXEC)
1064 mnt->mnt.mnt_flags |= MNT_LOCK_NOEXEC;
1067 /* Don't allow unprivileged users to reveal what is under a mount */
1068 if ((flag & CL_UNPRIVILEGED) &&
1069 (!(flag & CL_EXPIRE) || list_empty(&old->mnt_expire)))
1070 mnt->mnt.mnt_flags |= MNT_LOCKED;
1072 atomic_inc(&sb->s_active);
1073 mnt->mnt.mnt_sb = sb;
1074 mnt->mnt.mnt_root = dget(root);
1075 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
1076 mnt->mnt_parent = mnt;
1078 list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
1079 unlock_mount_hash();
1081 if ((flag & CL_SLAVE) ||
1082 ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
1083 list_add(&mnt->mnt_slave, &old->mnt_slave_list);
1084 mnt->mnt_master = old;
1085 CLEAR_MNT_SHARED(mnt);
1086 } else if (!(flag & CL_PRIVATE)) {
1087 if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
1088 list_add(&mnt->mnt_share, &old->mnt_share);
1089 if (IS_MNT_SLAVE(old))
1090 list_add(&mnt->mnt_slave, &old->mnt_slave);
1091 mnt->mnt_master = old->mnt_master;
1093 if (flag & CL_MAKE_SHARED)
1094 set_mnt_shared(mnt);
1096 /* stick the duplicate mount on the same expiry list
1097 * as the original if that was on one */
1098 if (flag & CL_EXPIRE) {
1099 if (!list_empty(&old->mnt_expire))
1100 list_add(&mnt->mnt_expire, &old->mnt_expire);
1108 return ERR_PTR(err);
1111 static void cleanup_mnt(struct mount *mnt)
1114 * This probably indicates that somebody messed
1115 * up a mnt_want/drop_write() pair. If this
1116 * happens, the filesystem was probably unable
1117 * to make r/w->r/o transitions.
1120 * The locking used to deal with mnt_count decrement provides barriers,
1121 * so mnt_get_writers() below is safe.
1123 WARN_ON(mnt_get_writers(mnt));
1124 if (unlikely(mnt->mnt_pins.first))
1126 fsnotify_vfsmount_delete(&mnt->mnt);
1127 dput(mnt->mnt.mnt_root);
1128 deactivate_super(mnt->mnt.mnt_sb);
1130 call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt);
1133 static void __cleanup_mnt(struct rcu_head *head)
1135 cleanup_mnt(container_of(head, struct mount, mnt_rcu));
1138 static LLIST_HEAD(delayed_mntput_list);
1139 static void delayed_mntput(struct work_struct *unused)
1141 struct llist_node *node = llist_del_all(&delayed_mntput_list);
1142 struct llist_node *next;
1144 for (; node; node = next) {
1145 next = llist_next(node);
1146 cleanup_mnt(llist_entry(node, struct mount, mnt_llist));
1149 static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput);
1151 static void mntput_no_expire(struct mount *mnt)
1154 if (likely(READ_ONCE(mnt->mnt_ns))) {
1156 * Since we don't do lock_mount_hash() here,
1157 * ->mnt_ns can change under us. However, if it's
1158 * non-NULL, then there's a reference that won't
1159 * be dropped until after an RCU delay done after
1160 * turning ->mnt_ns NULL. So if we observe it
1161 * non-NULL under rcu_read_lock(), the reference
1162 * we are dropping is not the final one.
1164 mnt_add_count(mnt, -1);
1170 * make sure that if __legitimize_mnt() has not seen us grab
1171 * mount_lock, we'll see their refcount increment here.
1174 mnt_add_count(mnt, -1);
1175 if (mnt_get_count(mnt)) {
1177 unlock_mount_hash();
1180 if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) {
1182 unlock_mount_hash();
1185 mnt->mnt.mnt_flags |= MNT_DOOMED;
1188 list_del(&mnt->mnt_instance);
1190 if (unlikely(!list_empty(&mnt->mnt_mounts))) {
1191 struct mount *p, *tmp;
1192 list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) {
1196 unlock_mount_hash();
1198 if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) {
1199 struct task_struct *task = current;
1200 if (likely(!(task->flags & PF_KTHREAD))) {
1201 init_task_work(&mnt->mnt_rcu, __cleanup_mnt);
1202 if (!task_work_add(task, &mnt->mnt_rcu, true))
1205 if (llist_add(&mnt->mnt_llist, &delayed_mntput_list))
1206 schedule_delayed_work(&delayed_mntput_work, 1);
1212 void mntput(struct vfsmount *mnt)
1215 struct mount *m = real_mount(mnt);
1216 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
1217 if (unlikely(m->mnt_expiry_mark))
1218 m->mnt_expiry_mark = 0;
1219 mntput_no_expire(m);
1222 EXPORT_SYMBOL(mntput);
1224 struct vfsmount *mntget(struct vfsmount *mnt)
1227 mnt_add_count(real_mount(mnt), 1);
1230 EXPORT_SYMBOL(mntget);
1232 struct vfsmount *mnt_clone_internal(struct path *path)
1235 p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE);
1238 p->mnt.mnt_flags |= MNT_INTERNAL;
1242 static inline void mangle(struct seq_file *m, const char *s)
1244 seq_escape(m, s, " \t\n\\");
1248 * Simple .show_options callback for filesystems which don't want to
1249 * implement more complex mount option showing.
1251 * See also save_mount_options().
1253 int generic_show_options(struct seq_file *m, struct dentry *root)
1255 const char *options;
1258 options = rcu_dereference(root->d_sb->s_options);
1260 if (options != NULL && options[0]) {
1268 EXPORT_SYMBOL(generic_show_options);
1271 * If filesystem uses generic_show_options(), this function should be
1272 * called from the fill_super() callback.
1274 * The .remount_fs callback usually needs to be handled in a special
1275 * way, to make sure, that previous options are not overwritten if the
1278 * Also note, that if the filesystem's .remount_fs function doesn't
1279 * reset all options to their default value, but changes only newly
1280 * given options, then the displayed options will not reflect reality
1283 void save_mount_options(struct super_block *sb, char *options)
1285 BUG_ON(sb->s_options);
1286 rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL));
1288 EXPORT_SYMBOL(save_mount_options);
1290 void replace_mount_options(struct super_block *sb, char *options)
1292 char *old = sb->s_options;
1293 rcu_assign_pointer(sb->s_options, options);
1299 EXPORT_SYMBOL(replace_mount_options);
1301 #ifdef CONFIG_PROC_FS
1302 /* iterator; we want it to have access to namespace_sem, thus here... */
1303 static void *m_start(struct seq_file *m, loff_t *pos)
1305 struct proc_mounts *p = m->private;
1307 down_read(&namespace_sem);
1308 if (p->cached_event == p->ns->event) {
1309 void *v = p->cached_mount;
1310 if (*pos == p->cached_index)
1312 if (*pos == p->cached_index + 1) {
1313 v = seq_list_next(v, &p->ns->list, &p->cached_index);
1314 return p->cached_mount = v;
1318 p->cached_event = p->ns->event;
1319 p->cached_mount = seq_list_start(&p->ns->list, *pos);
1320 p->cached_index = *pos;
1321 return p->cached_mount;
1324 static void *m_next(struct seq_file *m, void *v, loff_t *pos)
1326 struct proc_mounts *p = m->private;
1328 p->cached_mount = seq_list_next(v, &p->ns->list, pos);
1329 p->cached_index = *pos;
1330 return p->cached_mount;
1333 static void m_stop(struct seq_file *m, void *v)
1335 up_read(&namespace_sem);
1338 static int m_show(struct seq_file *m, void *v)
1340 struct proc_mounts *p = m->private;
1341 struct mount *r = list_entry(v, struct mount, mnt_list);
1342 return p->show(m, &r->mnt);
1345 const struct seq_operations mounts_op = {
1351 #endif /* CONFIG_PROC_FS */
1354 * may_umount_tree - check if a mount tree is busy
1355 * @mnt: root of mount tree
1357 * This is called to check if a tree of mounts has any
1358 * open files, pwds, chroots or sub mounts that are
1361 int may_umount_tree(struct vfsmount *m)
1363 struct mount *mnt = real_mount(m);
1364 int actual_refs = 0;
1365 int minimum_refs = 0;
1369 /* write lock needed for mnt_get_count */
1371 for (p = mnt; p; p = next_mnt(p, mnt)) {
1372 actual_refs += mnt_get_count(p);
1375 unlock_mount_hash();
1377 if (actual_refs > minimum_refs)
1383 EXPORT_SYMBOL(may_umount_tree);
1386 * may_umount - check if a mount point is busy
1387 * @mnt: root of mount
1389 * This is called to check if a mount point has any
1390 * open files, pwds, chroots or sub mounts. If the
1391 * mount has sub mounts this will return busy
1392 * regardless of whether the sub mounts are busy.
1394 * Doesn't take quota and stuff into account. IOW, in some cases it will
1395 * give false negatives. The main reason why it's here is that we need
1396 * a non-destructive way to look for easily umountable filesystems.
1398 int may_umount(struct vfsmount *mnt)
1401 down_read(&namespace_sem);
1403 if (propagate_mount_busy(real_mount(mnt), 2))
1405 unlock_mount_hash();
1406 up_read(&namespace_sem);
1410 EXPORT_SYMBOL(may_umount);
1412 static HLIST_HEAD(unmounted); /* protected by namespace_sem */
1414 static void namespace_unlock(void)
1416 struct hlist_head head;
1418 hlist_move_list(&unmounted, &head);
1420 up_write(&namespace_sem);
1422 if (likely(hlist_empty(&head)))
1427 group_pin_kill(&head);
1430 static inline void namespace_lock(void)
1432 down_write(&namespace_sem);
1435 enum umount_tree_flags {
1437 UMOUNT_PROPAGATE = 2,
1438 UMOUNT_CONNECTED = 4,
1441 static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how)
1443 /* Leaving mounts connected is only valid for lazy umounts */
1444 if (how & UMOUNT_SYNC)
1447 /* A mount without a parent has nothing to be connected to */
1448 if (!mnt_has_parent(mnt))
1451 /* Because the reference counting rules change when mounts are
1452 * unmounted and connected, umounted mounts may not be
1453 * connected to mounted mounts.
1455 if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT))
1458 /* Has it been requested that the mount remain connected? */
1459 if (how & UMOUNT_CONNECTED)
1462 /* Is the mount locked such that it needs to remain connected? */
1463 if (IS_MNT_LOCKED(mnt))
1466 /* By default disconnect the mount */
1471 * mount_lock must be held
1472 * namespace_sem must be held for write
1474 static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
1476 LIST_HEAD(tmp_list);
1479 if (how & UMOUNT_PROPAGATE)
1480 propagate_mount_unlock(mnt);
1482 /* Gather the mounts to umount */
1483 for (p = mnt; p; p = next_mnt(p, mnt)) {
1484 p->mnt.mnt_flags |= MNT_UMOUNT;
1485 list_move(&p->mnt_list, &tmp_list);
1488 /* Hide the mounts from mnt_mounts */
1489 list_for_each_entry(p, &tmp_list, mnt_list) {
1490 list_del_init(&p->mnt_child);
1493 /* Add propogated mounts to the tmp_list */
1494 if (how & UMOUNT_PROPAGATE)
1495 propagate_umount(&tmp_list);
1497 while (!list_empty(&tmp_list)) {
1498 struct mnt_namespace *ns;
1500 p = list_first_entry(&tmp_list, struct mount, mnt_list);
1501 list_del_init(&p->mnt_expire);
1502 list_del_init(&p->mnt_list);
1506 __touch_mnt_namespace(ns);
1509 if (how & UMOUNT_SYNC)
1510 p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
1512 disconnect = disconnect_mount(p, how);
1514 pin_insert_group(&p->mnt_umount, &p->mnt_parent->mnt,
1515 disconnect ? &unmounted : NULL);
1516 if (mnt_has_parent(p)) {
1517 mnt_add_count(p->mnt_parent, -1);
1519 /* Don't forget about p */
1520 list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts);
1525 change_mnt_propagation(p, MS_PRIVATE);
1529 static void shrink_submounts(struct mount *mnt);
1531 static int do_umount(struct mount *mnt, int flags)
1533 struct super_block *sb = mnt->mnt.mnt_sb;
1536 retval = security_sb_umount(&mnt->mnt, flags);
1541 * Allow userspace to request a mountpoint be expired rather than
1542 * unmounting unconditionally. Unmount only happens if:
1543 * (1) the mark is already set (the mark is cleared by mntput())
1544 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1546 if (flags & MNT_EXPIRE) {
1547 if (&mnt->mnt == current->fs->root.mnt ||
1548 flags & (MNT_FORCE | MNT_DETACH))
1552 * probably don't strictly need the lock here if we examined
1553 * all race cases, but it's a slowpath.
1556 if (mnt_get_count(mnt) != 2) {
1557 unlock_mount_hash();
1560 unlock_mount_hash();
1562 if (!xchg(&mnt->mnt_expiry_mark, 1))
1567 * If we may have to abort operations to get out of this
1568 * mount, and they will themselves hold resources we must
1569 * allow the fs to do things. In the Unix tradition of
1570 * 'Gee thats tricky lets do it in userspace' the umount_begin
1571 * might fail to complete on the first run through as other tasks
1572 * must return, and the like. Thats for the mount program to worry
1573 * about for the moment.
1576 if (flags & MNT_FORCE && sb->s_op->umount_begin) {
1577 sb->s_op->umount_begin(sb);
1581 * No sense to grab the lock for this test, but test itself looks
1582 * somewhat bogus. Suggestions for better replacement?
1583 * Ho-hum... In principle, we might treat that as umount + switch
1584 * to rootfs. GC would eventually take care of the old vfsmount.
1585 * Actually it makes sense, especially if rootfs would contain a
1586 * /reboot - static binary that would close all descriptors and
1587 * call reboot(9). Then init(8) could umount root and exec /reboot.
1589 if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
1591 * Special case for "unmounting" root ...
1592 * we just try to remount it readonly.
1594 if (!capable(CAP_SYS_ADMIN))
1596 down_write(&sb->s_umount);
1597 if (!(sb->s_flags & MS_RDONLY))
1598 retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
1599 up_write(&sb->s_umount);
1606 /* Recheck MNT_LOCKED with the locks held */
1608 if (mnt->mnt.mnt_flags & MNT_LOCKED)
1612 if (flags & MNT_DETACH) {
1613 if (!list_empty(&mnt->mnt_list))
1614 umount_tree(mnt, UMOUNT_PROPAGATE);
1617 shrink_submounts(mnt);
1619 if (!propagate_mount_busy(mnt, 2)) {
1620 if (!list_empty(&mnt->mnt_list))
1621 umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
1626 unlock_mount_hash();
1628 if (retval == -EBUSY)
1629 global_filetable_delayed_print(mnt);
1634 * __detach_mounts - lazily unmount all mounts on the specified dentry
1636 * During unlink, rmdir, and d_drop it is possible to loose the path
1637 * to an existing mountpoint, and wind up leaking the mount.
1638 * detach_mounts allows lazily unmounting those mounts instead of
1641 * The caller may hold dentry->d_inode->i_mutex.
1643 void __detach_mounts(struct dentry *dentry)
1645 struct mountpoint *mp;
1650 mp = lookup_mountpoint(dentry);
1651 if (IS_ERR_OR_NULL(mp))
1655 while (!hlist_empty(&mp->m_list)) {
1656 mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list);
1657 if (mnt->mnt.mnt_flags & MNT_UMOUNT) {
1658 hlist_add_head(&mnt->mnt_umount.s_list, &unmounted);
1661 else umount_tree(mnt, UMOUNT_CONNECTED);
1665 unlock_mount_hash();
1670 * Is the caller allowed to modify his namespace?
1672 static inline bool may_mount(void)
1674 return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
1678 * Now umount can handle mount points as well as block devices.
1679 * This is important for filesystems which use unnamed block devices.
1681 * We now support a flag for forced unmount like the other 'big iron'
1682 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1685 SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1690 int lookup_flags = 0;
1692 if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
1698 if (!(flags & UMOUNT_NOFOLLOW))
1699 lookup_flags |= LOOKUP_FOLLOW;
1701 retval = user_path_mountpoint_at(AT_FDCWD, name, lookup_flags, &path);
1704 mnt = real_mount(path.mnt);
1706 if (path.dentry != path.mnt->mnt_root)
1708 if (!check_mnt(mnt))
1710 if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */
1713 if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))
1716 retval = do_umount(mnt, flags);
1718 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1720 mntput_no_expire(mnt);
1725 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1728 * The 2.0 compatible umount. No flags.
1730 SYSCALL_DEFINE1(oldumount, char __user *, name)
1732 return sys_umount(name, 0);
1737 static bool is_mnt_ns_file(struct dentry *dentry)
1739 /* Is this a proxy for a mount namespace? */
1740 return dentry->d_op == &ns_dentry_operations &&
1741 dentry->d_fsdata == &mntns_operations;
1744 struct mnt_namespace *to_mnt_ns(struct ns_common *ns)
1746 return container_of(ns, struct mnt_namespace, ns);
1749 static bool mnt_ns_loop(struct dentry *dentry)
1751 /* Could bind mounting the mount namespace inode cause a
1752 * mount namespace loop?
1754 struct mnt_namespace *mnt_ns;
1755 if (!is_mnt_ns_file(dentry))
1758 mnt_ns = to_mnt_ns(get_proc_ns(dentry->d_inode));
1759 return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
1762 struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
1765 struct mount *res, *p, *q, *r, *parent;
1767 if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt))
1768 return ERR_PTR(-EINVAL);
1770 if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
1771 return ERR_PTR(-EINVAL);
1773 res = q = clone_mnt(mnt, dentry, flag);
1777 q->mnt_mountpoint = mnt->mnt_mountpoint;
1780 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
1782 if (!is_subdir(r->mnt_mountpoint, dentry))
1785 for (s = r; s; s = next_mnt(s, r)) {
1786 if (!(flag & CL_COPY_UNBINDABLE) &&
1787 IS_MNT_UNBINDABLE(s)) {
1788 if (s->mnt.mnt_flags & MNT_LOCKED) {
1789 /* Both unbindable and locked. */
1790 q = ERR_PTR(-EPERM);
1793 s = skip_mnt_tree(s);
1797 if (!(flag & CL_COPY_MNT_NS_FILE) &&
1798 is_mnt_ns_file(s->mnt.mnt_root)) {
1799 s = skip_mnt_tree(s);
1802 while (p != s->mnt_parent) {
1808 q = clone_mnt(p, p->mnt.mnt_root, flag);
1812 list_add_tail(&q->mnt_list, &res->mnt_list);
1813 attach_mnt(q, parent, p->mnt_mp);
1814 unlock_mount_hash();
1821 umount_tree(res, UMOUNT_SYNC);
1822 unlock_mount_hash();
1827 /* Caller should check returned pointer for errors */
1829 struct vfsmount *collect_mounts(struct path *path)
1833 if (!check_mnt(real_mount(path->mnt)))
1834 tree = ERR_PTR(-EINVAL);
1836 tree = copy_tree(real_mount(path->mnt), path->dentry,
1837 CL_COPY_ALL | CL_PRIVATE);
1840 return ERR_CAST(tree);
1844 void drop_collected_mounts(struct vfsmount *mnt)
1848 umount_tree(real_mount(mnt), 0);
1849 unlock_mount_hash();
1854 * clone_private_mount - create a private clone of a path
1856 * This creates a new vfsmount, which will be the clone of @path. The new will
1857 * not be attached anywhere in the namespace and will be private (i.e. changes
1858 * to the originating mount won't be propagated into this).
1860 * Release with mntput().
1862 struct vfsmount *clone_private_mount(struct path *path)
1864 struct mount *old_mnt = real_mount(path->mnt);
1865 struct mount *new_mnt;
1867 if (IS_MNT_UNBINDABLE(old_mnt))
1868 return ERR_PTR(-EINVAL);
1870 down_read(&namespace_sem);
1871 new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE);
1872 up_read(&namespace_sem);
1873 if (IS_ERR(new_mnt))
1874 return ERR_CAST(new_mnt);
1876 return &new_mnt->mnt;
1878 EXPORT_SYMBOL_GPL(clone_private_mount);
1880 int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
1881 struct vfsmount *root)
1884 int res = f(root, arg);
1887 list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
1888 res = f(&mnt->mnt, arg);
1895 static void cleanup_group_ids(struct mount *mnt, struct mount *end)
1899 for (p = mnt; p != end; p = next_mnt(p, mnt)) {
1900 if (p->mnt_group_id && !IS_MNT_SHARED(p))
1901 mnt_release_group_id(p);
1905 static int invent_group_ids(struct mount *mnt, bool recurse)
1909 for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
1910 if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
1911 int err = mnt_alloc_group_id(p);
1913 cleanup_group_ids(mnt, p);
1922 int count_mounts(struct mnt_namespace *ns, struct mount *mnt)
1924 unsigned int max = READ_ONCE(sysctl_mount_max);
1925 unsigned int mounts = 0, old, pending, sum;
1928 for (p = mnt; p; p = next_mnt(p, mnt))
1932 pending = ns->pending_mounts;
1933 sum = old + pending;
1937 (mounts > (max - sum)))
1940 ns->pending_mounts = pending + mounts;
1945 * @source_mnt : mount tree to be attached
1946 * @nd : place the mount tree @source_mnt is attached
1947 * @parent_nd : if non-null, detach the source_mnt from its parent and
1948 * store the parent mount and mountpoint dentry.
1949 * (done when source_mnt is moved)
1951 * NOTE: in the table below explains the semantics when a source mount
1952 * of a given type is attached to a destination mount of a given type.
1953 * ---------------------------------------------------------------------------
1954 * | BIND MOUNT OPERATION |
1955 * |**************************************************************************
1956 * | source-->| shared | private | slave | unbindable |
1960 * |**************************************************************************
1961 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1963 * |non-shared| shared (+) | private | slave (*) | invalid |
1964 * ***************************************************************************
1965 * A bind operation clones the source mount and mounts the clone on the
1966 * destination mount.
1968 * (++) the cloned mount is propagated to all the mounts in the propagation
1969 * tree of the destination mount and the cloned mount is added to
1970 * the peer group of the source mount.
1971 * (+) the cloned mount is created under the destination mount and is marked
1972 * as shared. The cloned mount is added to the peer group of the source
1974 * (+++) the mount is propagated to all the mounts in the propagation tree
1975 * of the destination mount and the cloned mount is made slave
1976 * of the same master as that of the source mount. The cloned mount
1977 * is marked as 'shared and slave'.
1978 * (*) the cloned mount is made a slave of the same master as that of the
1981 * ---------------------------------------------------------------------------
1982 * | MOVE MOUNT OPERATION |
1983 * |**************************************************************************
1984 * | source-->| shared | private | slave | unbindable |
1988 * |**************************************************************************
1989 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1991 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1992 * ***************************************************************************
1994 * (+) the mount is moved to the destination. And is then propagated to
1995 * all the mounts in the propagation tree of the destination mount.
1996 * (+*) the mount is moved to the destination.
1997 * (+++) the mount is moved to the destination and is then propagated to
1998 * all the mounts belonging to the destination mount's propagation tree.
1999 * the mount is marked as 'shared and slave'.
2000 * (*) the mount continues to be a slave at the new location.
2002 * if the source mount is a tree, the operations explained above is
2003 * applied to each mount in the tree.
2004 * Must be called without spinlocks held, since this function can sleep
2007 static int attach_recursive_mnt(struct mount *source_mnt,
2008 struct mount *dest_mnt,
2009 struct mountpoint *dest_mp,
2010 struct path *parent_path)
2012 HLIST_HEAD(tree_list);
2013 struct mnt_namespace *ns = dest_mnt->mnt_ns;
2014 struct mountpoint *smp;
2015 struct mount *child, *p;
2016 struct hlist_node *n;
2019 /* Preallocate a mountpoint in case the new mounts need
2020 * to be tucked under other mounts.
2022 smp = get_mountpoint(source_mnt->mnt.mnt_root);
2024 return PTR_ERR(smp);
2026 /* Is there space to add these mounts to the mount namespace? */
2028 err = count_mounts(ns, source_mnt);
2033 if (IS_MNT_SHARED(dest_mnt)) {
2034 err = invent_group_ids(source_mnt, true);
2037 err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
2040 goto out_cleanup_ids;
2041 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
2047 detach_mnt(source_mnt, parent_path);
2048 attach_mnt(source_mnt, dest_mnt, dest_mp);
2049 touch_mnt_namespace(source_mnt->mnt_ns);
2051 mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
2052 commit_tree(source_mnt);
2055 hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) {
2057 hlist_del_init(&child->mnt_hash);
2058 q = __lookup_mnt(&child->mnt_parent->mnt,
2059 child->mnt_mountpoint);
2061 mnt_change_mountpoint(child, smp, q);
2064 put_mountpoint(smp);
2065 unlock_mount_hash();
2070 while (!hlist_empty(&tree_list)) {
2071 child = hlist_entry(tree_list.first, struct mount, mnt_hash);
2072 child->mnt_parent->mnt_ns->pending_mounts = 0;
2073 umount_tree(child, UMOUNT_SYNC);
2075 unlock_mount_hash();
2076 cleanup_group_ids(source_mnt, NULL);
2078 ns->pending_mounts = 0;
2080 read_seqlock_excl(&mount_lock);
2081 put_mountpoint(smp);
2082 read_sequnlock_excl(&mount_lock);
2087 static struct mountpoint *lock_mount(struct path *path)
2089 struct vfsmount *mnt;
2090 struct dentry *dentry = path->dentry;
2092 mutex_lock(&dentry->d_inode->i_mutex);
2093 if (unlikely(cant_mount(dentry))) {
2094 mutex_unlock(&dentry->d_inode->i_mutex);
2095 return ERR_PTR(-ENOENT);
2098 mnt = lookup_mnt(path);
2100 struct mountpoint *mp = get_mountpoint(dentry);
2103 mutex_unlock(&dentry->d_inode->i_mutex);
2109 mutex_unlock(&path->dentry->d_inode->i_mutex);
2112 dentry = path->dentry = dget(mnt->mnt_root);
2116 static void unlock_mount(struct mountpoint *where)
2118 struct dentry *dentry = where->m_dentry;
2120 read_seqlock_excl(&mount_lock);
2121 put_mountpoint(where);
2122 read_sequnlock_excl(&mount_lock);
2125 mutex_unlock(&dentry->d_inode->i_mutex);
2128 static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
2130 if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER)
2133 if (d_is_dir(mp->m_dentry) !=
2134 d_is_dir(mnt->mnt.mnt_root))
2137 return attach_recursive_mnt(mnt, p, mp, NULL);
2141 * Sanity check the flags to change_mnt_propagation.
2144 static int flags_to_propagation_type(int flags)
2146 int type = flags & ~(MS_REC | MS_SILENT);
2148 /* Fail if any non-propagation flags are set */
2149 if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2151 /* Only one propagation flag should be set */
2152 if (!is_power_of_2(type))
2158 * recursively change the type of the mountpoint.
2160 static int do_change_type(struct path *path, int flag)
2163 struct mount *mnt = real_mount(path->mnt);
2164 int recurse = flag & MS_REC;
2168 if (path->dentry != path->mnt->mnt_root)
2171 type = flags_to_propagation_type(flag);
2176 if (type == MS_SHARED) {
2177 err = invent_group_ids(mnt, recurse);
2183 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
2184 change_mnt_propagation(m, type);
2185 unlock_mount_hash();
2192 static bool has_locked_children(struct mount *mnt, struct dentry *dentry)
2194 struct mount *child;
2195 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
2196 if (!is_subdir(child->mnt_mountpoint, dentry))
2199 if (child->mnt.mnt_flags & MNT_LOCKED)
2206 * do loopback mount.
2208 static int do_loopback(struct path *path, const char *old_name,
2211 struct path old_path;
2212 struct mount *mnt = NULL, *old, *parent;
2213 struct mountpoint *mp;
2215 if (!old_name || !*old_name)
2217 err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
2222 if (mnt_ns_loop(old_path.dentry))
2225 mp = lock_mount(path);
2230 old = real_mount(old_path.mnt);
2231 parent = real_mount(path->mnt);
2234 if (IS_MNT_UNBINDABLE(old))
2237 if (!check_mnt(parent))
2240 if (!check_mnt(old) && old_path.dentry->d_op != &ns_dentry_operations)
2243 if (!recurse && has_locked_children(old, old_path.dentry))
2247 mnt = copy_tree(old, old_path.dentry, CL_COPY_MNT_NS_FILE);
2249 mnt = clone_mnt(old, old_path.dentry, 0);
2256 mnt->mnt.mnt_flags &= ~MNT_LOCKED;
2258 err = graft_tree(mnt, parent, mp);
2261 umount_tree(mnt, UMOUNT_SYNC);
2262 unlock_mount_hash();
2267 path_put(&old_path);
2271 static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
2274 int readonly_request = 0;
2276 if (ms_flags & MS_RDONLY)
2277 readonly_request = 1;
2278 if (readonly_request == __mnt_is_readonly(mnt))
2281 if (readonly_request)
2282 error = mnt_make_readonly(real_mount(mnt));
2284 __mnt_unmake_readonly(real_mount(mnt));
2289 * change filesystem flags. dir should be a physical root of filesystem.
2290 * If you've mounted a non-root directory somewhere and want to do remount
2291 * on it - tough luck.
2293 static int do_remount(struct path *path, int flags, int mnt_flags,
2297 struct super_block *sb = path->mnt->mnt_sb;
2298 struct mount *mnt = real_mount(path->mnt);
2300 if (!check_mnt(mnt))
2303 if (path->dentry != path->mnt->mnt_root)
2306 /* Don't allow changing of locked mnt flags.
2308 * No locks need to be held here while testing the various
2309 * MNT_LOCK flags because those flags can never be cleared
2310 * once they are set.
2312 if ((mnt->mnt.mnt_flags & MNT_LOCK_READONLY) &&
2313 !(mnt_flags & MNT_READONLY)) {
2316 if ((mnt->mnt.mnt_flags & MNT_LOCK_NODEV) &&
2317 !(mnt_flags & MNT_NODEV)) {
2318 /* Was the nodev implicitly added in mount? */
2319 if ((mnt->mnt_ns->user_ns != &init_user_ns) &&
2320 !(sb->s_type->fs_flags & FS_USERNS_DEV_MOUNT)) {
2321 mnt_flags |= MNT_NODEV;
2326 if ((mnt->mnt.mnt_flags & MNT_LOCK_NOSUID) &&
2327 !(mnt_flags & MNT_NOSUID)) {
2330 if ((mnt->mnt.mnt_flags & MNT_LOCK_NOEXEC) &&
2331 !(mnt_flags & MNT_NOEXEC)) {
2334 if ((mnt->mnt.mnt_flags & MNT_LOCK_ATIME) &&
2335 ((mnt->mnt.mnt_flags & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK))) {
2339 err = security_sb_remount(sb, data);
2343 down_write(&sb->s_umount);
2344 if (flags & MS_BIND)
2345 err = change_mount_flags(path->mnt, flags);
2346 else if (!capable(CAP_SYS_ADMIN))
2349 err = do_remount_sb2(path->mnt, sb, flags, data, 0);
2352 propagate_remount(mnt);
2353 unlock_mount_hash();
2358 mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;
2359 mnt->mnt.mnt_flags = mnt_flags;
2360 touch_mnt_namespace(mnt->mnt_ns);
2361 unlock_mount_hash();
2363 up_write(&sb->s_umount);
2367 static inline int tree_contains_unbindable(struct mount *mnt)
2370 for (p = mnt; p; p = next_mnt(p, mnt)) {
2371 if (IS_MNT_UNBINDABLE(p))
2377 static int do_move_mount(struct path *path, const char *old_name)
2379 struct path old_path, parent_path;
2382 struct mountpoint *mp;
2384 if (!old_name || !*old_name)
2386 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
2390 mp = lock_mount(path);
2395 old = real_mount(old_path.mnt);
2396 p = real_mount(path->mnt);
2399 if (!check_mnt(p) || !check_mnt(old))
2402 if (old->mnt.mnt_flags & MNT_LOCKED)
2406 if (old_path.dentry != old_path.mnt->mnt_root)
2409 if (!mnt_has_parent(old))
2412 if (d_is_dir(path->dentry) !=
2413 d_is_dir(old_path.dentry))
2416 * Don't move a mount residing in a shared parent.
2418 if (IS_MNT_SHARED(old->mnt_parent))
2421 * Don't move a mount tree containing unbindable mounts to a destination
2422 * mount which is shared.
2424 if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
2427 for (; mnt_has_parent(p); p = p->mnt_parent)
2431 err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path);
2435 /* if the mount is moved, it should no longer be expire
2437 list_del_init(&old->mnt_expire);
2442 path_put(&parent_path);
2443 path_put(&old_path);
2447 static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
2450 const char *subtype = strchr(fstype, '.');
2459 mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
2461 if (!mnt->mnt_sb->s_subtype)
2467 return ERR_PTR(err);
2471 * add a mount into a namespace's mount tree
2473 static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
2475 struct mountpoint *mp;
2476 struct mount *parent;
2479 mnt_flags &= ~MNT_INTERNAL_FLAGS;
2481 mp = lock_mount(path);
2485 parent = real_mount(path->mnt);
2487 if (unlikely(!check_mnt(parent))) {
2488 /* that's acceptable only for automounts done in private ns */
2489 if (!(mnt_flags & MNT_SHRINKABLE))
2491 /* ... and for those we'd better have mountpoint still alive */
2492 if (!parent->mnt_ns)
2496 /* Refuse the same filesystem on the same mount point */
2498 if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb &&
2499 path->mnt->mnt_root == path->dentry)
2503 if (d_is_symlink(newmnt->mnt.mnt_root))
2506 newmnt->mnt.mnt_flags = mnt_flags;
2507 err = graft_tree(newmnt, parent, mp);
2514 static bool fs_fully_visible(struct file_system_type *fs_type, int *new_mnt_flags);
2517 * create a new mount for userspace and request it to be added into the
2520 static int do_new_mount(struct path *path, const char *fstype, int flags,
2521 int mnt_flags, const char *name, void *data)
2523 struct file_system_type *type;
2524 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2525 struct vfsmount *mnt;
2531 type = get_fs_type(fstype);
2535 if (user_ns != &init_user_ns) {
2536 if (!(type->fs_flags & FS_USERNS_MOUNT)) {
2537 put_filesystem(type);
2540 /* Only in special cases allow devices from mounts
2541 * created outside the initial user namespace.
2543 if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) {
2545 mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV;
2547 if (type->fs_flags & FS_USERNS_VISIBLE) {
2548 if (!fs_fully_visible(type, &mnt_flags)) {
2549 put_filesystem(type);
2555 mnt = vfs_kern_mount(type, flags, name, data);
2556 if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
2557 !mnt->mnt_sb->s_subtype)
2558 mnt = fs_set_subtype(mnt, fstype);
2560 put_filesystem(type);
2562 return PTR_ERR(mnt);
2564 err = do_add_mount(real_mount(mnt), path, mnt_flags);
2570 int finish_automount(struct vfsmount *m, struct path *path)
2572 struct mount *mnt = real_mount(m);
2574 /* The new mount record should have at least 2 refs to prevent it being
2575 * expired before we get a chance to add it
2577 BUG_ON(mnt_get_count(mnt) < 2);
2579 if (m->mnt_sb == path->mnt->mnt_sb &&
2580 m->mnt_root == path->dentry) {
2585 err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
2589 /* remove m from any expiration list it may be on */
2590 if (!list_empty(&mnt->mnt_expire)) {
2592 list_del_init(&mnt->mnt_expire);
2601 * mnt_set_expiry - Put a mount on an expiration list
2602 * @mnt: The mount to list.
2603 * @expiry_list: The list to add the mount to.
2605 void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
2609 list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
2613 EXPORT_SYMBOL(mnt_set_expiry);
2616 * process a list of expirable mountpoints with the intent of discarding any
2617 * mountpoints that aren't in use and haven't been touched since last we came
2620 void mark_mounts_for_expiry(struct list_head *mounts)
2622 struct mount *mnt, *next;
2623 LIST_HEAD(graveyard);
2625 if (list_empty(mounts))
2631 /* extract from the expiration list every vfsmount that matches the
2632 * following criteria:
2633 * - only referenced by its parent vfsmount
2634 * - still marked for expiry (marked on the last call here; marks are
2635 * cleared by mntput())
2637 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
2638 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
2639 propagate_mount_busy(mnt, 1))
2641 list_move(&mnt->mnt_expire, &graveyard);
2643 while (!list_empty(&graveyard)) {
2644 mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
2645 touch_mnt_namespace(mnt->mnt_ns);
2646 umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
2648 unlock_mount_hash();
2652 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
2655 * Ripoff of 'select_parent()'
2657 * search the list of submounts for a given mountpoint, and move any
2658 * shrinkable submounts to the 'graveyard' list.
2660 static int select_submounts(struct mount *parent, struct list_head *graveyard)
2662 struct mount *this_parent = parent;
2663 struct list_head *next;
2667 next = this_parent->mnt_mounts.next;
2669 while (next != &this_parent->mnt_mounts) {
2670 struct list_head *tmp = next;
2671 struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
2674 if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
2677 * Descend a level if the d_mounts list is non-empty.
2679 if (!list_empty(&mnt->mnt_mounts)) {
2684 if (!propagate_mount_busy(mnt, 1)) {
2685 list_move_tail(&mnt->mnt_expire, graveyard);
2690 * All done at this level ... ascend and resume the search
2692 if (this_parent != parent) {
2693 next = this_parent->mnt_child.next;
2694 this_parent = this_parent->mnt_parent;
2701 * process a list of expirable mountpoints with the intent of discarding any
2702 * submounts of a specific parent mountpoint
2704 * mount_lock must be held for write
2706 static void shrink_submounts(struct mount *mnt)
2708 LIST_HEAD(graveyard);
2711 /* extract submounts of 'mountpoint' from the expiration list */
2712 while (select_submounts(mnt, &graveyard)) {
2713 while (!list_empty(&graveyard)) {
2714 m = list_first_entry(&graveyard, struct mount,
2716 touch_mnt_namespace(m->mnt_ns);
2717 umount_tree(m, UMOUNT_PROPAGATE|UMOUNT_SYNC);
2723 * Some copy_from_user() implementations do not return the exact number of
2724 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2725 * Note that this function differs from copy_from_user() in that it will oops
2726 * on bad values of `to', rather than returning a short copy.
2728 static long exact_copy_from_user(void *to, const void __user * from,
2732 const char __user *f = from;
2735 if (!access_ok(VERIFY_READ, from, n))
2739 if (__get_user(c, f)) {
2750 int copy_mount_options(const void __user * data, unsigned long *where)
2760 if (!(page = __get_free_page(GFP_KERNEL)))
2763 /* We only care that *some* data at the address the user
2764 * gave us is valid. Just in case, we'll zero
2765 * the remainder of the page.
2767 /* copy_from_user cannot cross TASK_SIZE ! */
2768 size = TASK_SIZE - (unsigned long)data;
2769 if (size > PAGE_SIZE)
2772 i = size - exact_copy_from_user((void *)page, data, size);
2778 memset((char *)page + i, 0, PAGE_SIZE - i);
2783 char *copy_mount_string(const void __user *data)
2785 return data ? strndup_user(data, PAGE_SIZE) : NULL;
2789 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2790 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2792 * data is a (void *) that can point to any structure up to
2793 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2794 * information (or be NULL).
2796 * Pre-0.97 versions of mount() didn't have a flags word.
2797 * When the flags word was introduced its top half was required
2798 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2799 * Therefore, if this magic number is present, it carries no information
2800 * and must be discarded.
2802 long do_mount(const char *dev_name, const char __user *dir_name,
2803 const char *type_page, unsigned long flags, void *data_page)
2810 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
2811 flags &= ~MS_MGC_MSK;
2813 /* Basic sanity checks */
2815 ((char *)data_page)[PAGE_SIZE - 1] = 0;
2817 /* ... and get the mountpoint */
2818 retval = user_path(dir_name, &path);
2822 retval = security_sb_mount(dev_name, &path,
2823 type_page, flags, data_page);
2824 if (!retval && !may_mount())
2829 /* Default to relatime unless overriden */
2830 if (!(flags & MS_NOATIME))
2831 mnt_flags |= MNT_RELATIME;
2833 /* Separate the per-mountpoint flags */
2834 if (flags & MS_NOSUID)
2835 mnt_flags |= MNT_NOSUID;
2836 if (flags & MS_NODEV)
2837 mnt_flags |= MNT_NODEV;
2838 if (flags & MS_NOEXEC)
2839 mnt_flags |= MNT_NOEXEC;
2840 if (flags & MS_NOATIME)
2841 mnt_flags |= MNT_NOATIME;
2842 if (flags & MS_NODIRATIME)
2843 mnt_flags |= MNT_NODIRATIME;
2844 if (flags & MS_STRICTATIME)
2845 mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
2846 if (flags & MS_RDONLY)
2847 mnt_flags |= MNT_READONLY;
2849 /* The default atime for remount is preservation */
2850 if ((flags & MS_REMOUNT) &&
2851 ((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME |
2852 MS_STRICTATIME)) == 0)) {
2853 mnt_flags &= ~MNT_ATIME_MASK;
2854 mnt_flags |= path.mnt->mnt_flags & MNT_ATIME_MASK;
2857 flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN |
2858 MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
2861 if (flags & MS_REMOUNT)
2862 retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
2864 else if (flags & MS_BIND)
2865 retval = do_loopback(&path, dev_name, flags & MS_REC);
2866 else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2867 retval = do_change_type(&path, flags);
2868 else if (flags & MS_MOVE)
2869 retval = do_move_mount(&path, dev_name);
2871 retval = do_new_mount(&path, type_page, flags, mnt_flags,
2872 dev_name, data_page);
2878 static void free_mnt_ns(struct mnt_namespace *ns)
2880 ns_free_inum(&ns->ns);
2881 put_user_ns(ns->user_ns);
2886 * Assign a sequence number so we can detect when we attempt to bind
2887 * mount a reference to an older mount namespace into the current
2888 * mount namespace, preventing reference counting loops. A 64bit
2889 * number incrementing at 10Ghz will take 12,427 years to wrap which
2890 * is effectively never, so we can ignore the possibility.
2892 static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
2894 static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
2896 struct mnt_namespace *new_ns;
2899 new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
2901 return ERR_PTR(-ENOMEM);
2902 ret = ns_alloc_inum(&new_ns->ns);
2905 return ERR_PTR(ret);
2907 new_ns->ns.ops = &mntns_operations;
2908 new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
2909 atomic_set(&new_ns->count, 1);
2910 new_ns->root = NULL;
2911 INIT_LIST_HEAD(&new_ns->list);
2912 init_waitqueue_head(&new_ns->poll);
2914 new_ns->user_ns = get_user_ns(user_ns);
2916 new_ns->pending_mounts = 0;
2920 struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
2921 struct user_namespace *user_ns, struct fs_struct *new_fs)
2923 struct mnt_namespace *new_ns;
2924 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
2925 struct mount *p, *q;
2932 if (likely(!(flags & CLONE_NEWNS))) {
2939 new_ns = alloc_mnt_ns(user_ns);
2944 /* First pass: copy the tree topology */
2945 copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
2946 if (user_ns != ns->user_ns)
2947 copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED;
2948 new = copy_tree(old, old->mnt.mnt_root, copy_flags);
2951 free_mnt_ns(new_ns);
2952 return ERR_CAST(new);
2955 list_add_tail(&new_ns->list, &new->mnt_list);
2958 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2959 * as belonging to new namespace. We have already acquired a private
2960 * fs_struct, so tsk->fs->lock is not needed.
2968 if (&p->mnt == new_fs->root.mnt) {
2969 new_fs->root.mnt = mntget(&q->mnt);
2972 if (&p->mnt == new_fs->pwd.mnt) {
2973 new_fs->pwd.mnt = mntget(&q->mnt);
2977 p = next_mnt(p, old);
2978 q = next_mnt(q, new);
2981 while (p->mnt.mnt_root != q->mnt.mnt_root)
2982 p = next_mnt(p, old);
2995 * create_mnt_ns - creates a private namespace and adds a root filesystem
2996 * @mnt: pointer to the new root filesystem mountpoint
2998 static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
3000 struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns);
3001 if (!IS_ERR(new_ns)) {
3002 struct mount *mnt = real_mount(m);
3003 mnt->mnt_ns = new_ns;
3006 list_add(&mnt->mnt_list, &new_ns->list);
3013 struct dentry *mount_subtree(struct vfsmount *mnt, const char *name)
3015 struct mnt_namespace *ns;
3016 struct super_block *s;
3020 ns = create_mnt_ns(mnt);
3022 return ERR_CAST(ns);
3024 err = vfs_path_lookup(mnt->mnt_root, mnt,
3025 name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
3030 return ERR_PTR(err);
3032 /* trade a vfsmount reference for active sb one */
3033 s = path.mnt->mnt_sb;
3034 atomic_inc(&s->s_active);
3036 /* lock the sucker */
3037 down_write(&s->s_umount);
3038 /* ... and return the root of (sub)tree on it */
3041 EXPORT_SYMBOL(mount_subtree);
3043 SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
3044 char __user *, type, unsigned long, flags, void __user *, data)
3049 unsigned long data_page;
3051 kernel_type = copy_mount_string(type);
3052 ret = PTR_ERR(kernel_type);
3053 if (IS_ERR(kernel_type))
3056 kernel_dev = copy_mount_string(dev_name);
3057 ret = PTR_ERR(kernel_dev);
3058 if (IS_ERR(kernel_dev))
3061 ret = copy_mount_options(data, &data_page);
3065 ret = do_mount(kernel_dev, dir_name, kernel_type, flags,
3066 (void *) data_page);
3068 free_page(data_page);
3078 * Return true if path is reachable from root
3080 * namespace_sem or mount_lock is held
3082 bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
3083 const struct path *root)
3085 while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
3086 dentry = mnt->mnt_mountpoint;
3087 mnt = mnt->mnt_parent;
3089 return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
3092 int path_is_under(struct path *path1, struct path *path2)
3095 read_seqlock_excl(&mount_lock);
3096 res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2);
3097 read_sequnlock_excl(&mount_lock);
3100 EXPORT_SYMBOL(path_is_under);
3103 * pivot_root Semantics:
3104 * Moves the root file system of the current process to the directory put_old,
3105 * makes new_root as the new root file system of the current process, and sets
3106 * root/cwd of all processes which had them on the current root to new_root.
3109 * The new_root and put_old must be directories, and must not be on the
3110 * same file system as the current process root. The put_old must be
3111 * underneath new_root, i.e. adding a non-zero number of /.. to the string
3112 * pointed to by put_old must yield the same directory as new_root. No other
3113 * file system may be mounted on put_old. After all, new_root is a mountpoint.
3115 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
3116 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
3117 * in this situation.
3120 * - we don't move root/cwd if they are not at the root (reason: if something
3121 * cared enough to change them, it's probably wrong to force them elsewhere)
3122 * - it's okay to pick a root that isn't the root of a file system, e.g.
3123 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
3124 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
3127 SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
3128 const char __user *, put_old)
3130 struct path new, old, parent_path, root_parent, root;
3131 struct mount *new_mnt, *root_mnt, *old_mnt;
3132 struct mountpoint *old_mp, *root_mp;
3138 error = user_path_dir(new_root, &new);
3142 error = user_path_dir(put_old, &old);
3146 error = security_sb_pivotroot(&old, &new);
3150 get_fs_root(current->fs, &root);
3151 old_mp = lock_mount(&old);
3152 error = PTR_ERR(old_mp);
3157 new_mnt = real_mount(new.mnt);
3158 root_mnt = real_mount(root.mnt);
3159 old_mnt = real_mount(old.mnt);
3160 if (IS_MNT_SHARED(old_mnt) ||
3161 IS_MNT_SHARED(new_mnt->mnt_parent) ||
3162 IS_MNT_SHARED(root_mnt->mnt_parent))
3164 if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
3166 if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
3169 if (d_unlinked(new.dentry))
3172 if (new_mnt == root_mnt || old_mnt == root_mnt)
3173 goto out4; /* loop, on the same file system */
3175 if (root.mnt->mnt_root != root.dentry)
3176 goto out4; /* not a mountpoint */
3177 if (!mnt_has_parent(root_mnt))
3178 goto out4; /* not attached */
3179 root_mp = root_mnt->mnt_mp;
3180 if (new.mnt->mnt_root != new.dentry)
3181 goto out4; /* not a mountpoint */
3182 if (!mnt_has_parent(new_mnt))
3183 goto out4; /* not attached */
3184 /* make sure we can reach put_old from new_root */
3185 if (!is_path_reachable(old_mnt, old.dentry, &new))
3187 /* make certain new is below the root */
3188 if (!is_path_reachable(new_mnt, new.dentry, &root))
3190 root_mp->m_count++; /* pin it so it won't go away */
3192 detach_mnt(new_mnt, &parent_path);
3193 detach_mnt(root_mnt, &root_parent);
3194 if (root_mnt->mnt.mnt_flags & MNT_LOCKED) {
3195 new_mnt->mnt.mnt_flags |= MNT_LOCKED;
3196 root_mnt->mnt.mnt_flags &= ~MNT_LOCKED;
3198 /* mount old root on put_old */
3199 attach_mnt(root_mnt, old_mnt, old_mp);
3200 /* mount new_root on / */
3201 attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp);
3202 touch_mnt_namespace(current->nsproxy->mnt_ns);
3203 /* A moved mount should not expire automatically */
3204 list_del_init(&new_mnt->mnt_expire);
3205 put_mountpoint(root_mp);
3206 unlock_mount_hash();
3207 chroot_fs_refs(&root, &new);
3210 unlock_mount(old_mp);
3212 path_put(&root_parent);
3213 path_put(&parent_path);
3225 static void __init init_mount_tree(void)
3227 struct vfsmount *mnt;
3228 struct mnt_namespace *ns;
3230 struct file_system_type *type;
3232 type = get_fs_type("rootfs");
3234 panic("Can't find rootfs type");
3235 mnt = vfs_kern_mount(type, 0, "rootfs", NULL);
3236 put_filesystem(type);
3238 panic("Can't create rootfs");
3240 ns = create_mnt_ns(mnt);
3242 panic("Can't allocate initial namespace");
3244 init_task.nsproxy->mnt_ns = ns;
3248 root.dentry = mnt->mnt_root;
3249 mnt->mnt_flags |= MNT_LOCKED;
3251 set_fs_pwd(current->fs, &root);
3252 set_fs_root(current->fs, &root);
3255 void __init mnt_init(void)
3260 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
3261 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
3263 mount_hashtable = alloc_large_system_hash("Mount-cache",
3264 sizeof(struct hlist_head),
3267 &m_hash_shift, &m_hash_mask, 0, 0);
3268 mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache",
3269 sizeof(struct hlist_head),
3272 &mp_hash_shift, &mp_hash_mask, 0, 0);
3274 if (!mount_hashtable || !mountpoint_hashtable)
3275 panic("Failed to allocate mount hash table\n");
3277 for (u = 0; u <= m_hash_mask; u++)
3278 INIT_HLIST_HEAD(&mount_hashtable[u]);
3279 for (u = 0; u <= mp_hash_mask; u++)
3280 INIT_HLIST_HEAD(&mountpoint_hashtable[u]);
3286 printk(KERN_WARNING "%s: sysfs_init error: %d\n",
3288 fs_kobj = kobject_create_and_add("fs", NULL);
3290 printk(KERN_WARNING "%s: kobj create error\n", __func__);
3295 void put_mnt_ns(struct mnt_namespace *ns)
3297 if (!atomic_dec_and_test(&ns->count))
3299 drop_collected_mounts(&ns->root->mnt);
3303 struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
3305 struct vfsmount *mnt;
3306 mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
3309 * it is a longterm mount, don't release mnt until
3310 * we unmount before file sys is unregistered
3312 real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
3316 EXPORT_SYMBOL_GPL(kern_mount_data);
3318 void kern_unmount(struct vfsmount *mnt)
3320 /* release long term mount so mount point can be released */
3321 if (!IS_ERR_OR_NULL(mnt)) {
3322 real_mount(mnt)->mnt_ns = NULL;
3323 synchronize_rcu(); /* yecchhh... */
3327 EXPORT_SYMBOL(kern_unmount);
3329 bool our_mnt(struct vfsmount *mnt)
3331 return check_mnt(real_mount(mnt));
3334 bool current_chrooted(void)
3336 /* Does the current process have a non-standard root */
3337 struct path ns_root;
3338 struct path fs_root;
3341 /* Find the namespace root */
3342 ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt;
3343 ns_root.dentry = ns_root.mnt->mnt_root;
3345 while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root))
3348 get_fs_root(current->fs, &fs_root);
3350 chrooted = !path_equal(&fs_root, &ns_root);
3358 static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags)
3360 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
3361 int new_flags = *new_mnt_flags;
3363 bool visible = false;
3368 down_read(&namespace_sem);
3369 list_for_each_entry(mnt, &ns->list, mnt_list) {
3370 struct mount *child;
3373 if (mnt->mnt.mnt_sb->s_type != type)
3376 /* This mount is not fully visible if it's root directory
3377 * is not the root directory of the filesystem.
3379 if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root)
3382 /* Read the mount flags and filter out flags that
3383 * may safely be ignored.
3385 mnt_flags = mnt->mnt.mnt_flags;
3386 if (mnt->mnt.mnt_sb->s_iflags & SB_I_NOEXEC)
3387 mnt_flags &= ~(MNT_LOCK_NOSUID | MNT_LOCK_NOEXEC);
3389 /* Don't miss readonly hidden in the superblock flags */
3390 if (mnt->mnt.mnt_sb->s_flags & MS_RDONLY)
3391 mnt_flags |= MNT_LOCK_READONLY;
3393 /* Verify the mount flags are equal to or more permissive
3394 * than the proposed new mount.
3396 if ((mnt_flags & MNT_LOCK_READONLY) &&
3397 !(new_flags & MNT_READONLY))
3399 if ((mnt_flags & MNT_LOCK_NODEV) &&
3400 !(new_flags & MNT_NODEV))
3402 if ((mnt_flags & MNT_LOCK_NOSUID) &&
3403 !(new_flags & MNT_NOSUID))
3405 if ((mnt_flags & MNT_LOCK_NOEXEC) &&
3406 !(new_flags & MNT_NOEXEC))
3408 if ((mnt_flags & MNT_LOCK_ATIME) &&
3409 ((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK)))
3412 /* This mount is not fully visible if there are any
3413 * locked child mounts that cover anything except for
3414 * empty directories.
3416 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
3417 struct inode *inode = child->mnt_mountpoint->d_inode;
3418 /* Only worry about locked mounts */
3419 if (!(child->mnt.mnt_flags & MNT_LOCKED))
3421 /* Is the directory permanetly empty? */
3422 if (!is_empty_dir_inode(inode))
3425 /* Preserve the locked attributes */
3426 *new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \
3436 up_read(&namespace_sem);
3440 static struct ns_common *mntns_get(struct task_struct *task)
3442 struct ns_common *ns = NULL;
3443 struct nsproxy *nsproxy;
3446 nsproxy = task->nsproxy;
3448 ns = &nsproxy->mnt_ns->ns;
3449 get_mnt_ns(to_mnt_ns(ns));
3456 static void mntns_put(struct ns_common *ns)
3458 put_mnt_ns(to_mnt_ns(ns));
3461 static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns)
3463 struct fs_struct *fs = current->fs;
3464 struct mnt_namespace *mnt_ns = to_mnt_ns(ns);
3467 if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
3468 !ns_capable(current_user_ns(), CAP_SYS_CHROOT) ||
3469 !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
3476 put_mnt_ns(nsproxy->mnt_ns);
3477 nsproxy->mnt_ns = mnt_ns;
3480 root.mnt = &mnt_ns->root->mnt;
3481 root.dentry = mnt_ns->root->mnt.mnt_root;
3483 while(d_mountpoint(root.dentry) && follow_down_one(&root))
3486 /* Update the pwd and root */
3487 set_fs_pwd(fs, &root);
3488 set_fs_root(fs, &root);
3494 const struct proc_ns_operations mntns_operations = {
3496 .type = CLONE_NEWNS,
3499 .install = mntns_install,