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Commit 5d88457e authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

mnt: On an unmount propagate clearing of MNT_LOCKED 



A prerequisite of calling umount_tree is that the point where the tree
is mounted at is valid to unmount.

If we are propagating the effect of the unmount clear MNT_LOCKED in
every instance where the same filesystem is mounted on the same
mountpoint in the mount tree, as we know (by virtue of the fact
that umount_tree was called) that it is safe to reveal what
is at that mountpoint.

Cc: stable@vger.kernel.org
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
parent 411a938b

fs/namespace.c

+3 −0
Original line number Diff line number Diff line
@@ -1333,6 +1333,9 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how) 
	LIST_HEAD(tmp_list);

	struct mount *p;



	if (how & UMOUNT_PROPAGATE)

		propagate_mount_unlock(mnt);



	/* Gather the mounts to umount */

	for (p = mnt; p; p = next_mnt(p, mnt)) {

		p->mnt.mnt_flags |= MNT_UMOUNT;

fs/pnode.c

+20 −0
Original line number Diff line number Diff line
@@ -361,6 +361,26 @@ int propagate_mount_busy(struct mount *mnt, int refcnt) 
	return ret;

}



/*

 * Clear MNT_LOCKED when it can be shown to be safe.

 *

 * mount_lock lock must be held for write

 */

void propagate_mount_unlock(struct mount *mnt)

{

	struct mount *parent = mnt->mnt_parent;

	struct mount *m, *child;



	BUG_ON(parent == mnt);



	for (m = propagation_next(parent, parent); m;

			m = propagation_next(m, parent)) {

		child = __lookup_mnt_last(&m->mnt, mnt->mnt_mountpoint);

		if (child)

			child->mnt.mnt_flags &= ~MNT_LOCKED;

	}

}



/*

 * NOTE: unmounting 'mnt' naturally propagates to all other mounts its

 * parent propagates to.

fs/pnode.h

+1 −0
Original line number Diff line number Diff line
@@ -42,6 +42,7 @@ int propagate_mnt(struct mount *, struct mountpoint *, struct mount *, 
		struct hlist_head *);

int propagate_umount(struct list_head *);

int propagate_mount_busy(struct mount *, int);

void propagate_mount_unlock(struct mount *);

void mnt_release_group_id(struct mount *);

int get_dominating_id(struct mount *mnt, const struct path *root);

unsigned int mnt_get_count(struct mount *mnt);