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@xxxxxxxxxxxxxxx
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
---
fs/namespace.c | 3 +++
fs/pnode.c | 20 ++++++++++++++++++++
fs/pnode.h | 1 +
3 files changed, 24 insertions(+)
diff --git a/fs/namespace.c b/fs/namespace.c
index 3769dbd040c1..ca801b41c643 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1344,6 +1344,9 @@ 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;
diff --git a/fs/pnode.c b/fs/pnode.c
index c27ae38ee250..89890293dd0a 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -362,6 +362,26 @@ int propagate_mount_busy(struct mount *mnt, int refcnt)
}
/*
+ * 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.
*/
diff --git a/fs/pnode.h b/fs/pnode.h
index aa6d65df7204..af47d4bd7b31 100644
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -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);
--
2.2.1
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