vfs: umount_tree() might be called on subtree that had never made it

commit 63d37a84ab6004c235314ffd7a76c5eb28c2fae0 upstream.

__mnt_make_shortterm() in there undoes the effect of __mnt_make_longterm()
we'd done back when we set ->mnt_ns non-NULL; it should not be done to
vfsmounts that had never gone through commit_tree() and friends.  Kudos to
lczerner for catching that one...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index edc1c4aef75..b3d8f51c6fa 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1244,8 +1244,9 @@ void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill)
                 list_del_init(&p->mnt_expire);
                 list_del_init(&p->mnt_list);
                 __touch_mnt_namespace(p->mnt_ns);
+                if (p->mnt_ns)
+                        __mnt_make_shortterm(p);
                 p->mnt_ns = NULL;
-                __mnt_make_shortterm(p);
                 list_del_init(&p->mnt_child);
                 if (p->mnt_parent != p) {
                         p->mnt_parent->mnt_ghosts++;