mount: handle NULL values in mnt_ns_release()

commit 6c7ca6a02f8f9549a438a08a23c6327580ecf3d6 upstream.

When calling in listmount() mnt_ns_release() may be passed a NULL
pointer. Handle that case gracefully.

Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/namespace.c b/fs/namespace.c
index f5e46c2595b114ef66f18a2caa109f03beb7e56e..cc4926d53e7deac6d02ffb29768480eb2f5e2e1e 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -153,7 +153,7 @@ static void mnt_ns_release(struct mnt_namespace *ns)
        lockdep_assert_not_held(&mnt_ns_tree_lock);
 
        /* keep alive for {list,stat}mount() */
-       if (refcount_dec_and_test(&ns->passive)) {
+       if (ns && refcount_dec_and_test(&ns->passive)) {
                put_user_ns(ns->user_ns);
                kfree(ns);
        }