[PATCH 4.9 088/141] gfs2_meta: ->mount() can get NULL dev_name

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>

commit 3df629d873f8683af6f0d34dfc743f637966d483 upstream.

get in sync with mount_bdev() handling of the same

Reported-by: syzbot+c54f8e94e6bba03b04e9@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/gfs2/ops_fstype.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -1355,6 +1355,9 @@ static struct dentry *gfs2_mount_meta(st
 	struct path path;
 	int error;
 
+	if (!dev_name || !*dev_name)
+		return ERR_PTR(-EINVAL);
+
 	error = kern_path(dev_name, LOOKUP_FOLLOW, &path);
 	if (error) {
 		pr_warn("path_lookup on %s returned error %d\n",