ovl: fix getcwd() failure after unsuccessful rmdir

From: Rui Wang <[email protected]>
Date: Fri, 8 Jan 2016 23:09:59 +0800

commit ce9113bbcbf45a57c082d6603b9a9f342be3ef74 upstream.

ovl_remove_upper() should do d_drop() only after it successfully removes the dir, otherwise a subsequent getcwd() system call will fail, breaking userspace programs.

This is to fix: https://bugzilla.kernel.org/show_bug.cgi?id=110491

---
 fs/overlayfs/dir.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

@@ -618,7 +618,8 @@ static int ovl_remove_upper(struct dentr
 	 * sole user of this dentry.  Too tricky...  Just unhash for
 	 * now.
 	 */
-	d_drop(dentry);
+	if (!err)
+		d_drop(dentry);
 	mutex_unlock(&dir->i_mutex);
 
 	return err;