jbd2: fix use after free in jbd2_journal_start_reserved()

commit 92e3b405 upstream.

If start_this_handle() fails then it leads to a use after free of
"handle".
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

fs/jbd2/transaction.c

@@ -514,11 +514,13 @@ int jbd2_journal_start_reserved(handle_t *handle, unsigned int type,
 	 * similarly constrained call sites
 	 */
 	ret = start_this_handle(journal, handle, GFP_NOFS);
-	if (ret < 0)
+	if (ret < 0) {
 		jbd2_journal_free_reserved(handle);
+		return ret;
+	}
 	handle->h_type = type;
 	handle->h_line_no = line_no;
-	return ret;
+	return 0;
 }
 EXPORT_SYMBOL(jbd2_journal_start_reserved);