dlm: Fix kernel memory disclosure

Clear the 'unused' field and the uninitialized padding in 'lksb' to
avoid leaking memory to userland in copy_result_to_user().
Signed-off-by: Vlad Tsyrklevich <vlad@tsyrklevich.net>
Signed-off-by: David Teigland <teigland@redhat.com>

fs/dlm/user.c

@@ -123,6 +123,8 @@ static void compat_input(struct dlm_write_request *kb,
 static void compat_output(struct dlm_lock_result *res,
 			  struct dlm_lock_result32 *res32)
 {
+	memset(res32, 0, sizeof(*res32));
+
 	res32->version[0] = res->version[0];
 	res32->version[1] = res->version[1];
 	res32->version[2] = res->version[2];