dlm: missing length check in check_config()

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NDavid Teigland <teigland@redhat.com>

fs/dlm/rcom.c

@@ -85,6 +85,7 @@ static void make_config(struct dlm_ls *ls, struct rcom_config *rf)
 static int check_config(struct dlm_ls *ls, struct dlm_rcom *rc, int nodeid)
 {
 	struct rcom_config *rf = (struct rcom_config *) rc->rc_buf;
+	size_t conf_size = sizeof(struct dlm_rcom) + sizeof(struct rcom_config);
 
 	if ((rc->rc_header.h_version & 0xFFFF0000) != DLM_HEADER_MAJOR) {
 		log_error(ls, "version mismatch: %x nodeid %d: %x",
@@ -93,6 +94,12 @@ static int check_config(struct dlm_ls *ls, struct dlm_rcom *rc, int nodeid)
 		return -EPROTO;
 	}
 
+	if (rc->rc_header.h_length < conf_size) {
+		log_error(ls, "config too short: %d nodeid %d",
+			  rc->rc_header.h_length, nodeid);
+		return -EPROTO;
+	}
+
 	if (le32_to_cpu(rf->rf_lvblen) != ls->ls_lvblen ||
 	    le32_to_cpu(rf->rf_lsflags) != ls->ls_exflags) {
 		log_error(ls, "config mismatch: %d,%x nodeid %d: %d,%x",