bgpd: Fix core during received-routes brief json cmd

When a route-map causes a prefix to be denied (with soft-reconfig
enabled), executing show bgp nbr xyz received-routes brief json results
in invoking peer_adj_routes_brief() where prefix_path_count can be 0 and a
premature free of json happens.

This free of json was originally intended for a no-op condition i.e.
to free up the json objects which are originally allocated and not used.

Fixing this.

Ticket :#4081784

Signed-off-by: Rajasekar Raja <[email protected]>

bgpd/bgp_route.c

@@ -14527,6 +14527,7 @@ static int peer_adj_routes_brief(struct vty *vty, struct peer *peer, afi_t afi,
 		struct bgp_adj_in *ain = NULL;
 		struct bgp_adj_out *adj = NULL;
 		struct peer_af *paf = NULL;
+		bool json_pfx_populated = false;
 
 		if (type == bgp_show_adj_route_received) {
 			for (ain = dest->adj_in; ain; ain = ain->next) {
@@ -14545,6 +14546,7 @@ static int peer_adj_routes_brief(struct vty *vty, struct peer *peer, afi_t afi,
 				bgp_prefix_json_info_add(vty, json_flags, json_info,
 							 prefix_path_count, multi_path_count);
 				json_object_object_addf(json_prefix, json_info, "%pFX", rn_p);
+				json_pfx_populated = true;
 			}
 			ain = NULL;
 		} else if (type == bgp_show_adj_route_advertised) {
@@ -14569,12 +14571,14 @@ static int peer_adj_routes_brief(struct vty *vty, struct peer *peer, afi_t afi,
 								 multi_path_count);
 					json_object_object_addf(json_prefix, json_info, "%pFX",
 								rn_p);
+					json_pfx_populated = true;
 				}
 			}
 			adj = NULL;
 		}
 
-		if (prefix_path_count == 0) {
+		/* Free up the below only if json_pfx is not populated */
+		if (prefix_path_count == 0 && !json_pfx_populated) {
 			json_object_free(json_info);
 			json_object_free(json_flags);
 		}