Fix defects identified by Coverity.

src/bridge.c

@@ -80,13 +80,14 @@ int mqtt3_bridge_new(struct mosquitto_db *db, struct _mqtt3_bridge *bridge)
 	HASH_FIND(hh_id, db->contexts_by_id, local_id, strlen(local_id), new_context);
 	if(new_context){
 		/* (possible from persistent db) */
+		_mosquitto_free(local_id);
 	}else{
 		/* id wasn't found, so generate a new context */
 		new_context = mqtt3_context_init(db, -1);
 		if(!new_context){
 			return MOSQ_ERR_NOMEM;
 		}
-		new_context->id = _mosquitto_strdup(local_id);
+		new_context->id = local_id;
 		HASH_ADD_KEYPTR(hh_id, db->contexts_by_id, new_context->id, strlen(new_context->id), new_context);
 	}
 	new_context->bridge = bridge;

src/read_handle_server.c

@@ -468,6 +468,7 @@ int mqtt3_handle_connect(struct mosquitto_db *db, struct mosquitto *context)
 			ws_ctxt_user_head = (struct libws_mqtt_hack *)libwebsocket_context_user(found_context->ws_context);
 			ws_ctxt_user = _mosquitto_calloc(1, sizeof(struct libws_mqtt_hack));
 			if(!ws_ctxt_user){
+				rc = MOSQ_ERR_NOMEM;
 				goto handle_connect_error;
 			}
 			ws_ctxt_user->old_mosq = found_context;
@@ -492,20 +493,16 @@ int mqtt3_handle_connect(struct mosquitto_db *db, struct mosquitto *context)
 			ws_ctxt_user_head = (struct libws_mqtt_hack *)libwebsocket_context_user(found_context->ws_context);
 			ws_ctxt_user = _mosquitto_calloc(1, sizeof(struct libws_mqtt_hack));
 			if(!ws_ctxt_user){
+				rc = MOSQ_ERR_NOMEM;
 				goto handle_connect_error;
 			}
 			ws_ctxt_user->old_mosq = context;
 			ws_ctxt_user->new_mosq = found_context;
 
-			if(ws_ctxt_user_head){
 			while(ws_ctxt_user_head->next){
 				ws_ctxt_user_head = ws_ctxt_user_head->next;
 			}
 			ws_ctxt_user_head->next = ws_ctxt_user;
-			}else{
-				ws_ctxt_user->next = ws_ctxt_user_head->next;
-				ws_ctxt_user_head->next = ws_ctxt_user;
-			}
 			HASH_ADD_KEYPTR(hh_for_free, db->contexts_for_free, context, sizeof(void *), context);
 		}else{
 			HASH_ADD_KEYPTR(hh_for_free, db->contexts_for_free, context, sizeof(void *), context);

src/websockets.c

@@ -141,10 +141,15 @@ static int callback_mqtt(struct libwebsocket_context *context,
 				mosq->ws_context = context;
 				mosq->wsi = wsi;
 				u->mosq = mosq;
+			}else{
+				return -1;
 			}
 			break;
 
 		case LWS_CALLBACK_CLOSED:
+			if(!u){
+				return -1;
+			}
 			mosq = u->mosq;
 			if(mosq){
 				mosq->wsi = NULL;
@@ -153,6 +158,9 @@ static int callback_mqtt(struct libwebsocket_context *context,
 			break;
 
 		case LWS_CALLBACK_SERVER_WRITEABLE:
+			if(!u){
+				return -1;
+			}
 			mosq = u->mosq;
 			if(!mosq || mosq->state == mosq_cs_disconnect_ws || mosq->state == mosq_cs_disconnecting){
 				return -1;
@@ -209,6 +217,9 @@ static int callback_mqtt(struct libwebsocket_context *context,
 			break;
 
 		case LWS_CALLBACK_RECEIVE:
+			if(!u){
+				return -1;
+			}
 			mosq = u->mosq;
 			pos = 0;
 			buf = (uint8_t *)in;