Fixes to Coverity tasks : 73267, 72686, 72672

Cleaned up warnings, and added checks to malloc return values and error log writes in case of failures.

server/modules/protocol/mysql_backend.c

@@ -1300,14 +1300,33 @@ static int gw_change_user(
 						backend->session->client->remote,
 						password_set,
 						"");
+		if (message == NULL)
+		{
+			LOGIF(LE, (skygw_log_write_flush(
+				LOGFILE_ERROR,
+				"Error : Creating error message failed."))); 
+			rv = 0;
+			goto retblock;
+		}
 		/** TODO: Add custom message indicating that retry would probably help */
 		buf = modutil_create_mysql_err_msg(1, 0, 1045, "28000", message);
+		free(message);
+		
+		if (buf == NULL)
+		{
+			LOGIF(LE, (skygw_log_write_flush(
+				LOGFILE_ERROR,
+				"Error : Creating buffer for error message failed."))); 
+			rv = 0;
+			goto retblock;			
+		}
 		/** Set flags that help router to identify session commans reply */
 		gwbuf_set_type(buf, GWBUF_TYPE_MYSQL);
 		gwbuf_set_type(buf, GWBUF_TYPE_SESCMD_RESPONSE);
 		gwbuf_set_type(buf, GWBUF_TYPE_RESPONSE_END);
 		/** Create an incoming event for backend DCB */
-		poll_add_epollin_event_to_dcb(backend, buf);
+		poll_add_epollin_event_to_dcb(backend, gwbuf_clone(buf));
+		gwbuf_free(buf);
 		rv = 0;
         } else {
 		rv = gw_send_change_user_to_backend(database, username, client_sha1, backend_protocol);
@@ -1318,6 +1337,8 @@ static int gw_change_user(
 		strcpy(current_session->db, database);
 		memcpy(current_session->client_sha1, client_sha1, sizeof(current_session->client_sha1));
         }
+        
+retblock:
         gwbuf_free(queue);
 
 	return rv;

server/modules/protocol/mysql_common.c

@@ -2106,19 +2106,34 @@ char *create_auth_fail_str(
 	else
 		db_len = 0;
 
-	if (db_len>0)
+	if (db_len > 0)
+	{
 		ferrstr = "Access denied for user '%s'@'%s' (using password: %s) to database '%s'";
+	}
 	else
+	{
 		ferrstr = "Access denied for user '%s'@'%s' (using password: %s)";
-		
+	}	
 	errstr = (char *)malloc(strlen(username)+strlen(ferrstr)+strlen(hostaddr)+strlen("YES")-6 + db_len + ((db_len > 0) ? (strlen(" to database ") +2) : 0) + 1);
 	
-	if (errstr != NULL) {
-		if (db_len>0)
-			sprintf(errstr, ferrstr, username, hostaddr, (*sha1 == '\0' ? "NO" : "YES"), db); 
-		else
-			sprintf(errstr, ferrstr, username, hostaddr, (*sha1 == '\0' ? "NO" : "YES")); 
+	if (errstr == NULL)
+	{
+		LOGIF(LE, (skygw_log_write_flush(
+			LOGFILE_ERROR,
+			"Error : Memory allocation failed due to %s.", 
+			strerror(errno)))); 
+		goto retblock;
 	}
 
+	if (db_len > 0)
+	{
+		sprintf(errstr, ferrstr, username, hostaddr, (*sha1 == '\0' ? "NO" : "YES"), db); 
+	}
+	else
+	{
+		sprintf(errstr, ferrstr, username, hostaddr, (*sha1 == '\0' ? "NO" : "YES")); 
+	}
+	
+retblock:
 	return errstr;
 }

server/modules/routing/readconnroute.c

@@ -654,7 +654,7 @@ DCB*              backend_dcb;
  * @param instance		The router instance
  * @param router_session	The router session returned from the newSession call
  * @param queue			The queue of data buffers to route
- * @return The number of bytes sent
+ * @return if succeed 1, otherwise 0
  */
 static	int	
 routeQuery(ROUTER *instance, void *router_session, GWBUF *queue)
@@ -697,20 +697,22 @@ routeQuery(ROUTER *instance, void *router_session, GWBUF *queue)
                         "Error : Failed to route MySQL command %d to backend "
                         "server.",
                         mysql_command)));
+		rc = 0;
                 goto return_rc;
         }
         
 	switch(mysql_command) {
-        case MYSQL_COM_CHANGE_USER:
-                rc = backend_dcb->func.auth(
-                        backend_dcb,
-                        NULL,
-                        backend_dcb->session,
-                        queue);
-		break;
-        default:
-                rc = backend_dcb->func.write(backend_dcb, queue);
-                break;
+		case MYSQL_COM_CHANGE_USER:
+			rc = backend_dcb->func.auth(
+				backend_dcb,
+				NULL,
+				backend_dcb->session,
+				queue);
+			break;
+		
+		default:
+			rc = backend_dcb->func.write(backend_dcb, queue);
+			break;
         }
         
         CHK_PROTOCOL(((MySQLProtocol*)backend_dcb->protocol));

server/modules/routing/readwritesplit/readwritesplit.c

@@ -3829,7 +3829,6 @@ static bool route_session_write(
                                 {
                                         succp = false;
                                 }
-
                         }
                 }
                 rses_end_locked_router_action(router_cli_ses);
@@ -3842,6 +3841,12 @@ static bool route_session_write(
                 succp = false;
                 goto return_succp;
         }
+        
+        if (router_cli_ses->rses_nbackends <= 0)
+	{
+		succp = false;
+		goto return_succp;
+	}
         /** 
          * Additional reference is created to querybuf to 
          * prevent it from being released before properties
@@ -3909,6 +3914,10 @@ static bool route_session_write(
                                 }
                         }
                 }
+                else
+		{
+			succp = false;
+		}
         }
         /** Unlock router session */
         rses_end_locked_router_action(router_cli_ses);