MDEV-24317 Data race in LOGGER::init_error_log at sql/log.cc:1443 and in LOGGER::error_log_print at sql/log.cc:1181

don't initialize error_log_handler_list in set_handlers()
* error_log_handler_list is initialized to LOG_FILE early, in init_base()
* set_handlers always reinitializes it to LOG_FILE, so it's pointless
* after init_base() concurrent threads start using sql_log_warning,
  so following set_handlers() shouldn't modify error_log_handler_list
  without some protection

Author: vuvova

extra/mariabackup/xtrabackup.cc

@@ -6576,7 +6576,7 @@ int main(int argc, char **argv)
 	key_map_full.set_all();
 
 	logger.init_base();
-	logger.set_handlers(LOG_FILE, LOG_NONE, LOG_NONE);
+	logger.set_handlers(LOG_NONE, LOG_NONE);
 	mysql_mutex_init(key_LOCK_error_log, &LOCK_error_log,
 			 MY_MUTEX_INIT_FAST);
 

sql/log.cc

@@ -1561,13 +1561,9 @@ bool Log_to_csv_event_handler::init()
   return 0;
 }
 
-int LOGGER::set_handlers(ulonglong error_log_printer,
-                         ulonglong slow_log_printer,
+int LOGGER::set_handlers(ulonglong slow_log_printer,
                          ulonglong general_log_printer)
 {
-  /* error log table is not supported yet */
-  DBUG_ASSERT(error_log_printer < LOG_TABLE);
-
   lock_exclusive();
 
   if ((slow_log_printer & LOG_TABLE || general_log_printer & LOG_TABLE) &&
@@ -1580,7 +1576,6 @@ int LOGGER::set_handlers(ulonglong error_log_printer,
                     "Falling back to the old-fashioned logs");
   }
 
-  init_error_log(error_log_printer);
   init_slow_log(slow_log_printer);
   init_general_log(general_log_printer);
 

sql/log.h

@@ -1103,8 +1103,7 @@ class LOGGER
                          const char *query, size_t query_length);
 
   /* we use this function to setup all enabled log event handlers */
-  int set_handlers(ulonglong error_log_printer,
-                   ulonglong slow_log_printer,
+  int set_handlers(ulonglong slow_log_printer,
                    ulonglong general_log_printer);
   void init_error_log(ulonglong error_log_printer);
   void init_slow_log(ulonglong slow_log_printer);

sql/mysqld.cc

@@ -3607,7 +3607,7 @@ pthread_handler_t signal_hand(void *arg __attribute__((unused)))
       sql_print_information("Got signal %d to shutdown mysqld",sig);
 #endif
       /* switch to the old log message processing */
-      logger.set_handlers(LOG_FILE, global_system_variables.sql_log_slow ? LOG_FILE:LOG_NONE,
+      logger.set_handlers(global_system_variables.sql_log_slow ? LOG_FILE:LOG_NONE,
                           opt_log ? LOG_FILE:LOG_NONE);
       DBUG_PRINT("info",("Got signal: %d  abort_loop: %d",sig,abort_loop));
       if (!abort_loop)
@@ -3642,15 +3642,13 @@ pthread_handler_t signal_hand(void *arg __attribute__((unused)))
       /* reenable logs after the options were reloaded */
       if (log_output_options & LOG_NONE)
       {
-        logger.set_handlers(LOG_FILE,
-                            global_system_variables.sql_log_slow ?
+        logger.set_handlers(global_system_variables.sql_log_slow ?
                             LOG_TABLE : LOG_NONE,
                             opt_log ? LOG_TABLE : LOG_NONE);
       }
       else
       {
-        logger.set_handlers(LOG_FILE,
-                            global_system_variables.sql_log_slow ?
+        logger.set_handlers(global_system_variables.sql_log_slow ?
                             log_output_options : LOG_NONE,
                             opt_log ? log_output_options : LOG_NONE);
       }
@@ -5571,7 +5569,7 @@ static int init_server_components()
       sql_print_warning("There were other values specified to "
                         "log-output besides NONE. Disabling slow "
                         "and general logs anyway.");
-    logger.set_handlers(LOG_FILE, LOG_NONE, LOG_NONE);
+    logger.set_handlers(LOG_NONE, LOG_NONE);
   }
   else
   {
@@ -5587,8 +5585,7 @@ static int init_server_components()
       /* purecov: end */
     }
 
-    logger.set_handlers(LOG_FILE,
-                        global_system_variables.sql_log_slow ?
+    logger.set_handlers(global_system_variables.sql_log_slow ?
                         log_output_options:LOG_NONE,
                         opt_log ? log_output_options:LOG_NONE);
   }