Another potential DoS CVE for Oracle MySQL of July 2012

Another potential DoS CVE for Oracle MySQL CPU of July 2012

    ------------------------------------------------------------
    revno: 3097.126.64
    committer: [email protected]
    branch nick: systemtables-5.5
    timestamp: Wed 2012-04-11 15:53:17 +0530
    message:
      Bug#11815557 60269: MYSQL SHOULD REJECT ATTEMPTS TO CREATE SYSTEM
                          TABLES IN INCORRECT ENGINE

      PROBLEM:
        CREATE/ALTER TABLE currently can move system tables like
      mysql.db, user, host etc, to engines other than MyISAM. This is not
      completely supported as of now, by mysqld. When some of system tables
      like plugin, servers, event, func, *_priv, time_zone* are moved
      to innodb, mysqld restart crashes. Currently system tables
      can be moved to BLACKHOLE also!!!.

      ANALYSIS:
        The problem is that there is no check before creating or moving
      a system table to some particular engine.

        System tables are suppose to be residing in MyISAM. We can think
      of restricting system tables to exist only in MyISAM. But, there could
      be future needs of these system tables to be part of other engines
      by design. For eg, NDB cluster expects some tables to be on innodb
      or ndb engine. This calls for a solution, by which system
      tables can be supported by any desired engine, with minimal effort.

      FIX:
        The solution provides a handlerton interface using which,
      mysqld server can query particular storage engine handlerton for
      system tables that it supports. This way each storage engine
      layer can define their own system database and system tables.

        The check_engine() function uses the new handlerton function
      ha_check_if_supported_system_table() to check if db.tablename
      provided in the DDL is supported by the SE.

      Note: This fix has modified a test in help.test, which was moving
      mysql.help_* to innodb. The primary intention of the test was not
      to move them between engines.