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  1. MariaDB Server
  2. MDEV-7475

Wrong implementation of checking PLUGIN_VAR_SET condition

    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 5.5.41, 10.0.15
    • Fix Version/s: 5.5.42, 10.0.16
    • Component/s: Plugins
    • Labels:
    • Environment:
      I've confirmed in Windows + Visual Studio 2013. But, other platform is affected this issue. e.g. CentOS 6.5.

      Description

      This issue is MariaDB specific. MySQL is not implement this condition checking.

      In sql_plugin.cc, MariaDB implements PLUGIN_VAR_STR check as follows:

         3963        if (mysqld_server_started &&
         3964            ((o->flags & (PLUGIN_VAR_STR | PLUGIN_VAR_NOCMDOPT |
         3965                           PLUGIN_VAR_MEMALLOC)) == PLUGIN_VAR_STR))
         3966        { 
      

      But, this implementation has a critical bug which causes SEGV.

      This SEGV issues causes as follows:

      • Build latest Mroonga
      • Install built Mroonga into MariaDB
      • MySQL client lost connection against mysqld.
      Lost connection log:
      MariaDB [(none)]> INSTALL PLUGIN Mroonga SONAME 'ha_mroonga.dll';
      ERROR 2013 (HY000): Lost connection to MySQL server during query 
      

      Because, these phenomena causes wrong condition about PLUGIN_VAR_STR.

      In include/mysql/plugin.h, a series of PLUGIN_* value defined.
      But, these value has a misleading point.

      Here is the misleading point:
      From PLUGIN_VAR_BOOL to PLUGIN_VAR_DOUBLE are not assumed as a flag. But, defined after PLUGIN_VAR_UNSIGNED macro value are designed as a flag.

      OK, let's apply above description in practice.

      Here is the line which has causes problem:

       (o->flags & (PLUGIN_VAR_STR | PLUGIN_VAR_NOCMDOPT | PLUGIN_VAR_MEMALLOC)) == PLUGIN_VAR_STR
      

      From above description,

      o->flags & (PLUGIN_VAR_NOCMDOPT | PLUGIN_VAR_MEMALLOC) 
      

      is valid, because PLUGIN_VAR_NOCMDOPT and PLUGIN_VAR_MEMALLOC are designed as a flag. It is valid.
      But,

       (o->flags & PLUGIN_VAR_STR) == PLUGIN_VAR_STR
      

      is invalid code. Because,

      (PLUGIN_VAR_SET & PLUGIN_VAR_STR) == PLUGIN_VAR_STR 
      

      is true!
      In more detail, PLUGIN_VAR_STR and PLUGIN_VAR_SET are defined as follows in include/mysql/plugin.h:

      #define PLUGIN_VAR_STR          0x0005
      #define PLUGIN_VAR_SET          0x0007
      

      So, PLUGIN_VAR_SET & PLUGIN_VAR_STR ( 0x0007 AND 0x0005) equals PLUGIN_VAR_STR (0x0005).

      This result causes following bug:
      In latest Mroonga, specifies PLUGIN_VAR_SET ( https://github.com/mroonga/mroonga/blob/master/ha_mroonga.cpp#L965 ), not specifies PLUGIN_VAR_STR. But,

       (o->flags & (PLUGIN_VAR_STR | PLUGIN_VAR_NOCMDOPT | PLUGIN_VAR_MEMALLOC)) == PLUGIN_VAR_STR
      

      matches PLUGIN_VAR_STR, in spite of PLUGIN_VAR_STR is not set (NULL).

      As a result, causes SEGV and not to be able to register Mroonga storage engine plugin into MariaDB.

      I've added a fix patch which is written by Kohei Sutou.
      original patch found by (Sorry, this email is in Japanese...) : http://sourceforge.jp/projects/groonga/lists/archive/dev/2015-January/003067.html

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            • Assignee:
              serg Sergei Golubchik
              Reporter:
              cosmo0920 hiroshi HATAKE
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                Updated:
                Resolved:

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