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  1. MariaDB Server
  2. MDEV-31636

Memory leak in Sys_var_gtid_binlog_state::do_check()

Details

    Description

      --source include/have_log_bin.inc
      		 
      RESET MASTER;
      		 
      --error ER_WRONG_VALUE_FOR_VAR
      		 
      SET
      		 
        @@global.gtid_binlog_state='1-1-101,2-1-2002',
      		 
        @@global.slave_parallel_mode=x;
      		 
      SELECT @@global.gtid_binlog_state;


      ***Warnings generated in error logs during shutdown after running tests: main.AAA
      		 
       
      		 
      Warning: Memory not freed: 224
      		 
      Warning:   40 bytes lost at 0x45fa260, allocated by T@0 at sql/sys_vars.cc:2120, sql/set_var.cc:246, sql/set_var.cc:810, sql/set_var.cc:738, sql/sql_parse.cc:5040, sql/sql_parse.cc:8023, sql/sql_parse.cc:1896, sql/sql_parse.cc:1407
      		 
      Warning:  184 bytes lost at 0x7f71481b7790, allocated by T@0 at mysys/my_malloc.c:143, sql/rpl_gtid.cc:1359, sql/sys_vars.cc:2114, sql/set_var.cc:246, sql/set_var.cc:810, sql/set_var.cc:738, sql/sql_parse.cc:5040, sql/sql_parse.cc:8023
      		 
      Warning:  152 bytes lost at 0x409c760, allocated by T@0 at mysys/array.c:73, mysys/hash.c:99, sql/sql_hset.h:37, sql/debug_sync.cc:90, sql/debug_sync.cc:166, sql/debug_sync.cc:1808, ??:0, csu/libc-start.c:268
      		 
      Warning:   40 bytes lost at 0x45fa260, allocated by T@0 at sql/sys_vars.cc:2120, sql/set_var.cc:246, sql/set_var.cc:810, sql/set_var.cc:738, sql/sql_parse.cc:5040, sql/sql_parse.cc:8023, sql/sql_parse.cc:1896, sql/sql_parse.cc:1407
      		 
      Warning:  184 bytes lost at 0x7f71481b7790, allocated by T@0 at mysys/my_malloc.c:143, sql/rpl_gtid.cc:1359, sql/sys_vars.cc:2114, sql/set_var.cc:246, sql/set_var.cc:810, sql/set_var.cc:738, sql/sql_parse.cc:5040, sql/sql_parse.cc:8023

      The leaked memory is allocated in Sys_var_gtid_binlog_state::do_check() in this code:

        if (!(data= (gtid_binlog_state_data *)my_malloc(PSI_INSTRUMENT_ME,
      		 
                                                        sizeof(*data), MYF(0))))
      		 
        {

      The problem happens because:

      • The @@global.gtid_binlog_state='1-1-101,2-1-2002' part of the statement allocated memory and assigns it to var->save_result.ptr
      • The @@global.slave_parallel_mode=x part fails on an error (wrong value)
      • The entire statement fails
      • The allocated value in var->save_result.ptr is never freed during the statement cleanup

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          bar Alexander Barkov added a comment - - edited

          For the new system variable @@character_set_collations we'll need to allocate a temporary value to pass it between do_check() and session_update()/global_update(), similar to how it is done in @@gtid_binlog_state. So @@gtid_binlog_state should be fixed first.

          bar Alexander Barkov added a comment - - edited For the new system variable @@character_set_collations we'll need to allocate a temporary value to pass it between do_check() and session_update() / global_update() , similar to how it is done in @@gtid_binlog_state . So @@gtid_binlog_state should be fixed first.
          bar Alexander Barkov added a comment -

          A possible solution would be to allocate the structure on THD::mem_root instead of using my_malloc.

          bar Alexander Barkov added a comment - A possible solution would be to allocate the structure on THD::mem_root instead of using my_malloc.
          Elkin Andrei Elkin added a comment -

          A note on github is made to resolve.

          Elkin Andrei Elkin added a comment - A note on github is made to resolve.

          People

            Elkin Andrei Elkin
            bar Alexander Barkov
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            Dates

              Created:
              Updated:
              Resolved:

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