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MDEV-30902 Server crash in LEX::first_lists_tables_same

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ONLINE ALTER TABLE uses binlog events like the replication does.

Before it was never used outside of replication, so significant
change was required. For example, a single event had a statement-like
befavior: it locked the tables, opened it, and closed them in the end. But
for ONLINE ALTER we use preopened table.

A crash scenario is following: lex->query_tables was set to NULL in
restore_empty_query_table_list when alter event is applied.
Then lex->query_tables->prev_global was write-accessed in
LEX::first_lists_tables_same, leading to a segfault.

In replication restore_empty_query_table_list would mean resetting lex
before next query or event.

In ONLINE ALTER TABLE we reuse a locked table between the events, so
we should avoid it. Here the need to reset lex state (or close the tables)
can be determined by nonzero rgi->tables_to_lock_count.
If no table is locked, then event doesn't own the tables.

The same was already done before for rgi->slave_close_thread_tables call.
This commit is contained in:
Nikita Malyavin
2023-03-22 23:31:15 +03:00
committed by Sergei Golubchik
parent b08b78c5b9
commit 6f78efc01c
3 changed files with 53 additions and 3 deletions
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18
mysql-test/main/alter_table_online_debug.result
View File

@ -976,6 +976,8 @@ insert into t values (3);
set debug_sync= 'now signal goforit';
xa end 'xid';
xa commit 'xid' one phase;
connection con1;
connection default;
drop table t;
set debug_sync= reset;
#
@ -1158,5 +1160,21 @@ set debug_sync= reset;
set debug_dbug= @old_debug;
connection default;
#
# MDEV-30902 Server crash in LEX::first_lists_tables_same
#
create table t1 engine=myisam select 1 as x ;
create procedure p() alter table t1 engine=heap;
set debug_sync= 'alter_table_copy_end signal ended wait_for end';
call p;
connection con1;
set debug_sync= 'now wait_for ended';
insert into t1 values (2);
set debug_sync= 'now signal end';
connection default;
call p;
drop table t1;
drop procedure p;
set debug_sync=reset;
#
# End of 11.2 tests
#

25
mysql-test/main/alter_table_online_debug.test
View File

@ -1149,6 +1149,9 @@ xa end 'xid';
xa commit 'xid' one phase;
# Cleanup
--connection con1
--reap
--connection default
drop table t;
set debug_sync= reset;
@ -1326,6 +1329,28 @@ set debug_sync= reset;
set debug_dbug= @old_debug;
--connection default
--echo #
--echo # MDEV-30902 Server crash in LEX::first_lists_tables_same
--echo #
create table t1 engine=myisam select 1 as x ;
create procedure p() alter table t1 engine=heap;
set debug_sync= 'alter_table_copy_end signal ended wait_for end';
send call p;
--connection con1
set debug_sync= 'now wait_for ended';
insert into t1 values (2);
set debug_sync= 'now signal end';
--connection default
--reap
call p;
drop table t1;
drop procedure p;
set debug_sync=reset;
--echo #
--echo # End of 11.2 tests
--echo #

11
sql/log_event_server.cc
View File

@ -5238,7 +5238,12 @@ int Rows_log_event::do_apply_event(rpl_group_info *rgi)
goto err;
}
/* remove trigger's tables */
/*
Remove trigger's tables. In case of ONLINE ALTER TABLE, event doesn't own
the table (hence, no tables are locked), and therefore no cleanup should be
done after each event.
*/
if (rgi->tables_to_lock_count)
restore_empty_query_table_list(thd->lex);
if (WSREP(thd) && wsrep_thd_is_applying(thd))
@ -5258,9 +5263,11 @@ int Rows_log_event::do_apply_event(rpl_group_info *rgi)
DBUG_RETURN(error);
err:
restore_empty_query_table_list(thd->lex);
if (rgi->tables_to_lock_count)
{
restore_empty_query_table_list(thd->lex);
rgi->slave_close_thread_tables(thd);
}
thd->reset_query_timer();
DBUG_RETURN(error);
}