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mariadb/mysql-test/suite/rpl/t/rpl_row_trigger_multi_db.test
Brandon Nesterenko c2d44ecb90 MDEV-29894: Calling a function from a different database in a slave side trigger crashes
When opening and locking tables, if triggers will be invoked in a
separate database, thd->set_db() is invoked, thus freeeing the memory
and headers which thd->db had previously pointed to. In row based
replication, the event execution logic initializes thd->db to point
to the database which the event targets, which is owned by the
corresponding table share (introduced in d9898c9 for MDEV-7409).
The problem then, is that during the table opening and locking
process for a row event, memory which belongs to the table share
would be freed, which is not valid.

This patch replaces the thd->reset_db() calls to thd->set_db(),
which copies-by-value, rather than by reference. Then when the
memory is freed, our copy of memory is freed, rather than memory
which belongs to a table share.

Notes:
  1. The call to change thd->db now happens on a higher-level, in
Rows_log_event::do_apply_event() rather than ::do_exec_row(), in the
call stack. This is because do_exec_row() is called within a loop,
and each invocation would redundantly set and unset the db to the
same value.
  2. thd->set_db() is only used if triggers are to be invoked, as
there is no vulnerability in the non-trigger case, and copying
memory would be an unnecessary inefficiency.

Reviewed By:
============
Andrei Elkin <andrei.elkin@mariadb.com>
2023-06-21 12:51:01 -06:00

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#
# This test ensures that a table share's database name is not freed when
# using row based replication with triggers that open different databases
#
#
# References:
# MDEV-29894: Calling a function from a different database in a slave side
# trigger crashes
#
--source include/master-slave.inc
--source include/have_binlog_format_row.inc
--connection slave
--let $old_slave_run_triggers= `SELECT @@global.slave_run_triggers_for_rbr`
set global slave_run_triggers_for_rbr=1;
--connection master
CREATE TABLE t1 (a int);
--sync_slave_with_master
--connection slave
CREATE DATABASE db2;
CREATE FUNCTION db2.get_value(a INT) RETURNS int(2) RETURN 0;
--echo #
--echo # Test Insert_rows_log_event
--connection slave
DELIMITER //;
CREATE TRIGGER tr_ins BEFORE INSERT ON t1 FOR EACH ROW BEGIN
DECLARE a INT;
SET a = db2.get_value(1);
END//
DELIMITER ;//
--connection master
INSERT INTO t1 VALUES (1);
--sync_slave_with_master
--connection slave
DROP TRIGGER tr_ins;
--echo #
--echo # Test Update_rows_log_event
--connection master
--let $row_val=5
--eval INSERT INTO t1 VALUES ($row_val)
--sync_slave_with_master
--connection slave
DELIMITER //;
CREATE TRIGGER tr_upd BEFORE UPDATE ON t1 FOR EACH ROW BEGIN
DECLARE a INT;
SET a = db2.get_value(1);
END//
DELIMITER ;//
--connection master
--eval UPDATE t1 SET a=a+1 WHERE a=$row_val
--sync_slave_with_master
--connection slave
DROP TRIGGER tr_upd;
--echo #
--echo # Test Delete_rows_log_event
--connection master
--let $row_val=7
--eval INSERT INTO t1 VALUES ($row_val)
--sync_slave_with_master
--connection slave
DELIMITER //;
CREATE TRIGGER tr_del BEFORE DELETE ON t1 FOR EACH ROW BEGIN
DECLARE a INT;
SET a = db2.get_value(1);
END//
DELIMITER ;//
--connection master
--eval DELETE FROM t1 WHERE a=$row_val
--sync_slave_with_master
--connection slave
DROP TRIGGER tr_del;
--echo #
--echo # Cleanup
--connection slave
--eval SET GLOBAL slave_run_triggers_for_rbr=$old_slave_run_triggers
DROP DATABASE db2;
--connection master
DROP TABLE t1;
--source include/rpl_end.inc