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MDEV-24929 Server crash in thr_multi_unlock or in get_schema_tables_result

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This was caused by two different bugs:
1) Information_schema tables where not locked by lock_tables, but
   get_lock_data() was not filtering these out. This caused a crash when
   mysql_unlock_some_tables() tried to unlock tables early, including
   not locked information schema tables.

Fixed by not locking SYSTEM_TMP_TABLES

2) In some cases the optimizer will notice that we do not need to read
   the information_schema tables at all. In this case
   join_tab->read_record is not set, which caused a crash in
   get_schema_tables_result()

Fixed by ignoring const tables in get_schema_tables_result()
This commit is contained in:
Monty 2021-02-20 14:46:19 +02:00 committed by Sergei Golubchik
parent 0ab1e3914c
commit 640f42311a
4 changed files with 43 additions and 7 deletions
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13
mysql-test/main/information_schema.result
View file

@ -2303,5 +2303,18 @@ group by f;
f
drop table t1;
#
# MDEV-24929 Server crash in thr_multi_unlock or in
# get_schema_tables_result upon select from I_S with joins
#
CREATE TABLE t1 (a TIMESTAMP, KEY (a));
INSERT INTO t1 VALUES ('2012-12-12'),('2021-11-11');
SELECT count(*) FROM t1 AS t1a LEFT JOIN (t1 AS t1b JOIN INFORMATION_SCHEMA.ROUTINES) ON (t1b.a IS NULL);
count(*)
2
SELECT count(*) FROM t1 AS t1a LEFT JOIN (t1 AS t1b JOIN INFORMATION_SCHEMA.PROFILING) ON (t1b.a IS NULL);
count(*)
2
DROP TABLE t1;
#
# End of 10.3 tests
#

10
mysql-test/main/information_schema.test
View file

@ -2034,6 +2034,16 @@ inner join t1 on f=i.column_name
group by f;
drop table t1;
--echo #
--echo # MDEV-24929 Server crash in thr_multi_unlock or in
--echo # get_schema_tables_result upon select from I_S with joins
--echo #
CREATE TABLE t1 (a TIMESTAMP, KEY (a));
INSERT INTO t1 VALUES ('2012-12-12'),('2021-11-11');
SELECT count(*) FROM t1 AS t1a LEFT JOIN (t1 AS t1b JOIN INFORMATION_SCHEMA.ROUTINES) ON (t1b.a IS NULL);
SELECT count(*) FROM t1 AS t1a LEFT JOIN (t1 AS t1b JOIN INFORMATION_SCHEMA.PROFILING) ON (t1b.a IS NULL);
DROP TABLE t1;
--echo #
--echo # End of 10.3 tests
--echo #

17
sql/lock.cc
View file

@ -727,6 +727,9 @@ static int unlock_external(THD *thd, TABLE **table,uint count)
- GET_LOCK_STORE_LOCKS : Store lock info in TABLE
- GET_LOCK_SKIP_SEQUENCES : Ignore sequences (for temporary unlock)
- GET_LOCK_ON_THD : Store lock in thd->mem_root
Temporary tables are not locked (as these are single user), except for
TRANSACTIONAL_TMP_TABLES as locking is needed to handle transactions.
*/
MYSQL_LOCK *get_lock_data(THD *thd, TABLE **table_ptr, uint count, uint flags)
@ -743,8 +746,8 @@ MYSQL_LOCK *get_lock_data(THD *thd, TABLE **table_ptr, uint count, uint flags)
{
TABLE *t= table_ptr[i];
if (t->s->tmp_table != NON_TRANSACTIONAL_TMP_TABLE &&
t->s->tmp_table != INTERNAL_TMP_TABLE &&
if ((likely(!t->s->tmp_table) ||
(t->s->tmp_table == TRANSACTIONAL_TMP_TABLE)) &&
(!(flags & GET_LOCK_SKIP_SEQUENCES) || t->s->sequence == 0))
{
lock_count+= t->file->lock_count();
@ -772,13 +775,13 @@ MYSQL_LOCK *get_lock_data(THD *thd, TABLE **table_ptr, uint count, uint flags)
for (i=0 ; i < count ; i++)
{
TABLE *table;
TABLE *table= table_ptr[i];
enum thr_lock_type lock_type;
THR_LOCK_DATA **locks_start;
table= table_ptr[i];
if (table->s->tmp_table == NON_TRANSACTIONAL_TMP_TABLE ||
table->s->tmp_table == INTERNAL_TMP_TABLE ||
((flags & GET_LOCK_SKIP_SEQUENCES) && table->s->sequence))
if (!((likely(!table->s->tmp_table) ||
(table->s->tmp_table == TRANSACTIONAL_TMP_TABLE)) &&
(!(flags & GET_LOCK_SKIP_SEQUENCES) || table->s->sequence == 0)))
continue;
lock_type= table->reginfo.lock_type;
DBUG_ASSERT(lock_type != TL_WRITE_DEFAULT && lock_type != TL_READ_DEFAULT);

10
sql/sql_show.cc
View file

@ -8837,6 +8837,16 @@ bool get_schema_tables_result(JOIN *join,
if (table_list->schema_table->fill_table == 0)
continue;
/*
Do not fill in tables thare are marked as JT_CONST as these will never
be read and they also don't have a tab->read_record.table set!
This can happen with queries like
SELECT * FROM t1 LEFT JOIN (t1 AS t1b JOIN INFORMATION_SCHEMA.ROUTINES)
ON (t1b.a IS NULL);
*/
if (tab->type == JT_CONST)
continue;
/* skip I_S optimizations specific to get_all_tables */
if (lex->describe &&
(table_list->schema_table->fill_table != get_all_tables))