Bug#30882 Dropping a temporary table inside a stored function may cause a server crash

If a stored function that contains a drop temporary table statement
is invoked by a create temporary table of the same name may cause
a server crash. The problem is that when dropping a table no check
is done to ensure that table is not being used by some outer query
(or outer statement), potentially leaving the outer query with a
reference to a stale (freed) table.

The solution is when dropping a temporary table, always check if
the table is being used by some outer statement as a temporary
table can be dropped inside stored procedures.

The check is performed by looking at the TABLE::query_id value for
temporary tables. To simplify this check and to solve a bug related
to handling of temporary tables in prelocked mode, this patch changes
the way in which this member is used to track the fact that table is
used/unused. Now we ensure that TABLE::query_id is zero for unused
temporary tables (which means that all temporary tables which were
used by a statement should be marked as free for reuse after it's
execution has been completed).


mysql-test/include/handler.inc:
  Add test case for side effect of Bug#30882
mysql-test/r/handler_innodb.result:
  Add test case result for side effect of Bug#30882
mysql-test/r/handler_myisam.result:
  Add test case result for side effect of Bug#30882
mysql-test/r/sp-error.result:
  Add test case result for Bug#30882
mysql-test/t/sp-error.test:
  Add test case for Bug#30882
sql/event_db_repository.cc:
  Update close_thread_tables call, no more default values.
sql/mysql_priv.h:
  Remove implicit default parameters values of the close_thread_tables
  function as no callers are using it.
sql/slave.cc:
  Update close_thread_tables call, no more default values
sql/sp_head.cc:
  Update close_thread_tables call, no more default values
sql/sql_base.cc:
  Changed the approach to distinguishing currently unused temporary tables.
  Now we ensure that such tables always have TABLE::query_id set to 0 and
  use this fact to perform checks during opening and dropping of temporary
  tables. This means that we have to call close_thread_tables() even for
  statements which use only temporary tables. To make this call cheaper,
  we re-factored close_thread_tables() to not take LOCK_open unless there
  are open base tables.
sql/sql_handler.cc:
  Properly close temporary tables associated with a handler.
sql/sql_insert.cc:
  close_temporary_table is now merged into drop_temporary_table.
sql/sql_parse.cc:
  Now the condition doesn't cover all cases because close_thread_tables()
  must be called even for statements that use only temporary tables.
sql/sql_table.cc:
  Use drop_temporary_table which perform checks to verify if
  the table is not being used. Error path problem is due to
  a handler tables issue and is going to be addressed in bug
  31397.
sql/table.h:
  Rename previously unused clear_query_id and document the usage of
  query_id and open_by_handler.

1 files changed, 49 insertions, 3 deletions

diff --git a/mysql-test/r/sp-error.result b/mysql-test/r/sp-error.result
index 300fa42f3ad..b81f8ea64c9 100644
--- a/mysql-test/r/sp-error.result
+++ b/mysql-test/r/sp-error.result
@@ -1428,7 +1428,6 @@ create function bug20701() returns varchar(25) binary return "test";
 ERROR 42000: This version of MySQL doesn't yet support 'return value collation'
 create function bug20701() returns varchar(25) return "test";
 drop function bug20701;
-End of 5.1 tests
 create procedure proc_26503_error_1()
 begin
 retry:
@@ -1530,6 +1529,53 @@ return 1;
 end|
 ERROR HY000: Not allowed to set autocommit from a stored function or trigger
 create trigger t1
-before insert on t2 for each row set password = password('foo');
-delimiter ;|
+before insert on t2 for each row set password = password('foo');|
 ERROR HY000: Not allowed to set autocommit from a stored function or trigger
+drop function if exists f1;
+drop function if exists f2;
+drop table if exists t1, t2;
+create function f1() returns int
+begin
+drop temporary table t1;
+return 1;
+end|
+create temporary table t1 as select f1();
+ERROR HY000: Can't reopen table: 't1'
+create function f2() returns int
+begin
+create temporary table t2 as select f1();
+return 1;
+end|
+create temporary table t1 as select f2();
+ERROR HY000: Can't reopen table: 't1'
+drop function f1;
+drop function f2;
+create function f1() returns int
+begin
+drop temporary table t2,t1;
+return 1;
+end|
+create function f2() returns int
+begin
+create temporary table t2 as select f1();
+return 1;
+end|
+create temporary table t1 as select f2();
+ERROR HY000: Can't reopen table: 't2'
+drop function f1;
+drop function f2;
+create temporary table t2(a int);
+select * from t2;
+a
+create function f2() returns int
+begin
+drop temporary table t2;
+return 1;
+end|
+select f2();
+f2()
+1
+drop function f2;
+drop table t2;
+ERROR 42S02: Unknown table 't2'
+End of 5.1 tests