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).

1 files changed, 1 insertions, 1 deletions

diff --git a/sql/event_db_repository.cc b/sql/event_db_repository.cc
index 4451e763ff7..9a33b33d8c9 100644
--- a/sql/event_db_repository.cc
+++ b/sql/event_db_repository.cc
@@ -549,7 +549,7 @@ Event_db_repository::open_event_table(THD *thd, enum thr_lock_type lock_type,
 
   if (simple_open_n_lock_tables(thd, &tables))
   {
-    close_thread_tables(thd, FALSE, FALSE);
+    close_thread_tables(thd);
     DBUG_RETURN(TRUE);
   }