From a7e3008ab3d368c2e2957b346647a7656d638e5c Mon Sep 17 00:00:00 2001
From: Eugene Kosov <claprix@yandex.ru>
Date: Wed, 30 Oct 2019 12:53:25 +0300
Subject: [PATCH] MDEV-20926 UBSAN: load of value 165, which is not a valid
 value for type bool

Basicaly it's an uninitialized read. 165 is 0xa5 which comes from TRASH_ALLOC()

Fix by calling a class ctor which initializes problematic
TMP_TABLE_PARAM::force_copy_fields field
---
 sql/sql_show.cc | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/sql/sql_show.cc b/sql/sql_show.cc
index d8f65c74448..c63b8b0f8a8 100644
--- a/sql/sql_show.cc
+++ b/sql/sql_show.cc
@@ -7708,8 +7708,7 @@ TABLE *create_schema_table(THD *thd, TABLE_LIST *table_list)
     item->maybe_null= (fields_info->field_flags & MY_I_S_MAYBE_NULL);
     field_count++;
   }
-  TMP_TABLE_PARAM *tmp_table_param =
-    (TMP_TABLE_PARAM*) (thd->alloc(sizeof(TMP_TABLE_PARAM)));
+  TMP_TABLE_PARAM *tmp_table_param = new TMP_TABLE_PARAM;
   tmp_table_param->init();
   tmp_table_param->table_charset= cs;
   tmp_table_param->field_count= field_count;