MDEV-28403 ASAN heap-use-after-free in String::copy / get_field_default_value

This reverts commit 5ba77222
but keeps the test. A different fix for

MDEV-21028 Server crashes in Query_arena::set_query_arena upon SELECT from view

internal temporary tables should use THD as expr_area

mysql-test/r/func_default.result

@@ -167,8 +167,8 @@ create algorithm=temptable view v1 as select * from t1;
 create algorithm=merge     view v2 as select * from t1;
 select default(a) = now() from v1;
 default(a) = now()
-NULL
-NULL
+1
+1
 select default(a) = now() from v2;
 default(a) = now()
 1
@@ -191,16 +191,29 @@ default(v1)
 2001-01-01 10:20:30
 select default(v1) from (select v1 from t1 group by v1) dt;
 default(v1)
-0000-00-00 00:00:00
+2001-01-01 10:20:30
 drop table t1;
 create table t1 (a text default '');
 create algorithm=temptable view v1 as select * from t1;
 insert into t1 values ('a');
 select default(a) from v1;
 default(a)
-NULL
+
 drop view v1;
 drop table t1;
 #
+# MDEV-28403 ASAN heap-use-after-free in String::copy / get_field_default_value
+#
+create table t (a blob default 'x');
+create view v as select * from t;
+insert into t () values ();
+update t set a = default;
+select table_name,column_name,column_default from information_schema.columns where table_name = 'v';
+table_name	v
+column_name	a
+column_default	'x'
+drop view v;
+drop table t;
+#
 # End of 10.2 tests
 #

mysql-test/t/func_default.test

@@ -165,6 +165,17 @@ select default(a) from v1;
 drop view v1;
 drop table t1;
 
+--echo #
+--echo # MDEV-28403 ASAN heap-use-after-free in String::copy / get_field_default_value
+--echo #
+create table t (a blob default 'x');
+create view v as select * from t;
+insert into t () values ();
+update t set a = default;
+query_vertical select table_name,column_name,column_default from information_schema.columns where table_name = 'v';
+drop view v;
+drop table t;
+
 --echo #
 --echo # End of 10.2 tests
 --echo #

sql/sql_select.cc

@@ -16333,8 +16333,7 @@ Field *create_tmp_field_from_field(THD *thd, Field *org_field,
       table->s->db_create_options|= HA_OPTION_PACK_RECORD;
     else if (org_field->type() == FIELD_TYPE_DOUBLE)
       ((Field_double *) new_field)->not_fixed= TRUE;
-    new_field->vcol_info= new_field->default_value=
-      new_field->check_constraint= 0;
+    new_field->vcol_info= 0;
     new_field->cond_selectivity= 1.0;
     new_field->next_equal_field= NULL;
     new_field->option_list= NULL;
@@ -16901,6 +16900,7 @@ create_tmp_table(THD *thd, TMP_TABLE_PARAM *param, List<Item> &fields,
   table->intersect_keys.init();
   table->keys_in_use_for_query.init();
   table->no_rows_with_nulls= param->force_not_null_cols;
+  table->expr_arena= thd;
 
   table->s= share;
   init_tmp_table_share(thd, share, "", 0, "(temporary)", tmpname);