Bug#24630 Subselect query crashes mysqld

The crash happens because second filling of the same I_S table happens in
case of subselect with order by. table->sort.io_cache previously allocated
in create_sort_index() is deleted during second filling
(function get_schema_tables_result). There are two places where
I_S table can be filled: JOIN::exec and create_sort_index().
To fix the bug we should check if the table was already filled
in one of these places and skip processing of the table in second.

mysql-test/r/information_schema.result

@@ -1278,3 +1278,40 @@ table_name
 t1
 t2
 drop table t1,t2;
+select 1 as f1 from information_schema.tables  where "CHARACTER_SETS"=
+(select cast(table_name as char)  from information_schema.tables
+order by table_name limit 1) limit 1;
+f1
+1
+select t.table_name, group_concat(t.table_schema, '.', t.table_name),
+count(*) as num1
+from information_schema.tables t
+inner join information_schema.columns c1
+on t.table_schema = c1.table_schema AND t.table_name = c1.table_name
+where t.table_schema = 'information_schema' and
+c1.ordinal_position =
+(select isnull(c2.column_type) -
+isnull(group_concat(c2.table_schema, '.', c2.table_name)) +
+count(*) as num
+from information_schema.columns c2 where
+c2.table_schema='information_schema' and
+(c2.column_type = 'varchar(7)' or c2.column_type = 'varchar(20)')
+group by c2.column_type order by num limit 1)
+group by t.table_name order by num1, t.table_name;
+table_name	group_concat(t.table_schema, '.', t.table_name)	num1
+CHARACTER_SETS	information_schema.CHARACTER_SETS	1
+COLLATIONS	information_schema.COLLATIONS	1
+COLLATION_CHARACTER_SET_APPLICABILITY	information_schema.COLLATION_CHARACTER_SET_APPLICABILITY	1
+COLUMNS	information_schema.COLUMNS	1
+COLUMN_PRIVILEGES	information_schema.COLUMN_PRIVILEGES	1
+KEY_COLUMN_USAGE	information_schema.KEY_COLUMN_USAGE	1
+ROUTINES	information_schema.ROUTINES	1
+SCHEMATA	information_schema.SCHEMATA	1
+SCHEMA_PRIVILEGES	information_schema.SCHEMA_PRIVILEGES	1
+STATISTICS	information_schema.STATISTICS	1
+TABLES	information_schema.TABLES	1
+TABLE_CONSTRAINTS	information_schema.TABLE_CONSTRAINTS	1
+TABLE_PRIVILEGES	information_schema.TABLE_PRIVILEGES	1
+TRIGGERS	information_schema.TRIGGERS	1
+USER_PRIVILEGES	information_schema.USER_PRIVILEGES	1
+VIEWS	information_schema.VIEWS	1

mysql-test/t/information_schema.test

@@ -999,4 +999,28 @@ where table_schema = 'test' and table_name not in
  where table_schema = 'test' and column_name = 'f3');
 drop table t1,t2;
 
+
+#
+# Bug#24630  Subselect query crashes mysqld
+#
+select 1 as f1 from information_schema.tables  where "CHARACTER_SETS"=
+(select cast(table_name as char)  from information_schema.tables
+ order by table_name limit 1) limit 1;
+
+select t.table_name, group_concat(t.table_schema, '.', t.table_name),
+       count(*) as num1
+from information_schema.tables t
+inner join information_schema.columns c1
+on t.table_schema = c1.table_schema AND t.table_name = c1.table_name
+where t.table_schema = 'information_schema' and
+        c1.ordinal_position =
+        (select isnull(c2.column_type) -
+         isnull(group_concat(c2.table_schema, '.', c2.table_name)) +
+         count(*) as num
+         from information_schema.columns c2 where
+         c2.table_schema='information_schema' and
+         (c2.column_type = 'varchar(7)' or c2.column_type = 'varchar(20)')
+          group by c2.column_type order by num limit 1)
+group by t.table_name order by num1, t.table_name;
+
 # End of 5.0 tests.

sql/mysql_priv.h

@@ -932,7 +932,8 @@ int fill_schema_user_privileges(THD *thd, TABLE_LIST *tables, COND *cond);
 int fill_schema_schema_privileges(THD *thd, TABLE_LIST *tables, COND *cond);
 int fill_schema_table_privileges(THD *thd, TABLE_LIST *tables, COND *cond);
 int fill_schema_column_privileges(THD *thd, TABLE_LIST *tables, COND *cond);
-bool get_schema_tables_result(JOIN *join);
+bool get_schema_tables_result(JOIN *join,
+                              enum enum_schema_table_state executed_place);
 #define is_schema_db(X) \
   !my_strcasecmp(system_charset_info, information_schema_name.str, (X))
 

sql/sql_select.cc

@@ -1505,7 +1505,7 @@ JOIN::exec()
 
   if ((curr_join->select_lex->options & OPTION_SCHEMA_TABLE) &&
       !thd->lex->describe &&
-      get_schema_tables_result(curr_join))
+      get_schema_tables_result(curr_join, PROCESSED_BY_JOIN_EXEC))
   {
     DBUG_VOID_RETURN;
   }
@@ -12372,7 +12372,7 @@ create_sort_index(THD *thd, JOIN *join, ORDER *order,
   /* Fill schema tables with data before filesort if it's necessary */
   if ((join->select_lex->options & OPTION_SCHEMA_TABLE) &&
       !thd->lex->describe &&
-      get_schema_tables_result(join))
+      get_schema_tables_result(join, PROCESSED_BY_CREATE_SORT_INDEX))
     goto err;
 
   if (table->s->tmp_table)

sql/sql_show.cc

@@ -3938,13 +3938,15 @@ int make_schema_select(THD *thd, SELECT_LEX *sel,
   SYNOPSIS
     get_schema_tables_result()
     join  join which use schema tables
+    executed_place place where I_S table processed
 
   RETURN
     FALSE success
     TRUE  error
 */
 
-bool get_schema_tables_result(JOIN *join)
+bool get_schema_tables_result(JOIN *join,
+                              enum enum_schema_table_state executed_place)
 {
   JOIN_TAB *tmp_join_tab= join->join_tab+join->tables;
   THD *thd= join->thd;
@@ -3964,14 +3966,24 @@ bool get_schema_tables_result(JOIN *join)
       bool is_subselect= (&lex->unit != lex->current_select->master_unit() &&
                           lex->current_select->master_unit()->item);
       /*
-        The schema table is already processed and 
+        If schema table is already processed and
-        the statement is not a subselect.
+        the statement is not a subselect then
-        So we don't need to handle this table again.
+        we don't need to fill this table again.
+        If schema table is already processed and
+        schema_table_state != executed_place then
+        table is already processed and
+        we should skip second data processing.
       */
-      if (table_list->is_schema_table_processed && !is_subselect)
+      if (table_list->schema_table_state &&
+          (!is_subselect || table_list->schema_table_state != executed_place))
         continue;
 
-      if (is_subselect) // is subselect
+      /*
+        if table is used in a subselect and
+        table has been processed earlier with the same
+        'executed_place' value then we should refresh the table.
+      */
+      if (table_list->schema_table_state && is_subselect)
       {
         table_list->table->file->extra(HA_EXTRA_NO_CACHE);
         table_list->table->file->extra(HA_EXTRA_RESET_STATE);
@@ -3988,10 +4000,10 @@ bool get_schema_tables_result(JOIN *join)
       {
         result= 1;
         join->error= 1;
-        table_list->is_schema_table_processed= TRUE;
+        table_list->schema_table_state= executed_place;
         break;
       }
-      table_list->is_schema_table_processed= TRUE;
+      table_list->schema_table_state= executed_place;
     }
   }
   thd->no_warnings_for_error= 0;

sql/table.cc

@@ -3031,7 +3031,7 @@ void st_table_list::reinit_before_use(THD *thd)
   */
   table= 0;
   /* Reset is_schema_table_processed value(needed for I_S tables */
-  is_schema_table_processed= FALSE;
+  schema_table_state= NOT_PROCESSED;
 
   TABLE_LIST *embedded; /* The table at the current level of nesting. */
   TABLE_LIST *embedding= this; /* The parent nested table reference. */

sql/table.h

@@ -287,6 +287,12 @@ struct st_table {
   void reset_item_list(List<Item> *item_list) const;
 };
 
+enum enum_schema_table_state
+{ 
+  NOT_PROCESSED= 0,
+  PROCESSED_BY_CREATE_SORT_INDEX,
+  PROCESSED_BY_JOIN_EXEC
+};
 
 typedef struct st_foreign_key_info
 {
@@ -529,7 +535,6 @@ typedef struct st_table_list
   st_select_lex_unit *derived;		/* SELECT_LEX_UNIT of derived table */
   ST_SCHEMA_TABLE *schema_table;        /* Information_schema table */
   st_select_lex	*schema_select_lex;
-  bool is_schema_table_processed;
   /*
     True when the view field translation table is used to convert
     schema table fields for backwards compatibility with SHOW command.
@@ -638,6 +643,7 @@ typedef struct st_table_list
   */
   bool          prelocking_placeholder;
 
+  enum enum_schema_table_state schema_table_state;
   void calc_md5(char *buffer);
   void set_underlying_merge();
   int view_check_option(THD *thd, bool ignore_failure);