A fix and a test case for Bug#56540 "Exception (crash) in

sql_show.cc during rqg_info_schema test on Windows".

Ensure we do not access freed memory when filling
information_schema.views when one of the views
could not be properly opened.

mysql-test/r/information_schema.result

@@ -1807,3 +1807,47 @@ USING (TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME)
 WHERE COLUMNS.TABLE_SCHEMA = 'test'
 AND COLUMNS.TABLE_NAME = 't1';
 TABLE_SCHEMA	TABLE_NAME	COLUMN_NAME	CONSTRAINT_CATALOG	CONSTRAINT_SCHEMA	CONSTRAINT_NAME	TABLE_CATALOG	ORDINAL_POSITION	POSITION_IN_UNIQUE_CONSTRAINT	REFERENCED_TABLE_SCHEMA	REFERENCED_TABLE_NAME	REFERENCED_COLUMN_NAME	TABLE_CATALOG	ORDINAL_POSITION	COLUMN_DEFAULT	IS_NULLABLE	DATA_TYPE	CHARACTER_MAXIMUM_LENGTH	CHARACTER_OCTET_LENGTH	NUMERIC_PRECISION	NUMERIC_SCALE	CHARACTER_SET_NAME	COLLATION_NAME	COLUMN_TYPE	COLUMN_KEY	EXTRA	PRIVILEGES	COLUMN_COMMENT
+#
+# A test case for Bug#56540 "Exception (crash) in sql_show.cc
+# during rqg_info_schema test on Windows"
+# Ensure that we never access memory of a closed table,
+# in particular, never access table->field[] array.
+# Before the fix, the below test case, produced
+# valgrind errors.
+#
+drop table if exists t1;
+drop view if exists v1;
+create table t1 (a int, b int);
+create view v1 as select t1.a, t1.b from t1;
+alter table t1 change b c int;
+lock table t1 read;
+# --> connection con1
+flush tables;
+# --> connection default
+select * from information_schema.views;
+TABLE_CATALOG	def
+TABLE_SCHEMA	test
+TABLE_NAME	v1
+VIEW_DEFINITION	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1`
+CHECK_OPTION	NONE
+IS_UPDATABLE	
+DEFINER	root@localhost
+SECURITY_TYPE	DEFINER
+CHARACTER_SET_CLIENT	latin1
+COLLATION_CONNECTION	latin1_swedish_ci
+Warnings:
+Level	Warning
+Code	1356
+Message	View 'test.v1' references invalid table(s) or column(s) or function(s) or definer/invoker of view lack rights to use them
+unlock tables;
+#
+# Cleanup.
+#
+# --> connection con1
+# Reaping 'flush tables'
+# --> connection default
+drop table t1;
+drop view v1;
+#
+# End of 5.5 tests
+#

mysql-test/t/information_schema.test

@@ -1555,3 +1555,56 @@ WHERE COLUMNS.TABLE_SCHEMA = 'test'
 AND COLUMNS.TABLE_NAME = 't1';
 
 
+--echo #
+--echo # A test case for Bug#56540 "Exception (crash) in sql_show.cc
+--echo # during rqg_info_schema test on Windows"
+--echo # Ensure that we never access memory of a closed table,
+--echo # in particular, never access table->field[] array.
+--echo # Before the fix, the below test case, produced
+--echo # valgrind errors.
+--echo #
+
+--disable_warnings
+drop table if exists t1;
+drop view if exists v1;
+--enable_warnings
+
+create table t1 (a int, b int);
+create view v1 as select t1.a, t1.b from t1;
+alter table t1 change b c int;
+lock table t1 read;
+connect(con1, localhost, root,,);
+--echo # --> connection con1
+connection con1;
+send flush tables;
+--echo # --> connection default
+connection default;
+let $wait_condition=
+  select count(*) = 1 from information_schema.processlist
+    where state = "Waiting for table flush" and
+          info = "flush tables";
+--source include/wait_condition.inc
+--vertical_results
+select * from information_schema.views;
+--horizontal_results
+unlock tables;
+
+--echo #
+--echo # Cleanup.
+--echo #
+
+--echo # --> connection con1
+connection con1;
+--echo # Reaping 'flush tables'
+reap;
+disconnect con1;
+--source include/wait_until_disconnected.inc
+--echo # --> connection default
+connection default;
+drop table t1;
+drop view v1;
+
+
+--echo #
+--echo # End of 5.5 tests
+--echo #

sql/sql_base.cc

@@ -2902,8 +2902,12 @@ bool open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
     */
     if (check_and_update_table_version(thd, table_list, share))
       goto err_unlock;
-    if (table_list->i_s_requested_object &  OPEN_TABLE_ONLY)
+    if (table_list->i_s_requested_object & OPEN_TABLE_ONLY)
+    {
+      my_error(ER_NO_SUCH_TABLE, MYF(0), table_list->db,
+               table_list->table_name);
       goto err_unlock;
+    }
 
     /* Open view */
     if (open_new_frm(thd, share, alias,
@@ -2931,7 +2935,11 @@ bool open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
   */
 
   if (table_list->i_s_requested_object &  OPEN_VIEW_ONLY)
+  {
+    my_error(ER_NO_SUCH_TABLE, MYF(0), table_list->db,
+             table_list->table_name);
     goto err_unlock;
+  }
 
   if (!(flags & MYSQL_OPEN_IGNORE_FLUSH))
   {

sql/sql_show.cc

@@ -4934,18 +4934,29 @@ static int get_schema_views_record(THD *thd, TABLE_LIST *tables,
     else
       table->field[4]->store(STRING_WITH_LEN("NONE"), cs);
 
-    if (table->pos_in_table_list->table_open_method &
-        OPEN_FULL_TABLE)
+    /*
+      Only try to fill in the information about view updatability
+      if it is requested as part of the top-level query (i.e.
+      it's select * from i_s.views, as opposed to, say, select
+      security_type from i_s.views).  Do not try to access the
+      underlying tables if there was an error when opening the
+      view: all underlying tables are released back to the table
+      definition cache on error inside open_normal_and_derived_tables().
+      If a field is not assigned explicitly, it defaults to NULL.
+    */
+    if (res == FALSE &&
+        table->pos_in_table_list->table_open_method & OPEN_FULL_TABLE)
     {
       updatable_view= 0;
       if (tables->algorithm != VIEW_ALGORITHM_TMPTABLE)
       {
         /*
-          We should use tables->view->select_lex.item_list here and
-          can not use Field_iterator_view because the view always uses
-          temporary algorithm during opening for I_S and
-          TABLE_LIST fields 'field_translation' & 'field_translation_end'
-          are uninitialized is this case.
+          We should use tables->view->select_lex.item_list here
+          and can not use Field_iterator_view because the view
+          always uses temporary algorithm during opening for I_S
+          and TABLE_LIST fields 'field_translation'
+          & 'field_translation_end' are uninitialized is this
+          case.
         */
         List<Item> *fields= &tables->view->select_lex.item_list;
         List_iterator<Item> it(*fields);