BUG#25250768: WRITING ON A READ_ONLY=ON SERVER WITHOUT SUPER

              PRIVILEGE.

Backport from mysql-5.7 to mysql-5.5 and mysql-5.6.

BUG#13969578: TEMPORARY TABLE IN A DATABASE ON A READ-ONLY
                  INSTANCE CAN BE OVERWRITTEN

Analysis:
========

Creation or modification of a persistent table by a non-super user
is NOT ALLOWED in read_only mode. Only TEMPORARY tables are allowed
to be created or modified in read_only mode. But the creation of
a persistent table was being allowed when a temporary table of
the same name existed.

The routine which denies updating a non-temporary table in a
read_only mode does not handle the case of creation of a regular
table when a temporary table of the same exists.

Fix:
===
Handled the condition where an attempt is made to create a persistent
table having the same name as that of the temporary table. Hence
the creation of a persistent table by a non-super user when a
temporary table of the same exists is denied under read_only mode.

sql/sql_parse.cc

@@ -822,14 +822,18 @@ static my_bool deny_updates_if_read_only_option(THD *thd,
     (lex->sql_command == SQLCOM_CREATE_TABLE) &&
     (lex->create_info.options & HA_LEX_CREATE_TMP_TABLE);
 
+  const my_bool create_real_tables=
+    (lex->sql_command == SQLCOM_CREATE_TABLE) &&
+    !(lex->create_info.options & HA_LEX_CREATE_TMP_TABLE);
+
   const my_bool drop_temp_tables= 
     (lex->sql_command == SQLCOM_DROP_TABLE) &&
     lex->drop_temporary;
 
   const my_bool update_real_tables=
-    some_non_temp_table_to_be_updated(thd, all_tables) &&
-    !(create_temp_tables || drop_temp_tables);
-
+    ((create_real_tables ||
+      some_non_temp_table_to_be_updated(thd, all_tables)) &&
+     !(create_temp_tables || drop_temp_tables));
 
   const my_bool create_or_drop_databases=
     (lex->sql_command == SQLCOM_CREATE_DB) ||