MDEV-28546 : Possible to write/update with read_only=ON and not a SUPER privilege

Function wsrep_read_only_option was already removed in commit
d54bc3c0 because it could cause race condition on variable
opt_readonly so that value OFF can become permanent.
Removed function again and added test case. Note that writes
to TEMPORARY tables are still allowed when read_only=ON.

mysql-test/suite/galera/r/galera_read_only.result

@@ -17,10 +17,18 @@ connect foo_node_2,127.0.0.1,foo,,test,$port_2,;
 connection foo_node_2;
 INSERT INTO t1 VALUES (2);
 ERROR HY000: The MariaDB server is running with the --read-only option so it cannot execute this statement
+CREATE TEMPORARY TABLE t2(id int not null primary key) engine=innodb;
+INSERT INTO t2 values (1);
+DROP TABLE t2;
 connection node_2;
-SELECT COUNT(*) = 1 FROM t1;
-COUNT(*) = 1
+SELECT COUNT(*) AS EXPECT_1 FROM t1;
+EXPECT_1
 1
+connection node_2;
+SET GLOBAL read_only=TRUE;
+CREATE TEMPORARY TABLE t2(id int not null primary key) engine=innodb;
+INSERT INTO t2 values (1);
+DROP TABLE t2;
 SET GLOBAL read_only=FALSE;
 DROP TABLE t1;
 DROP USER foo@localhost;

mysql-test/suite/galera/t/galera_read_only.test

@@ -28,9 +28,20 @@ CREATE USER foo@localhost;
 --connection foo_node_2
 --error ER_OPTION_PREVENTS_STATEMENT
 INSERT INTO t1 VALUES (2);
+# Writes to temporary tables are allowed
+CREATE TEMPORARY TABLE t2(id int not null primary key) engine=innodb;
+INSERT INTO t2 values (1);
+DROP TABLE t2;
 
 --connection node_2
-SELECT COUNT(*) = 1 FROM t1;
+SELECT COUNT(*) AS EXPECT_1 FROM t1;
+
+--connection node_2
+SET GLOBAL read_only=TRUE;
+# Writes to temporary tables are allowed
+CREATE TEMPORARY TABLE t2(id int not null primary key) engine=innodb;
+INSERT INTO t2 values (1);
+DROP TABLE t2;
 
 # Cleanup
 SET GLOBAL read_only=FALSE;

sql/sql_parse.cc

@@ -1468,22 +1468,6 @@ static bool deny_updates_if_read_only_option(THD *thd, TABLE_LIST *all_tables)
 }
 
 #ifdef WITH_WSREP
-static my_bool wsrep_read_only_option(THD *thd, TABLE_LIST *all_tables)
-{
-  int opt_readonly_saved = opt_readonly;
-  ulong flag_saved = (ulong)(thd->security_ctx->master_access & SUPER_ACL);
-
-  opt_readonly = 0;
-  thd->security_ctx->master_access &= ~SUPER_ACL;
-
-  my_bool ret = !deny_updates_if_read_only_option(thd, all_tables);
-
-  opt_readonly = opt_readonly_saved;
-  thd->security_ctx->master_access |= flag_saved;
-
-  return ret;
-}
-
 static void wsrep_copy_query(THD *thd)
 {
   thd->wsrep_retry_command   = thd->get_command();
@@ -7807,7 +7791,7 @@ static bool wsrep_mysql_parse(THD *thd, char *rawbuf, uint length,
 {
   bool is_autocommit=
     !thd->in_multi_stmt_transaction_mode()                  &&
-    wsrep_read_only_option(thd, thd->lex->query_tables);
+    !thd->wsrep_applier;
   bool retry_autocommit;
   do
   {