Bug#35374491: Mysql read_ok_ex missing length check

Added a validity check on the length received from the network
for unknown trackers.

Change-Id: Idc7d229fc5905d919bd8c59907be1a5439a08efe

Author: gkodinov

sql-common/client.c

@@ -1011,6 +1011,7 @@ void read_ok_ex(MYSQL *mysql, ulong length) {
             len = (size_t)net_field_length_ll_safe(mysql, &pos, length,
                                                    &is_error);
             if (is_error) return;
+            if (!buffer_check_remaining(mysql, pos, length, len)) return;
             pos += len;
             break;
           }