Custom module permission option not available
Here is to implement the hook permission 

/**
 * Implements hook_permission().
 */
function form_example_permission() {
  return array(
    'administer your module' =&gt; array(
      'title' =&gt; t('Administer permission for your module'),
      'description' =&gt; t('Some description that would appear on the permission page..'),
    ),
  );
}