How to get attachments for a specific post type?

$posts = get_posts( array( 'post_type' => 'post', 'posts_per_page' => -1 ) );

     foreach ( $posts as $post ) {

         $attachments = get_children( array (
            'post_parent'    => $post->ID,
            'post_type'      => 'attachment',
            'post_mime_type' => 'image',
            'post_per_page'  => 25
        ), ARRAY_A );


      if( $attachments ) {
         //continue with what you were doing

      }
   }