WordPress upload file action hook

Try this way, should work well

function cpt_from_attachment($attachment_ID)
    {          
    global $current_user;
    get_currentuserinfo();

    $attachment_post = get_post( $attachment_ID );

    $type = get_post_mime_type($attachment_ID);

    // DO WHAT YOU NEED
}

add_action("add_attachment", 'cpt_from_attachment');