From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754086Ab0KRBdg (ORCPT ); Wed, 17 Nov 2010 20:33:36 -0500 Received: from kroah.org ([198.145.64.141]:35503 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753678Ab0KRBc4 (ORCPT ); Wed, 17 Nov 2010 20:32:56 -0500 Date: Wed, 17 Nov 2010 17:27:34 -0800 From: Greg KH To: Alan Cox Cc: Kay Sievers , Valdis.Kletnieks@vt.edu, Lennart Poettering , linux-kernel , Werner Fink , Jiri Slaby Subject: Re: tty: add 'active' sysfs attribute to tty0 and console device Message-ID: <20101118012734.GA8558@kroah.com> References: <20101116171447.29336514@lxorguk.ukuu.org.uk> <20101116195538.7fa66b97@lxorguk.ukuu.org.uk> <20101116213622.GA17824@tango.0pointer.de> <20101116225619.5fa7ef8b@lxorguk.ukuu.org.uk> <20101116231023.GB27594@tango.0pointer.de> <25482.1290031268@localhost> <20101117235647.00766e32@lxorguk.ukuu.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20101117235647.00766e32@lxorguk.ukuu.org.uk> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 17, 2010 at 11:56:47PM +0000, Alan Cox wrote: > > Brilliant conclusion. If you have mounted it, you own it. But you can > > not make your inactive session mount another new one. It's like this > > since ages. Hint: try stuff before hitting reply too fast. :) > > Except during the window when screen switching, or of course you could > just ssh in remotely and gdb or similar a process with it as controlling > tty running on your console and issue a vt switch back, then mount it. > Ironically the move from a root owned X server has made that much simpler > to automate, although it was always possible. > > Given you can often guess from the idle data if the victim has gone away > from the box it's not ideal. Even better any mess will appear on my > display and get hidden when I flip it back. > > The only way to stop that is to make use of the display locking facility > which takes us back where we began in saying that a usable interface is > going to need to lock the display. > > At that point the current console owner has to choose to allow the > console to be switched which can be limited effectively to physical > console access and done synchronously. In turn that means to abuse it I > already have physical access to the other users key so could just as > easily steal it and the software security is therefore sufficient. Ok, we are way-off-topic here from the original points. Which are: - the existing ioctl is broken and no userspace program can use it properly, so it might as well be removed. - Kay's patch is one proposed solution for what userspace is wanting to learn about ttys. Werner's is another one. So, what to do? I can do any one, or multiple things from the following options: - disable the existing ioctl to return an error so that no new userspace program starts to use it thinking it is valid - accept Werner's patch for those who like proc files - accept Kay's patch Any suggestions? thanks, greg k-h