From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934348Ab3BTQkj (ORCPT ); Wed, 20 Feb 2013 11:40:39 -0500 Received: from mail-ea0-f177.google.com ([209.85.215.177]:62427 "EHLO mail-ea0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933477Ab3BTQki (ORCPT ); Wed, 20 Feb 2013 11:40:38 -0500 Message-ID: <5124FC82.5040305@suse.cz> Date: Wed, 20 Feb 2013 17:40:34 +0100 From: Jiri Slaby User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:19.0) Gecko/20130124 Thunderbird/19.0 MIME-Version: 1.0 To: Karel Zak CC: gregkh@linuxfoundation.org, alan@linux.intel.com, jirislaby@gmail.com, linux-kernel@vger.kernel.org, Mauro Carvalho Chehab , Bryan Mason Subject: Re: [PATCH] TTY: do not reset master's packet mode References: <1358288782-2946-1-git-send-email-jslaby@suse.cz> <20130220131903.GA8501@x2.net.home> In-Reply-To: <20130220131903.GA8501@x2.net.home> X-Enigmail-Version: 1.6a1pre Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/20/2013 02:19 PM, Karel Zak wrote: > On Tue, Jan 15, 2013 at 11:26:22PM +0100, Jiri Slaby wrote: >> Now that login from util-linux is forced to drop all references to a >> TTY which it wants to hangup (to reach reference count 1) we are >> seeing issues with telnet. When login closes its last reference to the >> slave PTY, it also resets packet mode on the *master* side. And we >> have a race here. > > [...] > >> By this I am resurrecting an old bug, see References. We are hitting >> it regularly now, i.e. with updated util-linux, ergo login. >> >> Here, I am changing a behavior introduced back in 2.1 times. It would >> better have a long time testing before goes upstream. > > It would be nice to found a quick way how to resolve this problem, > because telnet+login is broken now... and for end users it seems like > a regression. Oh, the patch is in the TTY tree and I suppose it will go to 3.9-rc1 (and to stable as we will get to same later -rc -- to have some testing). > Maybe the requirement (patch) to close all references to TTY before > hangup should reverted or we can make an exception in login(1) code to > keep TTY open when login(1) is executed with -h (as used by telned). If we reverted the patch in login, we would have to revert also a patch in the TTY which closes a window allowing you to crash a kernel at will (in fact that patch disallows multiple opens when hanging up a terminal. IOW only the one to hang the terminal is allowed to have it opened.) -- js suse labs