From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756521Ab1FCWIf (ORCPT ); Fri, 3 Jun 2011 18:08:35 -0400 Received: from earthlight.etchedpixels.co.uk ([81.2.110.250]:48821 "EHLO www.etchedpixels.co.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754156Ab1FCWIe (ORCPT ); Fri, 3 Jun 2011 18:08:34 -0400 Date: Fri, 3 Jun 2011 23:10:28 +0100 From: Alan Cox To: Russ Gorby Cc: Greg Kroah-Hartman , linux-kernel@vger.kernel.org, suhail.ahmed@intel.com Subject: Re: [PATCH 5/5] tty: n_gsm: Fixed NULL ptr OOPs in tty_write_room() Message-ID: <20110603231028.5c267e60@lxorguk.ukuu.org.uk> In-Reply-To: <1307127821-21665-6-git-send-email-russ.gorby@intel.com> References: <[PATCH 0/5] N_GSM patchset : 06/03/2011> <1307127821-21665-6-git-send-email-russ.gorby@intel.com> X-Mailer: Claws Mail 3.7.9 (GTK+ 2.22.0; x86_64-redhat-linux-gnu) Face: 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 Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 3 Jun 2011 12:03:41 -0700 Russ Gorby wrote: > We saw a case where gsmld_output was called after the MUX > was shutdown. In this case gsm->tty was null so tty_write_room(NULL) > was called which resulted in an exception. This is papering over a problem. It shouldn't be happening. Do you have a copy of the backtrace of the event and does it occur a lot. If it's a one off freak event so far then instead add if (gsm->tty == NULL) { WARN_ON(1); return -ENXIO; } so we get dumps from it and the box survives when it occurs. That'll get us traces to nail it properly. For one your patch is not a valid ultimate fix because if it can occur what stops gsm->tty changing as it occurs.