From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752376AbcBJIpf (ORCPT ); Wed, 10 Feb 2016 03:45:35 -0500 Received: from mx2.suse.de ([195.135.220.15]:40777 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751057AbcBJIpd (ORCPT ); Wed, 10 Feb 2016 03:45:33 -0500 Date: Wed, 10 Feb 2016 09:45:30 +0100 Message-ID: From: Takashi Iwai To: Jerome Marchand Cc: Jaroslav Kysela , alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org Subject: Re: Should snd_card_free() check for null pointer? In-Reply-To: <1378691295.23400498.1455090098781.JavaMail.zimbra@redhat.com> References: <56B9F7F8.1000605@redhat.com> <1378691295.23400498.1455090098781.JavaMail.zimbra@redhat.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/24.5 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 10 Feb 2016 08:41:38 +0100, Jerome Marchand wrote: > > ----- Original Message ----- > > From: "Takashi Iwai" > > To: "Jerome Marchand" > > Cc: "Jaroslav Kysela" , alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org > > Sent: Tuesday, February 9, 2016 10:56:39 PM > > Subject: Re: Should snd_card_free() check for null pointer? > > > > On Tue, 09 Feb 2016 15:30:16 +0100, > > Jerome Marchand wrote: > > > > > > Hi, > > > > > > Before commit f24640648186b (ALSA: Use standard device refcount for card > > > accounting), snd_card_free() would return -EINVAL on a null pointer. Now > > > it ends up in a null pointer dereference. There is at least one driver > > > that can call snd_card_free() with null argument: saa7134_alsa. It can > > > easily be triggered by just inserting and removing the module (no need > > > to have the hardware). > > > I don't think that is a rule, but it seems that the standard behavior of > > > *_free() functions is to check for null pointer. What do you think? > > > > Well, I have a mixed feeling about this. Allowing NULL sometimes > > makes the code easier. OTOH, caling snd_card_free() with NULL is > > really an unexpected situation, and if a driver does it, most likely > > it does something weird. > > > > So, at this moment, I would fix the caller side. But, it's not a > > final call, just my gut feeling. > > I have no strong opinion either way and I have a patch that fixes saa7134 > driver ready to be sent if that is your preference. Go ahead, let's fix saa7134 side for now. thanks, Takashi