From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752431AbcBJHls (ORCPT ); Wed, 10 Feb 2016 02:41:48 -0500 Received: from mx3-phx2.redhat.com ([209.132.183.24]:42939 "EHLO mx3-phx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751755AbcBJHlr (ORCPT ); Wed, 10 Feb 2016 02:41:47 -0500 Date: Wed, 10 Feb 2016 02:41:38 -0500 (EST) From: Jerome Marchand To: Takashi Iwai Cc: Jaroslav Kysela , alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org Message-ID: <1378691295.23400498.1455090098781.JavaMail.zimbra@redhat.com> In-Reply-To: References: <56B9F7F8.1000605@redhat.com> Subject: Re: Should snd_card_free() check for null pointer? MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.36.5.243] X-Mailer: Zimbra 8.0.6_GA_5922 (ZimbraWebClient - FF44 (Linux)/8.0.6_GA_5922) Thread-Topic: Should snd_card_free() check for null pointer? Thread-Index: a0MZ8iZYs4OrBZ8ZVhKDFDMmcyzUSQ== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- 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. Thanks, Jerome > > > thanks, > > Takashi >