From mboxrd@z Thu Jan 1 00:00:00 1970 From: Takashi Iwai Subject: Re: Should snd_card_free() check for null pointer? Date: Tue, 09 Feb 2016 22:56:39 +0100 Message-ID: References: <56B9F7F8.1000605@redhat.com> Mime-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Return-path: In-Reply-To: <56B9F7F8.1000605@redhat.com> Sender: linux-kernel-owner@vger.kernel.org To: Jerome Marchand Cc: Jaroslav Kysela , alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org List-Id: alsa-devel@alsa-project.org 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. thanks, Takashi