On Wed, 10 Feb 2016 08:41:38 +0100, Jerome Marchand wrote:
----- Original Message -----
From: "Takashi Iwai" tiwai@suse.de To: "Jerome Marchand" jmarchan@redhat.com Cc: "Jaroslav Kysela" perex@perex.cz, 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