linux-kernel - Should snd_card_free() check for null pointer?

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Message-ID: <56B9F7F8.1000605@redhat.com>
Date:	Tue, 9 Feb 2016 15:30:16 +0100
From:	Jerome Marchand <jmarchan@...hat.com>
To:	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>
Cc:	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Should snd_card_free() check for null pointer?

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?

Thanks,
Jerome

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