linux-kernel - Re: [PATCH] ASoC: Intel: Skylake: fix dereference before NULL check on ebus

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Message-ID: <20170419133249.ac3sdmn7kqjbxaii@mwanda>
Date:   Wed, 19 Apr 2017 16:32:49 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Colin King <colin.king@...onical.com>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Vinod Koul <vinod.koul@...el.com>,
        Jeeja KP <jeeja.kp@...el.com>,
        Jayachandran B <jayachandran.b@...el.com>,
        "Subhransu S . Prusty" <subhransu.s.prusty@...el.com>,
        Dharageswari R <dharageswari.r@...el.com>,
        Pardha Saradhi K <pardha.saradhi.kesapragada@...el.com>,
        Yong Zhi <yong.zhi@...el.com>, alsa-devel@...a-project.org,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ASoC: Intel: Skylake: fix dereference before NULL check
 on ebus

On Wed, Apr 19, 2017 at 01:16:13PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> ebus is being NULL checked however it is being dereferenced
> earlier on the assignment bus = ebus_to_hbus(ebus).  Fix this
> by moving the assignment to after the NULL check on ebus to
> avoid a NULL pointer dereference error.
> 

ebus_to_hbus() doesn't dereference "ebus" it just uses it for pointer
math.

#define ebus_to_hbus(ebus)      (&(ebus)->bus)

If you pass a NULL to there, it returns an offset starting from NULL but
it doesn't Oops.

regards,
dan carpenter