From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S934496AbdDSNei (ORCPT <rfc822;w@1wt.eu>);
        Wed, 19 Apr 2017 09:34:38 -0400
Received: from aserp1040.oracle.com ([141.146.126.69]:39438 "EHLO
        aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S934184AbdDSNeg (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Wed, 19 Apr 2017 09:34:36 -0400
Date: Wed, 19 Apr 2017 16:32:49 +0300
From: Dan Carpenter <dan.carpenter@oracle.com>
To: Colin King <colin.king@canonical.com>
Cc: Liam Girdwood <lgirdwood@gmail.com>, Mark Brown <broonie@kernel.org>,
        Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.com>,
        Vinod Koul <vinod.koul@intel.com>, Jeeja KP <jeeja.kp@intel.com>,
        Jayachandran B <jayachandran.b@intel.com>,
        "Subhransu S . Prusty" <subhransu.s.prusty@intel.com>,
        Dharageswari R <dharageswari.r@intel.com>,
        Pardha Saradhi K <pardha.saradhi.kesapragada@intel.com>,
        Yong Zhi <yong.zhi@intel.com>, alsa-devel@alsa-project.org,
        kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ASoC: Intel: Skylake: fix dereference before NULL check
 on ebus
Message-ID: <20170419133249.ac3sdmn7kqjbxaii@mwanda>
References: <20170419121613.12353-1-colin.king@canonical.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20170419121613.12353-1-colin.king@canonical.com>
User-Agent: NeoMutt/20170113 (1.7.2)
X-Source-IP: userv0022.oracle.com [156.151.31.74]
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Wed, Apr 19, 2017 at 01:16:13PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.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