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 S1752573AbdA3I02 (ORCPT <rfc822;w@1wt.eu>);
        Mon, 30 Jan 2017 03:26:28 -0500
Received: from metis.ext.4.pengutronix.de ([92.198.50.35]:58489 "EHLO
        metis.ext.4.pengutronix.de" rhost-flags-OK-OK-OK-OK)
        by vger.kernel.org with ESMTP id S1752116AbdA3I0W (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Mon, 30 Jan 2017 03:26:22 -0500
Date: Mon, 30 Jan 2017 09:07:15 +0100
From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= 
        <u.kleine-koenig@pengutronix.de>
To: Thierry Reding <thierry.reding@gmail.com>
Cc: Shailendra Verma <shailendra.v@samsung.com>,
        Laxman Dewangan <ldewangan@nvidia.com>,
        Wolfram Sang <wsa@the-dreams.de>,
        Stephen Warren <swarren@wwwdotorg.org>,
        Alexandre Courbot <gnurou@gmail.com>, linux-i2c@vger.kernel.org,
        linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org,
        p.shailesh@samsung.com, ashish.kalra@samsung.com,
        Shailendra Verma <shailendra.capricorn@gmail.com>
Subject: Re: [PATCH] I2c: busses - Fix possible NULL derefrence.
Message-ID: <20170130080715.wuvx7ro3kuneolnu@pengutronix.de>
References: <CGME20170130050324epcas3p28c9adcffd7bc40e1733cdeef1e5240d5@epcas3p2.samsung.com>
 <1485752587-30107-1-git-send-email-shailendra.v@samsung.com>
 <20170130071217.GG3585@ulmo.ba.sec>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <20170130071217.GG3585@ulmo.ba.sec>
User-Agent: Mutt/1.6.2-neo (2016-06-11)
X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c5
X-SA-Exim-Mail-From: ukl@pengutronix.de
X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false
X-PTX-Original-Recipient: linux-kernel@vger.kernel.org
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hello,

On Mon, Jan 30, 2017 at 08:12:17AM +0100, Thierry Reding wrote:
> On Mon, Jan 30, 2017 at 10:33:07AM +0530, Shailendra Verma wrote:
> > of_device_get_match_data could return NULL, and so can cause
> > a NULL pointer dereference later.
> > 
> > Signed-off-by: Shailendra Verma <shailendra.v@samsung.com>
> > ---
> >  drivers/i2c/busses/i2c-tegra.c |    4 ++++
> >  1 file changed, 4 insertions(+)
> 
> This will never happen. Any match in the OF table that would cause the
> ->probe() to occur has a valid .data pointer associated with it.

Theoretically you could (I think) bind that driver to a node with

	compatible = "tegra-i2c";

Anyhow, even if today there was no possibility this could happen, that's
something that might easily be changed by a future change. So I doubt
"this will never happen" stays true for sure and being defensive is a
good idea. And even a BUG would be better than a silent NULL pointer
dereference.

Just my € 0.02
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |