linux-kernel - Re: [PATCH] I2c: busses - Fix possible NULL derefrence.

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Date:   Mon, 30 Jan 2017 09:07:15 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Shailendra Verma <shailendra.v@...sung.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        Stephen Warren <swarren@...dotorg.org>,
        Alexandre Courbot <gnurou@...il.com>,
        linux-i2c@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org, p.shailesh@...sung.com,
        ashish.kalra@...sung.com,
        Shailendra Verma <shailendra.capricorn@...il.com>
Subject: Re: [PATCH] I2c: busses - Fix possible NULL derefrence.

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@...sung.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/  |