linux-kernel - Re: [PATCH] i2c: rcar: fix a possible NULL dereference

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Message-ID: <20151112090307.GH24008@pengutronix.de>
Date:	Thu, 12 Nov 2015 10:03:07 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Wolfram Sang <wsa@...-dreams.de>
Cc:	LABBE Corentin <clabbe.montjoie@...il.com>,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: rcar: fix a possible NULL dereference

On Thu, Nov 12, 2015 at 09:48:37AM +0100, Wolfram Sang wrote:
> On Thu, Nov 12, 2015 at 09:09:26AM +0100, Uwe Kleine-König wrote:
> > Hello Wolfram,
> > 
> > On Thu, Nov 12, 2015 at 08:52:38AM +0100, Wolfram Sang wrote:
> > > On Thu, Nov 12, 2015 at 08:44:47AM +0100, Uwe Kleine-König wrote:
> > > > Other than that, the NULL pointer dereference should only happen if the
> > > > device was bound using the driver name. That might be worth to point out
> > > > in the commit log. So maybe make (in a separate patch) the probe
> > > > function fail when probed by name?
> > > 
> > > RCar is a DT only platform.
> > 
> > Does this imply that no checking is needed? I'm not sure.
> 
> I don't see how this driver could get probed otherwise. That being said,
> for the "better safe than sorry" approach, I'd accept your suggestion.

Try adding the following to a device tree:

	i2c-rcar {

	}

This creates a platform device with name=i2c-rcar which makes
platform_match() yield a match for your driver.

(The other alternative is a device with this name created by a platform
file (even if this is not an rcar machine) doesn't trigger that problem
here I think, because there is a platform_device_id with a matching
name).

See also 

	http://article.gmane.org/gmane.linux.kernel/2083641

for a similar discussion.

Best regards
Uwe

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