linux-kernel - Re: [PATCH] mtd: nand: mxc_nand: fix a possible NULL dereference

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Message-ID: <20151112082617.GE24008@pengutronix.de>
Date:	Thu, 12 Nov 2015 09:26:17 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Frans Klaver <fransklaver@...il.com>
Cc:	LABBE Corentin <clabbe.montjoie@...il.com>, baruch@...s.co.il,
	Brian Norris <computersforpeace@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Krzysztof Kozłowski <k.kozlowski.k@...il.com>,
	Luis de Bethencourt <luis@...ethencourt.com>,
	s.hauer@...gutronix.de,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-mtd@...ts.infradead.org
Subject: Re: [PATCH] mtd: nand: mxc_nand: fix a possible NULL dereference

On Thu, Nov 12, 2015 at 09:03:11AM +0100, Frans Klaver wrote:
> Hi,
> 
> On Thu, Nov 12, 2015 at 8:46 AM, LABBE Corentin
> <clabbe.montjoie@...il.com> wrote:
> > of_match_device could return NULL, and so cause a NULL pointer
> > dereference later.
> 
> Did you actually run into this? It seems to me that this driver is
> only probed if and only if we have a match and that therefore
> of_match_device will always return a valid pointer (it is using the
> same match table). Am I missing something?

Yes, you're missing something. The driver would probe for a dt snippet
like:

	mxc_nand {
		compatible = "foobar";
	}

In this case dev->of_node is non-NULL but of_match_device(mxcnd_dt_ids,
dev) is.

(I didn't actually test this, so there is a chance I'm wrong here. And
if not I wonder if it is sensible at all to match the device name on
driver name for of-created platform devices.)

Best regards
Uwe

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