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

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Message-ID: <CAH6sp9PyGqxn6gaes=SPinXmqK5ySLax-3KZ3uu=6Y4_Uc+d5A@mail.gmail.com>
Date:	Thu, 12 Nov 2015 09:36:55 +0100
From:	Frans Klaver <fransklaver@...il.com>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
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 9:26 AM, Uwe Kleine-König
<u.kleine-koenig@...gutronix.de> wrote:
> 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.)

Yea, looks like you're right. platform devices check a number of
things to determine a match, among which is driver name if all else
fails (platform.c, platform_match()).

Thanks,
Frans
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