Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753975AbbKLJCH (ORCPT ); Thu, 12 Nov 2015 04:02:07 -0500 Received: from metis.ext.4.pengutronix.de ([92.198.50.35]:33438 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753788AbbKLJCE (ORCPT ); Thu, 12 Nov 2015 04:02:04 -0500 Date: Thu, 12 Nov 2015 10:01:54 +0100 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Frans Klaver Cc: LABBE Corentin , baruch@tkos.co.il, Brian Norris , David Woodhouse , Krzysztof =?utf-8?Q?Koz=C5=82owski?= , Luis de Bethencourt , kernel@pengutronix.de, "linux-kernel@vger.kernel.org" , Greg Kroah-Hartman , devicetree@vger.kernel.org Subject: Re: [PATCH] mtd: nand: mxc_nand: fix a possible NULL dereference Message-ID: <20151112090154.GG24008@pengutronix.de> References: <1447314423-31225-1-git-send-email-clabbe.montjoie@gmail.com> <20151112082617.GE24008@pengutronix.de> <20151112085312.GF24008@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c0 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: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3220 Lines: 79 On Thu, Nov 12, 2015 at 09:57:07AM +0100, Frans Klaver wrote: > On Thu, Nov 12, 2015 at 9:53 AM, Uwe Kleine-K?nig > wrote: > > CC += devicetree@vger.kernel.org, gregkh > > You added linux@pengutronix instead of devicetree. Well I substituted Sascha by kernel@pengutronix.de on purpose, but considered that too unimportant for the outer world :-) But I really forgot devicetree@vger.kernel.org. Added now. > > On Thu, Nov 12, 2015 at 09:36:55AM +0100, Frans Klaver wrote: > >> On Thu, Nov 12, 2015 at 9:26 AM, Uwe Kleine-K?nig > >> 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 > >> >> 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()). > > > > Maybe something like this would help to reduce surprises: > > > > diff --git a/drivers/base/platform.c b/drivers/base/platform.c > > index f80aaaf9f610..a9fc22c86552 100644 > > --- a/drivers/base/platform.c > > +++ b/drivers/base/platform.c > > @@ -840,8 +840,8 @@ static int platform_match(struct device *dev, struct device_driver *drv) > > return !strcmp(pdev->driver_override, drv->name); > > > > /* Attempt an OF style match first */ > > - if (of_driver_match_device(dev, drv)) > > - return 1; > > + if (pdev->dev.of_node) > > + return of_driver_match_device(dev, drv); > > > > /* Then try ACPI style match */ > > if (acpi_driver_match_device(dev, drv)) > > That looks sensible, yea. There is a chance that misbehaving DT nodes > will fail after this change, of course. Which is ok if this behaviour is considered a misbehave :-) Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-K?nig | Industrial Linux Solutions | http://www.pengutronix.de/ | -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/