From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E1B59C83F17 for ; Mon, 28 Aug 2023 18:38:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231475AbjH1SiT (ORCPT ); Mon, 28 Aug 2023 14:38:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49536 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233036AbjH1Shv (ORCPT ); Mon, 28 Aug 2023 14:37:51 -0400 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8FFCA1A5 for ; Mon, 28 Aug 2023 11:37:40 -0700 (PDT) Received: from pendragon.ideasonboard.com (117.145-247-81.adsl-dyn.isp.belgacom.be [81.247.145.117]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id D77CB2D8; Mon, 28 Aug 2023 20:36:17 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1693247778; bh=vQIOl5TrRlEiCDa3NnrA7tdFPfjvz0tpmDMx1JbNVeE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=HwFkXUXbuyv2H+/Gua71GCyAGbIKfSHLr9P+aDwm8V9GhNutDxMoX95M66bzhbmVD bIcH5wUcGToby/5RwI+zdSKlRinKotknQpoPPwTJuIKHPt1B7GD/bCfNPUhdWo+AeP o3KQK3/gnYzHqjVstKbfELgBQzd8cqPw9iYpdUJw= Date: Mon, 28 Aug 2023 21:37:48 +0300 From: Laurent Pinchart To: Zhang Shurong Cc: victor.liu@nxp.com, andrzej.hajda@intel.com, neil.armstrong@linaro.org, rfoss@kernel.org, jonas@kwiboo.se, jernej.skrabec@gmail.com, airlied@gmail.com, daniel@ffwll.ch, shawnguo@kernel.org, s.hauer@pengutronix.de, kernel@pengutronix.de, festevam@gmail.com, linux-imx@nxp.com, dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] drm/bridge: imx: fix potential NULL pointer dereference in imx8qxp_ldb_parse_dt_companion() Message-ID: <20230828183748.GK14596@pendragon.ideasonboard.com> References: <20230828172822.GE14596@pendragon.ideasonboard.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 29, 2023 at 02:01:25AM +0800, Zhang Shurong wrote: > 在 2023年8月29日星期二 CST 上午1:28:22，Laurent Pinchart 写道： > > Hi Zhang, > > > > Thank you for the patch. > > > > On Tue, Aug 29, 2023 at 12:55:01AM +0800, Zhang Shurong wrote: > > > of_match_device() may fail and returns a NULL pointer. > > > > How can it return a NULL pointer here ? > > > > > Fix this by checking the return value of of_match_device(). > > > > > > Fixes: 3818715f62b4 ("drm/bridge: imx: Add LDB support for i.MX8qxp") > > > Signed-off-by: Zhang Shurong > > > --- > > > > > > drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c | 2 ++ > > > 1 file changed, 2 insertions(+) > > > > > > diff --git a/drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c > > > b/drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c index > > > 7984da9c0a35..d272f35c8eac 100644 > > > --- a/drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c > > > +++ b/drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c > > > @@ -488,6 +488,8 @@ static int imx8qxp_ldb_parse_dt_companion(struct imx8qxp_ldb *imx8qxp_ldb) > > > * string. > > > */ > > > match = of_match_device(dev->driver->of_match_table, dev); > > > + if (!match) > > > + return -ENODEV; > > > if (!of_device_is_compatible(companion, match->compatible)) { > > > DRM_DEV_ERROR(dev, "companion LDB is incompatible\n"); > > > ret = -ENXIO; > > I think we can make it happen by designing the platform device in a way that > its name aligns with that of the driver. In such a scenario, when the driver > is probed, the of_match_device function will return null. You can verify this > functionality by reviewing the following function: > > static int platform_match(struct device *dev, struct device_driver *drv) This particular device is found in OF-based systems only, and only instantiated through DT. You can create a platform_device manually that may match this driver, but that would be a made-up situation, not something that can happen in practice. -- Regards, Laurent Pinchart