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 23F71C4332F for ; Thu, 14 Apr 2022 08:32:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240956AbiDNIe7 (ORCPT ); Thu, 14 Apr 2022 04:34:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41428 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237689AbiDNIe5 (ORCPT ); Thu, 14 Apr 2022 04:34:57 -0400 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4B00363391; Thu, 14 Apr 2022 01:32:33 -0700 (PDT) Received: from [192.168.1.111] (91-156-85-209.elisa-laajakaista.fi [91.156.85.209]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 99A1125B; Thu, 14 Apr 2022 10:32:30 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1649925151; bh=f95sAmWwdjHUVI8Avcc4pPnkl/AY78Md6cw7xBbSuOw=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=vHnKDAOozWKdm9KwKMINztx80dsZqkPD9YUHKngyWssNiBI1T7OkTyynBzZIozuIT l4Dn2O+eAWi5OB2z6Bd+IZcRoMfcU8Ab0DQsirXjNwgvIp8JlCGz5a60gr+3jCNSLe Fr+VPChZjLnp7FfaxMIiJIyxyvUlmW+d3DM5vJKg= Message-ID: Date: Thu, 14 Apr 2022 11:32:27 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [RESEND][PATCH] omapdrm: fix missing check on list iterator Content-Language: en-US To: Xiaomeng Tong , airlied@linux.ie, daniel@ffwll.ch Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20220414061410.7678-1-xiam0nd.tong@gmail.com> From: Tomi Valkeinen In-Reply-To: <20220414061410.7678-1-xiam0nd.tong@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 14/04/2022 09:14, Xiaomeng Tong wrote: > The bug is here: > bus_flags = connector->display_info.bus_flags; > > The list iterator 'connector-' will point to a bogus position containing > HEAD if the list is empty or no element is found. This case must > be checked before any use of the iterator, otherwise it will lead > to a invalid memory access. > > To fix this bug, add an check. Use a new value 'iter' as the list > iterator, while use the old value 'connector' as a dedicated variable > to point to the found element. > > Cc: stable@vger.kernel.org > Fixes: ("drm/omap: Add support for drm_panel") > Signed-off-by: Xiaomeng Tong > --- > drivers/gpu/drm/omapdrm/omap_encoder.c | 14 +++++++++----- > 1 file changed, 9 insertions(+), 5 deletions(-) > > diff --git a/drivers/gpu/drm/omapdrm/omap_encoder.c b/drivers/gpu/drm/omapdrm/omap_encoder.c > index 4dd05bc732da..d648ab4223b1 100644 > --- a/drivers/gpu/drm/omapdrm/omap_encoder.c > +++ b/drivers/gpu/drm/omapdrm/omap_encoder.c > @@ -76,14 +76,16 @@ static void omap_encoder_mode_set(struct drm_encoder *encoder, > struct omap_encoder *omap_encoder = to_omap_encoder(encoder); > struct omap_dss_device *output = omap_encoder->output; > struct drm_device *dev = encoder->dev; > - struct drm_connector *connector; > + struct drm_connector *connector = NULL, *iter; > struct drm_bridge *bridge; > struct videomode vm = { 0 }; > u32 bus_flags; > > - list_for_each_entry(connector, &dev->mode_config.connector_list, head) { > - if (connector->encoder == encoder) > + list_for_each_entry(iter, &dev->mode_config.connector_list, head) { > + if (iter->encoder == encoder) { > + connector = iter; > break; > + } > } When does this bug happen? How do you get omap_encoder_mode_set() called for an encoder with a connector that is not valid? > > drm_display_mode_to_videomode(adjusted_mode, &vm); > @@ -106,8 +108,10 @@ static void omap_encoder_mode_set(struct drm_encoder *encoder, > omap_encoder_update_videomode_flags(&vm, bus_flags); > } > > - bus_flags = connector->display_info.bus_flags; > - omap_encoder_update_videomode_flags(&vm, bus_flags); > + if (connector) { > + bus_flags = connector->display_info.bus_flags; > + omap_encoder_update_videomode_flags(&vm, bus_flags); > + } > > /* Set timings for all devices in the display pipeline. */ > dss_mgr_set_timings(output, &vm); How does this fix the issue? You just skip the lines that set up the videomode, but then pass that videomode to dss_mgr_set_timings()... Tomi