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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6D3D0CD4F54 for ; Fri, 29 May 2026 13:29:46 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id AC10B10FF30; Fri, 29 May 2026 13:29:45 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="MwoVQvmw"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.21]) by gabe.freedesktop.org (Postfix) with ESMTPS id 53CCF10FF2F; Fri, 29 May 2026 13:29:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1780061384; x=1811597384; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version; bh=71sOesqiaHj4JhCD+9Hp64zuCWJ5C+w+x7JVSPreLQ8=; b=MwoVQvmwWJkTAmJmULcHbTWiJhCggL1nVS3mjjhjWcGTShepk/9s60Vg BcN5JSPlA8E6diRO0CUn5ISmA33A3q8uuaL05WPbsOvZ1Tbm66MObpx9i NADf/IhgHdfZ7+3w7ThXMk2bKhbqLkfFwm0wPBaXjlTQDDVvKX0rWifch ub1R5a5AT4eoaPbXnuWDRmerCTo9Q2aMU3u3G3iHMMxJaT8urwdEoqgmQ vLhWs+5qZy4iBj7wLoLpgbgqT1G/Qt7PswKhoouAVWRo0pOH1SDacNOsx F1yGvk1brbYdChvlQrf0bXvABW6EoWSiFp9hxGQcU3UTZQAEeB8APDhvw A==; X-CSE-ConnectionGUID: kO2vYPQcQ1CCXGERuXMN8A== X-CSE-MsgGUID: YW+AF//0RAKyFfa+rCcCgQ== X-IronPort-AV: E=McAfee;i="6800,10657,11801"; a="80812827" X-IronPort-AV: E=Sophos;i="6.24,175,1774335600"; d="scan'208";a="80812827" Received: from orviesa002.jf.intel.com ([10.64.159.142]) by orvoesa113.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 May 2026 06:29:44 -0700 X-CSE-ConnectionGUID: mL1xh5hPRmijtE9Oggpl3g== X-CSE-MsgGUID: V4M8DU/5R1GWyj/iv9P7uw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.24,175,1774335600"; d="scan'208";a="273165205" Received: from kniemiec-mobl1.ger.corp.intel.com (HELO localhost) ([10.245.244.147]) by orviesa002-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 May 2026 06:29:41 -0700 From: Jani Nikula To: Nikita Zhandarovich , Rodrigo Vivi , Joonas Lahtinen Cc: Nikita Zhandarovich , Tvrtko Ursulin , David Airlie , Simona Vetter , intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, lvc-project@linuxtesting.org Subject: Re: [PATCH] drm/i915/edp: Check supported link rates DPCD read In-Reply-To: <20260529120921.1633346-1-n.zhandarovich@fintech.ru> Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs Bertel Jungin Aukio 5, 02600 Espoo, Finland References: <20260529120921.1633346-1-n.zhandarovich@fintech.ru> Date: Fri, 29 May 2026 16:29:37 +0300 Message-ID: MIME-Version: 1.0 Content-Type: text/plain X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Fri, 29 May 2026, Nikita Zhandarovich wrote: > intel_edp_set_sink_rates() reads DP_SUPPORTED_LINK_RATES into a local > stack array and then parses the array unconditionally. If the read > fails or returns less data than requested, the array contents are not > valid and may result in bogus sink link rates being used. > > Check that the full DPCD block was read before parsing it. If not, fall > back to the default sink rate handling. > > Found by Linux Verification Center (linuxtesting.org) with static > analysis tool SVACE. Thanks for the patch. > > Fixes: 68f357cb7347 ("drm/i915/dp: generate and cache sink rate array for all DP, not just eDP 1.4") > Signed-off-by: Nikita Zhandarovich > --- > drivers/gpu/drm/i915/display/intel_dp.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c > index 6ef2a0043cda..b6650a12ca54 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp.c > +++ b/drivers/gpu/drm/i915/display/intel_dp.c > @@ -4678,10 +4678,16 @@ intel_edp_set_sink_rates(struct intel_dp *intel_dp) > > if (intel_dp->edp_dpcd[0] >= DP_EDP_14) { > __le16 sink_rates[DP_MAX_SUPPORTED_RATES]; > + ssize_t ret; > int i; > > - drm_dp_dpcd_read(&intel_dp->aux, DP_SUPPORTED_LINK_RATES, > - sink_rates, sizeof(sink_rates)); > + ret = drm_dp_dpcd_read(&intel_dp->aux, DP_SUPPORTED_LINK_RATES, > + sink_rates, sizeof(sink_rates)); Please switch to drm_dp_dpcd_read_data(). It'll return < 0 for errors, and is easier to deal with. > + if (ret != sizeof(sink_rates)) { > + drm_dbg_kms(display->drm, > + "Unable to read eDP supported link rates, using default rates\n"); > + goto use_default_rates; I think I'd avoid the goto and use: memset(sink_rates, 0, sizeof(sink_rates)); BR, Jani. > + } > > for (i = 0; i < ARRAY_SIZE(sink_rates); i++) { > int rate; > @@ -4715,6 +4721,7 @@ intel_edp_set_sink_rates(struct intel_dp *intel_dp) > * Use DP_LINK_RATE_SET if DP_SUPPORTED_LINK_RATES are available, > * default to DP_MAX_LINK_RATE and DP_LINK_BW_SET otherwise. > */ > +use_default_rates: > if (intel_dp->num_sink_rates) > intel_dp->use_rate_select = true; > else -- Jani Nikula, Intel