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 D1510C433F5 for ; Mon, 7 Feb 2022 11:05:07 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id CD72110EF54; Mon, 7 Feb 2022 11:05:06 +0000 (UTC) Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by gabe.freedesktop.org (Postfix) with ESMTPS id 6EFDC10EF54 for ; Mon, 7 Feb 2022 11:05:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1644231905; x=1675767905; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version; bh=vKJ4QcP9fRqWs4tGoyWgQwEyJftVIBFH0F7ZDLnXbgE=; b=KvO/5ZYcimv1zStXQBdZts8b10SNNzIfEfizpiRAh5cwKkOrZDzkbPLw cwa2hBVUi4wB4q5GaA1YHoo8g8xqFi1S3YkMvgokaWts48o7mpgSPzMqh +MIxbdRWveAjszEzulkWU4sjmtIb4xOSFxAqON0OjfM1MXX5XURm25I95 NE8LmXwIUJccYw96vlmFy5qmlKGNOqi6IL5/tzivPcNbaok9NSMiLPu8R TVzgP1HqWsolfAs9xluW8cUBdw1k30Dd9FJcr0cxdsZxrtaHwqTemcsdl tjKI4sSHlgJRFNoVTwRquDEPwLIqWAe2/mhvk9GRAFIEVe92pf69odBD2 w==; X-IronPort-AV: E=McAfee;i="6200,9189,10250"; a="335096447" X-IronPort-AV: E=Sophos;i="5.88,349,1635231600"; d="scan'208";a="335096447" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Feb 2022 03:05:05 -0800 X-IronPort-AV: E=Sophos;i="5.88,349,1635231600"; d="scan'208";a="628486542" Received: from nbaca1-mobl.ger.corp.intel.com (HELO localhost) ([10.252.18.25]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Feb 2022 03:05:00 -0800 From: Jani Nikula To: Kees Cook , Maarten Lankhorst , David Airlie , Daniel Vetter Subject: Re: [PATCH] drm/dp: Remove common Post Cursor2 register handling In-Reply-To: <202202041740.F368F91F5@keescook> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <20220105173507.2420910-1-keescook@chromium.org> <202202041740.F368F91F5@keescook> Date: Mon, 07 Feb 2022 13:04:55 +0200 Message-ID: <87y22nq6nc.fsf@intel.com> 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: , Cc: Thomas Zimmermann , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Jonathan Hunter , Thierry Reding , linux-tegra@vger.kernel.org, linux-hardening@vger.kernel.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Fri, 04 Feb 2022, Kees Cook wrote: > Ping, > > This is a OOB read fix. Can someone please pick this up? Daniel? Thierry? As I said, I reviewed this but I'm not comfortable applying patches that change the functionality of drivers I don't maintain. BR, Jani. > > -Kees > > On Wed, Jan 05, 2022 at 09:35:07AM -0800, Kees Cook wrote: >> The link_status array was not large enough to read the Adjust Request >> Post Cursor2 register, so remove the common helper function to avoid >> an OOB read, found with a -Warray-bounds build: >> >> drivers/gpu/drm/drm_dp_helper.c: In function 'drm_dp_get_adjust_request_post_cursor': >> drivers/gpu/drm/drm_dp_helper.c:59:27: error: array subscript 10 is outside array bounds of 'const u8[6]' {aka 'const unsigned char[6]'} [-Werror=array-bounds] >> 59 | return link_status[r - DP_LANE0_1_STATUS]; >> | ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~ >> drivers/gpu/drm/drm_dp_helper.c:147:51: note: while referencing 'link_status' >> 147 | u8 drm_dp_get_adjust_request_post_cursor(const u8 link_status[DP_LINK_STATUS_SIZE], >> | ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> >> Replace the only user of the helper with an open-coded fetch and decode, >> similar to drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c. >> >> Fixes: 79465e0ffeb9 ("drm/dp: Add helper to get post-cursor adjustments") >> Cc: Maarten Lankhorst >> Cc: Maxime Ripard >> Cc: Thomas Zimmermann >> Cc: David Airlie >> Cc: Daniel Vetter >> Cc: dri-devel@lists.freedesktop.org >> Signed-off-by: Kees Cook >> --- >> This is the alternative to: >> https://lore.kernel.org/lkml/20211203084354.3105253-1-keescook@chromium.org/ >> --- >> drivers/gpu/drm/drm_dp_helper.c | 10 ---------- >> drivers/gpu/drm/tegra/dp.c | 11 ++++++++++- >> include/drm/drm_dp_helper.h | 2 -- >> 3 files changed, 10 insertions(+), 13 deletions(-) >> >> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c >> index 23f9073bc473..c9528aa62c9c 100644 >> --- a/drivers/gpu/drm/drm_dp_helper.c >> +++ b/drivers/gpu/drm/drm_dp_helper.c >> @@ -144,16 +144,6 @@ u8 drm_dp_get_adjust_tx_ffe_preset(const u8 link_status[DP_LINK_STATUS_SIZE], >> } >> EXPORT_SYMBOL(drm_dp_get_adjust_tx_ffe_preset); >> >> -u8 drm_dp_get_adjust_request_post_cursor(const u8 link_status[DP_LINK_STATUS_SIZE], >> - unsigned int lane) >> -{ >> - unsigned int offset = DP_ADJUST_REQUEST_POST_CURSOR2; >> - u8 value = dp_link_status(link_status, offset); >> - >> - return (value >> (lane << 1)) & 0x3; >> -} >> -EXPORT_SYMBOL(drm_dp_get_adjust_request_post_cursor); >> - >> static int __8b10b_clock_recovery_delay_us(const struct drm_dp_aux *aux, u8 rd_interval) >> { >> if (rd_interval > 4) >> diff --git a/drivers/gpu/drm/tegra/dp.c b/drivers/gpu/drm/tegra/dp.c >> index 70dfb7d1dec5..f5535eb04c6b 100644 >> --- a/drivers/gpu/drm/tegra/dp.c >> +++ b/drivers/gpu/drm/tegra/dp.c >> @@ -549,6 +549,15 @@ static void drm_dp_link_get_adjustments(struct drm_dp_link *link, >> { >> struct drm_dp_link_train_set *adjust = &link->train.adjust; >> unsigned int i; >> + u8 post_cursor; >> + int err; >> + >> + err = drm_dp_dpcd_read(link->aux, DP_ADJUST_REQUEST_POST_CURSOR2, >> + &post_cursor, sizeof(post_cursor)); >> + if (err < 0) { >> + DRM_ERROR("failed to read post_cursor2: %d\n", err); >> + post_cursor = 0; >> + } >> >> for (i = 0; i < link->lanes; i++) { >> adjust->voltage_swing[i] = >> @@ -560,7 +569,7 @@ static void drm_dp_link_get_adjustments(struct drm_dp_link *link, >> DP_TRAIN_PRE_EMPHASIS_SHIFT; >> >> adjust->post_cursor[i] = >> - drm_dp_get_adjust_request_post_cursor(status, i); >> + (post_cursor >> (i << 1)) & 0x3; >> } >> } >> >> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h >> index 472dac376284..fdf3cf6ccc02 100644 >> --- a/include/drm/drm_dp_helper.h >> +++ b/include/drm/drm_dp_helper.h >> @@ -1528,8 +1528,6 @@ u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SI >> int lane); >> u8 drm_dp_get_adjust_tx_ffe_preset(const u8 link_status[DP_LINK_STATUS_SIZE], >> int lane); >> -u8 drm_dp_get_adjust_request_post_cursor(const u8 link_status[DP_LINK_STATUS_SIZE], >> - unsigned int lane); >> >> #define DP_BRANCH_OUI_HEADER_SIZE 0xc >> #define DP_RECEIVER_CAP_SIZE 0xf >> -- >> 2.30.2 >> -- Jani Nikula, Intel Open Source Graphics Center