From patchwork Tue Dec 12 00:55:26 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Doug Anderson X-Patchwork-Id: 13488268 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 7F8C4C4332F for ; Tue, 12 Dec 2023 00:56:07 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id E015910E091; Tue, 12 Dec 2023 00:56:06 +0000 (UTC) Received: from mail-pf1-x42f.google.com (mail-pf1-x42f.google.com [IPv6:2607:f8b0:4864:20::42f]) by gabe.freedesktop.org (Postfix) with ESMTPS id 24BFB10E091 for ; Tue, 12 Dec 2023 00:56:05 +0000 (UTC) Received: by mail-pf1-x42f.google.com with SMTP id d2e1a72fcca58-6cea0fd9b53so3141204b3a.1 for ; Mon, 11 Dec 2023 16:56:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1702342564; x=1702947364; darn=lists.freedesktop.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=AS84DpIlnHadbg548UoBHWDlxNfb0zaNqIcRTC+jUtI=; b=TfaIj72TJlKAhZdJHH779Sgj+Sc4xQTMnLIM7KxnbsuSe/PD1pWddScQplyVDQdSkz ePSZ7lBrIc8ycyYW56Mkt1gXDjRFHzqXxEvPIdC2GidJaUwtky8TsWyfYDsxJArDb2pO S0cw1PqgF06JUEc02HPT40GiHFpswy5S20aTw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1702342564; x=1702947364; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=AS84DpIlnHadbg548UoBHWDlxNfb0zaNqIcRTC+jUtI=; b=Qonc2geRFrv++NL26BeQk6bGN/D+LxYIWapObB2Elx0c+ADd+h3N/0I+kL2sMs4e1C epH6lYympm1cWx43kTgxPVi6r8cZa7m3PxQXOyeOFn/8D0t6A6G4fyBaOyQsWao1Py8T JeIiU+rf3B0QyGy5AG+B005nDWg80hDbQPuS2p6M/bz1l+xNgO6qI1ZQTdlZPjbQGdMe BIhuU+OrRDt9nHnlgaxdd5xIctDa8dHCG3Lh1Dj5vSpMkTb+bihktIcf3jSsvAVJmLC7 YVtdHXUbpn+x/re/jq0kv6jxKdHd/C+xydHOYN6BPXfR1R5CAiur+J6hgvxeEZxHKIEi yVpg== X-Gm-Message-State: AOJu0Yzvgl8J4wdEBleI8N5NGNew1qP3V4aN7PiLWmvdLb6t6Z6l2Ej4 Br2bo1xke01RZLdvbR3ZniR0V41rqDgF3hH2a5pO1Epf X-Google-Smtp-Source: AGHT+IEImkGOKriQgUmpcCdrkAlZGOVMJy7dWUFL7Mf+hsw6l3dDIoDd8j4PpPAdxvC2/AV5oSW9hg== X-Received: by 2002:a05:6a21:99a4:b0:18c:18d3:c8fd with SMTP id ve36-20020a056a2199a400b0018c18d3c8fdmr3061776pzb.14.1702342563762; Mon, 11 Dec 2023 16:56:03 -0800 (PST) Received: from tictac2.mtv.corp.google.com ([2620:15c:9d:2:5c08:e1ed:d922:d30c]) by smtp.gmail.com with ESMTPSA id k10-20020a170902694a00b001cc311ef152sm7251271plt.286.2023.12.11.16.56.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 Dec 2023 16:56:03 -0800 (PST) From: Douglas Anderson To: dri-devel@lists.freedesktop.org Subject: [PATCH 1/2] drm/bridge: parade-ps8640: Never increase the length when reading from AUX Date: Mon, 11 Dec 2023 16:55:26 -0800 Message-ID: <20231211165526.1.I9d1afcaad76a3e2c0ca046dc4adbc2b632c22eda@changeid> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog MIME-Version: 1.0 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: Maxime Ripard , Neil Armstrong , Philip Chen , Robert Foss , Andrzej Hajda , Thomas Zimmermann , Jonas Karlman , Sam Ravnborg , Douglas Anderson , Jernej Skrabec , Stephen Boyd , Laurent Pinchart , linux-kernel@vger.kernel.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" While testing, I happened to notice a random crash that looked like: Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: drm_dp_dpcd_probe+0x120/0x120 Analysis of drm_dp_dpcd_probe() shows that we pass in a 1-byte buffer (allocated on the stack) to the aux->transfer() function. Presumably if the aux->transfer() writes more than one byte to this buffer then we're in a bad shape. Dropping into kgdb, I noticed that "aux->transfer" pointed at ps8640_aux_transfer(). Reading through ps8640_aux_transfer(), I can see that there are cases where it could write more bytes to msg->buffer than were specified by msg->size. This could happen if the hardware reported back something bogus to us. Let's fix this so we never increase the length. NOTE: I have no actual way to reproduce this issue but it seems likely this is what was happening in the crash I looked at. Fixes: 13afcdd7277e ("drm/bridge: parade-ps8640: Add support for AUX channel") Signed-off-by: Douglas Anderson --- drivers/gpu/drm/bridge/parade-ps8640.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c index 8161b1a1a4b1..fb2ec4264549 100644 --- a/drivers/gpu/drm/bridge/parade-ps8640.c +++ b/drivers/gpu/drm/bridge/parade-ps8640.c @@ -302,7 +302,7 @@ static ssize_t ps8640_aux_transfer_msg(struct drm_dp_aux *aux, fallthrough; case SWAUX_STATUS_ACKM: - len = data & SWAUX_M_MASK; + len = min(len, (unsigned int)(data & SWAUX_M_MASK)); break; case SWAUX_STATUS_DEFER: case SWAUX_STATUS_I2C_DEFER: @@ -310,7 +310,7 @@ static ssize_t ps8640_aux_transfer_msg(struct drm_dp_aux *aux, msg->reply |= DP_AUX_NATIVE_REPLY_DEFER; else msg->reply |= DP_AUX_I2C_REPLY_DEFER; - len = data & SWAUX_M_MASK; + len = min(len, (unsigned int)(data & SWAUX_M_MASK)); break; case SWAUX_STATUS_INVALID: return -EOPNOTSUPP;