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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A93E0ECDE45 for ; Mon, 22 Oct 2018 08:06:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 538DA2083A for ; Mon, 22 Oct 2018 08:06:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 538DA2083A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728017AbeJVQXl (ORCPT ); Mon, 22 Oct 2018 12:23:41 -0400 Received: from mga14.intel.com ([192.55.52.115]:44872 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727523AbeJVQXl (ORCPT ); Mon, 22 Oct 2018 12:23:41 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 22 Oct 2018 01:06:12 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,411,1534834800"; d="scan'208";a="274462046" Received: from lahna.fi.intel.com (HELO lahna) ([10.237.72.157]) by fmsmga006.fm.intel.com with SMTP; 22 Oct 2018 01:06:10 -0700 Received: by lahna (sSMTP sendmail emulation); Mon, 22 Oct 2018 11:06:09 +0300 Date: Mon, 22 Oct 2018 11:06:09 +0300 From: Mika Westerberg To: Wenwen Wang Cc: Kangjie Lu , Andreas Noever , Michael Jamet , Yehezkel Bernat , open list Subject: Re: [PATCH] thunderbolt: fix a missing-check bug Message-ID: <20181022080609.GN2302@lahna.fi.intel.com> References: <1540066556-18088-1-git-send-email-wang6495@umn.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1540066556-18088-1-git-send-email-wang6495@umn.edu> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Oct 20, 2018 at 03:15:56PM -0500, Wenwen Wang wrote: > In tb_ring_poll(), the flag of the frame, i.e., > 'ring->descriptors[ring->tail].flags', is checked to see whether the frame > is completed. If yes, the frame including the flag will be read from the > ring and returned to the caller. The problem here is that the flag is > actually in a DMA region, which is allocated through dma_alloc_coherent() > in tb_ring_alloc(). Given that the device can also access this DMA region, > it is possible that a malicious device controlled by an attacker can modify > the flag between the check and the copy. By doing so, the attacker can > bypass the check and supply uncompleted frame, which can cause undefined > behavior of the kernel and introduce potential security risk. > > This patch firstly copies the flag into a local variable 'desc_flags' and > then performs the check and copy using 'desc_flags'. Through this way, the > above issue can be avoided. Same here :)