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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 BC05B13F6DFF for ; Mon, 30 Jul 2018 09:55:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 705D520873 for ; Mon, 30 Jul 2018 09:55:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 705D520873 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=daenzer.net 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 S1726904AbeG3L30 (ORCPT ); Mon, 30 Jul 2018 07:29:26 -0400 Received: from mail.netline.ch ([148.251.143.178]:43150 "EHLO netline-mail3.netline.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726709AbeG3L3Z (ORCPT ); Mon, 30 Jul 2018 07:29:25 -0400 Received: from localhost (localhost [127.0.0.1]) by netline-mail3.netline.ch (Postfix) with ESMTP id E42E72A6046; Mon, 30 Jul 2018 11:55:10 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at netline-mail3.netline.ch Received: from netline-mail3.netline.ch ([127.0.0.1]) by localhost (netline-mail3.netline.ch [127.0.0.1]) (amavisd-new, port 10024) with LMTP id 9E6PKxpdDu70; Mon, 30 Jul 2018 11:55:10 +0200 (CEST) Received: from thor (67.124.127.176.dynamic.wline.res.cust.swisscom.ch [176.127.124.67]) by netline-mail3.netline.ch (Postfix) with ESMTPSA id 1E7C02A6045; Mon, 30 Jul 2018 11:55:09 +0200 (CEST) Received: from localhost ([::1]) by thor with esmtp (Exim 4.91) (envelope-from ) id 1fk4tQ-0004fr-RT; Mon, 30 Jul 2018 11:55:08 +0200 Subject: Re: [PATCH] drm/amdgpu/pm: Fix potential Spectre v1 To: Alex Deucher , "Gustavo A. R. Silva" Cc: "David (ChunMing) Zhou" , David Airlie , LKML , amd-gfx list , Maling list - DRI developers , Alex Deucher , =?UTF-8?Q?Christian_K=c3=b6nig?= References: <20180723163232.GA17358@embeddedor.com> From: =?UTF-8?Q?Michel_D=c3=a4nzer?= Openpgp: preference=signencrypt Autocrypt: addr=michel@daenzer.net; prefer-encrypt=mutual; keydata= mQGiBDsehS8RBACbsIQEX31aYSIuEKxEnEX82ezMR8z3LG8ktv1KjyNErUX9Pt7AUC7W3W0b LUhu8Le8S2va6hi7GfSAifl0ih3k6Bv1Itzgnd+7ZmSrvCN8yGJaHNQfAevAuEboIb+MaVHo 9EMJj4ikOcRZCmQWw7evu/D9uQdtkCnRY9iJiAGxbwCguBHtpoGMxDOINCr5UU6qt+m4O+UD /355ohBBzzyh49lTj0kTFKr0Ozd20G2FbcqHgfFL1dc1MPyigej2gLga2osu2QY0ObvAGkOu WBi3LTY8Zs8uqFGDC4ZAwMPoFy3yzu3ne6T7d/68rJil0QcdQjzzHi6ekqHuhst4a+/+D23h Za8MJBEcdOhRhsaDVGAJSFEQB1qLBACOs0xN+XblejO35gsDSVVk8s+FUUw3TSWJBfZa3Imp V2U2tBO4qck+wqbHNfdnU/crrsHahjzBjvk8Up7VoY8oT+z03sal2vXEonS279xN2B92Tttr AgwosujguFO/7tvzymWC76rDEwue8TsADE11ErjwaBTs8ZXfnN/uAANgPLQjTWljaGVsIERh ZW56ZXIgPG1pY2hlbEBkYWVuemVyLm5ldD6IXgQTEQIAHgUCQFXxJgIbAwYLCQgHAwIDFQID AxYCAQIeAQIXgAAKCRBaga+OatuyAIrPAJ9ykonXI3oQcX83N2qzCEStLNW47gCeLWm/QiPY jqtGUnnSbyuTQfIySkK5AQ0EOx6FRRAEAJZkcvklPwJCgNiw37p0GShKmFGGqf/a3xZZEpjI qNxzshFRFneZze4f5LhzbX1/vIm5+ZXsEWympJfZzyCmYPw86QcFxyZflkAxHx9LeD+89Elx bw6wT0CcLvSv8ROfU1m8YhGbV6g2zWyLD0/naQGVb8e4FhVKGNY2EEbHgFBrAAMGA/0VktFO CxFBdzLQ17RCTwCJ3xpyP4qsLJH0yCoA26rH2zE2RzByhrTFTYZzbFEid3ddGiHOBEL+bO+2 GNtfiYKmbTkj1tMZJ8L6huKONaVrASFzLvZa2dlc2zja9ZSksKmge5BOTKWgbyepEc5qxSju YsYrX5xfLgTZC5abhhztpYhGBBgRAgAGBQI7HoVFAAoJEFqBr45q27IAlscAn2Ufk2d6/3p4 Cuyz/NX7KpL2dQ8WAJ9UD5JEakhfofed8PSqOM7jOO3LCA== Message-ID: <50f9f4f3-76e1-401a-bd84-6ae746fe4647@daenzer.net> Date: Mon, 30 Jul 2018 11:55:08 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-CA Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018-07-24 10:53 PM, Alex Deucher wrote: > On Mon, Jul 23, 2018 at 12:32 PM, Gustavo A. R. Silva > wrote: >> idx can be indirectly controlled by user-space, hence leading to a >> potential exploitation of the Spectre variant 1 vulnerability. >> >> This issue was detected with the help of Smatch: >> >> drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c:408 amdgpu_set_pp_force_state() >> warn: potential spectre issue 'data.states' >> >> Fix this by sanitizing idx before using it to index data.states > > Is this actually necessary? We already check that idx is valid a few > lines before: > if (ret || idx >= ARRAY_SIZE(data.states)) { > count = -EINVAL; > goto fail; > } A Spectre attack would be based on idx ending up too large, but the CPU speculatively executing the following code assuming idx < ARRAY_SIZE(data.states), and extracting information from the incorrectly speculated code via side channels. I'm not sure if that's actually possible in this case, but better safe than sorry? -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer