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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 96E49C3279B for ; Wed, 4 Jul 2018 07:38:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 59CF42445F for ; Wed, 4 Jul 2018 07:38:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 59CF42445F 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 S933779AbeGDHi1 (ORCPT ); Wed, 4 Jul 2018 03:38:27 -0400 Received: from mail.netline.ch ([148.251.143.178]:60295 "EHLO netline-mail3.netline.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932467AbeGDHiY (ORCPT ); Wed, 4 Jul 2018 03:38:24 -0400 Received: from localhost (localhost [127.0.0.1]) by netline-mail3.netline.ch (Postfix) with ESMTP id 268CC2A6048; Wed, 4 Jul 2018 09:38:22 +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 bfjoqku6RWhm; Wed, 4 Jul 2018 09:38:21 +0200 (CEST) Received: from thor (252.228.127.176.dynamic.wline.res.cust.swisscom.ch [176.127.228.252]) by netline-mail3.netline.ch (Postfix) with ESMTPSA id 464AA2A6045; Wed, 4 Jul 2018 09:38:21 +0200 (CEST) Received: from localhost ([::1]) by thor with esmtp (Exim 4.91) (envelope-from ) id 1facMm-0004QL-L8; Wed, 04 Jul 2018 09:38:20 +0200 Subject: Re: [PATCH] drm/amd/display/dc/dce: Fix multiple potential integer overflows To: "Gustavo A. R. Silva" , Alex Deucher , =?UTF-8?Q?Christian_K=c3=b6nig?= , "David (ChunMing) Zhou" , David Airlie Cc: dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20180704011305.GA15742@embeddedor.com> From: =?UTF-8?Q?Michel_D=c3=a4nzer?= Openpgp: preference=signencrypt Autocrypt: addr=michel@daenzer.net; prefer-encrypt=mutual; keydata= xsDiBDsehS8RBACbsIQEX31aYSIuEKxEnEX82ezMR8z3LG8ktv1KjyNErUX9Pt7AUC7W3W0b LUhu8Le8S2va6hi7GfSAifl0ih3k6Bv1Itzgnd+7ZmSrvCN8yGJaHNQfAevAuEboIb+MaVHo 9EMJj4ikOcRZCmQWw7evu/D9uQdtkCnRY9iJiAGxbwCguBHtpoGMxDOINCr5UU6qt+m4O+UD /355ohBBzzyh49lTj0kTFKr0Ozd20G2FbcqHgfFL1dc1MPyigej2gLga2osu2QY0ObvAGkOu WBi3LTY8Zs8uqFGDC4ZAwMPoFy3yzu3ne6T7d/68rJil0QcdQjzzHi6ekqHuhst4a+/+D23h Za8MJBEcdOhRhsaDVGAJSFEQB1qLBACOs0xN+XblejO35gsDSVVk8s+FUUw3TSWJBfZa3Imp V2U2tBO4qck+wqbHNfdnU/crrsHahjzBjvk8Up7VoY8oT+z03sal2vXEonS279xN2B92Tttr AgwosujguFO/7tvzymWC76rDEwue8TsADE11ErjwaBTs8ZXfnN/uAANgPM0jTWljaGVsIERh ZW56ZXIgPG1pY2hlbEBkYWVuemVyLm5ldD7CXgQTEQIAHgUCQFXxJgIbAwYLCQgHAwIDFQID AxYCAQIeAQIXgAAKCRBaga+OatuyAIrPAJ9ykonXI3oQcX83N2qzCEStLNW47gCeLWm/QiPY jqtGUnnSbyuTQfIySkLOwE0EOx6FRRAEAJZkcvklPwJCgNiw37p0GShKmFGGqf/a3xZZEpjI qNxzshFRFneZze4f5LhzbX1/vIm5+ZXsEWympJfZzyCmYPw86QcFxyZflkAxHx9LeD+89Elx bw6wT0CcLvSv8ROfU1m8YhGbV6g2zWyLD0/naQGVb8e4FhVKGNY2EEbHgFBrAAMGA/0VktFO CxFBdzLQ17RCTwCJ3xpyP4qsLJH0yCoA26rH2zE2RzByhrTFTYZzbFEid3ddGiHOBEL+bO+2 GNtfiYKmbTkj1tMZJ8L6huKONaVrASFzLvZa2dlc2zja9ZSksKmge5BOTKWgbyepEc5qxSju YsYrX5xfLgTZC5abhhztpcJGBBgRAgAGBQI7HoVFAAoJEFqBr45q27IAlscAn2Ufk2d6/3p4 Cuyz/NX7KpL2dQ8WAJ9UD5JEakhfofed8PSqOM7jOO3LCA== Message-ID: Date: Wed, 4 Jul 2018 09:38:19 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180704011305.GA15742@embeddedor.com> 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 2018-07-04 03:13 AM, Gustavo A. R. Silva wrote: > Add suffix ULL to constant 5 and cast variables target_pix_clk_khz and > feedback_divider to uint64_t in order to avoid multiple potential integer > overflows and give the compiler complete information about the proper > arithmetic to use. > > Notice that such constant and variables are used in contexts that > expect expressions of type uint64_t (64 bits, unsigned). The current > casts to uint64_t effectively apply to each expression as a whole, > but they do not prevent them from being evaluated using 32-bit > arithmetic instead of 64-bit arithmetic. > > Also, once the expressions are properly evaluated using 64-bit > arithmentic, there is no need for the parentheses that enclose > them. > > Addresses-Coverity-ID: 1460245 ("Unintentional integer overflow") > Addresses-Coverity-ID: 1460286 ("Unintentional integer overflow") > Addresses-Coverity-ID: 1460401 ("Unintentional integer overflow") > Fixes: 4562236b3bc0 ("drm/amd/dc: Add dc display driver (v2)") > Signed-off-by: Gustavo A. R. Silva > > [...] > > @@ -145,8 +145,8 @@ static bool calculate_fb_and_fractional_fb_divider( > * of fractional feedback decimal point and the fractional FB Divider precision > * is 2 then the equation becomes (ullfeedbackDivider + 5*100) / (10*100))*/ > > - feedback_divider += (uint64_t) > - (5 * calc_pll_cs->fract_fb_divider_precision_factor); > + feedback_divider += 5UL * > + calc_pll_cs->fract_fb_divider_precision_factor; This should be 5ULL, as the commit log says, otherwise it's still only 32 bits on 32-bit platforms. -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer