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=-7.9 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 4A20BC433E1 for ; Tue, 25 Aug 2020 15:09:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2CC202075F for ; Tue, 25 Aug 2020 15:09:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726734AbgHYPI4 (ORCPT ); Tue, 25 Aug 2020 11:08:56 -0400 Received: from mga02.intel.com ([134.134.136.20]:37665 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726191AbgHYPIs (ORCPT ); Tue, 25 Aug 2020 11:08:48 -0400 IronPort-SDR: guzVyx3idWPZHQ5VBZqRCfFTGV/WD2RCbcdrkUFbBahs9vWSyxsXP2agiKOpdascBntNeOd7b6 zSFQNeTnnzEA== X-IronPort-AV: E=McAfee;i="6000,8403,9723"; a="143902232" X-IronPort-AV: E=Sophos;i="5.76,353,1592895600"; d="scan'208";a="143902232" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2020 08:08:47 -0700 IronPort-SDR: KSfTDtD6zIFJ3yrXC9mxYXKt6FSoJ4/pJ7BjhBsF4uQzI1x1YuiipAjh3Izwl0Vjlot+R7UVxg keo6AcrqrJ7g== X-IronPort-AV: E=Sophos;i="5.76,353,1592895600"; d="scan'208";a="322791026" Received: from yyu32-mobl1.amr.corp.intel.com (HELO [10.213.162.112]) ([10.213.162.112]) by fmsmga004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2020 08:08:46 -0700 Subject: Re: [PATCH v11 9/9] x86: Disallow vsyscall emulation when CET is enabled To: Florian Weimer , Andy Lutomirski Cc: X86 ML , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , LKML , "open list:DOCUMENTATION" , Linux-MM , linux-arch , Linux API , Arnd Bergmann , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang References: <20200825002645.3658-1-yu-cheng.yu@intel.com> <20200825002645.3658-10-yu-cheng.yu@intel.com> <87pn7f9jeq.fsf@oldenburg2.str.redhat.com> From: "Yu, Yu-cheng" Message-ID: <0e378792-7ac0-6c52-5607-e73de856d820@intel.com> Date: Tue, 25 Aug 2020 08:08:45 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <87pn7f9jeq.fsf@oldenburg2.str.redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/25/2020 2:14 AM, Florian Weimer wrote: > * Andy Lutomirski: > >> On Mon, Aug 24, 2020 at 5:30 PM Yu-cheng Yu wrote: >>> >>> From: "H.J. Lu" >>> >>> Emulation of the legacy vsyscall page is required by some programs built >>> before 2013. Newer programs after 2013 don't use it. Disallow vsyscall >>> emulation when Control-flow Enforcement (CET) is enabled to enhance >>> security. >> >> NAK. >> >> By all means disable execute emulation if CET-IBT is enabled at the >> time emulation is attempted, and maybe even disable the vsyscall page >> entirely if you can magically tell that CET-IBT will be enabled when a >> process starts, but you don't get to just disable it outright on a >> CET-enabled kernel. > > Yeah, we definitely would have to revert/avoid this downstream. People > definitely want to run glibc-2.12-era workloads on current kernels. > Thanks for catching it. > That makes sense. I will update the patch. Thanks, Yu-cheng