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=-8.8 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=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 EE711C43461 for ; Wed, 9 Sep 2020 23:25:24 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6A08B221E9 for ; Wed, 9 Sep 2020 23:25:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6A08B221E9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 85B358E0001; Wed, 9 Sep 2020 19:25:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 82FFB6B0072; Wed, 9 Sep 2020 19:25:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7464D8E0001; Wed, 9 Sep 2020 19:25:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0170.hostedemail.com [216.40.44.170]) by kanga.kvack.org (Postfix) with ESMTP id 5F0916B0002 for ; Wed, 9 Sep 2020 19:25:23 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 2C2621EFD for ; Wed, 9 Sep 2020 23:25:23 +0000 (UTC) X-FDA: 77245106526.27.end69_0a0d52c270e1 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin27.hostedemail.com (Postfix) with ESMTP id 02B863D669 for ; Wed, 9 Sep 2020 23:25:22 +0000 (UTC) X-HE-Tag: end69_0a0d52c270e1 X-Filterd-Recvd-Size: 4513 Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by imf08.hostedemail.com (Postfix) with ESMTP for ; Wed, 9 Sep 2020 23:25:21 +0000 (UTC) IronPort-SDR: qUOkgVCjZpveo16RLvKKOF1wk+mTrQv6CNFC55K7xwAGNr4gRBrirqYjUcb/gP6dM+f1SNCAnp Sq8Ib85XI1Ew== X-IronPort-AV: E=McAfee;i="6000,8403,9739"; a="157718006" X-IronPort-AV: E=Sophos;i="5.76,410,1592895600"; d="scan'208";a="157718006" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Sep 2020 16:25:20 -0700 IronPort-SDR: 97ngTUD1zf87z1J3aBsa0H7mLbs6F9XUx1PagpQMhF0Zgnk57KKBy1hAnm4cgbBt1RMBPolWPy 18nZ0L9a9LoQ== X-IronPort-AV: E=Sophos;i="5.76,410,1592895600"; d="scan'208";a="329101836" Received: from yyu32-mobl1.amr.corp.intel.com (HELO [10.212.243.130]) ([10.212.243.130]) by fmsmga004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Sep 2020 16:25:18 -0700 Subject: Re: [PATCH v11 25/25] x86/cet/shstk: Add arch_prctl functions for shadow stack To: Dave Hansen , Andy Lutomirski Cc: Dave Martin , "H.J. Lu" , Florian Weimer , 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 , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Weijiang Yang References: <086c73d8-9b06-f074-e315-9964eb666db9@intel.com> <20200826164604.GW6642@arm.com> <87ft892vvf.fsf@oldenburg2.str.redhat.com> <0e9996bc-4c1b-cc99-9616-c721b546f857@intel.com> <4f2dfefc-b55e-bf73-f254-7d95f9c67e5c@intel.com> <20200901102758.GY6642@arm.com> <32005d57-e51a-7c7f-4e86-612c2ff067f3@intel.com> <46dffdfd-92f8-0f05-6164-945f217b0958@intel.com> <6e1e22a5-1b7f-2783-351e-c8ed2d4893b8@intel.com> <5979c58d-a6e3-d14d-df92-72cdeb97298d@intel.com> <08c91835-8486-9da5-a7d1-75e716fc5d36@intel.com> From: "Yu, Yu-cheng" Message-ID: Date: Wed, 9 Sep 2020 16:25:16 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Rspamd-Queue-Id: 02B863D669 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 9/9/2020 4:11 PM, Dave Hansen wrote: > On 9/9/20 4:07 PM, Yu, Yu-cheng wrote: >> What if a writable mapping is passed to madvise(MADV_SHSTK)?=C2=A0 Sho= uld >> that be rejected? >=20 > It doesn't matter to me. Even if it's readable, it _stops_ being even > directly readable after it's a shadow stack, right? I don't think > writes are special in any way. If anything, we *want* it to be writabl= e > because that indicates that it can be written to, and we will want to > write to it soon. >=20 But in a PROT_WRITE mapping, all the pte's have _PAGE_BIT_RW set. To=20 change them to shadow stack, we need to clear that bit from the pte's. That will be like mprotect_fixup()/change_protection_range().