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 5707CC43461 for ; Wed, 9 Sep 2020 23:07:15 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 06F3221D95 for ; Wed, 9 Sep 2020 23:07:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 06F3221D95 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 3A6196B0055; Wed, 9 Sep 2020 19:07:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 355556B005A; Wed, 9 Sep 2020 19:07:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 243E36B0062; Wed, 9 Sep 2020 19:07:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0086.hostedemail.com [216.40.44.86]) by kanga.kvack.org (Postfix) with ESMTP id 0E6C76B0055 for ; Wed, 9 Sep 2020 19:07:13 -0400 (EDT) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id B8036180AD806 for ; Wed, 9 Sep 2020 23:07:12 +0000 (UTC) X-FDA: 77245060704.06.sofa45_5b16b0b270e1 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin06.hostedemail.com (Postfix) with ESMTP id 826A2100A09C1 for ; Wed, 9 Sep 2020 23:07:12 +0000 (UTC) X-HE-Tag: sofa45_5b16b0b270e1 X-Filterd-Recvd-Size: 4812 Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by imf15.hostedemail.com (Postfix) with ESMTP for ; Wed, 9 Sep 2020 23:07:11 +0000 (UTC) IronPort-SDR: ov8oDDRmbMA6CvBFftPefce6j40cYKoFCx6iXP18vvf5JniYnCujXxozHftpMXMHW/VtN8TCKJ qbEuNAyz3YdA== X-IronPort-AV: E=McAfee;i="6000,8403,9739"; a="155895070" X-IronPort-AV: E=Sophos;i="5.76,410,1592895600"; d="scan'208";a="155895070" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Sep 2020 16:07:10 -0700 IronPort-SDR: qkfpSoKV1QeBLR8tjA8HAJxMsc61Q3klbLaexWsYoj4/2+poJ8zDHk1wXd4u6VEzMkKvkZoTVx KbyeR31mj0lQ== X-IronPort-AV: E=Sophos;i="5.76,410,1592895600"; d="scan'208";a="300309339" Received: from yyu32-mobl1.amr.corp.intel.com (HELO [10.212.243.130]) ([10.212.243.130]) by orsmga003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Sep 2020 16:07:08 -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> <73c2211f-8811-2d9f-1930-1c5035e6129c@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> From: "Yu, Yu-cheng" Message-ID: <08c91835-8486-9da5-a7d1-75e716fc5d36@intel.com> Date: Wed, 9 Sep 2020 16:07:07 -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: 826A2100A09C1 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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 3:59 PM, Dave Hansen wrote: > On 9/9/20 3:08 PM, Yu, Yu-cheng wrote: >> After looking at this more, I found the changes are more similar to >> mprotect() than madvise().=C2=A0 We are going to change an anonymous m= apping >> to a read-only mapping, and add the VM_SHSTK flag to it.=C2=A0 Would a= n >> x86-specific mprotect(PROT_SHSTK) make more sense? >> >> One alternative would be requiring a read-only mapping for >> madvise(MADV_SHSTK).=C2=A0 But that is inconvenient for the applicatio= n. >=20 > Why? It's just: >=20 > mmap()/malloc(); > mprotect(PROT_READ); > madvise(MADV_SHSTK); >=20 > vs. >=20 > mmap()/malloc(); > mprotect(PROT_SHSTK); >=20 > I'm not sure a single syscall counts as inconvenient. >=20 > I don't quite think we should use a PROT_ bit for this. It seems like > the kind of thing that could be fragile and break existing expectations= . > I don't care _that_ strongly though. >=20 What if a writable mapping is passed to madvise(MADV_SHSTK)? Should=20 that be rejected?