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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id EF1CCC61DA4 for ; Mon, 6 Mar 2023 18:15:30 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 777146B0073; Mon, 6 Mar 2023 13:15:30 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 726DB6B0074; Mon, 6 Mar 2023 13:15:30 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5EDEC6B0075; Mon, 6 Mar 2023 13:15:30 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 4CB426B0073 for ; Mon, 6 Mar 2023 13:15:30 -0500 (EST) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 19134806C5 for ; Mon, 6 Mar 2023 18:15:30 +0000 (UTC) X-FDA: 80539276020.07.C1BAC1A Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf04.hostedemail.com (Postfix) with ESMTP id 2730E40022 for ; Mon, 6 Mar 2023 18:15:27 +0000 (UTC) Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=X7HyX1uf; spf=pass (imf04.hostedemail.com: domain of luto@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=luto@kernel.org; dmarc=pass (policy=none) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1678126528; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=VWZCXqXW654mJFJ+yS/nKvu0uLS+RtZPIEWFah7fdtA=; b=CPeCxsCF58f4Pm8KFCYV6PaP2i7+GAwwFOH0KHufTWVZQC9v7nJnDqULF8XlcH9VDPN7Qh wjiJ6L6jI0I9ERaTWD6WHZF7Nm1yaervOHn4dW7uSUmy/JCcscglbPpsDUDaVhfihSsvc8 /ut7yQ8wcFmahxNJkK82+NoD38LnKkU= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=X7HyX1uf; spf=pass (imf04.hostedemail.com: domain of luto@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=luto@kernel.org; dmarc=pass (policy=none) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1678126528; a=rsa-sha256; cv=none; b=MopZbkyDdP6Afzt0AUhGoCrw6IIfWHPdFKtb6usTqaAi0YuFMSMmNoO6s6c1iCv+u+BRgj Rd8kMjHKdZ2XMPwcGiaYnkJhG/vmxT7sZdaa9FL6Kx9YUTSACSShhsGvNQZF2qANMjLHFA VoCAs81ZS242uBV6BTF2/vnxbPRejlo= Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id E7AC261086 for ; Mon, 6 Mar 2023 18:15:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 46038C433EF for ; Mon, 6 Mar 2023 18:15:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1678126526; bh=e9jsHK3Y3izRmScqj6Tbq8eAsCdvQQ3sYqO3uE9+g1c=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=X7HyX1ufkWoGU//VkDtxJVveZft2IwVqIiE6+D7boTvye2has1qPlXB+ml8GEvUOA SG95FrQa633Rz+KBE+jO82k021+qFZCGkmprtSskcIKsvFlGYsDAtFuQHbM0Lf9nWg BtYhTd1wFXGW3Livr2KSz9TzLcKQz7PJeATt5r1XSo7LtXwxJQU2P0i4kWuDwI2NSo jdky09uU8ZavZ46KebHBCEnp6/ZVf1dzuMKyuXcELHpHQYqs6d227Wj01VjzwEDOz6 jyDm9IRCtkcM2mK0OeawEJWaiU4LssfCyzp2t8X9PdFy2MkWR+hhLpARkP/OnBHZCC QhVZmX/+DrGNQ== Received: by mail-ed1-f41.google.com with SMTP id u9so42503898edd.2 for ; Mon, 06 Mar 2023 10:15:26 -0800 (PST) X-Gm-Message-State: AO0yUKXQU4+MRkCslFhTiGIG3onOS1kTl/f+v5yrGVOJGnwtYPCJCMRY hNPdUNAneUUoOUeVlLEd2vSm/Wc4xQfR5O0rPq9wPw== X-Google-Smtp-Source: AK7set8SLbHFbKu50C45V+XmZcA37AlGVkaEVMQnfhtMxcFSuf0+tBBA5TxTGatK6nCBit+HSX9pGacUV5OMJ4H5Ack= X-Received: by 2002:a50:9318:0:b0:4ad:72b2:cf53 with SMTP id m24-20020a509318000000b004ad72b2cf53mr6481738eda.2.1678126524529; Mon, 06 Mar 2023 10:15:24 -0800 (PST) MIME-Version: 1.0 References: <20230227222957.24501-1-rick.p.edgecombe@intel.com> <20230227222957.24501-25-rick.p.edgecombe@intel.com> In-Reply-To: From: Andy Lutomirski Date: Mon, 6 Mar 2023 10:15:13 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v7 24/41] mm: Don't allow write GUPs to shadow stack memory To: Borislav Petkov Cc: Rick Edgecombe , x86@kernel.org, "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H . J . Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , Weijiang Yang , "Kirill A . Shutemov" , John Allen , kcc@google.com, eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com, dethoma@microsoft.com, akpm@linux-foundation.org, Andrew.Cooper3@citrix.com, christina.schimpe@intel.com, david@redhat.com, debug@rivosinc.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: p6ph41qezyyfgdn3u8msnz5q5y3erfm3 X-Rspamd-Queue-Id: 2730E40022 X-HE-Tag: 1678126527-696413 X-HE-Meta: U2FsdGVkX18xKi42+3LZrA5yevSPK9+9hzOgx/Mi+/91HX+XslXJKNiNKWN7oymKcxl3lBSf2DYXzrxJo8TMHQOOZwxT7GVRNT1zdBAigmPYN+6ik3R7YIKxM1JV4tlV1WlJFsZO+KVc6rsxK+cpecIDUdjOV3ORvn88XdEH66m5qJ29udVAEXcTIDRsMa90zrG4Rvm6TbEyELeqbPDYS4lTThywMDeXCi5NhwwLlY30deF2mGON1a/VgQq16L3+wdtLvuz2lQh9Y45JcpCf9LDTO94CiZObIsbwlGkZjYJEnmCN0dOlMaY+TXRt4+zBCgPVdB2LRxvaA5RPh4eoj3hTd0/jAcSeKKelFDqwvZA+URTEyqO6xvWFfMkfinRWwqeAMbfdPpXwbjmiDJZSSPce7v/hRxND0t0Gd61g+mKCF9vhGVwqu5SzCu1gt8yrNgreXFKWDfscdMeapWJCrX/HDJykJ4HUkJB+Zrcf91mof51IClX7WzRYjn64BJmTQp53EGHTS9AX2OKR0KDCPXS7skO83Xl9n2cF8vzb7Afk/nRYsDUbiQvN0c7B+YbCJimA2IKEAnZlIbG7AfXsp2a4vPrOOEg/IFmXRZ+jvcgSD59JW7fi4OEtrP2oRtSIS0bS0MjiQZ+XWQ9vNH3OB+jp4dLq2iJ1N2E5IX7TVjHfGf3WwWH9a0Ius2VTaEqmDc6Ug1NRNVnsxClYo6cIbnn06YJ0EB/QJ7elVRGwu1iPM9oRLhS0SH94VbzX10yI/XuNKl0Ni8BntimWHrz6VQsPsYwCjJ8jH8haAgS5SxbxQXhBAROEHSBYnX71qK6fsiqJ2e/ftYgppDPahWnL7XoK1xIJfZDWlpUBO+P2NZv05H1JdHtgB4p/XPZLf+LhO8ndd5FMnZ8beT/HYkOLEPt1oCn2XD2x2PKPBt0uT/em1PY1CMm0iSe8l1r4y1sp8HlkrS0j/N/qyHqDH9c r43Xh/xi SLWCBvKivGVIsseX5a6KqqfbPfAAvXTHKEMbxendFFR71I97KTsiFwb3nuYx0TBVwAfbkx53A2TrNrT3kE9wePBpW+c5i85OKjVsl03ylnhrnINj35qvuOfslqKST+d2vV5CIjUbeqn6VAzlkBxmFiIAbApgSrPa5ZGiiZHHm9puCKj2cm7u2cMBqU0SF085YTj981y3xp22dmcQ602hLOs4H77DRLgTWCUl7xZxGCXv1vYVV6oGzTdw98uWQ/iAvK/8FZ8hjVKgylBIoUa3D4uhlPFHh/7ftGiv+2BXcvzLhVu2dqyWIEJqVvEoeie7vpqNQNjIbnC/wvnlbEYsrhdBsc/rYD+wcTCyLTMWKLKyr0ZygxB5jpvK6gaU+9aP9Hb3pWQB9rNMwWYlDBM3tO6fIIg== 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 Mon, Mar 6, 2023 at 5:10=E2=80=AFAM Borislav Petkov wrote= : > > On Mon, Feb 27, 2023 at 02:29:40PM -0800, Rick Edgecombe wrote: > > The x86 Control-flow Enforcement Technology (CET) feature includes a ne= w > > type of memory called shadow stack. This shadow stack memory has some > > unusual properties, which requires some core mm changes to function > > properly. > > > > Shadow stack memory is writable only in very specific, controlled ways. > > However, since it is writable, the kernel treats it as such. As a resul= t > = ^ > = , > > > there remain many ways for userspace to trigger the kernel to write to > > shadow stack's via get_user_pages(, FOLL_WRITE) operations. To make thi= s a Is there an alternate mechanism, or do we still want to allow FOLL_FORCE so that debuggers can write it? --Andy