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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 61F5FC61DA4 for ; Mon, 6 Mar 2023 18:17:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229591AbjCFSRE (ORCPT ); Mon, 6 Mar 2023 13:17:04 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58114 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229843AbjCFSRA (ORCPT ); Mon, 6 Mar 2023 13:17:00 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E8ADC72030 for ; Mon, 6 Mar 2023 10:16:18 -0800 (PST) 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 01FB06106E for ; Mon, 6 Mar 2023 18:15:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 52824C4339B 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-f49.google.com with SMTP id g3so42532641eda.1 for ; Mon, 06 Mar 2023 10:15:26 -0800 (PST) X-Gm-Message-State: AO0yUKUa6zzGxpyfgWZxfXK5obIlDunKHxhAxCLiZLKB1E1EoqFnFYx/ PpHYWN8lWujQ+c81xKqiGgZjcbe+a2i7p3vuocSS3A== 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 Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org 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