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 86755C433FE for ; Fri, 30 Sep 2022 23:03:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232192AbiI3XDG (ORCPT ); Fri, 30 Sep 2022 19:03:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60218 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229548AbiI3XDD (ORCPT ); Fri, 30 Sep 2022 19:03:03 -0400 Received: from mail-io1-xd34.google.com (mail-io1-xd34.google.com [IPv6:2607:f8b0:4864:20::d34]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 18B6F1D7BD3 for ; Fri, 30 Sep 2022 16:03:02 -0700 (PDT) Received: by mail-io1-xd34.google.com with SMTP id q83so4393208iod.7 for ; Fri, 30 Sep 2022 16:03:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date; bh=SqBsvh6C88KVHki7t4Nj5RWCZOuW9N4jEM2i1kXUX1A=; b=QV19rN7u49LBgxsERfExNXC4Qifjr+PujO83hWUsqQwWJAXOvZDMqMjRVEDwq/nUYr 8y2bG+TTsCRkpKYIxMWp8TqRP9q0NhNbhHKapcl7ZvaDlrJTayOSthJN8uY5l9d557x9 i/hEw2f9ra0wkORLPbcYwdezMlEVBHVdwUCkjEiJh7tiOGHh48T0sJ9EquqQ1m5DhnQ8 1ycYF/JTKxFOBImu3XQsT+D0d2yQO0F6wmMGdzGRtRwL5UBCP7gM0lmrYUwAPIWwx3t0 Yr8+kmTHepP1iIeY3YZxS+B1BGhJde4gU45irp5VKxeWy7uNtfVblAI+gIl/XxNQRTov W/xg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date; bh=SqBsvh6C88KVHki7t4Nj5RWCZOuW9N4jEM2i1kXUX1A=; b=Y8NGgFOIdOxAb4/O2ddY4LfWYJRyfnVB8z1fYcxkTdaB/QGXfoJzvqyXNDdCAvjPzl gc5nhVwTrGQVnpr0ssNrx+Gn8qTdu3skhyM5yrIkyRMLU+DjXPJ/aoG8sE1QxLnY50qg 9ZnAu5cTuref0241+20ekEHY6JKOOvMbyrCR08lAtv5QRaONiHPbmrlPtuwisVEo28ZN JK+9uHe/gJXTmoKXJCYQROJimoU4cG75VFd5ipbebXhj1EO6T6Wkjr7AEQ9HqbxrG0Uk qv/mAmOj+7WmSzbN9SO8ibu/Wtpm6JJyR005dqN79jVQWu0yJTm+Zd4oskh+ktgr38a6 igCA== X-Gm-Message-State: ACrzQf0hYo5KqA67w6oZFZAMH1Cu3ZOLvDM0jj7cW+jCUhlxC7s49WHw lnNIMmjZujHznO/HB4yzhNZLLEXuN9NUdxdwzyWXzA== X-Google-Smtp-Source: AMsMyM6/1Zo86oY4qRLob+fDqU88N1JO4RXTZoZZODrBjD9wJqjFTLtKUMBKFRj4TR8qKrKyDwQEelk6KAJ1qvm8qrk= X-Received: by 2002:a6b:5d02:0:b0:6a3:46d5:a08d with SMTP id r2-20020a6b5d02000000b006a346d5a08dmr4696832iob.2.1664578981372; Fri, 30 Sep 2022 16:03:01 -0700 (PDT) MIME-Version: 1.0 References: <20220929222936.14584-1-rick.p.edgecombe@intel.com> <20220929222936.14584-23-rick.p.edgecombe@intel.com> <9fed0342-2d02-aaf2-ed66-20ff08bdfd0b@intel.com> In-Reply-To: From: Jann Horn Date: Sat, 1 Oct 2022 01:02:25 +0200 Message-ID: Subject: Re: [PATCH v2 22/39] mm: Don't allow write GUPs to shadow stack memory To: Dave Hansen 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 , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H . J . Lu" , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V . Shankar" , Weijiang Yang , "Kirill A . Shutemov" , joao.moreira@intel.com, John Allen , kcc@google.com, eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com, dethoma@microsoft.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Oct 1, 2022 at 1:00 AM Jann Horn wrote: > So I think this change is actually a no-op - the only thing it does is > to return 0 if write==1, !_PAGE_RW, and _PAGE_DIRTY. But the check > below will always return 0 if !_PAGE_RW, unless I'm misreading it? Er, to be precise, it will always return 0 if write==1 and !_PAGE_RW.