From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751385AbeBVV1g (ORCPT ); Thu, 22 Feb 2018 16:27:36 -0500 Received: from mail-sn1nam02on0058.outbound.protection.outlook.com ([104.47.36.58]:65034 "EHLO NAM02-SN1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750776AbeBVV1f (ORCPT ); Thu, 22 Feb 2018 16:27:35 -0500 From: Nadav Amit To: Dave Hansen CC: "linux-kernel@vger.kernel.org" , "aarcange@redhat.com" , "luto@kernel.org" , "torvalds@linux-foundation.org" , "keescook@google.com" , "hughd@google.com" , "jgross@suse.com" , "x86@kernel.org" Subject: Re: [RFC][PATCH 04/10] x86/espfix: use kernel-default PTE mask Thread-Topic: [RFC][PATCH 04/10] x86/espfix: use kernel-default PTE mask Thread-Index: AQHTrBzppP06ODhzzkSqFbT0POLSXKOw76qA Date: Thu, 22 Feb 2018 21:27:31 +0000 Message-ID: <93613F56-C778-4EA0-8945-A0B8ABC1A5FD@vmware.com> References: <20180222203651.B776810C@viggo.jf.intel.com> <20180222203658.80705136@viggo.jf.intel.com> In-Reply-To: <20180222203658.80705136@viggo.jf.intel.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [208.91.2.2] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;BY2PR05MB661;20:SXlwyYNfqJEpjp/FmXehge16nRqZnvk5mPbPXc/mQ+ajiZ+metp/kXTc84onOuFupiVpuUFl4Xl4hhUiU3LEuXZsOFVQ8RxPjfliyQkuPDEjt3lkg9LsovAVrtU1YjYzlc90AFjrpn/Gj8jELm2btriv/9E086wr6iK3KMXHEvo= x-ms-exchange-antispam-srfa-diagnostics: SSOS; x-ms-office365-filtering-correlation-id: f2577062-77dd-4a03-8e6e-08d57a3b1503 x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(4534165)(4627221)(201703031133081)(201702281549075)(5600026)(4604075)(3008032)(2017052603307)(7153060)(7193020);SRVR:BY2PR05MB661; x-ms-traffictypediagnostic: BY2PR05MB661: x-microsoft-antispam-prvs: x-exchange-antispam-report-test: UriScan:(228905959029699); x-exchange-antispam-report-cfa-test: BCL:0;PCL:0;RULEID:(8211001082)(6040501)(2401047)(8121501046)(5005006)(93006095)(93001095)(10201501046)(3231166)(944501161)(52105095)(3002001)(6041288)(20161123560045)(20161123562045)(20161123564045)(201703131423095)(201702281528075)(20161123555045)(201703061421075)(201703061406153)(20161123558120)(6072148)(201708071742011);SRVR:BY2PR05MB661;BCL:0;PCL:0;RULEID:;SRVR:BY2PR05MB661; x-forefront-prvs: 059185FE08 x-forefront-antispam-report: SFV:NSPM;SFS:(10009020)(979002)(39860400002)(376002)(396003)(346002)(39380400002)(366004)(189003)(199004)(2950100002)(3660700001)(14454004)(6116002)(4326008)(6486002)(26005)(99286004)(33656002)(105586002)(106356001)(229853002)(25786009)(102836004)(3846002)(5660300001)(6346003)(6436002)(86362001)(83716003)(77096007)(6506007)(6512007)(68736007)(53936002)(36756003)(2906002)(305945005)(7736002)(3280700002)(186003)(6916009)(316002)(76176011)(6246003)(2900100001)(66066001)(82746002)(81166006)(81156014)(97736004)(478600001)(54906003)(8936002)(8676002)(969003)(989001)(999001)(1009001)(1019001);DIR:OUT;SFP:1101;SCL:1;SRVR:BY2PR05MB661;H:BY2PR05MB2215.namprd05.prod.outlook.com;FPR:;SPF:None;PTR:InfoNoRecords;MX:1;A:1;LANG:en; authentication-results: spf=none (sender IP is ) smtp.mailfrom=namit@vmware.com; x-microsoft-antispam-message-info: yov885qzC+H8B2L51HF+Lt+Asgo86Fb1DGsZ3t0azj9RVQNehQVcyosf91j5/+E4nAsb2qaFhrWRQjJYIUR+xBM4sPhS0MoUhqfRH2YzYo1ZBgCz5+MtegN3Wmocno29g13V5bWghJJkjwpA3Hw8WE/887iwrYLpEazDAOAoJJI= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="us-ascii" Content-ID: <606C13CC94DCAC45B5B64D63B3C506E4@namprd05.prod.outlook.com> MIME-Version: 1.0 X-OriginatorOrg: vmware.com X-MS-Exchange-CrossTenant-Network-Message-Id: f2577062-77dd-4a03-8e6e-08d57a3b1503 X-MS-Exchange-CrossTenant-originalarrivaltime: 22 Feb 2018 21:27:31.5600 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: b39138ca-3cee-4b4a-a4d6-cd83d9dd62f0 X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY2PR05MB661 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id w1MLRgj1020605 Dave Hansen wrote: > > From: Dave Hansen > > In creating its page tables, the espfix code masks its PGTABLE_PROT > value with the supported mask: __supported_pte_mask. This ensures > that unsupported bits are not set in the final PTE. But, it also > sets _PAGE_GLOBAL which we do not want for PTE. Use > __default_kernel_pte_mask instead which clears _PAGE_GLOBAL for PTI. Can you please explain what is your concern? Exposing more gadgets for speculative ROP attacks? Or is it a general rule of not exposing any kernel code &data more than absolutely necessary?