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=-13.1 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 8CF0BC43463 for ; Fri, 18 Sep 2020 21:25:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 58AD2235F8 for ; Fri, 18 Sep 2020 21:25:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726249AbgIRVZQ (ORCPT ); Fri, 18 Sep 2020 17:25:16 -0400 Received: from mga02.intel.com ([134.134.136.20]:40168 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726118AbgIRVZP (ORCPT ); Fri, 18 Sep 2020 17:25:15 -0400 IronPort-SDR: yOilVnswrj4ux1IPD2errlg1fU9PLGNc+Ym7Zqg4NDtf/+THt4vHat+sgAxggV65Be1MMk0VBq UQXnyTk48WSg== X-IronPort-AV: E=McAfee;i="6000,8403,9748"; a="147719056" X-IronPort-AV: E=Sophos;i="5.77,274,1596524400"; d="scan'208";a="147719056" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Sep 2020 14:25:15 -0700 IronPort-SDR: ZiAjpg9H+lTWiWwlbjyUOoATbibiuL2QEtEgXKwIohCa+6zltUvTvc3s1u8mlpNXGGhxxqAhG7 J6PuvaHWSUyQ== X-IronPort-AV: E=Sophos;i="5.77,274,1596524400"; d="scan'208";a="381051638" Received: from yyu32-mobl1.amr.corp.intel.com (HELO [10.212.0.248]) ([10.212.0.248]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Sep 2020 14:25:13 -0700 Subject: Re: [PATCH v12 1/8] x86/cet/ibt: Add Kconfig option for user-mode Indirect Branch Tracking To: Pavel Machek , Randy Dunlap Cc: 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" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Peter Zijlstra , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang References: <20200918192312.25978-1-yu-cheng.yu@intel.com> <20200918192312.25978-2-yu-cheng.yu@intel.com> <20200918205933.GB4304@duo.ucw.cz> From: "Yu, Yu-cheng" Message-ID: <019b5e45-b116-7f3d-f1f2-3680afbd676c@intel.com> Date: Fri, 18 Sep 2020 14:25:12 -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: <20200918205933.GB4304@duo.ucw.cz> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On 9/18/2020 1:59 PM, Pavel Machek wrote: > On Fri 2020-09-18 13:24:13, Randy Dunlap wrote: >> Hi, >> >> If you do another version of this: >> >> On 9/18/20 12:23 PM, Yu-cheng Yu wrote: >>> Introduce Kconfig option X86_INTEL_BRANCH_TRACKING_USER. >>> >>> Indirect Branch Tracking (IBT) provides protection against CALL-/JMP- >>> oriented programming attacks. It is active when the kernel has this >>> feature enabled, and the processor and the application support it. >>> When this feature is enabled, legacy non-IBT applications continue to >>> work, but without IBT protection. >>> >>> Signed-off-by: Yu-cheng Yu >>> --- >>> v10: >>> - Change build-time CET check to config depends on. >>> >>> arch/x86/Kconfig | 16 ++++++++++++++++ >>> 1 file changed, 16 insertions(+) >>> >>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig >>> index 6b6dad011763..b047e0a8d1c2 100644 >>> --- a/arch/x86/Kconfig >>> +++ b/arch/x86/Kconfig >>> @@ -1963,6 +1963,22 @@ config X86_INTEL_SHADOW_STACK_USER >>> >>> If unsure, say y. >>> >>> +config X86_INTEL_BRANCH_TRACKING_USER >>> + prompt "Intel Indirect Branch Tracking for user-mode" >>> + def_bool n >>> + depends on CPU_SUP_INTEL && X86_64 >>> + depends on $(cc-option,-fcf-protection) >>> + select X86_INTEL_CET >>> + help >>> + Indirect Branch Tracking (IBT) provides protection against >>> + CALL-/JMP-oriented programming attacks. It is active when >>> + the kernel has this feature enabled, and the processor and >>> + the application support it. When this feature is enabled, >>> + legacy non-IBT applications continue to work, but without >>> + IBT protection. >>> + >>> + If unsure, say y >> >> If unsure, say y. > > Actually, it would be "If unsure, say Y.", to be consistent with the > rest of the Kconfig. > > But I wonder if Yes by default is good idea. Only very new CPUs will > support this, right? Are they even available at the market? Should the > help text say "if your CPU is Whatever Lake or newer, ...." :-) ? I will revise the wording if there is another version. But a CET-capable kernel can run on legacy systems. We have been testing that combination. Yu-cheng