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=-3.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 2BEABC43463 for ; Fri, 18 Sep 2020 21:06:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DA08223119 for ; Fri, 18 Sep 2020 21:06:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="IWLwt/Jb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726250AbgIRVGj (ORCPT ); Fri, 18 Sep 2020 17:06:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60982 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726118AbgIRVGi (ORCPT ); Fri, 18 Sep 2020 17:06:38 -0400 Received: from mail-io1-xd42.google.com (mail-io1-xd42.google.com [IPv6:2607:f8b0:4864:20::d42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A8AEDC0613CE; Fri, 18 Sep 2020 14:06:38 -0700 (PDT) Received: by mail-io1-xd42.google.com with SMTP id y74so8460856iof.12; Fri, 18 Sep 2020 14:06:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=MvHhXjI9PINmG+l6DCDjKQZbsTRKGGMkTBP5zN5aSFQ=; b=IWLwt/JbdMSRpT6Wv3WAyCBN9qFCREgWtJcF0R1RIzLVY0SISm4RFwHsdcXIdL5d4E Yy7/2s+LDlk/87c0Fp+tQVi0zmDpn6GNtT8zIFczwsT7f4zqRnFy453Wbrx2aO+2VbVj vdaq2zhFJLmSjCLU0mocGAmtZoaaUK6RKO8Qz0A7yeJUTDJbRPhXHIh5ZOcHlXUvXFk3 LUOd/Bi9DKb0KWJIFqeinsKHmFCXFee6BbXLTqIXmNkioPBdjnv37wleZo/wrgkqn1NX 72vkgJhAipRe1DB64E2Yesd7jEdncu2/Nm2GU5jxRqcToMVoB7Ia5jtjXQAZwflWHYOc Ckjw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=MvHhXjI9PINmG+l6DCDjKQZbsTRKGGMkTBP5zN5aSFQ=; b=A/WFCEewpv/hVP+yj013d7fyobtZY8fzFKEx4Junlhi7DrYSak7z3b0OLVahYulrHB 8NFC6b6mNd7Lg5G6mwHrfT+pLbyzV96qZKN//EwbDgSCAQjNhORLMHUNyS2FKZWIyxJk Fwmrq0DlLMkxwM4DgFZu9OX4Xph7r12OwbM5AZoOtEqeGG3XGY97Wjc5gjc+3+W0d22c MGUl/FltLIoTeJuPOhJrMiqcgdDDTopfSSKUMCyffb5xylQpPxRIkFHanGHhLRqjgDYn K+UNQWnsr1jsKXu+vqb9GW7A8a27SKRn9slONAWBTY9KActvTnBsEwoIXvZer2dGEzu3 5Xrw== X-Gm-Message-State: AOAM531ceTPCGYCq7GYxVopo4hkPHCdZ4yuRW3CTkWOJHw1eUkvzV73r W/vrN/MLASot8dzmTKH08JwEr2HMjIHIuIuMrXM= X-Google-Smtp-Source: ABdhPJz3m6rfOxVGTE582qPYyesCg/UTfBm54/gjoz20D1+b0ua1bBFx46wx6IdHom/D2OhPgwwR2gJWI9CZGMjZWXc= X-Received: by 2002:a5e:9e4c:: with SMTP id j12mr29230986ioq.37.1600463197971; Fri, 18 Sep 2020 14:06:37 -0700 (PDT) MIME-Version: 1.0 References: <20200918192312.25978-1-yu-cheng.yu@intel.com> <20200918192312.25978-9-yu-cheng.yu@intel.com> <20200918210026.GC4304@duo.ucw.cz> In-Reply-To: <20200918210026.GC4304@duo.ucw.cz> From: "H.J. Lu" Date: Fri, 18 Sep 2020 14:06:02 -0700 Message-ID: Subject: Re: [PATCH v12 8/8] x86: Disallow vsyscall emulation when CET is enabled To: Pavel Machek Cc: Dave Hansen , Yu-cheng Yu , "the arch/x86 maintainers" , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , LKML , "open list:DOCUMENTATION" , Linux-MM , linux-arch , Linux API , Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Fri, Sep 18, 2020 at 2:00 PM Pavel Machek wrote: > > On Fri 2020-09-18 12:32:57, Dave Hansen wrote: > > On 9/18/20 12:23 PM, Yu-cheng Yu wrote: > > > Emulation of the legacy vsyscall page is required by some programs > > > built before 2013. Newer programs after 2013 don't use it. > > > Disable vsyscall emulation when Control-flow Enforcement (CET) is > > > enabled to enhance security. > > > > How does this "enhance security"? > > > > What is the connection between vsyscall emulation and CET? > > Boom. > > We don't break compatibility by default, and you should not tell > people to enable CET by default if you plan to do this. > Nothing will be broken. CET enabled applications don't use/need vsyscall emulation. -- H.J.