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=-5.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 909B2C433E4 for ; Tue, 25 Aug 2020 00:32:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 704CA2074D for ; Tue, 25 Aug 2020 00:32:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598315572; bh=HzNRSUeUL6OriNoi411G8DjwqUuqi7JFl1V+hmvfPWg=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=YhcyjGGiJEpgKGUjdHfniETEH6dgHTjhzBKq+wz9212gQ+/v/xq+Gkg5Dft+XP5uH RbZ7dJKIwAVArL3G0+QNYJKV8K+Dbk2NKBrVhPmEcqgh62o/JguET0jZ2nxWqnQU7T PcdOBymR4NYrWCCjCep2nvvGwHfoSvID1tomiVBE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728261AbgHYAcv (ORCPT ); Mon, 24 Aug 2020 20:32:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:41524 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728437AbgHYAct (ORCPT ); Mon, 24 Aug 2020 20:32:49 -0400 Received: from mail-wm1-f41.google.com (mail-wm1-f41.google.com [209.85.128.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DB8602177B for ; Tue, 25 Aug 2020 00:32:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598315569; bh=HzNRSUeUL6OriNoi411G8DjwqUuqi7JFl1V+hmvfPWg=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=uRWu1h/pRTe38+cnhWVoUjMTGyUxj4FX6LHXPmQOHohc0UiMAuVFXRFfGvQuUXiFU x0m9GY1EjwLb2Vn/RymkjG2w7e8cfbzAb7e02+yOOlT1W3LXR000Pr7kw4RnV+6ZXj WrQB1im2A7usG0ceNRnrso4/XUttJEJC2aZHtYTM= Received: by mail-wm1-f41.google.com with SMTP id c19so579267wmd.1 for ; Mon, 24 Aug 2020 17:32:48 -0700 (PDT) X-Gm-Message-State: AOAM53156OPMtvObyD5jLTEqXJStIuW2cvGsa31Ry4lGSs/BX+U5vL1s 4+oqY9wdGJrfNsNV7daIS1JbwADXn9xmOzJXDKHtMg== X-Google-Smtp-Source: ABdhPJyauPayFdftcuPZnq0MJTSphzvI2x0UgLNn081J3B9GZfktgEGZliAmuQJq8JPRJLx6kwBNbrs1VoFPRwDiqF4= X-Received: by 2002:a7b:ca48:: with SMTP id m8mr1581098wml.36.1598315567552; Mon, 24 Aug 2020 17:32:47 -0700 (PDT) MIME-Version: 1.0 References: <20200825002645.3658-1-yu-cheng.yu@intel.com> <20200825002645.3658-10-yu-cheng.yu@intel.com> In-Reply-To: <20200825002645.3658-10-yu-cheng.yu@intel.com> From: Andy Lutomirski Date: Mon, 24 Aug 2020 17:32:35 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v11 9/9] x86: Disallow vsyscall emulation when CET is enabled To: Yu-cheng Yu Cc: X86 ML , "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 , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang Content-Type: text/plain; charset="UTF-8" Sender: linux-api-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Mon, Aug 24, 2020 at 5:30 PM Yu-cheng Yu wrote: > > From: "H.J. Lu" > > Emulation of the legacy vsyscall page is required by some programs built > before 2013. Newer programs after 2013 don't use it. Disallow vsyscall > emulation when Control-flow Enforcement (CET) is enabled to enhance > security. NAK. By all means disable execute emulation if CET-IBT is enabled at the time emulation is attempted, and maybe even disable the vsyscall page entirely if you can magically tell that CET-IBT will be enabled when a process starts, but you don't get to just disable it outright on a CET-enabled kernel.