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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 DFA3BC43464 for ; Fri, 18 Sep 2020 21:08:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A3E9723119 for ; Fri, 18 Sep 2020 21:08:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726157AbgIRVI0 (ORCPT ); Fri, 18 Sep 2020 17:08:26 -0400 Received: from jabberwock.ucw.cz ([46.255.230.98]:33610 "EHLO jabberwock.ucw.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726118AbgIRVI0 (ORCPT ); Fri, 18 Sep 2020 17:08:26 -0400 X-Greylist: delayed 529 seconds by postgrey-1.27 at vger.kernel.org; Fri, 18 Sep 2020 17:08:25 EDT Received: by jabberwock.ucw.cz (Postfix, from userid 1017) id E8B041C0B8D; Fri, 18 Sep 2020 23:00:26 +0200 (CEST) Date: Fri, 18 Sep 2020 23:00:26 +0200 From: Pavel Machek To: Dave Hansen Cc: Yu-cheng Yu , 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 , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang Subject: Re: [PATCH v12 8/8] x86: Disallow vsyscall emulation when CET is enabled Message-ID: <20200918210026.GC4304@duo.ucw.cz> References: <20200918192312.25978-1-yu-cheng.yu@intel.com> <20200918192312.25978-9-yu-cheng.yu@intel.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="OBd5C1Lgu00Gd/Tn" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org --OBd5C1Lgu00Gd/Tn Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable 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. >=20 > How does this "enhance security"? >=20 > 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. Best regards, Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --OBd5C1Lgu00Gd/Tn Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iF0EABECAB0WIQRPfPO7r0eAhk010v0w5/Bqldv68gUCX2Uf6gAKCRAw5/Bqldv6 8qBcAJ0YJtWeTjQjXFucIva3HllV8Nh3fQCgmunsWFmIupuoMiilfqXcz7sKnsA= =pXmh -----END PGP SIGNATURE----- --OBd5C1Lgu00Gd/Tn--