From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756549Ab1E3LAB (ORCPT ); Mon, 30 May 2011 07:00:01 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:40133 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753791Ab1E3LAA (ORCPT ); Mon, 30 May 2011 07:00:00 -0400 Date: Mon, 30 May 2011 12:59:37 +0200 From: Ingo Molnar To: Andrew Lutomirski Cc: x86@kernel.org, Thomas Gleixner , linux-kernel@vger.kernel.org, Jesper Juhl , Borislav Petkov , Linus Torvalds , Andrew Morton , Arjan van de Ven , Jan Beulich , richard -rw- weinberger , Mikael Pettersson Subject: Re: [PATCH v2 08/10] x86-64: Emulate vsyscalls Message-ID: <20110530105937.GB20133@elte.hu> References: <07445623494a3d9f02581eb06326420f5f443043.1306724657.git.luto@mit.edu> <20110530074608.GD27557@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Andrew Lutomirski wrote: > On Mon, May 30, 2011 at 3:46 AM, Ingo Molnar wrote: > > > > * Andy Lutomirski wrote: > > > >> There's a fair amount of code in the vsyscall page, and who knows > >> what will happen if an exploit jumps into the middle of it.  Reduce > >> the risk by replacing most of it with short magic incantations that > >> are useless if entered in the middle.  This change can be disabled > >> by CONFIG_UNSAFE_VSYSCALLS (default y). > > > > btw., please flip the default or consider removing the option > > altogether. > > > > We want to improve security and we want safe vsyscalls the default, > > and it's no good if we make it too easy for users to keep the fire > > door open all the time! :-) > > I'd advocate waiting until glibc 2.14 comes out with this change: > > http://sourceware.org/git/?p=glibc.git;a=commit;h=a8509ca540427502bd955f35296ff7b727c7a8a1 > > I want to add a warning (ratelimited to an extremely low rate) in v3 > whenever any of the vsyscalls get used telling users that their legacy > code is suffering a performance impact, but it seems like bad form to > tell people to build glibc from git to avoid a regression. But only statically built binaries would be impacted in practice, right? The number of statically built binaries that heavily rely on vsyscalls ought to be a very small set ... Thanks, Ingo