Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758118Ab1EaSey (ORCPT ); Tue, 31 May 2011 14:34:54 -0400 Received: from one.firstfloor.org ([213.235.205.2]:45452 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757164Ab1EaSex (ORCPT ); Tue, 31 May 2011 14:34:53 -0400 Date: Tue, 31 May 2011 20:34:48 +0200 From: Andi Kleen To: Andy Lutomirski Cc: Ingo Molnar , 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 , Andi Kleen Subject: Re: [PATCH v4 10/10] x86-64: Add CONFIG_UNSAFE_VSYSCALLS to feature-removal-schedule Message-ID: <20110531183448.GA27166@one.firstfloor.org> References: <1660d1687db01852ec58bbf970e22868db367d53.1306851090.git.luto@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1660d1687db01852ec58bbf970e22868db367d53.1306851090.git.luto@mit.edu> User-Agent: Mutt/1.4.2.2i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1082 Lines: 28 > +What: CONFIG_UNSAFE_VSYSCALLS (x86_64) > +When: When glibc 2.14 or newer is ubitquitous. Perhaps mid-2012. > +Why: Having user-executable code at a fixed address is a security problem. > + Turning off CONFIG_UNSAFE_VSYSCALLS mostly removes the risk but will > + make the time() function slower on glibc versions 2.13 and below. I disagree with this description (and the whole idea really) First it's time+gettimeofday+vgetcu, not just time. A more accurate description is "will make all x86-64 Linux programs written to the original pre vDSO syscall ABI significantly slower" And the assumption that all world is using glibc is still as bad as it was on the first po.st And it's still a bad idea. Especially since there's a much better alternative anyways for the "security problem" which has none of these drawbacks. -Andi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/