Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758177Ab1EaS5o (ORCPT ); Tue, 31 May 2011 14:57:44 -0400 Received: from www.linutronix.de ([62.245.132.108]:42995 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756654Ab1EaS5n (ORCPT ); Tue, 31 May 2011 14:57:43 -0400 Date: Tue, 31 May 2011 20:57:27 +0200 (CEST) From: Thomas Gleixner To: Andi Kleen cc: Andy Lutomirski , Ingo Molnar , x86@kernel.org, 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 v4 10/10] x86-64: Add CONFIG_UNSAFE_VSYSCALLS to feature-removal-schedule In-Reply-To: <20110531183448.GA27166@one.firstfloor.org> Message-ID: References: <1660d1687db01852ec58bbf970e22868db367d53.1306851090.git.luto@mit.edu> <20110531183448.GA27166@one.firstfloor.org> User-Agent: Alpine 2.02 (LFD 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1213 Lines: 33 On Tue, 31 May 2011, Andi Kleen wrote: > > +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. How about posting an alternative patch? Thanks, tglx -- 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/