From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751061AbWEVR1W (ORCPT ); Mon, 22 May 2006 13:27:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751065AbWEVR1W (ORCPT ); Mon, 22 May 2006 13:27:22 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:63364 "EHLO mx3.mail.elte.hu") by vger.kernel.org with ESMTP id S1750996AbWEVR1V (ORCPT ); Mon, 22 May 2006 13:27:21 -0400 Date: Mon, 22 May 2006 19:27:10 +0200 From: Ingo Molnar To: Andrew Morton Cc: Zachary Amsden , jakub@redhat.com, rusty@rustcorp.com.au, linux-kernel@vger.kernel.org, torvalds@osdl.org, virtualization@lists.osdl.org, kraxel@suse.de Subject: Re: [PATCH] Gerd Hoffman's move-vsyscall-into-user-address-range patch Message-ID: <20060522172710.GA22823@elte.hu> References: <1147759423.5492.102.camel@localhost.localdomain> <20060516064723.GA14121@elte.hu> <1147852189.1749.28.camel@localhost.localdomain> <20060519174303.5fd17d12.akpm@osdl.org> <20060522162949.GG30682@devserv.devel.redhat.com> <4471EA60.8080607@vmware.com> <20060522101454.52551222.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060522101454.52551222.akpm@osdl.org> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=AWL autolearn=no SpamAssassin version=3.0.3 0.0 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Andrew Morton wrote: > Zachary Amsden wrote: > > > > Jakub Jelinek wrote: > > > > > > That's known bug in early glibcs short after adding vDSO support. > > > The vDSO support has been added in May 2003 to CVS glibc (i.e. post glibc > > > 2.3.2) and the problems have been fixed when they were discovered, in > > > February 2004: > > > http://sources.redhat.com/ml/libc-hacker/2004-02/msg00053.html > > > http://sources.redhat.com/ml/libc-hacker/2004-02/msg00059.html > > > > > > I strongly believe we want randomized vDSOs, people are already abusing the > > > fix mapped vDSO for attacks, and I think the unfortunate 10 months of broken > > > glibc shouldn't stop that forever. Anyone using such glibc can still use > > > vdso=0, or do that just once and upgrade to somewhat more recent glibc. > > > > > > > While I'm now inclined to agree with randomization, I think the default > > should be off. You can quite easily "echo 1 > > > /proc/sys/kernel/vdso_randomization" in the RC scripts, which allows you > > to maintain compatibility for everyone and get randomization turned on > > early enough to thwart attacks against any vulnerable daemons. > > > > It kinda sucks but yes, that's obviously least-breakage approach. It > does mean that many people won't benefit from (and won't test!) the > new feature though. very much so. Especially for security it's really bad if a feature is default-off. I'm quite strongly against such an approach. > Unless there's some sneaky way of auto-detecting a modern userspace, > perhaps (something which mounts /sys?). i'd rather not overdesign it. And unfortunately there is no good way to autodetect it. > All very sad. is it really a big problem to add "vdso=0" to the long list of requirements you need to run a 2.6 kernel on an old distribution (or to disable CONFIG_VDSO)? FC1 wasnt even 2.6-ready, it used a 2.4 kernel! Ingo