From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030622AbXCBWUi (ORCPT ); Fri, 2 Mar 2007 17:20:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030628AbXCBWUi (ORCPT ); Fri, 2 Mar 2007 17:20:38 -0500 Received: from mx1.redhat.com ([66.187.233.31]:41013 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030622AbXCBWUh (ORCPT ); Fri, 2 Mar 2007 17:20:37 -0500 Message-ID: <45E8A300.9020001@redhat.com> Date: Fri, 02 Mar 2007 17:19:44 -0500 From: Chuck Ebbert Organization: Red Hat User-Agent: Thunderbird 1.5.0.9 (X11/20070212) MIME-Version: 1.0 To: John Reiser CC: Oleg Nesterov , Andi Kleen , Ingo Molnar , Arjan van de Ven , Paul Mundt , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: + fully-honor-vdso_enabled.patch added to -mm tree References: <20070301175207.GA849@tv-sign.ru> <45E891E6.7090807@BitWagon.com> In-Reply-To: <45E891E6.7090807@BitWagon.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org John Reiser wrote: > The value of ->sysenter_return is interpreted in user space by the > sysexit instruction; nobody else cares what the value is. The kernel > is not required to provide a good value when vdso_enabled is zero, > because the kernel has not told the process that sysenter is valid > (by setting AT_SYSINFO.) Doesn't matter because a malicious user can still execute sysenter. We do have to deal with that somehow, so we have to put something safe in there. > Correct. Changing vdso_enabled from 0 to non-zero must be prepared > to lose this race if it is not prevented. Ordinarily it won't matter > because the administrator will perform such changes at a "quiet" time. > We have to deal with all the possibilities here, too.