From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753625Ab2KYWzg (ORCPT ); Sun, 25 Nov 2012 17:55:36 -0500 Received: from mx1.redhat.com ([209.132.183.28]:34534 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753564Ab2KYWzf (ORCPT ); Sun, 25 Nov 2012 17:55:35 -0500 Date: Sun, 25 Nov 2012 23:55:33 +0100 From: Oleg Nesterov To: Amnon Shiloh Cc: Cyrill Gorcunov , Pavel Emelyanov , Steven Rostedt , Frederic Weisbecker , Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org Subject: Re: arch_check_bp_in_kernelspace: fix the range check Message-ID: <20121125225533.GA24905@redhat.com> References: <20121123163320.GA32716@redhat.com> <20121124134511.47C5A592076@miso.sublimeip.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121124134511.47C5A592076@miso.sublimeip.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/25, Amnon Shiloh wrote: > > 2) I was then told (in my own words): "oh, don't worry, the vsyscall page > has now been minimized, all it contains now is *real* system calls, > and it always calls them". Not sure where did you get this idea ;) From the very beginning you were told that EMULATE mode doesn't do this. The NATIVE mode should be fine, yes. > 6) I just suggested an alternative: to have the whole vsyscall page > removed on a per-process basis. I accept your reply that this is > not possible. Yes, this is not possible. > 7) I suggested a third alternative: to have the vsyscall page be > unexecutable on a per-process basis, Like above, this is simply not possible. And at the same time the vsyscall page is already unexecutable in EMULATE mode, but globally. > 8) Any solution that allows a ptracer to prevent its traced process > from entering the vsyscall page and execute there system-calls > unchecked (thus in effect escape its jailer), would do for me. Well. I am even more confused... probably this was already discussed and I missed this, but. Why do you need to _prevent_, say, sys_gettimeofday()? Why we can't change emulate_vsyscall() to respect PTRACE_SYSCALL and report TRAP_VSYSCALL or PTRACE_EVENT_VSYSCALL as I tried to suggest in http://marc.info/?l=linux-kernel&m=135343635523715 ? You previously replied that this can not work. Now that you see that this _can_ work, could you please explain why this is not enough? Oleg.