From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761863Ab3DBVeT (ORCPT ); Tue, 2 Apr 2013 17:34:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:27909 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759664Ab3DBVeS (ORCPT ); Tue, 2 Apr 2013 17:34:18 -0400 From: Paul Moore To: "H.J. Lu" , "H. Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org Cc: keescook@chromium.org, coreyb@linux.vnet.ibm.com, wad@chromium.org Subject: Re: [PATCH] x86: remove the x32 syscall bitmask from syscall_get_nr() Date: Tue, 02 Apr 2013 17:31:37 -0400 Message-ID: <1818903.DGocx9Gl7W@sifl> Organization: Red Hat User-Agent: KMail/4.10.1 (Linux/3.8.5-gentoo; KDE/4.10.1; x86_64; ; ) In-Reply-To: <1729301.D1jGz2qpIc@sifl> References: <20130215172143.12549.10292.stgit@localhost> <1729301.D1jGz2qpIc@sifl> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday, March 25, 2013 04:55:17 PM Paul Moore wrote: > On Friday, March 15, 2013 03:18:12 PM H.J. Lu wrote: > > On Fri, Mar 15, 2013 at 2:56 PM, H. Peter Anvin wrote: > > > On 03/15/2013 02:15 PM, Paul Moore wrote: > > >> On Tuesday, February 26, 2013 03:58:23 PM Paul Moore wrote: > > >>> On Friday, February 15, 2013 12:21:43 PM Paul Moore wrote: > > >>>> Commit fca460f95e928bae373daa8295877b6905bc62b8 simplified the x32 > > >>>> implementation by creating a syscall bitmask, equal to 0x40000000, > > >>>> that > > >>>> could be applied to x32 syscalls such that the masked syscall number > > >>>> would be the same as a x86_64 syscall. While that patch was a nice > > >>>> way to simplify the code, it went a bit too far by adding the mask to > > >>>> syscall_get_nr(); returning the masked syscall numbers can cause > > >>>> confusion with callers that expect syscall numbers matching the x32 > > >>>> ABI, e.g. unmasked syscall numbers. > > >>>> > > >>>> This patch fixes this by simply removing the mask from > > >>>> syscall_get_nr() > > >>>> while preserving the other changes from the original commit. While > > >>>> there are several syscall_get_nr() callers in the kernel, most simply > > >>>> check that the syscall number is greater than zero, in this case this > > >>>> patch will have no effect. Of those remaining callers, they appear > > >>>> to be few, seccomp and ftrace, and from my testing of seccomp without > > >>>> this patch the original commit definitely breaks things; the seccomp > > >>>> filter does not correctly filter the syscalls due to the difference > > >>>> in > > >>>> syscall numbers in the BPF filter and the value from > > >>>> syscall_get_nr(). > > >>>> Applying this patch restores the seccomp BPF filter functionality on > > >>>> x32. > > >>>> > > >>>> I've tested this patch with the seccomp BPF filters as well as ftrace > > >>>> and everything looks reasonable to me; needless to say general usage > > >>>> seemed fine as well. > > >>> > > >>> I just wanted to check and see where things stood with this patch. > > >>> I'm > > >>> not > > >>> overly concerned about how this problem is solved, just that it is > > >>> solved. > > >>> If someone else has a better approach that is fine with me; I'll even > > >>> make > > >>> the offer to do additional testing if needed. > > >> > > >> Anyone? The seccomp filter bits are completely broken on x32 and I'd > > >> like to get this fixed, if not with this patch then something else - > > >> I'm > > >> more than happy to test/verify/etc whatever solution is deemed best ... > > > > > > Seems good to me -- H.J., do you seen any problem with this? > > > > It looks OK to me. > > Great, any chance of getting this fix merged for 3.9? Just a ping to see where we stand on getting this patch merged. Just a reminder that SECCOMP_FILTER is completely broken on x32 and either needs this patch, or another one, to fix the regression. -- paul moore security and virtualization @ redhat