From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751133Ab3BOTDP (ORCPT ); Fri, 15 Feb 2013 14:03:15 -0500 Received: from terminus.zytor.com ([198.137.202.10]:36987 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750755Ab3BOTDO (ORCPT ); Fri, 15 Feb 2013 14:03:14 -0500 Message-ID: <511E8659.6030601@zytor.com> Date: Fri, 15 Feb 2013 11:02:49 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 MIME-Version: 1.0 To: Paul Moore CC: x86@kernel.org, linux-kernel@vger.kernel.org, coreyb@linux.vnet.ibm.com, wad@chromium.org Subject: Re: [PATCH] x86: remove the x32 syscall bitmask from syscall_get_nr() References: <20130215172143.12549.10292.stgit@localhost> In-Reply-To: <20130215172143.12549.10292.stgit@localhost> X-Enigmail-Version: 1.5 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/15/2013 09:21 AM, 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. > Hi... it isn't 100% clear from the description if you have audited *all* the callers? -hpa