Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752399AbbHMIav (ORCPT ); Thu, 13 Aug 2015 04:30:51 -0400 Received: from mail-vk0-f45.google.com ([209.85.213.45]:35990 "EHLO mail-vk0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752332AbbHMIar (ORCPT ); Thu, 13 Aug 2015 04:30:47 -0400 MIME-Version: 1.0 From: David Drysdale Date: Thu, 13 Aug 2015 09:30:26 +0100 Message-ID: Subject: [Regression v4.2 ?] 32-bit seccomp-BPF returned errno values wrong in VM? To: Kees Cook , Denys Vlasenko , Andy Lutomirski , "linux-kernel@vger.kernel.org" , Will Drewry , Ingo Molnar Cc: Alok Kataria , Linus Torvalds , Borislav Petkov , Alexei Starovoitov , Frederic Weisbecker , "H. Peter Anvin" , Oleg Nesterov , Steven Rostedt , X86 ML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1848 Lines: 47 Hi folks, I've got an odd regression with the v4.2 rc kernel, and I wondered if anyone else could reproduce it. The problem occurs with a seccomp-bpf filter program that's set up to return an errno value -- an errno of 1 is always returned instead of what's in the filter, plus other oddities (selftest output below). The problem seems to need a combination of circumstances to occur: - The seccomp-bpf userspace program needs to be 32-bit, running against a 64-bit kernel -- I'm testing with seccomp_bpf from tools/testing/selftests/seccomp/, built via 'CFLAGS=-m32 make'. - The kernel needs to be running as a VM guest -- it occurs inside my VMware Fusion host, but not if I run on bare metal. Kees tells me he cannot repro with a kvm guest though. Bisecting indicates that the commit that induces the problem is 3f5159a9221f19b0, "x86/asm/entry/32: Update -ENOSYS handling to match the 64-bit logic", included in all the v4.2-rc* candidates. Apologies if I've just got something odd with my local setup, but the bisection was unequivocal enough that I thought it worth reporting... Thanks, David seccomp_bpf failure outputs: seccomp_bpf.c:533:global.ERRNO_valid:Expected 7 (7) == (*__errno_location ()) (1) seccomp_bpf.c:560:global.ERRNO_zero:Expected 0 (0) == read(0, ((void *)0), 0) (4294967295) seccomp_bpf.c:587:global.ERRNO_capped:Expected 4095 (4095) == (*__errno_location ()) (1) seccomp_bpf.c:905:precedence.errno_is_third:Expected 0 (0) == syscall(20) (4294967295) seccomp_bpf.c:925:precedence.errno_is_third_in_any_order:Expected 0 (0) == syscall(20) (4294967295) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/