Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750917AbdCIFgZ (ORCPT ); Thu, 9 Mar 2017 00:36:25 -0500 Received: from mail-io0-f181.google.com ([209.85.223.181]:34117 "EHLO mail-io0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750724AbdCIFgX (ORCPT ); Thu, 9 Mar 2017 00:36:23 -0500 MIME-Version: 1.0 In-Reply-To: <7af7bcc9-9115-be9f-2240-a022487e9b70@redhat.com> References: <20170301125426.l4nf65rx4wahohyl@wfg-t540p.sh.intel.com> <20170302202338.ci6wwb3yzjmdy4n2@wfg-t540p.sh.intel.com> <58B88353.2010508@iogearbox.net> <58C08535.3070000@iogearbox.net> <7af7bcc9-9115-be9f-2240-a022487e9b70@redhat.com> From: Kees Cook Date: Wed, 8 Mar 2017 21:36:01 -0800 X-Google-Sender-Auth: jiMzvLLZMqjVk9CEkViQrXtyHlE Message-ID: Subject: Re: [net/bpf] 3051bf36c2 BUG: unable to handle kernel paging request at 0000a7cf To: Laura Abbott Cc: Daniel Borkmann , Linus Torvalds , Thomas Gleixner , Ingo Molnar , Peter Anvin , Fengguang Wu , Network Development , LKML , LKP , ast@fb.com, "the arch/x86 maintainers" , "David S. Miller" 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: 1201 Lines: 32 On Wed, Mar 8, 2017 at 3:55 PM, Laura Abbott wrote: > On 03/08/2017 02:36 PM, Kees Cook wrote: >> On Wed, Mar 8, 2017 at 2:27 PM, Daniel Borkmann wrote: >>> [ 28.474232] rodata_test: test data was not read only >>> [...] >> >> In my tests so far, I've never been able to get rodata_test to fail >> (Qemu 2.5.0, Ubuntu). I'll retry with your .config and see if I can >> recheck under Qemu 2.7.1. Do you see these failures on real hardware? >> >> -Kees >> > > FWIW, I'm seeing the same issue with qemu 2.6.2 and 2.8.0 on Fedora 24 > and rawhide respectively. > > I also notice that CONFIG_X86_PAE is turned off in the defconfig. If > I set CONFIG_HIGHMEM_64G which turns on CONFIG_X86_PAE the problem > goes away. I can't tell if this is an indication of magically hiding > the TLB problem or if there is an issue with !X86_PAE invalidation. I found my difference. I normally run qemu with "-cpu host" which makes the failure go away. With "-cpu kvm64", I see the rodata_test failure immediately. Seems like this may be a kvm cpu feature emulation bug? I'll see if I can find the specific cpu feature in the morning... -Kees -- Kees Cook Pixel Security