From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756968AbbJ2N2v (ORCPT ); Thu, 29 Oct 2015 09:28:51 -0400 Received: from emvm-gh1-uea09.nsa.gov ([63.239.67.10]:50080 "EHLO emvm-gh1-uea09.nsa.gov" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751711AbbJ2N2u (ORCPT ); Thu, 29 Oct 2015 09:28:50 -0400 X-TM-IMSS-Message-ID: <807464ae000ae208@nsa.gov> Subject: Re: [PATCH] lkdtm: fix ACCESS_USERSPACE test To: Greg KH References: <1445978873-20870-1-git-send-email-sds@tycho.nsa.gov> <20151028001240.GA2971@kroah.com> Cc: keescook@chromium.org, linux-kernel@vger.kernel.org From: Stephen Smalley X-Enigmail-Draft-Status: N1110 Organization: National Security Agency Message-ID: <56321EF7.70407@tycho.nsa.gov> Date: Thu, 29 Oct 2015 09:28:23 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <20151028001240.GA2971@kroah.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/27/2015 08:12 PM, Greg KH wrote: > On Tue, Oct 27, 2015 at 04:47:53PM -0400, Stephen Smalley wrote: >> Add a copy_to_user() call to the ACCESS_USERSPACE test >> prior to attempting direct dereferencing of the user >> address to ensure the page is present. Otherwise, >> a fault occurs on arm kernels even prior to the introduction >> of CONFIG_CPU_SW_DOMAIN_PAN, and there is no difference in >> behavior for CONFIG_CPU_SW_DOMAIN_PAN=n vs CONFIG_CPU_SW_DOMAIN_PAN=y. >> >> Before this change, for any value of CONFIG_CPU_SW_DOMAIN_PAN: >> lkdtm: Performing direct entry ACCESS_USERSPACE >> lkdtm: attempting bad read at b6fe8000 >> Unable to handle kernel paging request at virtual address b6fe8000 >> >> After this change, for CONFIG_CPU_SW_DOMAIN_PAN=n: >> lkdtm: Performing direct entry ACCESS_USERSPACE >> lkdtm: attempting bad read at b6efc000 >> lkdtm: attempting bad write at b6efc000 >> >> After this change, for CONFIG_CPU_SW_DOMAIN_PAN=y: >> lkdtm: Performing direct entry ACCESS_USERSPACE >> lkdtm: attempting bad read at b6f7d000 >> Unhandled fault: page domain fault (0x01b) at 0xb6f7d000 >> ... >> >> Signed-off-by: Stephen Smalley >> --- >> drivers/misc/lkdtm.c | 8 +++++++- >> 1 file changed, 7 insertions(+), 1 deletion(-) > > Should this also be applied to older kernels (i.e. a stable fix)? I don't think it qualifies (only a fix for a kernel crash test), but will defer to Kees.