From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754794AbbJ1AMp (ORCPT ); Tue, 27 Oct 2015 20:12:45 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:38417 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754046AbbJ1AMo (ORCPT ); Tue, 27 Oct 2015 20:12:44 -0400 Date: Wed, 28 Oct 2015 09:12:40 +0900 From: Greg KH To: Stephen Smalley Cc: keescook@chromium.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] lkdtm: fix ACCESS_USERSPACE test Message-ID: <20151028001240.GA2971@kroah.com> References: <1445978873-20870-1-git-send-email-sds@tycho.nsa.gov> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1445978873-20870-1-git-send-email-sds@tycho.nsa.gov> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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)? thanks, greg k-h