Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753990Ab2KSSOt (ORCPT ); Mon, 19 Nov 2012 13:14:49 -0500 Received: from mail-oa0-f46.google.com ([209.85.219.46]:43050 "EHLO mail-oa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752978Ab2KSSOr (ORCPT ); Mon, 19 Nov 2012 13:14:47 -0500 MIME-Version: 1.0 In-Reply-To: References: <20121117002016.GA13493@www.outflux.net> <20121117002753.GA22778@kroah.com> Date: Mon, 19 Nov 2012 10:14:46 -0800 X-Google-Sender-Auth: 7n5hm9OGbAg3acOidamg0FQOJws Message-ID: Subject: Re: [PATCH] devtmpfs: mount with noexec and nosuid From: Kees Cook To: Kay Sievers Cc: Greg Kroah-Hartman , linux-kernel@vger.kernel.org, ellyjones@chromium.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1531 Lines: 39 On Fri, Nov 16, 2012 at 4:39 PM, Kay Sievers wrote: > On Sat, Nov 17, 2012 at 1:27 AM, Greg Kroah-Hartman > wrote: >> On Fri, Nov 16, 2012 at 04:20:16PM -0800, Kees Cook wrote: >>> Since devtmpfs is writable, make the default noexec nosuid as well. This >>> protects from the case of a privileged process having an arbitrary file >>> write flaw and an argumentless arbitrary execution (i.e. it would lack >>> the ability to run "mount -o remount,exec,suid /dev"), with a system >>> that already has nosuid,noexec on all other writable mounts. >>> >>> Cc: ellyjones@chromium.org >>> Signed-off-by: Kees Cook >>> --- >>> drivers/base/devtmpfs.c | 6 ++++-- >>> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> Have you tested this to verify that it doesn't break anything? >> >> Kay, could this cause any problems that you could think of? > > It breaks all sorts of old, possibly outdated, stuff, that does things > like mapping /dev/mem executable. It for sure used to break X drivers, > that fiddle with the BIOS of cards. Ah, yeah, you're totally right. Attempting an mmap with PROT_EXEC on /dev/mem would be denied. Is this something we could put behind a CONFIG? -Kees -- Kees Cook Chrome OS Security -- 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/