Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756952Ab0KJQc4 (ORCPT ); Wed, 10 Nov 2010 11:32:56 -0500 Received: from smtp.outflux.net ([198.145.64.163]:55070 "EHLO smtp.outflux.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756901Ab0KJQcz (ORCPT ); Wed, 10 Nov 2010 11:32:55 -0500 Date: Wed, 10 Nov 2010 08:32:45 -0800 From: Kees Cook To: Dan Rosenberg Cc: linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, mingo@elte.hu Subject: Re: [PATCH v2] Restrict unprivileged access to kernel syslog Message-ID: <20101110163245.GM5876@outflux.net> References: <1289348309.7380.31.camel@dan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1289348309.7380.31.camel@dan> Organization: Canonical X-HELO: www.outflux.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1550 Lines: 36 On Tue, Nov 09, 2010 at 07:18:29PM -0500, Dan Rosenberg wrote: > The kernel syslog contains debugging information that is often useful > during exploitation of other vulnerabilities, such as kernel heap > addresses. Rather than futilely attempt to sanitize hundreds (or > thousands) of printk statements and simultaneously cripple useful > debugging functionality, it is far simpler to create an option that > prevents unprivileged users from reading the syslog. > > This patch, loosely based on grsecurity's GRKERNSEC_DMESG, creates the > dmesg_restrict sysctl. When set to "0", the default, no restrictions > are enforced. When set to "1", only users with CAP_SYS_ADMIN can read > the kernel syslog via dmesg(8) or other mechanisms. > > v2 adds CONFIG_SECURITY_RESTRICT_DMESG. When enabled, the default > sysctl value is set to "1". When disabled, the default sysctl value is > set to "0". > > Signed-off-by: Dan Rosenberg > CC: Linus Torvalds > CC: Ingo Molnar > CC: Kees Cook > CC: stable Acked-by: Kees Cook As before, this looks fine and does the right thing with regard to /proc access to the kernel log. -- Kees Cook Ubuntu Security Team -- 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/