Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754915Ab0KJIZ3 (ORCPT ); Wed, 10 Nov 2010 03:25:29 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:34600 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752734Ab0KJIZ2 (ORCPT ); Wed, 10 Nov 2010 03:25:28 -0500 Date: Wed, 10 Nov 2010 09:25:16 +0100 From: Ingo Molnar To: Dan Rosenberg Cc: linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, kees.cook@canonical.com, Andrew Morton Subject: Re: [PATCH v2] Restrict unprivileged access to kernel syslog Message-ID: <20101110082516.GB3341@elte.hu> 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> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1609 Lines: 39 * 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: Ingo Molnar Linus, Andrew, any objections against pushing this trivial control flag upstream out of band, after a bit of testing? It's not like it can break anything, and the flag is very useful to distros. Thanks, Ingo -- 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/