Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756696Ab0KJP3l (ORCPT ); Wed, 10 Nov 2010 10:29:41 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:55553 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756246Ab0KJP3k (ORCPT ); Wed, 10 Nov 2010 10:29:40 -0500 Date: Wed, 10 Nov 2010 07:26:38 -0800 From: Andrew Morton To: Ingo Molnar Cc: Dan Rosenberg , linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, kees.cook@canonical.com Subject: Re: [PATCH v2] Restrict unprivileged access to kernel syslog Message-Id: <20101110072638.b0e5473d.akpm@linux-foundation.org> In-Reply-To: <20101110082516.GB3341@elte.hu> References: <1289348309.7380.31.camel@dan> <20101110082516.GB3341@elte.hu> X-Mailer: Sylpheed 2.7.1 (GTK+ 2.18.9; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1997 Lines: 47 On Wed, 10 Nov 2010 09:25:16 +0100 Ingo Molnar wrote: > > * 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. > OK by me, apart from ... a) I'd question the need for the config option. Are distros really so lame that they can't trust themselves to poke a number into procfs at boot time? b) we have "dmesg_restrict" and "CONFIG_RESTRICT_DMESG". Less dyslexia, please. -- 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/