From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932727Ab2AEUIR (ORCPT ); Thu, 5 Jan 2012 15:08:17 -0500 Received: from mx.scalarmail.ca ([98.158.95.75]:7369 "EHLO ironport-01.sms.scalar.ca" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755357Ab2AEUIQ (ORCPT ); Thu, 5 Jan 2012 15:08:16 -0500 Date: Thu, 5 Jan 2012 15:08:10 -0500 From: Nick Bowler To: Kees Cook Cc: linux-kernel@vger.kernel.org, Alexander Viro , Ingo Molnar , Andrew Morton , Rik van Riel , Federica Teodori , Lucian Adrian Grijincu , Peter Zijlstra , Eric Paris , Randy Dunlap , Dan Rosenberg , linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: Re: [PATCH v2012.1] fs: symlink restrictions on sticky directories Message-ID: <20120105200810.GA3826@elliptictech.com> References: <20120104201800.GA2587@www.outflux.net> <20120105143008.GA31728@elliptictech.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Organization: Elliptic Technologies Inc. User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2012-01-05 11:34 -0800, Kees Cook wrote: > On Thu, Jan 5, 2012 at 6:30 AM, Nick Bowler wrote: > > On 2012-01-04 12:18 -0800, Kees Cook wrote: > >> diff --git a/fs/Kconfig b/fs/Kconfig > >> index 5f4c45d..26ede24 100644 > >> --- a/fs/Kconfig > >> +++ b/fs/Kconfig > >> @@ -278,3 +278,19 @@ source "fs/nls/Kconfig" > >>  source "fs/dlm/Kconfig" > >> > >>  endmenu > >> + > >> +config PROTECTED_STICKY_SYMLINKS > >> +     bool "Protect symlink following in sticky world-writable directories" > >> +     default y > > [...] > > > > Why do we need a config option for this?  What's wrong with just using > > the sysctl? > > This way the sysctl can configured directly without needing to have a > distro add a new item to sysctl.conf. This seems totally pointless to me. There are tons of sysctls that don't have Kconfig options: what makes this one special? > > Why have you made this option "default y", when enabling it clearly > > makes user-visible changes to kernel behaviour? > > Ingo specifically asked me to make it "default y". But this is a brand new feature that changes longstanding behaviour of various syscalls. Making it default to enabled is rather mean to users (since it will tend to get enabled by "oldconfig") and seems almost guaranteed to cause regressions. Cheers, -- Nick Bowler, Elliptic Technologies (http://www.elliptictech.com/)