From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755895Ab1BIVkL (ORCPT ); Wed, 9 Feb 2011 16:40:11 -0500 Received: from brother.balabit.com ([195.70.62.219]:60316 "EHLO lists.balabit.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755823Ab1BIVkJ (ORCPT ); Wed, 9 Feb 2011 16:40:09 -0500 Subject: Re: CAP_SYSLOG, 2.6.38 and user space From: Gergely Nagy To: david@lang.hm Cc: "Serge E. Hallyn" , James Morris , Linux Kernel Mailing List In-Reply-To: References: <1296733177.14846.26.camel@moria> <20110203153252.GA24153@mail.hallyn.com> <20110204160513.GB17396@mail.hallyn.com> <1296837186.24742.15.camel@moria> <20110204171502.GA24226@mail.hallyn.com> <20110206011831.GB15805@mail.hallyn.com> <20110209212329.GA24777@mail.hallyn.com> <1297286934.13055.57.camel@luthien.mhp> Content-Type: text/plain; charset="UTF-8" Organization: BalaBit Date: Wed, 09 Feb 2011 22:40:04 +0100 Message-ID: <1297287604.13055.65.camel@luthien.mhp> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2011-02-09 at 13:34 -0800, david@lang.hm wrote: > On Wed, 9 Feb 2011, Gergely Nagy wrote: > > > On Wed, 2011-02-09 at 21:23 +0000, Serge E. Hallyn wrote: > >> So if that's how we're leaning, then the following patch is much more > >> concise. I'll send this to Linus and any appropriate -stable tomorrow > >> if noone objects. > >> > >> From 5166e114d6a7c508addbadd763322089eb0b02f5 Mon Sep 17 00:00:00 2001 > >> From: Serge Hallyn > >> Date: Thu, 3 Feb 2011 09:26:15 -0600 > >> Subject: [PATCH 1/1] cap_syslog: don't refuse cap_sys_admin for now (v2) > >> > >> It'd be nice to do that later, but it's not strictly necessary, > >> and it'll be hard to do without breaking somebody's userspace. > >> > >> Signed-off-by: Serge Hallyn > >> --- > >> kernel/printk.c | 14 ++++---------- > >> 1 files changed, 4 insertions(+), 10 deletions(-) > > > > Personally, I'd prefer the sysctl idea in the long run, because > > userspace can easily and automatically adapt to the running kernel then. > > Ie, this patch is fine for 2.6.38, but later on, a sysctl could be > > introduced, that when set (but defaulting to unset, as to not break > > userspace), would make CAP_SYS_ADMIN return -EPERM. That way, syslogds > > could look at the setting, and act accordingly. This would mean that old > > userspace wouldn't break, and upgraded userspace could work on both old > > and new kernels, depending on the setting. Distros or admins could then > > enable the sysctl once they made sure that all neccessary applications > > have been upgraded. > > what is your justification for ever having CAP_SYS_ADMIN return -EPERM? > what's the value in blocking this. Nothing. Come to think of it, the main use of the sysctl would be to detect CAP_SYSLOG support, so that applications can drop CAP_SYS_ADMIN and use CAP_SYSLOG only (which, imo, is a good idea - the less capabilities, the better, and CAP_SYS_ADMIN is quite broad when one only wants CAP_SYSLOG). If there's a better way to allow userspace to easily detect CAP_SYSLOG, I'm all for that. -- |8]