linux-kernel - Re: CAP_SYSLOG, 2.6.38 and user space

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Date:	Fri, 04 Feb 2011 09:40:04 +0100
From:	Gergely Nagy <algernon@...abit.hu>
To:	Marc Koschewski <marc@...nowledge.org>
Cc:	david@...g.hm, "Serge E. Hallyn" <serge@...lyn.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	James Morris <jmorris@...ei.org>
Subject: Re: CAP_SYSLOG, 2.6.38 and user space

On Fri, 2011-02-04 at 09:03 +0100, Marc Koschewski wrote:
> Moreover, this change really is 'hell' on _many_ machines. We had discussed a
> thousands time to not break existing applications. So a) either make it optional in
> the kernel so that userspace still works with CAP_SYS_ADMIN _and_ CAP_SYSLOG
> while dropping a note that it should be fixed in userspace _and_ mark it as
> deprecated as of mid 2012 or b) revert it.

I think the sysctl method would be superior, because it places the
migration time in the hands of the distributions/admins, and gives
syslogds a way to adjust, and use either CAP_SYS_ADMIN or CAP_SYSLOG,
based on the presence of the sysctl setting (as opposed to using either
and just postponing the flag-day from 2.6.38 to mid 2012, where we'd
have the same issues we have now: unupgraded userspace breaking).

Having both CAP_SYS_ADMIN and CAP_SYSLOG at the same time, for the sole
purpose of reading kernel log messages would kind of defeat the purpose
of CAP_SYSLOG. Therefore, a solution that allows both at the same time
doesn't look all that good to me.

However, having it toggle-able does, and solves all my worries at least:
defaulting to CAP_SYS_ADMIN maintains backwards compatibility, upgraded
systems can switch to CAP_SYSLOG if and when the system is ready for
that. All's well!

-- 
|8]

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