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

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Date:	Fri, 4 Feb 2011 11:08:42 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Gergely Nagy <algernon@...abit.hu>
Cc:	Marc Koschewski <marc@...nowledge.org>, 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

> 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.

If you do it right you don't need both, you need either, so old code will
use CAP_SYS_ADMIN and work, newer code will use CAP_SYSLOG and work but
hold less rights. In a couple of years you can then drop the
CAP_SYS_ADMIN ability to read log files, providing it is in the list of
API deprecations soon...

> 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!

Still a mess, we don't break ABIs at random so this patch needs reverting
or fixing ASAP, otherwise Linus will just revert it anyway..

Alan
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