linux-kernel - Re: [kernel-hardening] Re: [RFC PATCH 2/2] mm: restrict access to /proc/slabinfo

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Date:	Mon, 19 Sep 2011 16:36:38 -0400
From:	Valdis.Kletnieks@...edu
To:	Christoph Lameter <cl@...two.org>
Cc:	Vasiliy Kulikov <segoon@...nwall.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Andrew Morton <akpm@...ux-foundation.org>,
	kernel-hardening@...ts.openwall.com, Kees Cook <kees@...ntu.com>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Matt Mackall <mpm@...enic.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Dan Rosenberg <drosenberg@...curity.com>,
	Theodore Tso <tytso@....edu>, Alan Cox <alan@...ux.intel.com>,
	Jesper Juhl <jj@...osbits.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [kernel-hardening] Re: [RFC PATCH 2/2] mm: restrict access to /proc/slabinfo

On Mon, 19 Sep 2011 15:02:34 CDT, Christoph Lameter said:
> On Mon, 19 Sep 2011, Valdis.Kletnieks@...edu wrote:
> 
> > On Mon, 19 Sep 2011 12:51:10 CDT, Christoph Lameter said:
> >
> > > IMHO a restriction of access to slab statistics is reasonable in a
> > > hardened environment. Make it dependent on CONFIG_SECURITY or some such
> > > thing?
> >
> > Probably need to invent a separate Kconfig variable - CONFIG_SECURITY
> > is probably a way-too-big hammer for this nail. I can see lots of systems
> > that want to enable that, but won't want to tighten access to slab.
> 
> There is already CONFIG_SECURITY_DMESG_RESTRICT. Generalize that setting
> to include all sorts of other kernel statistics?

The question becomes "What are the chances that a given site either will or
will not agree with using the same setting for all things aggregated under
the same option".   I could probably make a good case for a  flag
called CONFIG_SECURITY_INFOLEAK_RESTRICT that would be a switch
for "standard perms or root only" for all info-leaking files under /proc and
/sys.

The problem is that dmesg has *other* info-leakage issues - but it's not
internal kernel state, it's stuff like ipfilter messages and potentially
Selinux messages if auditd isn't running, and of late things like systemd and
crond like to stick crap in there as well.


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