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

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Date:	Wed, 14 Sep 2011 08:18:25 -0700
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Vasiliy Kulikov <segoon@...nwall.com>
Cc:	kernel-hardening@...ts.openwall.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.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: [RFC PATCH 2/2] mm: restrict access to /proc/slabinfo

On Wed, 2011-09-14 at 17:16 +0400, Vasiliy Kulikov wrote:
> > World readable slabinfo simplifies kernel developers' job of debugging
> > kernel bugs (e.g. memleaks), but I believe it does more harm than
> > benefits.  For most users 0444 slabinfo is an unreasonable attack vector.
> 
> Please tell if anybody has complains about the restriction - whether it
> forces someone besides kernel developers to do "chmod/chgrp".  But if
> someone want to debug the kernel, it shouldn't significantly influence
> on common users, especially it shouldn't create security issues. 

Ubuntu ships today with a /etc/init/mounted-proc.conf that does:

	chmod 0400 "${MOUNTPOINT}"/slabinfo

After cursing Kees's name a few times, I commented it out and it hasn't
bothered me again.  

I expect that the folks that really care about this (and their distros)
will probably have a similar mechanism.  I guess the sword cuts both
ways in this case: it obviously _works_ to have the distros do it, but
it was a one-time inconvenience for me to override that.

In other words, I dunno.  If we do this in the kernel, can we at least
do something like CONFIG_INSECURE to both track these kinds of things
and make it easy to get them out of a developer's way?

-- Dave

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