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 21:21:15 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
Cc:	Vasiliy Kulikov <segoon@...nwall.com>,
	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, 2011-09-19 at 20:51 +0300, Pekka Enberg wrote:
>> How is the attacker able to identify that we kmalloc()'d from ecryptfs or
>> VFS based on non-root /proc/slabinfo when the slab allocator itself does
>> not have that sort of information if you mix up the allocations? Isn't this
>> much stronger protection especially if you combine that with /proc/slabinfo
>> restriction?

On Mon, Sep 19, 2011 at 9:03 PM, Dave Hansen <dave@...ux.vnet.ibm.com> wrote:
> Mixing it up just adds noise.  It makes the attack somewhat more
> difficult, but it still leaves open the possibility that the attacker
> can filter out the noise somehow.

So that would mean the attacker has somewhat fine-grained control over
kernel memory allocations, no? Can they use /proc/meminfo to deduce
the same kind of information? Should we close that down too?

                         Pekka
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