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 17:30:49 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Vasiliy Kulikov <segoon@...nwall.com>
Cc:	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 Wed, Sep 14, 2011 at 12:27 -0700, Kees Cook wrote:
>> On Sat, Sep 10, 2011 at 08:41:34PM +0400, Vasiliy Kulikov wrote:
>> > Historically /proc/slabinfo has 0444 permissions and is accessible to
>> > the world.  slabinfo contains rather private information related both to
>> > the kernel and userspace tasks.  Depending on the situation, it might
>> > reveal either private information per se or information useful to make
>> > another targeted attack.  Some examples of what can be learned by
>> > reading/watching for /proc/slabinfo entries:
>> > ...
>> > 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.
>> >
>> > Signed-off-by: Vasiliy Kulikov <segoon@...nwall.com>

On Sun, Sep 18, 2011 at 8:05 PM, Vasiliy Kulikov <segoon@...nwall.com> wrote:
>> Haven't had any mass complaints about the 0400 in Ubuntu (sorry Dave!), so
>> I'm obviously for it.
>>
>> Reviewed-by: Kees Cook <kees@...ntu.com>
>
> Looks like the members of the previous slabinfo discussion don't object
> against the patch now and it got two other Reviewed-by responses.  Can
> you merge it as-is or should I probably convince someone else?

We discussed this in March (google for 'Make /proc/slabinfo 0400') and
concluded that it's not worth it doesn't really protect from anything
and causes harm to developers.

                        Pekka
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