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Message-ID: <20110929172531.GA19290@albatros>
Date: Thu, 29 Sep 2011 21:25:31 +0400
From: Vasiliy Kulikov <segoon@...nwall.com>
To: kernel-hardening@...ts.openwall.com, Valdis.Kletnieks@...edu
Cc: David Rientjes <rientjes@...gle.com>, Christoph Lameter <cl@...two.org>,
	Pekka Enberg <penberg@...nel.org>, Matt Mackall <mpm@...enic.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	Kees Cook <kees@...ntu.com>, Dave Hansen <dave@...ux.vnet.ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alan Cox <alan@...ux.intel.com>, linux-kernel@...r.kernel.org
Subject: Re: Re: [PATCH 2/2] mm: restrict access to
 /proc/meminfo

On Thu, Sep 29, 2011 at 12:57 -0400, Valdis.Kletnieks@...edu wrote:
> But now he has to fly blind for the next 30 because the numbers will display
> exactly the same, and he can't correct for somebody else allocating one so he
> needs to only allocate 29...

You're still talking about "slabinfo", which is already restricted.


And meminfo can be still learned with the same race window (ala seq lock):

    prepare_stuff();
    fill_slabs(); // Here we know counters with KB granularity
    while (number_is_not_ok()) {
        prepare_stuff();
        fill_slabs();
    }
    do_exploit();


Thanks,

-- 
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments

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