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Date: Thu, 29 Sep 2011 21:25:31 +0400
From: Vasiliy Kulikov <segoon@openwall.com>
To: kernel-hardening@lists.openwall.com, Valdis.Kletnieks@vt.edu
Cc: David Rientjes <rientjes@google.com>, Christoph Lameter <cl@gentwo.org>,
        Pekka Enberg <penberg@kernel.org>, Matt Mackall <mpm@selenic.com>,
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        Linus Torvalds <torvalds@linux-foundation.org>,
        Alan Cox <alan@linux.intel.com>, linux-kernel@vger.kernel.org
Subject: Re: [kernel-hardening] Re: [PATCH 2/2] mm: restrict access to
 /proc/meminfo
Message-ID: <20110929172531.GA19290@albatros>
References: <20110927175453.GA3393@albatros>
 <20110927175642.GA3432@albatros>
 <20110927193810.GA5416@albatros>
 <alpine.DEB.2.00.1109271459180.13797@router.home>
 <alpine.DEB.2.00.1109271328151.24402@chino.kir.corp.google.com>
 <20110929161848.GA16348@albatros>
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On Thu, Sep 29, 2011 at 12:57 -0400, Valdis.Kletnieks@vt.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