linux-kernel - Re: [kernel-hardening] Re: [PATCH 2/2] mm: restrict access to /proc/meminfo

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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: [kernel-hardening] 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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