From: Vasiliy Kulikov <segoon@openwall.com>
To: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@gentwo.org>,
kernel-hardening@lists.openwall.com,
Pekka Enberg <penberg@kernel.org>, Matt Mackall <mpm@selenic.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, Kees Cook <kees@ubuntu.com>,
Dave Hansen <dave@linux.vnet.ibm.com>,
Valdis.Kletnieks@vt.edu,
Linus Torvalds <torvalds@linux-foundation.org>,
Alan Cox <alan@linux.intel.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] mm: restrict access to /proc/meminfo
Date: Thu, 29 Sep 2011 20:18:48 +0400 [thread overview]
Message-ID: <20110929161848.GA16348@albatros> (raw)
In-Reply-To: <alpine.DEB.2.00.1109271328151.24402@chino.kir.corp.google.com>
On Tue, Sep 27, 2011 at 13:33 -0700, David Rientjes wrote:
> I'd much rather just convert everything to use MB rather than KB so you
> can't determine things at a page level. I think that gets us much closer
> to what the patch is intending to restrict. But I also expect some
> breakage from things that just expect meminfo to be in KB units without
> parsing what the kernel is exporting.
I'm not convinced with rounding the information to MBs. The attacker
still may fill slabs with new objects to trigger new slab pages
allocations. He will be able to see when this MB-granularity barrier is
overrun thus seeing how many kbs there were before:
old = new - filled_obj_size_sum
As `new' is just increased, it means it is known with KB granularity,
not MB. By counting used slab objects he learns filled_obj_size_sum.
So, rounding gives us nothing, but obscurity.
Thanks,
--
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments
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next prev parent reply other threads:[~2011-09-29 16:19 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-27 17:54 [PATCH 1/2] mm: restrict access to slab files under procfs and sysfs Vasiliy Kulikov
2011-09-27 17:56 ` [PATCH 2/2] mm: restrict access to /proc/meminfo Vasiliy Kulikov
2011-09-27 18:27 ` David Rientjes
2011-09-27 19:14 ` Vasiliy Kulikov
2011-09-27 19:38 ` Vasiliy Kulikov
2011-09-27 20:03 ` Christoph Lameter
2011-09-27 20:33 ` David Rientjes
2011-09-27 20:47 ` Christoph Lameter
2011-09-28 20:31 ` Dave Hansen
2011-09-28 20:52 ` Alan Cox
2011-09-29 0:43 ` Valdis.Kletnieks
2011-09-29 14:11 ` Christoph Lameter
2011-09-29 16:18 ` Vasiliy Kulikov [this message]
2011-09-29 16:30 ` Dave Hansen
2011-09-29 16:43 ` [kernel-hardening] " Vasiliy Kulikov
2011-09-29 16:57 ` Valdis.Kletnieks
2011-09-29 17:25 ` [kernel-hardening] " Vasiliy Kulikov
2011-09-29 17:28 ` Vasiliy Kulikov
2011-09-28 21:46 ` Andrew Morton
2011-09-30 19:53 ` Vasiliy Kulikov
2011-09-30 20:03 ` Andrew Morton
2011-09-30 20:12 ` Vasiliy Kulikov
2011-09-30 20:15 ` Dave Hansen
2011-09-27 18:08 ` [PATCH 1/2] mm: restrict access to slab files under procfs and sysfs Christoph Lameter
2011-09-27 19:16 ` Vasiliy Kulikov
2011-09-27 19:35 ` Christoph Lameter
2011-09-27 18:21 ` David Rientjes
2011-09-27 20:00 ` Pekka Enberg
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