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 21:28:21 +0400 [thread overview]
Message-ID: <20110929172821.GA19601@albatros> (raw)
In-Reply-To: <20110929161848.GA16348@albatros>
On Thu, Sep 29, 2011 at 20:18 +0400, Vasiliy Kulikov wrote:
> 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.
s/filled_obj_size_sum/old/ of course.
> 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 17:29 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
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 [this message]
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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