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Date: Wed, 28 Sep 2011 14:46:14 -0700
From: Andrew Morton <akpm00@gmail.com>
To: Vasiliy Kulikov <segoon@openwall.com>
Cc: kernel-hardening@lists.openwall.com,
        Christoph Lameter <cl@linux-foundation.org>,
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        Linus Torvalds <torvalds@linux-foundation.org>,
        David Rientjes <rientjes@google.com>, Alan Cox <alan@linux.intel.com>,
        linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 2/2] mm: restrict access to /proc/meminfo
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On Tue, 27 Sep 2011 23:38:10 +0400
Vasiliy Kulikov <segoon@openwall.com> wrote:

> On Tue, Sep 27, 2011 at 21:56 +0400, Vasiliy Kulikov wrote:
> > /proc/meminfo stores information related to memory pages usage, which
> > may be used to monitor the number of objects in specific caches (and/or
> > the changes of these numbers).  This might reveal private information
> > similar to /proc/slabinfo infoleaks.  To remove the infoleak, just
> > restrict meminfo to root.  If it is used by unprivileged daemons,
> > meminfo permissions can be altered the same way as slabinfo:
> > 
> >     groupadd meminfo
> >     usermod -a -G meminfo $MONITOR_USER
> >     chmod g+r /proc/meminfo
> >     chgrp meminfo /proc/meminfo
> 
> Just to make it clear: since this patch breaks "free", I don't propose
> it anymore.

It will break top(1) too.  It isn't my favoritest-ever patch :)