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Subject: Re: [RFC PATCH 2/2] mm: restrict access to /proc/slabinfo
From: Dave Hansen <dave@linux.vnet.ibm.com>
To: Vasiliy Kulikov <segoon@openwall.com>
Cc: kernel-hardening@lists.openwall.com,
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Date: Wed, 14 Sep 2011 08:18:25 -0700
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On Wed, 2011-09-14 at 17:16 +0400, Vasiliy Kulikov wrote:
> > World readable slabinfo simplifies kernel developers' job of debugging
> > kernel bugs (e.g. memleaks), but I believe it does more harm than
> > benefits.  For most users 0444 slabinfo is an unreasonable attack vector.
> 
> Please tell if anybody has complains about the restriction - whether it
> forces someone besides kernel developers to do "chmod/chgrp".  But if
> someone want to debug the kernel, it shouldn't significantly influence
> on common users, especially it shouldn't create security issues. 

Ubuntu ships today with a /etc/init/mounted-proc.conf that does:

	chmod 0400 "${MOUNTPOINT}"/slabinfo

After cursing Kees's name a few times, I commented it out and it hasn't
bothered me again.  

I expect that the folks that really care about this (and their distros)
will probably have a similar mechanism.  I guess the sword cuts both
ways in this case: it obviously _works_ to have the distros do it, but
it was a one-time inconvenience for me to override that.

In other words, I dunno.  If we do this in the kernel, can we at least
do something like CONFIG_INSECURE to both track these kinds of things
and make it easy to get them out of a developer's way?

-- Dave