linux-kernel - Re: mmap_min_addr and your local LSM (ok, just SELinux)

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Message-ID: <20090730090645.GB1364@ucw.cz>
Date:	Thu, 30 Jul 2009 11:06:45 +0200
From:	Pavel Machek <pavel@....cz>
To:	Eric Paris <eparis@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, selinux@...ho.nsa.gov,
	sds@...ho.nsa.gov, jmorris@...ei.org, spender@...ecurity.net,
	dwalsh@...hat.com, cl@...ux-foundation.org, arjan@...radead.org,
	alan@...rguk.ukuu.org.uk
Subject: Re: mmap_min_addr and your local LSM (ok, just SELinux)

Hi!

> Brad Spengler recently pointed out that the SELinux decision on how to
> handle mmap_min_addr in some ways weakens system security vs on a system
> without SELinux (and in other ways can be stronger).  There is a trade
> off and a reason I did what I did but I would like ideas and discussion
> on how to get the best of both worlds.
> 
> With SELinux mapping the 0 page requires an SELinux policy permission,
> mmap_zero.  Without SELinux mapping the 0 page requires CAP_SYS_RAWIO.
> Note that CAP_SYS_RAWIO roughly translates to uid=0 since noone really
> does interesting things with capabilities.

I wonder if cap_sys_rawio is right capability for this..? rawio
normally grants you kernel-llevel access, so you don't want to give it
to wine. But maybe if it checked cap_sys_nice or some new capability,
we could reasonably give that to wine, and problem would be gone?

cap_sys_obscure_features ?

(I guess vm86 mode should fall under that, too :-)

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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