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

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Message-Id: <200907211331.50196.arnd@arndb.de>
Date:	Tue, 21 Jul 2009 13:31:50 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Kyle McMartin <kyle@...artin.ca>
Cc:	Eric Paris <eparis@...hat.com>, 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)

On Tuesday 21 July 2009, Kyle McMartin wrote:
> 
> Why do we not add a personality flag for this? With that, at least you
> could require a harmless setuid wrapper for wine that just set the
> personality bits and dropped root.

I thought the MMAP_PAGE_ZERO personality bit was exactly what Brad
was using in his demonstration. We don't need to define a new bit,
just use the one that's there ;-).

Then again, setting personality flags does not require root permissions
normally, so it's not an extremely strong protection, unless you also
start requiring CAP_SYS_RAWIO for setting MMAP_PAGE_ZERO.

	Arnd <><
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