linux-kernel - Re: Security fix for remapping of page 0 (was [PATCH] Change ZERO_SIZE

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Message-ID: <alpine.DEB.1.10.0906031537110.20254@gentwo.org>
Date:	Wed, 3 Jun 2009 15:42:13 -0400 (EDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Eric Paris <eparis@...isplace.org>
cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Larry H." <research@...reption.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, linux-mm@...ck.org,
	Rik van Riel <riel@...hat.com>, linux-kernel@...r.kernel.org,
	pageexec@...email.hu
Subject: Re: Security fix for remapping of page 0 (was [PATCH] Change 
 ZERO_SIZE_PTR to point at unmapped space)

On Wed, 3 Jun 2009, Eric Paris wrote:

> NAK  with SELinux on you now need both the SELinux mmap_zero
> permission and the CAP_SYS_RAWIO permission.  Previously you only
> needed one or the other, depending on which was the predominant
> LSM.....

CAP_SYS_RAWIO is checked so you only need to check for mmap_zero in
SELinux.

> Even if you want to argue that I have to take CAP_SYS_RAWIO in the
> SELinux case what about all the other places?  do_mremap?  do_brk?
> expand_downwards?

brk(0) would free up all the code? The others could be added.


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