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

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Message-ID: <alpine.LFD.2.01.0906031032390.4880@localhost.localdomain>
Date:	Wed, 3 Jun 2009 10:35:10 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
cc:	Christoph Lameter <cl@...ux-foundation.org>,
	"Larry H." <research@...reption.com>, 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, Alan Cox wrote:
>
> One way you could approach this would be to write a security module for
> non SELINUX users - one that did one thing alone - decide whether the app
> being run was permitted to map the low 64K perhaps by checking the
> security label on the file.

Unnecessary. I really think that 99% of all people are perfectly fine with 
just the "mmap_min_addr" rule, and no more.

The rest could just use SElinux or set it to zero. It's not like allowing 
mmap's at NULL is a huge problem. Sure, it allows a certain kind of attack 
vector, but it's by no means an easy or common one - you need to already 
have gotten fairly good local access to take advantage of it.

		Linus
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