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Date: Tue, 20 Feb 2018 19:16:38 +0200
From: Igor Stoppa <>
To: Laura Abbott <>, Kees Cook <>
CC: Boris Lukashev <>, Christopher Lameter
	<>, Matthew Wilcox <>, Jann Horn
	<>, Jerome Glisse <>, Michal Hocko
	<>, Christoph Hellwig <>,
	linux-security-module <>, Linux-MM
	<>, kernel list <>, "Kernel
 Hardening" <>
Subject: Re: [PATCH 4/6] Protectable Memory

On 13/02/18 20:10, Laura Abbott wrote:
> On 02/13/2018 07:20 AM, Igor Stoppa wrote:
>> Why alterations of page properties are not considered a risk and the physmap is?
>> And how would it be easier (i suppose) to attack the latter?
> Alterations are certainly a risk but with the physmap the
> mapping is already there. Find the address and you have
> access vs. needing to actually modify the properties
> then do the access. I could also be complete off base
> on my threat model here so please correct me if I'm
> wrong.

It's difficult for me to comment on this without knowing *how* the
attack would be performed, in your model.

Ex: my expectation is that the attacked has R/W access to kernel data
and has knowledge of the location of static variables.

This is not just a guess, but a real-life scenario, found in attacks
that, among other things, are capable of disabling SELinux, to proceed
toward gaining full root capability.

At that point, I think that variables which are allocated dynamically,
in vmalloc address space, are harder to locate, because of the virtual
mapping and the randomness of the address chosen (this I have not
confirmed yet, but I suppose there is some randomness in picking the
address to assign to a certain allocation request to vmalloc, otherwise,
it could be added).

> I think your other summaries are good points though
> and should go in the cover letter.

Ok, I'm just afraid it risks becoming a lengthy dissertation :-)


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