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Date: Mon, 8 May 2017 07:09:45 -0700
From: Thomas Garnier <>
To: Daniel Gruss <>
Cc: David Gens <>, 
	kernel list <>, 
	Kernel Hardening <>,,, Michael Schwarz <>, 
	Richard Fellner <>, 
	"Kirill A. Shutemov" <>, Ingo Molnar <>,
Subject: Re: [RFC, PATCH] x86_64: KAISER - do not map
 kernel in user mode

On Mon, May 8, 2017 at 6:53 AM, Daniel Gruss
<> wrote:
> On 06.05.2017 10:38, Daniel Gruss wrote:
>> On 2017-05-06 06:02, David Gens wrote:
>>> Assuming that their patch indeed leaks per-cpu addresses.. it might not
>>> necessarily
>>> be required to change it.
>> I think we're not leaking them (unless we still have some bug in our
>> code).
> Just to correct my answer here as well: Although we experimented with fixed
> mappings for per-cpu addresses, the current patch does not incorporate this
> yet, so it indeed still leaks. However, it is not a severe problem. The
> mapping of the required (per-cpu) variables would be at a fixed location in
> the user CR3, instead of the ones that are used in the kernel.

Why do you think it should be at a fixed location in the user CR3? I
see that you just mirror the entries. You also mirror
__entry_text_start / __entry_text_end which is part of the binary so
will leak the base address of the kernel. Maybe I am missing


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