kernel-hardening - Re: Re: [PATCH] x86: make IDT read-only

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Message-ID: <CAGXu5jJNG4o+_-kk=A2AfSRwyQE0pgaQh7YpSjnD_fB-s7U+wA@mail.gmail.com>
Date: Tue, 9 Apr 2013 11:46:08 -0700
From: Kees Cook <keescook@...omium.org>
To: "H. Peter Anvin" <hpa@...or.com>
Cc: "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Ingo Molnar <mingo@...hat.com>, 
	LKML <linux-kernel@...r.kernel.org>, "x86@...nel.org" <x86@...nel.org>, 
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, Jeremy Fitzhardinge <jeremy@...p.org>, 
	Marcelo Tosatti <mtosatti@...hat.com>, Alex Shi <alex.shi@...el.com>, 
	Borislav Petkov <borislav.petkov@....com>, Alexander Duyck <alexander.h.duyck@...el.com>, 
	Frederic Weisbecker <fweisbec@...il.com>, Steven Rostedt <rostedt@...dmis.org>, 
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, 
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>, 
	"virtualization@...ts.linux-foundation.org" <virtualization@...ts.linux-foundation.org>, 
	Dan Rosenberg <drosenberg@...curity.com>, Julien Tinnes <jln@...gle.com>, 
	Will Drewry <wad@...omium.org>, Eric Northup <digitaleric@...gle.com>
Subject: Re: Re: [PATCH] x86: make IDT read-only

On Tue, Apr 9, 2013 at 11:39 AM, H. Peter Anvin <hpa@...or.com> wrote:
> On 04/09/2013 11:31 AM, Kees Cook wrote:
>>>> ...
>>>> 0xffff880001e00000-0xffff88001fe00000         480M     RW         PSE GLB NX pmd
>>>>
>>>
>>> That is the 1:1 memory map area...
>>
>> Meaning what?
>>
>> -Kees
>>
>
> That's the area in which we just map 1:1 to memory.  Anything allocated
> with e.g. kmalloc() ends up with those addresses.

Ah-ha! Yes, I see now when comparing the debug/kernel_page_tables
reports. It's just the High Kernel Mapping that we care about.
Addresses outside that range are less of a leak. Excellent, then GDT
may not be a problem. Whew.

Does the v2 IDT patch look okay, BTW?

-Kees

--
Kees Cook
Chrome OS Security

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