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Date: Mon, 8 Aug 2016 22:01:41 +0200
From: "Rafael J. Wysocki" <>
To: Thomas Garnier <>
Cc: "Rafael J. Wysocki" <>, Borislav Petkov <>, 
	"Rafael J. Wysocki" <>, Linux PM list <>, 
	"the arch/x86 maintainers" <>, Linux Kernel Mailing List <>, 
	Yinghai Lu <>, Thomas Gleixner <>, Ingo Molnar <>, 
	"H . Peter Anvin" <>, Kees Cook <>, Pavel Machek <>, 
	Kernel Hardening <>, Borislav Petkov <>
Subject: Re: [Resend][PATCH] x86/power/64: Always create temporary identity
 mapping correctly

On Mon, Aug 8, 2016 at 8:00 PM, Thomas Garnier <> wrote:
> On Mon, Aug 8, 2016 at 6:54 AM, Rafael J. Wysocki <> wrote:
>> On Mon, Aug 8, 2016 at 3:40 PM, Borislav Petkov <> wrote:
>>> On Mon, Aug 08, 2016 at 03:31:31PM +0200, Rafael J. Wysocki wrote:
>>>> From: Rafael J. Wysocki <>
>>>> The low-level resume-from-hibernation code on x86-64 uses
>>>> kernel_ident_mapping_init() to create the temoprary identity mapping,
>>>> but that function assumes that the offset between kernel virtual
>>>> addresses and physical addresses is aligned on the PGD level.
>>>> However, with a randomized identity mapping base, it may be aligned
>>>> on the PUD level and if that happens, the temporary identity mapping
>>>> created by set_up_temporary_mappings() will not reflect the actual
>>>> kernel identity mapping and the image restoration will fail as a
>>>> result (leading to a kernel panic most of the time).
>>>> To fix this problem, rework kernel_ident_mapping_init() to support
>>>> unaligned offsets between KVA and PA up to the PMD level and make
>>>> set_up_temporary_mappings() use it as approprtiate.
>>>> Reported-by: Thomas Garnier <>
>>> Reported-by: Borislav Petkov <>
>>>> Suggested-by: Yinghai Lu <>
>>>> Signed-off-by: Rafael J. Wysocki <>
>>>> Acked-by: Yinghai Lu <>
>>>> ---
>>>> This is sort of urgent, because hibernation doesn't work with KASLR on x86-64
>>>> in 4.8-rc1 AFAICS and this should make them work together again.
>>>> Unless anyone sees any problems with it, I'll queue it up for 4.8-rc2.
>>>> Thomas, would it be possible to test it with KASLR enabled, please?
> I tested it on my setup couple times. Worked well.


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