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Date: Mon, 8 Aug 2016 15:54:48 +0200
From: "Rafael J. Wysocki" <>
To: Borislav Petkov <>
Cc: "Rafael J. Wysocki" <>, Linux PM list <>, 
	Thomas Garnier <>, "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 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?
> Is that the only patch which needs to be tested? Ontop of which tree?

That should be the only one on top of plain 4.8-rc1.

If it doesn't help, we need more work to do. :-)

> CONFIG_RANDOMIZE_MEMORY blew up s2d on my laptop here so I'll run it
> once I have the required info from you :)



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