Re: [Resend][PATCH] x86/power/64: Always create temporary identity mapping correctly

[Borislav Petkov]

On Mon, Aug 08, 2016 at 03:31:31PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> 
> 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 <thgarnie@xxxxxxxxxx>

Reported-by: Borislav Petkov <bp@xxxxxxx>

> Suggested-by: Yinghai Lu <yinghai@xxxxxxxxxx>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> Acked-by: Yinghai Lu <yinghai@xxxxxxxxxx>
> ---
> 
> 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?

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

Thanks.

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