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

[Rafael J. Wysocki]

On Mon, Aug 8, 2016 at 3:40 PM, Borislav Petkov <bp@xxxxxxx> wrote:
> 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?

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 :)

Thanks!

Best,
Rafael