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Date: Mon, 8 Aug 2016 11:00:40 -0700
From: Thomas Garnier <thgarnie@...gle.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Borislav Petkov <bp@...e.de>, "Rafael J. Wysocki" <rjw@...ysocki.net>,
Linux PM list <linux-pm@...r.kernel.org>, "the arch/x86 maintainers" <x86@...nel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Yinghai Lu <yinghai@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>,
Kees Cook <keescook@...omium.org>, Pavel Machek <pavel@....cz>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>, Borislav Petkov <bpetkov@...e.de>
Subject: Re: [Resend][PATCH] x86/power/64: Always create temporary identity
mapping correctly
On Mon, Aug 8, 2016 at 6:54 AM, Rafael J. Wysocki <rafael@...nel.org> wrote:
> On Mon, Aug 8, 2016 at 3:40 PM, Borislav Petkov <bp@...e.de> wrote:
>> On Mon, Aug 08, 2016 at 03:31:31PM +0200, Rafael J. Wysocki wrote:
>>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>>
>>> 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@...gle.com>
>>
>> Reported-by: Borislav Petkov <bp@...e.de>
>>
>>> Suggested-by: Yinghai Lu <yinghai@...nel.org>
>>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>> Acked-by: Yinghai Lu <yinghai@...nel.org>
>>> ---
>>>
>>> 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.
>> 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
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