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

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Date:	Mon, 8 Aug 2016 22:01:41 +0200
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Thomas Garnier <thgarnie@...gle.com>
Cc:	"Rafael J. Wysocki" <rafael@...nel.org>,
	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 8:00 PM, Thomas Garnier <thgarnie@...gle.com> wrote:
> 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.

Thanks!