linux-kernel - Re: PROBLEM: Resume form hibernate broken by setting NX on gap

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Date:	Fri, 10 Jun 2016 11:18:47 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Logan Gunthorpe <logang@...tatee.com>
Cc:	"Rafael J. Wysocki" <rafael@...nel.org>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	Ingo Molnar <mingo@...nel.org>, Ingo Molnar <mingo@...hat.com>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Brian Gerst <brgerst@...il.com>
Subject: Re: PROBLEM: Resume form hibernate broken by setting NX on gap

On Fri, Jun 10, 2016 at 11:16 AM, Logan Gunthorpe <logang@...tatee.com> wrote:
> Hey,
>
> On 10/06/16 12:09 PM, Kees Cook wrote:
>>> restore_code: ffff880157c3b000
>>> jump_addr: ffffffff81446be0
>>>
>>>
>>> diff --git a/arch/x86/power/hibernate_64.c b/arch/x86/power/hibernate_64.c
>>> index 009947d..6efedb7 100644
>>> --- a/arch/x86/power/hibernate_64.c
>>> +++ b/arch/x86/power/hibernate_64.c
>>> @@ -92,6 +92,9 @@ int swsusp_arch_resume(void)
>>>         memcpy(relocated_restore_code, &core_restore_code,
>>>                &restore_registers - &core_restore_code);
>>>
>>> +       pr_info("restore_code: %p\n", relocated_restore_code);
>>> +       pr_info("jump_addr: %lx\n", restore_jump_address);
>>> +
>>
>> Also interesting would be the "relocated_restore_code" address, as
>> well as a dump of /sys/kernel/debug/kernel_page_tables (from
>> CONFIG_X86_PTDUMP).
>
> Is that not what I printed? If not, can you give me a better hint as to

Oh, whoops, sorry, I saw "restore_code" in the pr_info and
"relocate_restore_code" in the memcpy and didn't scan the right thing
in the pr_info line. :)

> what you're looking for so I can spin another kernel? I'll also provide
> the kernel_page_tables once I do that.

Cool, thanks.

>
>> I'm baffled by the problem, but the best I can understand is the the
>> relocated_restore_code range isn't executable (which should be visible
>> from finding it in /sys/kernel/debug/kernel_page_tables), but I don't
>> see how to solve that since my original patch didn't work.
>
> Yeah this is definitely a baffling problem.

-Kees


-- 
Kees Cook
Chrome OS & Brillo Security