linux-kernel - Re: [PATCH v1] x86/power/64: Restore processor state before using per-cpu variables

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Message-ID: <CAJZ5v0hC28BMqgurck0oiQGxf=XhYwseiVs+DeLdv9wKHFCa7w@mail.gmail.com>
Date:	Fri, 12 Aug 2016 13:14:49 +0200
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Borislav Petkov <bp@...e.de>
Cc:	Thomas Garnier <thgarnie@...gle.com>,
	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Linux PM <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>,
	Kernel Hardening <kernel-hardening@...ts.openwall.com>,
	Jiri Kosina <jikos@...nel.org>, Yinghai Lu <yinghai@...nel.org>
Subject: Re: [PATCH v1] x86/power/64: Restore processor state before using
 per-cpu variables

On Fri, Aug 12, 2016 at 7:49 AM, Borislav Petkov <bp@...e.de> wrote:
> On Thu, Aug 11, 2016 at 02:49:29PM -0700, Thomas Garnier wrote:
>> Restore the processor state before calling any other function to ensure
>> per-cpu variables can be used with KASLR memory randomization.
>>
>> Tracing functions use per-cpu variables (gs based) and one was called
>> just before restoring the processor state fully. It resulted in a double
>> fault when both the tracing & the exception handler functions tried to
>> use a per-cpu variable.
>>
>> Signed-off-by: Thomas Garnier <thgarnie@...gle.com>
>> ---
>> Based on next-20160808
>
> Ok, I believe before I test this, I need to apply another patch from
> Rafael. I think it is the "Always create temporary identity mapping
> correctly" thing.
>
> Yes, no?

Yes.

> Rafael, can you please apply everything on a test branch for us to run?

You can simply test my linux-next branch:

git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git \
linux-next

That's 4.8-rc1 plus 3 fixes on top of it.

Thanks,
Rafael