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

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Message-ID: <CAJcbSZEAyS6Lp=Cuz=-4yL39yz=Z_FpVuY2NiYjM=fchFtpTEg@mail.gmail.com>
Date:	Fri, 12 Aug 2016 09:03:52 -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>,
	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 4:14 AM, Rafael J. Wysocki <rafael@...nel.org> wrote:
> 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.

Borislav, let me know once you tested it and I will send a v2 with acked/tested.