Re: KASLR causes intermittent boot failures on some systems

From: Jeff Moyer <jmoyer@redhat.com>
To: Thomas Garnier <thgarnie@google.com>
Cc: Ingo Molnar <mingo@kernel.org>, Baoquan He <bhe@redhat.com>,
	Dan Williams <dan.j.williams@intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-nvdimm@ml01.01.org, Kees Cook <keescook@chromium.org>
Subject: Re: KASLR causes intermittent boot failures on some systems
Date: Fri, 07 Apr 2017 10:51:21 -0400	[thread overview]
Message-ID: <x49o9w86zkm.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <CAJcbSZGWLC+QCk8GuBneL2ho2eXfyKdVrP4uUgvbSv-GoXissg@mail.gmail.com> (Thomas Garnier's message of "Fri, 7 Apr 2017 07:49:43 -0700")

Thomas Garnier <thgarnie@google.com> writes:

> CCing Kees for information.
>
> On Fri, Apr 7, 2017 at 7:41 AM, Jeff Moyer <jmoyer@redhat.com> wrote:
>> Hi,
>>
>> commit 021182e52fe01 ("x86/mm: Enable KASLR for physical mapping memory
>> regions") causes some of my systems with persistent memory (whether real
>> or emulated) to fail to boot with a couple of different crash
>> signatures.  The first signature is a NMI watchdog lockup of all but 1
>> cpu, which causes much difficulty in extracting useful information from
>> the console.  The second variant is an invalid paging request, listed
>> below.
>>
>> On some systems, I haven't hit this problem at all.  Other systems
>> experience a failed boot maybe 20-30% of the time.  To reproduce it,
>> configure some emulated pmem on your system.  You can find directions
>> for that here: https://nvdimm.wiki.kernel.org/
>
> Did you try to repro on qemu?

I did not.

-Jeff