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Re: KASLR causes intermittent boot failures on some systems

From	Jeff Moyer <jmoyer@redhat.com>
Newsgroups	linux.kernel
Subject	Re: KASLR causes intermittent boot failures on some systems
Date	2017-04-10 21:20 +0200
Message-ID	<tuN0Z-4VF-1@gated-at.bofh.it> (permalink)
References	(1 earlier) <ttJC9-4GN-3@gated-at.bofh.it> <tuJTu-2D4-73@gated-at.bofh.it> <tuM4W-4ll-15@gated-at.bofh.it> <tuMeB-4oO-5@gated-at.bofh.it> <tuMRj-4S4-11@gated-at.bofh.it>
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Kees Cook <keescook@chromium.org> writes:

> On Mon, Apr 10, 2017 at 11:22 AM, Jeff Moyer <jmoyer@redhat.com> wrote:
>> Kees Cook <keescook@chromium.org> writes:
>>
>>> On Mon, Apr 10, 2017 at 8:49 AM, Jeff Moyer <jmoyer@redhat.com> wrote:
>>>> Kees Cook <keescook@chromium.org> writes:
>>>>
>>>>> 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.
>>>>>
>>>>> Just to rule out some of the stuff in the boot path, does booting with
>>>>> "nokaslr" solve this? (i.e. I want to figure out if this is from some
>>>>> of the rearrangements done that are exposed under that commit, or if
>>>>> it is genuinely the randomization that is killing the systems...)
>>>>
>>>> Adding "nokaslr" to the boot line does indeed make the problem go away.
>>>
>>> Are you booting with a memmap= flag?
>>
>> From my first email:
>>
>> [ 0.000000] Command line: BOOT_IMAGE=/vmlinuz-4.11.0-rc5+
>> root=/dev/mapper/rhel_intel--lizardhead--04-root ro memmap=192G!1024G
>> crashkernel=auto rd.lvm.lv=rhel_intel-lizardhead-04/root
>> rd.lvm.lv=rhel_intel-lizardhead-04/swap console=ttyS0,115200n81
>> LANG=en_US.UTF-8
>>
>> Did you not receive the attachments?
>
> I see it now, thanks!
>
> The memmap parsing was added in -rc1 (f28442497b5ca), so I'd expect
> that to be handled. Hmmm.

I can also reproduce this on a system with real persistent memory, which
does not require the memmap parameter.

Cheers,
Jeff

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Thread

Re: KASLR causes intermittent boot failures on some systems Jeff Moyer <jmoyer@redhat.com> - 2017-04-10 18:00 +0200
  Re: KASLR causes intermittent boot failures on some systems Kees Cook <keescook@chromium.org> - 2017-04-10 20:20 +0200
    Re: KASLR causes intermittent boot failures on some systems Jeff Moyer <jmoyer@redhat.com> - 2017-04-10 20:30 +0200
      Re: KASLR causes intermittent boot failures on some systems Kees Cook <keescook@chromium.org> - 2017-04-10 21:10 +0200
        Re: KASLR causes intermittent boot failures on some systems Jeff Moyer <jmoyer@redhat.com> - 2017-04-10 21:20 +0200

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