Re: KASLR causes intermittent boot failures on some systems

[Jeff Moyer]

Kees Cook <keescook@xxxxxxxxxxxx> writes:

> On Mon, Apr 10, 2017 at 8:49 AM, Jeff Moyer <jmoyer@xxxxxxxxxx> wrote:
>> Kees Cook <keescook@xxxxxxxxxxxx> writes:
>>
>>> On Fri, Apr 7, 2017 at 7:41 AM, Jeff Moyer <jmoyer@xxxxxxxxxx> 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

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Cheers,
Jeff