Re: KASLR causes intermittent boot failures on some systems

[Kees Cook]

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?

-Kees

-- 
Kees Cook
Pixel Security