Re: KASLR causes intermittent boot failures on some systems

[Jeff Moyer]

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.

Cheers,
Jeff