linux-kernel - Re: KASLR causes intermittent boot failures on some systems

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Message-ID: <CAJcbSZH5BrK_ip8DxQd5vxrtckcbZ8vaQhf5h9qsQ+tzakhvKw@mail.gmail.com>
Date:   Wed, 19 Apr 2017 07:56:36 -0700
From:   Thomas Garnier <thgarnie@...gle.com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Baoquan He <bhe@...hat.com>, Jeff Moyer <jmoyer@...hat.com>,
        Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>
Subject: Re: KASLR causes intermittent boot failures on some systems

On Wed, Apr 19, 2017 at 7:34 AM, Dan Williams <dan.j.williams@...el.com> wrote:
> Does the randomization ever cross a pgd boundary?

Yes, it can cross a pgd boundary. The original physical memory mapping
might as well but you would need almost 550Gb of memory.

>
> These crashes look very similar to the crashes caused by
> arch_add_memory() racing itself. This issue was fixed in:
>
>     f931ab479dd2 mm: fix devm_memremap_pages crash, use
> mem_hotplug_{begin, done}
>
> ...but that only helps users that call mem_hotplug_begin() to prevent
> concurrent updates.
>

It could be related to page table changes done concurrently or just
done with certain expectations.


-- 
Thomas