[Query] ARM64 kaslr support - randomness, seeding and kdump

Bhupesh Sharma
2018-03-16T09:35:10Z

On Wed, Mar 14, 2018 at 11:54 PM, Mark Rutland <mark.rutland@arm.com> wrote:
> On Wed, Mar 14, 2018 at 11:10:53AM +0900, AKASHI Takahiro wrote:
>> If kaslr-seed has a critical value in terms of security, is kexec-tools
>> a right place? It is exposed to user space albeit for a short time of period.
>
> The kernel zeroes the seed in the DT at boot time, so the current seed
> isn't visible to userspace.
>
> If kexec-tools generates a seed, and inserts it into the DTB that it
> loads, this is only visible to kexec tools or other applications which
> can inspect its memory, so I don't think this is much of a concern.
> Anything with such privilege can presumably kexec() to arbitrary code
> anyhow.
>
> The next kernel will then zero its seed in the DT at boot time, so
> similarly this won't be visible to userspace on the new kernel.
>
> FWIW, having kexec tools generate a seed for the kexec_load() case makes
> sense to me.

Fair enough. I will try to take a stab at the same and come back with
my findings on this thread.

Thanks,
Bhupesh