Re: [PATCH] Prefer kASLR over Hibernation

From: Kees Cook
Date: Mon Apr 11 2016 - 14:47:23 EST

On Mon, Apr 11, 2016 at 11:21 AM, Geert Uytterhoeven
<geert@xxxxxxxxxxxxxx> wrote:
> On Mon, Apr 11, 2016 at 8:03 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>> On Mon, Apr 11, 2016 at 1:00 AM, James Morse <james.morse@xxxxxxx> wrote:
>>> On 06/04/16 20:44, Kees Cook wrote:
>>>> When building with both CONFIG_HIBERNATION and CONFIG_RANDOMIZE_BASE,
>>>> one or the other must be chosen at boot-time. Until now, hibernation
>>>> was selected when no choice was made on the command line.
>>>> To make the security benefits of kASLR more widely available to end
>>>> users (since the use of hibernation is becoming more rare and kASLR,
>>>> already available on x86, will be available on arm64 and MIPS soon),
>>>> this changes the default to preferring kASLR over hibernation. Users
>>>> wanting hibernation can turn off kASLR by adding "nokaslr" to the kernel
>>>> command line.
>>> While hibernate isn't yet merged for arm64, it does work with kASLR in v4.6-rc*,
>>> it would be a shame to have to choose at boot time, (but that's my problem to
>>> fix if/when its merged).
>> Ah, interesting, so they work together on arm64? (i.e. you've actually
>> tested a boot loader that provides the seed for kASLR to operate?)
> Probably the PS3 people can provide us with a good tool to generate a
> seed that makes hibernation work all the time ;-)



Kees Cook
Chrome OS & Brillo Security