[PATCH 1/3] mm: security: introduce the init_allocations=1 boot option

Michal Hocko mhocko at kernel.org
Tue Apr 23 08:31:48 UTC 2019

On Thu 18-04-19 09:35:32, Dave Hansen wrote:
> On 4/18/19 8:42 AM, Alexander Potapenko wrote:
> > This option adds the possibility to initialize newly allocated pages and
> > heap objects with zeroes. This is needed to prevent possible information
> > leaks and make the control-flow bugs that depend on uninitialized values
> > more deterministic.
> Isn't it better to do this at free time rather than allocation time?  If
> doing it at free, you can't even have information leaks for pages that
> are in the allocator.

I would tend to agree here. Free path is usually less performance sensitive
than the allocation. Those really hot paths tend to defer the work.

I am also worried that an opt-out gfp flag would tend to be used
incorrectly as the history has shown for others - e.g. __GFP_TEMPORARY.
So I would rather see this robust without a fine tuning unless there is
real use case that would suffer from this and we can think of a
background scrubbing or something similar.

Michal Hocko

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