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Message-ID: <20180717071223.GA29533@gmail.com>
Date: Tue, 17 Jul 2018 09:12:23 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Alexander Popov <alex.popov@...ux.com>
Cc: Kees Cook <keescook@...omium.org>,
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Subject: Re: [PATCH v14 0/6] Introduce the STACKLEAK feature and a test for it
* Alexander Popov <alex.popov@...ux.com> wrote:
> > ... which would keep it initialized and wouldn't be racy, right?
>
> No, this will break the poison search logic.
Ok.
> > I.e. only the most expensive part of the function, the scanning, would be
> > turned off via the sysctl. I submit that this will avoid all measurable
> > aspects of the 1% kbuild performance overhead.
>
> Yes, I've made an experiment - skipping stackleak_erase() cuts almost all
> performance penalty of the feature.
Ok, that's good!
> > A more involved approach can be done in the future if warranted, and the feature
> > could be disabled/enabled more thoroughly - but the runtime sysctl would be
> > acceptable for me for now, as a first iteration.
>
> Thanks, I see your point.
> I'll return with an additional patch introducing sysctl knob + static key for
> one-time disabling of stack erasing.
Thank you!
I'll have a final review of the patch but I guess it will be fine, so if that's
the only change then you can also include my:
Acked-by: Ingo Molnar <mingo@...nel.org>
... to not hold the patch up for v4.19, and this can go upstream via Kees's tree?
Ingo
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