linux-hardening - Re: KFENCE: included in x86 defconfig?

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Date: Wed, 7 Feb 2024 20:04:44 +0100
From: Borislav Petkov <bp@...en8.de>
To: Matthieu Baerts <matttbe@...nel.org>
Cc: Marco Elver <elver@...gle.com>, Alexander Potapenko <glider@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com,
	Netdev <netdev@...r.kernel.org>, Jakub Kicinski <kuba@...nel.org>,
	linux-hardening@...r.kernel.org, Kees Cook <keescook@...omium.org>,
	the arch/x86 maintainers <x86@...nel.org>
Subject: Re: KFENCE: included in x86 defconfig?

On Wed, Feb 07, 2024 at 07:35:53PM +0100, Matthieu Baerts wrote:
> Sorry, I'm sure I understand your suggestion: do you mean not including
> KFENCE in hardening.config either, but in another one?
> 
> For the networking tests, we are already merging .config files, e.g. the
> debug.config one. We are not pushing to have KFENCE in x86 defconfig, it
> can be elsewhere, and we don't mind merging other .config files if they
> are maintained.

Well, depends on where should KFENCE be enabled? Do you want people to
run their tests with it too, or only the networking tests? If so, then
hardening.config probably makes sense. 

Judging by what Documentation/dev-tools/kfence.rst says:

"KFENCE is designed to be enabled in production kernels, and has near zero
performance overhead."

this reads like it should be enabled *everywhere* - not only in some
hardening config.

But then again I've never played with it so I don't really know.

If only the networking tests should enable it, then it should be a local
.config snippet which is not part of the kernel.

Makes more sense?

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette