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Date:   Tue, 19 Apr 2022 19:42:42 -0700
From:   Kees Cook <keescook@chromium.org>
To:     joao@overdrivepizza.com
Cc:     linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org,
        peterz@infradead.org, jpoimboe@redhat.com,
        andrew.cooper3@citrix.com, samitolvanen@google.com,
        mark.rutland@arm.com, hjl.tools@gmail.com,
        alyssa.milburn@linux.intel.com, ndesaulniers@google.com,
        gabriel.gomes@linux.intel.com, rick.p.edgecombe@intel.com
Subject: Re: [RFC PATCH 00/11] Kernel FineIBT Support
Message-ID: <202204191937.2720E7E@keescook>
References: <20220420004241.2093-1-joao@overdrivepizza.com>
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In-Reply-To: <20220420004241.2093-1-joao@overdrivepizza.com>
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Hi!

On Tue, Apr 19, 2022 at 05:42:30PM -0700, joao@overdrivepizza.com wrote:
> I'm considering detaching the prototype fixes from this series and reworking
> them to submit actual fixes (patches 10 and 11). Any specific suggestions for
> these specific patches? Maybe you want to take a look and help in co-authorship
> as we did with the void*-in-x86-crypto patches in the past? I guess these are
> useful for whatever CFI scheme is in place.

Yeah, if 10 and 11 are general prototype-based fixes, let's get them in.
I would expect regular CFI and kCFI to trip over those too. I'll comment
on those patches directly.

> Any other major concerns, ideas, or suggestions? :)

I think it'd be good to get kCFI landed in Clang first (since it is
effectively architecture agnostic), and then get FineIBT landed. But
that doesn't mean we can't be working on the kernel side of things at
the same time.

And just thinking generally, for other architecture-specific stuff,
I do wonder what an arm64 PAC-based CFI might look like. I prefer things
be hard-coded as kCFI is doing, but it'd be nice to be able to directly
measure performance and size overheads comparing the various methods.

-- 
Kees Cook