linux-hardening - Re: [PATCH] bcachefs: Refactor bkey

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Date: Wed, 18 Oct 2023 18:04:07 -0400
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Kees Cook <keescook@...omium.org>
Cc: Brian Foster <bfoster@...hat.com>, linux-bcachefs@...r.kernel.org,
	kernel test robot <lkp@...el.com>, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] bcachefs: Refactor bkey_i to use a flexible array

On Fri, Oct 13, 2023 at 04:44:21PM -0700, Kees Cook wrote:
> On Fri, Oct 13, 2023 at 07:26:11AM -0400, Brian Foster wrote:
> > Hi Kees,
> > 
> > I'm curious if this is something that could be buried in bch_val given
> > it's already kind of a fake structure..? If not, my only nitty comment
> 
> I was thinking it would be best to keep the flexible array has "high" in
> the struct as possible, as in the future more refactoring will be needed
> to avoid having flex arrays overlap with other members in composite
> structures. So instead of pushing into bch_val, I left it at the highest
> level possible, bch_i, as that's the struct being used by the memcpy().

I agree with Brian here - I'd like this buried in bch_val, if possible.

I also went with unsafe_memcpy() for now - that's now in my for-next
tree. I'm not seeing any advantage of DECLARE_FLEX_ARRAY over that -
perhaps later if we could use __counted_by that would make more sense.