Re: [PATCH v8 3/8] Use atomic_t for ucounts reference counting

[Kees Cook]

On Mon, Mar 15, 2021 at 03:19:17PM -0700, Linus Torvalds wrote:
> It just saturates, and doesn't have the "don't do this" case, which
> the ucounts case *DOES* have.

Right -- I saw that when digging through the thread. I'm honestly
curious, though, why did the 0-day bot find a boot crash? (I can't
imagine ucounts wrapped in 0.4 seconds.) So it looked like an
increment-from-zero case, which seems like it would be a bug?

> I know you are attached to refcounts, but really: they are not only
> more expensive, THEY LITERALLY DO THE WRONG THING.

Heh, right -- I'm not arguing that refcount_t MUST be used, I just didn't
see the code path that made them unsuitable: hitting INT_MAX - 128 seems
very hard to do. Anyway, I'll go study it more to try to understand what
I'm missing.

-- 
Kees Cook