Re: [PATCH v2 0/2] Lock and Pointer guards

Linus Torvalds
2023-06-06T15:46:20Z

On Tue, Jun 6, 2023 at 8:31 AM Kees Cook <keescook@chromium.org> wrote:
>
> nit: Linus's example was "(void *)8" (instead of 1) because we've had
> issues in the past with alignment warnings on archs that are sensitive
> to it. (e.g. see the __is_constexpr() macro which is doing NULL/!NULL
> comparisons.)

Note that I don't think we ever saw such a warning, it was just a
theoretical observation that depending on type, the compiler might
warn about known mis-aligned pointer bits.

So I'm not sure the 1-vs-8 actually matters. We do other things that
assume that low bits in a pointer are retained and valid, even if in
theory the C type system might have issues with it.

But maybe I mis-remember - if you did get an actual warning, maybe we
should document that warning just to keep the memory alive.

Linus