Re: [PATCH] pinctrl: stmfx: Fix hazardous u8[] to unsigned long cast

[Linus Walleij]

On Sun, Jul 25, 2021 at 8:08 PM Marc Zyngier <maz@xxxxxxxxxx> wrote:

> Casting a small array of u8 to an unsigned long is *never* OK:
>
> - it does funny thing when the array size is less than that of a long,
>   as it accesses random places in the stack
> - it makes everything even more fun with a BE kernel
>
> Fix this by building the unsigned long used as a bitmap byte by byte,
> in a way that works across endianess and has no undefined behaviours.
>
> An extra BUILD_BUG_ON() catches the unlikely case where the array
> would be larger than a single unsigned long.
>
> Fixes: 1490d9f841b1 ("pinctrl: Add STMFX GPIO expander Pinctrl/GPIO driver")
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Cc: Amelie Delaunay <amelie.delaunay@xxxxxxxxxxx>
> Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
> Cc: Maxime Coquelin <mcoquelin.stm32@xxxxxxxxx>
> Cc: Alexandre Torgue <alexandre.torgue@xxxxxxxxxxx>

Patch applied!

Yours,
Linus Walleij