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

On Sun, Jul 25, 2021 at 8:08 PM Marc Zyngier maz@kernel.org 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@kernel.org Cc: stable@vger.kernel.org Cc: Amelie Delaunay amelie.delaunay@foss.st.com Cc: Linus Walleij linus.walleij@linaro.org Cc: Maxime Coquelin mcoquelin.stm32@gmail.com Cc: Alexandre Torgue alexandre.torgue@foss.st.com

Patch applied!

Yours, Linus Walleij