Re: [PATCH] hwmon: (w83791d) Convert macros to functions to avoid TOCTOU

[Guenter Roeck]

On Wed, Dec 03, 2025 at 02:01:05AM +0800, Gui-Dong Han wrote:
> The macro FAN_FROM_REG evaluates its arguments multiple times. When used
> in lockless contexts involving shared driver data, this leads to
> Time-of-Check to Time-of-Use (TOCTOU) race conditions, potentially
> causing divide-by-zero errors.
> 
> Convert the macro to a static function. This guarantees that arguments
> are evaluated only once (pass-by-value), preventing the race
> conditions.
> 
> Additionally, in store_fan_div, move the calculation of the minimum
> limit inside the update lock. This ensures that the read-modify-write
> sequence operates on consistent data.
> 
> Adhere to the principle of minimal changes by only converting macros
> that evaluate arguments multiple times and are used in lockless
> contexts.
> 
> Link: https://lore.kernel.org/all/CALbr=LYJ_ehtp53HXEVkSpYoub+XYSTU8Rg=o1xxMJ8=5z8B-g@xxxxxxxxxxxxxx/
> Fixes: 9873964d6eb2 ("[PATCH] HWMON: w83791d: New hardware monitoring driver for the Winbond W83791D") 
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Gui-Dong Han <hanguidong02@xxxxxxxxx>

Applied.

Thanks,
Guenter