Re: [PATCH] leds: leds-mt6323: Adjust return/parameter types in wled get/set callbacks

[Lee Jones <lee@kernel.org>]

On Thu, 22 Jun 2023, Nathan Chancellor wrote:

> Clang's kernel Control Flow Integrity (kCFI) is a compiler-based
> security mitigation that ensures the target of an indirect function call
> matches the expected type of the call and trapping if they do not match
> exactly. The warning -Wincompatible-function-pointer-types-strict aims
> to catch these issues at compile time, which reveals:
> 
>  drivers/leds/leds-mt6323.c:598:49: error: incompatible function pointer types assigning to 'int (*)(struct led_classdev *, enum led_brightness)' from 'int (struct led_classdev *, unsigned int)' [-Werror,-Wincompatible-function-pointer-types-strict]
>    598 |                         leds->led[reg]->cdev.brightness_set_blocking =
>        |                                                                      ^
>    599 |                                                 mt6323_wled_set_brightness;
>        |                                                 ~~~~~~~~~~~~~~~~~~~~~~~~~~
>  drivers/leds/leds-mt6323.c:600:40: error: incompatible function pointer types assigning to 'enum led_brightness (*)(struct led_classdev *)' from 'unsigned int (struct led_classdev *)' [-Werror,-Wincompatible-function-pointer-types-strict]
>    600 |                         leds->led[reg]->cdev.brightness_get =
>        |                                                             ^
>    601 |                                                 mt6323_get_wled_brightness;
>        |                                                 ~~~~~~~~~~~~~~~~~~~~~~~~~~
>  2 errors generated.
> 
> While 'unsigned int' is ABI compatible with 'enum led_brightness' (hence
> no warning from -Wincompatible-function-pointer-types) and the callers
> of these callbacks use/pass the values as 'unsigned int', the mismatch
> between the prototype and the called function will trip kCFI at runtime.
> 
> Change the types in the implementations to match the prototypes, clearing
> up the warning and avoiding kCFI failures.
> 
> Fixes: 9bb0a9e0626c ("leds: leds-mt6323: Add support for WLEDs and MT6332")
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
>  drivers/leds/leds-mt6323.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)

Applied, thanks

-- 
Lee Jones [李琼斯]