Re: [PATCH v2 04/11] leds: rgb: ktd202x: Fix a division by zero with long blinks

[sashiko-bot@kernel.org]

> From: Joseph Telaak <joseph@telaak.dev>
> 
> blink_set() works out the on time as delay_on * 256 / (delay_on +
> delay_off) in unsigned long, with delays straight from the timer
> trigger's sysfs files:
> 
> - when the two delays add up to exactly 2^32 on 32 bit, or 2^64 on
>   64 bit, the sum wraps to 0 and the kernel divides by zero, for
>   example with "echo 2147483648" into both delay_on and delay_off.
>   That oopses on x86 and gives an arbitrary result on MIPS and arm64.
> - on 32 bit the product already overflows once delay_on is above about
>   4.6 hours, and a sum that wraps sets the wrong period, so long blinks
>   get an arbitrary duty cycle
> 
> Saturate the sum, and compute the on time with mul_u64_u64_div_u64().
> 
> Fixes: 0ebdb7210943 ("leds: Add ktd202x driver")
> Cc: stable@vger.kernel.org
> Signed-off-by: Joseph Telaak <joseph@telaak.dev>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261109-ktd202x-et6326-v2-0-56e97c226658@telaak.dev?part=4