Re: [PATCH v3] wifi: mac80211: fix integer overflow in hwmp_route_info_get()

[Johannes Berg]

On Thu, 2025-01-16 at 08:49 +0000, Gavrilov Ilia wrote:
> Since the new_metric and last_hop_metric variables can reach
> the MAX_METRIC(0xffffffff) value, an integer overflow may occur
> when multiplying them by 10/9. It can lead to incorrect behavior.
> 
> Found by InfoTeCS on behalf of Linux Verification Center
> (linuxtesting.org) with SVACE.
> 
> Fixes: a8d418d9ac25 ("mac80211: mesh: only switch path when new metric is at least 10% better")
> Cc: stable@xxxxxxxxxxxxxxx

Seems a bit overblown for stable, but also don't really care...

> +static inline bool is_metric_better(u32 x, u32 y, u32 percent)
> +{

You shouldn't put inline here, in general.

Also that function probably wants a comment, and the 'percent' argument
is hardcoded to 10, so you don't need it. Let's keep this stuff simple,
*especially* if it's for stable too ...

> +	if (check_add_overflow(x, a, &e)) {
> +		if (x > y - a)
> +			return false;

seems simpler as "return x > y - a;" or so?

johannes