linux-kernel - Re: [PATCH v3] wifi: mac80211: fix integer overflow in hwmp_route_info

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Message-ID: <56a9253a801757c03320cfe0000c5ac68dacac14.camel@sipsolutions.net>
Date: Tue, 11 Feb 2025 14:29:11 +0100
From: Johannes Berg <johannes@...solutions.net>
To: Gavrilov Ilia <Ilia.Gavrilov@...otecs.ru>
Cc: Julan Hsu <julanhsu@...gle.com>, "linux-wireless@...r.kernel.org"
	 <linux-wireless@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	 <linux-kernel@...r.kernel.org>, "lvc-project@...uxtesting.org"
	 <lvc-project@...uxtesting.org>, "stable@...r.kernel.org"
	 <stable@...r.kernel.org>
Subject: Re: [PATCH v3] wifi: mac80211: fix integer overflow in
 hwmp_route_info_get()

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@...r.kernel.org

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