linux-kernel - Re: [PATCH net-next v2] net: napi: Prevent overflow of napi_defer_hard

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Message-ID: <CANn89i+=HiffVo9iv2NKMC2LFT15xFLG16h7wN3MCrTiKT3zQQ@mail.gmail.com>
Date: Thu, 5 Sep 2024 13:08:05 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Joe Damato <jdamato@...tly.com>
Cc: netdev@...r.kernel.org, mkarsten@...terloo.ca, 
	Jakub Kicinski <kuba@...nel.org>, "David S. Miller" <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>, 
	Jonathan Corbet <corbet@....net>, Breno Leitao <leitao@...ian.org>, 
	Alexander Lobakin <aleksander.lobakin@...el.com>, Johannes Berg <johannes.berg@...el.com>, 
	Jamie Bainbridge <jamie.bainbridge@...il.com>, 
	"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v2] net: napi: Prevent overflow of napi_defer_hard_irqs

On Wed, Sep 4, 2024 at 5:34 PM Joe Damato <jdamato@...tly.com> wrote:
>
> In commit 6f8b12d661d0 ("net: napi: add hard irqs deferral feature")
> napi_defer_irqs was added to net_device and napi_defer_irqs_count was
> added to napi_struct, both as type int.
>
> This value never goes below zero, so there is not reason for it to be a
> signed int. Change the type for both from int to u32, and add an
> overflow check to sysfs to limit the value to S32_MAX.
>
> The limit of S32_MAX was chosen because the practical limit before this
> patch was S32_MAX (anything larger was an overflow) and thus there are
> no behavioral changes introduced. If the extra bit is needed in the
> future, the limit can be raised.

Reviewed-by: Eric Dumazet <edumazet@...gle.com>