netdev - Re: [PATCH net-next v1 1/1] ppp: Fix KMSAN warning by initializing 2-byte header

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Message-ID: <rqdpj4pdxkiad7amqp7qzsrdtgy3i5beqpz7gsrjy4dwkmwg2x@3bsn7svbawic>
Date: Fri, 21 Feb 2025 09:48:33 +0800
From: Jiayuan Chen <jiayuan.chen@...ux.dev>
To: Jakub Kicinski <kuba@...nel.org>
Cc: bpf@...r.kernel.org, netdev@...r.kernel.org, andrew+netdev@...n.ch, 
	davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com, horms@...nel.org, 
	ricardo@...liere.net, viro@...iv.linux.org.uk, dmantipov@...dex.ru, 
	aleksander.lobakin@...el.com, linux-ppp@...r.kernel.org, linux-kernel@...r.kernel.org, 
	mrpre@....com, syzbot+853242d9c9917165d791@...kaller.appspotmail.com
Subject: Re: [PATCH net-next v1 1/1] ppp: Fix KMSAN warning by initializing
 2-byte header

On Thu, Feb 20, 2025 at 03:27:03PM -0800, Jakub Kicinski wrote:
> On Tue, 18 Feb 2025 21:31:44 +0800 Jiayuan Chen wrote:
> > -		*(u8 *)skb_push(skb, 2) = 1;
> > +		*(u16 *)skb_push(skb, 2) = 1;
> 
> This will write the 1 to a different byte now, on big endian machines.
> Probably doesn't matter but I doubt it's intentional?
> -- 
> pw-bot: cr
You are correct that I assigned the value in a way that produces different
data on big-endian and little-endian systems, although it doesn't cause
any issues.
I think it's better to assign it correctly according to the corresponding
header and add more comments to avoid confusion for other developers in
the future.