linux-kernel - Re: [PATCH net-next v2 1/1] ppp: Fix KMSAN warning by initializing 2-byte header

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Message-ID: <20250224160706.1ebde164@kernel.org>
Date: Mon, 24 Feb 2025 16:07:06 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Jiayuan Chen <jiayuan.chen@...ux.dev>
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 v2 1/1] ppp: Fix KMSAN warning by initializing
 2-byte header

On Tue, 25 Feb 2025 07:20:08 +0800 Jiayuan Chen wrote:
> I apologize for the mistake, I've investigated the original maintainer's
> user-space PPP implementation and libpcap's behavior, and found that
> initializing the first byte to 0 or 1 is necessary, it indicates
> direction, which is used in libpcap to distinguish between inbound and
> outbound traffic.
> For more details, please refer to the cover letter of my v3 patch.
> 
> https://lore.kernel.org/linux-ppp/20250222092556.274267-1-jiayuan.chen@linux.dev/T/#t

You can still use the htons() there, it's cleaner.