netdev - Re: [PATCH net] llc: verify mac len before reading mac header

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Message-ID: <20231025160016.0ffecfac@kernel.org>
Date: Wed, 25 Oct 2023 16:00:16 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
 pabeni@...hat.com, Willem de Bruijn <willemb@...gle.com>,
 syzbot+a8c7be6dee0de1b669cc@...kaller.appspotmail.com,
 joonwpark81@...il.com
Subject: Re: [PATCH net] llc: verify mac len before reading mac header

On Tue, 24 Oct 2023 23:12:13 -0400 Willem de Bruijn wrote:
> Fixes: f83f1768f833 ("[LLC]: skb allocation size for responses")
> 
> Can respin if necessary.
> 
> At least one of the three eth_hdr uses goes back to before the start
> of git history.

Right, good enough.

> But the one that syzbot exercises is introduced in this commit.
> 
> That commit is old enough (2008), that effectively all stable kernels
> should receive this. This commit also introduces llc_mac_header_len,
> which shows at least one valid L2 header that is not an Ethernet
> header, back in the day:
> 
> +#ifdef CONFIG_TR
> +       case ARPHRD_IEEE802_TR:
> +               return sizeof(struct trh_hdr);
> +#endif
> 
> But that token ring variant was removed in 2012 in commit 211ed865108e
> ("net: delete all instances of special processing for token ring").