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

[Jakub Kicinski <kuba@kernel.org>]

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").