netdev - Re: [PATCH net] geneve: fix header validation in geneve[6]_xmit

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Date: Thu, 4 Apr 2024 19:09:22 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: "David S . Miller" <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com, syzbot+9ee20ec1de7b3168db09@...kaller.appspotmail.com, 
	Phillip Potter <phil@...lpotter.co.uk>, Sabrina Dubroca <sd@...asysnail.net>
Subject: Re: [PATCH net] geneve: fix header validation in geneve[6]_xmit_skb

On Thu, Apr 4, 2024 at 7:00 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Thu,  4 Apr 2024 13:11:26 +0000 Eric Dumazet wrote:
> > syzbot is able to trigger an uninit-value in geneve_xmit() [1]
> >
> > Problem : While most ip tunnel helpers (like ip_tunnel_get_dsfield())
> > uses skb_protocol(skb, true), pskb_inet_may_pull() is only using
> > skb->protocol.
> >
> > If anything else than ETH_P_IPV6 or ETH_P_IP is found in skb->protocol,
> > pskb_inet_may_pull() does nothing at all.
> >
> > If a vlan tag was provided by the caller (af_packet in the syzbot case),
> > the network header might not point to the correct location, and skb
> > linear part could be smaller than expected.
> >
> > Add skb_vlan_inet_prepare() to perform a complete mac validation.
> >
> > Use this in geneve for the moment, I suspect we need to adopt this
> > more broadly.
>
> Something is cause the ttl test do break:
>
> # │ geneve │     4 │     4 │ inherit 0x3c │    inherit 8 │ false │./l2_tos_ttl_inherit.sh: line 350: printf: 0xeaECT0: invalid hex number
> ok 1 selftests: net: l2_tos_ttl_inherit.sh # SKIP
>
> https://netdev-3.bots.linux.dev/vmksft-net-dbg/results/537382/6-l2-tos-ttl-inherit-sh/stdout
>
> Is is possibly this change?

Let me check this, thanks !