netdev - Re: [PATCH v1 net 1/5] sit: Pull header after checking skb->protocol in sit_tunnel

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Message-ID: <20240417190432.5d9dc732@kernel.org>
Date: Wed, 17 Apr 2024 19:04:32 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, David Ahern
 <dsahern@...nel.org>, Steffen Klassert <steffen.klassert@...unet.com>,
 Herbert Xu <herbert@...dor.apana.org.au>, Willem de Bruijn
 <willemb@...gle.com>, Kuniyuki Iwashima <kuni1840@...il.com>,
 <netdev@...r.kernel.org>, syzkaller <syzkaller@...glegroups.com>
Subject: Re: [PATCH v1 net 1/5] sit: Pull header after checking
 skb->protocol in sit_tunnel_xmit().

On Mon, 15 Apr 2024 15:20:37 -0700 Kuniyuki Iwashima wrote:
> syzkaller crafted a GSO packet of ETH_P_8021AD + ETH_P_NSH and sent it
> over sit0.
> 
> After nsh_gso_segment(), skb->data - skb->head was 138, on the other
> hand, skb->network_header was 128.

is data offset > skb->network_header valid at this stage?
Can't we drop these packets instead?