fou: remove warn in gue_gro_receive on unsupported protocol

[ Upstream commit dd89a81 ]

Drop the WARN_ON_ONCE inn gue_gro_receive if the encapsulated type is
not known or does not have a GRO handler.

Such a packet is easily constructed. Syzbot generates them and sets
off this warning.

Remove the warning as it is expected and not actionable.

The warning was previously reduced from WARN_ON to WARN_ON_ONCE in
commit 2701366 ("fou: Do WARN_ON_ONCE in gue_gro_receive for bad
proto callbacks").

Signed-off-by: Willem de Bruijn <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>

CVE-2024-44940
(cherry picked from commit 5a2e37bc648a2503bf6d687aed27b9f4455d82eb linux-6.1.y)
Signed-off-by: Bethany Jamison <[email protected]>
Acked-by: ivanhu <[email protected]>
Acked-by: Guoqing Jiang <[email protected]>
Signed-off-by: Stefan Bader <[email protected]>

Author: wdebruij

net/ipv4/fou.c

@@ -453,7 +453,7 @@ static struct sk_buff *gue_gro_receive(struct sock *sk,
 
 	offloads = NAPI_GRO_CB(skb)->is_ipv6 ? inet6_offloads : inet_offloads;
 	ops = rcu_dereference(offloads[proto]);
-	if (WARN_ON_ONCE(!ops || !ops->callbacks.gro_receive))
+	if (!ops || !ops->callbacks.gro_receive)
 		goto out;
 
 	pp = call_gro_receive(ops->callbacks.gro_receive, head, skb);