udp: call skb_orphan() before skb_attempt_defer_free()

Standard UDP receive path does not use skb->destructor.

But skmsg layer does use it, since it calls skb_set_owner_sk_safe()
from udp_read_skb().

This then triggers this warning in skb_attempt_defer_free():

DEBUG_NET_WARN_ON_ONCE(skb->destructor);

We must call skb_orphan() to fix this issue.

Fixes: 6471658dc66c ("udp: use skb_attempt_defer_free()")
Reported-by: [e-mail]
Closes: https://lore.kernel.org/netdev/[e-mail]/T/#u
Signed-off-by: Eric Dumazet <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

net/ipv4/udp.c

···
 		sk_peek_offset_bwd(sk, len);
 
 	if (!skb_shared(skb)) {
+		skb_orphan(skb);
 		skb_attempt_defer_free(skb);
 		return;
 	}