sock: set sk_err to ee_errno on dequeue from errq

When setting sk_err, set it to ee_errno, not ee_origin.

Commit f5f99309 ("sock: do not set sk_err in
sock_dequeue_err_skb") disabled updating sk_err on errq dequeue,
which is correct for most error types (origins):

  -       sk->sk_err = err;

Commit 38b25793 ("sock: reset sk_err when the error queue is
empty") reenabled the behavior for IMCP origins, which do require it:

  +       if (icmp_next)
  +               sk->sk_err = SKB_EXT_ERR(skb_next)->ee.ee_origin;

But read from ee_errno.

Fixes: 38b25793 ("sock: reset sk_err when the error queue is empty")
Reported-by: Ayush Ranjan <ayushranjan@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Link: https://lore.kernel.org/r/20201126151220.2819322-1-willemdebruijn.kernel@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/core/skbuff.c

@@ -4549,7 +4549,7 @@ struct sk_buff *sock_dequeue_err_skb(struct sock *sk)
 	if (skb && (skb_next = skb_peek(q))) {
 		icmp_next = is_icmp_err_skb(skb_next);
 		if (icmp_next)
-			sk->sk_err = SKB_EXT_ERR(skb_next)->ee.ee_origin;
+			sk->sk_err = SKB_EXT_ERR(skb_next)->ee.ee_errno;
 	}
 	spin_unlock_irqrestore(&q->lock, flags);