tcp: also NULL skb->dev when copy was needed

In rare cases retransmit logic will make a full skb copy, which will not
trigger the zeroing added in recent change
b738a185beaa ("tcp: ensure skb->dev is NULL before leaving TCP stack").

Cc: Eric Dumazet <[e-mail]>
Fixes: 75c119afe14f ("tcp: implement rb-tree based retransmit queue")
Fixes: 28f8bfd1ac94 ("netfilter: Support iif matches in POSTROUTING")
Signed-off-by: Florian Westphal <[e-mail]>
Signed-off-by: Eric Dumazet <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv4/tcp_output.c

···
 
 		tcp_skb_tsorted_save(skb) {
 			nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
-			err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
-				     -ENOBUFS;
+			if (nskb) {
+				nskb->dev = NULL;
+				err = tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC);
+			} else {
+				err = -ENOBUFS;
+			}
 		} tcp_skb_tsorted_restore(skb);
 
 		if (!err) {