af_iucv: wrong mapping of sent and confirmed skbs

When sending data through IUCV a MESSAGE COMPLETE interrupt
signals that sent data memory can be freed or reused again.
With commit f9c41a6
"af_iucv: fix recvmsg by replacing skb_pull() function" the
MESSAGE COMPLETE callback iucv_callback_txdone() identifies
the wrong skb as being confirmed, which leads to data corruption.
This patch fixes the skb mapping logic in iucv_callback_txdone().

Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/iucv/af_iucv.c

@@ -1830,7 +1830,7 @@ static void iucv_callback_txdone(struct iucv_path *path,
 		spin_lock_irqsave(&list->lock, flags);
 
 		while (list_skb != (struct sk_buff *)list) {
-			if (msg->tag != IUCV_SKB_CB(list_skb)->tag) {
+			if (msg->tag == IUCV_SKB_CB(list_skb)->tag) {
 				this = list_skb;
 				break;
 			}