[AF_IUCV]: broken send_skb_q results in endless loop

A race has been detected in iucv_callback_txdone().
skb_unlink has to be done inside the locked area.

In addition checkings for successful allocations are inserted.
Signed-off-by: NUrsula Braun <braunu@de.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/iucv/af_iucv.c

@@ -482,6 +482,10 @@ static int iucv_sock_connect(struct socket *sock, struct sockaddr *addr,
 	/* Create path. */
 	iucv->path = iucv_path_alloc(IUCV_QUEUELEN_DEFAULT,
 				     IPRMDATA, GFP_KERNEL);
+	if (!iucv->path) {
+		err = -ENOMEM;
+		goto done;
+	}
 	err = iucv_path_connect(iucv->path, &af_iucv_handler,
 				sa->siucv_user_id, NULL, user_data, sk);
 	if (err) {
@@ -1094,6 +1098,8 @@ static void iucv_callback_rx(struct iucv_path *path, struct iucv_message *msg)
 
 save_message:
 	save_msg = kzalloc(sizeof(struct sock_msg_q), GFP_ATOMIC | GFP_DMA);
+	if (!save_msg)
+		return;
 	save_msg->path = path;
 	save_msg->msg = *msg;
 
@@ -1118,10 +1124,10 @@ static void iucv_callback_txdone(struct iucv_path *path,
 			this = list_skb;
 			list_skb = list_skb->next;
 		} while (memcmp(&msg->tag, this->cb, 4) && list_skb);
+		__skb_unlink(this, list);
 
 		spin_unlock_irqrestore(&list->lock, flags);
 
-		skb_unlink(this, &iucv_sk(sk)->send_skb_q);
 		kfree_skb(this);
 	}