RDMA/iw_cxgb4: Avoid touch after free error in ARP failure handlers

The patch 761e19a5 (RDMA/iw_cxgb4: Handle return value of
c4iw_ofld_send() in abort_arp_failure()) from May 6, 2016
leads to the following static checker warning:
	drivers/infiniband/hw/cxgb4/cm.c:575 abort_arp_failure()
	warn: passing freed memory 'skb'

Also fixes skb leak when l2t resolution fails

Fixes: 761e19a5 (RDMA/iw_cxgb4: Handle return value of
c4iw_ofld_send() in abort_arp_failure())
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NRaju Rangoju <rajur@chelsio.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

drivers/infiniband/hw/cxgb4/cm.c

@@ -488,6 +488,7 @@ static int _put_ep_safe(struct c4iw_dev *dev, struct sk_buff *skb)
 
 	ep = *((struct c4iw_ep **)(skb->cb + 2 * sizeof(void *)));
 	release_ep_resources(ep);
+	kfree_skb(skb);
 	return 0;
 }
 
@@ -498,6 +499,7 @@ static int _put_pass_ep_safe(struct c4iw_dev *dev, struct sk_buff *skb)
 	ep = *((struct c4iw_ep **)(skb->cb + 2 * sizeof(void *)));
 	c4iw_put_ep(&ep->parent_ep->com);
 	release_ep_resources(ep);
+	kfree_skb(skb);
 	return 0;
 }
 
@@ -569,11 +571,13 @@ static void abort_arp_failure(void *handle, struct sk_buff *skb)
 
 	pr_debug("%s rdev %p\n", __func__, rdev);
 	req->cmd = CPL_ABORT_NO_RST;
+	skb_get(skb);
 	ret = c4iw_ofld_send(rdev, skb);
 	if (ret) {
 		__state_set(&ep->com, DEAD);
 		queue_arp_failure_cpl(ep, skb, FAKE_CPL_PUT_EP_SAFE);
-	}
+	} else
+		kfree_skb(skb);
 }
 
 static int send_flowc(struct c4iw_ep *ep)