[PATCH] scsi: target: cxgbit: check skb dequeue result

[Denis Plotnikov <den-plotnikov@xxxxxxxxxxxxxx>]

On a couple of abort packet paths skb dequeuing may end up with
returning NULL, which, in turn, may end up with further null
pointer dereference.

Fix it by checking the return value of skb dequeuing.

Found by Linux Verification Center(linuxtesting.org) with SVACE.

Fixes: 9730ffcb8957 (cxgbit: add files for cxgbit.ko)
Signed-off-by: Denis Plotnikov <den-plotnikov@xxxxxxxxxxxxxx>
---
 drivers/target/iscsi/cxgbit/cxgbit_cm.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/target/iscsi/cxgbit/cxgbit_cm.c b/drivers/target/iscsi/cxgbit/cxgbit_cm.c
index 518ded214e74..d43fd761c20a 100644
--- a/drivers/target/iscsi/cxgbit/cxgbit_cm.c
+++ b/drivers/target/iscsi/cxgbit/cxgbit_cm.c
@@ -669,6 +669,9 @@ static int cxgbit_send_abort_req(struct cxgbit_sock *csk)
 		cxgbit_send_tx_flowc_wr(csk);
 
 	skb = __skb_dequeue(&csk->skbq);
+	if (!skb)
+		return 0;
+
 	cxgb_mk_abort_req(skb, len, csk->tid, csk->txq_idx,
 			  csk->com.cdev, cxgbit_abort_arp_failure);
 
@@ -1769,9 +1772,10 @@ static void cxgbit_abort_req_rss(struct cxgbit_sock *csk, struct sk_buff *skb)
 		cxgbit_send_tx_flowc_wr(csk);
 
 	rpl_skb = __skb_dequeue(&csk->skbq);
-
-	cxgb_mk_abort_rpl(rpl_skb, len, csk->tid, csk->txq_idx);
-	cxgbit_ofld_send(csk->com.cdev, rpl_skb);
+	if (!rpl_skb) {
+		cxgb_mk_abort_rpl(rpl_skb, len, csk->tid, csk->txq_idx);
+		cxgbit_ofld_send(csk->com.cdev, rpl_skb);
+	}
 
 	if (wakeup_thread) {
 		cxgbit_queue_rx_skb(csk, skb);
-- 
2.25.1