[PATCH for-next v2] RDMA/rxe: Fix coding error in rxe_rcv_mcast_pkt

[Bob Pearson <rpearsonhpe@gmail.com>]

[2]
Replaced unnecessary if(skb) by a comment.

[1]
rxe_rcv_mcast_pkt() in rxe_recv.c can leak SKBs in error path
code. The loop over the QPs attached to a multicast group
creates new cloned SKBs for all but the last QP in the list
and passes the SKB and its clones to rxe_rcv_pkt() for further
processing. Any QPs that do not pass some checks are skipped.
If the last QP in the list fails the tests the SKB is leaked.
This patch checks if the SKB for the last QP was used and if
not frees it. Also removes a redundant loop invariant assignment.

Fixes: 8700e3e7c4857 ("Soft RoCE driver")
Fixes: 71abf20b28ff8 ("RDMA/rxe: Handle skb_clone() failure in rxe_recv.c")
Signed-off-by: Bob Pearson <rpearson@hpe.com>
---
 drivers/infiniband/sw/rxe/rxe_recv.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/infiniband/sw/rxe/rxe_recv.c b/drivers/infiniband/sw/rxe/rxe_recv.c
index c9984a28eecc..9293899ae76d 100644
--- a/drivers/infiniband/sw/rxe/rxe_recv.c
+++ b/drivers/infiniband/sw/rxe/rxe_recv.c
@@ -252,7 +252,6 @@ static void rxe_rcv_mcast_pkt(struct rxe_dev *rxe, struct sk_buff *skb)
 
 	list_for_each_entry(mce, &mcg->qp_list, qp_list) {
 		qp = mce->qp;
-		pkt = SKB_TO_PKT(skb);
 
 		/* validate qp for incoming packet */
 		err = check_type_state(rxe, pkt, qp);
@@ -264,12 +263,18 @@ static void rxe_rcv_mcast_pkt(struct rxe_dev *rxe, struct sk_buff *skb)
 			continue;
 
 		/* for all but the last qp create a new clone of the
-		 * skb and pass to the qp.
+		 * skb and pass to the qp. If an error occurs in the
+		 * checks for the last qp in the list we need to
+		 * free the skb since it hasn't been passed on to
+		 * rxe_rcv_pkt() which would free it later.
 		 */
-		if (mce->qp_list.next != &mcg->qp_list)
+		if (mce->qp_list.next != &mcg->qp_list) {
 			per_qp_skb = skb_clone(skb, GFP_ATOMIC);
-		else
+		} else {
 			per_qp_skb = skb;
+			/* show we have consumed the skb */
+			skb = NULL;
+		}
 
 		if (unlikely(!per_qp_skb))
 			continue;
@@ -284,9 +289,8 @@ static void rxe_rcv_mcast_pkt(struct rxe_dev *rxe, struct sk_buff *skb)
 
 	rxe_drop_ref(mcg);	/* drop ref from rxe_pool_get_key. */
 
-	return;
-
 err1:
+	/* free skb if not consumed */
 	kfree_skb(skb);
 }
 
-- 
2.27.0