RDMA/rxe: Fix FIXME in rxe_udp_encap_recv()

rxe_udp_encap_recv() drops the reference to rxe->ib_dev taken by
rxe_get_dev_from_net() which should be held until each received skb is
freed. This patch moves the calls to ib_device_put() to each place a
received skb is freed. It also takes references to the ib_device for each
cloned skb created to process received multicast packets.

Fixes: 4c173f59 ("RDMA/rxe: Use ib_device_get_by_netdev() instead of open coding")
Link: https://lore.kernel.org/r/20210128233318.2591-1-rpearson@hpe.comSigned-off-by: Bob Pearson <rpearson@hpe.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/sw/rxe/rxe_comp.c

@@ -515,6 +515,7 @@ static void rxe_drain_resp_pkts(struct rxe_qp *qp, bool notify)
 	while ((skb = skb_dequeue(&qp->resp_pkts))) {
 		rxe_drop_ref(qp);
 		kfree_skb(skb);
+		ib_device_put(qp->ibqp.device);
 	}
 
 	while ((wqe = queue_head(qp->sq.queue))) {
@@ -527,6 +528,17 @@ static void rxe_drain_resp_pkts(struct rxe_qp *qp, bool notify)
 	}
 }
 
+static void free_pkt(struct rxe_pkt_info *pkt)
+{
+	struct sk_buff *skb = PKT_TO_SKB(pkt);
+	struct rxe_qp *qp = pkt->qp;
+	struct ib_device *dev = qp->ibqp.device;
+
+	kfree_skb(skb);
+	rxe_drop_ref(qp);
+	ib_device_put(dev);
+}
+
 int rxe_completer(void *arg)
 {
 	struct rxe_qp *qp = (struct rxe_qp *)arg;
@@ -624,11 +636,8 @@ int rxe_completer(void *arg)
 			break;
 
 		case COMPST_DONE:
-			if (pkt) {
-				rxe_drop_ref(pkt->qp);
-				kfree_skb(skb);
-				skb = NULL;
-			}
+			if (pkt)
+				free_pkt(pkt);
 			goto done;
 
 		case COMPST_EXIT:
@@ -671,12 +680,8 @@ int rxe_completer(void *arg)
 			 */
 			if (qp->comp.started_retry &&
 			    !qp->comp.timeout_retry) {
-				if (pkt) {
-					rxe_drop_ref(pkt->qp);
-					kfree_skb(skb);
-					skb = NULL;
-				}
-
+				if (pkt)
+					free_pkt(pkt);
 				goto done;
 			}
 
@@ -699,13 +704,8 @@ int rxe_completer(void *arg)
 					qp->comp.started_retry = 1;
 					rxe_run_task(&qp->req.task, 0);
 				}
-
-				if (pkt) {
-					rxe_drop_ref(pkt->qp);
-					kfree_skb(skb);
-					skb = NULL;
-				}
-
+				if (pkt)
+					free_pkt(pkt);
 				goto done;
 
 			} else {
@@ -726,9 +726,7 @@ int rxe_completer(void *arg)
 				mod_timer(&qp->rnr_nak_timer,
 					  jiffies + rnrnak_jiffies(aeth_syn(pkt)
 						& ~AETH_TYPE_MASK));
-				rxe_drop_ref(pkt->qp);
-				kfree_skb(skb);
-				skb = NULL;
+				free_pkt(pkt);
 				goto exit;
 			} else {
 				rxe_counter_inc(rxe,
@@ -742,13 +740,8 @@ int rxe_completer(void *arg)
 			WARN_ON_ONCE(wqe->status == IB_WC_SUCCESS);
 			do_complete(qp, wqe);
 			rxe_qp_error(qp);
-
-			if (pkt) {
-				rxe_drop_ref(pkt->qp);
-				kfree_skb(skb);
-				skb = NULL;
-			}
-
+			if (pkt)
+				free_pkt(pkt);
 			goto exit;
 		}
 	}

drivers/infiniband/sw/rxe/rxe_net.c

@@ -152,10 +152,14 @@ static struct dst_entry *rxe_find_route(struct net_device *ndev,
 static int rxe_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 {
 	struct udphdr *udph;
+	struct rxe_dev *rxe;
 	struct net_device *ndev = skb->dev;
-	struct rxe_dev *rxe = rxe_get_dev_from_net(ndev);
 	struct rxe_pkt_info *pkt = SKB_TO_PKT(skb);
 
+	/* takes a reference on rxe->ib_dev
+	 * drop when skb is freed
+	 */
+	rxe = rxe_get_dev_from_net(ndev);
 	if (!rxe)
 		goto drop;
 
@@ -174,12 +178,6 @@ static int rxe_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 
 	rxe_rcv(skb);
 
-	/*
-	 * FIXME: this is in the wrong place, it needs to be done when pkt is
-	 * destroyed
-	 */
-	ib_device_put(&rxe->ib_dev);
-
 	return 0;
 drop:
 	kfree_skb(skb);

drivers/infiniband/sw/rxe/rxe_recv.c

@@ -274,6 +274,10 @@ static void rxe_rcv_mcast_pkt(struct rxe_dev *rxe, struct sk_buff *skb)
 		 */
 		if (mce->qp_list.next != &mcg->qp_list) {
 			per_qp_skb = skb_clone(skb, GFP_ATOMIC);
+			if (WARN_ON(!ib_device_try_get(&rxe->ib_dev))) {
+				kfree_skb(per_qp_skb);
+				continue;
+			}
 		} else {
 			per_qp_skb = skb;
 			/* show we have consumed the skb */
@@ -296,6 +300,7 @@ static void rxe_rcv_mcast_pkt(struct rxe_dev *rxe, struct sk_buff *skb)
 err1:
 	/* free skb if not consumed */
 	kfree_skb(skb);
+	ib_device_put(&rxe->ib_dev);
 }
 
 /**
@@ -405,4 +410,5 @@ void rxe_rcv(struct sk_buff *skb)
 		rxe_drop_ref(pkt->qp);
 
 	kfree_skb(skb);
+	ib_device_put(&rxe->ib_dev);
 }

drivers/infiniband/sw/rxe/rxe_resp.c

@@ -99,6 +99,7 @@ static inline enum resp_states get_req(struct rxe_qp *qp,
 		while ((skb = skb_dequeue(&qp->req_pkts))) {
 			rxe_drop_ref(qp);
 			kfree_skb(skb);
+			ib_device_put(qp->ibqp.device);
 		}
 
 		/* go drain recv wr queue */
@@ -1012,6 +1013,7 @@ static enum resp_states cleanup(struct rxe_qp *qp,
 		skb = skb_dequeue(&qp->req_pkts);
 		rxe_drop_ref(qp);
 		kfree_skb(skb);
+		ib_device_put(qp->ibqp.device);
 	}
 
 	if (qp->resp.mr) {
@@ -1176,6 +1178,7 @@ static void rxe_drain_req_pkts(struct rxe_qp *qp, bool notify)
 	while ((skb = skb_dequeue(&qp->req_pkts))) {
 		rxe_drop_ref(qp);
 		kfree_skb(skb);
+		ib_device_put(qp->ibqp.device);
 	}
 
 	if (notify)