IB/cm: Remove cma_multicast->igmp_joined

This variable isn't read and written to with proper locking, so it is
racy. Instead of using an unlocked bool use presence in the mc->list

The caller could race rdma_join_multicast with rdma_leave_multicast which
would leak a mc join and cause a use after free of mc.

Instead, do not add the mc to the list until it has completed
initialization, all mcs on the list require leaving.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>

drivers/infiniband/core/cma.c

@@ -366,7 +366,6 @@ struct cma_multicast {
 	void			*context;
 	struct sockaddr_storage	addr;
 	struct kref		mcref;
-	bool			igmp_joined;
 	u8			join_state;
 };
 
@@ -1643,21 +1642,14 @@ static void cma_release_port(struct rdma_id_private *id_priv)
 static void cma_leave_roce_mc_group(struct rdma_id_private *id_priv,
 				    struct cma_multicast *mc)
 {
-	if (mc->igmp_joined) {
-		struct rdma_dev_addr *dev_addr =
-			&id_priv->id.route.addr.dev_addr;
-		struct net_device *ndev = NULL;
-
-		if (dev_addr->bound_dev_if)
-			ndev = dev_get_by_index(dev_addr->net,
-						dev_addr->bound_dev_if);
-		if (ndev) {
-			cma_igmp_send(ndev,
-				      &mc->multicast.ib->rec.mgid,
-				      false);
-			dev_put(ndev);
-		}
-		mc->igmp_joined = false;
+	struct rdma_dev_addr *dev_addr = &id_priv->id.route.addr.dev_addr;
+	struct net_device *ndev = NULL;
+
+	if (dev_addr->bound_dev_if)
+		ndev = dev_get_by_index(dev_addr->net, dev_addr->bound_dev_if);
+	if (ndev) {
+		cma_igmp_send(ndev, &mc->multicast.ib->rec.mgid, false);
+		dev_put(ndev);
 	}
 	kref_put(&mc->mcref, release_mc);
 }
@@ -4196,8 +4188,6 @@ static int cma_iboe_join_multicast(struct rdma_id_private *id_priv,
 			if (!send_only) {
 				err = cma_igmp_send(ndev, &mc->multicast.ib->rec.mgid,
 						    true);
-				if (!err)
-					mc->igmp_joined = true;
 			}
 		}
 	} else {
@@ -4249,26 +4239,29 @@ int rdma_join_multicast(struct rdma_cm_id *id, struct sockaddr *addr,
 	memcpy(&mc->addr, addr, rdma_addr_size(addr));
 	mc->context = context;
 	mc->id_priv = id_priv;
-	mc->igmp_joined = false;
 	mc->join_state = join_state;
-	spin_lock(&id_priv->lock);
-	list_add(&mc->list, &id_priv->mc_list);
-	spin_unlock(&id_priv->lock);
 
 	if (rdma_protocol_roce(id->device, id->port_num)) {
 		kref_init(&mc->mcref);
 		ret = cma_iboe_join_multicast(id_priv, mc);
-	} else if (rdma_cap_ib_mcast(id->device, id->port_num))
+		if (ret)
+			goto out_err;
+	} else if (rdma_cap_ib_mcast(id->device, id->port_num)) {
 		ret = cma_join_ib_multicast(id_priv, mc);
-	else
+		if (ret)
+			goto out_err;
+	} else {
 		ret = -ENOSYS;
-
-	if (ret) {
-		spin_lock_irq(&id_priv->lock);
-		list_del(&mc->list);
-		spin_unlock_irq(&id_priv->lock);
-		kfree(mc);
+		goto out_err;
 	}
+
+	spin_lock(&id_priv->lock);
+	list_add(&mc->list, &id_priv->mc_list);
+	spin_unlock(&id_priv->lock);
+
+	return 0;
+out_err:
+	kfree(mc);
 	return ret;
 }
 EXPORT_SYMBOL(rdma_join_multicast);