[ipoib] Fix a race when chain-loading undionly.kpxe in IPoIB

The Infiniband link status change callback ipoib_link_state_changed()
may be called while the IPoIB device is closed, in which case there
will not be an IPoIB queue pair to be joined to the IPv4 broadcast
group.  This leads to NULL pointer dereferences in ib_mcast_attach()
and ib_mcast_detach().

Fix by not attempting to join (or leave) the broadcast group unless we
actually have an IPoIB queue pair.

Signed-off-by: Wissam Shoukair <wissams@mellanox.com>
Modified-by: Michael Brown <mcb30@ipxe.org>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/net/ipoib.c

 	int rc;
 
 	/* Leave existing broadcast group */
-	ipoib_leave_broadcast_group ( ipoib );
+	if ( ipoib->qp )
+		ipoib_leave_broadcast_group ( ipoib );
 
 	/* Update MAC address based on potentially-new GID prefix */
 	memcpy ( &ipoib->mac.gid.s.prefix, &ibdev->gid.s.prefix,
 	netdev_link_err ( netdev, ( rc ? rc : -EINPROGRESS_JOINING ) );
 
 	/* Join new broadcast group */
-	if ( ib_is_open ( ibdev ) && ib_link_ok ( ibdev ) &&
+	if ( ib_is_open ( ibdev ) && ib_link_ok ( ibdev ) && ipoib->qp &&
 	     ( ( rc = ipoib_join_broadcast_group ( ipoib ) ) != 0 ) ) {
 		DBGC ( ipoib, "IPoIB %p could not rejoin broadcast group: "
 		       "%s\n", ipoib, strerror ( rc ) );
 
 	/* Tear down the queues */
 	ib_destroy_qp ( ibdev, ipoib->qp );
+	ipoib->qp = NULL;
 	ib_destroy_cq ( ibdev, ipoib->cq );
+	ipoib->cq = NULL;
 
 	/* Close IB device */
 	ib_close ( ibdev );

src/net/infiniband.c

 	struct ib_multicast_gid *mgid;
 	int rc;
 
+	/* Sanity check */
+	assert ( qp != NULL );
+
 	/* Add to software multicast GID list */
 	mgid = zalloc ( sizeof ( *mgid ) );
 	if ( ! mgid ) {
 		       union ib_gid *gid ) {
 	struct ib_multicast_gid *mgid;
 
+	/* Sanity check */
+	assert ( qp != NULL );
+
 	/* Remove from hardware multicast GID list */
 	ibdev->op->mcast_detach ( ibdev, qp, gid );
 

src/net/infiniband/ib_mcast.c

 	DBGC ( ibdev, "IBDEV %p QPN %lx joining " IB_GID_FMT "\n",
 	       ibdev, qp->qpn, IB_GID_ARGS ( gid ) );
 
+	/* Sanity check */
+	assert ( qp != NULL );
+
 	/* Initialise structure */
 	membership->qp = qp;
 	memcpy ( &membership->gid, gid, sizeof ( membership->gid ) );
 	DBGC ( ibdev, "IBDEV %p QPN %lx leaving " IB_GID_FMT "\n",
 	       ibdev, qp->qpn, IB_GID_ARGS ( gid ) );
 
+	/* Sanity check */
+	assert ( qp != NULL );
+
 	/* Detach from multicast GID */
 	ib_mcast_detach ( ibdev, qp, &membership->gid );