RDMA/core: Fix use after free and refcnt leak on ndev in_device in iw…

…arp_query_port

If an iWARP driver is probed and removed while there are no ips set for
the device, it will lead to a reference count leak on the inet device of
the netdevice.

In addition, the netdevice was accessed after already calling netdev_put,
which could lead to using the netdev after already freed.

Fixes: 4929116 ("RDMA/core: Add common iWARP query port")
Link: https://lore.kernel.org/r/20190925123332.10746-1-michal.kalderon@marvell.com
Signed-off-by: Ariel Elior <ariel.elior@marvell.com>
Signed-off-by: Michal Kalderon <michal.kalderon@marvell.com>
Reviewed-by: Shiraz Saleem <shiraz.saleem@intel.com>
Reviewed-by: Kamal Heib <kamalheib1@gmail.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/device.c

@@ -1987,28 +1987,29 @@ static int iw_query_port(struct ib_device *device,
  if (!netdev)
  return -ENODEV;
 
- dev_put(netdev);
-
  port_attr->max_mtu = IB_MTU_4096;
  port_attr->active_mtu = ib_mtu_int_to_enum(netdev->mtu);
 
  if (!netif_carrier_ok(netdev)) {
  port_attr->state = IB_PORT_DOWN;
  port_attr->phys_state = IB_PORT_PHYS_STATE_DISABLED;
  } else {
- inetdev = in_dev_get(netdev);
+ rcu_read_lock();
+ inetdev = __in_dev_get_rcu(netdev);
 
  if (inetdev && inetdev->ifa_list) {
  port_attr->state = IB_PORT_ACTIVE;
  port_attr->phys_state = IB_PORT_PHYS_STATE_LINK_UP;
- in_dev_put(inetdev);
  } else {
  port_attr->state = IB_PORT_INIT;
  port_attr->phys_state =
  IB_PORT_PHYS_STATE_PORT_CONFIGURATION_TRAINING;
  }
+
+ rcu_read_unlock();
  }
 
+ dev_put(netdev);
  err = device->ops.query_port(device, port_num, port_attr);
  if (err)
  return err;