ionic: check port ptr before use

[ Upstream commit 2bcbf42 ]

Check for corner case of port_init failure before using
the port_info pointer.

Fixes: 4d03e00 ("ionic: Add initial ethtool support")
Signed-off-by: Shannon Nelson <snelson@pensando.io>
Link: https://lore.kernel.org/r/20201104195606.61184-1-snelson@pensando.io
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/ethernet/pensando/ionic/ionic_ethtool.c

@@ -126,6 +126,11 @@ static int ionic_get_link_ksettings(struct net_device *netdev,
 
 	ethtool_link_ksettings_zero_link_mode(ks, supported);
 
+	if (!idev->port_info) {
+		netdev_err(netdev, "port_info not initialized\n");
+		return -EOPNOTSUPP;
+	}
+
 	/* The port_info data is found in a DMA space that the NIC keeps
 	 * up-to-date, so there's no need to request the data from the
 	 * NIC, we already have it in our memory space.