[PATCH v2] net: lan966x: avoid unregistering netdev on register failure

[Myeonghun Pak <mhun512@gmail.com>]

lan966x_probe_port() stores the newly allocated net_device in the
port before calling register_netdev(). If register_netdev() fails,
the probe error path calls lan966x_cleanup_ports(), which sees
port->dev and calls unregister_netdev() for a device that was never
registered.

Destroy the phylink instance created for this port and clear port->dev
before returning the registration error, matching the existing guard
used by the common cleanup path. Also require port->dev to be non-NULL
before matching it against the FDMA netdev, so the error path cannot treat
an uninitialized FDMA netdev and a failed port as a valid match.

Fixes: d28d6d2e37d1 ("net: lan966x: add port module support")
Co-developed-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Myeonghun Pak <mhun512@gmail.com>
---
Changes in v2:
- Require port->dev to be non-NULL before calling the FDMA netdev cleanup
  path, avoiding a NULL == NULL match when register_netdev() fails before
  FDMA NAPI has been initialized.

 drivers/net/ethernet/microchip/lan966x/lan966x_main.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_main.c b/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
index 47752d3fde..22c496f588 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
@@ -756,7 +756,7 @@ static void lan966x_cleanup_ports(struct lan966x *lan966x)
 			unregister_netdev(port->dev);
 
 		lan966x_xdp_port_deinit(port);
-		if (lan966x->fdma && lan966x->fdma_ndev == port->dev)
+		if (lan966x->fdma && port->dev && lan966x->fdma_ndev == port->dev)
 			lan966x_fdma_netdev_deinit(lan966x, port->dev);
 
 		if (port->phylink) {
@@ -873,6 +873,9 @@ static int lan966x_probe_port(struct lan966x *lan966x, u32 p,
 	err = register_netdev(dev);
 	if (err) {
 		dev_err(lan966x->dev, "register_netdev failed\n");
+		phylink_destroy(phylink);
+		port->phylink = NULL;
+		port->dev = NULL;
 		return err;
 	}