[PATCH v3] 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. The common cleanup path now skips
ports without port->dev before reaching the registered netdev cleanup, so
it only handles ports that reached the registered-netdev lifetime.

This also avoids treating an uninitialized FDMA netdev and the failed port
as a NULL == NULL match in the common cleanup path.

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 v3:
- Make lan966x_cleanup_ports() skip ports without port->dev, so the
  common cleanup path does not run registered-netdev, XDP, FDMA, or
  phylink cleanup for a port whose netdev registration failed.
- Keep the register_netdev() failure path responsible for destroying the
  newly created phylink and clearing port->dev before returning.

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 | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_main.c b/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
index 47752d3fde..1179a6e127 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
@@ -749,11 +749,10 @@ static void lan966x_cleanup_ports(struct lan966x *lan966x)
 
 	for (p = 0; p < lan966x->num_phys_ports; p++) {
 		port = lan966x->ports[p];
-		if (!port)
+		if (!port || !port->dev)
 			continue;
 
-		if (port->dev)
-			unregister_netdev(port->dev);
+		unregister_netdev(port->dev);
 
 		lan966x_xdp_port_deinit(port);
 		if (lan966x->fdma && lan966x->fdma_ndev == port->dev)
@@ -873,6 +872,9 @@ 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;
 	}