igc: Fix LED-related deadlock on driver unbind

Roman reports a deadlock on unplug of a Thunderbolt docking station
containing an Intel I225 Ethernet adapter.

The root cause is that led_classdev's for LEDs on the adapter are
registered such that they're device-managed by the netdev. That
results in recursive acquisition of the rtnl_lock() mutex on unplug:

When the driver calls unregister_netdev(), it acquires rtnl_lock(),
then frees the device-managed resources. Upon unregistering the LEDs,
netdev_trig_deactivate() invokes unregister_netdevice_notifier(),
which tries to acquire rtnl_lock() again.

Avoid by using non-device-managed LED registration.

Stack trace for posterity:

schedule+0x6e/0xf0
schedule_preempt_disabled+0x15/0x20
__mutex_lock+0x2a0/0x750
unregister_netdevice_notifier+0x40/0x150
netdev_trig_deactivate+0x1f/0x60 [ledtrig_netdev]
led_trigger_set+0x102/0x330
led_classdev_unregister+0x4b/0x110
release_nodes+0x3d/0xb0
devres_release_all+0x8b/0xc0
device_del+0x34f/0x3c0
unregister_netdevice_many_notify+0x80b/0xaf0
unregister_netdev+0x7c/0xd0
igc_remove+0xd8/0x1e0 [igc]
pci_device_remove+0x3f/0xb0

Fixes: ea578703b03d ("igc: Add support for LEDs on i225/i226")
Reported-by: Roman Lozko <[e-mail]>
Closes: https://lore.kernel.org/r/CAEhC_B=[e-mail]/
Reported-by: "Marek Marczykowski-Górecki" <[e-mail]>
Closes: https://lore.kernel.org/r/ZhRD3cOtz5i-61PB@mail-itl/
Signed-off-by: Kurt Kanzenbach <[e-mail]>
Signed-off-by: Lukas Wunner <[e-mail]>
Cc: Heiner Kallweit <[e-mail]>
Reviewed-by: Simon Horman <[e-mail]>
Reviewed-by: Kurt Kanzenbach <[e-mail]>
Tested-by: Kurt Kanzenbach <[e-mail]> # Intel i225
Tested-by: Naama Meir <[e-mail]>
Signed-off-by: Tony Nguyen <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/ethernet/intel/igc/igc.h

···
 
 	/* LEDs */
 	struct mutex led_mutex;
+	struct igc_led_classdev *leds;
 };
 
 void igc_up(struct igc_adapter *adapter);
···
 void igc_ptp_tx_tstamp_event(struct igc_adapter *adapter);
 
 int igc_led_setup(struct igc_adapter *adapter);
+void igc_led_free(struct igc_adapter *adapter);
 
 #define igc_rx_pg_size(_ring) (PAGE_SIZE << igc_rx_pg_order(_ring))
 

drivers/net/ethernet/intel/igc/igc_leds.c

···
 		 pci_dev_id(adapter->pdev), index);
 }
 
-static void igc_setup_ldev(struct igc_led_classdev *ldev,
-			   struct net_device *netdev, int index)
+static int igc_setup_ldev(struct igc_led_classdev *ldev,
+			  struct net_device *netdev, int index)
 {
 	struct igc_adapter *adapter = netdev_priv(netdev);
 	struct led_classdev *led_cdev = &ldev->led;
···
 	led_cdev->hw_control_get = igc_led_hw_control_get;
 	led_cdev->hw_control_get_device = igc_led_hw_control_get_device;
 
-	devm_led_classdev_register(&netdev->dev, led_cdev);
+	return led_classdev_register(&netdev->dev, led_cdev);
 }
 
 int igc_led_setup(struct igc_adapter *adapter)
 {
 	struct net_device *netdev = adapter->netdev;
-	struct device *dev = &netdev->dev;
 	struct igc_led_classdev *leds;
-	int i;
+	int i, err;
 
 	mutex_init(&adapter->led_mutex);
 
-	leds = devm_kcalloc(dev, IGC_NUM_LEDS, sizeof(*leds), GFP_KERNEL);
+	leds = kcalloc(IGC_NUM_LEDS, sizeof(*leds), GFP_KERNEL);
 	if (!leds)
 		return -ENOMEM;
 
-	for (i = 0; i < IGC_NUM_LEDS; i++)
-		igc_setup_ldev(leds + i, netdev, i);
+	for (i = 0; i < IGC_NUM_LEDS; i++) {
+		err = igc_setup_ldev(leds + i, netdev, i);
+		if (err)
+			goto err;
+	}
+
+	adapter->leds = leds;
 
 	return 0;
+
+err:
+	for (i--; i >= 0; i--)
+		led_classdev_unregister(&((leds + i)->led));
+
+	kfree(leds);
+	return err;
+}
+
+void igc_led_free(struct igc_adapter *adapter)
+{
+	struct igc_led_classdev *leds = adapter->leds;
+	int i;
+
+	for (i = 0; i < IGC_NUM_LEDS; i++)
+		led_classdev_unregister(&((leds + i)->led));
+
+	kfree(leds);
 }

drivers/net/ethernet/intel/igc/igc_main.c

···
 	cancel_work_sync(&adapter->watchdog_task);
 	hrtimer_cancel(&adapter->hrtimer);
 
+	if (IS_ENABLED(CONFIG_IGC_LEDS))
+		igc_led_free(adapter);
+
 	/* Release control of h/w to f/w.  If f/w is AMT enabled, this
 	 * would have already happened in close and is redundant.
 	 */