igc: don't fail igc_probe() on LED setup error

When igc_led_setup() fails, igc_probe() fails and triggers kernel panic
in free_netdev() since unregister_netdev() is not called. [1]
This behavior can be tested using fault-injection framework, especially
the failslab feature. [2]

Since LED support is not mandatory, treat LED setup failures as
non-fatal and continue probe with a warning message, consequently
avoiding the kernel panic.

[1]
 kernel BUG at net/core/dev.c:12047!
 Oops: invalid opcode: 0000 [#1] SMP NOPTI
 CPU: 0 UID: 0 PID: 937 Comm: repro-igc-led-e Not tainted 6.17.0-rc4-enjuk-tnguy-00865-gc4940196ab02 #64 PREEMPT(voluntary)
 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
 RIP: 0010:free_netdev+0x278/0x2b0
 [...]
 Call Trace:
  <TASK>
  igc_probe+0x370/0x910
  local_pci_probe+0x3a/0x80
  pci_device_probe+0xd1/0x200
 [...]

[2]
 #!/bin/bash -ex

 FAILSLAB_PATH=/sys/kernel/debug/failslab/
 DEVICE=0000:00:05.0
 START_ADDR=$(grep " igc_led_setup" /proc/kallsyms \
         | awk '{printf("0x%s", $1)}')
 END_ADDR=$(printf "0x%x" $((START_ADDR + 0x100)))

 echo $START_ADDR > $FAILSLAB_PATH/require-start
 echo $END_ADDR > $FAILSLAB_PATH/require-end
 echo 1 > $FAILSLAB_PATH/times
 echo 100 > $FAILSLAB_PATH/probability
 echo N > $FAILSLAB_PATH/ignore-gfp-wait

 echo $DEVICE > /sys/bus/pci/drivers/igc/bind

Fixes: ea57870 ("igc: Add support for LEDs on i225/i226")
Signed-off-by: Kohei Enju <enjuk@amazon.com>
Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Reviewed-by: Vitaly Lifshits <vitaly.lifshits@intel.com>
Reviewed-by: Kurt Kanzenbach <kurt@linutronix.de>
Tested-by: Mor Bar-Gabay <morx.bar.gabay@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

Author: hyperenju

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

@@ -345,6 +345,7 @@ struct igc_adapter {
 	/* LEDs */
 	struct mutex led_mutex;
 	struct igc_led_classdev *leds;
+	bool leds_available;
 };
 
 void igc_up(struct igc_adapter *adapter);

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

@@ -7335,8 +7335,14 @@ static int igc_probe(struct pci_dev *pdev,
 
 	if (IS_ENABLED(CONFIG_IGC_LEDS)) {
 		err = igc_led_setup(adapter);
-		if (err)
-			goto err_register;
+		if (err) {
+			netdev_warn_once(netdev,
+					 "LED init failed (%d); continuing without LED support\n",
+					 err);
+			adapter->leds_available = false;
+		} else {
+			adapter->leds_available = true;
+		}
 	}
 
 	return 0;
@@ -7392,7 +7398,7 @@ static void igc_remove(struct pci_dev *pdev)
 	cancel_work_sync(&adapter->watchdog_task);
 	hrtimer_cancel(&adapter->hrtimer);
 
-	if (IS_ENABLED(CONFIG_IGC_LEDS))
+	if (IS_ENABLED(CONFIG_IGC_LEDS) && adapter->leds_available)
 		igc_led_free(adapter);
 
 	/* Release control of h/w to f/w.  If f/w is AMT enabled, this