netdev - Re: [Intel-wired-lan] [PATCH v1 iwl-net] igc: unregister netdev when igc_led_setup() fails in igc

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Message-ID: <15453ddf-0854-4be6-9eed-017ef79d3c77@intel.com>
Date: Wed, 10 Sep 2025 10:28:17 +0300
From: "Lifshits, Vitaly" <vitaly.lifshits@...el.com>
To: Kurt Kanzenbach <kurt@...utronix.de>, Kohei Enju <enjuk@...zon.com>,
	<intel-wired-lan@...ts.osuosl.org>, <netdev@...r.kernel.org>
CC: Tony Nguyen <anthony.l.nguyen@...el.com>, Przemek Kitszel
	<przemyslaw.kitszel@...el.com>, Andrew Lunn <andrew+netdev@...n.ch>, "David
 S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, "Jakub
 Kicinski" <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	<kohei.enju@...il.com>
Subject: Re: [Intel-wired-lan] [PATCH v1 iwl-net] igc: unregister netdev when
 igc_led_setup() fails in igc_probe()

On 9/8/2025 9:26 AM, Kurt Kanzenbach wrote:
> On Sat Sep 06 2025, Kohei Enju wrote:
>> Currently igc_probe() doesn't unregister netdev when igc_led_setup()
>> fails, causing BUG_ON() in free_netdev() and then kernel panics. [1]
>>
>> This behavior can be tested using fault-injection framework. I used the
>> failslab feature to test the issue. [2]
>>
>> Call unregister_netdev() when igc_led_setup() fails to avoid 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: ea578703b03d ("igc: Add support for LEDs on i225/i226")
>> Signed-off-by: Kohei Enju <enjuk@...zon.com>
> 
> Reviewed-by: Kurt Kanzenbach <kurt@...utronix.de>

Thank you for the patch and for identifying this issue!

I was wondering whether we could avoid failing the probe in cases where 
igc_led_setup fails. It seems to me that a failure in the LED class 
functionality shouldn't prevent the device's core functionality from 
working properly.

 From what I understand, errors in this function are not due to hardware 
malfunctions. Therefore, I suggest we remove the error propagation.

Alternatively, if feasible, we could consider reordering the function 
calls so that the LED class setup occurs before the netdev registration.