kernel panic in fec network driver on iMX6ULL

[dallasfoley]

I'm currently seeing kernel panics in the fec driver when configuring and re-configuring my network with netplan.io in ubuntu.

I'm seeing this on our own hardware as well as the iMX6ULL EVK. The kernel version is 4.14.98. I've also tried using 5.4 from git://git.kernel.org/pub/scm/linux/kernel/git/shawnguo/linux.git.

I noticed the panic happens when unbinding and then binding the device to the driver, which netplan.io seems to by running strace.

eg. running the following commands can cause the kernel panic.

~# echo -n "20b4000.ethernet" > /sys/bus/platform/drivers/fec/ubind
~# echo -n "20b4000.ethernet" > /sys/bus/platform/drivers/fec/bind

[igorpadykov]

Hi Dallas

nxp does not support netplan on its linux releases, issue may be posted

on netplan wiki: https://launchpad.net/netplan/+filebug 

Best regards
igor
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[dallasfoley]

It's the unbinding/binding from sysfs that exposes the bug in the driver.

[fabio_estevam]

Hi Dallas,

Performing unbind/bind operation on the FEC driver is not safe. Please check the details in this commit where I disable the unbind operation in the driver:

kernel/git/netdev/net-next.git - David Miller's -next networking tree 

You can still build the FEC driver as module and load/unload it.

Regards,

Fabio Estevam

[dallasfoley]

Thanks Fabio, I've applied the patch and now blocks unbinding the driver. It looks like netplan.io is aware of SOC's that don't support network driver unbinding.

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