On Mon, 22 Jun 2020 12:00:48 +0200 Bartosz Golaszewski wrote:

From: Bartosz Golaszewski <redacted>

This devres helper registers a release callback that only unregisters
the net_device. It works perfectly fine with netdev structs that are
not managed on their own. There's no reason to check this - drop the
warning.

Signed-off-by: Bartosz Golaszewski <redacted>

I think the reasoning for this suggestion was to catch possible UAF
errors. The netdev doesn't necessarily has to be from devm_alloc_* 
but it has to be part of devm-ed memory or memory which is freed 
after driver's remove callback.

Are there cases in practice where you've seen the netdev not being
devm allocated?