Re: [PATCH] usb: gadget: u_ether: refuse to re-register a failed net_device

[sashiko-bot@kernel.org]

> From: Nicholas Velten <nicholasfvelten@gmail.com>
> 
> When register_netdevice() fails in or after netdev_register_kobject(),
> it returns an error but leaves the net_device in NETREG_UNREGISTERED.
> Such a device can never be registered again; the only valid thing to do
> with it is free_netdev().
> 
> The configfs Ethernet functions (ECM, EEM, NCM, RNDIS and subset)
> allocate their net_device once per function instance and register it
> from the bind callback, retrying on every bind for as long as the device
> is not registered (formerly tracked by a "bound" flag, now by
> device_is_registered()). After a failed registration the next bind
> therefore calls register_netdev() on an NETREG_UNREGISTERED device and
> hits the BUG_ON() at the top of register_netdevice():
> 
> [ ... ]
> Fixes: 40d133d7f542 ("usb: gadget: f_ncm: convert to new function interface with backward compatibility")
> Reported-by: syzbot+85ede281798faf736677@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=85ede281798faf736677
> Assisted-by: Claude:claude-opus-5-5
> Signed-off-by: Nicholas Velten <nicholasfvelten@gmail.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20261014-fix-gadget-netdev-reregister-v1-1-0fb91999da06@gmail.com?part=1