Re: Linux6.14-rc5: INFO: task hung in register_netdevice_notifier_net

[Kuniyuki Iwashima]

From: Stanislav Fomichev <stfomichev@xxxxxxxxx>
Date: Sun, 16 Mar 2025 09:54:27 -0700
> On 03/16, ffhgfv wrote:
> > Hello, I found a bug titled "   INFO: task hung in register_netdevice_notifier_net  " with modified syzkaller in the Linux6.14-rc5.
> > If you fix this issue, please add the following tag to the commit:  Reported-by: Jianzhou Zhao <xnxc22xnxc22@xxxxxx>,    xingwei lee <xrivendell7@xxxxxxxxx>, Zhizhuo Tang <strforexctzzchange@xxxxxxxxxxx>
> 
> Haven't looked that deep, but it seems to involve a tunneling device,
> so I wonder whether it's gonna be fixed by:
> - https://patchwork.kernel.org/project/netdevbpf/patch/20250312190513.1252045-2-sdf@xxxxxxxxxxx/
> - https://patchwork.kernel.org/project/netdevbpf/patch/20250312190513.1252045-3-sdf@xxxxxxxxxxx/
> 
> Do you have a repro? Can you rerun with the above fixes and enable
> lockdep?

It seems lockdep is enabled but doesn't report any locking bug,
so I think this report is generated simply because of RTNL storm by
syzkaller.

I have 200+ task hung reports due to RTNL on my syzkaller instances.

The tunnel part is ip_tunnel_init_net() that takes RTNL too for
register_netdevice().