RE: [EXTERNAL] Re: [PATCH net] net: core: Fix the loop in default_device_exit_net()

[Haiyang Zhang]

> -----Original Message-----
> From: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
> Sent: Saturday, July 19, 2025 4:48 PM
> To: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxxxxxxxx>; linux-
> hyperv@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; Haiyang Zhang
> <haiyangz@xxxxxxxxxxxxx>; KY Srinivasan <kys@xxxxxxxxxxxxx>;
> wei.liu@xxxxxxxxxx; edumazet@xxxxxxxxxx; pabeni@xxxxxxxxxx;
> horms@xxxxxxxxxx; davem@xxxxxxxxxxxxx; sdf@xxxxxxxxxxx;
> ahmed.zaki@xxxxxxxxx; aleksander.lobakin@xxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx
> Subject: [EXTERNAL] Re: [PATCH net] net: core: Fix the loop in
> default_device_exit_net()
> 
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> 
> On Fri, Jul 18, 2025 at 4:37 PM Jakub Kicinski <kuba@xxxxxxxxxx> wrote:
> >
> > On Fri, 18 Jul 2025 13:20:14 -0700 Haiyang Zhang wrote:
> > > The loop in default_device_exit_net() won't be able to properly detect
> the
> > > head then stop, and will hit NULL pointer, when a driver, like
> hv_netvsc,
> > > automatically moves the slave device together with the master device.
> > >
> > > To fix this, add a helper function to return the first migratable
> netdev
> > > correctly, no matter one or two devices were removed from this net's
> list
> > > in the last iteration.
> >
> > FTR I think that what the driver is trying to do is way too hacky, and
> > it should be fixed instead. But I defer to Kuniyuki for the final word,
> > maybe this change is useful for other reasons..
> 
> I agree that it should be fixed on the driver side.  I don't
> think of a good reason for the change.

Kuniyuki and Jakub:

Thanks for the reviews. I'm working on a patch that will fix the driver side.

- Haiyang