linux-kernel - RE: [EXTERNAL] Re: [PATCH net] net: core: Fix the loop in default_device_exit

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Message-ID:
 <SJ2PR21MB401389FA98D182F16154E64ACA5CA@SJ2PR21MB4013.namprd21.prod.outlook.com>
Date: Tue, 22 Jul 2025 16:20:31 +0000
From: Haiyang Zhang <haiyangz@...rosoft.com>
To: Kuniyuki Iwashima <kuniyu@...gle.com>, Jakub Kicinski <kuba@...nel.org>
CC: Haiyang Zhang <haiyangz@...ux.microsoft.com>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>, KY Srinivasan
	<kys@...rosoft.com>, "wei.liu@...nel.org" <wei.liu@...nel.org>,
	"edumazet@...gle.com" <edumazet@...gle.com>, "pabeni@...hat.com"
	<pabeni@...hat.com>, "horms@...nel.org" <horms@...nel.org>,
	"davem@...emloft.net" <davem@...emloft.net>, "sdf@...ichev.me"
	<sdf@...ichev.me>, "ahmed.zaki@...el.com" <ahmed.zaki@...el.com>,
	"aleksander.lobakin@...el.com" <aleksander.lobakin@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [EXTERNAL] Re: [PATCH net] net: core: Fix the loop in
 default_device_exit_net()



> -----Original Message-----
> From: Kuniyuki Iwashima <kuniyu@...gle.com>
> Sent: Saturday, July 19, 2025 4:48 PM
> To: Jakub Kicinski <kuba@...nel.org>
> Cc: Haiyang Zhang <haiyangz@...ux.microsoft.com>; linux-
> hyperv@...r.kernel.org; netdev@...r.kernel.org; Haiyang Zhang
> <haiyangz@...rosoft.com>; KY Srinivasan <kys@...rosoft.com>;
> wei.liu@...nel.org; edumazet@...gle.com; pabeni@...hat.com;
> horms@...nel.org; davem@...emloft.net; sdf@...ichev.me;
> ahmed.zaki@...el.com; aleksander.lobakin@...el.com; linux-
> kernel@...r.kernel.org
> Subject: [EXTERNAL] Re: [PATCH net] net: core: Fix the loop in
> default_device_exit_net()
> 
> [You don't often get email from kuniyu@...gle.com. Learn why this is
> important at https://aka.ms/LearnAboutSenderIdentification ]
> 
> On Fri, Jul 18, 2025 at 4:37 PM Jakub Kicinski <kuba@...nel.org> 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