RE: [PATCH net] hv_netvsc: fix race of netvsc and VF register_netdevice

[Haiyang Zhang]

> -----Original Message-----
> From: Wojciech Drewek <wojciech.drewek@xxxxxxxxx>
> Sent: Thursday, October 26, 2023 6:48 AM
> To: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; linux-hyperv@xxxxxxxxxxxxxxx;
> netdev@xxxxxxxxxxxxxxx
> Cc: KY Srinivasan <kys@xxxxxxxxxxxxx>; wei.liu@xxxxxxxxxx; Dexuan Cui
> <decui@xxxxxxxxxxxxx>; edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx;
> pabeni@xxxxxxxxxx; davem@xxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> stable@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH net] hv_netvsc: fix race of netvsc and VF
> register_netdevice
> 
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> 
> On 25.10.2023 23:16, Haiyang Zhang wrote:
> > The rtnl lock also needs to be held before rndis_filter_device_add()
> > which advertises nvsp_2_vsc_capability / sriov bit, and triggers
> > VF NIC offering and registering. If VF NIC finished register_netdev()
> > earlier it may cause name based config failure.
> >
> > To fix this issue, move the call to rtnl_lock() before
> > rndis_filter_device_add(), so VF will be registered later than netvsc
> > / synthetic NIC, and gets a name numbered (ethX) after netvsc.
> >
> > And, move register_netdevice_notifier() earlier, so the call back
> > function is set before probing.
> >
> > Cc: stable@xxxxxxxxxxxxxxx
> > Fixes: e04e7a7bbd4b ("hv_netvsc: Fix a deadlock by getting rtnl lock earlier
> in netvsc_probe()")
> > Signed-off-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> >
> > ---
> >  drivers/net/hyperv/netvsc_drv.c | 30 +++++++++++++++++++-----------
> >  1 file changed, 19 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/net/hyperv/netvsc_drv.c
> b/drivers/net/hyperv/netvsc_drv.c
> > index 3ba3c8fb28a5..feca1391f756 100644
> > --- a/drivers/net/hyperv/netvsc_drv.c
> > +++ b/drivers/net/hyperv/netvsc_drv.c
> > @@ -2531,15 +2531,6 @@ static int netvsc_probe(struct hv_device *dev,
> >               goto devinfo_failed;
> >       }
> >
> > -     nvdev = rndis_filter_device_add(dev, device_info);
> > -     if (IS_ERR(nvdev)) {
> > -             ret = PTR_ERR(nvdev);
> > -             netdev_err(net, "unable to add netvsc device (ret %d)\n", ret);
> > -             goto rndis_failed;
> > -     }
> > -
> > -     eth_hw_addr_set(net, device_info->mac_adr);
> > -
> >       /* We must get rtnl lock before scheduling nvdev->subchan_work,
> >        * otherwise netvsc_subchan_work() can get rtnl lock first and wait
> >        * all subchannels to show up, but that may not happen because
> > @@ -2547,9 +2538,23 @@ static int netvsc_probe(struct hv_device *dev,
> >        * -> ... -> device_add() -> ... -> __device_attach() can't get
> >        * the device lock, so all the subchannels can't be processed --
> >        * finally netvsc_subchan_work() hangs forever.
> > +      *
> > +      * The rtnl lock also needs to be held before rndis_filter_device_add()
> > +      * which advertises nvsp_2_vsc_capability / sriov bit, and triggers
> > +      * VF NIC offering and registering. If VF NIC finished register_netdev()
> > +      * earlier it may cause name based config failure.
> >        */
> >       rtnl_lock();
> >
> > +     nvdev = rndis_filter_device_add(dev, device_info);
> > +     if (IS_ERR(nvdev)) {
> > +             ret = PTR_ERR(nvdev);
> > +             netdev_err(net, "unable to add netvsc device (ret %d)\n", ret);
> > +             goto rndis_failed;
> 
> In case of error rtnl won't be unlocked.

Good catch! Will correct this. 

Thanks,
- Haiyang