Re: [PATCH rdma-next V1 5/9] IB/ipoib: rtnl_unlock can not come after free_netdev

[Leon Romanovsky <leonro-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>]

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On Thu, Dec 29, 2016 at 10:55:34PM +0200, Or Gerlitz wrote:
> On Wed, Dec 28, 2016 at 2:47 PM, Leon Romanovsky <leon-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> wrote:
> > From: Feras Daoud <ferasda-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
> >
> > The ipoib_vlan_add function calls rtnl_unlock after free_netdev,
> > rtnl_unlock not only releases the lock, but also calls netdev_run_todo.
> > The latter function browses the net_todo_list array and completes the
> > unregistration of all its net_device instances. If we call free_netdev
> > before rtnl_unlock, then netdev_run_todo call over the freed device causes
> > panic.
>
>
> RU claiming that we are crashing 100.0% here? since when? ever?

According to our internal bugtracker (see #131352), this bug was
literaly forever (4 years old), and it was fixed internaly in
MOFED 2.0.

>
> > To fix, move rtnl_unlock call before free_netdev call.
> >
> > Fixes: 9baa0b036410 ("IB/ipoib: Add rtnl_link_ops support")
> > Cc: Or Gerlitz <ogerlitz-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
>
> > diff --git a/drivers/infiniband/ulp/ipoib/ipoib_vlan.c b/drivers/infiniband/ulp/ipoib/ipoib_vlan.c
> > index 9682183..d9dab4a 100644
> > --- a/drivers/infiniband/ulp/ipoib/ipoib_vlan.c
> > +++ b/drivers/infiniband/ulp/ipoib/ipoib_vlan.c
> > @@ -168,11 +168,11 @@ int ipoib_vlan_add(struct net_device *pdev, unsigned short pkey)
> >  out:
> >         up_write(&ppriv->vlan_rwsem);
> >
> > +       rtnl_unlock();
> > +
> >         if (result)
> >                 free_netdev(priv->dev);
> >
> > -       rtnl_unlock();
> > -
> >         return result;
> >  }
> --
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