Re: [PATCH net] net/packet: fix a race in packet_bind() and packet_notifier()

[Eric Dumazet <eric.dumazet@gmail.com>]

On Tue, 2017-11-28 at 09:48 -0500, David Miller wrote:
> From: Eric Dumazet <eric.dumazet@gmail.com>
> Date: Mon, 27 Nov 2017 20:00:52 -0800
> 
> > @@ -368,9 +368,11 @@ static void __unregister_prot_hook(struct sock
> *sk, bool sync)
> >       __sock_put(sk);
> >  
> >       if (sync) {
> > +             po->frozen = 1;
> >               spin_unlock(&po->bind_lock);
> >               synchronize_net();
> >               spin_lock(&po->bind_lock);
> > +             po->frozen = 0;
> >       }
> >  }
> >  
> 
> Ugh.
> 
> Maybe you can just set po->num to zero in the bind code path which
> causes
> this problem.  That will prevent this situation entirely.

Yes, I can submit a V2 with this idea implemented, thanks.