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

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Message-ID: <1511882095.16595.14.camel@gmail.com>
Date:   Tue, 28 Nov 2017 07:14:55 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, fruggeri@...stanetworks.com,
        willemb@...gle.com
Subject: Re: [PATCH net] net/packet: fix a race in packet_bind() and
 packet_notifier()

On Tue, 2017-11-28 at 09:48 -0500, David Miller wrote:
> From: Eric Dumazet <eric.dumazet@...il.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.