On 20.06, Pablo Neira Ayuso wrote:
> On Fri, Jun 19, 2015 at 02:03:39PM -0500, Eric W. Biederman wrote:
> >
> > Add code to nf_unregister_hook to flush the nf_queue when a hook is
> > unregistered. This guarantees that the pointer that the nf_queue code
> > retains into the nf_hook list will remain valid while a packet is
> > queued.
>
> I think the real problem is that struct nf_queue_entry holds a pointer
> to struct nf_hook_ops, which will be gone after removal. So you
> uncovered a long standing problem that will amplify by when pernet
> hooks are in place.
>
> Regarding the pointer to nf_hook_list, now that new netdevice variant
> doesn't support nf_queue yet, so that nf_hook_list will be always
> valid since it will point to the global nf_hooks in the core.
I think Eric's patch is the right thing to do. I'm not sure I get
your netdev comment, but we certainly do want to drop packets once
a hook is gone.
> > +{
> > + const struct nf_queue_handler *qh;
> > + struct net *net;
> > +
> > + rtnl_lock();
>
> Why rtnl_lock() here?
for_each_net(). Would actually be nice to have a variant that doesn't
need the rtnl since it makes locking order analysis a lot harder.
> > + rcu_read_lock();
> > + qh = rcu_dereference(queue_handler);
> > + if (qh) {
> > + for_each_net(net) {
> > + qh->nf_hook_drop(net, ops);
> > + }
> > + }
> > + rcu_read_unlock();
> > + rtnl_unlock();
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