Re: [PATCH nf,v2] netfilter: nf_queue: don't re-enter same hook on packet reinjection

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Mon, Oct 17, 2016 at 03:29:27PM -0400, Aaron Conole wrote:
> Pablo Neira Ayuso <pablo@netfilter.org> writes:
[...]
> > From c1a731c68791bcd504a7fe5d28f5f0fd59d66118 Mon Sep 17 00:00:00 2001
> > From: Pablo Neira Ayuso <pablo@netfilter.org>
> > Date: Thu, 13 Oct 2016 08:14:03 +0200
> > Subject: [PATCH nf,v3] netfilter: nf_queue: don't re-enter same hook on packet
> >  reinjection
> >
> > If the packet is accepted, we have to skip the current hook from where
> > the packet was enqueued. Thus, we can emulate the previous
> > list_for_each_entry_continue() behaviour happening from nf_reinject(),
> > otherwise the packets gets enqueued over and over again.
> >
> > Fixes: e3b37f11e6e4 ("netfilter: replace list_head with single linked list")
> > Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
> > ---
> >  net/netfilter/nf_queue.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/net/netfilter/nf_queue.c b/net/netfilter/nf_queue.c
> > index 96964a0070e1..0b5ac3c9c2bc 100644
> > --- a/net/netfilter/nf_queue.c
> > +++ b/net/netfilter/nf_queue.c
> > @@ -187,8 +187,10 @@ void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
> >  	entry->state.thresh = INT_MIN;
> >  
> >  	if (verdict == NF_ACCEPT) {
> > -	next_hook:
> > -		verdict = nf_iterate(skb, &entry->state, &hook_entry);
> > +		hook_entry = rcu_dereference(hook_entry->next);
> > +		if (hook_entry)
> > +next_hook:
> 
> Should the above two lines be transposed to this?
> 
>  next_hook:
>  		if (hook_entry)
> 
> Sorry if I'm misunderstanding it.  Too many special cases for my tiny
> brain...

Right, my patch is still not correct.

I think this should be it:

        if (verdict == NF_ACCEPT) {
next_hook:
                hook_entry = rcu_dereference(hook_entry->next);
                if (hook_entry)
                        verdict = nf_iterate(skb, &entry->state, &hook_entry);

So we jump to "next_hook" in case of NF_QUEUE verdict with bypass flag
set on.  In that case, we need to continue just after the current hook
entry to emulate the behaviour that we previously have via
list_for_each_entry_continue().

This NF_QUEUE handling is also broken from nf_hook_slow() path, right?