From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pablo Neira Ayuso Subject: Re: [PATCH] netfilter: nf_conntrack: don't release a conntrack with non-zero refcnt Date: Tue, 4 Feb 2014 11:21:43 +0100 Message-ID: <20140204102143.GA4711@localhost> References: <1391465397-3856-1-git-send-email-pablo@netfilter.org> <20140203232925.GA3695@breakpoint.cc> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netfilter-devel@vger.kernel.org, avagin@parallels.com, eric.dumazet@gmail.com To: Florian Westphal Return-path: Received: from mail.us.es ([193.147.175.20]:54287 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752859AbaBDKVx (ORCPT ); Tue, 4 Feb 2014 05:21:53 -0500 Content-Disposition: inline In-Reply-To: <20140203232925.GA3695@breakpoint.cc> Sender: netfilter-devel-owner@vger.kernel.org List-ID: On Tue, Feb 04, 2014 at 12:29:25AM +0100, Florian Westphal wrote: > Pablo Neira Ayuso wrote: > > diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c > > index 4d1fb5d..356bef5 100644 > > --- a/net/netfilter/nf_conntrack_core.c > > +++ b/net/netfilter/nf_conntrack_core.c > > @@ -448,7 +448,9 @@ nf_conntrack_hash_check_insert(struct nf_conn *ct) > > goto out; > > > > add_timer(&ct->timeout); > > - nf_conntrack_get(&ct->ct_general); > > + smp_wmb(); > > + /* The caller holds a reference to this object */ > > + atomic_set(&ct->ct_general.use, 2); > > What happens when the skb is dropped before confirmation? If you refer to the spot above, conntracks added via ctnetlink are always confirmed and the refcount will become 1 after insertion into the hashes. In the packet path, the refcount is 1 for unconfirmed conntracks, so if you release the skbuff, nf_conntrack_put() is called and the conntrack is also released (fulfilling that refcount equals 0). > How is skb_clone etc. solved (it increments refcnt of underlying > conntrack object?) I think this works as before, this patch is just delaying the initial refcount bumping to 1 to make it once the conntrack is inserted in any of the lists. Please, let me know if you still see any problematic case. Thanks.