Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755665AbaAFRVg (ORCPT ); Mon, 6 Jan 2014 12:21:36 -0500 Received: from mail-lb0-f169.google.com ([209.85.217.169]:45716 "EHLO mail-lb0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754608AbaAFRVe (ORCPT ); Mon, 6 Jan 2014 12:21:34 -0500 Date: Mon, 6 Jan 2014 21:21:30 +0400 From: Cyrill Gorcunov To: Florian Westphal Cc: Andrey Vagin , netfilter-devel@vger.kernel.org, netfilter@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, vvs@openvz.org, Pablo Neira Ayuso , Patrick McHardy , Jozsef Kadlecsik , "David S. Miller" Subject: Re: [PATCH] netfilter: nf_conntrack: release conntrack from rcu callback Message-ID: <20140106172130.GA2360@moon> References: <1389023672-14351-1-git-send-email-avagin@openvz.org> <20140106170235.GJ28854@breakpoint.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140106170235.GJ28854@breakpoint.cc> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 06, 2014 at 06:02:35PM +0100, Florian Westphal wrote: > > Can you elaborate? > Yes, nf_ct_is_dying(ct) might be called for the wrong conntrack. > > But, in case we _think_ that its the right one we call > nf_ct_tuple_equal() to verify we indeed found the right one: > > h = ____nf_conntrack_find(net, zone, tuple, hash); > if (h) { // might be released right now, but page won't go away (SLAB_BY_RCU) > ct = nf_ct_tuplehash_to_ctrack(h); > if (unlikely(nf_ct_is_dying(ct) || > !atomic_inc_not_zero(&ct->ct_general.use))) > // which means we should hit this path (0 ref). > h = NULL; > else { > // otherwise, it cannot go away from under us, since > // we own a reference now. > if (unlikely(!nf_ct_tuple_equal(tuple, &h->tuple) || > nf_ct_zone(ct) != zone)) { > // if we get here, the entry got recycled on other cpu > // for a different tuple, we can bail out and drop > // the reference safely and re-try the lookup > nf_ct_put(ct); > goto begin; > } > } I think tuple may match if task 1 task 2 task 3 nf_conntrack_find_get ____nf_conntrack_find destroy_conntrack hlist_nulls_del_rcu nf_conntrack_free kmem_cache_free __nf_conntrack_alloc kmem_cache_alloc if (nf_ct_is_dying(ct)) data is not yet cleaned memset(&ct->tuplehash[IP_CT_DIR_MAX], No? Or there something obvious I'm missing? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/