From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 76D2BC38A2A for ; Sun, 10 May 2020 12:28:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5D48D2082E for ; Sun, 10 May 2020 12:28:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728907AbgEJM2R (ORCPT ); Sun, 10 May 2020 08:28:17 -0400 Received: from Chamillionaire.breakpoint.cc ([193.142.43.52]:39672 "EHLO Chamillionaire.breakpoint.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726863AbgEJM2Q (ORCPT ); Sun, 10 May 2020 08:28:16 -0400 Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1jXl3z-00061G-GI; Sun, 10 May 2020 14:28:11 +0200 From: Florian Westphal To: Subject: [PATCH nf] netfilter: conntrack: fix infinite loop on rmmod Date: Sun, 10 May 2020 14:28:07 +0200 Message-Id: <20200510122807.24011-1-fw@strlen.de> X-Mailer: git-send-email 2.26.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org 'rmmod nf_conntrack' can hang forever, because the netns exit gets stuck in nf_conntrack_cleanup_net_list(): i_see_dead_people: busy = 0; list_for_each_entry(net, net_exit_list, exit_list) { nf_ct_iterate_cleanup(kill_all, net, 0, 0); if (atomic_read(&net->ct.count) != 0) busy = 1; } if (busy) { schedule(); goto i_see_dead_people; } When nf_ct_iterate_cleanup iterates the conntrack table, all nf_conn structures can be found twice: once for the original tuple and once for the conntracks reply tuple. get_next_corpse() only calls the iterator when the entry is in original direction -- the idea was to avoid unneeded invocations of the iterator callback. When support for clashing entries was added, the assumption that all nf_conn objects are added twice, once in original, once for reply tuple no longer holds -- NF_CLASH_BIT entries are only added in the non-clashing reply direction. Thus, if at least one NF_CLASH entry is in the list then nf_conntrack_cleanup_net_list() always skips it completely. During normal netns destruction, this causes a hang of several seconds, until the gc worker removes the entry (NF_CLASH entries always have a 1 second timeout). But in the rmmod case, the gc worker has already been stopped, so ct.count never becomes 0. We can fix this in two ways: 1. Add a second test for CLASH_BIT and call iterator for those entries as well, or: 2. Skip the original tuple direction and use the reply tuple. 2) is simpler, so do that. Fixes: 6a757c07e51f80ac ("netfilter: conntrack: allow insertion of clashing entries") Reported-by: Chen Yi Signed-off-by: Florian Westphal --- net/netfilter/nf_conntrack_core.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c index c4582eb71766..8cbce1159a91 100644 --- a/net/netfilter/nf_conntrack_core.c +++ b/net/netfilter/nf_conntrack_core.c @@ -2139,8 +2139,19 @@ get_next_corpse(int (*iter)(struct nf_conn *i, void *data), nf_conntrack_lock(lockp); if (*bucket < nf_conntrack_htable_size) { hlist_nulls_for_each_entry(h, n, &nf_conntrack_hash[*bucket], hnnode) { - if (NF_CT_DIRECTION(h) != IP_CT_DIR_ORIGINAL) + if (NF_CT_DIRECTION(h) != IP_CT_DIR_REPLY) continue; + /* All nf_conn objects are added to hash table twice, one + * for original direction tuple, once for the reply tuple. + * + * Exception: In the IPS_NAT_CLASH case, only the reply + * tuple is added (the original tuple already existed for + * a different object). + * + * We only need to call the iterator once for each + * conntrack, so we just use the 'reply' direction + * tuple while iterating. + */ ct = nf_ct_tuplehash_to_ctrack(h); if (iter(ct, data)) goto found; -- 2.26.2