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=unavailable 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 D8ECBC00454 for ; Mon, 9 Dec 2019 19:26:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B5B2320726 for ; Mon, 9 Dec 2019 19:26:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726826AbfLIT0u (ORCPT ); Mon, 9 Dec 2019 14:26:50 -0500 Received: from correo.us.es ([193.147.175.20]:58454 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726589AbfLIT0t (ORCPT ); Mon, 9 Dec 2019 14:26:49 -0500 Received: from antivirus1-rhel7.int (unknown [192.168.2.11]) by mail.us.es (Postfix) with ESMTP id 702DF12084B for ; Mon, 9 Dec 2019 20:26:46 +0100 (CET) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 63EEEDA70E for ; Mon, 9 Dec 2019 20:26:46 +0100 (CET) Received: by antivirus1-rhel7.int (Postfix, from userid 99) id 598CCDA70C; Mon, 9 Dec 2019 20:26:46 +0100 (CET) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 4BB82DA707; Mon, 9 Dec 2019 20:26:44 +0100 (CET) Received: from 192.168.1.97 (192.168.1.97) by antivirus1-rhel7.int (F-Secure/fsigk_smtp/550/antivirus1-rhel7.int); Mon, 09 Dec 2019 20:26:44 +0100 (CET) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/antivirus1-rhel7.int) Received: from salvia.here (sys.soleta.eu [212.170.55.40]) (Authenticated sender: pneira@us.es) by entrada.int (Postfix) with ESMTPA id 1BFF54265A5A; Mon, 9 Dec 2019 20:26:44 +0100 (CET) X-SMTPAUTHUS: auth mail.us.es From: Pablo Neira Ayuso To: netfilter-devel@vger.kernel.org Cc: davem@davemloft.net, netdev@vger.kernel.org Subject: [PATCH 01/17] netfilter: ctnetlink: netns exit must wait for callbacks Date: Mon, 9 Dec 2019 20:26:22 +0100 Message-Id: <20191209192638.71184-2-pablo@netfilter.org> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20191209192638.71184-1-pablo@netfilter.org> References: <20191209192638.71184-1-pablo@netfilter.org> X-Virus-Scanned: ClamAV using ClamSMTP Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org From: Florian Westphal Curtis Taylor and Jon Maxwell reported and debugged a crash on 3.10 based kernel. Crash occurs in ctnetlink_conntrack_events because net->nfnl socket is NULL. The nfnl socket was set to NULL by netns destruction running on another cpu. The exiting network namespace calls the relevant destructors in the following order: 1. ctnetlink_net_exit_batch This nulls out the event callback pointer in struct netns. 2. nfnetlink_net_exit_batch This nulls net->nfnl socket and frees it. 3. nf_conntrack_cleanup_net_list This removes all remaining conntrack entries. This is order is correct. The only explanation for the crash so ar is: cpu1: conntrack is dying, eviction occurs: -> nf_ct_delete() -> nf_conntrack_event_report \ -> nf_conntrack_eventmask_report -> notify->fcn() (== ctnetlink_conntrack_events). cpu1: a. fetches rcu protected pointer to obtain ctnetlink event callback. b. gets interrupted. cpu2: runs netns exit handlers: a runs ctnetlink destructor, event cb pointer set to NULL. b runs nfnetlink destructor, nfnl socket is closed and set to NULL. cpu1: c. resumes and trips over NULL net->nfnl. Problem appears to be that ctnetlink_net_exit_batch only prevents future callers of nf_conntrack_eventmask_report() from obtaining the callback. It doesn't wait of other cpus that might have already obtained the callbacks address. I don't see anything in upstream kernels that would prevent similar crash: We need to wait for all cpus to have exited the event callback. Fixes: 9592a5c01e79dbc59eb56fa ("netfilter: ctnetlink: netns support") Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nf_conntrack_netlink.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c index d8d33ef52ce0..6a1c8f1f6171 100644 --- a/net/netfilter/nf_conntrack_netlink.c +++ b/net/netfilter/nf_conntrack_netlink.c @@ -3626,6 +3626,9 @@ static void __net_exit ctnetlink_net_exit_batch(struct list_head *net_exit_list) list_for_each_entry(net, net_exit_list, exit_list) ctnetlink_net_exit(net); + + /* wait for other cpus until they are done with ctnl_notifiers */ + synchronize_rcu(); } static struct pernet_operations ctnetlink_net_ops = { -- 2.11.0