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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 011B4C04AB1 for ; Mon, 13 May 2019 09:57:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D0F3E20989 for ; Mon, 13 May 2019 09:57:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728836AbfEMJ5K (ORCPT ); Mon, 13 May 2019 05:57:10 -0400 Received: from mail.us.es ([193.147.175.20]:34232 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728721AbfEMJ4n (ORCPT ); Mon, 13 May 2019 05:56:43 -0400 Received: from antivirus1-rhel7.int (unknown [192.168.2.11]) by mail.us.es (Postfix) with ESMTP id 9BA23DA737 for ; Mon, 13 May 2019 11:56:41 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 8CBB3DA706 for ; Mon, 13 May 2019 11:56:41 +0200 (CEST) Received: by antivirus1-rhel7.int (Postfix, from userid 99) id 73D94DA70C; Mon, 13 May 2019 11:56:41 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 5D827DA7A5; Mon, 13 May 2019 11:56:39 +0200 (CEST) Received: from 192.168.1.97 (192.168.1.97) by antivirus1-rhel7.int (F-Secure/fsigk_smtp/550/antivirus1-rhel7.int); Mon, 13 May 2019 11:56:39 +0200 (CEST) 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 2F0324265A32; Mon, 13 May 2019 11:56:39 +0200 (CEST) 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 06/13] netfilter: nf_tables: fix base chain stat rcu_dereference usage Date: Mon, 13 May 2019 11:56:23 +0200 Message-Id: <20190513095630.32443-7-pablo@netfilter.org> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20190513095630.32443-1-pablo@netfilter.org> References: <20190513095630.32443-1-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 Following splat gets triggered when nfnetlink monitor is running while xtables-nft selftests are running: net/netfilter/nf_tables_api.c:1272 suspicious rcu_dereference_check() usage! other info that might help us debug this: 1 lock held by xtables-nft-mul/27006: #0: 00000000e0f85be9 (&net->nft.commit_mutex){+.+.}, at: nf_tables_valid_genid+0x1a/0x50 Call Trace: nf_tables_fill_chain_info.isra.45+0x6cc/0x6e0 nf_tables_chain_notify+0xf8/0x1a0 nf_tables_commit+0x165c/0x1740 nf_tables_fill_chain_info() can be called both from dumps (rcu read locked) or from the transaction path if a userspace process subscribed to nftables notifications. In the 'table dump' case, rcu_access_pointer() cannot be used: We do not hold transaction mutex so the pointer can be NULLed right after the check. Just unconditionally fetch the value, then have the helper return immediately if its NULL. In the notification case we don't hold the rcu read lock, but updates are prevented due to transaction mutex. Use rcu_dereference_check() to make lockdep aware of this. Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nf_tables_api.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c index f2e12ae50544..e4f6ecac48c3 100644 --- a/net/netfilter/nf_tables_api.c +++ b/net/netfilter/nf_tables_api.c @@ -1190,6 +1190,9 @@ static int nft_dump_stats(struct sk_buff *skb, struct nft_stats __percpu *stats) u64 pkts, bytes; int cpu; + if (!stats) + return 0; + memset(&total, 0, sizeof(total)); for_each_possible_cpu(cpu) { cpu_stats = per_cpu_ptr(stats, cpu); @@ -1247,6 +1250,7 @@ static int nf_tables_fill_chain_info(struct sk_buff *skb, struct net *net, if (nft_is_base_chain(chain)) { const struct nft_base_chain *basechain = nft_base_chain(chain); const struct nf_hook_ops *ops = &basechain->ops; + struct nft_stats __percpu *stats; struct nlattr *nest; nest = nla_nest_start(skb, NFTA_CHAIN_HOOK); @@ -1268,8 +1272,9 @@ static int nf_tables_fill_chain_info(struct sk_buff *skb, struct net *net, if (nla_put_string(skb, NFTA_CHAIN_TYPE, basechain->type->name)) goto nla_put_failure; - if (rcu_access_pointer(basechain->stats) && - nft_dump_stats(skb, rcu_dereference(basechain->stats))) + stats = rcu_dereference_check(basechain->stats, + lockdep_commit_lock_is_held(net)); + if (nft_dump_stats(skb, stats)) goto nla_put_failure; } -- 2.11.0