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=-9.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 AC747C76197 for ; Fri, 19 Jul 2019 16:45:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 900562186A for ; Fri, 19 Jul 2019 16:45:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731873AbfGSQpc (ORCPT ); Fri, 19 Jul 2019 12:45:32 -0400 Received: from mail.us.es ([193.147.175.20]:49420 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728449AbfGSQpb (ORCPT ); Fri, 19 Jul 2019 12:45:31 -0400 Received: from antivirus1-rhel7.int (unknown [192.168.2.11]) by mail.us.es (Postfix) with ESMTP id CA44CBAEE2 for ; Fri, 19 Jul 2019 18:45:29 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id A921DDA704 for ; Fri, 19 Jul 2019 18:45:29 +0200 (CEST) Received: by antivirus1-rhel7.int (Postfix, from userid 99) id 9D853115107; Fri, 19 Jul 2019 18:45:29 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id DBE84DA704; Fri, 19 Jul 2019 18:45:24 +0200 (CEST) Received: from 192.168.1.97 (192.168.1.97) by antivirus1-rhel7.int (F-Secure/fsigk_smtp/550/antivirus1-rhel7.int); Fri, 19 Jul 2019 18:45:24 +0200 (CEST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/antivirus1-rhel7.int) Received: from salvia.here (unknown [47.60.47.94]) (Authenticated sender: pneira@us.es) by entrada.int (Postfix) with ESMTPA id 5CF0340705C4; Fri, 19 Jul 2019 18:45:24 +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 01/14] netfilter: nfnetlink: avoid deadlock due to synchronous request_module Date: Fri, 19 Jul 2019 18:45:04 +0200 Message-Id: <20190719164517.29496-2-pablo@netfilter.org> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20190719164517.29496-1-pablo@netfilter.org> References: <20190719164517.29496-1-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 Thomas and Juliana report a deadlock when running: (rmmod nf_conntrack_netlink/xfrm_user) conntrack -e NEW -E & modprobe -v xfrm_user They provided following analysis: conntrack -e NEW -E netlink_bind() netlink_lock_table() -> increases "nl_table_users" nfnetlink_bind() # does not unlock the table as it's locked by netlink_bind() __request_module() call_usermodehelper_exec() This triggers "modprobe nf_conntrack_netlink" from kernel, netlink_bind() won't return until modprobe process is done. "modprobe xfrm_user": xfrm_user_init() register_pernet_subsys() -> grab pernet_ops_rwsem .. netlink_table_grab() calls schedule() as "nl_table_users" is non-zero so modprobe is blocked because netlink_bind() increased nl_table_users while also holding pernet_ops_rwsem. "modprobe nf_conntrack_netlink" runs and inits nf_conntrack_netlink: ctnetlink_init() register_pernet_subsys() -> blocks on "pernet_ops_rwsem" thanks to xfrm_user module both modprobe processes wait on one another -- neither can make progress. Switch netlink_bind() to "nowait" modprobe -- this releases the netlink table lock, which then allows both modprobe instances to complete. Reported-by: Thomas Jarosch Reported-by: Juliana Rodrigueiro Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nfnetlink.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c index 92077d459109..4abbb452cf6c 100644 --- a/net/netfilter/nfnetlink.c +++ b/net/netfilter/nfnetlink.c @@ -578,7 +578,7 @@ static int nfnetlink_bind(struct net *net, int group) ss = nfnetlink_get_subsys(type << 8); rcu_read_unlock(); if (!ss) - request_module("nfnetlink-subsys-%d", type); + request_module_nowait("nfnetlink-subsys-%d", type); return 0; } #endif -- 2.11.0