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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 04B91C433FF for ; Fri, 2 Aug 2019 13:20:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D1570216C8 for ; Fri, 2 Aug 2019 13:19:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564751999; bh=nUdfbhfIQrSghXscbJC5+DYXbBibO3UhUhJIbYLvPp0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=IH2Igdy2L58CfzCLe6R/YyBp9XI7FBdM+fnTgDkUT1rH1DgB9I1mixeEnAsgbXZxT mRZ5UkoPqJvw3nu92yri6iCGs/d3Xyo/ynzUz2o0qzpl+gS8Lq6+LBOSuHFVKtpjRR 35b4NPAQ/u7meqXUySS4wlm3/JrWieLLVONRiY0s= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732785AbfHBNT6 (ORCPT ); Fri, 2 Aug 2019 09:19:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:58188 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2393219AbfHBNTz (ORCPT ); Fri, 2 Aug 2019 09:19:55 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A8D6D2173E; Fri, 2 Aug 2019 13:19:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564751994; bh=nUdfbhfIQrSghXscbJC5+DYXbBibO3UhUhJIbYLvPp0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Dr6P3OuRq961fC8OsY45tXvhfBE8NiYpURE9AsA8rg1xDQG+dkbKpPZ0yNZ+neQFP vNqBKpMDSbKPpn5PiAPdwwI/iJW2wBYiWjn4hddWke5G+8fsPdrycWw3ucc9vc3zGY IhyRsOXWJcrHiOU82c7Fd9aEhqAPx/Rz8EbdGsNc= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Florian Westphal , Thomas Jarosch , Juliana Rodrigueiro , Pablo Neira Ayuso , Sasha Levin , netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org Subject: [PATCH AUTOSEL 5.2 02/76] netfilter: nfnetlink: avoid deadlock due to synchronous request_module Date: Fri, 2 Aug 2019 09:18:36 -0400 Message-Id: <20190802131951.11600-2-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190802131951.11600-1-sashal@kernel.org> References: <20190802131951.11600-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Florian Westphal [ Upstream commit 1b0890cd60829bd51455dc5ad689ed58c4408227 ] 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 Signed-off-by: Sasha Levin --- 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 92077d4591090..4abbb452cf6c6 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 -- 2.20.1