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=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 F06D3C32750 for ; Fri, 2 Aug 2019 13:25:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C33D4217D4 for ; Fri, 2 Aug 2019 13:25:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564752355; bh=tlx84D8sSjVoacLkk/cR5dKVIyxX5S11HGCogWBGsu8=; h=From:To:Cc:Subject:Date:List-ID:From; b=YGhLUf/iUSuORwojJxG1wtSDC1QhCkP1Yb/OIJR/VA4ZJzvWYQfbYZWs9/nodgvWt 4mqid/KYp4iO8kT0MjnPQO0L3jxHcJujNFbNlkDATbrtXnHWx94/DDQ217oaVK8FNd WitPCDkZzqzjo6fy8YxRGujx29EKLk05id+Bi594= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2394446AbfHBNZy (ORCPT ); Fri, 2 Aug 2019 09:25:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:36538 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390633AbfHBNZt (ORCPT ); Fri, 2 Aug 2019 09:25:49 -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 412A921850; Fri, 2 Aug 2019 13:25:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564752349; bh=tlx84D8sSjVoacLkk/cR5dKVIyxX5S11HGCogWBGsu8=; h=From:To:Cc:Subject:Date:From; b=lt4XdFNCPXD0aRAFi5YHPQ1S1it/aI9tfA9xfm+yNnqAIzD/jttF3S+2gCul4hnte vg0VO3BdV9GQSCQ0YgT2FAcEoHh2i0BksKdoVKOv85EKMBkrp3N1CPNg+qbolAuTfE /BywJOTVooMe5BJ25cyH5IG/ClFAMAvafMXfbCro= 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 4.9 01/22] netfilter: nfnetlink: avoid deadlock due to synchronous request_module Date: Fri, 2 Aug 2019 09:25:25 -0400 Message-Id: <20190802132547.14517-1-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 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 2278d9ab723bf..9837a61cb3e3b 100644 --- a/net/netfilter/nfnetlink.c +++ b/net/netfilter/nfnetlink.c @@ -490,7 +490,7 @@ 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