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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 08CC7C3A5A1 for ; Thu, 22 Aug 2019 17:48:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CA41C233FC for ; Thu, 22 Aug 2019 17:48:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566496088; bh=SjlbYIDq9G0CebwODxm4/BZhdOniFDbdZN/Rfjxiv8M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=R7J9iuhOSu/YQj30JaxMSwP+MPjcFaOKQRGHYBWu+L7nllDP0RbeSfp0Uoa5XnfvJ UKQTjFYcTa2geMr7bgDG6OWj/eo3PSYjXZepwy0s6pu701fSHyqWnra2klWLSqfAnR SRdrA1x0fH6/xozp27aWIEoOQm8bISGUNCl2tqrU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393426AbfHVRsH (ORCPT ); Thu, 22 Aug 2019 13:48:07 -0400 Received: from mail.kernel.org ([198.145.29.99]:40818 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391356AbfHVRWd (ORCPT ); Thu, 22 Aug 2019 13:22:33 -0400 Received: from localhost (wsip-184-188-36-2.sd.sd.cox.net [184.188.36.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4479D21743; Thu, 22 Aug 2019 17:22:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566494553; bh=SjlbYIDq9G0CebwODxm4/BZhdOniFDbdZN/Rfjxiv8M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DTYtSXrDNOPrjp+4mrzJRvm5mEzxa83kEmqkHhXLutDSfe/B0/WcSrGMbqyj+FRDR PeutdcLra9eyPPUOlJYaoIwO0GqVGzx7Gc0XgEj/taCcKKlis6vUoVpSwDNegZtDTW r+Jm6CBApZYar5ma9n7KxCrDlxnSZW0FqHDBbVyI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Thomas Jarosch , Juliana Rodrigueiro , Florian Westphal , Pablo Neira Ayuso , Sasha Levin Subject: [PATCH 4.4 09/78] netfilter: nfnetlink: avoid deadlock due to synchronous request_module Date: Thu, 22 Aug 2019 10:18:13 -0700 Message-Id: <20190822171832.313288206@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190822171832.012773482@linuxfoundation.org> References: <20190822171832.012773482@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [ 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 9adedba78eeac..044559c10e98e 100644 --- a/net/netfilter/nfnetlink.c +++ b/net/netfilter/nfnetlink.c @@ -495,7 +495,7 @@ 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