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,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 9E9C3C33C9E for ; Sat, 11 Jan 2020 10:15:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 731B9208E4 for ; Sat, 11 Jan 2020 10:15:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578737701; bh=tcLG8+JVF+ooC+z8TNYOf9QGLZPT+V/PPErH5ds8vCo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=YLXcbmPZKX/z3lzrvsGANR0PpJD2NM0K72QZdgK+N/oxWklrtm7vnJEA3MF1ktxWk 8eMkVQmqDTS3tL2q0h1827TqfY3Yf0AxqgtmgrZffPVWUReYSMd4j2cwk6SGpREhIB 4p3GF9Tsj++b7bJ8cgmZkz4Sbj5DpN1T9Gl7e+/o= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730204AbgAKKPA (ORCPT ); Sat, 11 Jan 2020 05:15:00 -0500 Received: from mail.kernel.org ([198.145.29.99]:55660 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729973AbgAKKO5 (ORCPT ); Sat, 11 Jan 2020 05:14:57 -0500 Received: from localhost (unknown [62.119.166.9]) (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 0BB4E2082E; Sat, 11 Jan 2020 10:14:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578737696; bh=tcLG8+JVF+ooC+z8TNYOf9QGLZPT+V/PPErH5ds8vCo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dzG+P6ezqjcf1EWKxaYFlytRgFZ7dYcpynm77lCoODc6SDNpFjUFBx2N5li+Z9Wf8 JHMyPASYAIwjWjp7aFF7Yrw9KaiytHPHEHrk4bc7rJrmXlj1HEEoQOPQutKqe/KUzc 4IhDAidfjYbuywJstYDq4aHVrmIQCtVksXCbgJNg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Florian Westphal , Pablo Neira Ayuso , Sasha Levin Subject: [PATCH 4.19 07/84] netfilter: ctnetlink: netns exit must wait for callbacks Date: Sat, 11 Jan 2020 10:49:44 +0100 Message-Id: <20200111094846.716942155@linuxfoundation.org> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200111094845.328046411@linuxfoundation.org> References: <20200111094845.328046411@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 From: Florian Westphal [ Upstream commit 18a110b022a5c02e7dc9f6109d0bd93e58ac6ebb ] Curtis Taylor and Jon Maxwell reported and debugged a crash on 3.10 based kernel. Crash occurs in ctnetlink_conntrack_events because net->nfnl socket is NULL. The nfnl socket was set to NULL by netns destruction running on another cpu. The exiting network namespace calls the relevant destructors in the following order: 1. ctnetlink_net_exit_batch This nulls out the event callback pointer in struct netns. 2. nfnetlink_net_exit_batch This nulls net->nfnl socket and frees it. 3. nf_conntrack_cleanup_net_list This removes all remaining conntrack entries. This is order is correct. The only explanation for the crash so ar is: cpu1: conntrack is dying, eviction occurs: -> nf_ct_delete() -> nf_conntrack_event_report \ -> nf_conntrack_eventmask_report -> notify->fcn() (== ctnetlink_conntrack_events). cpu1: a. fetches rcu protected pointer to obtain ctnetlink event callback. b. gets interrupted. cpu2: runs netns exit handlers: a runs ctnetlink destructor, event cb pointer set to NULL. b runs nfnetlink destructor, nfnl socket is closed and set to NULL. cpu1: c. resumes and trips over NULL net->nfnl. Problem appears to be that ctnetlink_net_exit_batch only prevents future callers of nf_conntrack_eventmask_report() from obtaining the callback. It doesn't wait of other cpus that might have already obtained the callbacks address. I don't see anything in upstream kernels that would prevent similar crash: We need to wait for all cpus to have exited the event callback. Fixes: 9592a5c01e79dbc59eb56fa ("netfilter: ctnetlink: netns support") Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso Signed-off-by: Sasha Levin --- net/netfilter/nf_conntrack_netlink.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c index 47e5a076522d..7ba9ea55816a 100644 --- a/net/netfilter/nf_conntrack_netlink.c +++ b/net/netfilter/nf_conntrack_netlink.c @@ -3576,6 +3576,9 @@ static void __net_exit ctnetlink_net_exit_batch(struct list_head *net_exit_list) list_for_each_entry(net, net_exit_list, exit_list) ctnetlink_net_exit(net); + + /* wait for other cpus until they are done with ctnl_notifiers */ + synchronize_rcu(); } static struct pernet_operations ctnetlink_net_ops = { -- 2.20.1