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,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 8333DC2D0C6 for ; Fri, 27 Dec 2019 18:07:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5D2BC20722 for ; Fri, 27 Dec 2019 18:07:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1577470056; bh=5xoNdYn26opBSDh04DZK7AGpg1tz1m+vcD613elU4+s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=EO18uYEg8b3LmBVL63wRVpDRRyzkfcrTXiV3cC0EknOirBwSWbyyKKTL5U8U3o6d6 YVD37YiJ13pXWnHl9VQEU8xhQqTuUizRX+nHZK7C5NEzlZN6l7qeI6ixhC/+nCpQYv lhU6yIk6pmNXUlL+rUOynKVPZPvErfjsp9nNt4s4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728137AbfL0SHb (ORCPT ); Fri, 27 Dec 2019 13:07:31 -0500 Received: from mail.kernel.org ([198.145.29.99]:59272 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727250AbfL0SC1 (ORCPT ); Fri, 27 Dec 2019 13:02:27 -0500 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 32F3F2173E; Fri, 27 Dec 2019 18:02:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1577469747; bh=5xoNdYn26opBSDh04DZK7AGpg1tz1m+vcD613elU4+s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xYvuDoxMeZzt0S9+t6nyu/yOsoUqdrnzmRtR6JfdNYHqWC9GMFdrU6yxMnGMvEx3j MqDAn2V+jPlgy+xaiNlRvBN868l0VpGLoOtJFkustmPP1KImk93tZIpLm7Z8oDhoiZ vB5plIzMSQhjxHHtssW/Ajsmjl8VPb+TcwDufdTs= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Florian Westphal , Pablo Neira Ayuso , Sasha Levin , netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org Subject: [PATCH AUTOSEL 4.14 03/57] netfilter: ctnetlink: netns exit must wait for callbacks Date: Fri, 27 Dec 2019 13:01:28 -0500 Message-Id: <20191227180222.7076-3-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191227180222.7076-1-sashal@kernel.org> References: <20191227180222.7076-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@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 c781c9a1a697..39a32edaa92c 100644 --- a/net/netfilter/nf_conntrack_netlink.c +++ b/net/netfilter/nf_conntrack_netlink.c @@ -3422,6 +3422,9 @@ 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