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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 BEEF7C71122 for ; Sun, 14 Oct 2018 15:47:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8DD8920645 for ; Sun, 14 Oct 2018 15:47:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8DD8920645 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=decadent.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729684AbeJNX2i (ORCPT ); Sun, 14 Oct 2018 19:28:38 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:37269 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728125AbeJNX2i (ORCPT ); Sun, 14 Oct 2018 19:28:38 -0400 Received: from [2a02:8011:400e:2:cbab:f00:c93f:614] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.84_2) (envelope-from ) id 1gBiM3-0004cH-4e; Sun, 14 Oct 2018 16:30:55 +0100 Received: from ben by deadeye with local (Exim 4.91) (envelope-from ) id 1gBiLS-0000Kx-GO; Sun, 14 Oct 2018 16:30:18 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Wolfgang Bumiller" , "David S. Miller" Date: Sun, 14 Oct 2018 16:25:41 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 144/366] net: fix deadlock while clearing neighbor proxy table In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:cbab:f00:c93f:614 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.60-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Wolfgang Bumiller commit 53b76cdf7e8fecec1d09e38aad2f8579882591a8 upstream. When coming from ndisc_netdev_event() in net/ipv6/ndisc.c, neigh_ifdown() is called with &nd_tbl, locking this while clearing the proxy neighbor entries when eg. deleting an interface. Calling the table's pndisc_destructor() with the lock still held, however, can cause a deadlock: When a multicast listener is available an IGMP packet of type ICMPV6_MGM_REDUCTION may be sent out. When reaching ip6_finish_output2(), if no neighbor entry for the target address is found, __neigh_create() is called with &nd_tbl, which it'll want to lock. Move the elements into their own list, then unlock the table and perform the destruction. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199289 Fixes: 6fd6ce2056de ("ipv6: Do not depend on rt->n in ip6_finish_output2().") Signed-off-by: Wolfgang Bumiller Signed-off-by: David S. Miller [bwh: Backported to 3.16: - Move the (useless) call to release_net() as well - Adjust context] Signed-off-by: Ben Hutchings --- --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -54,7 +54,8 @@ do { \ static void neigh_timer_handler(unsigned long arg); static void __neigh_notify(struct neighbour *n, int type, int flags); static void neigh_update_notify(struct neighbour *neigh); -static int pneigh_ifdown(struct neigh_table *tbl, struct net_device *dev); +static int pneigh_ifdown_and_unlock(struct neigh_table *tbl, + struct net_device *dev); static struct neigh_table *neigh_tables; #ifdef CONFIG_PROC_FS @@ -260,8 +261,7 @@ int neigh_ifdown(struct neigh_table *tbl { write_lock_bh(&tbl->lock); neigh_flush_dev(tbl, dev); - pneigh_ifdown(tbl, dev); - write_unlock_bh(&tbl->lock); + pneigh_ifdown_and_unlock(tbl, dev); del_timer_sync(&tbl->proxy_timer); pneigh_queue_purge(&tbl->proxy_queue); @@ -659,9 +659,10 @@ int pneigh_delete(struct neigh_table *tb return -ENOENT; } -static int pneigh_ifdown(struct neigh_table *tbl, struct net_device *dev) +static int pneigh_ifdown_and_unlock(struct neigh_table *tbl, + struct net_device *dev) { - struct pneigh_entry *n, **np; + struct pneigh_entry *n, **np, *freelist = NULL; u32 h; for (h = 0; h <= PNEIGH_HASHMASK; h++) { @@ -669,17 +670,24 @@ static int pneigh_ifdown(struct neigh_ta while ((n = *np) != NULL) { if (!dev || n->dev == dev) { *np = n->next; - if (tbl->pdestructor) - tbl->pdestructor(n); - if (n->dev) - dev_put(n->dev); - release_net(pneigh_net(n)); - kfree(n); + n->next = freelist; + freelist = n; continue; } np = &n->next; } } + write_unlock_bh(&tbl->lock); + while ((n = freelist)) { + freelist = n->next; + n->next = NULL; + if (tbl->pdestructor) + tbl->pdestructor(n); + if (n->dev) + dev_put(n->dev); + release_net(pneigh_net(n)); + kfree(n); + } return -ENOENT; }