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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 B25DBC43381 for ; Wed, 20 Feb 2019 16:00:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8F56D2086A for ; Wed, 20 Feb 2019 16:00:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725915AbfBTQAL (ORCPT ); Wed, 20 Feb 2019 11:00:11 -0500 Received: from mx1.redhat.com ([209.132.183.28]:57096 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725801AbfBTQAK (ORCPT ); Wed, 20 Feb 2019 11:00:10 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 53DE4C8F8C; Wed, 20 Feb 2019 16:00:10 +0000 (UTC) Received: from localhost.localdomain (unknown [10.32.181.131]) by smtp.corp.redhat.com (Postfix) with ESMTP id 70E005D970; Wed, 20 Feb 2019 16:00:09 +0000 (UTC) Message-ID: <41e9458103145407898f2c61c99589564009658f.camel@redhat.com> Subject: Re: [PATCH net] ipv6: route: purge exception on removal From: Paolo Abeni To: netdev@vger.kernel.org Cc: David Ahern , "David S. Miller" Date: Wed, 20 Feb 2019 17:00:08 +0100 In-Reply-To: <460ef555bb02ec46d8a6108aa0d7b0095e11afd1.1550662037.git.pabeni@redhat.com> References: <460ef555bb02ec46d8a6108aa0d7b0095e11afd1.1550662037.git.pabeni@redhat.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.30.5 (3.30.5-1.fc29) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Wed, 20 Feb 2019 16:00:10 +0000 (UTC) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, 2019-02-20 at 15:08 +0100, Paolo Abeni wrote: > When a netdevice is unregistered, we flush the relevant exception > via rt6_sync_down_dev() -> fib6_ifdown() -> fib6_del() -> fib6_del_route(). > > Finally, we end-up calling rt6_remove_exception(), where we release > the relevant dst, while we keep the references to the related fib6_info and > dev. Such references should be released later when the dst will be > destroyed. > > There are a number of caches that can keep the exception around for an > unlimited amount of time - namely dst_cache, possibly even socket cache. > As a result device registration may hang, as demonstrated by this script: > > ip netns add cl > ip netns add rt > ip netns add srv > ip netns exec rt sysctl -w net.ipv6.conf.all.forwarding=1 > > ip link add name cl_veth type veth peer name cl_rt_veth > ip link set dev cl_veth netns cl > ip -n cl link set dev cl_veth up > ip -n cl addr add dev cl_veth 2001::2/64 > ip -n cl route add default via 2001::1 > > ip -n cl link add tunv6 type ip6tnl mode ip6ip6 local 2001::2 remote 2002::1 hoplimit 64 dev cl_veth > ip -n cl link set tunv6 up > ip -n cl addr add 2013::2/64 dev tunv6 > > ip link set dev cl_rt_veth netns rt > ip -n rt link set dev cl_rt_veth up > ip -n rt addr add dev cl_rt_veth 2001::1/64 > > ip link add name rt_srv_veth type veth peer name srv_veth > ip link set dev srv_veth netns srv > ip -n srv link set dev srv_veth up > ip -n srv addr add dev srv_veth 2002::1/64 > ip -n srv route add default via 2002::2 > > ip -n srv link add tunv6 type ip6tnl mode ip6ip6 local 2002::1 remote 2001::2 hoplimit 64 dev srv_veth > ip -n srv link set tunv6 up > ip -n srv addr add 2013::1/64 dev tunv6 > > ip link set dev rt_srv_veth netns rt > ip -n rt link set dev rt_srv_veth up > ip -n rt addr add dev rt_srv_veth 2002::2/64 > > ip netns exec srv netserver & sleep 0.1 > ip netns exec cl ping6 -c 4 2013::1 > ip netns exec cl netperf -H 2013::1 -t TCP_STREAM -l 3 & sleep 1 > ip -n rt link set dev rt_srv_veth mtu 1400 > wait %2 > > ip -n cl link del cl_veth > > This commit addresses the issue purging all the references held by the > exception at time, as we currently do for e.g. ipv6 pcpu dst entries. > > Fixes: 93531c674315 ("net/ipv6: separate handling of FIB entries from dst based routes") > Signed-off-by: Paolo Abeni > --- > net/ipv6/route.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/net/ipv6/route.c b/net/ipv6/route.c > index 964491cf3672..43a819ae46c2 100644 > --- a/net/ipv6/route.c > +++ b/net/ipv6/route.c > @@ -1274,11 +1274,21 @@ static DEFINE_SPINLOCK(rt6_exception_lock); > static void rt6_remove_exception(struct rt6_exception_bucket *bucket, > struct rt6_exception *rt6_ex) > { > + struct fib6_info *from; > struct net *net; > > if (!bucket || !rt6_ex) > return; > > + /* purge completely the exception to allow releasing the held resources: > + * some [sk] cache may keep the dst around for unlimited time > + */ > + from = rcu_dereference_protected(rt6_ex->rt6i->from, > + lockdep_is_held(&rt6_exception_lock)); > + rcu_assign_pointer(rt6_ex->rt6i->from, NULL); > + fib6_info_release(from); > + dst_dev_put(&rt6_ex->rt6i->dst); > + > net = dev_net(rt6_ex->rt6i->dst.dev); uhm... This is possibly racy, if dev goes away on dst_dev_put(). I'll send a v2 reordering the operation so that we don't access dev (and net ) after dst_dev_put(). Sorry for the noise, Paolo