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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 681CDC28B2B for ; Fri, 19 Aug 2022 16:19:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1352137AbiHSQTm (ORCPT ); Fri, 19 Aug 2022 12:19:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36996 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1352132AbiHSQPp (ORCPT ); Fri, 19 Aug 2022 12:15:45 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0A198D39A8; Fri, 19 Aug 2022 08:58:45 -0700 (PDT) Received: from dggemv704-chm.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4M8RD641SmzkWQg; Fri, 19 Aug 2022 23:55:18 +0800 (CST) Received: from kwepemm600001.china.huawei.com (7.193.23.3) by dggemv704-chm.china.huawei.com (10.3.19.47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 19 Aug 2022 23:58:33 +0800 Received: from [10.174.176.245] (10.174.176.245) by kwepemm600001.china.huawei.com (7.193.23.3) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 19 Aug 2022 23:58:32 +0800 Message-ID: Date: Fri, 19 Aug 2022 23:58:32 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [PATCH net] net/sched: fix netdevice reference leaks in attach_one_default_qdisc() To: Jakub Kicinski CC: , , , , , , , , References: <20220817104646.22861-1-wanghai38@huawei.com> <20220818105642.6d58e9d4@kernel.org> From: "wanghai (M)" In-Reply-To: <20220818105642.6d58e9d4@kernel.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.176.245] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To kwepemm600001.china.huawei.com (7.193.23.3) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2022/8/19 1:56, Jakub Kicinski 写道: > On Wed, 17 Aug 2022 18:46:46 +0800 Wang Hai wrote: >> In attach_default_qdiscs(), when attach default qdisc (fq_codel) fails >> and fallback to noqueue, if the original attached qdisc is not released >> and a new one is directly attached, this will cause netdevice reference >> leaks. > Could you provide more details on the failure path? My preference would > be to try to clean up properly there, if possible. Hi Jakub. Here are the details of the failure. Do I need to do cleanup under the failed path? If a dev has multiple queues and queue 0 fails to attach qdisc because there is no memory in attach_one_default_qdisc(). Then dev->qdisc will be noop_qdisc by default. But the other queues may be able to successfully attach to default qdisc. In this case, the fallback to noqueue process will be triggered static void attach_default_qdiscs(struct net_device *dev) {     ...     if (!netif_is_multiqueue(dev) ||         dev->priv_flags & IFF_NO_QUEUE) {             ...             netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL); // queue 0 attach failed because -ENOBUFS, but the other queues attach successfully             qdisc = txq->qdisc_sleeping;             rcu_assign_pointer(dev->qdisc, qdisc); // dev->qdisc = &noop_qdisc             ...     }     ...     if (qdisc == &noop_qdisc) {         ...         netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL); // Re-attach, but not release the previously created qdisc         ...     } } >> The following is the bug log: >> >> veth0: default qdisc (fq_codel) fail, fallback to noqueue >> unregister_netdevice: waiting for veth0 to become free. Usage count = 32 >> leaked reference. >> qdisc_alloc+0x12e/0x210 >> qdisc_create_dflt+0x62/0x140 >> attach_one_default_qdisc.constprop.41+0x44/0x70 >> dev_activate+0x128/0x290 >> __dev_open+0x12a/0x190 >> __dev_change_flags+0x1a2/0x1f0 >> dev_change_flags+0x23/0x60 >> do_setlink+0x332/0x1150 >> __rtnl_newlink+0x52f/0x8e0 >> rtnl_newlink+0x43/0x70 >> rtnetlink_rcv_msg+0x140/0x3b0 >> netlink_rcv_skb+0x50/0x100 >> netlink_unicast+0x1bb/0x290 >> netlink_sendmsg+0x37c/0x4e0 >> sock_sendmsg+0x5f/0x70 >> ____sys_sendmsg+0x208/0x280 >> >> In attach_one_default_qdisc(), release the old one before attaching >> a new qdisc to fix this bug. >> >> Fixes: bf6dba76d278 ("net: sched: fallback to qdisc noqueue if default qdisc setup fail") >> Signed-off-by: Wang Hai >> --- >> net/sched/sch_generic.c | 5 +++++ >> 1 file changed, 5 insertions(+) >> >> diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c >> index d47b9689eba6..87b61ef14497 100644 >> --- a/net/sched/sch_generic.c >> +++ b/net/sched/sch_generic.c >> @@ -1140,6 +1140,11 @@ static void attach_one_default_qdisc(struct net_device *dev, >> >> if (!netif_is_multiqueue(dev)) >> qdisc->flags |= TCQ_F_ONETXQUEUE | TCQ_F_NOPARENT; >> + >> + if (dev_queue->qdisc_sleeping && >> + dev_queue->qdisc_sleeping != &noop_qdisc) >> + qdisc_put(dev_queue->qdisc_sleeping); >> + >> dev_queue->qdisc_sleeping = qdisc; >> } >> > . -- Wang Hai