Messages in this thread | | | Date | Thu, 25 Aug 2022 20:29:21 +0800 | Subject | Re: [PATCH net] net/sched: fix netdevice reference leaks in attach_one_default_qdisc() | From | "wanghai (M)" <> |
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在 2022/8/19 23:58, wanghai (M) 写道: > > 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 > ... > } > } > Hi Jakub. Do you have any other suggestions for this patch? Any replies would be appreciated.
>>> 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 <wanghai38@huawei.com> >>> --- >>> 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
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