Messages in this thread Patch in this message | | | Date | Fri, 19 Aug 2022 23:58:32 +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 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 <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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