From: Wei Yongjun <weiyongjun1@xxxxxxxxxx>
Date: Mon, 5 Sep 2016 16:06:31 +0800
> In general, when DAD detected IPv6 duplicate address, ifp->state
> will be set to INET6_IFADDR_STATE_ERRDAD and DAD is stopped by a
> delayed work, the call tree should be like this:
>
> ndisc_recv_ns
> -> addrconf_dad_failure <- missing ifp put
> -> addrconf_mod_dad_work
> -> schedule addrconf_dad_work()
> -> addrconf_dad_stop() <- missing ifp hold before call it
>
> addrconf_dad_failure() called with ifp refcont holding but not put.
> addrconf_dad_work() call addrconf_dad_stop() without extra holding
> refcount. This will not cause any issue normally.
>
> But the race between addrconf_dad_failure() and addrconf_dad_work()
> may cause ifp refcount leak and netdevice can not be unregister,
> dmesg show the following messages:
>
> IPv6: eth0: IPv6 duplicate address fe80::XX:XXXX:XXXX:XX detected!
> ...
> unregister_netdevice: waiting for eth0 to become free. Usage count = 1
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: c15b1ccadb32 ("ipv6: move DAD and addrconf_verify processing
> to workqueue")
> Signed-off-by: Wei Yongjun <weiyongjun1@xxxxxxxxxx>
Applied and queued up for -stable.
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