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Subject[PATCH 3.16 255/346] ipv6: addrconf: fix dev refcont leak when DAD failed
3.16.39-rc1 review patch.  If anyone has any objections, please let me know.


From: Wei Yongjun <>

commit 751eb6b6042a596b0080967c1a529a9fe98dac1d upstream.

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:

-> 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

Fixes: c15b1ccadb32 ("ipv6: move DAD and addrconf_verify processing
to workqueue")
Signed-off-by: Wei Yongjun <>
Signed-off-by: David S. Miller <>
Signed-off-by: Ben Hutchings <>
net/ipv6/addrconf.c | 2 ++
1 file changed, 2 insertions(+)

--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1686,6 +1686,7 @@ void addrconf_dad_failure(struct inet6_i

addrconf_mod_dad_work(ifp, 0);
+ in6_ifa_put(ifp);

/* Join to solicited addr multicast group.
@@ -3262,6 +3263,7 @@ static void addrconf_dad_work(struct wor
goto out;
} else if (action == DAD_ABORT) {
+ in6_ifa_hold(ifp);
addrconf_dad_stop(ifp, 1);
goto out;
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