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>
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index bdf368e..2f1f5d4 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1948,6 +1948,7 @@ errdad:
spin_unlock_bh(&ifp->lock);
addrconf_mod_dad_work(ifp, 0);
+ in6_ifa_put(ifp);
}
/* Join to solicited addr multicast group.
@@ -3857,6 +3858,7 @@ static void addrconf_dad_work(struct work_struct *w)
addrconf_dad_begin(ifp);
goto out;
} else if (action == DAD_ABORT) {
+ in6_ifa_hold(ifp);
addrconf_dad_stop(ifp, 1);
if (disable_ipv6)
addrconf_ifdown(idev->dev, 0);
--
2.7.0
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