[PATCH 3.10 222/319] ipv6: addrconf: fix dev refcont leak when DAD failed

Willy Tarreau
2017-02-05T19:45:10Z

From: Wei Yongjun <weiyongjun1@huawei.com>

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:

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@vger.kernel.org
Fixes: c15b1ccadb32 ("ipv6: move DAD and addrconf_verify processing
to workqueue")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: Mike Manning <mmanning@brocade.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
net/ipv6/addrconf.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 98dd353..0f18d858 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1694,6 +1694,7 @@ void addrconf_dad_failure(struct inet6_ifaddr *ifp)
spin_unlock_bh(&ifp->state_lock);

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

/* Join to solicited addr multicast group. */
@@ -3337,6 +3338,7 @@ 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);
goto out;
}
--
2.8.0.rc2.1.gbe9624a