ipv6: only call ip6_route_dev_notify() once for NETDEV_UNREGISTER

commit 76da0704507bbc51875013f6557877ab308cfd0a upstream.

In commit 242d3a49a2a1 ("ipv6: reorder ip6_route_dev_notifier after ipv6_dev_notf")
I assumed NETDEV_REGISTER and NETDEV_UNREGISTER are paired,
unfortunately, as reported by jeffy, netdev_wait_allrefs()
could rebroadcast NETDEV_UNREGISTER event until all refs are
gone.

We have to add an additional check to avoid this corner case.
For netdev_wait_allrefs() dev->reg_state is NETREG_UNREGISTERED,
for dev_change_net_namespace(), dev->reg_state is
NETREG_REGISTERED. So check for dev->reg_state != NETREG_UNREGISTERED.

Fixes: 242d3a49a2a1 ("ipv6: reorder ip6_route_dev_notifier after ipv6_dev_notf")
Reported-by: jeffy <jeffy.chen@rock-chips.com>
Cc: David Ahern <dsahern@gmail.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 286beb459faa1e197d19e12c2f48323eb1ce592b..af2bc34cb81fe592a63882f2765a483d12263c30 100644 (file)
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2835,7 +2835,11 @@ static int ip6_route_dev_notify(struct notifier_block *this,
                net->ipv6.ip6_blk_hole_entry->dst.dev = dev;
                net->ipv6.ip6_blk_hole_entry->rt6i_idev = in6_dev_get(dev);
 #endif
-        } else if (event == NETDEV_UNREGISTER) {
+        } else if (event == NETDEV_UNREGISTER &&
+                   dev->reg_state != NETREG_UNREGISTERED) {
+               /* NETDEV_UNREGISTER could be fired for multiple times by
+                * netdev_wait_allrefs(). Make sure we only call this once.
+                */
                in6_dev_put(net->ipv6.ip6_null_entry->rt6i_idev);
 #ifdef CONFIG_IPV6_MULTIPLE_TABLES
                in6_dev_put(net->ipv6.ip6_prohibit_entry->rt6i_idev);