[Patch] rtnetlink: call ->dellink on failure when ->newlink exists

Ignacy reported that when eth0 is down and add a vlan device
on top of it like:

  ip link add link eth0 name eth0.1 up type vlan id 1

We will get a refcount leak:

  unregister_netdevice: waiting for eth0.1 to become free. Usage count = 2

The problem is when rtnl_configure_link() fails in rtnl_newlink(),
we simply call unregister_device(), but for stacked device like vlan,
we almost do nothing when we unregister the upper device, more work
is done when we unregister the lower device, so call its ->dellink().

Reported-by: Ignacy Gawedzki <redacted>
Signed-off-by: Cong Wang <redacted>
---
 net/core/rtnetlink.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 5be499b..ab293a3 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c

@@ -2162,7 +2162,14 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh)
 		}
 		err = rtnl_configure_link(dev, ifm);
 		if (err < 0) {
-			unregister_netdevice(dev);
+			if (ops->newlink) {
+				LIST_HEAD(list_kill);
+
+				ops->dellink(dev, &list_kill);
+				unregister_netdevice_many(&list_kill);
+			} else {
+				unregister_netdevice(dev);
+			}
 			goto out;
 		}
 

-- 
1.8.3.1