[PATCH v2] netpoll: Fix extra refcount release in netpoll_cleanup()

From: Bjorn Helgaas
Date: Thu Mar 24 2016 - 22:56:33 EST

netpoll_setup() does a dev_hold() on np->dev, the netpoll device. If it
fails, it correctly does a dev_put() but leaves np->dev set. If we call
netpoll_cleanup() after the failure, np->dev is still set so we do another
dev_put(), which decrements the refcount an extra time.

It's questionable to call netpoll_cleanup() after netpoll_setup() fails,
but it can be difficult to find the problem, and we can easily avoid it in
this case. The extra decrements can lead to hangs like this:

unregister_netdevice: waiting for bond0 to become free. Usage count = -3

Set and clear np->dev at the points where we dev_hold() and dev_put() the

Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
net/core/netpoll.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 94acfc8..a57bd17 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -603,7 +603,6 @@ int __netpoll_setup(struct netpoll *np, struct net_device *ndev)
const struct net_device_ops *ops;
int err;

- np->dev = ndev;
strlcpy(np->dev_name, ndev->name, IFNAMSIZ);
INIT_WORK(&np->cleanup_work, netpoll_async_cleanup);

@@ -670,6 +669,7 @@ int netpoll_setup(struct netpoll *np)
goto unlock;
+ np->dev = ndev;

if (netdev_master_upper_dev_get(ndev)) {
np_err(np, "%s is a slave device, aborting\n", np->dev_name);
@@ -770,6 +770,7 @@ int netpoll_setup(struct netpoll *np)
return 0;

+ np->dev = NULL;