Commit 543e3a8d authored Mar 24, 2016 by Bjorn Helgaas Committed by David S. Miller Mar 25, 2016

netpoll: Fix extra refcount release in netpoll_cleanup()

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
device.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 7dd39913

net/core/netpoll.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -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;
		}
		dev_hold(ndev);
		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;

		put:
		np->dev = NULL;
		dev_put(ndev);
		unlock:
		rtnl_unlock();

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