net: fix net_device refcounting

of_find_net_device_by_node() uses class_find_device() internally to
lookup the corresponding network device.  class_find_device() returns
a reference to the embedded struct device, with its refcount
incremented.

Add a comment to the definition in net/core/net-sysfs.c indicating the
need to drop this refcount, and fix the DSA code to drop this refcount
when the OF-generated platform data is cleaned up and freed.  Also
arrange for the ref to be dropped when handling errors.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 0 deletions

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index b279077c3089..805a95a48107 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1481,6 +1481,15 @@ static int of_dev_node_match(struct device *dev, const void *data)
 	return ret == 0 ? dev->of_node == data : ret;
 }
 
+/*
+ * of_find_net_device_by_node - lookup the net device for the device node
+ * @np: OF device node
+ *
+ * Looks up the net_device structure corresponding with the device node.
+ * If successful, returns a pointer to the net_device with the embedded
+ * struct device refcount incremented by one, or NULL on failure. The
+ * refcount must be dropped when done with the net_device.
+ */
 struct net_device *of_find_net_device_by_node(struct device_node *np)
 {
 	struct device *dev;