[PATCH 9/9] net: fix net_device refcounting

From: Russell King
Date: Tue Sep 22 2015 - 12:19:38 EST


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@xxxxxxxxxxxxxxxx>
---
net/core/net-sysfs.c | 9 +++++++++
net/dsa/dsa.c | 5 ++++-
2 files changed, 13 insertions(+), 1 deletion(-)

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;
diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
index bf4ba15fb780..c59fa5d9c22c 100644
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@@ -679,7 +679,7 @@ static int dsa_of_probe(struct device *dev)
pd = kzalloc(sizeof(*pd), GFP_KERNEL);
if (!pd) {
ret = -ENOMEM;
- goto out_put_mdio;
+ goto out_put_ethernet;
}

dev->platform_data = pd;
@@ -773,6 +773,8 @@ static int dsa_of_probe(struct device *dev)
out_free:
kfree(pd);
dev->platform_data = NULL;
+out_put_ethernet:
+ put_device(&ethernet_dev->dev);
out_put_mdio:
put_device(&mdio_bus->dev);
return ret;
@@ -786,6 +788,7 @@ static void dsa_of_remove(struct device *dev)
return;

dsa_of_free_platform_data(pd);
+ put_device(&pd->of_netdev->dev);
kfree(pd);
}
#else
--
2.1.0

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