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Subject[PATCH] mdio: mux: Correct mdio_mux_init error path issues
There is a potential unnecessary refcount decriment on error path of
put_device(&pb->mii_bus->dev), as it is possible to avoid the
of_mdio_find_bus() call if mux_bus is specified by the calling function.

The same put_device() is not called in the error path if the
devm_kzalloc of pb fails. This caused the variable used in the
put_device() to be changed, as the pb pointer was obviously not set up.

There is an unnecessary of_node_get() on child_bus_node if the
of_mdiobus_register() is successful, as the
for_each_available_child_of_node() automatically increments this.
Thus the refcount on this node will always be +1 more than it should be.

There is no of_node_put() on child_bus_node if the of_mdiobus_register()
call fails.

Finally, it is lacking devm_kfree() of pb in the error path. While this
might not be technically necessary, it was present in other parts of the
function. So, I am adding it where necessary to make it uniform.

Signed-off-by: Jon Mason <>
Fixes: f20e6657a875 ("mdio: mux: Enhanced MDIO mux framework for integrated multiplexers")
Fixes: 0ca2997d1452 ("netdev/of/phy: Add MDIO bus multiplexer support.")
drivers/net/phy/mdio-mux.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/net/phy/mdio-mux.c b/drivers/net/phy/mdio-mux.c
index 963838d4fac1..6943c5ece44a 100644
--- a/drivers/net/phy/mdio-mux.c
+++ b/drivers/net/phy/mdio-mux.c
@@ -122,10 +122,9 @@ int mdio_mux_init(struct device *dev,
pb = devm_kzalloc(dev, sizeof(*pb), GFP_KERNEL);
if (pb == NULL) {
ret_val = -ENOMEM;
- goto err_parent_bus;
+ goto err_pb_kz;

pb->switch_data = data;
pb->switch_fn = switch_fn;
pb->current_child = -1;
@@ -154,6 +153,7 @@ int mdio_mux_init(struct device *dev,
cb->mii_bus = mdiobus_alloc();
if (!cb->mii_bus) {
ret_val = -ENOMEM;
+ devm_kfree(dev, cb);
@@ -169,8 +169,8 @@ int mdio_mux_init(struct device *dev,
if (r) {
devm_kfree(dev, cb);
+ of_node_put(child_bus_node);
} else {
- of_node_get(child_bus_node);
cb->next = pb->children;
pb->children = cb;
@@ -181,9 +181,11 @@ int mdio_mux_init(struct device *dev,
return 0;

+ devm_kfree(dev, pb);
/* balance the reference of_mdio_find_bus() took */
- put_device(&pb->mii_bus->dev);
+ if (!mux_bus)
+ put_device(&parent_bus->dev);
return ret_val;
 \ /
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