[PATCH 4.9 159/207] net: mdio-mux: fix unbalanced put_device

Greg Kroah-Hartman
2021-11-24T12:23:14Z

From: Corentin Labbe <clabbe.montjoie@gmail.com>

commit 60f786525032432af1b7d9b8935cb12936244ccd upstream.

mdio_mux_uninit() call put_device (unconditionally) because of
of_mdio_find_bus() in mdio_mux_init.
But of_mdio_find_bus is only called if mux_bus is empty.
If mux_bus is set, mdio_mux_uninit will print a "refcount_t: underflow"
trace.

This patch add a get_device in the other branch of "if (mux_bus)".

Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/phy/mdio-mux.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

--- a/drivers/net/phy/mdio-mux.c
+++ b/drivers/net/phy/mdio-mux.c
@@ -117,6 +117,7 @@ int mdio_mux_init(struct device *dev,
} else {
parent_bus_node = NULL;
parent_bus = mux_bus;
+ get_device(&parent_bus->dev);
}

pb = devm_kzalloc(dev, sizeof(*pb), GFP_KERNEL);
@@ -182,9 +183,7 @@ int mdio_mux_init(struct device *dev,

devm_kfree(dev, pb);
err_pb_kz:
- /* balance the reference of_mdio_find_bus() took */
- if (!mux_bus)
- put_device(&parent_bus->dev);
+ put_device(&parent_bus->dev);
err_parent_bus:
of_node_put(parent_bus_node);
return ret_val;
@@ -202,7 +201,6 @@ void mdio_mux_uninit(void *mux_handle)
cb = cb->next;
}

- /* balance the reference of_mdio_find_bus() in mdio_mux_init() took */
put_device(&pb->mii_bus->dev);
}
EXPORT_SYMBOL_GPL(mdio_mux_uninit);