linux-kernel - [PATCH] mdio: mux: Correct mdio_mux

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Date:   Wed, 10 May 2017 11:20:27 -0400
From:   Jon Mason <jon.mason@...adcom.com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        bcm-kernel-feedback-list@...adcom.com
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 <jon.mason@...adcom.com>
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);
 			of_node_put(child_bus_node);
 			break;
 		}
@@ -169,8 +169,8 @@ int mdio_mux_init(struct device *dev,
 		if (r) {
 			mdiobus_free(cb->mii_bus);
 			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);
+err_pb_kz:
 	/* balance the reference of_mdio_find_bus() took */
-	put_device(&pb->mii_bus->dev);
-
+	if (!mux_bus)
+		put_device(&parent_bus->dev);
 err_parent_bus:
 	of_node_put(parent_bus_node);
 	return ret_val;
-- 
2.7.4