[RFC PATCH net-next 2/3] net: dsa: destroy the phylink instance on any error in dsa_slave_phy_setup

[Vladimir Oltean <vladimir.oltean@nxp.com>]

DSA supports connecting to a phy-handle, and has a fallback to a non-OF
based method of connecting to an internal PHY on the switch's own MDIO
bus, if no phy-handle and no fixed-link nodes were present.

The -ENODEV error code from the first attempt (phylink_of_phy_connect)
is what triggers the second attempt (phylink_connect_phy).

However, when the first attempt returns a different error code than
-ENODEV, this results in an unbalance of calls to phylink_create and
phylink_destroy by the time we exit the function. The phylink instance
has leaked.

There are many other error codes that can be returned by
phylink_of_phy_connect. For example, phylink_validate returns -EINVAL.
So this is a practical issue too.

Fixes: aab9c4067d23 ("net: dsa: Plug in PHYLINK support")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
I know, I will send this bug fix to "net" too, this is provided just for
testing purposes, and for the completeness of the patch set.

 net/dsa/slave.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index a7a114b9cb77..8a395290267c 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -1856,13 +1856,11 @@ static int dsa_slave_phy_setup(struct net_device *slave_dev)
 		 * use the switch internal MDIO bus instead
 		 */
 		ret = dsa_slave_phy_connect(slave_dev, dp->index, phy_flags);
-		if (ret) {
-			netdev_err(slave_dev,
-				   "failed to connect to port %d: %d\n",
-				   dp->index, ret);
-			phylink_destroy(dp->pl);
-			return ret;
-		}
+	}
+	if (ret) {
+		netdev_err(slave_dev, "failed to connect to PHY: %pe\n",
+			   ERR_PTR(ret));
+		phylink_destroy(dp->pl);
 	}
 
 	return ret;
-- 
2.25.1