phy: phy_ethtool_ksettings_set: Lock the PHY while changing settings

There is a race condition where the PHY state machine can change
members of the phydev structure at the same time userspace requests a
change via ethtool. To prevent this, have phy_ethtool_ksettings_set
take the PHY lock.

Fixes: 2d55173e ("phy: add generic function to support ksetting support")
Reported-by: Walter Stoll <Walter.Stoll@duagon.com>
Suggested-by: Walter Stoll <Walter.Stoll@duagon.com>
Tested-by: Walter Stoll <Walter.Stoll@duagon.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/phy.c

@@ -798,6 +798,7 @@ int phy_ethtool_ksettings_set(struct phy_device *phydev,
 	      duplex != DUPLEX_FULL)))
 		return -EINVAL;
 
+	mutex_lock(&phydev->lock);
 	phydev->autoneg = autoneg;
 
 	if (autoneg == AUTONEG_DISABLE) {
@@ -814,8 +815,9 @@ int phy_ethtool_ksettings_set(struct phy_device *phydev,
 	phydev->mdix_ctrl = cmd->base.eth_tp_mdix_ctrl;
 
 	/* Restart the PHY */
-	phy_start_aneg(phydev);
+	_phy_start_aneg(phydev);
 
+	mutex_unlock(&phydev->lock);
 	return 0;
 }
 EXPORT_SYMBOL(phy_ethtool_ksettings_set);