net: phy: fix potential race in the phylib state machine

hkallweit · davem330 · commit a20049071796 · 2019-02-14T12:04:55.000-05:00
Russell reported the following race in the phylib state machine (quoting from his mail): if (phy_polling_mode(phydev) && phy_is_started(phydev)) phy_queue_state_machine(phydev, PHY_STATE_TIME); state = PHY_UP thread 0 thread 1 phy_disconnect() +-phy_is_started() phy_is_started() | `-phy_stop() +-phydev->state = PHY_HALTED `-phy_stop_machine() `-cancel_delayed_work_sync() phy_queue_state_machine() `-mod_delayed_work() At this point, the phydev->state_queue() has been added back onto the system workqueue despite phy_stop_machine() having been called and cancel_delayed_work_sync() called on it. Fix this by protecting the complete operation in thread 0. Fixes: 2b3e88e ("net: phy: improve phy state checking") Reported-by: Russell King - ARM Linux admin <linux@armlinux.org.uk> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com> Reviewed-by: Florian Fainelli <f.fainelli@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
@@ -985,8 +985,10 @@ void phy_state_machine(struct work_struct *work)
 	 * state machine would be pointless and possibly error prone when
 	 * called from phy_disconnect() synchronously.
 	 */
+	mutex_lock(&phydev->lock);
 	if (phy_polling_mode(phydev) && phy_is_started(phydev))
 		phy_queue_state_machine(phydev, PHY_STATE_TIME);
+	mutex_unlock(&phydev->lock);
 }
 
 /**
