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

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: 2b3e88ea65 ("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>
This commit is contained in:
Heiner Kallweit 2019-02-13 20:12:54 +01:00 committed by David S. Miller
parent a2fc9d7e36
commit a200490717
1 changed files with 2 additions and 0 deletions
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2
drivers/net/phy/phy.c
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@ -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);
}
/**