net: phy: fix potential race in the phylib state machine
authorHeiner Kallweit <hkallweit1@gmail.com>
Wed, 13 Feb 2019 19:12:54 +0000 (20:12 +0100)
committerDavid S. Miller <davem@davemloft.net>
Thu, 14 Feb 2019 17:04:55 +0000 (12:04 -0500)
commita20049071796691cf99eb6433968fc3c27632b95
tree5c4576e502af6717242dee142475bf318856d0cc
parenta2fc9d7e36f6d484d9be4a0a204400aaf6059544
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: 2b3e88ea6528 ("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>
drivers/net/phy/phy.c