[PATCH 4.19 20/37] net: phy: Avoid NPD upon phy_detach() when driver is unbound

Greg Kroah-Hartman
2020-09-25T12:54:11Z

From: Florian Fainelli <f.fainelli@gmail.com>

[ Upstream commit c2b727df7caa33876e7066bde090f40001b6d643 ]

If we have unbound the PHY driver prior to calling phy_detach() (often
via phy_disconnect()) then we can cause a NULL pointer de-reference
accessing the driver owner member. The steps to reproduce are:

echo unimac-mdio-0:01 > /sys/class/net/eth0/phydev/driver/unbind
ip link set eth0 down

Fixes: cafe8df8b9bc ("net: phy: Fix lack of reference count on PHY driver")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/phy/phy_device.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -1154,7 +1154,8 @@ void phy_detach(struct phy_device *phyde

phy_led_triggers_unregister(phydev);

- module_put(phydev->mdio.dev.driver->owner);
+ if (phydev->mdio.dev.driver)
+ module_put(phydev->mdio.dev.driver->owner);

/* If the device had no specific driver before (i.e. - it
* was using the generic driver), we unbind the device