Subject: [PATCH 37/54] net: phy: Avoid NPD upon phy_detach() when driver is unbound

From: Florian Fainelli <[email-masked]>
Date: Wed, 16 Sep 2020 20:43:09 -0700

[ 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 <[email-masked]>
Reviewed-by: Andrew Lunn <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 drivers/net/phy/phy_device.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index aa23fd0ccc53..067910d242ab 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -1631,7 +1631,8 @@ void phy_detach(struct phy_device *phydev)
 
 	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
-- 
2.26.2