[PATCH 4.19 40/86] phylib: fix potential use-after-free

[Greg Kroah-Hartman]

From: Marek Behún <kabel@xxxxxxxxxx>

[ Upstream commit cbda1b16687580d5beee38273f6241ae3725960c ]

Commit bafbdd527d56 ("phylib: Add device reset GPIO support") added call
to phy_device_reset(phydev) after the put_device() call in phy_detach().

The comment before the put_device() call says that the phydev might go
away with put_device().

Fix potential use-after-free by calling phy_device_reset() before
put_device().

Fixes: bafbdd527d56 ("phylib: Add device reset GPIO support")
Signed-off-by: Marek Behún <kabel@xxxxxxxxxx>
Reviewed-by: Andrew Lunn <andrew@xxxxxxx>
Link: https://lore.kernel.org/r/20220119162748.32418-1-kabel@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/net/phy/phy_device.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index b884b681d5c52..a03d0627efb06 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -1166,6 +1166,9 @@ void phy_detach(struct phy_device *phydev)
 	    phydev->mdio.dev.driver == &genphy_driver.mdiodrv.driver)
 		device_release_driver(&phydev->mdio.dev);
 
+	/* Assert the reset signal */
+	phy_device_reset(phydev, 1);
+
 	/*
 	 * The phydev might go away on the put_device() below, so avoid
 	 * a use-after-free bug by reading the underlying bus first.
@@ -1175,9 +1178,6 @@ void phy_detach(struct phy_device *phydev)
 	put_device(&phydev->mdio.dev);
 	if (ndev_owner != bus->owner)
 		module_put(bus->owner);
-
-	/* Assert the reset signal */
-	phy_device_reset(phydev, 1);
 }
 EXPORT_SYMBOL(phy_detach);
 
-- 
2.34.1