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

Greg Kroah-Hartman
2022-02-07T11:25:11Z

From: Marek Behún <kabel@kernel.org>

[ 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@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20220119162748.32418-1-kabel@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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