[PATCH 4.14 13/33] phy: mdio: fix memory leak

Greg Kroah-Hartman
2021-10-14T14:57:54Z

From: Pavel Skripkin <paskripkin@gmail.com>

[ Upstream commit ca6e11c337daf7925ff8a2aac8e84490a8691905 ]

Syzbot reported memory leak in MDIO bus interface, the problem was in
wrong state logic.

MDIOBUS_ALLOCATED indicates 2 states:
1. Bus is only allocated
2. Bus allocated and __mdiobus_register() fails, but
device_register() was called

In case of device_register() has been called we should call put_device()
to correctly free the memory allocated for this device, but mdiobus_free()
calls just kfree(dev) in case of MDIOBUS_ALLOCATED state

To avoid this behaviour we need to set bus->state to MDIOBUS_UNREGISTERED
_before_ calling device_register(), because put_device() should be
called even in case of device_register() failure.

Link: https://lore.kernel.org/netdev/YVMRWNDZDUOvQjHL@shell.armlinux.org.uk/
Fixes: 46abc02175b3 ("phylib: give mdio buses a device tree presence")
Reported-and-tested-by: syzbot+398e7dc692ddbbb4cfec@syzkaller.appspotmail.com
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Link: https://lore.kernel.org/r/eceae1429fbf8fa5c73dd2a0d39d525aa905074d.1633024062.git.paskripkin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/phy/mdio_bus.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 5fc7b6c1a442..5ef9bbbab3db 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -344,6 +344,13 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
bus->dev.groups = NULL;
dev_set_name(&bus->dev, "%s", bus->id);

+ /* We need to set state to MDIOBUS_UNREGISTERED to correctly release
+ * the device in mdiobus_free()
+ *
+ * State will be updated later in this function in case of success
+ */
+ bus->state = MDIOBUS_UNREGISTERED;
+
err = device_register(&bus->dev);
if (err) {
pr_err("mii_bus %s failed to register\n", bus->id);
--
2.33.0