[PATCH AUTOSEL 5.17 099/135] usbnet: Run unregister_netdev() before unbind() again

Sasha Levin
2022-05-30T14:03:27Z

From: Lukas Wunner <lukas@wunner.de>

[ Upstream commit d1408f6b4dd78fb1b9e26bcf64477984e5f85409 ]

Commit 2c9d6c2b871d ("usbnet: run unbind() before unregister_netdev()")
sought to fix a use-after-free on disconnect of USB Ethernet adapters.

It turns out that a different fix is necessary to address the issue:
https://lore.kernel.org/netdev/18b3541e5372bc9b9fc733d422f4e698c089077c.1650177997.git.lukas@wunner.de/

So the commit was not necessary.

The commit made binding and unbinding of USB Ethernet asymmetrical:
Before, usbnet_probe() first invoked the ->bind() callback and then
register_netdev(). usbnet_disconnect() mirrored that by first invoking
unregister_netdev() and then ->unbind().

Since the commit, the order in usbnet_disconnect() is reversed and no
longer mirrors usbnet_probe().

One consequence is that a PHY disconnected (and stopped) in ->unbind()
is afterwards stopped once more by unregister_netdev() as it closes the
netdev before unregistering. That necessitates a contortion in ->stop()
because the PHY may only be stopped if it hasn't already been
disconnected.

Reverting the commit allows making the call to phy_stop() unconditional
in ->stop().

Tested-by: Oleksij Rempel <o.rempel@pengutronix.de> # LAN9514/9512/9500
Tested-by: Ferry Toth <fntoth@gmail.com> # LAN9514
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Acked-by: Oliver Neukum <oneukum@suse.com>
Cc: Martyn Welch <martyn.welch@collabora.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/usb/asix_devices.c | 6 +-----
drivers/net/usb/smsc95xx.c | 3 +--
drivers/net/usb/usbnet.c | 6 +++---
3 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/drivers/net/usb/asix_devices.c b/drivers/net/usb/asix_devices.c
index 6b2fbdf4e0fd..34854ee537dc 100644
--- a/drivers/net/usb/asix_devices.c
+++ b/drivers/net/usb/asix_devices.c
@@ -799,11 +799,7 @@ static int ax88772_stop(struct usbnet *dev)
{
struct asix_common_private *priv = dev->driver_priv;

- /* On unplugged USB, we will get MDIO communication errors and the
- * PHY will be set in to PHY_HALTED state.
- */
- if (priv->phydev->state != PHY_HALTED)
- phy_stop(priv->phydev);
+ phy_stop(priv->phydev);

return 0;
}
diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
index a0f29482294d..d81485cd7e90 100644
--- a/drivers/net/usb/smsc95xx.c
+++ b/drivers/net/usb/smsc95xx.c
@@ -1218,8 +1218,7 @@ static int smsc95xx_start_phy(struct usbnet *dev)

static int smsc95xx_stop(struct usbnet *dev)
{
- if (dev->net->phydev)
- phy_stop(dev->net->phydev);
+ phy_stop(dev->net->phydev);

return 0;
}
diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 9a6450f796dc..36b24ec11650 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -1616,9 +1616,6 @@ void usbnet_disconnect (struct usb_interface *intf)
xdev->bus->bus_name, xdev->devpath,
dev->driver_info->description);

- if (dev->driver_info->unbind)
- dev->driver_info->unbind(dev, intf);
-
net = dev->net;
unregister_netdev (net);

@@ -1626,6 +1623,9 @@ void usbnet_disconnect (struct usb_interface *intf)

usb_scuttle_anchored_urbs(&dev->deferred);

+ if (dev->driver_info->unbind)
+ dev->driver_info->unbind(dev, intf);
+
usb_kill_urb(dev->interrupt);
usb_free_urb(dev->interrupt);
kfree(dev->padding_pkt);
--
2.35.1