Commit d1408f6b authored by Lukas Wunner's avatar Lukas Wunner Committed by David S. Miller
Browse files

usbnet: Run unregister_netdev() before unbind() again 

Commit 2c9d6c2b ("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: default avatarLukas Wunner <lukas@wunner.de>
Acked-by: default avatarOliver Neukum <oneukum@suse.com>
Cc: Martyn Welch <martyn.welch@collabora.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7b8b8222

drivers/net/usb/asix_devices.c

+1 −5
Original line number Diff line number Diff line
@@ -795,10 +795,6 @@ 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);



	return 0;

drivers/net/usb/smsc95xx.c

+1 −2
Original line number Diff line number Diff line
@@ -1243,7 +1243,6 @@ static int smsc95xx_start_phy(struct usbnet *dev) 


static int smsc95xx_stop(struct usbnet *dev)

{

	if (dev->net->phydev)

	phy_stop(dev->net->phydev);



	return 0;

drivers/net/usb/usbnet.c

+3 −3
Original line number Diff line number Diff line
@@ -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);