Re: [PATCH net-next 1/7] usbnet: Run unregister_netdev() before unbind() again

[Oliver Neukum <oneukum@suse.com>]

On 27.04.22 07:48, Lukas Wunner wrote:
> 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().
>
> Signed-off-by: Lukas Wunner <lukas@wunner.de>
> Cc: Oleksij Rempel <o.rempel@pengutronix.de>
> Cc: Martyn Welch <martyn.welch@collabora.com>
> Cc: Andrew Lunn <andrew@lunn.ch>
>
Acked-by: Oliver Neukum <oneukum@suse.com>