netdev - Re: [PATCH net-next 1/7] usbnet: Run unregister

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Message-ID: <f332cdf1-90c8-bfd0-b019-a398b8f4e58c@suse.com>
Date:   Wed, 27 Apr 2022 09:44:54 +0200
From:   Oliver Neukum <oneukum@...e.com>
To:     Lukas Wunner <lukas@...ner.de>,
        Steve Glendinning <steve.glendinning@...well.net>,
        UNGLinuxDriver@...rochip.com, Oliver Neukum <oneukum@...e.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, linux-usb@...r.kernel.org,
        Andre Edich <andre.edich@...rochip.com>,
        Oleksij Rempel <o.rempel@...gutronix.de>,
        Martyn Welch <martyn.welch@...labora.com>,
        Gabriel Hojda <ghojda@...urs.ro>,
        Christoph Fritz <chf.fritz@...glemail.com>,
        Lino Sanfilippo <LinoSanfilippo@....de>,
        Philipp Rosenberger <p.rosenberger@...bus.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Russell King <linux@...linux.org.uk>
Subject: Re: [PATCH net-next 1/7] usbnet: Run unregister_netdev() before
 unbind() again



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@...ner.de>
> Cc: Oleksij Rempel <o.rempel@...gutronix.de>
> Cc: Martyn Welch <martyn.welch@...labora.com>
> Cc: Andrew Lunn <andrew@...n.ch>
>
Acked-by: Oliver Neukum <oneukum@...e.com>