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Date: Sun, 17 Apr 2022 09:28:25 +0200 From: Lukas Wunner <lukas@...ner.de> To: Greg Kroah-Hartman <gregkh@...uxfoundation.org> Cc: Oliver Neukum <oneukum@...e.com>, "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Jann Horn <jannh@...gle.com>, Oleksij Rempel <o.rempel@...gutronix.de>, netdev@...r.kernel.org, linux-usb@...r.kernel.org, Andrew Lunn <andrew@...n.ch>, Eric Dumazet <edumazet@...gle.com>, Jacky Chou <jackychou@...x.com.tw>, Willy Tarreau <w@....eu>, Lino Sanfilippo <LinoSanfilippo@....de>, Philipp Rosenberger <p.rosenberger@...bus.com>, Heiner Kallweit <hkallweit1@...il.com> Subject: Re: [PATCH] usbnet: Fix use-after-free on disconnect On Thu, Apr 14, 2022 at 01:07:35PM +0200, Greg Kroah-Hartman wrote: > On Thu, Apr 14, 2022 at 12:58:58PM +0200, Lukas Wunner wrote: > > On Wed, Apr 13, 2022 at 08:59:48PM +0200, Oliver Neukum wrote: > > > On 13.04.22 16:16, Lukas Wunner wrote: > > > > --- a/drivers/net/usb/usbnet.c > > > > +++ b/drivers/net/usb/usbnet.c > > > > @@ -469,6 +469,9 @@ static enum skb_state defer_bh(struct usbnet *dev, struct sk_buff *skb, > > > > */ > > > > void usbnet_defer_kevent (struct usbnet *dev, int work) > > > > { > > > > + if (dev->intf->condition == USB_INTERFACE_UNBINDING) > > > > + return; > > > > > > But, no, you cannot do this. This is a very blatant layering violation. > > > You cannot use states internal to usb core like that in a driver. > > > > Why do you think it's internal? > > > > enum usb_interface_condition is defined in include/linux/usb.h > > for everyone to see and use. If it was meant to be private, > > I'd expect it to be marked as such or live in drivers/usb/core/usb.h. > > Because we didn't think people would do crazy things like this. I assume "crazy things" encompasses reading and writing intf->condition without any locking or explicit memory barriers. However many drivers do that through the exported functions: usb_reset_device() usb_lock_device_for_reset() usb_driver_claim_interface() usb_driver_release_interface() In any case, I've decided to pursue a different approach which fixes the issue in core networking code rather than usbnet. USB Ethernet may not be the only culprit after all. A replacement patch superseding this one was just submitted: https://lore.kernel.org/netdev/18b3541e5372bc9b9fc733d422f4e698c089077c.1650177997.git.lukas@wunner.de Thanks, Lukas
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