On Wed, Apr 13, 2022 at 08:59:48PM +0200, Oliver Neukum wrote:
> On 13.04.22 16:16, Lukas Wunner wrote:
> > Jann Horn reports a use-after-free on disconnect of a USB Ethernet
> > (ax88179_178a.c). Oleksij Rempel has witnessed the same issue with a
> > different driver (ax88172a.c).
>
> I see. Very good catch
>
> > --- 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.
Adding Greg to clarify.
> I see two options.
> 1. A dedicated flag in usbnet (then please with the correct smp barriers)
> 2. You introduce an API to usb core to query this.
I'd definitely prefer option 2 as I'd hate to duplicate functionality.
What do you have in mind? A simple accessor to return intf->condition
or something like usb_interface_unbinding() which returns a bool?
Thanks,
Lukas
