Re: usb/sound/bcd2000: warning in bcd2000_init_device

From: Alan Stern
Date: Tue Oct 03 2017 - 12:50:13 EST

On Tue, 3 Oct 2017, Takashi Iwai wrote:

> > It's a dev_WARN because it indicates a potentially serious error in the
> > driver: The driver has submitted an interrupt URB to a bulk endpoint.
> > That may not sound bad, but the same check gets triggered if a driver
> > submits a bulk URB to an isochronous endpoint, or any other invalid
> > combination.
> >
> > Most likely the explanation here is that the driver doesn't bother to
> > check the endpoint type because it expects the endpoint will always be
> > interrupt. But that is not a safe strategy. USB devices and their
> > firmware should not be trusted unnecessarily.
> >
> > The best fix is, like you said, to add a sanity check in the caller.
> OK, but then do we have some handy helper for the check?
> As other bug reports by syzkaller suggest, there are a few other
> drivers that do the same, submitting a urb with naive assumption of
> the fixed EP for specific devices. In the end we'll need to put the
> very same checks there in multiple places.

Perhaps we could add a helper routine that would take a list of
expected endpoint types and check that the actual endpoints match the
types. But of course, all the drivers you're talking about would have
to add a call to this helper routine.

Alan Stern