Re: usb/sound/bcd2000: warning in bcd2000_init_device

From: Greg Kroah-Hartman
Date: Tue Oct 03 2017 - 13:42:17 EST

On Tue, Oct 03, 2017 at 12:50:08PM -0400, Alan Stern wrote:
> 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.

We have almost this type of function, usb_find_common_endpoints(),
what's wrong with using that? Johan has already swept the tree and
added a lot of these checks, odds are no one looked at the sound/


greg k-h