On Wed, Oct 04, 2017 at 08:10:59AM +0200, Takashi Iwai wrote: > On Tue, 03 Oct 2017 19:42:21 +0200, > Greg Kroah-Hartman wrote: > > > > 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/ > > subdir... Yeah, I only swept the tree for instances were a missing endpoint could lead to a NULL-deref. This is not the case here were the endpoint addresses are hardcoded in the driver. I also never got around to applying the new helper outside of drivers/usb. > Well, what I had in my mind is just a snippet from usb_submit_urb(), > something like: > > bool usb_sanity_check_urb_pipe(struct urb *urb) > { > struct usb_host_endpoint *ep; > int xfertype; > static const int pipetypes[4] = { > PIPE_CONTROL, PIPE_ISOCHRONOUS, PIPE_BULK, PIPE_INTERRUPT > }; > > ep = usb_pipe_endpoint(urb->dev, urb->pipe); > xfertype = usb_endpoint_type(&ep->desc); > return usb_pipetype(urb->pipe) != pipetypes[xfertype]; > } > > And calling this before usb_submit_urb() in each place that assigns > the fixed EP as device-specific quirks. > Does it make sense? Not really. Your driver should not even bind to an interface which lacks the expected endpoints (rather than check this at a potentially later point in time when URBs are submitted). The new helper which Greg mentioned would allow this to implemented with just a few lines of code. Just add it to bcd2000_init_midi() or similar. Thanks, Johan -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html