On Sat, Jun 26, 2021 at 10:21 PM Qiang Liu <cyruscy...@gmail.com> wrote: > > Hi folks, > > I found this bug by my dwc2 fuzzer. > It seems that > * https://bugs.launchpad.net/qemu/+bug/1907042 > * https://bugs.launchpad.net/qemu/+bug/1525123 > or > * https://gitlab.com/qemu-project/qemu/-/issues/119 > * https://gitlab.com/qemu-project/qemu/-/issues/303 > have reported similar issues. > > Would it be better to consider and fix them together? > > Best, > Qiang > > On Sun, Jun 27, 2021 at 11:28 AM Qiang Liu <cyruscy...@gmail.com> wrote: > > > > When eptype is USB_ENDPOINT_XFER_CONTROL and pid is > > TSIZ_SC_MC_PID_SETUP, usb_ep_get() should return the control endpoint. > > In hw/usb/core.c, the assumed epnum of the control endpoint is 0. When > > epnum is not 0, usb_ep_get() will crash due to the check assert(pid == > > USB_TOKEN_IN || pid == USB_TOKEN_OUT). > > > > The description > > http://www.capital-micro.com/PDF/CME-M7_Family_User_Guide_EN.pdf > > (18.5.3.4 (14), 18.5.3.4 (10)) a) mentions that the pid is maintained by > > the host, b) but doesn't mention that whether the epnum should be 0 for > > the control endpoint. However, usb_ep_get() assumes it is 0. To avoid > > potential assertion failure in usb_ep_get(), we could enforce epnum to 0 > > and warn users. > > > > Fixes: 153ef1662c3 ("dwc-hsotg (dwc2) USB host controller emulation") > > Signed-off-by: Qiang Liu <cyruscy...@gmail.com> > > --- > > hw/usb/hcd-dwc2.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/hw/usb/hcd-dwc2.c b/hw/usb/hcd-dwc2.c > > index e1d96ac..65d9d46 100644 > > --- a/hw/usb/hcd-dwc2.c > > +++ b/hw/usb/hcd-dwc2.c > > @@ -636,6 +636,11 @@ static void dwc2_enable_chan(DWC2State *s, uint32_t > > index) > > } > > > > if (eptype == USB_ENDPOINT_XFER_CONTROL && pid == > > TSIZ_SC_MC_PID_SETUP) { > > + if (epnum != 0) { > > + qemu_log_mask(LOG_GUEST_ERROR, > > + "epnum should be 0 for the control endpoint\n"); > > + epnum = 0; > > + } > > pid = USB_TOKEN_SETUP; > > } else { > > pid = epdir ? USB_TOKEN_IN : USB_TOKEN_OUT; > > -- > > 2.7.4 > >
Hi Qiang, Sorry for the late reply, I've had a busy week. Yes, I think it would be best to fix this in the core since it affects more than one host. I'm not sure that forcing the Control endpoint to 0 is the best solution though, perhaps it would be better to print an error message and fail the operation? AFAIK there are no real-world devices that have Control endpoints other than 0, although I believe it is allowed by the USB spec. Let's wait and see what Gerd thinks. - Paul
