ohci: check device is not NULL before calling usb_ep_get()

A call to ohci_find_device() can return NULL if it doesn't find a
device matching 'addr' so for the two callers, explicitly check
the return value before passing it to usb_ep_get().

Signed-off-by: Liam Merwick <liam.merwick@oracle.com>
Message-id: 1549460216-25808-6-git-send-email-liam.merwick@oracle.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

hw/usb/hcd-ohci.c

@@ -848,6 +848,10 @@ static int ohci_service_iso_td(OHCIState *ohci, struct ohci_ed *ed,
         bool int_req = relative_frame_number == frame_count &&
                        OHCI_BM(iso_td.flags, TD_DI) == 0;
         dev = ohci_find_device(ohci, OHCI_BM(ed->flags, ED_FA));
+        if (dev == NULL) {
+            trace_usb_ohci_td_dev_error();
+            return 1;
+        }
         ep = usb_ep_get(dev, pid, OHCI_BM(ed->flags, ED_EN));
         usb_packet_setup(&ohci->usb_packet, pid, ep, 0, addr, false, int_req);
         usb_packet_addbuf(&ohci->usb_packet, ohci->usb_buf, len);
@@ -1071,6 +1075,10 @@ static int ohci_service_td(OHCIState *ohci, struct ohci_ed *ed)
             return 1;
         }
         dev = ohci_find_device(ohci, OHCI_BM(ed->flags, ED_FA));
+        if (dev == NULL) {
+            trace_usb_ohci_td_dev_error();
+            return 1;
+        }
         ep = usb_ep_get(dev, pid, OHCI_BM(ed->flags, ED_EN));
         usb_packet_setup(&ohci->usb_packet, pid, ep, 0, addr, !flag_r,
                          OHCI_BM(td.flags, TD_DI) == 0);