usb: add pid check at the first of uhci_handle_td()

pid can be gotten from uhci device memory in uhci_handle_td(),
so the guest can trigger assert qemu if we get an invalid pid.
And the uhci spec 2.1.2 tells us The Host Controller sets Host
Controller Process Error bit to 1 when it detects a fatal error
and indicates that the Host Controller suffered a consistency
check failure while processing a Transfer Descriptor. An example
of a consistency check failure would be finding an illegal PID
field while processing the packet header portion of the TD.
When this error occurs, the Host Controller clears the Run/Stop
bit in the Command register to prevent further schedule execution.

We'd better to set UHCI_STS_HCPERR and kick an interrupt, check
the pid value at the first of uhci_handle_td function.

https://bugzilla.redhat.com/show_bug.cgi?id=1070027Signed-off-by: NGonglei <arei.gonglei@huawei.com>
Message-id: 1455867238-4720-1-git-send-email-arei.gonglei@huawei.com

[ applied minor codestyle fix ]
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

hw/usb/hcd-uhci.c

@@ -773,8 +773,22 @@ static int uhci_handle_td(UHCIState *s, UHCIQueue *q, uint32_t qh_addr,
     bool spd;
     bool queuing = (q != NULL);
     uint8_t pid = td->token & 0xff;
-    UHCIAsync *async = uhci_async_find_td(s, td_addr);
+    UHCIAsync *async;
+
+    switch (pid) {
+    case USB_TOKEN_OUT:
+    case USB_TOKEN_SETUP:
+    case USB_TOKEN_IN:
+        break;
+    default:
+        /* invalid pid : frame interrupted */
+        s->status |= UHCI_STS_HCPERR;
+        s->cmd &= ~UHCI_CMD_RS;
+        uhci_update_irq(s);
+        return TD_RESULT_STOP_FRAME;
+    }
 
+    async = uhci_async_find_td(s, td_addr);
     if (async) {
         if (uhci_queue_verify(async->queue, qh_addr, td, td_addr, queuing)) {
             assert(q == NULL || q == async->queue);
@@ -880,11 +894,7 @@ static int uhci_handle_td(UHCIState *s, UHCIQueue *q, uint32_t qh_addr,
         break;
 
     default:
-        /* invalid pid : frame interrupted */
-        uhci_async_free(async);
-        s->status |= UHCI_STS_HCPERR;
-        uhci_update_irq(s);
-        return TD_RESULT_STOP_FRAME;
+        abort(); /* Never to execute */
     }
 
     if (async->packet.status == USB_RET_ASYNC) {