xhci: fix segfault

Guest trying to reset a endpoint of a disconnected device resulted in
xhci trying to dereference uport while being NULL, thereby crashing
qemu.  Fix that by adding a check.  Drop unused dev variable while
touching that code bit.

Cc: qemu-stable@nongnu.org
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit 75cc1c1fcba1987bdf3979c4289ab756c2b15742)

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/hw/usb/hcd-xhci.c b/hw/usb/hcd-xhci.c
index 632ede8497dcecd2ce4973b8cbb07e866c5dc847..d88c1ae8c07b20a853ba1f30a2a29df9fb7de294 100644 (file)
--- a/hw/usb/hcd-xhci.c
+++ b/hw/usb/hcd-xhci.c
@@ -1395,7 +1395,6 @@ static TRBCCode xhci_reset_ep(XHCIState *xhci, unsigned int slotid,
 {
     XHCISlot *slot;
     XHCIEPContext *epctx;
-    USBDevice *dev;
 
     trace_usb_xhci_ep_reset(slotid, epid);
     assert(slotid >= 1 && slotid <= xhci->numslots);
@@ -1431,8 +1430,8 @@ static TRBCCode xhci_reset_ep(XHCIState *xhci, unsigned int slotid,
         ep |= 0x80;
     }
 
-    dev = xhci->slots[slotid-1].uport->dev;
-    if (!dev) {
+    if (!xhci->slots[slotid-1].uport ||
+        !xhci->slots[slotid-1].uport->dev) {
         return CC_USB_TRANSACTION_ERROR;
     }