[PATCH 4.4 106/137] xhci: Fix list corruption in urb dequeue at host removal

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>

commit 5c82171167adb8e4ac77b91a42cd49fb211a81a0 upstream.

xhci driver frees data for all devices, both usb2 and and usb3 the
first time usb_remove_hcd() is called, including td_list and and xhci_ring
structures.

When usb_remove_hcd() is called a second time for the second xhci bus it
will try to dequeue all pending urbs, and touches td_list which is already
freed for that endpoint.

Reported-by: Joe Lawrence <joe.lawrence@xxxxxxxxxxx>
Tested-by: Joe Lawrence <joe.lawrence@xxxxxxxxxxx>
Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/host/xhci.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -1549,7 +1549,9 @@ int xhci_urb_dequeue(struct usb_hcd *hcd
 		xhci_dbg_trace(xhci, trace_xhci_dbg_cancel_urb,
 				"HW died, freeing TD.");
 		urb_priv = urb->hcpriv;
-		for (i = urb_priv->td_cnt; i < urb_priv->length; i++) {
+		for (i = urb_priv->td_cnt;
+		     i < urb_priv->length && xhci->devs[urb->dev->slot_id];
+		     i++) {
 			td = urb_priv->td[i];
 			if (!list_empty(&td->td_list))
 				list_del_init(&td->td_list);