USB: Prepare for refactoring by adding extra udev checks.

[This is upstream commit 2d4fa940.
It needs to be backported to kernels as old as 3.2, because it fixes the
buggy commit 65bdac5e "USB: Handle warm
reset failure on empty port."]

The next patch will refactor the hub port code to rip out the recursive
call to hub_port_reset on a failed hot reset.  In preparation for that,
make sure all code paths can deal with being called with a NULL udev.
The usb_device will not be valid if warm reset was issued because a port
transitioned to the Inactive or Compliance Mode on a device connect.

This patch should have no effect on current behavior.
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/hub.c

@@ -2584,6 +2584,9 @@ static int hub_port_wait_reset(struct usb_hub *hub, int port1,
 				return -ENOTCONN;
 
 			if ((portstatus & USB_PORT_STAT_ENABLE)) {
+				if (!udev)
+					return 0;
+
 				if (hub_is_wusb(hub))
 					udev->speed = USB_SPEED_WIRELESS;
 				else if (hub_is_superspeed(hub->hdev))
@@ -2627,14 +2630,16 @@ static void hub_port_finish_reset(struct usb_hub *hub, int port1,
 			struct usb_hcd *hcd;
 			/* TRSTRCY = 10 ms; plus some extra */
 			msleep(10 + 40);
+			if (udev) {
 				update_devnum(udev, 0);
 				hcd = bus_to_hcd(udev->bus);
-			/* The xHC may think the device is already reset,
-			 * so ignore the status.
+				/* The xHC may think the device is already
+				 * reset, so ignore the status.
 				 */
 				if (hcd->driver->reset_device)
 					hcd->driver->reset_device(hcd, udev);
 			}
+		}
 		/* FALL THROUGH */
 	case -ENOTCONN:
 	case -ENODEV:
@@ -2647,7 +2652,7 @@ static void hub_port_finish_reset(struct usb_hub *hub, int port1,
 			clear_port_feature(hub->hdev, port1,
 					USB_PORT_FEAT_C_PORT_LINK_STATE);
 		}
-		if (!warm)
+		if (!warm && udev)
 			usb_set_device_state(udev, *status
 					? USB_STATE_NOTATTACHED
 					: USB_STATE_DEFAULT);