[PATCH] USB: usbcore: usb_set_configuration oops (NULL ptr dereference)

When trying to deconfigure a device via usb_set_configuration(dev, 0),
2.6.16-rc kernels after 55c527187c oops
with "Unable to handle NULL pointer dereference at...". This is due to
an unchecked dereference of cp in the power budget part.

This patch was already included in Linus' tree.

Signed-off-by: Horst Schirmeier <horst@schirmeier.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>

drivers/usb/core/message.c

@@ -1388,11 +1388,13 @@ free_interfaces:
 	if (dev->state != USB_STATE_ADDRESS)
 		usb_disable_device (dev, 1);	// Skip ep0
 
-	i = dev->bus_mA - cp->desc.bMaxPower * 2;
-	if (i < 0)
-		dev_warn(&dev->dev, "new config #%d exceeds power "
-				"limit by %dmA\n",
-				configuration, -i);
+	if (cp) {
+		i = dev->bus_mA - cp->desc.bMaxPower * 2;
+		if (i < 0)
+			dev_warn(&dev->dev, "new config #%d exceeds power "
+					"limit by %dmA\n",
+					configuration, -i);
+	}
 
 	if ((ret = usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
 			USB_REQ_SET_CONFIGURATION, 0, configuration, 0,