[PATCH] Input: xpad - fix oops when attaching an unknown Xbox One gamepad

[Cameron Gutman <aicommander@gmail.com>]

Xbox One controllers have multiple interfaces which all have the
same class, subclass, and protocol. One of the these interfaces
has only a single endpoint. When Xpad attempts to bind to this
interface, it causes an oops when trying initialize the output URB
by trying to access the second endpoint's descriptor.

This situation was avoided for known Xbox One devices by checking
the XTYPE constant associated with the VID and PID tuple. However,
this breaks when new or previously unknown Xbox One controllers
are attached to the system.

This change addresses the problem by deriving the XTYPE for Xbox
One controllers based on the interface protocol before checking
the interface number.

Fixes: 1a48ff81b391 ("Input: xpad - add support for Xbox One controllers")
Signed-off-by: Cameron Gutman <aicommander@gmail.com>
Cc: stable@vger.kernel.org
---
This bug affects kernels since 3.18. Controllers upgraded to the 2015
firmware will trigger the oops on affected kernels (up to 4.4 when the
new device ID was added). The Xbox One Elite controller will likely
also trigger the oops up to 4.6 (though I've not tested myself) along
with any new third-party Xbox One controllers that are released.

There are a few ways we could address it, but this one seems nice
because it allows the controller to work correctly (as opposed to simply
kicking out interfaces without enough endpoints).
---
 drivers/input/joystick/xpad.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/input/joystick/xpad.c b/drivers/input/joystick/xpad.c
index 923c572..3438e98 100644
--- a/drivers/input/joystick/xpad.c
+++ b/drivers/input/joystick/xpad.c
@@ -1437,16 +1437,6 @@ static int xpad_probe(struct usb_interface *intf, const struct usb_device_id *id
 			break;
 	}
 
-	if (xpad_device[i].xtype == XTYPE_XBOXONE &&
-	    intf->cur_altsetting->desc.bInterfaceNumber != 0) {
-		/*
-		 * The Xbox One controller lists three interfaces all with the
-		 * same interface class, subclass and protocol. Differentiate by
-		 * interface number.
-		 */
-		return -ENODEV;
-	}
-
 	xpad = kzalloc(sizeof(struct usb_xpad), GFP_KERNEL);
 	if (!xpad)
 		return -ENOMEM;
@@ -1478,6 +1468,8 @@ static int xpad_probe(struct usb_interface *intf, const struct usb_device_id *id
 		if (intf->cur_altsetting->desc.bInterfaceClass == USB_CLASS_VENDOR_SPEC) {
 			if (intf->cur_altsetting->desc.bInterfaceProtocol == 129)
 				xpad->xtype = XTYPE_XBOX360W;
+			else if (intf->cur_altsetting->desc.bInterfaceProtocol == 208)
+				xpad->xtype = XTYPE_XBOXONE;
 			else
 				xpad->xtype = XTYPE_XBOX360;
 		} else {
@@ -1492,6 +1484,17 @@ static int xpad_probe(struct usb_interface *intf, const struct usb_device_id *id
 			xpad->mapping |= MAP_STICKS_TO_NULL;
 	}
 
+	if (xpad->xtype == XTYPE_XBOXONE &&
+	    intf->cur_altsetting->desc.bInterfaceNumber != 0) {
+		/*
+		 * The Xbox One controller lists three interfaces all with the
+		 * same interface class, subclass and protocol. Differentiate by
+		 * interface number.
+		 */
+		error = -ENODEV;
+		goto err_free_in_urb;
+	}
+
 	error = xpad_init_output(intf, xpad);
 	if (error)
 		goto err_free_in_urb;
-- 
2.7.4