[PATCH 3.16 174/245] Input: sur40 - fix interface sanity checks

[Ben Hutchings]

3.16.83-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Johan Hovold <johan@xxxxxxxxxx>

commit 6b32391ed675827f8425a414abbc6fbd54ea54fe upstream.

Make sure to use the current alternate setting when verifying the
interface descriptors to avoid binding to an invalid interface.

This in turn could cause the driver to misbehave or trigger a WARN() in
usb_submit_urb() that kernels with panic_on_warn set would choke on.

Fixes: bdb5c57f209c ("Input: add sur40 driver for Samsung SUR40 (aka MS Surface 2.0/Pixelsense)")
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Acked-by: Vladis Dronov <vdronov@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20191210113737.4016-8-johan@xxxxxxxxxx
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/input/touchscreen/sur40.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/input/touchscreen/sur40.c
+++ b/drivers/input/touchscreen/sur40.c
@@ -357,7 +357,7 @@ static int sur40_probe(struct usb_interf
 	int error;
 
 	/* Check if we really have the right interface. */
-	iface_desc = &interface->altsetting[0];
+	iface_desc = interface->cur_altsetting;
 	if (iface_desc->desc.bInterfaceClass != 0xFF)
 		return -ENODEV;