[PATCH 3.16 173/245] Input: gtco - fix endpoint sanity check

[Ben Hutchings]

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

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

From: Johan Hovold <johan@xxxxxxxxxx>

commit a8eeb74df5a6bdb214b2b581b14782c5f5a0cf83 upstream.

The driver was checking the number of endpoints of the first alternate
setting instead of the current one, something which could lead to the
driver 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: 162f98dea487 ("Input: gtco - fix crash on detecting device without endpoints")
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Acked-by: Vladis Dronov <vdronov@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20191210113737.4016-5-johan@xxxxxxxxxx
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/input/tablet/gtco.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

--- a/drivers/input/tablet/gtco.c
+++ b/drivers/input/tablet/gtco.c
@@ -886,18 +886,14 @@ static int gtco_probe(struct usb_interfa
 	}
 
 	/* Sanity check that a device has an endpoint */
-	if (usbinterface->altsetting[0].desc.bNumEndpoints < 1) {
+	if (usbinterface->cur_altsetting->desc.bNumEndpoints < 1) {
 		dev_err(&usbinterface->dev,
 			"Invalid number of endpoints\n");
 		error = -EINVAL;
 		goto err_free_urb;
 	}
 
-	/*
-	 * The endpoint is always altsetting 0, we know this since we know
-	 * this device only has one interrupt endpoint
-	 */
-	endpoint = &usbinterface->altsetting[0].endpoint[0].desc;
+	endpoint = &usbinterface->cur_altsetting->endpoint[0].desc;
 
 	/* Some debug */
 	dev_dbg(&usbinterface->dev, "gtco # interfaces: %d\n", usbinterface->num_altsetting);
@@ -984,7 +980,7 @@ static int gtco_probe(struct usb_interfa
 	input_dev->dev.parent = &usbinterface->dev;
 
 	/* Setup the URB, it will be posted later on open of input device */
-	endpoint = &usbinterface->altsetting[0].endpoint[0].desc;
+	endpoint = &usbinterface->cur_altsetting->endpoint[0].desc;
 
 	usb_fill_int_urb(gtco->urbinfo,
 			 gtco->usbdev,