[PATCH 3.2 10/46] Input: gtco - fix crash on detecting device without endpoints

[Ben Hutchings <ben@decadent.org.uk>]

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

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

From: Vladis Dronov <vdronov@redhat.com>

commit 162f98dea487206d9ab79fc12ed64700667a894d upstream.

The gtco driver expects at least one valid endpoint. If given malicious
descriptors that specify 0 for the number of endpoints, it will crash in
the probe function. Ensure there is at least one endpoint on the interface
before using it.

Also let's fix a minor coding style issue.

The full correct report of this issue can be found in the public
Red Hat Bugzilla:

https://bugzilla.redhat.com/show_bug.cgi?id=1283385

Reported-by: Ralf Spenneberg <ralf@spenneberg.net>
Signed-off-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/input/tablet/gtco.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/drivers/input/tablet/gtco.c
+++ b/drivers/input/tablet/gtco.c
@@ -866,6 +866,14 @@ static int gtco_probe(struct usb_interfa
 		goto err_free_buf;
 	}
 
+	/* Sanity check that a device has an endpoint */
+	if (usbinterface->altsetting[0].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
@@ -887,7 +895,7 @@ static int gtco_probe(struct usb_interfa
 	 * HID report descriptor
 	 */
 	if (usb_get_extra_descriptor(usbinterface->cur_altsetting,
-				     HID_DEVICE_TYPE, &hid_desc) != 0){
+				     HID_DEVICE_TYPE, &hid_desc) != 0) {
 		err("Can't retrieve exta USB descriptor to get hid report descriptor length");
 		error = -EIO;
 		goto err_free_urb;