[PATCH 2/2][Trusty, Utopic, Vivid, Wily, Xenial] Input: gtco - fix crash on detecting device without endpoints

[Luis Henriques]

From: Vladis Dronov <vdronov at redhat.com>

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 at spenneberg.net>
Signed-off-by: Vladis Dronov <vdronov at redhat.com>
Cc: stable at vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov at gmail.com>
(cherry picked from commit 162f98dea487206d9ab79fc12ed64700667a894d)
CVE-2016-2187
BugLink: https://bugs.launchpad.net/bugs/1575706
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/input/tablet/gtco.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/input/tablet/gtco.c b/drivers/input/tablet/gtco.c
index 29e01ab6859f..a9f8f925ba2b 100644
--- a/drivers/input/tablet/gtco.c
+++ b/drivers/input/tablet/gtco.c
@@ -869,6 +869,14 @@ static int gtco_probe(struct usb_interface *usbinterface,
 		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
@@ -890,7 +898,7 @@ static int gtco_probe(struct usb_interface *usbinterface,
 	 * HID report descriptor
 	 */
 	if (usb_get_extra_descriptor(usbinterface->cur_altsetting,
-				     HID_DEVICE_TYPE, &hid_desc) != 0){
+				     HID_DEVICE_TYPE, &hid_desc) != 0) {
 		dev_err(&usbinterface->dev,
 			"Can't retrieve exta USB descriptor to get hid report descriptor length\n");
 		error = -EIO;