Input: gtco - fix crash on detecting device without endpoints

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>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/drivers/input/tablet/gtco.c b/drivers/input/tablet/gtco.c
index 3a7f3a4a4396..7c18249d6c8e 100644
--- a/drivers/input/tablet/gtco.c
+++ b/drivers/input/tablet/gtco.c
@@ -858,6 +858,14 @@ 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
@@ -879,7 +887,7 @@ 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;