Input: gtco - fix crash on detecting device without endpoints

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>

diff --git a/drivers/input/tablet/gtco.c b/drivers/input/tablet/gtco.c
index 8ea6afe..929215a 100644 (file)
--- a/drivers/input/tablet/gtco.c
+++ b/drivers/input/tablet/gtco.c
@@ -866,6 +866,14 @@ 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
@@ -887,7 +895,7 @@ 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) {
                err("Can't retrieve exta USB descriptor to get hid report descriptor length");
                error = -EIO;
                goto err_free_urb;