HID: roccat: add bounds checking in kone_sysfs_write_settings()

This code doesn't check if "settings->startup_profile" is within bounds
and that could result in an out of bounds array access. What the code
does do is it checks if the settings can be written to the firmware, so
it's possible that the firmware has a bounds check? It's safer and
easier to verify when the bounds checking is done in the kernel.

Fixes: 14bf62cde794 ("HID: add driver for Roccat Kone gaming mouse")
Signed-off-by: Dan Carpenter <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

drivers/hid/hid-roccat-kone.c

···
 	struct kone_device *kone = hid_get_drvdata(dev_get_drvdata(dev));
 	struct usb_device *usb_dev = interface_to_usbdev(to_usb_interface(dev));
 	int retval = 0, difference, old_profile;
+	struct kone_settings *settings = (struct kone_settings *)buf;
 
 	/* I need to get my data in one piece */
 	if (off != 0 || count != sizeof(struct kone_settings))
 		return -EINVAL;
 
 	mutex_lock(&kone->kone_lock);
-	difference = memcmp(buf, &kone->settings, sizeof(struct kone_settings));
+	difference = memcmp(settings, &kone->settings,
+			    sizeof(struct kone_settings));
 	if (difference) {
-		retval = kone_set_settings(usb_dev,
-				(struct kone_settings const *)buf);
-		if (retval) {
-			mutex_unlock(&kone->kone_lock);
-			return retval;
+		if (settings->startup_profile < 1 ||
+		    settings->startup_profile > 5) {
+			retval = -EINVAL;
+			goto unlock;
 		}
 
+		retval = kone_set_settings(usb_dev, settings);
+		if (retval)
+			goto unlock;
+
 		old_profile = kone->settings.startup_profile;
-		memcpy(&kone->settings, buf, sizeof(struct kone_settings));
+		memcpy(&kone->settings, settings, sizeof(struct kone_settings));
 
 		kone_profile_activated(kone, kone->settings.startup_profile);
 
 		if (kone->settings.startup_profile != old_profile)
 			kone_profile_report(kone, kone->settings.startup_profile);
 	}
+unlock:
 	mutex_unlock(&kone->kone_lock);
+
+	if (retval)
+		return retval;
 
 	return sizeof(struct kone_settings);
 }