[PATCH v2] HID: roccat: add bounds checking in kone_sysfs_write_settings()

[Dan Carpenter <dan.carpenter@oracle.com>]

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 <dan.carpenter@oracle.com>
---
v2:  In the v1 patch I added a check against settings->size but that's
potentially too strict so it was removed.

 drivers/hid/hid-roccat-kone.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/drivers/hid/hid-roccat-kone.c b/drivers/hid/hid-roccat-kone.c
index 2ff4c8e366ff..1ca64481145e 100644
--- a/drivers/hid/hid-roccat-kone.c
+++ b/drivers/hid/hid-roccat-kone.c
@@ -294,31 +294,40 @@ static ssize_t kone_sysfs_write_settings(struct file *fp, struct kobject *kobj,
 	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);
 }
 static BIN_ATTR(settings, 0660, kone_sysfs_read_settings,
-- 
2.28.0