if (!capable(CAP_SYS_ADMIN))
return -EPERM;
+ /* The block layer will pass back some non-nbd ioctls in case we have
+ * special handling for them, but we don't so just return an error.
+ */
+ if (_IOC_TYPE(cmd) != 0xab)
+ return -EINVAL;
+
mutex_lock(&nbd->config_lock);
/* Don't allow ioctl operations on a nbd device that was created with