How could be a programmer, who has enough patience to read documents and has knowledge to implement the Windows kernel driver which does, 1. offer IOCTL serivc

How could be a programmer, who has enough patience to read documents and has knowledge to implement the Windows kernel driver which does, 1. offer IOCTL serivce 2. disable SMEP 3. execute user-space code from kernel. , NOT notice the very program he is writing has serious security vulnerability? How could he not notice and saying "Wait, Am I writing rootkit?"