> While you're still between fork() and execve()
This is what I'm trying to say: if this fork() and execve() is not your code, but something
from a proprietary plugin for which you have no source, you cannot control it at all. In other
words, you cannot call any function there, including closefrom(). Hence, marking the fd
O_CLOEXEC on open() makes sure that on fork() this fd is closed.