Shared file descriptor is closed prematurely

[josephlr]

Here, we create a File from a raw fd. However, as this object is created on the stack, at the endo the function, the file will be dropped, and thus closed.

This means that on systems using a shared FD, the second call to getrandom will fail. This can be fixed by just storing a File instead of a RawFd in static memory.

[newpavlov]

Yes, code should use mem::forget(f), I was doing it, but missed it during review...

You can't store File, as Read impl requires an exclusive access. You could use try_clone, but I think it will be slightly less efficient.