[cylemons]

In the manpage for vfork, Linux in particular

> As with fork(2), the child process created by vfork() inherits copies of various of the caller's process attributes (e.g., file descriptors, signal dispositions, and current working directory); the vfork() call differs only in the treatment of the virtual address space, as described above.

so it seems Linux does define the behavior of vfork, but if you rely on it, your code won't be portable to other POSIX systems

https://man7.org/linux/man-pages/man2/vfork.2.html