Re: [PATCH v4 09/12] unix-socket: disallow chdir() when creating unix domain sockets

> Junio C Hamano <gitster@pobox.com> writes:
> 
> >> So I dunno. I'd be OK to just rip the feature out in favor of doing
> >> those chdir()s. But that seems like a non-zero amount of work versus
> >> leaving, and the existing code has the benefit that if another caller
> >> shows up, it could benefit from the feature.
> >
> > I am OK to keep the series as-is, and leave it to a possible future
> > work to remove the need for chdir even for long paths and not having
> > to return an error with ENAMETOOLONG; when such an update happens,
> > the "fail if need to chdir" feature this patch is adding will become
> > a no-op.
> 
> For example, as this is UNIX-only codepath, I wonder if something
> like this would be a good way to avoid chdir() that would cause
> trouble.
> 
>     - obtain a fd from socket(2)
>     - check if path is too long to fit in sa->sun_path
>       - if it does, bind(2) the fd to the address
>       - if it does not, fork(2) a child and
>         - in the child, chdir(2) there and use the shortened path
> 	  to bind(2), and exit(3)
>         - the parents just wait(2)s for the child to return. By the
>           time it dies, the fd would be successfully bound to the
> 	  path.
>     - now we have a file descriptor that is bound at that path.