bug#39236: [musl] coreutils cp mishandles error return from lchmod

[Florian Weimer]

* Rich Felker:

>> Hmm.  The way I read the musl code, the O_PATH descriptor already
>> exists.  At this point, you can just chmod the O_PATH descriptor, and
>> have the kernel report EOPNOTSUPP if the file system does not support
>> that.
>
> Oh, you mean the second one after it's already open? Maybe that's ok.

Yes, that's what I meant.

> I was concerned it might follow the link and chmod the target at that
> point.

In my tests, it works.  I think it's also documented behavior for chown
on these pseudo-files.

I also verified that closing an O_PATH descriptor does not release POSIX
advisory locks for the same file.  But I'm wondering if there's still
something we are missing.

Thanks,
Florian