[PATCHESv2] Add vfs_admin vfs module

[Jeremy Allison]

On Tue, Oct 06, 2015 at 08:36:34AM -0700, Jeremy Allison wrote:
> 
> For directories, the only "safe" POSIX way to do this as
> root is :
> 
> a). mkdir(name)
> b). fd = open(name, O_RDONLY);
> c). fstat(fd);
> d). Ensure owner/primary group match current POSIX
> creds.
> e). fchown(fd, newcreds);
> 
> That's not race-free, but at least it can detect
> any races.

Correction ! That should be:

a). mkdir(name)
a1). chdir(name);
b). fd = open(".", O_RDONLY);
c). fstat(fd);
d). Ensure owner/primary group match current POSIX
creds.
e). fchown(fd, newcreds);

This stuff is tricky :-).