Re: *at syscalls for xattrs?

[Jeff Garzik]

H. Peter Anvin wrote:
> Jeff Garzik wrote:
> > > What the *at() interfaces really do is fix/paper over a longstanding
> > > wart in Unix: the cwd really should have been a standard file descriptor
> > > (like stdin/stdout/stderr) instead of a magic piece of state maintained
> > > in kernel space.
> > It's more than a wart, IMO.  *at() allows one to close races (with
> > potential security implications) that are otherwise impossible to close,
> > in directory traversal.
> >
> > *at() permits a userspace program to hold proper references to all
> > objects during a directory traversal, with all that implies.
>
> Well, as Jeremy pointed out, in the absence of threads you can do the
> same thing with fchdir(), however, that's much more of a hack.

My posixutils project (coreutils replacement) used fchdir(2), but that 
still doesn't get you 100% race-free.  It gets you close, yes.

	Jeff



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