Re: *at syscalls for xattrs?

Jeff Garzik
2007-07-16T09:52:30Z

H. Peter Anvin wrote:
> Miklos Szeredi wrote:
>> The *at() thing basically gives you the advantages of a CWD without
>> the disadvantages.
>>
>> For example it could be useful to implement the functionality of
>> find(1) as a library interface.
>>
>
> 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.

Jeff