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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