bug#25342: GNU coreutils: race condition in "ln -f source dest"

[Paul Eggert]

Mirsad Goran Todorovac wrote:
> It would suffice that:
> linkat (AT_CWDFD, source, AT_CWDFD, dest, 0) == 0 || unlink (dest) == 0 && 
> linkat (AT_CWDFD, source, AT_CWDFD, dest, 0) == 0;
> be replaced with:
> linkat (AT_CWDFD, source, AT_CWDFD, dest_tmp, 0) == 0 && renameat (AT_CWDFD, 
> dest_tmp, AT_CWDFD, dest) == 0;

It isn't that simple, since renameat is a no-op if the source and destination 
are already hard links. So the patch you sent in would not work.

Anyway, I'm not disagreeing with the basic idea, I'm merely saying I don't see 
why we should have an option to keep the old behavior. Anybody who really wants 
the old behavior can do 'rm -f new && ln old new' instead.