How to share a writable flock file in /tmp/ between two users?

Question

It seems that Linux has tightened up security in /tmp in later kernels than 3.x and if /tmp has the sticky bit set another user may not modify a 0777 file.

Are there any work arounds for sharing a flock'ed file? (I cannot create the file as root ahead of time, which apparently would work since root owns /tmp)

$ ll /tmp/zzz
-rwxrwxrwx 1 games games 1 Aug 23 11:35 /tmp/zzz
$ id
uid=1000(me) gid=1000(me) groups=1000(me)
$ /usr/bin/flock /tmp/zzz  ls 
flock: cannot open lock file /tmp/zzz: Permission denied 

Answer 1

One solution is to use a directory instead:

(umask 0222 && mkdir -p /tmp/lock.foo && flock /tmp/.foo /usr/bin/whatever)

The restriction does not appear to apply to directories, and the directory doesn't seem to require to be writable by other users either.