"Race condition in the setsid function in Linux before 126.96.36.199 allows
local users to cause a denial of service (crash) and possibly access
portions of kernel memory, related to TTY changes, locking, and
We originally believed this issue did not affect 2.4 kernels, however
this appears to be incorrect.
See bug #149591 for backported patch
Actually, Alan said "In the 2.4 case your controlling tty is
private not thread group so a setsid() can't race because you can't
setsid in the same thread as is opening current->tty."