[PATCH] SELinux: retain ptracer SID across fork

This fixes a bug in SELinux to retain the ptracer SID (if any) across fork.
Otherwise, SELinux will always deny attempts by traced children to exec
domain-changing programs even if the policy would have allowed the tracer
to trace the new domains as well.

Signed-off-by: Stephen Smalley <sds@epoch.ncsc.mil>
Signed-off-by: James Morris <jmorris@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>