The original justification for cap_task_kill() was as follows:

	check_kill_permission() does appropriate uid equivalence checks.
	However with file capabilities it becomes possible for an
	unprivileged user to execute a file with file capabilities
	resulting in a more privileged task with the same uid.

However now that cap_task_kill() always returns 0 (permission
granted) when p->uid==current->uid, the whole hook is worthless,
and only likely to create more subtle problems in the corner cases
where it might still be called but return -EPERM.  Those cases
are basically when uids are different but euid/suid is equivalent
as per the check in check_kill_permission().

One example of a still-broken application is 'at' for non-root users.

This patch removes cap_task_kill().
Signed-off-by: NSerge Hallyn <serge@hallyn.com>
Acked-by: NAndrew G. Morgan <morgan@kernel.org>
Earlier-version-tested-by: NLuiz Fernando N. Capitulino <lcapitulino@mandriva.com.br>
Acked-by: NCasey Schaufler <casey@schaufler-ca.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>