[PATCH] fix sched_setscheduler semantics

Currently, a negative policy argument passed into the
'sys_sched_setscheduler()' system call, will return with success.  However,
the manpage for 'sys_sched_setscheduler' says:

EINVAL The scheduling policy is not one of the recognized policies, or the
              parameter p does not make sense for the policy.
Signed-off-by: NJason Baron <jbaron@redhat.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

kernel/sched.c

@@ -3850,6 +3850,10 @@ do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
 asmlinkage long sys_sched_setscheduler(pid_t pid, int policy,
 				       struct sched_param __user *param)
 {
+	/* negative values for policy are not valid */
+	if (policy < 0)
+		return -EINVAL;
+
 	return do_sched_setscheduler(pid, policy, param);
 }