audit: don't generate audit feature changed log when audit disabled

If audit is disabled,we shouldn't generate the audit log.
Acked-by: NEric Paris <eparis@redhat.com>
Signed-off-by: NGao feng <gaofeng@cn.fujitsu.com>
Signed-off-by: NRichard Guy Briggs <rgb@redhat.com>
Signed-off-by: NEric Paris <eparis@redhat.com>

kernel/audit.c

@@ -680,6 +680,9 @@ static void audit_log_feature_change(int which, u32 old_feature, u32 new_feature
 {
 	struct audit_buffer *ab;
 
+	if (audit_enabled == AUDIT_OFF)
+		return;
+
 	ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_FEATURE_CHANGE);
 	audit_log_format(ab, "feature=%s old=%d new=%d old_lock=%d new_lock=%d res=%d",
 			 audit_feature_names[which], !!old_feature, !!new_feature,