lsm: add a LSM_STARTED_ALL notification event

Add a new LSM notifier event, LSM_STARTED_ALL, which is fired once at
boot when all of the LSMs have been started.

Reviewed-by: Kees Cook <kees@kernel.org>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: John Johansen <john.johhansen@canonical.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

include/linux/security.h

@@ -85,6 +85,7 @@ struct timezone;
 
 enum lsm_event {
 	LSM_POLICY_CHANGE,
+	LSM_STARTED_ALL,
 };
 
 struct dm_verity_digest {

security/lsm_init.c

@@ -556,6 +556,7 @@ static int __init security_initcall_late(void)
 
 	rc = lsm_initcall(late);
 	lsm_pr_dbg("all enabled LSMs fully activated\n");
+	call_blocking_lsm_notifier(LSM_STARTED_ALL, NULL);
 
 	return rc;
 }