audit service: Explicitly call auditctl to disable everything

Otherwise, journald might be starting auditing.
Some reading:
    - https://fedorahosted.org/fesco/ticket/1311
    - https://github.com/systemd/systemd/issues/959
    - 64f83d3087

nixos/modules/security/audit.nix

@@ -4,6 +4,7 @@ with lib;
 
 let
   cfg = config.security.audit;
+  enabled = cfg.enable == "lock" || cfg.enable;
 
   failureModes = {
     silent = 0;
@@ -11,6 +12,13 @@ let
     panic  = 2;
   };
 
+  disableScript = pkgs.writeScript "audit-disable" ''
+    #!${pkgs.stdenv.shell} -eu
+    # Explicitly disable everything, as otherwise journald might start it.
+    auditctl -D
+    auditctl -e 0 -a task,never
+  '';
+
   # TODO: it seems like people like their rules to be somewhat secret, yet they will not be if
   # put in the store like this. At the same time, it doesn't feel like a huge deal and working
   # around that is a pain so I'm leaving it like this for now.
@@ -91,7 +99,7 @@ in {
     };
   };
 
-  config = mkIf (cfg.enable == "lock" || cfg.enable) {
+  config = {
     systemd.services.audit = {
       description = "Kernel Auditing";
       wantedBy = [ "basic.target" ];
@@ -103,8 +111,8 @@ in {
       serviceConfig = {
         Type = "oneshot";
         RemainAfterExit = true;
-        ExecStart = "@${startScript} audit-start";
-        ExecStop  = "@${stopScript}  audit-stop";
+        ExecStart = "@${if enabled then startScript else disableScript} audit-start";
+        ExecStop  = "@${stopScript} audit-stop";
       };
     };
   };