init: Detach daemon only after sepolicy is loaded

The new sequence of operation would be:

1: Load sepolicy - Daemon will continue to be alive and serve any I/O request

2: After sepolicy loading is complete - Switch the device-mapper tables.

3: Kill the block device daemon launched in the first-stage init.

4: Re-launch the daemon with the correct selinux labels set.

5: Enforce the sepolicy

Bug: 240321741
Test: Full OTA on pixel
Signed-off-by: Akilesh Kailash <akailash@google.com>
Change-Id: Idd392f0f0aae7d93e546c0ec0762e6c07b6263e4
diff --git a/init/snapuserd_transition.cpp b/init/snapuserd_transition.cpp
index 5c821b0..6972f30 100644
--- a/init/snapuserd_transition.cpp
+++ b/init/snapuserd_transition.cpp
@@ -226,12 +226,9 @@
 
     argv_.emplace_back("snapuserd");
     argv_.emplace_back("-no_socket");
-    if (!sm_->DetachSnapuserdForSelinux(&argv_)) {
+    if (!sm_->PrepareSnapuserdArgsForSelinux(&argv_)) {
         LOG(FATAL) << "Could not perform selinux transition";
     }
-
-    // Make sure the process is gone so we don't have any selinux audits.
-    KillFirstStageSnapuserd(old_pid_);
 }
 
 void SnapuserdSelinuxHelper::FinishTransition() {
@@ -301,6 +298,12 @@
 }
 
 void SnapuserdSelinuxHelper::RelaunchFirstStageSnapuserd() {
+    if (!sm_->DetachFirstStageSnapuserdForSelinux()) {
+        LOG(FATAL) << "Could not perform selinux transition";
+    }
+
+    KillFirstStageSnapuserd(old_pid_);
+
     auto fd = GetRamdiskSnapuserdFd();
     if (!fd) {
         LOG(FATAL) << "Environment variable " << kSnapuserdFirstStageFdVar << " was not set!";