fix: resolve resource leaks and improve namespace lifecycle management

- Fix DNS resolver leaks by creating temporary resolv.conf files within the profile's runtime directory and ensuring robust cleanup.
- Fix isolation block directory leaks by explicitly removing the block directory during namespace unpinning.
- Improve namespace lifecycle management:
    - Register processes before joining an active namespace to prevent race conditions in reference counting.
    - Update `IsLastProcess` and corresponding tests to reflect the unregister-then-check cleanup flow.
- Improve test reliability and correctness:
    - Convert `TestAppRun_ProfileDirInjection` to use separate binary execution, preventing process replacement and ensuring `t.TempDir()` cleanup.
    - Replace hardcoded test configuration paths with `t.TempDir()` in `mount_leak_test.go`.
    - Implement `SetEnvOverrides` helper for cleaner environment variable management in E2E tests.
    - Improve E2E lifecycle tests with better environment handling and output redirection.

1 files changed, 28 insertions, 1 deletions

diff --git a/internal/namespace/pinning.go b/internal/namespace/pinning.go
index 07f15f8..9bf4fee 100644
--- a/internal/namespace/pinning.go
+++ b/internal/namespace/pinning.go
@@ -12,6 +12,24 @@ import (
 	"golang.org/x/sys/unix"
 )
 
+// blockPaths defines the host services that are bind-mounted over to block access
+// from within the isolated namespace.
+var blockPaths = []string{
+	"/run/dbus/system_bus_socket",
+	"/run/systemd/resolve/io.systemd.Resolve",
+	"/run/systemd/resolve/io.systemd.Resolve.Monitor",
+	"/run/nscd/socket",
+	"/var/run/dbus/system_bus_socket",
+	"/var/run/systemd/resolve/io.systemd.Resolve",
+	"/var/run/systemd/resolve/io.systemd.Resolve.Monitor",
+	"/var/run/nscd/socket",
+}
+
+// GetBlockPaths returns the list of paths blocked for namespace isolation.
+func GetBlockPaths() []string {
+	return blockPaths
+}
+
 // PinNamespace binds the current network namespace to the profile's namespace path.
 // This prevents the kernel from destroying the namespace when all processes exit.
 func PinNamespace(pm *paths.PathManager, profile string) error {
@@ -44,7 +62,6 @@ func UnpinNamespace(pm *paths.PathManager, profile string) error {
 	}
 
 	// 1. Unmount the namespace first.
-	// If this is the last reference to the namespace, the kernel will destroy it.
 	if err := unix.Unmount(nsPath, 0); err != nil {
 		return fmt.Errorf("failed to unmount namespace %s: %w", nsPath, err)
 	}
@@ -54,6 +71,16 @@ func UnpinNamespace(pm *paths.PathManager, profile string) error {
 		return fmt.Errorf("failed to remove pin file %s: %w", nsPath, err)
 	}
 
+	// 3. Unmount and clean up blocking services.
+	// Since the block files are located within the profile directory, 
+	// we must unmount them before we can remove the directory.
+	for _, p := range GetBlockPaths() {
+		_ = unix.Unmount(p, unix.MNT_DETACH)
+	}
+
+	blockDir := filepath.Join(pm.RuntimeBaseDir(), "profiles", profile, "block")
+	_ = os.RemoveAll(blockDir)
+
 	pidsDir := GetPidsDirPath(pm, profile)
 
 	// Try to remove pids directory and empty parent directories