Fix: cgroup2: Check cgroup existence on Load

Signed-off-by: Berbe <4251220+Berbe@users.noreply.github.com>

Author: Berbe

cgroup2/manager.go

@@ -224,6 +224,10 @@ func Load(group string, opts ...InitOpts) (*Manager, error) {
 		return nil, err
 	}
 	path := filepath.Join(c.mountpoint, group)
+	_, err := os.Stat(path)
+	if err != nil {
+		return nil, err
+	}
 	return &Manager{
 		unifiedMountpoint: c.mountpoint,
 		path:              path,

cgroup2/manager_test.go

@@ -19,6 +19,7 @@ package cgroup2
 import (
 	"context"
 	"fmt"
+	"io/fs"
 	"os"
 	"os/exec"
 	"syscall"
@@ -477,3 +478,11 @@ func TestLoadOKWhenExistent(t *testing.T) {
 	_, err = Load(group)
 	require.NoError(t, err)
 }
+
+func TestLoadErrorsWhenNonExistent(t *testing.T) {
+	checkCgroupMode(t)
+	group := "/nonexistent"
+
+	_, err := Load(group)
+	require.ErrorIs(t, err, fs.ErrNotExist)
+}