libct/cg: add test for remove a non-exist dir in a ro mount point

Signed-off-by: lfbzhm <lifubang@acmcoder.com>

libcontainer/cgroups/utils_test.go

@@ -3,11 +3,14 @@ package cgroups
 import (
 	"bytes"
 	"errors"
+	"os"
+	"path/filepath"
 	"reflect"
 	"strings"
 	"testing"
 
 	"github.com/moby/sys/mountinfo"
+	"golang.org/x/sys/unix"
 )
 
 const fedoraMountinfo = `15 35 0:3 / /proc rw,nosuid,nodev,noexec,relatime shared:5 - proc proc rw
@@ -661,3 +664,42 @@ func TestConvertBlkIOToIOWeightValue(t *testing.T) {
 		}
 	}
 }
+
+// TestRemovePathEROFS is to test remove a non-exist dir in a ro mount point.
+// The similar issue example: https://github.com/opencontainers/runc/issues/4518
+func TestRemovePathEROFS(t *testing.T) {
+	dirFrom, err := os.MkdirTemp(".", "from-")
+	if err != nil {
+		t.Skip("can't create a tmp dir")
+	}
+	defer func() {
+		_ = unix.Rmdir(dirFrom)
+	}()
+	dirTo, err := os.MkdirTemp(".", "to-")
+	if err != nil {
+		t.Skip("can't create a tmp dir")
+	}
+	defer func() {
+		_ = unix.Rmdir(dirTo)
+	}()
+	err = unix.Mount(dirFrom, dirTo, "", unix.MS_BIND, "")
+	if err != nil {
+		t.Skip("no permission of mount")
+	}
+	err = unix.Mount("", dirTo, "", unix.MS_REMOUNT|unix.MS_BIND|unix.MS_RDONLY, "")
+	if err != nil {
+		t.Skip("no permission of mount")
+	}
+	defer func() {
+		_ = unix.Unmount(dirTo, 0)
+	}()
+	nonExistDir := filepath.Join(dirTo, "nothing")
+	err = rmdir(nonExistDir, true)
+	if !errors.Is(err, unix.EROFS) {
+		t.Fatalf("expected the error of removing a non-exist dir %s in a ro mount point with rmdir to be unix.EROFS, but got %v", nonExistDir, err)
+	}
+	err = RemovePath(nonExistDir)
+	if err != nil {
+		t.Fatalf("expected the error of removing a non-exist dir %s in a ro mount point with RemovePath to be nil, but got %v", nonExistDir, err)
+	}
+}