Fix root dir as an allowed path on linux

filesystemserver/handler/handler.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 )
 
 type FilesystemHandler struct {
@@ -33,7 +34,11 @@ func NewFilesystemHandler(allowedDirs []string) (*FilesystemHandler, error) {
 
 		// Ensure the path ends with a separator to prevent prefix matching issues
 		// For example, /tmp/foo should not match /tmp/foobar
-		normalized = append(normalized, filepath.Clean(abs)+string(filepath.Separator))
+		cleanPath := filepath.Clean(abs)
+		if !strings.HasSuffix(cleanPath, string(filepath.Separator)) {
+			cleanPath = cleanPath + string(filepath.Separator)
+		}
+		normalized = append(normalized, cleanPath)
 	}
 	return &FilesystemHandler{
 		allowedDirs: normalized,

filesystemserver/handler/helper_test.go

@@ -0,0 +1,13 @@
+package handler
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRoot(t *testing.T) {
+	handler, err := NewFilesystemHandler([]string{"/"})
+	assert.NoError(t, err)
+	assert.True(t, handler.isPathInAllowedDirs("/etc/hostname"))
+}