Merge pull request #1001 from xabrouck/oldkernel

Making cred optional as it didn't exist in old 2.6 kernels

Author: ikelos

volatility3/framework/symbols/linux/__init__.py

@@ -28,7 +28,7 @@ def __init__(self, *args, **kwargs) -> None:
         self.set_type_class("fs_struct", extensions.fs_struct)
         self.set_type_class("files_struct", extensions.files_struct)
         self.set_type_class("kobject", extensions.kobject)
-        self.set_type_class("cred", extensions.cred)
+        self.optional_set_type_class("cred", extensions.cred)
         self.set_type_class("kernel_cap_struct", extensions.kernel_cap_struct)
         # Might not exist in the current symbols
         self.optional_set_type_class("module", extensions.module)