19774 FIX Handle corrupted data files gracefully instead of crashing

Crash-Group-ID: 3380
Jira: CMK-33559
Change-Id: I29da9ff5b73abd64b0e70fc3e5cf6744267449e6

Author: otAAAh

.werks/19774.md

@@ -0,0 +1,21 @@
+[//]: # (werk v3)
+# Handle corrupted data files gracefully instead of crashing
+
+key        | value
+---------- | ---
+date       | 2026-04-14T13:00:00+00:00
+version    | 2.5.0b5
+class      | fix
+edition    | community
+component  | core
+level      | 1
+compatible | yes
+
+When a Checkmk data file (`.mk` file) became corrupted (e.g., filled with null
+bytes due to a filesystem issue), loading it would crash with a `SyntaxError:
+source code string cannot contain null bytes`. This was most commonly observed
+on the notification analysis page when the notification backlog file was
+corrupted.
+
+Checkmk now gracefully falls back to the default value when a data file cannot
+be deserialized, and logs a warning.

packages/cmk-ccc/cmk/ccc/store/__init__.py

@@ -192,7 +192,11 @@ def load_object_from_file(path: Path, *, default: Any, lock: bool = False) -> An
         tracer.simple_span("load_object_from_file", path),
         _leave_locked_unless_exception(path) if lock else nullcontext(),
     ):
-        return ObjectStore(path, serializer=DimSerializer()).read_obj(default=default)
+        try:
+            return ObjectStore(path, serializer=DimSerializer()).read_obj(default=default)
+        except (SyntaxError, ValueError):
+            logger.warning("Failed to deserialize %s, returning default", path)
+            return default
 
 
 def load_object_from_pickle_file(path: Path, *, default: Any, lock: bool = False) -> Any:

packages/cmk-ccc/tests/test_store.py

@@ -212,7 +212,6 @@ def test_save_text_to_file(tmp_path: Path, data: str) -> None:
     assert store.load_text_from_file(path) == data
 
 
-@pytest.mark.xfail(strict=True, reason="Crash group 3380: SyntaxError on null bytes in file")
 def test_load_object_from_file_null_bytes(tmp_path: Path) -> None:
     """A file containing null bytes should return default, not crash with SyntaxError."""
     path = tmp_path / "corrupted.mk"