Guard JavaCoordinator JAR scan against symlink cycles

Author: jason810496

task-sdk/src/airflow/sdk/coordinators/java/coordinator.py

@@ -26,6 +26,7 @@
 import selectors
 import signal
 import socket
+import stat
 import subprocess
 import time
 import zipfile
@@ -62,10 +63,36 @@ def _start_server() -> socket.socket:
 
 
 def _find_jars(items: Iterable[pathlib.Path]) -> Iterator[pathlib.Path]:
+    """
+    Yield JAR files under *items*, descending into directories.
+
+    A symlink loop or a directory that hardlinks into one of its ancestors
+    would otherwise recurse until the interpreter stack is exhausted, so
+    directories are deduplicated by ``(st_dev, st_ino)`` for the duration
+    of a single scan.
+    """
+    seen_dirs: set[tuple[int, int]] = set()
+    yield from _walk_jars(items, seen_dirs)
+
+
+def _walk_jars(items: Iterable[pathlib.Path], seen_dirs: set[tuple[int, int]]) -> Iterator[pathlib.Path]:
     for item in items:
-        if item.is_dir():
-            yield from _find_jars(item.iterdir())
-        elif item.is_file() and item.suffix == ".jar":
+        try:
+            st = item.stat()
+        except OSError:
+            continue
+        if stat.S_ISDIR(st.st_mode):
+            key = (st.st_dev, st.st_ino)
+            if key in seen_dirs:
+                log.debug("Skipping already-visited directory", path=str(item))
+                continue
+            seen_dirs.add(key)
+            try:
+                children = list(item.iterdir())
+            except OSError:
+                continue
+            yield from _walk_jars(children, seen_dirs)
+        elif stat.S_ISREG(st.st_mode) and item.suffix == ".jar":
             yield item
 
 

task-sdk/tests/task_sdk/coordinators/java/test_coordinator.py

@@ -40,6 +40,7 @@
     _JavaActivitySubprocess,
     _ResourceTracker,
     _start_server,
+    _walk_jars,
 )
 from airflow.sdk.execution_time.coordinator import BaseCoordinator
 from airflow.sdk.execution_time.supervisor import ActivitySubprocess
@@ -214,6 +215,62 @@ def test_find_by_explicit_main_class_not_present_raises(self, tmp_path):
         with pytest.raises(FileNotFoundError, match="com.example.Missing"):
             _JarInfo.find([tmp_path], "com.example.Missing")
 
+    def test_symlink_cycle_does_not_infinite_recurse(self, tmp_path):
+        nested = tmp_path / "inner"
+        nested.mkdir()
+        _make_jar(nested / "app.jar", main_class="com.example.Loop", schema_version="2026-06-16")
+        loop = nested / "loop"
+        try:
+            loop.symlink_to(tmp_path)
+        except (OSError, NotImplementedError):
+            pytest.skip("symlinks not supported on this platform")
+
+        result = _JarInfo.find([tmp_path], "com.example.Loop")
+        assert result == _JarInfo("com.example.Loop", "2026-06-16")
+
+
+class TestWalkJars:
+    def test_skips_directory_whose_key_is_already_in_seen_dirs(self, tmp_path):
+        """A directory whose (st_dev, st_ino) is already in seen_dirs is skipped."""
+        _make_jar(tmp_path / "app.jar", main_class="com.example.Main", schema_version="2026-06-16")
+        st = tmp_path.stat()
+        seen_dirs: set[tuple[int, int]] = {(st.st_dev, st.st_ino)}
+        assert list(_walk_jars([tmp_path], seen_dirs)) == []
+
+    def test_records_visited_directories_in_seen_dirs(self, tmp_path):
+        """Every directory descended into is added to seen_dirs."""
+        sub = tmp_path / "sub"
+        sub.mkdir()
+        _make_jar(sub / "app.jar", main_class="com.example.Main", schema_version="2026-06-16")
+        seen_dirs: set[tuple[int, int]] = set()
+        list(_walk_jars([tmp_path], seen_dirs))
+        assert (tmp_path.stat().st_dev, tmp_path.stat().st_ino) in seen_dirs
+        assert (sub.stat().st_dev, sub.stat().st_ino) in seen_dirs
+
+    def test_symlink_cycle_yields_each_jar_once(self, tmp_path):
+        """A symlink that loops back to an ancestor must not yield the same JAR twice."""
+        nested = tmp_path / "inner"
+        nested.mkdir()
+        jar = _make_jar(nested / "app.jar", main_class="com.example.Loop", schema_version="2026-06-16")
+        loop = nested / "loop"
+        try:
+            loop.symlink_to(tmp_path)
+        except (OSError, NotImplementedError):
+            pytest.skip("symlinks not supported on this platform")
+
+        seen_dirs: set[tuple[int, int]] = set()
+        yielded = list(_walk_jars([tmp_path], seen_dirs))
+        assert [p.resolve() for p in yielded] == [jar.resolve()]
+
+    def test_skip_logged_when_directory_revisited(self, tmp_path):
+        """A revisited directory triggers the 'Skipping already-visited directory' debug log."""
+        sub = tmp_path / "sub"
+        sub.mkdir()
+        seen_dirs: set[tuple[int, int]] = {(sub.stat().st_dev, sub.stat().st_ino)}
+        with patch("airflow.sdk.coordinators.java.coordinator.log") as mock_log:
+            list(_walk_jars([sub], seen_dirs))
+        mock_log.debug.assert_any_call("Skipping already-visited directory", path=str(sub))
+
 
 class TestAcceptConnections:
     def _connect_after_delay(self, addr: tuple[str, int], delay: float = 0.0) -> None: