gh-129983: fix data race in compile_template in sre.c

Lib/test/libregrtest/tsan.py

@@ -34,6 +34,7 @@
 TSAN_PARALLEL_TESTS = [
     'test_abc',
     'test_hashlib',
+    'test_re',
 ]
 
 

Lib/test/test_re.py

@@ -1,3 +1,4 @@
+from test import support
 from test.support import (gc_collect, bigmemtest, _2G,
                           cpython_only, captured_stdout,
                           check_disallow_instantiation, is_emscripten, is_wasi,
@@ -33,6 +34,7 @@ class B(bytes):
     def __getitem__(self, index):
         return B(super().__getitem__(index))
 
+@support.skip_if_sanitizer("not everything here is free-threading safe yet", thread=True)
 class ReTests(unittest.TestCase):
 
     def assertTypedEqual(self, actual, expect, msg=None):
@@ -2714,6 +2716,7 @@ def get_debug_out(pat):
     return out.getvalue()
 
 
+@support.skip_if_sanitizer("not everything here is free-threading safe yet", thread=True)
 @cpython_only
 class DebugTests(unittest.TestCase):
     maxDiff = None
@@ -2810,6 +2813,7 @@ def test_possesive_repeat(self):
 ''')
 
 
+@support.skip_if_sanitizer("not everything here is free-threading safe yet", thread=True)
 class PatternReprTests(unittest.TestCase):
     def check(self, pattern, expected):
         self.assertEqual(repr(re.compile(pattern)), expected)
@@ -2890,6 +2894,7 @@ def test_flags_repr(self):
                          "re.ASCII|re.LOCALE|re.UNICODE|re.MULTILINE|re.DEBUG|0xffe01")
 
 
+@support.skip_if_sanitizer("not everything here is free-threading safe yet", thread=True)
 class ImplementationTest(unittest.TestCase):
     """
     Test implementation details of the re module.
@@ -3027,6 +3032,7 @@ def test_sre_template_invalid_group_index(self):
         self.assertIn("an integer is required", str(cm.exception))
 
 
+@support.skip_if_sanitizer("not everything here is free-threading safe yet", thread=True)
 class ExternalTests(unittest.TestCase):
 
     def test_re_benchmarks(self):
@@ -3140,5 +3146,12 @@ def test_re_tests(self):
                     self.assertTrue(obj.search(s))
 
 
+@unittest.skipUnless(support.check_sanitizer(thread=True), 'only has meaning if TSAN enabled')
+class FreeThreadingTests(unittest.TestCase):
+    def test_compile_pattern(self):
+        # gh-129983: Data race in compile_template in sre.c
+        re.sub(r"(\d+)", r"\1kg", "Weight: 50")
+
+
 if __name__ == "__main__":
     unittest.main()

Misc/NEWS.d/next/Core_and_Builtins/2025-02-11-20-38-37.gh-issue-129983._1Fujo.rst

@@ -0,0 +1 @@
+Fix data race in compile_template in :file:`sre.c`.

Modules/_sre/sre.c

@@ -1167,13 +1167,21 @@ compile_template(_sremodulestate *module_state,
                  PatternObject *pattern, PyObject *template)
 {
     /* delegate to Python code */
-    PyObject *func = module_state->compile_template;
+    PyObject *func = FT_ATOMIC_LOAD_PTR_RELAXED(module_state->compile_template);
     if (func == NULL) {
         func = PyImport_ImportModuleAttrString("re", "_compile_template");
         if (func == NULL) {
             return NULL;
         }
+#ifdef Py_GIL_DISABLED
+        PyObject *other_func = NULL;
+        if (!_Py_atomic_compare_exchange_ptr(&module_state->compile_template, &other_func, func))  {
+            Py_DECREF(func);
+            func = other_func;
+        }
+#else
         Py_XSETREF(module_state->compile_template, func);
+#endif
     }
 
     PyObject *args[] = {(PyObject *)pattern, template};