codecs.c: fix race condition

colesbury · Apr 23, 2023 · 5d006db · 5d006db
1 parent 6540bf3
commit 5d006db
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Showing 3 changed files with 26 additions and 21 deletions.
diff --git a/Include/internal/pycore_ucnhash.h b/Include/internal/pycore_ucnhash.h
@@ -28,6 +28,8 @@ typedef struct {
 
 } _PyUnicode_Name_CAPI;
 
+extern _PyUnicode_Name_CAPI *_PyUnicode_GetNameCAPI(void);
+
 #ifdef __cplusplus
 }
 #endif

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
@@ -5724,6 +5724,22 @@ PyUnicode_AsUTF16String(PyObject *unicode)
  return _PyUnicode_EncodeUTF16(unicode, NULL, 0);
 }
 
+_PyUnicode_Name_CAPI *_PyUnicode_GetNameCAPI(void)
+{
+ PyInterpreterState *interp = _PyInterpreterState_Get();
+ _PyUnicode_Name_CAPI *ucnhash_capi;
+
+ ucnhash_capi = _Py_atomic_load_ptr(&interp->unicode.ucnhash_capi);
+ if (ucnhash_capi == NULL) {
+ ucnhash_capi = (_PyUnicode_Name_CAPI *)PyCapsule_Import(
+ PyUnicodeData_CAPSULE_NAME, 1);
+
+ // It's fine if we overwite the value here. It's always the same value.
+ _Py_atomic_store_ptr(&interp->unicode.ucnhash_capi, ucnhash_capi);
+ }
+ return ucnhash_capi;
+}
+
 /* --- Unicode Escape Codec ----------------------------------------------- */
 
 PyObject *
@@ -5739,7 +5755,6 @@ _PyUnicode_DecodeUnicodeEscapeInternal(const char *s,
  PyObject *errorHandler = NULL;
  PyObject *exc = NULL;
  _PyUnicode_Name_CAPI *ucnhash_capi;
- PyInterpreterState *interp = _PyInterpreterState_Get();
 
  // so we can remember if we've seen an invalid escape char or not
  *first_invalid_escape = NULL;
@@ -5887,19 +5902,13 @@ _PyUnicode_DecodeUnicodeEscapeInternal(const char *s,
 
  /* \N{name} */
  case 'N':
- ucnhash_capi = interp->unicode.ucnhash_capi;
+ ucnhash_capi = _PyUnicode_GetNameCAPI();
  if (ucnhash_capi == NULL) {
- /* load the unicode data module */
- ucnhash_capi = (_PyUnicode_Name_CAPI *)PyCapsule_Import(
- PyUnicodeData_CAPSULE_NAME, 1);
- if (ucnhash_capi == NULL) {
- PyErr_SetString(
- PyExc_UnicodeError,
- "\\N escapes not supported (can't load unicodedata module)"
- );
- goto onError;
- }
- interp->unicode.ucnhash_capi = ucnhash_capi;
+ PyErr_SetString(
+ PyExc_UnicodeError,
+ "\\N escapes not supported (can't load unicodedata module)"
+ );
+ return NULL;
  }
 
  message = "malformed \\N character escape";

diff --git a/Python/codecs.c b/Python/codecs.c
@@ -949,8 +949,6 @@ PyObject *PyCodec_BackslashReplaceErrors(PyObject *exc)
  return Py_BuildValue("(Nn)", res, end);
 }
 
-static _PyUnicode_Name_CAPI *ucnhash_capi = NULL;
-
 PyObject *PyCodec_NameReplaceErrors(PyObject *exc)
 {
  if (PyObject_TypeCheck(exc, (PyTypeObject *)PyExc_UnicodeEncodeError)) {
@@ -971,13 +969,9 @@ PyObject *PyCodec_NameReplaceErrors(PyObject *exc)
  return NULL;
  if (!(object = PyUnicodeEncodeError_GetObject(exc)))
  return NULL;
+ _PyUnicode_Name_CAPI *ucnhash_capi = _PyUnicode_GetNameCAPI();
  if (!ucnhash_capi) {
- /* load the unicode data module */
- ucnhash_capi = (_PyUnicode_Name_CAPI *)PyCapsule_Import(
- PyUnicodeData_CAPSULE_NAME, 1);
- if (!ucnhash_capi) {
- return NULL;
- }
+ return NULL;
  }
  for (i = start, ressize = 0; i < end; ++i) {
  /* object is guaranteed to be "ready" */