[3.13] gh-128013: fix data race in PyUnicode_AsUTF8AndSize on free-threading (#128021) (#128417)

Author: kumaraditya303

Lib/test/test_capi/test_unicode.py

@@ -1,7 +1,7 @@
 import unittest
 import sys
 from test import support
-from test.support import import_helper
+from test.support import threading_helper, import_helper
 
 try:
     import _testcapi
@@ -959,6 +959,24 @@ def test_asutf8(self):
         self.assertRaises(TypeError, unicode_asutf8, [], 0)
         # CRASHES unicode_asutf8(NULL, 0)
 
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    @threading_helper.requires_working_threading()
+    def test_asutf8_race(self):
+        """Test that there's no race condition in PyUnicode_AsUTF8()"""
+        unicode_asutf8 = _testcapi.unicode_asutf8
+        from threading import Thread
+
+        data = "😊"
+
+        def worker():
+            for _ in range(1000):
+                self.assertEqual(unicode_asutf8(data, 5), b'\xf0\x9f\x98\x8a\0')
+
+        threads = [Thread(target=worker) for _ in range(10)]
+        with threading_helper.start_threads(threads):
+            pass
+
+
     @support.cpython_only
     @unittest.skipIf(_testlimitedcapi is None, 'need _testlimitedcapi module')
     def test_asutf8andsize(self):

Objects/unicodeobject.c

@@ -111,47 +111,80 @@ NOTE: In the interpreter's initialization phase, some globals are currently
 #  define _PyUnicode_CHECK(op) PyUnicode_Check(op)
 #endif
 
-#define _PyUnicode_UTF8(op)                             \
-    (_PyCompactUnicodeObject_CAST(op)->utf8)
-#define PyUnicode_UTF8(op)                              \
-    (assert(_PyUnicode_CHECK(op)),                      \
-     PyUnicode_IS_COMPACT_ASCII(op) ?                   \
-         ((char*)(_PyASCIIObject_CAST(op) + 1)) :       \
-         _PyUnicode_UTF8(op))
-#define _PyUnicode_UTF8_LENGTH(op)                      \
-    (_PyCompactUnicodeObject_CAST(op)->utf8_length)
-#define PyUnicode_UTF8_LENGTH(op)                       \
-    (assert(_PyUnicode_CHECK(op)),                      \
-     PyUnicode_IS_COMPACT_ASCII(op) ?                   \
-         _PyASCIIObject_CAST(op)->length :              \
-         _PyUnicode_UTF8_LENGTH(op))
+static inline char* _PyUnicode_UTF8(PyObject *op)
+{
+    return FT_ATOMIC_LOAD_PTR_ACQUIRE(_PyCompactUnicodeObject_CAST(op)->utf8);
+}
+
+static inline char* PyUnicode_UTF8(PyObject *op)
+{
+    assert(_PyUnicode_CHECK(op));
+    if (PyUnicode_IS_COMPACT_ASCII(op)) {
+        return ((char*)(_PyASCIIObject_CAST(op) + 1));
+    }
+    else {
+         return _PyUnicode_UTF8(op);
+    }
+}
+
+static inline void PyUnicode_SET_UTF8(PyObject *op, char *utf8)
+{
+    FT_ATOMIC_STORE_PTR_RELEASE(_PyCompactUnicodeObject_CAST(op)->utf8, utf8);
+}
+
+static inline Py_ssize_t PyUnicode_UTF8_LENGTH(PyObject *op)
+{
+    assert(_PyUnicode_CHECK(op));
+    if (PyUnicode_IS_COMPACT_ASCII(op)) {
+         return _PyASCIIObject_CAST(op)->length;
+    }
+    else {
+         return _PyCompactUnicodeObject_CAST(op)->utf8_length;
+    }
+}
+
+static inline void PyUnicode_SET_UTF8_LENGTH(PyObject *op, Py_ssize_t length)
+{
+    _PyCompactUnicodeObject_CAST(op)->utf8_length = length;
+}
 
 #define _PyUnicode_LENGTH(op)                           \
     (_PyASCIIObject_CAST(op)->length)
 #define _PyUnicode_STATE(op)                            \
     (_PyASCIIObject_CAST(op)->state)
 #define _PyUnicode_HASH(op)                             \
     (_PyASCIIObject_CAST(op)->hash)
-#define _PyUnicode_KIND(op)                             \
-    (assert(_PyUnicode_CHECK(op)),                      \
-     _PyASCIIObject_CAST(op)->state.kind)
-#define _PyUnicode_GET_LENGTH(op)                       \
-    (assert(_PyUnicode_CHECK(op)),                      \
-     _PyASCIIObject_CAST(op)->length)
+
+static inline Py_hash_t PyUnicode_HASH(PyObject *op)
+{
+    assert(_PyUnicode_CHECK(op));
+    return FT_ATOMIC_LOAD_SSIZE_RELAXED(_PyASCIIObject_CAST(op)->hash);
+}
+
+static inline void PyUnicode_SET_HASH(PyObject *op, Py_hash_t hash)
+{
+    FT_ATOMIC_STORE_SSIZE_RELAXED(_PyASCIIObject_CAST(op)->hash, hash);
+}
+
 #define _PyUnicode_DATA_ANY(op)                         \
     (_PyUnicodeObject_CAST(op)->data.any)
 
-#define _PyUnicode_SHARE_UTF8(op)                       \
-    (assert(_PyUnicode_CHECK(op)),                      \
-     assert(!PyUnicode_IS_COMPACT_ASCII(op)),           \
-     (_PyUnicode_UTF8(op) == PyUnicode_DATA(op)))
+static inline int _PyUnicode_SHARE_UTF8(PyObject *op)
+{
+    assert(_PyUnicode_CHECK(op));
+    assert(!PyUnicode_IS_COMPACT_ASCII(op));
+    return (_PyUnicode_UTF8(op) == PyUnicode_DATA(op));
+}
 
 /* true if the Unicode object has an allocated UTF-8 memory block
    (not shared with other data) */
-#define _PyUnicode_HAS_UTF8_MEMORY(op)                  \
-    ((!PyUnicode_IS_COMPACT_ASCII(op)                   \
-      && _PyUnicode_UTF8(op)                            \
-      && _PyUnicode_UTF8(op) != PyUnicode_DATA(op)))
+static inline int _PyUnicode_HAS_UTF8_MEMORY(PyObject *op)
+{
+    return (!PyUnicode_IS_COMPACT_ASCII(op)
+            && _PyUnicode_UTF8(op) != NULL
+            && _PyUnicode_UTF8(op) != PyUnicode_DATA(op));
+}
+
 
 /* Generic helper macro to convert characters of different types.
    from_type and to_type have to be valid type names, begin and end
@@ -650,7 +683,7 @@ _PyUnicode_CheckConsistency(PyObject *op, int check_content)
                                  || kind == PyUnicode_2BYTE_KIND
                                  || kind == PyUnicode_4BYTE_KIND);
             CHECK(ascii->state.ascii == 0);
-            CHECK(compact->utf8 != data);
+            CHECK(_PyUnicode_UTF8(op) != data);
         }
         else {
             PyUnicodeObject *unicode = _PyUnicodeObject_CAST(op);
@@ -662,16 +695,17 @@ _PyUnicode_CheckConsistency(PyObject *op, int check_content)
             CHECK(ascii->state.compact == 0);
             CHECK(data != NULL);
             if (ascii->state.ascii) {
-                CHECK(compact->utf8 == data);
+                CHECK(_PyUnicode_UTF8(op) == data);
                 CHECK(compact->utf8_length == ascii->length);
             }
             else {
-                CHECK(compact->utf8 != data);
+                CHECK(_PyUnicode_UTF8(op) != data);
             }
         }
-
-        if (compact->utf8 == NULL)
+#ifndef Py_GIL_DISABLED
+        if (_PyUnicode_UTF8(op) == NULL)
             CHECK(compact->utf8_length == 0);
+#endif
     }
 
     /* check that the best kind is used: O(n) operation */
@@ -1115,8 +1149,8 @@ resize_compact(PyObject *unicode, Py_ssize_t length)
 
     if (_PyUnicode_HAS_UTF8_MEMORY(unicode)) {
         PyMem_Free(_PyUnicode_UTF8(unicode));
-        _PyUnicode_UTF8(unicode) = NULL;
-        _PyUnicode_UTF8_LENGTH(unicode) = 0;
+        PyUnicode_SET_UTF8_LENGTH(unicode, 0);
+        PyUnicode_SET_UTF8(unicode, NULL);
     }
 #ifdef Py_TRACE_REFS
     _Py_ForgetReference(unicode);
@@ -1169,8 +1203,8 @@ resize_inplace(PyObject *unicode, Py_ssize_t length)
     if (!share_utf8 && _PyUnicode_HAS_UTF8_MEMORY(unicode))
     {
         PyMem_Free(_PyUnicode_UTF8(unicode));
-        _PyUnicode_UTF8(unicode) = NULL;
-        _PyUnicode_UTF8_LENGTH(unicode) = 0;
+        PyUnicode_SET_UTF8_LENGTH(unicode, 0);
+        PyUnicode_SET_UTF8(unicode, NULL);
     }
 
     data = (PyObject *)PyObject_Realloc(data, new_size);
@@ -1180,8 +1214,8 @@ resize_inplace(PyObject *unicode, Py_ssize_t length)
     }
     _PyUnicode_DATA_ANY(unicode) = data;
     if (share_utf8) {
-        _PyUnicode_UTF8(unicode) = data;
-        _PyUnicode_UTF8_LENGTH(unicode) = length;
+        PyUnicode_SET_UTF8_LENGTH(unicode, length);
+        PyUnicode_SET_UTF8(unicode, data);
     }
     _PyUnicode_LENGTH(unicode) = length;
     PyUnicode_WRITE(PyUnicode_KIND(unicode), data, length, 0);
@@ -1411,12 +1445,12 @@ unicode_convert_wchar_to_ucs4(const wchar_t *begin, const wchar_t *end,
 
     assert(unicode != NULL);
     assert(_PyUnicode_CHECK(unicode));
-    assert(_PyUnicode_KIND(unicode) == PyUnicode_4BYTE_KIND);
+    assert(PyUnicode_KIND(unicode) == PyUnicode_4BYTE_KIND);
     ucs4_out = PyUnicode_4BYTE_DATA(unicode);
 
     for (iter = begin; iter < end; ) {
         assert(ucs4_out < (PyUnicode_4BYTE_DATA(unicode) +
-                           _PyUnicode_GET_LENGTH(unicode)));
+                           PyUnicode_GET_LENGTH(unicode)));
         if (Py_UNICODE_IS_HIGH_SURROGATE(iter[0])
             && (iter+1) < end
             && Py_UNICODE_IS_LOW_SURROGATE(iter[1]))
@@ -1430,7 +1464,7 @@ unicode_convert_wchar_to_ucs4(const wchar_t *begin, const wchar_t *end,
         }
     }
     assert(ucs4_out == (PyUnicode_4BYTE_DATA(unicode) +
-                        _PyUnicode_GET_LENGTH(unicode)));
+                        PyUnicode_GET_LENGTH(unicode)));
 
 }
 #endif
@@ -1801,7 +1835,7 @@ unicode_modifiable(PyObject *unicode)
     assert(_PyUnicode_CHECK(unicode));
     if (Py_REFCNT(unicode) != 1)
         return 0;
-    if (FT_ATOMIC_LOAD_SSIZE_RELAXED(_PyUnicode_HASH(unicode)) != -1)
+    if (PyUnicode_HASH(unicode) != -1)
         return 0;
     if (PyUnicode_CHECK_INTERNED(unicode))
         return 0;
@@ -4052,6 +4086,21 @@ PyUnicode_FSDecoder(PyObject* arg, void* addr)
 
 static int unicode_fill_utf8(PyObject *unicode);
 
+
+static int
+unicode_ensure_utf8(PyObject *unicode)
+{
+    int err = 0;
+    if (PyUnicode_UTF8(unicode) == NULL) {
+        Py_BEGIN_CRITICAL_SECTION(unicode);
+        if (PyUnicode_UTF8(unicode) == NULL) {
+            err = unicode_fill_utf8(unicode);
+        }
+        Py_END_CRITICAL_SECTION();
+    }
+    return err;
+}
+
 const char *
 PyUnicode_AsUTF8AndSize(PyObject *unicode, Py_ssize_t *psize)
 {
@@ -4063,13 +4112,11 @@ PyUnicode_AsUTF8AndSize(PyObject *unicode, Py_ssize_t *psize)
         return NULL;
     }
 
-    if (PyUnicode_UTF8(unicode) == NULL) {
-        if (unicode_fill_utf8(unicode) == -1) {
-            if (psize) {
-                *psize = -1;
-            }
-            return NULL;
+    if (unicode_ensure_utf8(unicode) == -1) {
+        if (psize) {
+            *psize = -1;
         }
+        return NULL;
     }
 
     if (psize) {
@@ -5401,6 +5448,7 @@ unicode_encode_utf8(PyObject *unicode, _Py_error_handler error_handler,
 static int
 unicode_fill_utf8(PyObject *unicode)
 {
+    _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(unicode);
     /* the string cannot be ASCII, or PyUnicode_UTF8() would be set */
     assert(!PyUnicode_IS_ASCII(unicode));
 
@@ -5442,10 +5490,10 @@ unicode_fill_utf8(PyObject *unicode)
         PyErr_NoMemory();
         return -1;
     }
-    _PyUnicode_UTF8(unicode) = cache;
-    _PyUnicode_UTF8_LENGTH(unicode) = len;
     memcpy(cache, start, len);
     cache[len] = '\0';
+    PyUnicode_SET_UTF8_LENGTH(unicode, len);
+    PyUnicode_SET_UTF8(unicode, cache);
     _PyBytesWriter_Dealloc(&writer);
     return 0;
 }
@@ -10996,9 +11044,9 @@ _PyUnicode_EqualToASCIIId(PyObject *left, _Py_Identifier *right)
         return 0;
     }
 
-    Py_hash_t right_hash = FT_ATOMIC_LOAD_SSIZE_RELAXED(_PyUnicode_HASH(right_uni));
+    Py_hash_t right_hash = PyUnicode_HASH(right_uni);
     assert(right_hash != -1);
-    Py_hash_t hash = FT_ATOMIC_LOAD_SSIZE_RELAXED(_PyUnicode_HASH(left));
+    Py_hash_t hash = PyUnicode_HASH(left);
     if (hash != -1 && hash != right_hash) {
         return 0;
     }
@@ -11484,14 +11532,14 @@ unicode_hash(PyObject *self)
 #ifdef Py_DEBUG
     assert(_Py_HashSecret_Initialized);
 #endif
-    Py_hash_t hash = FT_ATOMIC_LOAD_SSIZE_RELAXED(_PyUnicode_HASH(self));
+    Py_hash_t hash = PyUnicode_HASH(self);
     if (hash != -1) {
         return hash;
     }
     x = _Py_HashBytes(PyUnicode_DATA(self),
                       PyUnicode_GET_LENGTH(self) * PyUnicode_KIND(self));
 
-    FT_ATOMIC_STORE_SSIZE_RELAXED(_PyUnicode_HASH(self), x);
+    PyUnicode_SET_HASH(self, x);
     return x;
 }
 
@@ -14888,8 +14936,8 @@ unicode_subtype_new(PyTypeObject *type, PyObject *unicode)
     _PyUnicode_STATE(self).compact = 0;
     _PyUnicode_STATE(self).ascii = _PyUnicode_STATE(unicode).ascii;
     _PyUnicode_STATE(self).statically_allocated = 0;
-    _PyUnicode_UTF8_LENGTH(self) = 0;
-    _PyUnicode_UTF8(self) = NULL;
+    PyUnicode_SET_UTF8_LENGTH(self, 0);
+    PyUnicode_SET_UTF8(self, NULL);
     _PyUnicode_DATA_ANY(self) = NULL;
 
     share_utf8 = 0;
@@ -14919,8 +14967,8 @@ unicode_subtype_new(PyTypeObject *type, PyObject *unicode)
 
     _PyUnicode_DATA_ANY(self) = data;
     if (share_utf8) {
-        _PyUnicode_UTF8_LENGTH(self) = length;
-        _PyUnicode_UTF8(self) = data;
+        PyUnicode_SET_UTF8_LENGTH(self, length);
+        PyUnicode_SET_UTF8(self, data);
     }
 
     memcpy(data, PyUnicode_DATA(unicode), kind * (length + 1));