From: Sam Gross <colesbury@gmail.com>
Date: Thu, 2 Jan 2025 19:02:54 +0000 (-0500)
Subject: gh-128212: Fix race in `_PyUnicode_CheckConsistency` (GH-128367)
X-Git-Tag: v3.14.0a4~144
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=8eebe4e6d02bb4ad3f1ca6c52624186903dce893;p=thirdparty%2FPython%2Fcpython.git

gh-128212: Fix race in `_PyUnicode_CheckConsistency` (GH-128367)

There was a data race on the utf8 field between `PyUnicode_SET_UTF8` and
`_PyUnicode_CheckConsistency`. Use the `_PyUnicode_UTF8()` accessor,
which uses an atomic load internally, to avoid the data race.
---

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 1aab9cf37768..9f0a4d4785ed 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -688,7 +688,7 @@ _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);