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gh-117657: Fix data race in compare_unicode_unicode_threadsafe (gh-131746)

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We can't safely check the type of the found key until we incref it or if we know that it's immortal.
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Sam Gross 2025-03-26 09:01:57 -04:00 • committed by GitHub
parent ac12de2e6a
commit 5abff6960b
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1 changed files with 3 additions and 1 deletions
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4
Objects/dictobject.c
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@ -1412,18 +1412,20 @@ compare_unicode_unicode_threadsafe(PyDictObject *mp, PyDictKeysObject *dk,
{ {
PyDictUnicodeEntry *ep = &((PyDictUnicodeEntry *)ep0)[ix]; PyDictUnicodeEntry *ep = &((PyDictUnicodeEntry *)ep0)[ix];
PyObject *startkey = _Py_atomic_load_ptr_relaxed(&ep->me_key); PyObject *startkey = _Py_atomic_load_ptr_relaxed(&ep->me_key);
assert(startkey == NULL || PyUnicode_CheckExact(startkey));
if (startkey == key) { if (startkey == key) {
assert(PyUnicode_CheckExact(startkey));
return 1; return 1;
} }
if (startkey != NULL) { if (startkey != NULL) {
if (_Py_IsImmortal(startkey)) { if (_Py_IsImmortal(startkey)) {
assert(PyUnicode_CheckExact(startkey));
return unicode_get_hash(startkey) == hash && unicode_eq(startkey, key); return unicode_get_hash(startkey) == hash && unicode_eq(startkey, key);
} }
else { else {
if (!_Py_TryIncrefCompare(&ep->me_key, startkey)) { if (!_Py_TryIncrefCompare(&ep->me_key, startkey)) {
return DKIX_KEY_CHANGED; return DKIX_KEY_CHANGED;
} }
assert(PyUnicode_CheckExact(startkey));
if (unicode_get_hash(startkey) == hash && unicode_eq(startkey, key)) { if (unicode_get_hash(startkey) == hash && unicode_eq(startkey, key)) {
Py_DECREF(startkey); Py_DECREF(startkey);
return 1; return 1;