From 12db45211d411583cbe272c7ba6811a811b721ca Mon Sep 17 00:00:00 2001 From: Sam Gross Date: Fri, 7 Mar 2025 10:34:53 -0500 Subject: gh-130851: Only intern constants of types generated by the compiler (#130901) The free-threading build interns and immortalizes most constants generated by the bytecode compiler. However, users can construct their own code objects with arbitrary constants. We should not intern or immortalize these objects if they are not of a type that we know how to handle. This change fixes a reference leak failure in the recently added `test_code.test_unusual_constants` test. It also addresses a potential crash that could occur when attempting to destroy an immortalized object during interpreter shutdown. --- Objects/codeobject.c | 43 +++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 41 insertions(+), 2 deletions(-) diff --git a/Objects/codeobject.c b/Objects/codeobject.c index 5d23a7a..60563ea 100644 --- a/Objects/codeobject.c +++ b/Objects/codeobject.c @@ -135,6 +135,44 @@ should_intern_string(PyObject *o) #ifdef Py_GIL_DISABLED static PyObject *intern_one_constant(PyObject *op); + +// gh-130851: In the free threading build, we intern and immortalize most +// constants, except code objects. However, users can generate code objects +// with arbitrary co_consts. We don't want to immortalize or intern unexpected +// constants or tuples/sets containing unexpected constants. +static int +should_immortalize_constant(PyObject *v) +{ + // Only immortalize containers if we've already immortalized all their + // elements. + if (PyTuple_CheckExact(v)) { + for (Py_ssize_t i = PyTuple_GET_SIZE(v); --i >= 0; ) { + if (!_Py_IsImmortal(PyTuple_GET_ITEM(v, i))) { + return 0; + } + } + return 1; + } + else if (PyFrozenSet_CheckExact(v)) { + PyObject *item; + Py_hash_t hash; + Py_ssize_t pos = 0; + while (_PySet_NextEntry(v, &pos, &item, &hash)) { + if (!_Py_IsImmortal(item)) { + return 0; + } + } + return 1; + } + else if (PySlice_Check(v)) { + PySliceObject *slice = (PySliceObject *)v; + return (_Py_IsImmortal(slice->start) && + _Py_IsImmortal(slice->stop) && + _Py_IsImmortal(slice->step)); + } + return (PyLong_CheckExact(v) || PyFloat_CheckExact(v) || + PyComplex_Check(v) || PyBytes_CheckExact(v)); +} #endif static int @@ -241,8 +279,9 @@ intern_constants(PyObject *tuple, int *modified) // Intern non-string constants in the free-threaded build _PyThreadStateImpl *tstate = (_PyThreadStateImpl *)_PyThreadState_GET(); - if (!_Py_IsImmortal(v) && !PyCode_Check(v) && - !PyUnicode_CheckExact(v) && !tstate->suppress_co_const_immortalization) + if (!_Py_IsImmortal(v) && !PyUnicode_CheckExact(v) && + should_immortalize_constant(v) && + !tstate->suppress_co_const_immortalization) { PyObject *interned = intern_one_constant(v); if (interned == NULL) { -- cgit v0.12