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gh-148653: Fix some marshal errors related to recursive immutable objects (GH-148698)

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Forbid marshalling recursive code, slice and frozendict objects which
cannot be correctly unmarshalled.
Reject invalid marshal data produced by marshalling recursive frozendict
objects which was previously incorrectly unmarshalled.
Add multiple tests for recursive data structures.
This commit is contained in:
Serhiy Storchaka
2026-04-18 11:24:33 +03:00
committed by GitHub
parent 92164dc917
commit 2e37d83641
3 changed files with 182 additions and 16 deletions
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Python/marshal.c
+53 -16
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@@ -382,7 +382,6 @@ static int
w_ref(PyObject *v, char *flag, WFILE *p)
{
_Py_hashtable_entry_t *entry;
int w;
if (p->version < 3 || p->hashtable == NULL)
return 0; /* not writing object references */
@@ -399,20 +398,28 @@ w_ref(PyObject *v, char *flag, WFILE *p)
entry = _Py_hashtable_get_entry(p->hashtable, v);
if (entry != NULL) {
/* write the reference index to the stream */
w = (int)(uintptr_t)entry->value;
uintptr_t w = (uintptr_t)entry->value;
if (w & 0x80000000LU) {
PyErr_Format(PyExc_ValueError, "cannot marshal recursion %T objects", v);
goto err;
}
/* we don't store "long" indices in the dict */
assert(0 <= w && w <= 0x7fffffff);
assert(w <= 0x7fffffff);
w_byte(TYPE_REF, p);
w_long(w, p);
w_long((int)w, p);
return 1;
} else {
size_t s = p->hashtable->nentries;
size_t w = p->hashtable->nentries;
/* we don't support long indices */
if (s >= 0x7fffffff) {
if (w >= 0x7fffffff) {
PyErr_SetString(PyExc_ValueError, "too many objects");
goto err;
}
w = (int)s;
// Corresponding code should call w_complete() after
// writing the object.
if (PyCode_Check(v) || PySlice_Check(v) || PyFrozenDict_CheckExact(v)) {
w |= 0x80000000LU;
}
if (_Py_hashtable_set(p->hashtable, Py_NewRef(v),
(void *)(uintptr_t)w) < 0) {
Py_DECREF(v);
@@ -426,6 +433,27 @@ err:
return 1;
}
static void
w_complete(PyObject *v, WFILE *p)
{
if (p->version < 3 || p->hashtable == NULL) {
return;
}
if (_PyObject_IsUniquelyReferenced(v)) {
return;
}
_Py_hashtable_entry_t *entry = _Py_hashtable_get_entry(p->hashtable, v);
if (entry == NULL) {
return;
}
assert(entry != NULL);
uintptr_t w = (uintptr_t)entry->value;
assert(w & 0x80000000LU);
w &= ~0x80000000LU;
entry->value = (void *)(uintptr_t)w;
}
static void
w_complex_object(PyObject *v, char flag, WFILE *p);
@@ -599,6 +627,9 @@ w_complex_object(PyObject *v, char flag, WFILE *p)
w_object(value, p);
}
w_object((PyObject *)NULL, p);
if (PyFrozenDict_CheckExact(v)) {
w_complete(v, p);
}
}
else if (PyAnySet_CheckExact(v)) {
PyObject *value;
@@ -684,6 +715,7 @@ w_complex_object(PyObject *v, char flag, WFILE *p)
w_object(co->co_linetable, p);
w_object(co->co_exceptiontable, p);
Py_DECREF(co_code);
w_complete(v, p);
}
else if (PyObject_CheckBuffer(v)) {
/* Write unknown bytes-like objects as a bytes object */
@@ -709,6 +741,7 @@ w_complex_object(PyObject *v, char flag, WFILE *p)
w_object(slice->start, p);
w_object(slice->stop, p);
w_object(slice->step, p);
w_complete(v, p);
}
else {
W_TYPE(TYPE_UNKNOWN, p);
@@ -1433,9 +1466,19 @@ r_object(RFILE *p)
case TYPE_DICT:
case TYPE_FROZENDICT:
v = PyDict_New();
R_REF(v);
if (v == NULL)
if (v == NULL) {
break;
}
if (type == TYPE_DICT) {
R_REF(v);
}
else {
idx = r_ref_reserve(flag, p);
if (idx < 0) {
Py_CLEAR(v);
break;
}
}
for (;;) {
PyObject *key, *val;
key = r_object(p);
@@ -1458,13 +1501,7 @@ r_object(RFILE *p)
Py_CLEAR(v);
}
if (type == TYPE_FROZENDICT && v != NULL) {
PyObject *frozendict = PyFrozenDict_New(v);
if (frozendict != NULL) {
Py_SETREF(v, frozendict);
}
else {
Py_CLEAR(v);
}
Py_SETREF(v, PyFrozenDict_New(v));
}
retval = v;
break;