Skip to content

bpo-30570: fix an issubclass infinite recursion crash #29017

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wants to merge 1 commit into from
Closed

bpo-30570: fix an issubclass infinite recursion crash #29017

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
8 changes: 8 additions & 0 deletions Lib/test/test_isinstance.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -313,6 +313,14 @@ def __bases__(self):
self.assertRaises(RecursionError, issubclass, int, X())
self.assertRaises(RecursionError, isinstance, 1, X())

def test_infinite_recursion_via_bases_tuple(self):
"""Regression test for bpo-30570."""
class Failure(object):
def __getattr__(self, attr):
return (self, None)

self.assertFalse(issubclass(Failure(), int))


def blowstack(fxn, arg, compare_to):
# Make sure that calling isinstance with a deeply nested tuple for its
Expand Down
37 changes: 35 additions & 2 deletions Objects/abstract.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2525,7 +2525,8 @@ abstract_get_bases(PyObject *cls)


static int
abstract_issubclass(PyObject *derived, PyObject *cls)
_abstract_issubclass_inner(PyObject *derived, PyObject *cls,
PyObject* visited_set)
{
PyObject *bases = NULL;
Py_ssize_t i, n;
Expand Down Expand Up @@ -2558,7 +2559,24 @@ abstract_issubclass(PyObject *derived, PyObject *cls)
continue;
}
for (i = 0; i < n; i++) {
r = abstract_issubclass(PyTuple_GET_ITEM(bases, i), cls);
PyObject *borrowed_base = PyTuple_GET_ITEM(bases, i);
PyObject *visitor = PyLong_FromVoidPtr(borrowed_base);
if (visitor == NULL) {
Py_DECREF(bases);
return -1;
}
if (PySet_Contains(visited_set, visitor)) {
Py_DECREF(visitor);
continue;
}
if (PySet_Add(visited_set, visitor) < 0) {
Py_DECREF(visitor);
Py_DECREF(bases);
return -1;
}
Py_DECREF(visitor); // PySet_Add does its own INCREF.
r = _abstract_issubclass_inner(
borrowed_base, cls, visited_set);
if (r != 0)
break;
}
Expand All @@ -2567,6 +2585,21 @@ abstract_issubclass(PyObject *derived, PyObject *cls)
}
}

static int
abstract_issubclass(PyObject *derived, PyObject *cls)
{
int result;
/* I would much rather use a C++ hash_map but we're stuck in C so
* we'll use our own high overhead for the purpose data structure. */
PyObject *visited_set = PySet_New(NULL);
if (visited_set == NULL) {
return -1;
}
result = _abstract_issubclass_inner(derived, cls, visited_set);
Py_DECREF(visited_set);
return result;
}

static int
check_class(PyObject *cls, const char *error)
{
Expand Down