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Fix invalid access when reinterpret_casting a non-pybind11 PyObject* to instance* (found by Valgrind in #2746) #2755

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Merged
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Dec 31, 2020
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Fix invalid access when reinterpret_casting a non-pybind11 PyObject* to instance* (found by Valgrind in #2746) #2755

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10 changes: 5 additions & 5 deletions include/pybind11/pybind11.h
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Original file line number Diff line number Diff line change
Expand Up @@ -504,15 +504,15 @@ class cpp_function : public function {

auto self_value_and_holder = value_and_holder();
if (overloads->is_constructor) {
const auto tinfo = get_type_info((PyTypeObject *) overloads->scope.ptr());
const auto pi = reinterpret_cast<instance *>(parent.ptr());
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@YannickJadoul YannickJadoul Dec 30, 2020 •
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Comments from #2746:

  • @bstaletic: Without checking the type first, we were reinterpreting NotPybindDerived() as instance*.
  • @YannickJadoul: See also the code below that gets simplified; cfr. if (!self_value_and_holder.type || !self_value_and_holder.inst) -> pi->get_value_and_holder(tinfo, true);

self_value_and_holder = pi->get_value_and_holder(tinfo, false);

if (!self_value_and_holder.type || !self_value_and_holder.inst) {
if (!PyObject_TypeCheck(parent.ptr(), (PyTypeObject *) overloads->scope.ptr())) {
PyErr_SetString(PyExc_TypeError, "__init__(self, ...) called with invalid `self` argument");
return nullptr;
}

const auto tinfo = get_type_info((PyTypeObject *) overloads->scope.ptr());
const auto pi = reinterpret_cast<instance *>(parent.ptr());
self_value_and_holder = pi->get_value_and_holder(tinfo, true);

// If this value is already registered it must mean __init__ is invoked multiple times;
// we really can't support that in C++, so just ignore the second __init__.
if (self_value_and_holder.instance_registered())
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