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gh-99240: Reset pointer to NULL when the pointed memory is freed in argument parsing #99890

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Dec 17, 2022
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4 changes: 4 additions & 0 deletions Lib/test/test_capi/test_getargs.py
Original file line number Diff line number Diff line change
Expand Up @@ -1085,6 +1085,10 @@ def test_Z_hash(self):
with self.assertWarns(DeprecationWarning):
self.assertIsNone(getargs_Z_hash(None))

def test_gh_99240_clear_args(self):
from _testcapi import gh_99240_clear_args
self.assertRaises(TypeError, gh_99240_clear_args, 'a', '\0b')


class Object_TestCase(unittest.TestCase):
def test_S(self):
Expand Down
Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
In argument parsing, after deallocating newly allocated memory, reset its
pointer to NULL.
18 changes: 18 additions & 0 deletions Modules/_testcapi/getargs.c
Original file line number Diff line number Diff line change
Expand Up @@ -854,6 +854,23 @@ getargs_s_hash_int2(PyObject *self, PyObject *args, PyObject *kwargs)
Py_RETURN_NONE;
}

static PyObject *
gh_99240_clear_args(PyObject *self, PyObject *args) {
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char *a = NULL;
char *b = NULL;

if (!PyArg_ParseTuple(args, "eses", "idna", &a, "idna", &b)) {
if (a || b) {
PyErr_Clear();
PyErr_SetString(PyExc_AssertionError, "Arguments are not cleared.");
}
return NULL;
}
PyMem_Free(a);
PyMem_Free(b);
Py_RETURN_NONE;
}

static PyMethodDef test_methods[] = {
{"get_args", get_args, METH_VARARGS},
{"get_kwargs", _PyCFunction_CAST(get_kwargs), METH_VARARGS|METH_KEYWORDS},
Expand Down Expand Up @@ -906,6 +923,7 @@ static PyMethodDef test_methods[] = {
{"test_empty_argparse", test_empty_argparse, METH_NOARGS},
{"test_k_code", test_k_code, METH_NOARGS},
{"test_s_code", test_s_code, METH_NOARGS},
{"gh_99240_clear_args", gh_99240_clear_args, METH_VARARGS},
{NULL},
};

Expand Down
10 changes: 5 additions & 5 deletions Python/getargs.c
Original file line number Diff line number Diff line change
Expand Up @@ -202,9 +202,9 @@ _PyArg_VaParse_SizeT(PyObject *args, const char *format, va_list va)
static int
cleanup_ptr(PyObject *self, void *ptr)
{
if (ptr) {
PyMem_Free(ptr);
}
void **pptr = (void **)ptr;
PyMem_Free(*pptr);
*pptr = NULL;
return 0;
}

Expand Down Expand Up @@ -1116,7 +1116,7 @@ convertsimple(PyObject *arg, const char **p_format, va_list *p_va, int flags,
PyErr_NoMemory();
RETURN_ERR_OCCURRED;
}
if (addcleanup(*buffer, freelist, cleanup_ptr)) {
if (addcleanup(buffer, freelist, cleanup_ptr)) {
Py_DECREF(s);
return converterr(
"(cleanup problem)",
Expand Down Expand Up @@ -1162,7 +1162,7 @@ convertsimple(PyObject *arg, const char **p_format, va_list *p_va, int flags,
PyErr_NoMemory();
RETURN_ERR_OCCURRED;
}
if (addcleanup(*buffer, freelist, cleanup_ptr)) {
if (addcleanup(buffer, freelist, cleanup_ptr)) {
Py_DECREF(s);
return converterr("(cleanup problem)",
arg, msgbuf, bufsize);
Expand Down