bpo-42655: Fix subprocess extra_groups gid conversion (pythonGH-23762)

(cherry picked from commit 0159e5e)

Co-authored-by: Jakub Kulík <Kulikjak@gmail.com>

Author: miss-islington

Misc/NEWS.d/next/Library/2020-12-25-12-32-47.bpo-42655.W5ytpV.rst

@@ -0,0 +1,2 @@
+:mod:`subprocess` *extra_groups* is now correctly passed into setgroups()
+system call.

Modules/_posixsubprocess.c

@@ -753,7 +753,7 @@ subprocess_fork_exec(PyObject* self, PyObject *args)
     if (groups_list != Py_None) {
 #ifdef HAVE_SETGROUPS
         Py_ssize_t i;
-        unsigned long gid;
+        gid_t gid;
 
         if (!PyList_Check(groups_list)) {
             PyErr_SetString(PyExc_TypeError,
@@ -787,10 +787,6 @@ subprocess_fork_exec(PyObject* self, PyObject *args)
                 Py_DECREF(elem);
                 goto cleanup;
             } else {
-                /* In posixmodule.c UnsignedLong is used as a fallback value
-                * if the value provided does not fit in a Long. Since we are
-                * already doing the bounds checking on the Python side, we
-                * can go directly to an UnsignedLong here. */
                 if (!_Py_Gid_Converter(elem, &gid)) {
                     Py_DECREF(elem);
                     PyErr_SetString(PyExc_ValueError, "invalid group id");

Modules/posixmodule.c

@@ -632,7 +632,7 @@ _PyLong_FromGid(gid_t gid)
 }
 
 int
-_Py_Uid_Converter(PyObject *obj, void *p)
+_Py_Uid_Converter(PyObject *obj, uid_t *p)
 {
     uid_t uid;
     PyObject *index;
@@ -719,7 +719,7 @@ _Py_Uid_Converter(PyObject *obj, void *p)
 
 success:
     Py_DECREF(index);
-    *(uid_t *)p = uid;
+    *p = uid;
     return 1;
 
 underflow:
@@ -738,7 +738,7 @@ _Py_Uid_Converter(PyObject *obj, void *p)
 }
 
 int
-_Py_Gid_Converter(PyObject *obj, void *p)
+_Py_Gid_Converter(PyObject *obj, gid_t *p)
 {
     gid_t gid;
     PyObject *index;
@@ -826,7 +826,7 @@ _Py_Gid_Converter(PyObject *obj, void *p)
 
 success:
     Py_DECREF(index);
-    *(gid_t *)p = gid;
+    *p = gid;
     return 1;
 
 underflow:

Modules/posixmodule.h

@@ -14,8 +14,8 @@ extern "C" {
 #ifndef MS_WINDOWS
 PyAPI_FUNC(PyObject *) _PyLong_FromUid(uid_t);
 PyAPI_FUNC(PyObject *) _PyLong_FromGid(gid_t);
-PyAPI_FUNC(int) _Py_Uid_Converter(PyObject *, void *);
-PyAPI_FUNC(int) _Py_Gid_Converter(PyObject *, void *);
+PyAPI_FUNC(int) _Py_Uid_Converter(PyObject *, uid_t *);
+PyAPI_FUNC(int) _Py_Gid_Converter(PyObject *, gid_t *);
 #endif /* MS_WINDOWS */
 
 #if defined(PYPTHREAD_SIGMASK) || defined(HAVE_SIGWAIT) || \