bpo-40014: Fix os.getgrouplist() on macOS (GH-19118)

miss-islington · vstinner · web-flow · commit 1cdc61c7673f · 2020-03-23T12:21:07.000-07:00
On macOS, getgrouplist() returns a non-zero value without setting errno if the group list is too small. Double the list size and call it again in this case. (cherry picked from commit 8ec7370) Co-authored-by: Victor Stinner <vstinner@python.org>
diff --git a/Misc/NEWS.d/next/Library/2020-03-23-17-52-00.bpo-40014.Ya70VG.rst b/Misc/NEWS.d/next/Library/2020-03-23-17-52-00.bpo-40014.Ya70VG.rst
@@ -0,0 +1,3 @@
+Fix ``os.getgrouplist()``: on macOS, the ``getgrouplist()`` function returns a
+non-zero value without setting ``errno`` if the group list is too small. Double
+the list size and call it again in this case.
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
@@ -6178,10 +6178,29 @@ posix_getgrouplist(PyObject *self, PyObject *args)
     if (groups == NULL)
         return PyErr_NoMemory();
 
+#ifdef __APPLE__
+    while (getgrouplist(user, basegid, groups, &ngroups)) {
+        /* On macOS, getgrouplist() returns a non-zero value without setting
+           errno if the group list is too small. Double the list size and call
+           it again in this case. */
+        PyMem_Free(groups);
+
+        if (ngroups > INT_MAX / 2) {
+            return PyErr_NoMemory();
+        }
+        ngroups *= 2;
+
+        groups = PyMem_New(int, ngroups);
+        if (groups == NULL) {
+            return PyErr_NoMemory();
+        }
+    }
+#else
     if (getgrouplist(user, basegid, groups, &ngroups) == -1) {
         PyMem_Del(groups);
         return posix_error();
     }
+#endif
 
 #ifdef _Py_MEMORY_SANITIZER
     /* Clang memory sanitizer libc intercepts don't know getgrouplist. */

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	+Fix ``os.getgrouplist()``: on macOS, the ``getgrouplist()`` function returns a
	`2`	+non-zero value without setting ``errno`` if the group list is too small. Double
	`3`	`+the list size and call it again in this case.`