bpo-40014: Fix os.getgrouplist() (GH-19126)
Fix os.getgrouplist(): if getgrouplist() function fails because the
group list is too small, retry with a larger group list.
On failure, the glibc implementation of getgrouplist() sets ngroups
to the total number of groups. For other implementations, double the
group list size.
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
index 58f14fa..e9b36c2 100644
--- 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
@@ -1,3 +1,4 @@
-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.
+Fix ``os.getgrouplist()``: if ``getgrouplist()`` function fails because the
+group list is too small, retry with a larger group list. On failure, the glibc
+implementation of ``getgrouplist()`` sets ``ngroups`` to the total number of
+groups. For other implementations, double the group list size.
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index e489b74..9ab136b 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -6991,37 +6991,40 @@
return NULL;
#endif
+ while (1) {
#ifdef __APPLE__
- groups = PyMem_New(int, ngroups);
-#else
- groups = PyMem_New(gid_t, ngroups);
-#endif
- 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);
+#else
+ groups = PyMem_New(gid_t, ngroups);
+#endif
if (groups == NULL) {
return PyErr_NoMemory();
}
+
+ int old_ngroups = ngroups;
+ if (getgrouplist(user, basegid, groups, &ngroups) != -1) {
+ /* Success */
+ break;
+ }
+
+ /* getgrouplist() fails if the group list is too small */
+ PyMem_Free(groups);
+
+ if (ngroups > old_ngroups) {
+ /* If the group list is too small, the glibc implementation of
+ getgrouplist() sets ngroups to the total number of groups and
+ returns -1. */
+ }
+ else {
+ /* Double the group list size */
+ if (ngroups > INT_MAX / 2) {
+ return PyErr_NoMemory();
+ }
+ ngroups *= 2;
+ }
+
+ /* Retry getgrouplist() with a larger group list */
}
-#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. */