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.
(cherry picked from commit f5c7cabb2be4e42a5975ba8aac8bb458c8d9d6d7)
Co-authored-by: Victor Stinner <vstinner@python.org>
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index be7ebb6..d40827d 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -6906,37 +6906,40 @@
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. */