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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.
This commit is contained in:
Victor Stinner 2020-03-24 18:22:10 +01:00 committed by GitHub
parent 4b3252cb76
commit f5c7cabb2b
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2 changed files with 32 additions and 28 deletions
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7
Misc/NEWS.d/next/Library/2020-03-23-17-52-00.bpo-40014.Ya70VG.rst
View File

@ -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.

53
Modules/posixmodule.c
View File

@ -6991,37 +6991,40 @@ posix_getgrouplist(PyObject *self, PyObject *args)
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. */