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bpo-40014: Fix os.getgrouplist() (GH-19126)

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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 Fix ``os.getgrouplist()``: if ``getgrouplist()`` function fails because the
non-zero value without setting ``errno`` if the group list is too small. Double group list is too small, retry with a larger group list. On failure, the glibc
the list size and call it again in this case. implementation of ``getgrouplist()`` sets ``ngroups`` to the total number of
groups. For other implementations, double the group list size.

35
Modules/posixmodule.c
View file

@ -6991,37 +6991,40 @@ posix_getgrouplist(PyObject *self, PyObject *args)
return NULL; return NULL;
#endif #endif
while (1) {
#ifdef __APPLE__ #ifdef __APPLE__
groups = PyMem_New(int, ngroups); groups = PyMem_New(int, ngroups);
#else #else
groups = PyMem_New(gid_t, ngroups); groups = PyMem_New(gid_t, ngroups);
#endif #endif
if (groups == NULL) if (groups == NULL) {
return PyErr_NoMemory(); return PyErr_NoMemory();
}
#ifdef __APPLE__ int old_ngroups = ngroups;
while (getgrouplist(user, basegid, groups, &ngroups)) { if (getgrouplist(user, basegid, groups, &ngroups) != -1) {
/* On macOS, getgrouplist() returns a non-zero value without setting /* Success */
errno if the group list is too small. Double the list size and call break;
it again in this case. */ }
/* getgrouplist() fails if the group list is too small */
PyMem_Free(groups); 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) { if (ngroups > INT_MAX / 2) {
return PyErr_NoMemory(); return PyErr_NoMemory();
} }
ngroups *= 2; ngroups *= 2;
}
groups = PyMem_New(int, ngroups); /* Retry getgrouplist() with a larger group list */
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 #ifdef _Py_MEMORY_SANITIZER
/* Clang memory sanitizer libc intercepts don't know getgrouplist. */ /* Clang memory sanitizer libc intercepts don't know getgrouplist. */