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[3.9] bpo-40705: Fix use-after-free in _zoneinfo's module_free (GH-20280) #20319

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Merged
merged 1 commit into from
May 24, 2020
Merged

[3.9] bpo-40705: Fix use-after-free in _zoneinfo's module_free (GH-20280) #20319

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15 changes: 9 additions & 6 deletions Modules/_zoneinfo.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2490,6 +2490,7 @@ new_weak_cache()
static int
initialize_caches()
{
// TODO: Move to a PyModule_GetState / PEP 573 based caching system.
if (TIMEDELTA_CACHE == NULL) {
TIMEDELTA_CACHE = PyDict_New();
}
Expand Down Expand Up @@ -2603,14 +2604,16 @@ module_free()

xdecref_ttinfo(&NO_TTINFO);

Py_XDECREF(TIMEDELTA_CACHE);
if (!Py_REFCNT(TIMEDELTA_CACHE)) {
TIMEDELTA_CACHE = NULL;
if (TIMEDELTA_CACHE != NULL && Py_REFCNT(TIMEDELTA_CACHE) > 1) {
Py_DECREF(TIMEDELTA_CACHE);
} else {
Py_CLEAR(TIMEDELTA_CACHE);
}

Py_XDECREF(ZONEINFO_WEAK_CACHE);
if (!Py_REFCNT(ZONEINFO_WEAK_CACHE)) {
ZONEINFO_WEAK_CACHE = NULL;
if (ZONEINFO_WEAK_CACHE != NULL && Py_REFCNT(ZONEINFO_WEAK_CACHE) > 1) {
Py_DECREF(ZONEINFO_WEAK_CACHE);
} else {
Py_CLEAR(ZONEINFO_WEAK_CACHE);
}

strong_cache_free(ZONEINFO_STRONG_CACHE);
Expand Down