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bpo-29438: fixed use-after-free in key sharing dict #17

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Feb 12, 2017
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bpo-29438: fixed use-after-free in key sharing dict #17

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2 changes: 2 additions & 0 deletions Misc/NEWS
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,8 @@ What's New in Python 3.7.0 alpha 1?
Core and Builtins
-----------------

- bpo-29438: Fixed use-after-free problem in key sharing dict.

- Issue #29319: Prevent RunMainFromImporter overwriting sys.path[0].

- Issue #29337: Fixed possible BytesWarning when compare the code objects.
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10 changes: 7 additions & 3 deletions Objects/dictobject.c
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Expand Up @@ -4352,15 +4352,19 @@ _PyObjectDict_SetItem(PyTypeObject *tp, PyObject **dictptr,
}
if (value == NULL) {
res = PyDict_DelItem(dict, key);
if (cached != ((PyDictObject *)dict)->ma_keys) {
// Since key sharing dict doesn't allow deletion, PyDict_DelItem()
// always converts dict to combined form.
if ((cached = CACHED_KEYS(tp)) != NULL) {
CACHED_KEYS(tp) = NULL;
DK_DECREF(cached);
}
}
else {
int was_shared = cached == ((PyDictObject *)dict)->ma_keys;
int was_shared = (cached == ((PyDictObject *)dict)->ma_keys);
res = PyDict_SetItem(dict, key, value);
if (was_shared && cached != ((PyDictObject *)dict)->ma_keys) {
if (was_shared &&
(cached = CACHED_KEYS(tp)) != NULL &&
cached != ((PyDictObject *)dict)->ma_keys) {
/* PyDict_SetItem() may call dictresize and convert split table
* into combined table. In such case, convert it to split
* table again and update type's shared key only when this is
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