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Commit 23192ab

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[3.12] GH-115874: Fix segfault in FutureIter_dealloc (GH-118114)
GH-115874: Fix segfault in FutureIter_dealloc (GH-117741) (cherry picked from commit d8f3503) Co-authored-by: Savannah Ostrowski <savannahostrowski@gmail.com>
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Fixed a possible segfault during garbage collection of ``_asyncio.FutureIter`` objects

‎Modules/_asynciomodule.c

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+16-2Lines changed: 16 additions & 2 deletions
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@@ -1590,11 +1590,25 @@ static void
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FutureIter_dealloc(futureiterobject *it)
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{
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PyTypeObject *tp = Py_TYPE(it);
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asyncio_state *state = get_asyncio_state_by_def((PyObject *)it);
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// FutureIter is a heap type so any subclass must also be a heap type.
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assert(_PyType_HasFeature(tp, Py_TPFLAGS_HEAPTYPE));
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PyObject *module = ((PyHeapTypeObject*)tp)->ht_module;
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asyncio_state *state = NULL;
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PyObject_GC_UnTrack(it);
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tp->tp_clear((PyObject *)it);
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if (state->fi_freelist_len < FI_FREELIST_MAXLEN) {
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// GH-115874: We can't use PyType_GetModuleByDef here as the type might have
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// already been cleared, which is also why we must check if ht_module != NULL.
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// Due to this restriction, subclasses that belong to a different module
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// will not be able to use the free list.
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if (module && _PyModule_GetDef(module) == &_asynciomodule) {
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state = get_asyncio_state(module);
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}
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if (state && state->fi_freelist_len < FI_FREELIST_MAXLEN) {
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state->fi_freelist_len++;
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it->future = (FutureObj*) state->fi_freelist;
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state->fi_freelist = it;

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