Fix use-after-free during lazy object initialization#22401
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I can't really comment about the fix but here's one small thing I did notice.
| zval garbage; | ||
| ZVAL_COPY_VALUE(&garbage, p); | ||
| ZVAL_UNDEF(p); | ||
| i_zval_ptr_dtor(&garbage); |
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zend_lazy_object_revert_init is entirely off the hot path, right? I think zval_ptr_dtor would be more appropriate to avoid excess code size?
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Right, switched both new dtors to zval_ptr_dtor.
zend_lazy_object_revert_init() and zend_lazy_object_init_proxy() dropped a property value's refcount while the slot or dynamic-properties table still aliased it, so a value whose destructor reaches back through a reference cycle (unset($this->obj->prop)) freed it twice. Clear the slot and detach the properties table before dropping the refcount. Fixes phpGH-22399
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Lazy object initialization destroyed property values while the slot or the dynamic-properties
HashTablestill aliased them, so a value whose__destructreaches back through a reference cycle (unset($this->obj->prop)) double-freed it, a UAF inzend_objects_store_del. The fix clears the slot and detaches the properties table before dropping the refcount, across all four destruction sites inzend_lazy_object_revert_initandzend_lazy_object_init_proxy(declared and dynamic properties, ghost revert and proxy cleanup); verified under ASAN.Fixes GH-22399