Fix OSS Fuzz #61865: Undef variable in ++/-- for declared property that is unset in error handler #12114
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iluuu1994
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Sep 3, 2023
Zend/zend_object_handlers.c
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| zend_error(E_WARNING, "Undefined property: %s::$%s", ZSTR_VAL(zobj->ce->name), ZSTR_VAL(name)); | ||
| /* We set the retval to null AFTER the warning so that an error handler cannot mess | ||
| * with the property value... */ | ||
| ZVAL_NULL(retval); |
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This can leak.
class Foo {}
class C {
public $a;
function errorHandler($errno, $errstr) {
$this->a = new Foo();
}
}
$c = new C;
set_error_handler([$c,'errorHandler']);
unset($c->a);
(++$c->a);
var_dump($c->a);Just wrapping the ZVAL_NULL in a if (Z_TYPE_P(retval) == IS_UNDEF) { should do. This will change the behavior to throw a "TypeError: Cannot increment Foo" exception, which I think is what I would expect.
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I guess if we want that, then for consistency the zend_hash_update for the dynamic case should become zend_hash_add instead too?
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@nielsdos That probably makes sense. The leak doesn't happen in that case because the hash table takes care of releasing the old value.
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With the fix in php#12114, the behaviour would change for non-dynamic properties. Align the behaviour for dynamic properties to be the same.
…at is unset in error handler Reorder when we assign the property value to NULL which is identical to a3a3964 Just for the declared property case instead of dynamic.
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iluuu1994
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Sep 5, 2023
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Reorder when we assign the property value to NULL which is identical to a3a3964
Just for the declared property case instead of dynamic.