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Fix use-after-free in RecursiveIteratorIterator on reentry #22466

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iliaal wants to merge 1 commit into from
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Fix use-after-free in RecursiveIteratorIterator on reentry #22466

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1 change: 1 addition & 0 deletions ext/spl/spl_iterators.c
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Original file line number Diff line number Diff line change
Expand Up @@ -273,6 +273,7 @@ static void spl_recursive_it_move_forward_ex(spl_recursive_it_object *object, zv
zend_clear_exception();
}
}
iterator = object->iterators[object->level].iterator;

@devnexen devnexen Jun 26, 2026

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Since endChildren()/valid() are also reentry points, it might be worth dtoring object->iterators[object->level].iterator at line 431 with a new test wdyt ?

@iliaal iliaal Jun 26, 2026

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Confirmed, and it's a separate pre-existing UAF (reproduces on base without this hunk). endChildren() re-entering via $this->next() frees the level's sub-iterator and pops the level inside the reentrant call, then the outer frame's zend_iterator_dtor(iterator) at line 432 frees the stale local again. rewind() reentry is already safe: it unwinds to level 0 and the if (object->level > 0) re-check catches it.

So it needs more than reloading object->iterators[object->level].iterator there: the reentrant next() already tore the level down, so the outer frame has to notice and skip the dtor/decrement. I'll fix it in a follow-up with its own test rather than widen this PR.

ZEND_FALLTHROUGH;
case RS_START:
if (iterator->funcs->valid(iterator) == FAILURE) {
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41 changes: 41 additions & 0 deletions ext/spl/tests/recursiveiteratoriterator_rewind_during_next.phpt
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@@ -0,0 +1,41 @@
--TEST--
RecursiveIteratorIterator: rewind() re-entered from an inner next() must not use-after-free
--FILE--
<?php
class Reenter implements RecursiveIterator {
public $data; public $pos = 0; public $rii; public $depth;
public static bool $fired = false;
function __construct(array $d, $depth = 0) { $this->data = $d; $this->depth = $depth; }
function current(): mixed { return $this->data[$this->pos] ?? null; }
function key(): mixed { return $this->pos; }
function next(): void {
$this->pos++;
if ($this->rii && $this->depth === 1 && $this->pos === 1 && !self::$fired) {
self::$fired = true;
$this->rii->rewind();
}
}
function rewind(): void { $this->pos = 0; }
function valid(): bool { return $this->pos < count($this->data); }
function hasChildren(): bool { return is_array($this->current()); }
function getChildren(): RecursiveIterator {
$c = new Reenter($this->current(), $this->depth + 1);
$c->rii = $this->rii;
return $c;
}
}
$root = new Reenter([[10, 11], [20, 21]]);
$rii = new RecursiveIteratorIterator($root, RecursiveIteratorIterator::SELF_FIRST);
$root->rii = $rii;
$seen = [];
foreach ($rii as $v) {
if (is_array($v)) { $v = '[' . implode(',', $v) . ']'; }
$seen[] = $v;
if (count($seen) > 20) { $seen[] = '...'; break; }
}
echo implode(' ', $seen), "\n";
echo "done\n";
?>
--EXPECT--
[10,11] 10 [10,11] 10 11 [20,21] 20 21
done
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