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Guard var_dump()/debug_zval_dump() against native stack overflow #22871

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Guard var_dump()/debug_zval_dump() against native stack overflow #22871

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40 changes: 40 additions & 0 deletions ext/standard/tests/general_functions/var_dump_stack_limit.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,40 @@
--TEST--
var_dump() and debug_zval_dump() guard against native stack overflow on deep structures
--SKIPIF--
<?php
if (ini_get('zend.max_allowed_stack_size') === false) {
die('skip No stack limit support');
}
if (getenv('SKIP_ASAN')) {
die('skip ASAN needs different stack limit setting due to more stack space usage');
}
?>
--INI--
zend.max_allowed_stack_size=256K
--FILE--
<?php
$a = [];
for ($i = 0; $i < 50000; $i++) { $a = [$a]; }

class Node { public $next; }
$firstNode = new Node();
$node = $firstNode;
for ($i = 0; $i < 50000; $i++) { $newNode = new Node(); $node->next = $newNode; $node = $newNode; }

function guarded(callable $fn): string {
ob_start();
$fn();
return str_contains(ob_get_clean(), 'nesting level too deep') ? "guarded\n" : "NO GUARD\n";
}

echo 'var_dump array: ', guarded(fn() => var_dump($a));
echo 'debug_zval_dump array: ', guarded(fn() => debug_zval_dump($a));
echo 'debug_zval_dump object: ', guarded(fn() => debug_zval_dump($firstNode));

while (is_array($a) && isset($a[0])) { $a = $a[0]; }
while ($next = $firstNode->next) { $firstNode->next = $next->next; }
?>
--EXPECT--
var_dump array: guarded
debug_zval_dump array: guarded
debug_zval_dump object: guarded
18 changes: 18 additions & 0 deletions ext/standard/var.c
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,12 @@ struct php_serialize_data {

static void php_array_element_dump(zval *zv, zend_ulong index, zend_string *key, int level) /* {{{ */
{
#ifdef ZEND_CHECK_STACK_LIMIT
if (UNEXPECTED(zend_call_stack_overflowed(EG(stack_limit)))) {
php_printf("%*cnesting level too deep", level + 1, ' ');
return;
}
#endif
if (key == NULL) { /* numeric key */
php_printf("%*c[" ZEND_LONG_FMT "]=>\n", level + 1, ' ', index);
} else { /* string key */
Expand Down Expand Up @@ -255,6 +261,12 @@ PHP_FUNCTION(var_dump)

static void zval_array_element_dump(zval *zv, zend_ulong index, zend_string *key, int level) /* {{{ */
{
#ifdef ZEND_CHECK_STACK_LIMIT
if (UNEXPECTED(zend_call_stack_overflowed(EG(stack_limit)))) {
php_printf("%*cnesting level too deep", level + 1, ' ');
return;
}
#endif
if (key == NULL) { /* numeric key */
php_printf("%*c[" ZEND_LONG_FMT "]=>\n", level + 1, ' ', index);
} else { /* string key */
Expand All @@ -270,6 +282,12 @@ static void zval_object_property_dump(zend_property_info *prop_info, zval *zv, z
{
const char *prop_name, *class_name;

#ifdef ZEND_CHECK_STACK_LIMIT
if (UNEXPECTED(zend_call_stack_overflowed(EG(stack_limit)))) {
php_printf("%*cnesting level too deep", level + 1, ' ');
return;
}
#endif
if (key == NULL) { /* numeric key */
php_printf("%*c[" ZEND_LONG_FMT "]=>\n", level + 1, ' ', index);
} else { /* string key */
Expand Down
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