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Keep dumped objects alive across __debugInfo() and property hooks #22471

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59 changes: 59 additions & 0 deletions ext/standard/tests/general_functions/gh21024.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,59 @@
--TEST--
GH-21024 (UAF in var_dump()/debug_zval_dump()/var_export() when a callback frees the dumped object)
--FILE--
<?php
class Bar {
public function __debugInfo(): array {
echo $undefined;
return ['ok' => 1];
}
}
class Hooked {
public $x { get { echo $undefined; return 1; } }
}

$a = [new Bar];
$ra = &$a[0];
set_error_handler(function () use (&$ra) { $ra = null; });
var_dump($a);
restore_error_handler();

$b = [new Bar];
$rb = &$b[0];
set_error_handler(function () use (&$rb) { $rb = null; });
debug_zval_dump($b);
restore_error_handler();

$c = [new Hooked];
$rc = &$c[0];
set_error_handler(function () use (&$rc) { $rc = null; });
var_export($c);
echo "\n";
restore_error_handler();

echo "survived\n";
?>
--EXPECTF--
array(1) {
[0]=>
&object(Bar)#%d (1) {
["ok"]=>
int(1)
}
}
array(1) packed refcount(%d){
[0]=>
reference refcount(%d) {
object(Bar)#%d (1) refcount(%d){
["ok"]=>
int(1)
}
}
}
array (
0 =>
\Hooked::__set_state(array(
'x' => 1,
)),
)
survived
41 changes: 30 additions & 11 deletions ext/standard/var.c
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Original file line number Diff line number Diff line change
Expand Up @@ -179,15 +179,20 @@ PHPAPI void php_var_dump(zval *struc, int level) /* {{{ */
}
ZEND_GUARD_OR_GC_PROTECT_RECURSION(guard, DEBUG, zobj);

/* zend_get_properties_for() may invoke __debugInfo(), which can run
* a user error handler that drops the last reference to the object.
* Keep it alive and use the captured zobj rather than re-reading
* struc, whose zval the handler may also have overwritten. */
GC_ADDREF(zobj);
myht = zend_get_properties_for(struc, ZEND_PROP_PURPOSE_DEBUG);
if (ce->ce_flags & ZEND_ACC_ENUM) {
zval *case_name_zval = zend_enum_fetch_case_name(Z_OBJ_P(struc));
zval *case_name_zval = zend_enum_fetch_case_name(zobj);
php_printf("%senum(%s::%s) (%d) {\n", COMMON, ZSTR_VAL(ce->name), Z_STRVAL_P(case_name_zval), myht ? zend_array_count(myht) : 0);
} else {
class_name = Z_OBJ_HANDLER_P(struc, get_class_name)(Z_OBJ_P(struc));
const char *prefix = php_var_dump_object_prefix(Z_OBJ_P(struc));
class_name = zobj->handlers->get_class_name(zobj);
const char *prefix = php_var_dump_object_prefix(zobj);

php_printf("%s%sobject(%s)#%d (%d) {\n", COMMON, prefix, ZSTR_VAL(class_name), Z_OBJ_HANDLE_P(struc), myht ? zend_array_count(myht) : 0);
php_printf("%s%sobject(%s)#%d (%d) {\n", COMMON, prefix, ZSTR_VAL(class_name), zobj->handle, myht ? zend_array_count(myht) : 0);
zend_string_release_ex(class_name, 0);
}

Expand All @@ -202,7 +207,7 @@ PHPAPI void php_var_dump(zval *struc, int level) /* {{{ */
if (Z_TYPE_P(val) == IS_INDIRECT) {
val = Z_INDIRECT_P(val);
if (key) {
prop_info = zend_get_typed_property_info_for_slot(Z_OBJ_P(struc), val);
prop_info = zend_get_typed_property_info_for_slot(zobj, val);
}
}

Expand All @@ -217,6 +222,7 @@ PHPAPI void php_var_dump(zval *struc, int level) /* {{{ */
}
PUTS("}\n");
ZEND_GUARD_OR_GC_UNPROTECT_RECURSION(guard, DEBUG, zobj);
OBJ_RELEASE(zobj);
break;
}
case IS_RESOURCE: {
Expand Down Expand Up @@ -382,11 +388,16 @@ PHPAPI void php_debug_zval_dump(zval *struc, int level) /* {{{ */
}
ZEND_GUARD_OR_GC_PROTECT_RECURSION(guard, DEBUG, zobj);

/* zend_get_properties_for() may invoke __debugInfo(), which can run a
* user error handler that drops the last reference to the object. Keep
* it alive across the call and report the refcount excluding this
* temporary reference. */
GC_ADDREF(zobj);
myht = zend_get_properties_for(struc, ZEND_PROP_PURPOSE_DEBUG);
class_name = Z_OBJ_HANDLER_P(struc, get_class_name)(Z_OBJ_P(struc));
const char *prefix = php_var_dump_object_prefix(Z_OBJ_P(struc));
class_name = zobj->handlers->get_class_name(zobj);
const char *prefix = php_var_dump_object_prefix(zobj);

php_printf("%sobject(%s)#%d (%d) refcount(%u){\n", prefix, ZSTR_VAL(class_name), Z_OBJ_HANDLE_P(struc), myht ? zend_array_count(myht) : 0, Z_REFCOUNT_P(struc));
php_printf("%sobject(%s)#%d (%d) refcount(%u){\n", prefix, ZSTR_VAL(class_name), zobj->handle, myht ? zend_array_count(myht) : 0, GC_REFCOUNT(zobj) - 1);
zend_string_release_ex(class_name, 0);
if (myht) {
ZEND_HASH_FOREACH_KEY_VAL(myht, index, key, val) {
Expand All @@ -395,7 +406,7 @@ PHPAPI void php_debug_zval_dump(zval *struc, int level) /* {{{ */
if (Z_TYPE_P(val) == IS_INDIRECT) {
val = Z_INDIRECT_P(val);
if (key) {
prop_info = zend_get_typed_property_info_for_slot(Z_OBJ_P(struc), val);
prop_info = zend_get_typed_property_info_for_slot(zobj, val);
}
}

Expand All @@ -410,6 +421,7 @@ PHPAPI void php_debug_zval_dump(zval *struc, int level) /* {{{ */
}
PUTS("}\n");
ZEND_GUARD_OR_GC_UNPROTECT_RECURSION(guard, DEBUG, zobj);
OBJ_RELEASE(zobj);
break;
}
case IS_RESOURCE: {
Expand Down Expand Up @@ -608,13 +620,19 @@ PHPAPI zend_result php_var_export_ex(zval *struc, int level, smart_str *buf) /*
return SUCCESS;
}
ZEND_GUARD_OR_GC_PROTECT_RECURSION(guard, EXPORT, zobj);
/* zend_get_properties_for() and the property hooks read below may
* run userland (a get hook, a custom get_properties) that drops the
* last reference to the object. Keep it alive and use the captured
* zobj rather than re-reading struc, which the handler may also have
* overwritten. */
GC_ADDREF(zobj);
myht = zend_get_properties_for(struc, ZEND_PROP_PURPOSE_VAR_EXPORT);
if (level > 1) {
smart_str_appendc(buf, '\n');
buffer_append_spaces(buf, level - 1);
}

zend_class_entry *ce = Z_OBJCE_P(struc);
zend_class_entry *ce = zobj->ce;
bool is_enum = ce->ce_flags & ZEND_ACC_ENUM;

/* stdClass has no __set_state method, but can be casted to */
Expand All @@ -624,7 +642,6 @@ PHPAPI zend_result php_var_export_ex(zval *struc, int level, smart_str *buf) /*
smart_str_appendc(buf, '\\');
smart_str_append(buf, ce->name);
if (is_enum) {
zend_object *zobj = Z_OBJ_P(struc);
zval *case_name_zval = zend_enum_fetch_case_name(zobj);
smart_str_appendl(buf, "::", 2);
smart_str_append(buf, Z_STR_P(case_name_zval));
Expand All @@ -650,6 +667,7 @@ PHPAPI zend_result php_var_export_ex(zval *struc, int level, smart_str *buf) /*
if (EG(exception)) {
ZEND_GUARD_OR_GC_UNPROTECT_RECURSION(guard, EXPORT, zobj);
zend_release_properties(myht);
OBJ_RELEASE(zobj);
return FAILURE;
}
}
Expand All @@ -662,6 +680,7 @@ PHPAPI zend_result php_var_export_ex(zval *struc, int level, smart_str *buf) /*
zend_release_properties(myht);
}
ZEND_GUARD_OR_GC_UNPROTECT_RECURSION(guard, EXPORT, zobj);
OBJ_RELEASE(zobj);
if (level > 1 && !is_enum) {
buffer_append_spaces(buf, level - 1);
}
Expand Down
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