Edit report at http://bugs.php.net/bug.php?id=51768&edit=1
ID: 51768
Updated by: cataphr...@php.net
Reported by: cataphr...@php.net
Summary: Fallback to read_property causes subsequent crash
Status: Open
Type: Bug
Package: Reproducible crash
Operating System: Windows
PHP Version: 5.3.2
New Comment:
Apparently, not to break backwards compatibility,
$a = &$obj->prop
should not accept only references, like read_dimension. The current
behavior is to make a reference if the refcount is one
(SEPARATE_ZVAL_TO_MAKE_IS_REF).
Anyway, in the test script the refcount is 2.
Previous Comments:
------------------------------------------------------------------------
[2010-05-08 16:01:21] cataphr...@php.net
I got it backwards in the expected behavior and a bit in the
description.
What should give a fatal error is something like:
$obj->prop = &$a;
I said that
$a = &$obj['prop']
emits an error. It doesn't. It emits a notice if the zval* returned by
the read_dimension handler does not return a reference (Indirect
modification of overloaded element).
In fact both read_dimension and read_property without
get_property_ptr_ptr behave correctly in the $obj->prop = &$a by
emitting a fatal error: (Cannot assign by reference to overloaded
object)
The expected behavior should then be either mimic read_dimension (accept
only references) or just throw an error.
------------------------------------------------------------------------
[2010-05-08 04:14:05] cataphr...@php.net
Description:
------------
When the get_property_ptr_ptr handler is omitted,
zend_fetch_property_address falls back to read_property, but then the
behavior in cases such as
$a = &$obj->prop;
deviates from that of
$a = &$obj['prop'];
which properly emits an error.
The final result is a crash.
Test script:
---------------
exttest.h:
#ifndef PHP_EXTTEST_H
# define PHP_EXTTEST_H
# ifdef HAVE_CONFIG_H
# include<config.h>
# endif
# include<php.h>
extern zend_module_entry exttest_module_entry;
#define phpext_exttest_ptr &exttest_module_entry
#endif
exttest.c:
#include "exttest.h"
static zend_object_handlers object_handlers;
static zend_object_value ce_create_object(zend_class_entry *class_type
TSRMLS_DC)
{
zend_object_value zov;
zend_object *zobj;
zobj = emalloc(sizeof *zobj);
zend_object_std_init(zobj, class_type TSRMLS_CC);
zend_hash_copy(zobj->properties, &(class_type->default_properties),
(copy_ctor_func_t) zval_add_ref, NULL, sizeof(zval*));
zov.handle = zend_objects_store_put(zobj,
(zend_objects_store_dtor_t) zend_objects_destroy_object,
(zend_objects_free_object_storage_t)
zend_objects_free_object_storage,
NULL TSRMLS_CC);
zov.handlers = &object_handlers;
return zov;
}
ZEND_MODULE_STARTUP_D(exttest)
{
zend_class_entry ce;
zend_class_entry *ce_ptr;
zval *property;
ALLOC_PERMANENT_ZVAL(property);
INIT_ZVAL(*property);
Z_TYPE_P(property) = IS_LONG;
Z_LVAL_P(property) = 20l;
memcpy(&object_handlers, zend_get_std_object_handlers(),
sizeof object_handlers);
object_handlers.get_property_ptr_ptr = NULL;
INIT_CLASS_ENTRY(ce, "TestClass", NULL);
ce_ptr = zend_register_internal_class(&ce TSRMLS_CC);
ce_ptr->create_object = ce_create_object;
zend_declare_property_ex(ce_ptr, "prop", 4, property,
ZEND_ACC_PUBLIC,
NULL, 0 TSRMLS_CC);
}
zend_module_entry exttest_module_entry = {
STANDARD_MODULE_HEADER,
"exttest",
NULL, /* Functions */
ZEND_MODULE_STARTUP_N(exttest) , /* MINIT */
NULL, /* MSHUTDOWN */
NULL, /* RINIT */
NULL, /* RSHUTDOWN */
NULL, /* MINFO */
NO_VERSION_YET,
STANDARD_MODULE_PROPERTIES
};
ZEND_GET_MODULE(exttest)
config.m4:
PHP_ARG_ENABLE(exttest,
[Whether to enable the "exttest" extension],
[ enable-exttest Enable "exttest" extension support])
if test $PHP_EXTTEST != "no"; then
PHP_SUBST(EXTTEST_SHARED_LIBADD)
PHP_NEW_EXTENSION(exttest, exttest.c, $ext_shared)
fi
test.php:
<?php
$obj = new TestClass();
debug_zval_dump($obj);
$a = &$obj->prop;
debug_zval_dump($obj);
debug_zval_dump(&$a);
$a = 40;
debug_zval_dump($obj);
debug_zval_dump(&$a);
unset($a);
debug_zval_dump($obj);
Expected result:
----------------
Expected an error saying the operation is not permitted (like when
attempting $a = &obj['index'] where there's no get_property_ptr_ptr
equivalent).
Actual result:
--------------
When thre's get_property_ptr_ptr:
object(TestClass)#1 (1) refcount(2){
["prop"]=>
long(20) refcount(2)
}
object(TestClass)#1 (1) refcount(2){
["prop"]=>
&long(20) refcount(2)
}
&long(20) refcount(3)
object(TestClass)#1 (1) refcount(2){
["prop"]=>
&long(40) refcount(2)
}
&long(40) refcount(3)
object(TestClass)#1 (1) refcount(2){
["prop"]=>
long(40) refcount(1)
}
When there's no get_property_ptr_ptr, zend_fetch_property_address falls
back to read_propert. Something happens afterwards that provokes the
crash.
object(TestClass)#1 (1) refcount(2){
["prop"]=>
long(20) refcount(2)
}
object(TestClass)#1 (1) refcount(2){
["prop"]=>
long(20) refcount(1)
}
&long(20) refcount(3)
object(TestClass)#1 (1) refcount(2){
["prop"]=>
long(20) refcount(1)
}
&long(40) refcount(3)
object(TestClass)#1 (1) refcount(2){
["prop"]=>
long(20) refcount(1)
}
Segmentation fault
#0 0x081d60ae in zend_mm_check_ptr (heap=0x83881b8, ptr=0x840ca90,
silent=1,
__zend_filename=0x83633a0
"/home/glopes/php/php-5.3.2/Zend/zend_variables.c", __zend_lineno=178,
__zend_orig_filename=0x83621b8
"/home/glopes/php/php-5.3.2/Zend/zend_execute_API.c",
__zend_orig_lineno=440) at
/home/glopes/php/php-5.3.2/Zend/zend_alloc.c:1347
#1 0x081d768d in _zend_mm_free_int (heap=0x83881b8, p=0x840ca90,
__zend_filename=0x83633a0
"/home/glopes/php/php-5.3.2/Zend/zend_variables.c", __zend_lineno=178,
__zend_orig_filename=0x83621b8
"/home/glopes/php/php-5.3.2/Zend/zend_execute_API.c",
__zend_orig_lineno=440) at
/home/glopes/php/php-5.3.2/Zend/zend_alloc.c:1983
#2 0x081d86bb in _efree (ptr=0x840ca90,
__zend_filename=0x83633a0
"/home/glopes/php/php-5.3.2/Zend/zend_variables.c", __zend_lineno=178,
__zend_orig_filename=0x83621b8
"/home/glopes/php/php-5.3.2/Zend/zend_execute_API.c",
__zend_orig_lineno=440) at
/home/glopes/php/php-5.3.2/Zend/zend_alloc.c:2351
#3 0x081e9944 in _zval_ptr_dtor (zval_ptr=0x841d584,
__zend_filename=0x83633a0
"/home/glopes/php/php-5.3.2/Zend/zend_variables.c", __zend_lineno=178)
at /home/glopes/php/php-5.3.2/Zend/zend_execute_API.c:440
#4 0x081f7ca8 in _zval_ptr_dtor_wrapper (zval_ptr=0x841d584)
at /home/glopes/php/php-5.3.2/Zend/zend_variables.c:178
#5 0x08207cf7 in zend_hash_destroy (ht=0x841d520) at
/home/glopes/php/php-5.3.2/Zend/zend_hash.c:526
#6 0x0821d64d in zend_object_std_dtor (object=0x841ccf8)
at /home/glopes/php/php-5.3.2/Zend/zend_objects.c:45
#7 0x0821d9a9 in zend_objects_free_object_storage (object=0x841ccf8)
at /home/glopes/php/php-5.3.2/Zend/zend_objects.c:114
#8 0x0822252b in zend_objects_store_del_ref_by_handle_ex (handle=1,
handlers=0xb7f1bd60)
at /home/glopes/php/php-5.3.2/Zend/zend_objects_API.c:220
#9 0x08222320 in zend_objects_store_del_ref (zobject=0x841c45c)
at /home/glopes/php/php-5.3.2/Zend/zend_objects_API.c:172
#10 0x081f7917 in _zval_dtor_func (zvalue=0x841c45c,
__zend_filename=0x83621b8
"/home/glopes/php/php-5.3.2/Zend/zend_execute_API.c",
__zend_lineno=439)
at /home/glopes/php/php-5.3.2/Zend/zend_variables.c:52
#11 0x081e96cf in _zval_dtor (zvalue=0x841c45c,
__zend_filename=0x83621b8
"/home/glopes/php/php-5.3.2/Zend/zend_execute_API.c",
__zend_lineno=439)
at /home/glopes/php/php-5.3.2/Zend/zend_variables.h:35
#12 0x081e9919 in _zval_ptr_dtor (zval_ptr=0x841d5d8,
__zend_filename=0x83633a0
"/home/glopes/php/php-5.3.2/Zend/zend_variables.c", __zend_lineno=178)
at /home/glopes/php/php-5.3.2/Zend/zend_execute_API.c:439
#13 0x081f7ca8 in _zval_ptr_dtor_wrapper (zval_ptr=0x841d5d8)
at /home/glopes/php/php-5.3.2/Zend/zend_variables.c:178
#14 0x0820806e in zend_hash_apply_deleter (ht=0x83879d0, p=0x841d5cc)
at /home/glopes/php/php-5.3.2/Zend/zend_hash.c:611
#15 0x08208596 in zend_hash_reverse_apply (ht=0x83879d0,
apply_func=0x81e91bd <zval_call_destructor>)
at /home/glopes/php/php-5.3.2/Zend/zend_hash.c:760
#16 0x081e924a in shutdown_destructors () at
/home/glopes/php/php-5.3.2/Zend/zend_execute_API.c:226
#17 0x081f943c in zend_call_destructors () at
/home/glopes/php/php-5.3.2/Zend/zend.c:874
#18 0x08190427 in php_request_shutdown (dummy=0x0) at
/home/glopes/php/php-5.3.2/main/main.c:1587
#19 0x082c0086 in main (argc=2, argv=0xbfffe674) at
/home/glopes/php/php-5.3.2/sapi/cli/php_cli.c:1373
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/bug.php?id=51768&edit=1
