Edit report at https://bugs.php.net/bug.php?id=62005&edit=1
ID: 62005
Updated by: larue...@php.net
Reported by: jlee+bug at imvu dot com
Summary: Invalid memory access when incrementally assigning
to a member of a null object
Status: Open
Type: Bug
Package: Scripting Engine problem
Operating System: Ubuntu 10.04.1 LTS
PHP Version: master-Git-2012-05-10 (Git)
-Assigned To:
+Assigned To: laruence
Block user comment: N
Private report: N
New Comment:
I have got a fix, assign to myself.
Previous Comments:
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[2012-05-12 04:05:41] larue...@php.net
in 5.3, I got:
Strict Standards: Creating default object from empty value in /tmp/1.php on
line 3
[Sat May 12 12:05:52 2012] Script: '/tmp/1.php'
/home/huixinchen/opensource/php-5.3/Zend/zend_execute.c(437) : Freeing
0x0324AE08
(32 bytes), script=/tmp/1.php
=== Total 1 memory leaks detected ===
------------------------------------------------------------------------
[2012-05-11 16:47:45] jlee+bug at imvu dot com
Description:
------------
Valgrind reports an invalid memory access in PHP when a script incrementally
assigns to a member of a null object while a user-defined error handler is in
place. This invalid access causes occasional segfaults. It was initially
observed in PHP 5.3, but it was found to still be present when run from vanilla
github source as of 2012-04-30.
I have not been able to fix the bug, but here is what I've discovered so far:
During the incremental assignment, PHP replaces the variable's null value with
an empty object value, while issuing a warning. However, it seems that there
is some problem with updating the references to these values. An invalid
memory access occurs during the return from the function, when the virtual
machine tries to decrement the null value's reference count after it is already
zero (and has been freed). Also, the empty object value does not get its
reference count decremented and therefore gets leaked.
Please see the attached test script and valgrind log.
Test script:
---------------
#!/usr/bin/php
<?
function add_points($player, $points) {
$player->energy += $points;
}
function errorHandler($severity, $message, $filename, $line, $super_globals) { }
set_error_handler('errorHandler');
add_points(NULL, 10);
Expected result:
----------------
I expect no invalid read or write messages in valgrind's output.
Actual result:
--------------
When running under valgrind:
==8441== Memcheck, a memory error detector
==8441== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==8441== Using Valgrind-3.8.0.SVN and LibVEX; rerun with -h for copyright info
==8441== Command: /home/joe/bin/php broken_assignment.php
==8441==
==8441== Invalid read of size 4
==8441== at 0x7FC35C: zend_leave_helper_SPEC (zend.h:391)
==8441== by 0x8042B4: ZEND_RETURN_SPEC_CONST_HANDLER (zend_vm_execute.h:2262)
==8441== by 0x7FB85E: execute (zend_vm_execute.h:410)
==8441== by 0x7BE1C7: zend_execute_scripts (zend.c:1272)
==8441== by 0x7320CB: php_execute_script (main.c:2473)
==8441== by 0x90CD2E: do_cli (php_cli.c:988)
==8441== by 0x90DCD3: main (php_cli.c:1361)
==8441== Address 0x6a12120 is 16 bytes inside a block of size 32 free'd
==8441== at 0x4C2879F: free (vg_replace_malloc.c:427)
==8441== by 0x78842B: _efree (zend_alloc.c:2434)
==8441== by 0x7A8448: _zval_ptr_dtor (zend_execute_API.c:439)
==8441== by 0x7BAFE9: _zval_ptr_dtor_wrapper (zend_variables.c:180)
==8441== by 0x7CF504: zend_hash_clean (zend_hash.c:596)
==8441== by 0x7FC00F: zend_leave_helper_SPEC (zend_vm_execute.h:529)
==8441== by 0x8042B4: ZEND_RETURN_SPEC_CONST_HANDLER (zend_vm_execute.h:2262)
==8441== by 0x7FB85E: execute (zend_vm_execute.h:410)
==8441== by 0x7BE1C7: zend_execute_scripts (zend.c:1272)
==8441== by 0x7320CB: php_execute_script (main.c:2473)
==8441== by 0x90CD2E: do_cli (php_cli.c:988)
==8441== by 0x90DCD3: main (php_cli.c:1361)
[5 other invalid read/writes omitted]
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