php.net |  support |  documentation |  report a bug |  advanced search |  search howto |  statistics |  random bug |  login

go to bug id or search bugs for

Bug #78589 Memory leak with GC + __destruct()
Submitted: 2019-09-23 10:20 UTC Modified: 2019-09-23 10:35 UTC
From: nikic@php.net Assigned:
Status: Closed Package: Scripting Engine problem
PHP Version: 7.4Git-2019-09-23 (Git) OS:
Private report: No CVE-ID: None
View Developer Edit
Anyone can comment on a bug. Have a simpler test case? Does it work for you on a different platform? Let us know!
Just going to say 'Me too!'? Don't clutter the database with that please !
Your email address:
MUST BE VALID
Solve the problem:
2 + 30 = ?
Subscribe to this entry?

 
 [2019-09-23 10:20 UTC] nikic@php.net 
Description:
------------
This is reduced from an OSS-Fuzz testcase involving unserialize(), but turns out to be some kind of generic GC bug. It is related to the changes to __destruct() handling in 7.4.

Test script:
---------------
class Test {
    public function __destruct() {} 
} 
 
$test = new Test; 
$test->foo = [&$test->foo];
$ary = [&$ary, $test];
unset($ary, $test);
gc_collect_cycles();

Actual result:
--------------
[Mon Sep 23 12:17:48 2019]  Script:  '/home/nikic/php-src-fuzz/t009.php'
Zend/zend_vm_execute.h(27609) :  Freeing 0x00007f8220201940 (32 bytes), script=/home/nikic/php-src-fuzz/t009.php
[Mon Sep 23 12:17:48 2019]  Script:  '/home/nikic/php-src-fuzz/t009.php'
/home/nikic/php-src-fuzz/Zend/zend_hash.c(256) :  Freeing 0x00007f82202588a0 (56 bytes), script=/home/nikic/php-src-fuzz/t009.php
[Mon Sep 23 12:17:48 2019]  Script:  '/home/nikic/php-src-fuzz/t009.php'
/home/nikic/php-src-fuzz/Zend/zend_hash.c(131) :  Freeing 0x00007f822025c280 (264 bytes), script=/home/nikic/php-src-fuzz/t009.php
=== Total 3 memory leaks detected ===

Patches

Pull Requests

History

AllCommentsChangesGit/SVN commitsRelated reports
 [2019-09-23 10:35 UTC] nikic@php.net
-Status: Open +Status: Analyzed
 [2019-09-23 10:35 UTC] nikic@php.net 
The problem seems to be that we set gc_protected=1 during the zval destruction phase. However, in this case the destruction of the object wants to add the inner array to the GC buffer. (It was previously removed as nested data of the __destruct object.)
 [2019-09-24 10:19 UTC] nikic@php.net 
Automatic comment on behalf of nikita.ppv@gmail.com
Revision: http://git.php.net/?p=php-src.git;a=commit;h=73115ef8730cc2466fdb039acb6b9463bc08808a
Log: Fixed bug #78589
 [2019-09-24 10:19 UTC] nikic@php.net
-Status: Analyzed +Status: Closed
 
PHP Copyright © 2001-2025 The PHP Group
All rights reserved. 		Last updated: Sat Oct 25 17:00:01 2025 UTC