Bug #78010 [Com]: Segmentation fault during GC

Edit report at https://bugs.php.net/bug.php?id=78010&edit=1 ID: 78010 Comment by: grzegorz129 at gmail dot com Reported by: valera dot ymnik at gmail dot com Summary: Segmentation fault during GC Status: Verified Type: Bug Package: Reproducible crash Operating System: Debian 9 && Ubuntu 18.04 PHP Version: 7.3.5 Block user comment: N Private report: N New Comment: I simplified the reproducer and added some comments: <?php //gc_disable(); class foo { public function __construct() { $this->x = $this; for ($i = 0; $i < 898; $i++) { //Will not trigger with <898 $obj = [new stdClass, new stdClass]; //This must have at least 2 elements $this->y[] = $obj; } } } for ($i = 0; $i < 2; ++$i) { //This must run >=2 (increasing the number of elements in the array *2 will not do) $x = []; //This must be reset foreach (array_fill(0, 389, 'x') as &$params) { //Will not trigger <389 $x[] = new foo; } } echo "Completed\n"; Valgring output: https://zerobin.net/?ca2ef1bcab5e1b03#qc85nUSpB0Yp7oK4Bvd1hSOV3B9kybe34XmH6wvZE6o= Previous Comments: ------------------------------------------------------------------------ [2019-07-12 20:50:21] grzegorz129 at gmail dot com Maybe stating the obvious but putting gc_disable() at the beginning of the script makes the code complete. Also tested on 7.4alpha3 - the same result. ------------------------------------------------------------------------ [2019-07-12 18:50:46] nikic@php.net Related To: Bug #78280 ------------------------------------------------------------------------ [2019-07-12 16:11:17] kolja dot zuelsdorf at deinhandy dot de We have this issue under strong suspicion to break one of our core business processes and wonder why it was not addressed in the last bugfix releases. Is there anything we can do to help mitigate the issue? So far we are running said process on an old (7.1) version. Furthermore, I've confirmed that the same thing happens on 7.3.6 and 7.3.7 too. ------------------------------------------------------------------------ [2019-05-14 12:43:51] nikic@php.net First valgrind warning: ==21347== Invalid read of size 4 ==21347== at 0x94623D: zend_gc_collect_cycles (zend_gc.c:1529) ==21347== by 0x9436EA: gc_possible_root_when_full (zend_gc.c:579) ==21347== by 0x943996: gc_possible_root (zend_gc.c:629) ==21347== by 0x970CF4: zend_assign_to_variable (zend_execute.h:146) ==21347== by 0x9E99E5: ZEND_ASSIGN_SPEC_CV_VAR_RETVAL_UNUSED_HANDLER (zend_vm_execute.h:48960) ==21347== by 0x9FBA14: execute_ex (zend_vm_execute.h:65005) ==21347== by 0x9FC649: zend_execute (zend_vm_execute.h:65726) ==21347== by 0x908A98: zend_execute_scripts (zend.c:1661) ==21347== by 0x8518DA: php_execute_script (main.c:2676) ==21347== by 0x9FF646: do_cli (php_cli.c:985) ==21347== by 0xA00965: main (php_cli.c:1375) ==21347== Address 0x2661b414 is 4 bytes inside a block of size 40 free'd ==21347== at 0x4C30D3B: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==21347== by 0x8C7FC4: _efree (zend_alloc.c:2497) ==21347== by 0x96619B: zend_objects_store_del (zend_objects_API.c:198) ==21347== by 0x902E4E: rc_dtor_func (zend_variables.c:57) ==21347== by 0x91C30D: i_zval_ptr_dtor (zend_variables.h:44) ==21347== by 0x921881: zend_array_destroy (zend_hash.c:1589) ==21347== by 0x95DBA1: zend_object_std_dtor (zend_objects.c:53) ==21347== by 0x966137: zend_objects_store_del (zend_objects_API.c:194) ==21347== by 0x902E4E: rc_dtor_func (zend_variables.c:57) ==21347== by 0x91C30D: i_zval_ptr_dtor (zend_variables.h:44) ==21347== by 0x921881: zend_array_destroy (zend_hash.c:1589) ==21347== by 0x902E4E: rc_dtor_func (zend_variables.c:57) ==21347== Block was alloc'd at ==21347== at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==21347== by 0x8C8F07: __zend_malloc (zend_alloc.c:2889) ==21347== by 0x8C7E9C: _emalloc (zend_alloc.c:2483) ==21347== by 0x95E27A: zend_objects_new (zend_objects.c:195) ==21347== by 0x90FFCE: _object_and_properties_init (zend_API.c:1356) ==21347== by 0x9100AE: object_init_ex (zend_API.c:1379) ==21347== by 0x992655: ZEND_NEW_SPEC_CONST_UNUSED_HANDLER (zend_vm_execute.h:9173) ==21347== by 0x9F7273: execute_ex (zend_vm_execute.h:60503) ==21347== by 0x9FC649: zend_execute (zend_vm_execute.h:65726) ==21347== by 0x908A98: zend_execute_scripts (zend.c:1661) ==21347== by 0x8518DA: php_execute_script (main.c:2676) ==21347== by 0x9FF646: do_cli (php_cli.c:985) ------------------------------------------------------------------------ [2019-05-14 12:37:36] valera dot ymnik at gmail dot com Description: ------------ Reproduced on "PHP 7.3.5-1+0~20190503093827.38+stretch~1.gbp60a41b (cli) (built: May 3 2019 09:38:28) ( NTS )" and "PHP 7.3.5-1+ubuntu18.04.1+deb.sury.org+1 (cli) (built: May 3 2019 10:00:24) ( NTS )" Test script: --------------- <?php class Test { private $data; private $values; public function __construct() { $this->data = new stdClass; $this->data->context = $this; $this->values = new stdClass; $this->values->store = []; for ($i = 0; $i < 526; $i++) { $obj = new stdClass; $obj->data = new stdClass; $obj->z = new stdClass; $obj->z->a = new stdClass; $obj->z->b = new stdClass; $this->values->store[] = $obj; } } } $data = [array_fill(0, 400, []), array_fill(0, 400, [])]; foreach ($data as $row_id => $values) { foreach ($values as $id => &$params) { $params["store"] = new Test; } unset($params); } echo "Completed\n"; Expected result: ---------------- Completed Actual result: -------------- Segmentation fault ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=78010&edit=1