Description:
------------
Fuzzing PHP 5.6.25 x64 w/ American Fuzzy Lop and ASAN.

Test script:
---------------
<?php class foo{function __wakeup(){$this->__0=0/error_log('');}function _(){(y());}}var_dump(unserialize('a:2:{i:0;O:3:"foo":1:0s:3:"__0";R:1;}'));

Expected result:
----------------
No crash.

Actual result:
--------------
ASAN:SIGSEGV
=================================================================
==2814==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x0000018edcab sp 0x7ffde9624850 bp 0x7fea62c2ed20 T0)
    #0 0x18edcaa in _zend_hash_index_update_or_next_insert /root/php-5.6.25/Zend/zend_hash.c:401
    #1 0x44306d in process_nested_data /root/php-5.6.25/ext/standard/var_unserializer.c:336
    #2 0x15203d4 in php_var_unserialize /root/php-5.6.25/ext/standard/var_unserializer.c:841
    #3 0x14c9656 in zif_unserialize /root/php-5.6.25/ext/standard/var.c:964
    #4 0x1e551b4 in zend_do_fcall_common_helper_SPEC /root/php-5.6.25/Zend/zend_vm_execute.h:558
    #5 0x1a2c75b in execute_ex /root/php-5.6.25/Zend/zend_vm_execute.h:363
    #6 0x1897c68 in zend_execute_scripts /root/php-5.6.25/Zend/zend.c:1341
    #7 0x15d04ef in php_execute_script /root/php-5.6.25/main/main.c:2613
    #8 0x1e5ede7 in do_cli /root/php-5.6.25/sapi/cli/php_cli.c:994
    #9 0x4565d0 in main /root/php-5.6.25/sapi/cli/php_cli.c:1378
    #10 0x7fea60753b44 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b44)
    #11 0x45741e (/root/php-5.6.25/sapi/cli/php+0x45741e)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /root/php-5.6.25/Zend/zend_hash.c:401 _zend_hash_index_update_or_next_insert
==2814==ABORTING