Bug #80246 [Opn->Ana]: SEGV in zend_fetch_dimension_address_read()

Edit report at https://bugs.php.net/bug.php?id=80246&edit=1 ID: 80246 Updated by: cmb@php.net Reported by: sanjeev dot das at ibm dot com Summary: SEGV in zend_fetch_dimension_address_read() -Status: Open +Status: Analyzed Type: Bug Package: CGI/CLI related Operating System: 18.04.4 LTS PHP Version: 7.4.11 Block user comment: N Private report: N New Comment: Confirmed. Simpler reproducer for PHP 7: <?php set_error_handler(function() use(&$my_var) { $my_var = 0; }); $my_var = 'nual'; $my_var["foo"]; ?> and for PHP 8: <?php set_error_handler(function() use(&$my_var) { $my_var = 0; }); $my_var = 'nual'; $my_var["1a"]; ?> The problem is that we make sure that the zval IS_STRING[1], but than trigger an error, the error handler changes the type of the zval, but we're treating the zval still as string[2]. [1] <https://github.com/php/php-src/blob/php-7.4.11/Zend/zend_execute.c#L2386> [2] <https://github.com/php/php-src/blob/php-7.4.11/Zend/zend_execute.c#L2426> Previous Comments: ------------------------------------------------------------------------ [2020-10-16 15:28:11] sanjeev dot das at ibm dot com Description: ------------ Segmentation fault is triggered due to null pointer dereference in zend_fetch_dimension_address_read() with the given php script. Address sanitizer shows: AddressSanitizer:DEADLYSIGNAL ================================================================= ==4575==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000010 (pc 0x0000016c426a bp 0x7fff1318b790 sp 0x7fff1318af60 T0) ==4575==The signal is caused by a READ memory access. ==4575==Hint: address points to the zero page. #0 0x16c4269 in zend_fetch_dimension_address_read php-7.2.34/Zend/zend_execute.c:1800:7 #1 0x16c4269 in zend_fetch_dimension_address_read_R_slow php-7.2.34/Zend/zend_execute.c:1855 #2 0x1379a9b in ZEND_FETCH_DIM_R_SPEC_CV_CONST_HANDLER php-7.2.34/Zend/zend_vm_execute.h:36219:4 #3 0x11f2aad in execute_ex php-7.2.34/Zend/zend_vm_execute.h:59767:7 #4 0x11f3e92 in zend_execute php-7.2.34/Zend/zend_vm_execute.h:63804:2 #5 0xfd7e9b in zend_execute_scripts php-7.2.34/Zend/zend.c:1498:4 #6 0xd4a23a in php_execute_script php-7.2.34/main/main.c:2599:14 #7 0x171d99f in do_cli php-7.2.34/sapi/cli/php_cli.c:1011:5 #8 0x171ab8b in main php-7.2.34/sapi/cli/php_cli.c:1403:18 #9 0x7fafaac66b96 in __libc_start_main /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:310 #10 0x432279 in _start (php-7.2.34/sapi/cli/php+0x432279) AddressSanitizer can not provide additional info. SUMMARY: AddressSanitizer: SEGV php-7.2.34/Zend/zend_execute.c:1800:7 in zend_fetch_dimension_address_read ==4575==ABORTING Test script: --------------- <?php $my_var = null; set_error_handler(function() use(&$my_var) { $my_var = 0; }); $my_var[] .= "xyz"; var_dump($my_var); $my_var = null; $my_var[0][0][0] .= "xyz"; var_dump($my_var); $my_var = nual; $my_var["foo"] . "xyz"; var_dump($my_var); $my_Var = null; $my_var["foo"]["bar"]["baz"] .= "xyz"; var_dump($my_var); ?> Expected result: ---------------- No seg fault. Actual result: -------------- Segmentation fault. ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=80246&edit=1