Use after free in SplFixedArray

[chibinz]

Description

The following code:

<?php

class C {
    function __destruct() {
        global $arr;
        $arr->setSize(0);
    }
}

$arr = new SplFixedArray(2);
$arr[0] = new C;
unset($arr[0]);

Resulted in this output:

==1479422==ERROR: AddressSanitizer: heap-use-after-free on address 0x604000045d90 at pc 0x560b20d53d29 bp 0x7ffc0a25d2f0 sp 0x7ffc0a25d2e8
READ of size 4 at 0x604000045d90 thread T0
    #0 0x560b20d53d28 in zend_gc_delref /tmp/php-asan/Zend/zend_types.h:1346:2
    #1 0x560b20d54e5b in zend_objects_store_del /tmp/php-asan/Zend/zend_objects_API.c:180:4
    #2 0x560b20dbbb66 in rc_dtor_func /tmp/php-asan/Zend/zend_variables.c:57:2
    #3 0x560b20dbbc54 in i_zval_ptr_dtor /tmp/php-asan/Zend/zend_variables.h:45:4
    #4 0x560b20dbbba4 in zval_ptr_dtor /tmp/php-asan/Zend/zend_variables.c:84:2
    #5 0x560b2023d0fb in spl_fixedarray_object_unset_dimension_helper /tmp/php-asan/ext/spl/spl_fixedarray.c:462:3
    #6 0x560b2023efa6 in spl_fixedarray_object_unset_dimension /tmp/php-asan/ext/spl/spl_fixedarray.c:475:2
    #7 0x560b20abcc6d in ZEND_UNSET_DIM_SPEC_CV_CONST_HANDLER /tmp/php-asan/Zend/zend_vm_execute.h:45268:4
    #8 0x560b209a602d in execute_ex /tmp/php-asan/Zend/zend_vm_execute.h:58565:7
    #9 0x560b209a6857 in zend_execute /tmp/php-asan/Zend/zend_vm_execute.h:64217:2
    #10 0x560b20dda9d0 in zend_execute_script /tmp/php-asan/Zend/zend.c:1928:3
    #11 0x560b205f961b in php_execute_script_ex /tmp/php-asan/main/main.c:2574:13
    #12 0x560b205f9b18 in php_execute_script /tmp/php-asan/main/main.c:2614:9
    #13 0x560b20de2479 in do_cli /tmp/php-asan/sapi/cli/php_cli.c:935:5
    #14 0x560b20ddf49c in main /tmp/php-asan/sapi/cli/php_cli.c:1310:18
    #15 0x7efce7a29d8f  (/lib/x86_64-linux-gnu/libc.so.6+0x29d8f) (BuildId: 490fef8403240c91833978d494d39e537409b92e)
    #16 0x7efce7a29e3f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e3f) (BuildId: 490fef8403240c91833978d494d39e537409b92e)
    #17 0x560b1f802dc4 in _start (/workspaces/TriFuzz/targets/php-asan/bin/php+0x402dc4)

0x604000045d90 is located 0 bytes inside of 40-byte region [0x604000045d90,0x604000045db8)
freed by thread T0 here:
    #0 0x560b1f8876e2 in free /opt/llvm-15-build/llvm-15.x/final/llvm-project/compiler-rt/lib/asan/asan_malloc_linux.cpp:52:3
    #1 0x560b20836103 in __zend_free /tmp/php-asan/Zend/zend_alloc.c:3308:2
    #2 0x560b20839fd4 in _efree /tmp/php-asan/Zend/zend_alloc.c:2747:3
    #3 0x560b20d5530a in zend_objects_store_del /tmp/php-asan/Zend/zend_objects_API.c:198:3
    #4 0x560b20d57456 in zend_object_release /tmp/php-asan/Zend/zend_objects_API.h:77:3
    #5 0x560b20d5722f in zend_objects_destroy_object /tmp/php-asan/Zend/zend_objects.c:204:3
    #6 0x560b20d54e52 in zend_objects_store_del /tmp/php-asan/Zend/zend_objects_API.c:179:4
    #7 0x560b20dbbb66 in rc_dtor_func /tmp/php-asan/Zend/zend_variables.c:57:2
    #8 0x560b20dbbc54 in i_zval_ptr_dtor /tmp/php-asan/Zend/zend_variables.h:45:4
    #9 0x560b20dbbba4 in zval_ptr_dtor /tmp/php-asan/Zend/zend_variables.c:84:2
    #10 0x560b2023d0fb in spl_fixedarray_object_unset_dimension_helper /tmp/php-asan/ext/spl/spl_fixedarray.c:462:3
    #11 0x560b2023efa6 in spl_fixedarray_object_unset_dimension /tmp/php-asan/ext/spl/spl_fixedarray.c:475:2
    #12 0x560b20abcc6d in ZEND_UNSET_DIM_SPEC_CV_CONST_HANDLER /tmp/php-asan/Zend/zend_vm_execute.h:45268:4
    #13 0x560b209a602d in execute_ex /tmp/php-asan/Zend/zend_vm_execute.h:58565:7
    #14 0x560b209a6857 in zend_execute /tmp/php-asan/Zend/zend_vm_execute.h:64217:2
    #15 0x560b20dda9d0 in zend_execute_script /tmp/php-asan/Zend/zend.c:1928:3
    #16 0x560b205f961b in php_execute_script_ex /tmp/php-asan/main/main.c:2574:13
    #17 0x560b205f9b18 in php_execute_script /tmp/php-asan/main/main.c:2614:9
    #18 0x560b20de2479 in do_cli /tmp/php-asan/sapi/cli/php_cli.c:935:5
    #19 0x560b20ddf49c in main /tmp/php-asan/sapi/cli/php_cli.c:1310:18
    #20 0x7efce7a29d8f  (/lib/x86_64-linux-gnu/libc.so.6+0x29d8f) (BuildId: 490fef8403240c91833978d494d39e537409b92e)

previously allocated by thread T0 here:
    #0 0x560b1f88798e in malloc /opt/llvm-15-build/llvm-15.x/final/llvm-project/compiler-rt/lib/asan/asan_malloc_linux.cpp:69:3
    #1 0x560b2083a543 in __zend_malloc /tmp/php-asan/Zend/zend_alloc.c:3280:14
    #2 0x560b20839ed0 in _emalloc /tmp/php-asan/Zend/zend_alloc.c:2737:10
    #3 0x560b20d57513 in zend_objects_new /tmp/php-asan/Zend/zend_objects.c:210:24
    #4 0x560b2085418d in _object_and_properties_init /tmp/php-asan/Zend/zend_API.c:1823:22
    #5 0x560b20854390 in object_init_ex /tmp/php-asan/Zend/zend_API.c:1846:9
    #6 0x560b20aa3b28 in ZEND_NEW_SPEC_CONST_UNUSED_HANDLER /tmp/php-asan/Zend/zend_vm_execute.h:10923:6
    #7 0x560b209a602d in execute_ex /tmp/php-asan/Zend/zend_vm_execute.h:58565:7
    #8 0x560b209a6857 in zend_execute /tmp/php-asan/Zend/zend_vm_execute.h:64217:2
    #9 0x560b20dda9d0 in zend_execute_script /tmp/php-asan/Zend/zend.c:1928:3
    #10 0x560b205f961b in php_execute_script_ex /tmp/php-asan/main/main.c:2574:13
    #11 0x560b205f9b18 in php_execute_script /tmp/php-asan/main/main.c:2614:9
    #12 0x560b20de2479 in do_cli /tmp/php-asan/sapi/cli/php_cli.c:935:5
    #13 0x560b20ddf49c in main /tmp/php-asan/sapi/cli/php_cli.c:1310:18
    #14 0x7efce7a29d8f  (/lib/x86_64-linux-gnu/libc.so.6+0x29d8f) (BuildId: 490fef8403240c91833978d494d39e537409b92e)

SUMMARY: AddressSanitizer: heap-use-after-free /tmp/php-asan/Zend/zend_types.h:1346:2 in zend_gc_delref
Shadow bytes around the buggy address:
  0x0c0880000b60: fa fa 00 00 00 00 00 00 fa fa 00 00 00 00 00 fa
  0x0c0880000b70: fa fa 00 00 00 00 00 00 fa fa 00 00 00 00 00 fa
  0x0c0880000b80: fa fa 00 00 00 00 00 00 fa fa 00 00 00 00 00 fa
  0x0c0880000b90: fa fa fd fd fd fd fd fd fa fa 00 00 00 00 00 fa
  0x0c0880000ba0: fa fa fd fd fd fd fd fa fa fa fd fd fd fd fd fa
=>0x0c0880000bb0: fa fa[fd]fd fd fd fd fa fa fa fa fa fa fa fa fa
  0x0c0880000bc0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0880000bd0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0880000be0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0880000bf0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0880000c00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==1479422==ABORTING

PHP Version

PHP 8.5.0-dev

Operating System

No response

[iluuu1994]

This should be fixed in the same way as #16466. I'll create a PR shortly.