Sec Bug->Bug #81691 [Opn]: use-after-free of spl file handle

Edit report at https://bugs.php.net/bug.php?id=81691&edit=1 ID: 81691 Updated by: stas@php.net Reported by: cuirongzhen at huawei dot com Summary: use-after-free of spl file handle Status: Open -Type: Security +Type: Bug Package: SPL related Operating System: openEuler/Ubuntu 20.04.1 PHP Version: 8.1.0 Block user comment: N Private report: Y Previous Comments: ------------------------------------------------------------------------ [2021-12-03 10:52:09] cmb@php.net Thanks for reporting this issue! I don't think this qualifies as security issue, but it is certainly bad that the underlying resource can be accessed directly without the knowledge of the object, which causes all kinds of issues (e.g. changing the stream position on the resource would not cause a segfault, but other erroneous behavior). ------------------------------------------------------------------------ [2021-12-03 08:44:32] cuirongzhen at huawei dot com Description: ------------ Usually $file=SplFileObject(..) can be closed with $file=null. However, fclose(end(get_resources())); can directly free the file stream without set $file to null. It can cause use-after-free if $file gets accessed later. Test script: --------------- <?php $file=new SplFileObject("/tmp/1.txt"); fclose(end(get_resources())); var_dump($file->fgets()); ?> Expected result: ---------------- report error at $file->fgets() Actual result: -------------- Program received signal SIGSEGV, Segmentation fault. 0x0000000000000000 in ?? () (gdb) bt #0 0x0000000000000000 in ?? () #1 0x00005555559b83c9 in _php_stream_fill_read_buffer (stream=stream@entry=0x7ffff567e2a0, size=<optimized out>) at ./php-8.1.0-src/main/streams/streams.c:666 #2 0x00005555559b895f in _php_stream_get_line (stream=0x7ffff567e2a0, buf=buf@entry=0x0, maxlen=maxlen@entry=0, returned_len=returned_len@entry=0x7fffffffaa40) at ./php-8.1.0-src/main/streams/streams.c:981 #3 0x0000555555901110 in spl_filesystem_file_read (intern=0x7ffff5682000, silent=0) at ./php-8.1.0-src/ext/spl/spl_directory.c:1887 #4 0x00005555559014ff in zim_SplFileObject_fgets (execute_data=<optimized out>, return_value=0x7ffff56140e0) at ./php-8.1.0-src/ext/spl/spl_directory.c:2174 #5 0x0000555555a73363 in ZEND_DO_FCALL_SPEC_RETVAL_USED_HANDLER () at ./php-8.1.0-src/Zend/zend_vm_execute.h:1870 #6 execute_ex (ex=0x7ffff567e2a0) at ./php-8.1.0-src/Zend/zend_vm_execute.h:54555 #7 0x0000555555a74f14 in zend_execute (op_array=0x7ffff568a000, return_value=0x0) at ./php-8.1.0-src/Zend/zend_vm_execute.h:58882 #8 0x0000555555a084ab in zend_execute_scripts (type=type@entry=8, retval=retval@entry=0x0, file_count=file_count@entry=3) at ./php-8.1.0-src/Zend/zend.c:1761 #9 0x00005555559a471a in php_execute_script (primary_file=<optimized out>) at ./php-8.1.0-src/main/main.c:2534 #10 0x0000555555aeaf9b in do_cli (argc=2, argv=0x555556788ed0) at ./php-8.1.0-src/sapi/cli/php_cli.c:965 #11 0x000055555578f052 in main (argc=2, argv=0x555556788ed0) at ./php-8.1.0-src/sapi/cli/php_cli.c:1367 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=81691&edit=1