Assertion failure `_php_stream_seek` at streams/streams.c

Description

The following code:

<?php
class mystream {
function stream_open($path, $mode, $options, &$opened_path) { return true; }
function stream_seek($offset, $whence) {
$this->pos = $offset; // SEEK_CUR with negative offset → negative pos
return true;
}
function stream_tell() { return $this->pos; }
}
stream_wrapper_register("test", "mystream");
$fp = fopen("test://foo", "rb");
fseek($fp, -1, SEEK_CUR);
fseek($fp, 0, SEEK_CUR);

Resulted in this output:

php: /home/phpfuzz/WorkSpace/flowfusion/php-src/main/streams/streams.c:1465: int _php_stream_seek(php_stream *, zend_off_t, int): Assertion `stream->position >= 0' failed.
Aborted (core dumped)

To reproduce:

./php-src/sapi/cli/php  ./test.php

Commit:

cdc0366bbb366934e91b5461d524226ecb26c891

Configurations:

CC="clang-12" CXX="clang++-12" CFLAGS="-DZEND_VERIFY_TYPE_INFERENCE" CXXFLAGS="-DZEND_VERIFY_TYPE_INFERENCE" ./configure --enable-debug --enable-address-sanitizer --enable-undefined-sanitizer --enable-re2c-cgoto --enable-fpm --enable-litespeed --enable-phpdbg-debug --enable-zts --enable-bcmath --enable-calendar --enable-dba --enable-dl-test --enable-exif --enable-ftp --enable-gd --enable-gd-jis-conv --enable-mbstring --enable-pcntl --enable-shmop --enable-soap --enable-sockets --enable-sysvmsg --enable-zend-test --with-zlib --with-bz2 --with-curl --with-enchant --with-gettext --with-gmp --with-mhash --with-ldap --with-libedit --with-readline --with-snmp --with-sodium --with-xsl --with-zip --with-mysqli --with-pdo-mysql --with-pdo-pgsql --with-pgsql --with-sqlite3 --with-pdo-sqlite --with-webp --with-jpeg --with-freetype --enable-sigchild --with-readline --with-pcre-jit --with-iconv

Operating System:

Ubuntu 20.04 Host, Docker 0599jiangyc/flowfusion:latest

This report is automatically generated by FlowFusion

PHP Version

nightly

Operating System

No response

main/streams/streams.c から始め、_php_stream_seek とレポート内の stream wrapper のシーケンスに注目してください。示されている reproducer で ./php-src/sapi/cli/php ./test.php を実行し、その後、カスタム wrapper での seeking によって position assertion がトリガーされたり abort したりしなくなったことを確認してください。