HashTable use-after-destroy during lazy proxy __get() with dynamic properties
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Bug
Category: Engine
Status: Verified
- Dominant language
- C
- Stars
- 40.4k
- Forks
- 8.1k
- Avg merge
- 2d 13h
- Merged PRs (30d)
- 96
Description
Description
The following code:
<?php
#[AllowDynamicProperties]
class RealInstance {
public $_;
public function __get($name) {
global $obj;
$obj->foo ??= $obj->$$a[] =&$$a;
$a[] =$$a;
$x[!0] =$$a;
return $this->name;
}
}
class Proxy extends RealInstance {
public function r_get($name) {
return $this->$name;
}
}
$rc = new ReflectionClass(Proxy::class);
$obj = $rc->newLazyProxy(function () {
return new RealInstance;
});
$real = $rc->initializeLazyObject($obj);
var_dump($real->prop);
Resulted in this output:
/path/to/php-src/Zend/zend_hash.c(2699) : ht=0x7f6a9f802900 is already destroyed
php: /path/to/php-src/Zend/zend_hash.c:73: void _zend_is_inconsistent(const HashTable *, const char *, int): Assertion `0' failed.
Aborted
Notes
This bug triggers the same hash table use-after-destroy assertion as #20286 but via a different execution path.
Commit:
56795d2810e
Build configuration:
CC="clang" CXX="clang++" CFLAGS="-fsanitize=address -g -O0" CXXFLAGS="-fsanitize=address -g -O0" LDFLAGS="-fsanitize=address" ./buildconf --force && ./configure --enable-debug --enable-address-sanitizer --disable-shared --with-pic --enable-mbstring --with-zlib
PHP Version
PHP 8.6.0-dev (cli) (built: Nov 29 2025 14:32:34) (NTS DEBUG)
Copyright (c) The PHP Group
Zend Engine v4.6.0-dev, Copyright (c) Zend Technologies
with Zend OPcache v8.6.0-dev, Copyright (c), by Zend Technologies
Operating System
Ubuntu 22.04
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Run the supplied reproducer with the documented debug and AddressSanitizer build, then inspect the assertion in zend_hash.c and the lazy proxy path through __get(), newLazyProxy(), and initializeLazyObject(). Done means the reproducer no longer reaches the HashTable use-after-destroy assertion and a regression test covers this execution path.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- c, php
- Domain
- backend
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Quiet
- Clarity
- Mostly clear
- Newbie friendliness
- 42/100