String corruption on deployments with php-fpm 8.1.6

Description

Hello,

We experience seemingly random in-memory corruption of code when deploying new versions of our PHP app on php-fpm 8.1.6 on Linux. Here is a sample error message:

include(/space/www/api2019/data/releases/20220607140425/vendor/la�R�F): Failed to open stream: No such file or directory

This example happens in the class loader from composer. The beginning of the file name is correct, the end is obviously not.

Another example (another release on another server):

Call to undefined function Symfony\Component\HttpFoundation\implode()

This bug is not easily reproducible, it happens in random-looking places in the code, sometimes but not always, on some servers but not others (we have 10 app servers, the bug appears on one server at a time, very rarely two, not on every release but more than half of them).

When it happens, it looks like there is only one corrupted chunk of data; depending on the affected data, it may only cause a few real errors or basically prevent the code from working on the server at all. It generates errors for a few minutes. Restarting the fpm daemon fixes it; reloading it or running opcache_reset() does not.

We will try to reproduce it on a staging server; at the moment I can only say it appears under load and not under light testing.

It may or may not be related to #8731 (same app, same servers, seemingly fixed by downgrading to 8.0.19).

I know this report is not really helpful, but I'm at a loss how to make it more useful.

Downgrading to PHP 8.0.19 seems to fix the issue.

PHP Version

PHP 8.1.6 (cli) (built: May 17 2022 16:49:19) (NTS)

Operating System

Debian 10

首先，尝试在运行 Debian 10 上 PHP-FPM 8.1.6 且处于负载下的 staging 服务器上复现该损坏现象，并与 PHP 8.0.19 进行比较。观察重启 FPM、重新加载 FPM 或运行 opcache_reset() 是否会改变结果，并检查 Composer ClassLoader 失败以及与 #8731 的潜在关系。确认了可复现的原因和经过验证的修复方案后，即视为完成。