apcu+apc.coredump_unmap (and status page) cause segfault ?

[Grummfy]

Hello,

I have an issue, and I think it's related to apcu, and more specially to the apc.coredump_unmap=On option. I got an issue with php (fixed with the upgrade of php from 8.3.14 to 8.3.19) but because I have read that apc.coredump_unmap can help to see what's going on in case of segfault, I activate it. But then, after the upgrade I was still seeing some segfault. But once I disabled the option, the issue disappear.

I see the segfault occurs when I check the status page of php-fpm (but I assume it's a side effect).

So here is my case to reproduce it. Sorry, I got no extra time to narrower it more.

The issue occurs in 8.3.19 -> 8.3.21(last 8.3). But In 8.4.7 I got no issue.

So here is my docker compose file

services:
  php-dbg:
    platform: linux/amd64
    build:
      dockerfile: ./Dockerfile
      target: php_base
    extra_hosts:
      - "host.docker.internal:host-gateway"
    tty: true
  php-fpm-status-dbg:
    image: hipages/php-fpm_exporter
    command:
      - --phpfpm.scrape-uri=tcp://php-dbg:9001/_status
    depends_on:
      - php-dbg
prometheus:
   image: prom/prometheus:v2.53.3
     command:
         - --config.file=/etc/prometheus.yaml
         - --web.enable-remote-write-receiver
         - --enable-feature=exemplar-storage
        - --enable-feature=native-histograms
     volumes:
         - ./docker/opentelemetry/prometheus/prometheus.yaml:/etc/prometheus.yaml
     ports:
         - "9090:9090"

prometheus.yml

global:
    scrape_interval:     15s
    evaluation_interval: 15s

scrape_configs:
    - job_name: 'prometheus'
      static_configs:
          - targets: [ 'localhost:9090' ]global:
    scrape_interval:     15s
    evaluation_interval: 15s

scrape_configs:
    - job_name: 'prometheus'
      static_configs:
          - targets: [ 'localhost:9090' ]
    - job_name: 'php-fpm-status-dbg'
      static_configs:
          - targets: ['php-fpm-status-dbg:9253']
      scheme: http
      metrics_path: /metrics

Dockerfile

#syntax=docker/dockerfile:1.4
ARG PHP_VERSION=8.3.21

FROM php:$PHP_VERSION-fpm-alpine AS php_upstream
FROM mlocati/php-extension-installer:2 AS php_extension_installer_upstream
FROM composer/composer:2-bin AS composer_upstream
FROM php_upstream AS php_base
WORKDIR /srv/app
RUN apk update && \
    apk upgrade && \
    apk add --no-cache \
		acl \
		fcgi \
		file \
		gettext \
		git \
    	gnu-libiconv \
        icu-libs \
        icu-data-full \
        linux-headers \
        bash \
        tzdata \
    	su-exec \
	&& \
    apk cache --no-interactive purge && \
    rm -rf /var/cache/apk/*
COPY --from=php_extension_installer_upstream --link /usr/bin/install-php-extensions /usr/local/bin/
RUN set -eux; \
    install-php-extensions \
		apcu \
		intl \
		opcache \
		zip
ENV TZ=Europe/brussels
ENV COMPOSER_ALLOW_SUPERUSER=1
ENV PATH="${PATH}:/root/.composer/vendor/bin"

COPY --link zz-docker.conf /usr/local/etc/php-fpm.d/zz-docker.conf
COPY --link z-my.ini /usr/local/etc/php/conf.d/z-my.ini
COPY --link docker-entrypoint.sh /usr/local/bin/docker-entrypoint
COPY --from=composer_upstream --link /composer /usr/bin/composer

RUN mkdir storage && \
    mkdir -p /var/run/php && \
    chmod 0755 /usr/local/bin/docker-entrypoint && \
    echo '<?php echo "hello";' > /srv/app/index.php

# expose status page
EXPOSE 9001

ENTRYPOINT ["docker-entrypoint"]
CMD ["php-fpm"]

z-my.ini

apc.enable_cli = 1
apc.coredump_unmap = On

date.timezone = Europe/Paris
session.auto_start = Off
short_open_tag = Off

zz-docker.conf

[global]
daemonize = no
process_control_timeout = 120
error_log = /proc/self/fd/2
log_level = notice

emergency_restart_threshold = 5
emergency_restart_interval = 1m

[www]
listen = /var/run/php/php-fpm.sock
listen.mode = 0666
ping.path = /ping

pm = dynamic
pm.max_children = 8
pm.start_servers = 2
pm.min_spare_servers = 1
pm.max_spare_servers = 4
pm.max_requests = 150

pm.status_path = /_status
pm.status_listen = 0.0.0.0:9001

docker-entrypoint.sh

#!/bin/sh
set -ex

echo 'Entrypoint starting'

# first arg is `-f` or `--some-option`
if [ "${1#-}" != "$1" ]; then
	set -- php-fpm "$@"
fi

RUN_AS=''

# when running php, php-fpm or bin/console do some extra stuff
if [ "$1" = 'php-fpm' ] || [ "$1" = 'php' ] || [ "$1" = 'bin/console' ]; then
	RUN_AS='www-data'

	# add user to tty group to get the right to output
	addgroup www-data tty

	setfacl -R -m u:www-data:rwX -m u:"$(whoami)":rwX /run/php
	setfacl -dR -m u:www-data:rwX -m u:"$(whoami)":rwX /run/php

	echo 'PHP app ready!'
fi

# launch php-fpm with limited user
if [ "$RUN_AS" != '' ]; then
	su-exec "${RUN_AS}" docker-php-entrypoint "$@"
else
	docker-php-entrypoint "$@"
fi

[madmajestro]

Which apcu version does the error occur with? 5.1.24, current master branch, ...?

[Grummfy]

oups, I forget to say it ;)
5.1.24