php-fpm trying to kill another user's pool results in an infinite loop and 99% cpu usage

Description

Hi,

We've come across an interesting issue where an instance of the php-fpm pool ran by one user gets stuck restarting and tries to kill another user's php-fpm pool instances.. similar issue has been described here:

https://bugs.php.net/bug.php?id=74709

Can you please help us fix this? Here's a snippet of strace of the process in question:-

strace: Process 34545 attached
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)
fcntl(3, F_GETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=1, l_len=1, l_pid=32328}) = 0
kill(32328, SIGTERM) = -1 EPERM (Operation not permitted)

the process for which above strace is for is owned by user "xyz", while the process it's trying to kill (process id: 32328) is owned by user "anc".

I would also like to add that this causes all of our websites to timeout. by all websites i mean websites which are using the same php version. like for example the process that's currently stuck and reported in my below mssg is using php 8.0.15 and so all of the websites on my server using php 8.0.15 are timing out.

PHP Version

8.0.15

Operating System

CloudLinux v7.9.0 (CentOS 7)

Aucun fichier source ni test n'est identifié. Commencez par reproduire le redémarrage du pool php-fpm sous PHP 8.0.15 sur CloudLinux v7.9/CentOS 7 et examinez la séquence répétée de kill et file-lock affichée par strace. Le travail est terminé lorsqu'un résultat EPERM ne peut pas provoquer une boucle infinie affectant le pool d'un autre utilisateur et que les sites utilisant la même version de PHP restent accessibles.