[Bug] Firecracker uses up 100% CPU after an upgrade from v1.1.2 to v1.3.1

[gorbak25]

Describe the bug

After upgrading firecracker from v1.1.2 to v1.3.1 the VMM instantly uses up 100% of the CPU while not creating an unix api socket. Firecracker eventually manages to create the socket, but it takes a few minutes. After attaching to the faulty firecracker process with strace it is revealed that firecracker is stuck in a loop trying to close every pid in existence:

To Reproduce

Run firecracker inside a privileged docker container based on node:16-bullseye with /dev/kvm mounted inside. v1.1.2 works fine, v1.3.1 doesn't work at all.

Expected behaviour

The Firecracker process starts without using 100% of the CPU and creates an unix socket.

Environment

• Firecracker version: v1.3.1
• Host kernel: 6.1.12-arch1-1 Archlinux
• Guest kernel: 5.6
• Rootfs used: Ext4, ubuntu 22.04
• Architecture: x86_64, AMD Ryzen 9 5950X

Additional context

I was working on my startup which is a project for creating and managing dev environments inside Firecracker Microvm's. The project works fine using firecracker v1.1.2, after I upgraded the firecracker version the project broke.

Checks

• Have you searched the Firecracker Issues database for similar problems?
• Have you read the existing relevant Firecracker documentation?
• Are you certain the bug being reported is a Firecracker issue?

[gorbak25]

This is the offending commit: f79c94d
Turns out the limit for open FD's is pretty high in the container I've been running firecracker in.

[Rohan-Jagannathan]

Hello, I am representing a group of undergraduate UT Austin students aiming to contribute to open-source virtualization projects on behalf of a virtualization course. Could we have this issue assigned to us?