CVE-2022-47929: traffic control noqueue no problem?

USER namespaces power the functionality of our favorite tools such as docker, podman, and kubernetes. We wrote about Linux namespaces back in June and explained them like this:

Most of the namespaces are uncontroversial, like the UTS namespace which allows the host system to hide its hostname and time. Others are complex but straightforward - NET and NS (mount) namespaces are known to be hard to wrap your head around. Finally, there is this very special, very curious USER namespace. USER namespace is special since it allows the - typically unprivileged owner to operate as "root" inside it. It's a foundation to having tools like Docker to not operate as true root, and things like rootless containers.

Due to its nature, allowing unprivileged users access to USER namespace always carried a great security risk. With its help the unprivileged user can in fact run code that typically requires root. This code is often under-tested and buggy. Today we will look into one such case where USER namespaces are leveraged to exploit a kernel bug that can result in an unprivileged denial of service attack.

Enter Linux Traffic Control queue disciplines

In 2019, we were exploring leveraging Linux Traffic Control's queue Continue reading

Live-patching security vulnerabilities inside the Linux kernel with eBPF Linux Security Module

Linux Security Modules (LSM) is a hook-based framework for implementing security policies and Mandatory Access Control in the Linux kernel. Until recently users looking to implement a security policy had just two options. Configure an existing LSM module such as AppArmor or SELinux, or write a custom kernel module.

Linux 5.7 introduced a third way: LSM extended Berkeley Packet Filters (eBPF) (LSM BPF for short). LSM BPF allows developers to write granular policies without configuration or loading a kernel module. LSM BPF programs are verified on load, and then executed when an LSM hook is reached in a call path.

Let’s solve a real-world problem

Modern operating systems provide facilities allowing "partitioning" of kernel resources. For example FreeBSD has "jails", Solaris has "zones". Linux is different - it provides a set of seemingly independent facilities each allowing isolation of a specific resource. These are called "namespaces" and have been growing in the kernel for years. They are the base of popular tools like Docker, lxc or firejail. Many of the namespaces are uncontroversial, like the UTS namespace which allows the host system to hide its hostname and time. Others are complex but straightforward - NET and NS (mount) namespaces Continue reading