2026-05-07
When a critical Linux kernel privilege escalation was publicly disclosed, Cloudflare's security and engineering teams detected, investigated, and mitigated the threat across our global fleet, confirming zero customer impact and no malicious exploitation....
2025-02-14
The Linux kernel can produce a hung task warning. Searching the Internet and the kernel docs, you can find a brief explanation that the process is stuck in the uninterruptible state....
2024-03-06
This post illustrates some of the Linux Kernel features, which are helping us to keep our production systems more secure. We will deep dive into how they work and why you may consider enabling them as well...
2023-05-11
If you run your software on Linux, the Linux Kernel itself can satisfy all your cryptographic needs! In this post we will explore Linux Crypto API for user applications and try to understand its pros and cons...
2023-03-20
If I navigate to https://blog.cloudflare.com/, my browser will connect to a remote TCP address from the local IP address assigned to my machine, and a randomly chosen local TCP port. What happens if I then decide to head to another site?...
2022-11-28
Many leaks happen because of software bugs and security vulnerabilities. In this post we will learn how the Linux kernel can help protect cryptographic keys from a whole class of potential security vulnerabilities: memory access violations....
2022-10-10
We have first adopted the BPF tail calls when building our XDP-based packet processing pipeline. BPF tail calls have served us well since then. But they do have their caveats...
2022-02-04
Chances are you might have heard of io_uring. It first appeared in Linux 5.1, back in 2019, and was advertised as the new API for asynchronous I/O. Its goal was to be an alternative to the deemed-to-be-broken-beyond-repair AIO, the “old” asynchronous I/O API...
2021-03-04
We have been dealing with conntrack, the connection tracking layer in the Linux kernel, for years. And yet, despite the collected know-how, questions about its inner workings occasionally come up. When they do, it is hard to resist the temptation to go digging for answers....
2020-03-25
Encrypting data at rest is vital for Cloudflare with more than 200 data centres across the world. In this post, we will investigate the performance of disk encryption on Linux and explain how we made it at least two times faster for ourselves and our customers!...
2019-07-10
For some time I’ve wanted to play with coverage-guided fuzzing. I decided to have a go at the Linux Kernel netlink machinery. It's a good target: it's an obscure part of kernel, and it's relatively easy to automatically craft valid messages....
