Kangrejos 2025 Interview: Greg Kroah-Hartman, Linux Foundation Fellow

At Kangrejos 2025, the Rust for Linux workshop, Tyler Mandry sits down on behalf of the Rust Project Content Team with Greg Kroah-Hartman, Linux stable kernel maintainer and Linux Foundation Fellow, to talk about Rust in the kernel, the email-based development model, Git, and what keeps kernel developers around for decades. Greg maintains the stable kernels, the driver core, USB, and more, and has seen essentially every Linux security bug for twenty-some years: thirteen CVEs a day. Topics include: • Why he's open to Rust: whole classes of bugs (leaked locks, unchecked error returns, memory cleanup mistakes) that just can't happen, by virtue of the language • "My friend was right, it's fun": rewriting the kernel's CVE tooling from bash and C into Rust • The hard part: the C/Rust bindings, the most complex Rust code he's seen, and why getting that intersection right decides whether this succeeds • Tagging untrusted data from user space with the type system, so unverified input won't even build • Why the kernel's email-plus-Git model exists: 9-10 accepted patches per hour, thousands of developers from ~450 companies, no central point of failure, and it works offline • Git's origins in kernel development, Quilt for stable patch stacks, and thoughts on jj • The kernel memory model: a formal proof spanning x86, Arm, and Alpha, and why Rust should take a look • Retention as a feature: exponential contributor curves, 30-year networking veterans, and retirees from other operating systems joining because "this is fun again" • How Rust already improved the kernel's C: Danilo's solution to the device-removal problem, ported back to C by a Google developer to clean up all the C drivers Links mentioned: Greg's site: http://www.kroah.com/ The Linux kernel: https://kernel.org/ Rust for Linux: https://rust-for-linux.com/ Kangrejos: https://kangrejos.com/ Rust Atomics and Locks by Mara Bos (free online): https://marabos.nl/atomics/ Linux Device Drivers, 3rd edition (free online): https://lwn.net/Kernel/LDD3/ jj (Jujutsu): https://github.com/jj-vcs/jj Books Greg recommends: Code Complete, The Mythical Man-Month, Programming Pearls, Beautiful Code, and Robert Love's Linux Kernel Development. Interview conducted by Tyler Mandry on behalf of the Rust Project Content Team.