Linux Weekly News

Version 6.14.0 of Framework Mono has been announced.

This is the first release of Framework Mono from its new home at WineHQ. It includes work from the past 5 years that was never included in a stable release because no stable branch had been created in that time. Highlights are native support for ARM64 on macOS and many improvements to windows forms for X11.

See the release notes for a full list of new features and plans for future releases.

Security updates have been issued by Debian (libaws, ruby2.7, and squid), Fedora (bigloo, emacs, neovim, python-jinja2, rizin, and tree-sitter), Oracle (kernel), Red Hat (grub2, kernel, kernel-rt, and libxml2), SUSE (iniparser, kernel, krb5, libxkbfile, and u-boot), and Ubuntu (gnuchess, openjdk-17-crac, openjdk-21-crac, and openvpn).

The Python project's recent switch to a tail-calling interpreter may not provide as large a speed advantage as initially thought. A blog post from Nelson Elhage gives the details. In short, switching to a tail-call-based interpreter accidentally works around an unfixed regression in LLVM 19. On other compilers, the performance benefit (while still present) is more moderate.

When the tail-call interpreter was announced, I was surprised and impressed by the performance improvements, but also confused: I'm not an expert, but I'm passingly-familiar with modern CPU hardware, compilers, and interpreter design, and I couldn't explain why this change would be so effective. I became curious – and perhaps slightly obsessed – and the reports in this post are the result of a few weeks of off-and-on compiling and benchmarking and disassembly of dozens of different Python binaries, in an attempt to understand what I was seeing.

One of the advantages of the Rust type system is its ability to encapsulate requirements about the state of the program in the type system; often, this state includes which locks must be held to be able to carry out specific operations. C lacks the ability to express these requirements, but there would be obvious benefits if that kind of feature could be grafted onto the language. The Clang compiler has made some strides in that direction with its thread-safety analysis feature; two developers have been independently working to take advantage of that work for the kernel.

Security updates have been issued by Debian (openvpn and thunderbird), Fedora (buildah, chromium, podman-tui, python-spotipy, qt6-qtwebengine, and vim), Mageia (chromium-browser-stable and gpac), Oracle (krb5), Red Hat (firefox, kernel, kernel-rt, libxml2, and pcs), SUSE (buildah, chromedriver, chromium, firefox, go1.23, go1.24, grype, python, python311-GitPython, ruby3.4-rubygem-rack, thunderbird, and xen), and Ubuntu (xorg-server, xorg-server-hwe-16.04, xorg-server-hwe-18.04).

Linus has released 6.14-rc6 for testing. "This release remains on track, nothing special to report".

The 6.6.82 stable kernel has been released. "All i386 users of the 6.6 kernel series must upgrade (as they skipped the last release.) All other arches can skip this one as it should not affect them."

Greg Kroah-Hartman has announced the release of four more stable kernels: 6.13.6, 6.12.18, 6.6.81, and 6.1.130. Unlike a normal release, Kroah-Hartman did not call for all users to update their kernels. Specifically, the 6.6.81 kernel is currently broken on i386 systems, and users should wait for 6.6.82.

Matthieu Clemenceau has published a status update on Ubuntu 25.04 (Plucky Puffin) development to the Ubuntu Discourse forum. This includes updates on Ubuntu's adoption of Dracut as an alternative to initramfs-tools, a move to a single ISO for arm64 devices rather than device-specific images, and reverting the planned O3 optimization flags for Plucky Puffin.

Earlier in this cycle, we announced plans to enable the O3 optimization level for all Ubuntu packages by default. As part of this effort, we conducted extensive benchmarking, which revealed that while some workloads saw improvements, overall system performance slightly declined, and binary sizes increased. Given these results, we are likely to revert this change soon.

The beta for Ubuntu 25.04 is planned for March 27, with the final release scheduled on April 17.

On January 20, Thomas Weißschuh shared a new patch set implementing an alternate method for checking the integrity of loadable kernel modules. This mechanism, which checks module integrity based on hashes computed at build time instead of using cryptographic signatures, could enable reproducible kernel builds in more contexts. Several distributions have already expressed interest in the patch set if Weißschuh can get it into the kernel.

Security updates have been issued by Debian (chromium), Fedora (firefox and man2html), Mageia (erlang, ffmpeg, and vim), Oracle (doxygen, firefox, python-jinja2, squid, and webkit2gtk3), Red Hat (nodejs:18), SUSE (emacs, go1.23, go1.24, and pcp), and Ubuntu (ansible, firefox, linux-azure, linux-nvidia, and python-django).

The kernel project has usually been willing to make fundamental internal changes if they lead to a better kernel in the end. The project also, though, goes out of its way to avoid breaking interfaces that have been exposed to user space, even if programs come to rely on behavior that was never documented. Sometimes, those two principles come into conflict, leading to a situation where fixing problems within the kernel is either difficult or impossible. This sort of situation has been impeding performance improvements in the kernel's POSIX timers implementation for some time, but it appears that a solution has been found.

Security updates have been issued by Debian (firefox-esr), Fedora (firefox and vim), Red Hat (firefox), Slackware (mozilla), SUSE (firefox, firefox-esr, kernel, and podman), and Ubuntu (gpac, kernel, linux, linux-aws, linux-gcp, linux-gcp-5.15, linux-gke, linux-hwe-5.15, and redis).

Inside this week's LWN.net Weekly Edition:

• Front: Firefox forks; Bend and Vine; FineIBT; Guard pages; Fedora's Flatpak packaging; Zotero.
• Briefs: LFS 12.3; FerretDB 2.0; Firefox; Fish 4.0; Incus 6.10; Thunderbird 136.0; Xen 4.20; Quotes; ...
• Announcements: Newsletters, conferences, security updates, patches, and more.

The Google Bug Hunters blog has a detailed description of how a vulnerability in AMD's microcode-patching functionality was discovered and exploited; the authors have also released a set of tools to assist with this kind of research in the future.

Secure hash functions are designed in such a way that there is no secret key, and there is no way to use knowledge of the intermediate state in order to generate a collision. However, CMAC was not designed as a hash function, and therefore it is a weak hash function against an adversary who has the key. Remember that every AMD Zen CPU has to have the same AES-CMAC key in order to successfully calculate the hash of the AMD public key and the microcode patch contents. Therefore, the key only needs to be revealed from a single CPU in order to compromise all other CPUs using the same key. This opens up the potential for hardware attacks (e.g., reading the key from ROM with a scanning electron microscope), side-channel attacks (e.g., using Correlation Power Analysis to leak the key during validation), or other software or hardware attacks that can somehow reveal the key. In summary, it is a safe assumption that such a key will not remain secret forever.

Version 2.0.0 of FerretDB has been released. FerretDB is an open-source alternative to MongoDB, which switched to a non-open license in 2018, built on top of PostgreSQL. This release utilizes the DocumentDB PostgreSQL extension for better performance, adds vector search, and replication.

Functional programming languages have a long association with graphs. In the 1990s, it was even thought that parallel graph-reduction architectures could make functional programming languages much faster than their imperative counterparts. Alas, that prediction mostly failed to materialize. Even though graphs are still used as a theoretical formalism in order to define and optimize functional languages (such as Haskell's spineless tagless graph-machine), they are still mostly compiled down to the same old non-parallel assembly code that every other language uses. Now, two projects — Bend and Vine — have sprung up attempting to change that, and prove that parallel graph reduction can be a useful technique for real programs.

The Xen Project has announced the release of Xen 4.20. This release adds support for AMD Zen 5 CPUs, improved compliance with the MISRA C standard, work on PCI-passthrough on Arm, and more. Xen 4.20 also removes support for Xeon Phi CPUs, which were discontinued in 2018. See the feature list and release notes for more information.

Version 136.0 of the Thunderbird Desktop mail client has been released. The release includes a quick toggle for adapting messages to dark mode, and a new "Appearance" setting to control message threading and sorting order globally, as well as a number of bug fixes. See the security advisory for a full list of security vulnerabilities addressed in Thunderbird 136.0.

Version 12.3 of Linux From Scratch (LFS) has been released, along with Beyond Linux From Scratch (BLFS) 12.3. LFS provides step-by-step instructions on building a customized Linux system entirely from source, and BLFS helps to extend an LFS installation into a more usable system. Notable changes in this release include toolchain updates to GNU Binutils 2.44, GNU C Library (glibc) 2.41, and Linux 6.13.2. The Changelog has a full list of changes since the previous stable release.