Yonghong Song brought a story about tracking down the cause of a strange verifier error message to the 2025 Linux Storage, Filesystem, Memory-Management, and BPF Summit. He then presented some possible ways to improve Clang's user experience for anyone running into the same class of error in the future. Toward the end of his allotted time, he also discussed the problems with optimizations that change the signature of functions — a problem that José Marchesi had also brought up in the previous session.

• Front: Calibre 8.0; Fedora reproducibility; OpenWrt One; 6.15 Merge Window; LSFMM+BPF coverage including BPF in GCC, Rust merging process, and more.
• Briefs: Ubuntu namespaces; New FPL; PorteuX 2.0; Firefox 137.0; GCC Rust; Rockbox 4.0; Rust specification; Thundermail; Dave Täht RIP; Quotes; ...
• Announcements: Newsletters, conferences, security updates, patches, and more.

Saying that calibre is ebook-management software undersells the application by a fair margin. Calibre is an open-source Swiss Army knife for ebooks that can be used for everything from creating ebooks, converting ebooks from obscure formats to modern formats like EPUB, to serving up an ebook library over the web. The most recent major release, calibre 8.0, brings a better text-to-speech engine, a tool for creating audio overlays when authoring ebooks, support for profiles in the ebook viewer, and more.

José Marchesi and David Faust kicked off the BPF track at the 2025 Linux Storage, Filesystem, Memory-Management, and BPF Summit with an extra-long session on what they have been doing to support compiling to BPF in GCC. Overall, the project is slowly working toward full support for BPF, with most of the self-tests now passing using Faust's in-progress patches. However, the progress toward that goal has turned up a number of problems with how Clang supports BPF that needed to be discussed at length to find a path forward for both projects.

Ryan Sipes has announced efforts to expand Thunderbird's offerings with web services to "enhance the experience of using Thunderbird".

The Why for offering these services is simple. Thunderbird loses users each day to rich ecosystems that are both clients and services, such as Gmail and Office365. These ecosystems have both hard vendor lock-ins (through interoperability issues with 3rd-pary clients) and soft lock-ins (through convenience and integration between their clients and services). It is our goal to eventually have a similar offering so that a 100% open source, freedom-respecting alternative ecosystem is available for those who want it.

The planned services include hosted email, appointment scheduling, a revival of Firefox Send, and (of course) an AI assistant based on a partnership with Flower AI. The AI features will "always be optional for use by people who want them". Sipes is managing director of product for Thunderbird's parent organization, MZLA Technologies Corporation. LWN covered his GUADEC 2024 keynote last July.

Outgoing Fedora Project Leader (FPL) Matthew Miller has announced his successor, Jef Spaleta.

Some of you may remember Jef's passionate voice in the early Fedora community. He got involved all the way back in the days of fedora.us, before Red Hat got involved. Jef served on the Fedora Board from July 2007 through the end of 2008. This was the critical time after Fedora Extras and Fedora Core merged into one Fedora Linux where, with the launch of the "Features" process, Fedora became a truly community-led project.

Spaleta will be joining Red Hat full time in May and Miller will be formally handing off FPL duties at the Flock conference in June.

Version 2.0 of PorteuX, a distribution based on Slackware Linux, has been released. This release adds the ability to test experimental Wayland sessions for the Cinnamon, LXQt, and Xfce desktops. PorteuX 2.0 updates the Linux kernel to 6.14 and includes many package updates and bug fixes. Users have the choice of PorteuX stable or its rolling release called current. See the install.txt for instructions on installing PorteuX to disk.

Searching through LWN's archives will turn up many references to his work fixing WiFi, improving queue management, tackling bufferbloat, and more. Farewell, Dave, we hope the music is good wherever you are.

(Thanks to Jon Masters for the heads-up).

The effort to ensure that open-source software is reproducible has been gathering steam over the years, and gaining traction with major Linux distributions. Debian, for example, has been working toward reproducible builds for more than a decade; it can now produce official live CDs of the current stable release that are reproducible. Fedora started on the path much later, but it has progressed far enough that the project is now considering a change proposal for the Fedora 43 development cycle, expected to be released in October, with a goal of making 99% of Fedora's package builds reproducible. So far, reaction to the proposal seems favorable and focused primarily on how to achieve the goal—with minimal pain for packagers—rather than whether to attempt it.

Greg Kroah-Hartman announced the release of four stable kernels on March 28: 6.13.9, 6.12.21, 6.6.85, and 6.1.132. Users are advised to upgrade.

KDE contributor David Edmundson has published a blog post about improving KDE Plasma's login experience by replacing SDDM with a new Plasma Login Manager.

It's worth stressing nothing is official or set in stone yet, whilst it has come up in previous Plasma online meetings and in the 2023 Akademy. I'm posting this whilst starting a more official discussion on the plasma-devel mailing list.

Oliver Beard and I have made a new mutli-process greeter, that uses the same startup mechanism as the desktop session. It doesn't have all the features that we propose at the start of the blog, but an architecture where features and services can be slowly and safely added.

That discussion is here for those who would like to follow along. The prototype is currently in two repositories: plasma-login for the frontend work, and plasma-login-manager, which is a fork of SDDM.

Ubuntu 23.10 and 24.04 LTS introduced a feature using AppArmor to restrict access to user namespaces. Qualys has reported three ways to bypass AppArmor's restrictions and enable local users to gain full administrative capabilities within a user namespace. Ubuntu has followed up with a post that explains the namespace-restriction feature in detail, and says these bypasses do not constitute security vulnerabilities.

While a superficial observation of the application of user namespaces may indicate privileged (root level) access, this is a fictitious state that is operating as expected, with access control still mapped to the real (root namespace) user's permissions. As such, these bypasses do not enable more access than what the default Linux kernel unprivileged user namespace feature allows in most Linux distributions. They do, however, demonstrate limitations that we are looking to address in order to strengthen existing protections against as-of-yet-unknown Linux kernel vulnerabilities.

LWN covered Ubuntu 24.04 LTS last May.

One recurring criticism of Rust has been that the language has no official specification. This is a barrier to adoption in some safety-conscious organizations, as well as to writing alternate language implementations. Now, the Rust project has announced that it will be adopting the Ferrocene Language Specification (FLS) developed by Ferrous Systems and maintaining it as part of the core project. While this may not satisfy die-hard standardization-process enthusiasts, it's a step toward removing another barrier to using Rust in safety-critical systems.

It's in that light that we're pleased to announce that we'll be adopting the FLS into the Rust Project as part of our ongoing specification efforts. This adoption is being made possible by the gracious donation of the FLS by Ferrous Systems. We're grateful to them for the work they've done in assembling the FLS, in making it fit for qualification purposes, in promoting its use and the use of Rust generally in safety-critical industries, and now, for working with us to take the next step and to bring the FLS into the Project.