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[$] Toward fast, containerized, user-space filesystems
Filesystems are complex and performance-sensitive beasts. They can also present security concerns. Microkernel-based systems have long pushed filesystems into separate processes in order to contain any vulnerabilities that may be found there. Linux can do the same with the Filesystem in Userspace (FUSE) subsystem, but using FUSE brings a significant performance penalty. Darrick Wong is working on ways to eliminate that penalty, and he has a massive patch set showing how ext4 filesystems can be safely implemented in user space by unprivileged processes with good performance. This work has the potential to radically change how filesystems are managed on Linux systems.
[$] LWN.net Weekly Edition for November 6, 2025
Posted Nov 6, 2025 0:14 UTC (Thu)The LWN.net Weekly Edition for November 6, 2025 is available.
Inside this week's LWN.net Weekly Edition
- Front: Python thread safety; Namespace reference counting; Merigraf; Speeding up short reads; Julia 1.12; systemd security.
- Briefs: CHERIoT 1.0; Chromium XSLT; Arm KASLR; Bazzite; Devuan 6.0; Incus 6.18; LXQt 2.3.0; Rust 1.91.0; Quotes; ...
- Announcements: Newsletters, conferences, security updates, patches, and more.
[$] A security model for systemd
Linux has many security features and tools that have evolved over
the years to address threats as they emerge and security gaps as they
are discovered. Linux security is all, as Lennart Poettering observed at the All Systems Go! conference held
in Berlin, somewhat random and not a "clean
"
design. To many observers, that may also appear to be the case for
systemd; however, Poettering said that he does have a vision for how
all of the security-related pieces of systemd are meant to fit
together. He wanted to use his talk to explain "how the individual
security-related parts of systemd actually fit together and why they
exist in the first place
".
[$] Julia 1.12 brings progress on standalone binaries and more
Julia is a modern programming language that is of particular interest to scientists due to its high performance combined with language features such as Lisp-style macros, an advanced type system, and multiple dispatch. We last looked at Julia in January on the occasion of its 1.11 release. Early in October Julia 1.12 appeared, bringing a handful of quality-of-life improvements for Julia programmers, most notably support, though still experimental and limited, for the creation of binaries.
[$] An explicit thread-safety proposal for Python
Python already has several ways to run programs concurrently — including asynchronous functions, threads, subinterpreters, and multiprocessing — but all of those options have drawbacks of one kind or another. PEP 703 ("Making the Global Interpreter Lock Optional in CPython") removed a major barrier to running Python threads in parallel, but also exposed Python programmers to the same tricky synchronization problems found in other languages supporting multithreaded programs. A new draft proposal by Mark Shannon, PEP 805 ("Safe Parallel Python"), suggests a way for the CPython runtime to cut down on concurrency bugs, making it more practical for Python programmers to use versions of the language without the global interpreter lock (GIL).
[$] Namespace reference counting and listns()
The kernel's namespaces feature is, among other things, a key part of the implementation of containers. Like much in the kernel, though, the namespace API evolved over time; there was no design at the outset. As a result, this API has some rough edges and missing features. Christian Brauner is working to straighten out the namespace situation somewhat with this daunting 72-part patch series that, among other things, adds a new system call to allow user space to query the namespaces present on the system.
[$] Mergiraf: syntax-aware merging for Git
The idea of automatic syntax-aware merging in version-control systems goes back to 2005 or earlier, but initial implementations were often language-specific and slow. Mergiraf is a merge-conflict resolver that uses a generic algorithm plus a small amount of language-specific knowledge to solve conflicts that Git's default strategy cannot. The project's contributors have been working on the tool for just under a year, but it already supports 33 languages, including C, Python, Rust, and even SystemVerilog.
[$] The long path toward optimizing short reads
The kernel's file-I/O subsystems have been highly optimized over the years in the hope of providing the best performance for a wide variety of workloads. There is, however, one workload type that suffers with current kernels: applications that perform many short reads, in multiple processes, from the same file. Kiryl Shutsemau has been working on a patch to try to optimize this case, but the task is turning out to be harder than one might expect.
LWN.net Weekly Edition for October 30, 2025
Posted Oct 30, 2025 0:08 UTC (Thu)The LWN.net Weekly Edition for October 30, 2025 is available.
Inside this week's LWN.net Weekly Edition
- Front: Pixnapping attack; Fil-C; Debian ftpmasters; GoFundMe complaints; Safer user-space access.
- Briefs: Man pages 6.16; Btrfs on AlmaLinux; Fedora Linux 43; ICANN report; PSF grants; Rust Coreutils 0.3.0; Tor Browser 15.0; Quotes; ...
- Announcements: Newsletters, conferences, security updates, patches, and more.
Retrieving pixels from Android phones with Pixnapping
A new class of attacks on Android phones, called "Pixnapping", was announced on October 13. It allows a malicious app to gather output rendered in a victim app, pixel-by-pixel, by exploiting a GPU side-channel. Depending on what the victim app displays, anything from sensitive email and chats to two-factor authentication (2FA) codes could be captured—and shipped off to an attacker's site.
Mastodon 4.5 released
Version 4.5 of the Mastodon decentralized social-media platform has been released. Notable features in this release include quote posts, native emoji support, as well as enhanced moderation and blocking features for server administrators. The project also has a post detailing new features in 4.5 for developers of clients and other software that interacts with Mastodon.
Freedesktop.org now hosts the Filesystem Hierarchy Standard
The future of the Filesystem Hierarchy Standard (FHS) has been under discussion for some time; now,
Neal Gompa has announced
that the FHS is "hosted and stewarded
" by Freedesktop.org.
For those who are unaware, the Filesystem Hierarchy Standard (FHS) is the definition for POSIX operating systems to organize system and user data. It is broadly adopted by Linux, BSD, and other operating systems that follow POSIX-like conventions.
See this page for the specification's new home.
Security updates for Thursday
Security updates have been issued by Debian (unbound), Fedora (deepin-qt5integration, deepin-qt5platform-plugins, dtkcore, dtkgui, dtklog, dtkwidget, fcitx-qt5, fcitx5-qt, fontforge, gammaray, golang-github-openprinting-ipp-usb, kddockwidgets, keepassxc, kf5-akonadi-server, kf5-frameworkintegration, kf5-kwayland, plasma-integration, python-qt5, qadwaitadecorations, qt5, qt5-qt3d, qt5-qtbase, qt5-qtcharts, qt5-qtconnectivity, qt5-qtdatavis3d, qt5-qtdeclarative, qt5-qtdoc, qt5-qtgamepad, qt5-qtgraphicaleffects, qt5-qtimageformats, qt5-qtlocation, qt5-qtmultimedia, qt5-qtnetworkauth, qt5-qtquickcontrols, qt5-qtquickcontrols2, qt5-qtremoteobjects, qt5-qtscript, qt5-qtscxml, qt5-qtsensors, qt5-qtserialbus, qt5-qtserialport, qt5-qtspeech, qt5-qtsvg, qt5-qttools, qt5-qttranslations, qt5-qtvirtualkeyboard, qt5-qtwayland, qt5-qtwebchannel, qt5-qtwebengine, qt5-qtwebkit, qt5-qtwebsockets, qt5-qtwebview, qt5-qtx11extras, qt5-qtxmlpatterns, qt5ct, and xorg-x11-server), Mageia (binutils, gstreamer1.0-plugins-bad, libsoup, libsoup3, mediawiki, net-tools, and tigervnc, x11-server, and x11-server-xwayland), Red Hat (tigervnc), SUSE (aws-efs-utils, fetchmail, flake-pilot, ImageMagick, java-1_8_0-ibm, java-1_8_0-openjdk, kernel-devel, kubecolor, OpenSMTPD, sccache, tiff, and zellij), and Ubuntu (linux, linux-aws, linux-aws-6.14, linux-gcp, linux-gcp-6.14, linux-oem-6.14, linux-oracle, linux-oracle-6.14, linux-raspi, linux-realtime, linux, linux-aws, linux-gkeop, linux-hwe-6.8, linux-ibm, linux-ibm-6.8, linux-lowlatency, linux-lowlatency-hwe-6.8, linux-nvidia, linux-nvidia-lowlatency, linux, linux-aws, linux-kvm, linux-lts-xenial, linux-oracle-6.8, linux-realtime-6.14, poppler, python-django, and various linux-* packages).
Removing XSLT from Chromium
Mason Freed and Dominik Röttsches have published a document with a timeline and plans for removing Extensible Stylesheet Language Transformations (XSLT) from the Chromium project and Chrome browser:
Chromium has officially deprecated XSLT, including the XSLTProcessor JavaScript API and the XML stylesheet processing instruction. We intend to remove support from version 155 (November 17, 2026). The Firefox and WebKit projects have also indicated plans to remove XSLT from their browser engines. This document provides some history and context, explains how we are removing XSLT to make Chrome safer, and provides a path for migrating before these features are removed from the browser.
LWN covered the Web Hypertext Application Technology Working Group (WHATWG) discussion about XSLT in August.
LXQt 2.3.0 released
Version 2.3.0 of the Lightweight Qt Desktop Environment (LXQt) has been released. The highlight of this release is continued improvement in Wayland support across LXQt components. Rather than offering its own compositor, the LXQt project takes a modular approach and works with several Wayland compositors, such as KWin, labwc, and niri.
OCI Runtime Specification 1.3 adds FreeBSD
Version
1.3 of the Open Container Initiative (OCI) Runtime
Specification has been released. The specification covers the
configuration, execution environment, and lifecycle of containers. The
most notable change in 1.3 is the addition of FreeBSD to the
specification, which the FreeBSD Foundation calls
"a watershed moment for FreeBSD
":
The addition of cloud-native container support complements FreeBSD's already robust virtualization capabilities, particularly the powerful FreeBSD jails technology that has been a cornerstone of the operating system for over two decades. In fact, OCI containers on FreeBSD are implemented using jails as the underlying isolation mechanism, bringing together the security and resource management benefits of jails with the portability and ecosystem advantages of OCI-compliant containers.
Security updates for Wednesday
Security updates have been issued by Debian (bind9 and gimp), Fedora (chromium, fastapi-cli, fastapi-cloud-cli, gherkin, libnbd, maturin, openapi-python-client, python-annotated-doc, python-cron-converter, python-fastapi, python-inline-snapshot, python-jiter, python-openapi-core, python-platformio, python-pydantic, python-pydantic-core, python-pydantic-extra-types, python-rignore, python-starlette, python-typer, python-typing-inspection, python-uv-build, ruff, rust-astral-tokio-tar, rust-attribute-derive, rust-attribute-derive-macro, rust-collection_literals, rust-get-size-derive2, rust-get-size2, rust-interpolator, rust-jiter, rust-manyhow, rust-manyhow-macros, rust-proc-macro-utils, rust-quote-use, rust-quote-use-macros, rust-regex, rust-regex-automata, rust-reqsign, rust-reqsign-aws-v4, rust-reqsign-command-execute-tokio, rust-reqsign-core, rust-reqsign-file-read-tokio, rust-reqsign-http-send-reqwest, rust-serde_json, rust-speedate, rust-tikv-jemalloc-sys, rust-tikv-jemallocator, and uv), Mageia (golang and libavif), Red Hat (bind9.16, pcs, and qt6-qtsvg), SUSE (colord, ffmpeg, govulncheck-vulndb, jasper, openjpeg, poppler, qatengine, qatlib, runc, sccache, and tiff), and Ubuntu (keystone, libssh, linux-hwe-6.14, linux-nvidia-tegra, linux-nvidia-tegra-5.15, linux-nvidia-tegra-igx, linux-raspi, runc-app, runc-stable, squid, squid3, and unbound).
Incus 6.18 released
Version 6.18 of the Incus container and virtual-machine management system has been released. Notable changes in this release include new configuration keys for providing credentials to systemd, BPF token delegation, VirtIO support for sound cards, the ability to export ISO volumes, improvements to the IncusOS command-line utility, and more.
Security updates for Tuesday
Security updates have been issued by Debian (dcmtk, geographiclib, gimp, pure-ftpd, and ruby-rack), Fedora (dotnet9.0), Oracle (expat, kernel, tigervnc, xorg-x11-server, and xorg-x11-server-Xwayland), Red Hat (git, mariadb:10.5, multiple packages, osbuild-composer, pcs, sssd, and tigervnc), SUSE (kernel and redis), and Ubuntu (google-guest-agent).
CHERIoT 1.0 released
Version 1.0 of the Capability Hardware Extension to RISC-V for IoT (CHERIoT) specification has been released. CHERIoT is a hardware-software system for secure embedded devices, and the specification provides a full description of the ISA and its intended use by CHERIoT RTOS. David Chisnall has written a blog post about the release that explains its significance as well as plans for CHERIoT 2.0 and beyond:
The last change that we made to the ISA was in December 2024, so we are confident that this is a stable release that we can support in hardware for a long time. This specification was implemented by the 1.0 release of CHERIoT Ibex and by CHERIoT Kudu (which has not yet had an official release). These two implementations demonstrate that the ISA scales from three-stage single-issue pipelines to six-stage dual-issue pipelines, roughly the same range of microarchitectures supported by Arm's M profile.
We at SCI have the first of our ICENI chips, which use the CHERIoT Ibex core, on the way back from the fab now and will be scaling up to mass production in the new year. I am not allowed to speak for other folks building CHERIoT silicon, but I expect 2026 to be an exciting year for the CHERIoT project!