Linux Weekly News

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.

Security updates have been issued by Debian (libreoffice), Fedora (exim and fscrypt), Red Hat (kernel), Slackware (mozilla), SUSE (docker, firefox, and podman), and Ubuntu (linux, linux-lowlatency, linux-lowlatency-hwe-5.15, linux, linux-lowlatency, linux-lowlatency-hwe-6.8, linux, linux-oem-6.11, linux-aws, linux-aws-6.8, linux-oracle, linux-oracle-6.8, linux-raspi, linux-aws, linux-gcp, linux-hwe-6.11, linux-oracle, linux-raspi, linux-realtime, linux-aws, linux-gkeop, linux-ibm, linux-intel-iotg, linux-intel-iotg-5.15, linux-oracle, linux-oracle-5.15, linux-raspi, and linux-gcp, linux-gcp-6.8, linux-gke, linux-gkeop).

Mozilla's actions have been rubbing many Firefox fans the wrong way as of late, and inspiring them to look for alternatives. There are many choices for users who are looking for a browser that isn't part of the Chrome monoculture but is full-featured and suitable for day-to-day use. For those who are willing to stay in the Firefox "family" there are a number of good options that have taken vastly different approaches. This includes GNU IceCat, Floorp, LibreWolf, and Zen.

Version 136.0 of the Firefox browser has been released. Changes include a new vertical tab layout, an automatic attempt to upgrade HTTP connections to HTTPS, support for AMD GPUs on Linux, an Arm64 port for Linux, and more.

Version 6.10 of the Incus container-management system has been released. New features include better Let's Encrypt support, API-wide filtering, IOMMU support in virtual machines, and more. See this announcement for details.

Security updates have been issued by AlmaLinux (kernel), Mageia (x11-server), Red Hat (emacs and webkit2gtk3), SUSE (ffmpeg-7, govulncheck-vulndb, kernel, and skopeo), and Ubuntu (cmark-gfm, erlang, krb5, linux-gcp-6.8, linux-raspi, linux-kvm, lucene-solr, postgresql-12, postgresql-14, postgresql-16, raptor2, spip, tomcat7, and wpa).

Mozilla has issued an update to its terms of use (TOU) that were announced on February 26. It has removed a reference in the TOU to Mozilla's Acceptable Use Policy "because it seems to be causing more confusion than clarity", and has revised the TOU "to more clearly reflect the limited scope of how Mozilla interacts with user data". The new language says:

You give Mozilla the rights necessary to operate Firefox. This includes processing your data as we describe in the Firefox Privacy Notice. It also includes a nonexclusive, royalty-free, worldwide license for the purpose of doing as you request with the content you input in Firefox. This does not give Mozilla any ownership in that content.

Mozilla has also updated its Privacy FAQ to provide more detail about its reasons for the changes.

One of the many new features packed into the 6.13 kernel release was guard pages, a hardening mechanism that makes it possible to inject zero-access pages into a process's address space in an efficient way. That feature only supports anonymous (user-space data) pages, though. To make guard pages more widely useful, Lorenzo Stoakes has put together a patch set enabling the feature for file-backed pages as well; in the process, he examined and resolved a long list of potential problems that extending the feature could encounter. One potential problem was not on his list, though.

Security updates have been issued by Debian (ffmpeg, kernel, linux-6.1, mariadb-10.5, proftpd-dfsg, and xorg-server), Fedora (chromium, cutter-re, iniparser, nodejs22, rizin, webkitgtk, wireshark, xen, and xorg-x11-server), Mageia (binutils and ffmpeg), Oracle (emacs and kernel), Red Hat (emacs and webkit2gtk3), SUSE (azure-cli, bsdtar, gnutls, govulncheck-vulndb, libX11, libxkbfile, libxml2, nodejs-electron, openssh8.4, ovmf, phpMyAdmin, python, python-azure-identity, python311-jupyter-server, tiff, trivy, u-boot, and wireshark), and Ubuntu (opennds and Ruby SAML).

The 6.14-rc5 kernel prepatch is out for testing. "Nothing looks particularly big or worrisome".

Differences of opinion, as well as outright disputes, between upstream open-source projects and Linux distribution packagers over packaging practices are nothing new. It is rarer, though, for those disputes to boil over to threats of legal action—but a disagreement between the Open Broadcaster Software (OBS) Studio project and Fedora packagers reached that point in mid-February. After escalation to a higher authority, things have been worked out to the satisfaction of the OBS project, but some lingering questions remain. How Fedora should prioritize Flatpak repositories, how to handle conflicts between upstreams and Fedora packagers, and the mechanics of removing or retiring Flatpaks all remain open questions.

There is a fair amount of unhappiness on the Internet about the announcement from Mozilla about a new "terms of use" agreement and an updated privacy notice for the Firefox browser.

Firefox will always continue to add new features, improve existing ones, and test new ideas. We remain dedicated to making Firefox open source, but we believe that doing so along with an official Terms of Use will give you more transparency over your rights and permissions as you use Firefox. And actually asking you to acknowledge it is an important step, so we're making it a part of the standard product experience starting in early March for new users and later this year for existing ones.

Specifically, the apparent removal of a promise to not sell users' personal data has drawn attention.

(See also: this analysis by Michael Taggart. "So, is this Mozilla 'going evil?' Nah, prolly not. But it is at best clumsy, and a poor showing if they want me to believe they care about Firefox, rather than the data it can provide".)