Direct memory access (DMA) I/O is simple in concept: a peripheral device moves data directly to or from memory while the CPU is busy doing other things. As is so often the case, DMA is rather more complicated in practice, and the kernel has developed a complicated internal API to support it. It turns out that the DMA API, as it exists now, can affect the performance of some high-bandwidth devices. In an effort to address that problem, Leon Romanovsky is making the API even more complex with this patch series adding a new two-step mapping API.

A new batch of stable kernels has just been released: 6.11.8, 6.6.61, 6.1.117, and 5.15.172. As usual, they contain important fixes throughout the kernel tree.

Security updates have been issued by Fedora (llama-cpp, mingw-expat, python3.6, webkit2gtk4.0, and xorg-x11-server-Xwayland), Mageia (java-1.8.0-openjdk, java-11-openjdk, java-17-openjdk, java-21-openjdk & java-latest-openjdk and libarchive), Oracle (expat, gstreamer1-plugins-base, kernel, libsoup, podman, and tigervnc), SUSE (buildah, java-1_8_0-openjdk, and switchboard-plug-bluetooth), and Ubuntu (zlib).

The LWN.net Weekly Edition for November 14, 2024 is available.

Programming language polyglots are files that are valid programs in multiple languages, and do different things in each. While polyglots are normally nothing more than a curiosity, the Cosmopolitan Libc project has been trying to put them to a novel use: producing native, multi-platform binaries that run directly on several operating systems and architectures. There are still some rough edges with the project's approach, but it is generally possible to build C programs into a polyglot format with with minimal tweaking.

Security updates have been issued by AlmaLinux (expat), Fedora (chromium and golang-github-nvidia-container-toolkit), Mageia (curl, expat, mpg123, networkmanager-libreswan, openssl, php-tcpdf, qbittorrent, and x11-server, x11-server-xwayland, and tigervnc), Red Hat (kernel and libsoup), Slackware (mozilla), SUSE (firefox, kernel, python-PyPDF2, and xen), and Ubuntu (dotnet9, ghostscript, linux-aws, linux-oem-6.8, and pydantic).

Over the years, there has been steady progress in adding security features to compilers and other tools to assist with hardening the Linux kernel (and, of course, other programs). In something of a tradition in the toolchains track at the Linux Plumbers Conference, Kees Cook and Qing Zhao have led a session on that progress and further plans; this year, they were joined by Justin Stitt (YouTube video).

Garrett LeSage has written an in-depth article for Fedora Magazine about a new web-based user interface (UI) for Fedora's Anaconda installer, planned to ship with Fedora 42. The article looks at the rationale for moving from GTK 3 to a web-based UI, provides a number of screenshots and demo screencasts, as well as instructions on trying out the new installer with Fedora Rawhide.

Security updates have been issued by AlmaLinux (gstreamer1-plugins-base), Debian (chromium, ghostscript, libarchive, mpg123, ruby-saml, and symfony), Fedora (buildah and podman), Red Hat (buildah, containernetworking-plugins, podman, skopeo, and xorg-x11-server-Xwayland), Slackware (wget), SUSE (pcp), and Ubuntu (linux, linux-aws-5.15, linux-gcp, linux-gcp-5.15, linux-gke, linux-gkeop, linux-gkeop-5.15, linux-hwe-5.15, linux-ibm, linux-ibm-5.15, linux-kvm, linux-lowlatency, linux-lowlatency-hwe-5.15, linux-nvidia, linux-oracle, linux-oracle-5.15, linux-raspi, linux-xilinx-zynqmp and mysql-8.0).

What have been the most significant security-related incidents for the open-source community in 2024 (so far)? Marta Rybczyńska recently ran a poll and got some interesting results. At the 2024 Open Source Summit Japan, she presented those results along with some commentary of her own. The events in question are unlikely to be a surprise to LWN readers, but the overall picture that was presented was worth a look.

Longtime Debian and Tor developer, Jérémy Bobbio—perhaps better known as "Lunar"—died on November 8. Lunar was one of the founders of the reproducible builds movement and more recently had been working with Software Heritage. More information and tributes in French can be found at this site. They will be missed.

Security updates have been issued by AlmaLinux (podman), Debian (guix, libarchive, and nss), Fedora (expat, iaito, opendmarc, python-werkzeug, radare2, squid, and xorg-x11-server), Mageia (htmldoc, libheif, nspr, nss, firefox & rust, python-urllib3, python-werkzeug, quictls, ruby-webrick, and thunderbird), Oracle (firefox and NetworkManager-libreswan), SUSE (apache2, chromedriver, chromium, coredns, expat, govulncheck-vulndb, httpcomponents-client, java-17-openjdk, java-21-openjdk, libheif, python-wxPython, python311, python312, qbittorrent, ruby3.3-rubygem-actionmailer, ruby3.3-rubygem-actiontext, ruby3.3-rubygem-puma, ruby3.3-rubygem-rails, and virtualbox), and Ubuntu (openjdk-17, openjdk-21, openjdk-8, openjdk-lts, and qemu).

Linus has released 6.12-rc7 for testing. "No big surprises, and I think everything is on track for a final 6.12 release next weekend."

Back In Time is a GPL-2.0-licensed backup tool based on rsync and written in Python. It has both graphical and command-line interfaces, and supports backups to local disks or over SSH. Back In Time was originally written by Oprea Dan and released in 2009. The tool has been through some rough patches over the years, and is currently on its third set of maintainers. Christian Buhtz, one of the current maintainers, explained to me how he and his co-maintainers had revived the project, as well as why he thought Back In Time stood out from all of the existing backup solutions.

Greg Kroah-Hartman has shared another seven stable kernel updates: 6.6.60, 6.11.7, 6.1.116, 5.15.171, 5.10.229, 5.4.285, and 4.19.323.

Fedora Linux, as a rule, handles version upgrades reasonably well. However, there are times when users may want to do a fresh installation rather than an upgrade but preserve existing users and data under /home. This is a scenario that the Fedora installer, currently, does not address. Users can maintain a separate /home partition, of course, but the installer does not incorporate existing users into the new install—that is an exercise left to the user to handle. One solution might be to use systemd-homed, a systemd service for managing users and home directories. However, a discussion proposing the use systemd-homed as part of Fedora installation uncovered some hurdles, such as trying to blend its approach to managing users with tools that centralize user management.

Arthur Cohen has posted a detailed introduction to the gccrs project on the Rust Blog, seemingly with the goal of convincing the Rust community about the value of the project.

Likewise, many GCC plugins are used for increasing the safety of critical projects such as the Linux kernel, which has recently gained support for the Rust programming language. This makes gccrs a useful tool for analyzing unsafe Rust code, and more generally Rust code which has to interact with existing C code. We also want gccrs to be a useful tool for rustc itself by helping pan out the Rust specification effort with a unique viewpoint - that of a tool trying to replicate another's functionality, oftentimes through careful experimentation and source reading where the existing documentation did not go into enough detail.

(LWN last looked at gccrs in October).

Security updates have been issued by AlmaLinux (edk2), Debian (webkit2gtk), Fedora (thunderbird), Oracle (bzip2, container-tools:ol8, edk2, go-toolset:ol8, libtiff, python-idna, python3.11, and python3.12), Slackware (expat), and SUSE (apache2, govulncheck-vulndb, grub2, java-1_8_0-openjdk, python3, python39, qemu, xorg-x11-server, and xwayland).

Flexible arrays — arrays that are declared as the final member of a structure and which have a size determined at run time — have long drawn the attention of developers seeking to harden the kernel against buffer-overflow vulnerabilities. These arrays have reliably been a source of bugs, so anything that can be done to ensure that operations on them stay within bounds is a welcome improvement. While many improvements, including the recent counted-by work, have been made, one of the most difficult cases remains. Now, however, developers who are interested in using recent compiler bounds-checking features are trying to get a handle on struct sockaddr.

Security updates have been issued by AlmaLinux (bcc, bpftrace, bzip2, container-tools:rhel8, grafana-pcp, haproxy, kernel, kernel-rt, krb5, libtiff, python-gevent, python3.11, python3.11-urllib3, python3.12, python3.12-urllib3, xmlrpc-c, and xorg-x11-server and xorg-x11-server-Xwayland), Debian (puma and pypy3), Fedora (firefox), Gentoo (libgit2), Mageia (libarchive), SUSE (ghostscript, go1.22-openssl, go1.23-openssl, htmldoc, kmail-account-wizard, libarchive, libgsf, libmozjs-128-0, openssl-3, python-jupyterlab, python-mysql-connector-python, python36, and ruby2.1), and Ubuntu (cinder, linux-aws, linux-aws-6.8, linux-oracle, linux-oracle-6.8, linux-aws, linux-azure-5.4, linux-kvm, linux-oracle, linux-xilinx-zynqmp, and linux-nvidia, linux-nvidia-6.8, linux-nvidia-lowlatency).