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There are some "magic links" in kernel pseudo-filesystems, like procfs,that can be—have been—(ab)used to cause security problems, such as acontainer-confinement breach in 2019.Aleksa Sarai has long been working on ways to blunt the impact of thesemagic links. He led a filesystem session at the2023 Linux Storage, Filesystem,Memory-Management and BPF Summit to discuss the status of those efforts.

The6.3.8,6.1.34,5.15.117,5.10.184,5.4.247,4.19.286, and4.14.318stable kernel updates have all been released; each contains another set ofimportant fixes.

Security updates have been issued by Debian (ffmpeg, owslib, php7.4, and php8.2), Fedora (ntp-refclock, php, and python3.7), Red Hat (c-ares, firefox, and thunderbird), SUSE (kernel, openldap2, and tomcat), and Ubuntu (binutils, dotnet6, dotnet7, node-fetch, and python-tornado).

There has long been a desire to enable users to mount filesystem images withoutrequiring privileges, but the securityimplications of allowing it are seriously concerning. Few, if any, kernelfilesystems are hardened against maliciously crafted images, after all.Lennart Poettering led a filesystem session at the 2023 Linux Storage, Filesystem,Memory-Management and BPF Summit where he presented a possible pathforward.

The fifth conference on PowerManagement and Scheduling in the Linux Kernel (abbreviated "OSPM") washeld on April 17 to 19 in Ancona, Italy. LWN was not there,unfortunately, but the attendees of the event have gotten together to writeup summaries of the discussions that took place and LWN has the privilegeof being able to publish them. Reports from the first day of the eventappear below.

Paul McKenney has announced a newversion of his book IsParallel Programming Hard, And, If So, What Can You Do About It?.

Videosfrom the 2022 Tracing Summit are now available on YouTube. Theyinclude talks about Visual eBPF, Perfetto, the state of Linux tracers,libpatch, hardware trace, and more.

Security updates have been issued by Debian (vim), Fedora (kernel), Oracle (emacs, firefox, python3, and qemu), SUSE (firefox, java-1_8_0-ibm, and libwebp), and Ubuntu (firefox, glusterfs, and sniproxy).

The Fedora project has posted the results of its elections for members oftheFedoraEngineering Steering Committee (Stephen Gallagher, Neal Gompa, MajorHayden, and Tom Stellard),FedoraCouncil (Sumantro Mukherjee), and MindshareCommittee (David Duncan).

The CPU scheduler's one job at any given time is to run the task that hasthe strongest claim to the CPU. There are many factors that complicatethat job, not the least of which is that the "strongest claim" is sometimesa bit of a fuzzy concept. Realtime throttling, a mechanism designed tokeep a runaway realtime task from monopolizing the CPU, is one case wheredevelopers have concluded that the task with, ostensibly, the highestpriority should not actually be the one that runs. But realtime throttlinghas rarely pleased anybody; the deadline-serverinfrastructure patches posted by Daniel Bristot de Oliveira are thelatest attempt to find a better solution.

Security updates have been issued by Debian (pypdf2 and thunderbird), Fedora (chromium, dbus, mariadb, matrix-synapse, sympa, and thunderbird), Scientific Linux (python and python3), SUSE (chromium, gdb, and openldap2), and Ubuntu (jupyter-core, requests, sssd, and vim).

The 6.4-rc6 kernel prepatch is out fortesting.

"After 1 year, 9 months, and 28 days of development", Debian 12, codenamed "bookworm", has been released. The announcement has lots of details about package versions for desktop environments (6 are supported), kernel version (Linux 6.1 series), other package versions (compilers, graphics tools, office suites, languages, and more), architectures supported (8 for real hardware and 5 for cloud services), blends, and lots more.

Two different topics concerning the virtual filesystem (VFS) layer were thesubject of a session led by VFS co-maintainer Christian Brauner at the2023 Linux Storage, Filesystem,Memory-Management and BPF Summit. As might be guessed, it was afilesystem-track session; Brauner had three separate items he planned onbringing up, but the discussion on the first two consumed the wholehalf-hour—and then some. A mechanism to avoid media-change races whenmounting loop (or loopback) and other devices was disposed of fairlyquickly, but the discussion around the mount-beneath feature went on at length.

Priority inversion comes about when a low-priority task holds a resourcethat is needed by a higher-priority task, with the result that the wrongtask is the only one that can run. This problem is arguably most acute inrealtime settings, but it can happen in just about any system that hasmultiple tasks running. The variety ofscheduling classes provided by the Linux kernel make handling priorityinversion a difficult problem; the latest version of the proxyexecution patch series points toward a possible solution.

Greg Kroah-Hartman has released the 6.3.7,6.1.33, 5.15.116, 5.10.183, 5.4.246, 4.19.285, and 4.14.317 stable kernels. As usual, theycontain many important fixes throughout the tree; users of those seriesshould upgrade.

Security updates have been issued by Debian (jupyter-core, openssl, and ruby2.5), Fedora (firefox), Mageia (libreoffice, openssl, and python-flask), Red Hat (python and python3), Slackware (mozilla, php8, and python3), SUSE (java-1_8_0-ibm, libcares2, mariadb, and python36), and Ubuntu (linux, linux-aws, linux-kvm, linux-lts-xenial, linux-gke, linux-intel-iotg, linux-raspi, linux-xilinx-zynqmp, and mozjs102).

The kernel is an increasingly dynamic body of code, where new executabletext can show up at any time. Currently, the task of allocating memory fornew kernel code falls on the subsystem that first brought the ability toload code into a running kernel: the module loader. This patchset from Mike Rapoport looks to move the responsibility for theseallocations to a new "JIT allocator", addressing a number of rough edges inthe process.

Security updates have been issued by Debian (chromium, firefox-esr, and ruby2.5), Fedora (curl, dbus, pypy, pypy3.8, pypy3.9, python3.10, and python3.8), Red Hat (python and python-flask), Scientific Linux (emacs), SUSE (firefox, google-cloud-sap-agent, libwebp, opensc, openssl, openssl-3, openssl1, python-sqlparse, python310, and supportutils), and Ubuntu (libxml2, netatalk, and sysstat).

The LWN.net Weekly Edition for June 8, 2023 is available.

Gao Xiang gave an overview of the Extended Read-Only FileSystem (EROFS) in a filesystem session at the2023 Linux Storage, Filesystem,Memory-Management and BPF Summit. EROFS was addedto Linux 5.4 in 2019 and has been increasingly used inplaces beyond its roots as a filesystem for Android and embedded devices.Container images based on EROFS are being used in many places these days, for example.

At the end of our February article aboutthe debate around the composefs read-only,integrity-protected filesystem, it was predicted that the topic would come up at the2023 Linux Storage, Filesystem,Memory-Management and BPF Summit. That happened on the second day ofthe summit whenAlexander Larsson led a session on composefs. While the mailing-listdiscussion was somewhat contentious, the session was less so, since overlayfs canbe made to fit the needs of the composefs use cases. It turnsout that an entirely newfilesystem is not really needed.

Version15.5 of the openSUSE Leap distribution has been released. This is notintended as a feature release, but brings updated versions of manypackages. The project has also announcedthat there will be one more 15.x release before that series ends and usershave to migrate to whatever its successor will be.

Security updates have been issued by Debian (c-ares), Fedora (curl and firefox), Oracle (cups-filters, kernel, and webkit2gtk3), Red Hat (emacs and kpatch-patch), Slackware (mozilla), SUSE (kernel and openssl-1_0_0), and Ubuntu (firefox and libreoffice).

Margaret Mitchell, a researcher focused on the intersection of machinelearning and ethics, was the morning keynote speaker on the third day of PyCon 2023. She spoke about herjourney into machine learning and how the Python language has beeninstrumental in it. It was a timely and thought-provoking talk that lookedbeyond the machine-learning hype to consider the bigger picture.

Security updates have been issued by Debian (linux-5.10), Red Hat (cups-filters, curl, kernel, kernel-rt, kpatch-patch, and webkit2gtk3), SUSE (apache-commons-fileupload, openstack-heat, openstack-swift, python-Werkzeug, and openstack-heat, python-Werkzeug), and Ubuntu (frr, go, libraw, libssh, nghttp2, python2.7, python3.10, python3.11, python3.5, python3.6, python3.8, and xfce4-settings).

At the2023 Linux Storage, Filesystem,Memory-Management and BPF Summit, Luis Chamberlain led a plenarysession on kernel support for block sizes larger than 4KB. There areassumptions in the current kernel that the block size used by a block-layerdevice is less than or equal to the system's page size—both are usually 4KBtoday. But there have been efforts over the years to remove thatrestriction; that work may be heading toward fruition, in part because ofthe folio efforts of late, though there arestill lots of areas that need attention.

The 6.3.6, 6.1.32, 5.15.115, 5.10.182, and 5.4.245 stable kernels have been released.They contain a relatively small number of important fixes throughout thekernel tree.

Developers learning the Unix (or POSIX in general) system-call set willquickly encounter file descriptors, which are used to represent open filesand more. Developers also tend to learn early on that the first three filedescriptors are special, with file descriptor zero being the standard inputstream, one being standard output, and two being standard error. Thekernel, though, does not normally attach any specific meaning to a givendescriptor number, so it was somewhat surprising when a recent BPF patchseries attempted to attach a special meaning to zero when used as a filedescriptor.

Security updates have been issued by Debian (chromium, cpio, mariadb-10.3, nbconvert, sofia-sip, and wireshark), Fedora (ImageMagick, mingw-python-requests, openssl, python3.6, texlive-base, and webkitgtk), Red Hat (apr-util, git, gnutls, kernel, kernel-rt, and kpatch-patch), Slackware (cups and ntp), and Ubuntu (linux-azure-fde, linux-azure-fde-5.15 and perl).

Linus has released 6.4-rc5 for testing.

Red Hat's Matthias Clasen has letit be known that LibreOffice will be dropped from a future Red HatEnterprise Linux release, and the future of its support in Fedora isunclear as well.

As the 2023 Linux Storage, Filesystem,Memory-Management and BPF Summit neared its conclusion, two sessionswere held in the memory-management track on process-oriented topics. MikeRapoport ran a session on memory-management documentation (or the lackthereof), while Andrew Morton talked about the state of the subsystem'sdevelopment process in general. Both sessions were relatively brief and didnot foreshadow substantial changes to come.

Security updates have been issued by Debian (cups and netatalk), SUSE (cups, ImageMagick, installation-images, libvirt, openvswitch, and qemu), and Ubuntu (avahi, cups, linux, linux-aws, linux-aws-hwe, linux-azure, linux-azure-4.15, linux-gcp, linux-gcp-4.15, linux-hwe, linux-kvm, linux-oracle, linux-snapdragon, linux, linux-aws, linux-azure, linux-azure-5.4, linux-gcp, linux-gcp-5.4, linux-gke, linux-gkeop, linux-hwe-5.4, linux-ibm, linux-ibm-5.4, linux-kvm, linux-oracle, linux-oracle-5.4, linux-aws-5.4, linux-bluefield, linux-intel-iotg, and linux-intel-iotg-5.15).

Version1.70.0 of the Rust language is out. Changes include enabling the"sparse" protocol for Cargo, a couple of new types for the initializationof shared data, and more. "You should see substantially improvedperformance when fetching information from the crates.io index."

Like most other distributions, the Debian project decided to end theseparation between the root and /usr filesystems years ago.Unlike most others, though, Debian is still working on the implementationof this decision. The upcoming Debian 12 ("bookworm") release willfeature a merged /usr in most respects, but there are a couple ofnagging issues that threaten to stretch this transition out for some timeyet.

A new version of NixOS, which is a Linuxdistribution based on the Nix packagemanager, has been released: NixOS 23.05is now available. The releasenotes list numerous updates, including Nix 2.13, Linux 6.1,glibc 2.37, Cinnamon 5.6, GNOME 44, and KDE Plasma 5.27.

Security updates have been issued by Debian (libwebp, openssl, sssd, and texlive-bin), Fedora (bitcoin-core, editorconfig, edk2, mod_auth_openidc, pypy, pypy3.9, python3.10, and python3.8), Red Hat (kernel, openssl, pcs, pki-core:10.6, and qatzip), SUSE (chromium, ImageMagick, openssl-1_1, and tiff), and Ubuntu (cups, libvirt, and linux, linux-aws, linux-aws-5.15, linux-azure, linux-azure-5.15, linux-gcp, linux-gcp-5.15, linux-gke, linux-gke-5.15, linux-gkeop, linux-hwe-5.15, linux-hwe-5.19, linux-ibm, linux-kvm, linux-lowlatency, linux-lowlatency-hwe-5.15, linux-oracle, linux-oracle-5.15, linux-raspi).

The LWN.net Weekly Edition for June 1, 2023 is available.

The code-tagging mechanism proposed lastyear by Suren Baghdasaryan and Kent Overstreet has been the subject of anumber of (sometimes tense) discussions. That conversation came to thememory-management track at the 2023 LinuxStorage, Filesystem, Memory-Management and BPF Summit, where itsdevelopers (Baghdasaryan attending in-person and Overstreet remotely) triedto convince the attendees that its benefits justify its cost.

David Malcolm writesabout a number of new features that have been added to the staticanalyzer in the GCC 13 release.

Security updates have been issued by Debian (connman and kamailio), Fedora (texlive-base), Mageia (cups-filters, postgresql, qtbase5, tcpreplay, tomcat, and vim), Slackware (openssl), SUSE (amazon-ssm-agent, cni, cni-plugins, compat-openssl098, installation-images, libaom, openssl, openssl-1_0_0, openssl-1_1, terraform, terraform-provider-helm, tiff, tomcat, and wireshark), and Ubuntu (batik, flask, linux-oem-5.17, linux-oem-6.0, linux-oem-6.1, linux-oracle, linux-oracle-5.4, mozjs102, nanopb, openssl, openssl1.0, snapd, and texlive-bin).

The6.3.5,6.1.31,5.15.114,5.10.181,5.4.244,4.19.284, and4.14.316stable kernels have all been released; each contains another set ofimportant fixes.

Martin Petersen and John Garry led a session at the2023 Linux Storage, Filesystem,Memory-Management and BPF Summit on work they have been doing toimplement atomic block writes of various sizes for SCSI and NVMe. The idea is to support devices that can guarantee atomic operations forsizes larger than their block size. It isan attempt to "find common ground" between the two standards, Petersen said, because the twohave slightly different semantics, depending on the device type, anddifferent restrictions, which has made for an "interesting project". It hasbeen a challenge to find an abstraction layer that can work with the "fivedifferent variants of SCSI and NVMe implementations that may or may not be out there".

Security updates have been issued by Debian (libssh and sssd), Fedora (microcode_ctl and python3.6), Gentoo (cgal, firefox firefox-bin, openimageio, squashfs-tools, thunderbird thunderbird-bin, tiff, tomcat, webkit-gtk, and xorg-server xwayland), SUSE (c-ares and go1.18-openssl), and Ubuntu (Jhead, node-hawk, node-nth-check, and perl).

The Rust community has experienced some turbulence in response to thecancellation of a keynote talk at the upcoming RustConf event. TheRust project leadership has now put out a blog postapologizing for and explaining its role in the event, describing its"decision-making and communication processes" as the primary causeof the failure.

Thanks to an LWN comment from "engla", we have learned that the videos from the recently completed 2023 Linux Storage, Filesystem,Memory-Management and BPF Summit are now available on YouTube. LWN sat in on many of the talks, of course, and we are still chugging along on our coverage of the conference.

Version 1.9 of Julia, which is anopen-source programming language popular in scientific computing, was releasedin early May. There are a number of interesting new features this timearound, including more work addressing thestartup-time complaints and a number of improvements to the package system.Beyond that, there are a few interesting features from the Julia 1.8 releaseto catch up on.

Aseries of blog posts from the 2023 Python Language Summit has beenposted; topics covered include the C API, the global interpreter lock,the standard library, and a talk on burnout from Guido van Rossum:

Certain topics return predictably to development conferences every year,usually because developers are still struggling to find a viable solutionto a specific problem. One such topic is the lack of scalability in thekernel's page-fault-handling code, so it was no surprise to see thisproblem on the agenda for the 2023 LinuxStorage, Filesystem, Memory-Management and BPF Summit. Matthew Wilcoxled a session in the memory-management track to discuss the state ofpage-fault handling and what can be done to improve it further.