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The Fedora project may have managed to shake off its reputation for delayedreleases in recent years, but that hasn't stopped the release date forFedora 34 from slippingone week to April 27. Modulo ahandful of bugs, though, this release is in its final form, so a lookat what is coming is warranted. Distribution releases, especially thosefor fast-moving community distributions, are a good point at which to catchup with the state of many free-software projects and where Linux is headedin general. Fedora 34 includes a lot of changes, including the GNOME 40 release but, for the mostpart, it looks like an exercise in continuity.

Security updates have been issued by Debian (xorg-server), Fedora (kernel), openSUSE (clamav, fluidsynth, python-bleach, spamassassin, and xorg-x11-server), Red Hat (gnutls and nettle, libldb, and thunderbird), Scientific Linux (thunderbird), SUSE (clamav, util-linux, and xorg-x11-server), and Ubuntu (network-manager and underscore).

The Google security blog has adetailed article on what a device driver written in Rust looks like."That is, we use Rust's ownership discipline when interacting with Ccode by handing the C portion ownership of a Rust object, allowing it tocall functions implemented in Rust, then eventually giving ownershipback. So as long as the C code is correct, the lifetime of Rust fileobjects work seamlessly as well, with the compiler enforcing correctlifetime management on the Rust side, for example: open cannot returnstack-allocated pointers or heap-allocated objects containing pointers tothe stack, ioctl/read/write cannot free (ormodify without synchronization) the contents of the object stored in filp->private_data, etc."

The LWN.net Weekly Edition for April 15, 2021 is available.

In early April, Fedora program manager Ben Cotton posteda proposal to use the distribution'sdebuginfodservers by default in Fedora 35. This feature would help developerswho are trying to debug or trace their programs using various tools, but who arelacking the source code and debugging symbols needed. The serverscan provide that data directly to the tools as needed, but there are somesecurity and privacy concerns to work through before turning the feature onby default.

The OpenStack cloud-infrastructure project has made its 23rd release, Wallaby. "The Wallaby release strengthens open infrastructure for cloud native applications with enhanced security and integration with other open source technologies. More than 17,000 code changes authored by over 800 contributors from 140 different organizations and 45 countries were merged into the release.In addition to delivering a wide range of improvements to the stable and reliable OpenStack core and its highly flexible project integration capabilities, Wallaby delivers security enhancements including fallback permissions and RBAC improvements in Ironic [bare-metal provisioning service], Glance [image service] and Manila [shared filesystems], and the community focused this cycle on migrating the RBAC policy format from JSON to YAML. Additionally, the Ironic project has extended functionality for UEFI (Unified Extensible Firmware Interface), including secure erase for NVME."

Stable kernels 5.11.14, 5.10.30, 5.4.112, and 4.19.187 have been released with importantfixes throughout the tree. Users should upgrade.

Security updates have been issued by CentOS (screen), Debian (clamav, courier-authlib, and tomcat9), Red Hat (thunderbird), SUSE (clamav, glibc, kernel, open-iscsi, opensc, spamassassin, thunderbird, wpa_supplicant, and xorg-x11-server), and Ubuntu (linux, linux-aws, linux-aws-5.4, linux-azure, linux-azure-5.4, linux-gcp, linux-gcp-5.4, linux-gke-5.4, linux-gkeop, linux-gkeop-5.4, linux-hwe-5.4, linux-kvm, linux-oracle, linux-oracle-5.4, linux-raspi, linux-raspi-5.4, linux, linux-aws, linux-aws-hwe, linux-azure, linux-azure-4.15, linux-dell300x, linux-gcp, linux-gcp-4.15, linux-kvm, linux-oracle, linux-raspi2, linux-snapdragon, linux, linux-aws, linux-azure, linux-gcp, linux-hwe-5.8, linux-kvm, linux-oracle, linux-raspi, linux, linux-aws, linux-kvm, linux-lts-xenial, linux-raspi2, linux-snapdragon, linux-oem-5.10, linux-oem-5.6, nettle, and xorg-server, xorg-server-hwe-16.04, xorg-server-hwe-18.04).

The FreeBSD 13 release is out. It includes a lot of updated software, theremoval of a number of GNU tools (including the toolchain), and more, butnot WireGuard. See the releasenotes for the details.

There are times when developers and system administrators need to diagnoseproblems in running code. The program to be examined can be a user-spaceprocess, the kernel, or both. Two of the major tools available on Linux toperform this sort of analysis areSystemTap andbpftrace. SystemTap has been availablesince 2005, while bpftrace is a more recent contender that, to some,may appear tohave made SystemTap obsolete. However, SystemTap is still the preferredtool forsome real-world use cases.

Security updates have been issued by Debian (libpano13), Fedora (mosquitto and perl-Net-CIDR-Lite), Mageia (curl, mongodb, pdfbox, python-jinja2, rygel, spamassassin, tor, velocity, webkit2, and wireshark), openSUSE (umoci), Oracle (389-ds:1.4, kernel, and virt:ol and virt-devel:rhel), Red Hat (kernel and kpatch-patch), Slackware (dnsmasq and irssi), and SUSE (cifs-utils, rubygem-actionpack-4_2, and spamassassin).

While some parts of the core kernel reached a relatively stable "done"state years ago, others never really seem to be finished. One of thelatter variety is undoubtedly the kernel's implementation of spinlocks,which arbitrate access to data at the lowest levels of the kernel. Lockperformance can have a significant effect on the performance of the systemas a whole, so optimization work can pay back big dividends. Lest onethink that this work is finally done, the NUMA-awareqspinlock patch set shows how some more performance can be squeezed outof the kernel's spinlock implementation.

The Free Software Foundation has finally issueda statement on why the decision to return Richard Stallman to theorganization's board of directors was taken.

Security updates have been issued by CentOS (kernel and libldb), Debian (mediawiki, qemu, ruby-kramdown, and xen), Fedora (grub2, libldb, libopenmpt, python-pikepdf, python39, samba, squid, and webkit2gtk3), openSUSE (bcc, ceph, gssproxy, hostapd, isync, kernel, openexr, openSUSE KMPs, and tpm2-tss-engine), SUSE (fwupdate and wpa_supplicant), and Ubuntu (spamassassin).

The 5.12-rc7 kernel prepatch is out; it'srather larger than Linus would have liked."End result: I'm still waffling about the final 5.12 release. The factthat we have a big rc7 does make me think that I'll probably do an rc8this time around. But it ends up depending a bit on how the upcomingweek goes, and if things are deathly quiet, I may end up deciding thatan rc8 doesn't really make sense."

There is another set of stable kernel updates out:5.11.13,5.10.29,5.4.111,4.19.186,4.14.230,4.9.266, and4.4.266.Each contains another set of important fixes.

HPVM ("heterogeneous parallelvirtual machine") is a compiler for targets like GPUs and FPGAs based onLLVM; the 1.0 release is available now. "This release is a major addition to our first release (version 0.5),adding support for linear algebra tensor operations, Pytorch andKeras frontends, approximations for convolution operators, and anefficient and flexible framework for approximation tuning. Our novelapproximation-tuner automatically selects approximation knobs forindividual tensor operations and selects configurations that maximizea (configurable) performance objective."

The seccomp()mechanism allows the imposition of a filter program (expressed in "classic" BPF)that makes policy decisions on whether to allow each system call invoked by the targetprocess. The user-space notificationfeature further allows those decisions to be deferred to anotherprocess. As this recentpatch set from Sargun Dhillon shows, though, user-space notificationstill has some rough edges, especially when it comes to signals. Thispatch makes a simple change to try to address a rather complex problembrought to the fore by changes in the Go language's preemption model.

Security updates have been issued by Debian (lib3mf, php-pear, and python-django), Fedora (perl-Net-Netmask), openSUSE (flatpak, libostree, xdg-desktop-portal,, fwupd, fwupdate, and hostapd), Oracle (kernel, libldb, nettle, and squid), Red Hat (nettle), and SUSE (fwupdate, tpm2-tss-engine, and umoci).

Richard Stallman's return to the FreeSoftware Foundation's board of directors has provoked a flurry of responses, and many organizations inthe free-software community have expressed their unhappiness with thatappointment. In almost every case, the process leading up to thatexpression has been carried out behind closed doors. The Debian project,instead, is deciding what to do in a classic Debian way — holding a publicvote on a general resolution with a wide range of possible outcomes.

Security updates have been issued by Fedora (chromium, libldb, rpm, samba, and seamonkey), openSUSE (isync), Oracle (kernel), Red Hat (openssl and squid), SUSE (ceph, flatpak, libostree, xdg-desktop-portal, xdg-desktop-portal-gtk, fwupd, fwupdate, and openexr), and Ubuntu (curl, linux-lts-trusty, and lxml).

The LWN.net Weekly Edition for April 8, 2021 is available.

Five years ago, we looked at an effort toassist in the assignment of CommonVulnerabilities and Exposures (CVE) IDs, especially for open-sourceprojects.Developers in the free-software world have often found it difficult toobtain CVE IDs for the vulnerabilities that they find.The Distributed WeaknessFiling (DWF) project was meant to reduce the friction in theCVE-assignment process, but it never really got off the ground. In a blogpost, Josh Bressers said that DWF was hampered by trying to follow therules for CVEs. That has led to a plan to restart DWF, but this time without the"yoke of legacy CVE".

Projects, even of the open-source variety, sometimes have secrets that needto be maintained. They can range from things like signing keys, which are(or should be) securely stored away from the project's code, to credentialsand tokens for access to various web-based services, such as cloud-hosting services or thePython Package Index (PyPI). These credentialsare sometimesneeded by instances of the running code, and some others benefit from beingstored "near" the code, but these types of credentials are not meant tobe distributed outside of the project.They can sometimes mistakenly be added to a public repository, however, which isa slip that attackers are most definitely on the lookout for.The big repository-hosting services like GitHuband GitLab are well-placed to scan for these kinds of secrets beingcommitted to project repositories—and they do.

Stable kernels 5.11.12, 5.10.28, 5.4.110, 4.19.185, 4.14.229, 4.9.265, and 4.4.265 have been released with the usual setof important fixes. Users should upgrade.

Security updates have been issued by openSUSE (chromium), Oracle (flatpak and kernel), Red Hat (virt:8.3 and virt-devel:8.3), and SUSE (gssproxy and xen).

The Mozilla Hacks site has areport on the use of ThreadSanitizer to detect and fix data races inthe Firefox browser. "While benign data races do exist, we foundthat data races arevery easily misclassified as benign. The reasons for this are clear: It ishard to reason about what compilers can and will optimize, and confirmationfor certain 'benign' data races requires you to look at the assembler codethat the compiler finally produces. Needless to say, this procedure isoften much more time consuming than fixing the actual data race and alsonot future-proof. As a result, we decided that the ultimate goal should bea 'no data races' policy that declares even benign data races asundesirable due to their risk of misclassification, the required time forinvestigation and the potential risk from future compilers (with betteroptimizations) or future platforms (e.g. ARM)."

Security updates have been issued by Debian (chromium, netty, python-bleach, and python3.5), Fedora (libmediainfo, libzen, and mediainfo), Mageia (openssl), openSUSE (chromium), Red Hat (389-ds:1.4, flatpak, kernel, kernel-rt, kpatch-patch, libldb, and virt:rhel and virt-devel:rhel), and Ubuntu (python-django and ruby-rack).

Kees Cook has posted along list of security-related improvements that made it into the 5.9kernel release. "Sasha Levin, Andy Lutomirski, Chang S. Bae, AndiKleen, Tony Luck, Thomas Gleixner, and others landed the long-awaitedFSGSBASE series. This provides task switching performance improvementswhile keeping the kernel safe from modules accidentally (or maliciously)trying to use the features directly (which exposed an unprivileged directkernel access hole)."

Version3.2 of the Django web framework is out; it has been designated as along-term-support release. New features include automatic AppConfigdiscovery, functional indexes, pymemcache support, and more; see therelease notes for details.

The recent proposalfrom David Hildenbrand to remove support for the /dev/kmem specialfile has not sparked a lot of discussion. Perhaps that is because today'syoungsters, lacking an understanding of history, may be wonderingwhat that file is in the first place and, thus, be unclear on why it maymatter. Chances are that /dev/kmem will not be missed, but inpassing it takes away a venerable part of the Unix kernel interface.

Security updates have been issued by Debian (libxstream-java, php-nette, and smarty3), Fedora (curl, openssl, spamassassin, and webkit2gtk3), Mageia (ant, batik, kernel, kernel-linus, nodejs-chownr, nodejs-yargs-parser, python-bottle, and ruby-em-http-request), openSUSE (curl and OpenIPMI), and Red Hat (openssl).

The long saga of Oracle's copyright-infringement against Google, whichcopied much of the Java API for use in Android, has come to an end with thisruling [PDF] in favor of Google. "Google’s purpose was to create adifferent task-related system for a different computing environment(smartphones) and to create a platform—the Android platform—that would helpachieve and popularize that objective. The record demonstrates numerousways in which reimplementing an interface can further the development ofcomputer programs. Google’s purpose was therefore consistent with thatcreative progress that is the basic constitutional objective of copyrightitself."

The 5.12-rc6 kernel prepatch is out fortesting. "Well, if rc5 was bigger than usual, and I worried about what thatmeant for this release, rc6 is positively tiny.So I think it was just due to the usual random timing fluctuations,probably mainly networking updates (which were in rc5, but not inrc6). Which means that unless things change in the next two weeks, theschedule for this release is going to be the usual one."

One of the key tasks assigned to the memory-management subsystem is tooptimize the system's use of the available memory; that means pushing outpages containing unused data so that they can be put to better useelsewhere. Predicting which pages will be accessed in the near future is atricky task, and the kernel has evolved a number of mechanisms designed toimprove its chances of guessing right. But the kernel not only often getsit wrong, it also can expend a lot of CPU time to make the incorrectchoice. The multi-generationalLRU patch set posted by Yu Zhao is an attempt to improve thatsituation.

Security updates have been issued by Debian (busybox, ldb, openjpeg2, spamassassin, and underscore), Fedora (kernel, kernel-headers, and kernel-tools), Mageia (privoxy, python and python3, and rpm), openSUSE (ovmf, tar, and tomcat), SUSE (curl, firefox, OpenIPMI, and tomcat), and Ubuntu (openexr).

The process of hardening the kernel can benefit in a number of ways fromsupport by the compiler. In recent years, the Kernel Self Protection Project has broughtthis support from the grsecurity/PaXpatch set into the kernel in the form of GCCplugins; LWN looked into that process backin 2017. A recent discussion has highlighted the fact that the use ofGCC plugins brings disadvantages as well, and some developers would prefer to see those plugins replaced.

Security updates have been issued by Debian (underscore), Fedora (busybox, linux-firmware, and xmlgraphics-commons), Oracle (kernel and kernel-container), Slackware (curl and seamonkey), SUSE (firefox and opensc), and Ubuntu (spamassassin).

Version 18.1 ofLineageOS, the Android-based distribution once known as Cyanogen, isavailable. "With that said, we have been working extremely hardsince Android 11’s release last August to port our features to this newversion of Android. Thanks to our hard work adapting to Google’s fairlylarge changes in Android 10, we were able to rebase our changes ontoAndroid 11 much more efficiently. This led to a lot of time to spend oncool new features!" Some of those features include in improvedvoice recorder, a new calendar, a built-in backup mechanism, an improvedmusic player, and more.

A company called Xinuos has announced alawsuit against IBM and Red Hat that has a familiar echo to it."Xinuos alleges that the IBM and Red Hat conspiracy has harmed theopen-source community and specifically Xinuos’ OpenServer 10 product, whichis based on FreeBSD, an open-source UNIX-based operating system andalternative to Red Hat’s Linux-based open-source operating system,RHEL. 'By dominating the Unix/Linux server operating system market,competing open-source operating systems, like our FreeBSD-based OpenServer10, have been pushed out of the market.'" The fulltext of the suit [PDF] is available for those wanting the details.

The LWN.net Weekly Edition for April 1, 2021 is available.

The HPy project has beenaround for more than a year now; it is meant to provide an alternate C APIfor Python that allows extensions to the language to run, and run well, in moreenvironments. It first came to our attention in a reportof a talk at the 2020Python Language Summit (LWN coverage), but it goes back to some discussions that wereheld at EuroPython 2019. Thereare a number of ways that the existing C API holds back innovation forPython, but there are also some hugely important extensions (e.g. NumPy) that use it; any change to the APIneeds to take those into account.

Security updates have been issued by Debian (curl, ldb, leptonlib, and linux-4.19), Fedora (busybox), Gentoo (openssl, redis, salt, and sqlite), Mageia (firefox, fwupd, glib2.0, python-aiohttp, radare2, thunderbird, and zeromq), openSUSE (firefox), SUSE (ovmf, tomcat, and zabbix), and Ubuntu (curl, lxml, and pygments).

A problem reported when attaching GDB to programs that use io_uring has led to a flurry of potentialsolutions, and one that was merged into Linux 5.12-rc5. The problemstemmed from a change made in the 5.12merge window tohow the threads used by io_uring were created, such that they became associatedwith the process using io_uring. Those "I/O threads" were treatedspecially in the kernel, but that led to the problem with GDB (and likely other ptrace()-usingprograms). The solution is to treat them like other threads because itturned out that trying to makethem special caused more problems than it solved.

CloudLinux has announced the availability of a "ready for productionworkloads" version of AlmaLinux, which is intended to be areplacement for CentOS 8. Also announced is the creation of afoundation to manage the distribution: "The company also announced the formation of a non-profit organization thatwill take over responsibility for managing the AlmaLinux project goingforward. CloudLinux has committed a $1 million dollars annual endowment tosupport the project. The AlmaLinux project named Jack Aboutboul as communitymanager of AlmaLinux."

Stable kernels 5.11.11, 5.10.27, 5.4.109, 4.19.184, 4.14.228, 4.9.264, and 4.4.264 have been released. They all containimportant fixes and users should update.

Security updates have been issued by Debian (lxml), Fedora (openssl, pdfbox, rpm, and rubygem-kramdown), openSUSE (eclipse), Oracle (flatpak and openssl), Red Hat (curl, kernel, kpatch-patch, mariadb, nss-softokn, openssl, perl, and tomcat), and SUSE (firefox, ovmf, and tar).

So far, this series has covered five common lockless patterns in the Linuxkernel; those are probably the five that you will most likely encounterwhen working on Linux. Throughout this series, some details have been left out and somesimplifications were made in the name of clarity. In this finalinstallment, I will sort out some of these loose ends and try to answerwhat is arguably themost important question of all: when should you use the locklesspatterns that have been described here?

John Sullivan, executive director of the Free Software Foundation, has announced hisresignation from the organization. "It's been a humbling honorto serve this institution, and to work alongside the FSF's staff, members,and volunteers over the years. The current staff deserve your fullconfidence and support -- they certainly have mine."Meanwhile, the FSF has announcedthe addition of Ian Kelling to its board of directors. "The boardand voting members look forward to having the participation of the staffvia this designated seat in our future deliberations. This is an importantstep in the FSF's effort to recognize and support new leadership, toconnect that leadership to the community, to improve transparency andaccountability, and to build trust. There is still considerable work to bedone, and that work will continue."

Security updates have been issued by Arch Linux (awstats, busybox, dotnet-runtime, dotnet-runtime-3.1, dotnet-sdk, dotnet-sdk-3.1, gitlab, godot, groovy, libebml, mkinitcpio-busybox, openssl, python2, vivaldi, webkit2gtk, and wpewebkit), CentOS (firefox and thunderbird), Debian (pygments, spamassassin, thunderbird, and webkit2gtk), Fedora (CGAL, dotnet3.1, dotnet5.0, firefox, kernel, qt, and xen), Mageia (imagemagick, jackson-databind, openscad, redis, and unbound), openSUSE (evolution-data-server, go1.15, and zstd), Oracle (firefox, openssl, and thunderbird), Red Hat (flatpak), Slackware (xterm), and Ubuntu (squid, squid3 and webkit2gtk).