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A buggy patch posted to the linux-kernel mailing list in early April was apparently the last straw for Greg Kroah-Hartman as it led to the planned reversion of a whole slew of commits with one thing in common: their origin at the University of Minnesota (UMN). The patch to the NFSv4 authorization mechanism was duly questioned by two NFS developers, but it is not an honest mistake; according to Kroah-Hartman, there has been an attack of sorts underway as part of some academic research at the university. In order to be sure that these intentional bugs, many with security implications, do not continue to haunt Linux, he is working on reverting commits that came from email addresses with the umn.edu domain.
In a lengthy message to the linux-kernel mailing list, Miguel Ojeda "introduced" the Rust for Linux project. It was likely not the first time that most kernel developers had heard of the effort; there was an extensive discussion of the project at the 2020 Linux Plumbers Conference, for example. It has also been raised before on the list. Now, the project is looking for feedback from the kernel community about its plans, thus the RFC posting on April 14.
Zoned block devices have some unfamiliar characteristics that result from compromises made in the name of higher storage density. They are divided into zones, some or all of which do not support random access for write operations. Instead, these "sequential" zones can only be written in order, from the first block to the last. This constraint poses a new challenge for filesystems, which are normally designed with the assumption that storage blocks can be written in any order. It is thus not surprising that zoned-device support in mainstream filesystems in Linux has been slow in coming; that is changing, though, with the addition of support for zoned block devices to Btrfs in Linux 5.12.
One of the key resources that defines a process is its address space — the set of mappings that determines what any specific memory address means within that process. An address space is normally private to the process it belongs to, but there are situations where one process needs to make changes to another process's memory; an interactive debugger would be one case in point. The ptrace() system call makes such changes possible, but it is slow and not always easy to use, so there has been a longstanding quest for better alternatives. One possibility, process_vm_exec() from Andrei Vagin, was recently posted for review.
The Fedora project may have managed to shake off its reputation for delayed releases in recent years, but that hasn't stopped the release date for Fedora 34 from slipping one week to April 27. Modulo a handful of bugs, though, this release is in its final form, so a look at what is coming is warranted. Distribution releases, especially those for fast-moving community distributions, are a good point at which to catch up with the state of many free-software projects and where Linux is headed in general. Fedora 34 includes a lot of changes, including the GNOME 40 release but, for the most part, it looks like an exercise in continuity.
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In early April, Fedora program manager Ben Cotton posted a proposal to use the distribution's debuginfod servers by default in Fedora 35. This feature would help developers who are trying to debug or trace their programs using various tools, but who are lacking the source code and debugging symbols needed. The servers can provide that data directly to the tools as needed, but there are some security and privacy concerns to work through before turning the feature on by default.
There are times when developers and system administrators need to diagnose problems in running code. The program to be examined can be a user-space process, the kernel, or both. Two of the major tools available on Linux to perform this sort of analysis are SystemTap and bpftrace. SystemTap has been available since 2005, while bpftrace is a more recent contender that, to some, may appear to have made SystemTap obsolete. However, SystemTap is still the preferred tool for some real-world use cases.
While some parts of the core kernel reached a relatively stable "done" state years ago, others never really seem to be finished. One of the latter variety is undoubtedly the kernel's implementation of spinlocks, which arbitrate access to data at the lowest levels of the kernel. Lock performance can have a significant effect on the performance of the system as a whole, so optimization work can pay back big dividends. Lest one think that this work is finally done, the NUMA-aware qspinlock patch set shows how some more performance can be squeezed out of the kernel's spinlock implementation.
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 target process. The user-space notification feature further allows those decisions to be deferred to another process. As this recent patch set from Sargun Dhillon shows, though, user-space notification still has some rough edges, especially when it comes to signals. This patch makes a simple change to try to address a rather complex problem brought to the fore by changes in the Go language's preemption model.
Stable kernels 5.11.16, 5.10.32, and 5.4.114 have been released. They contain important fixes and users should upgrade.
Security updates have been issued by Debian (firefox-esr, php-pear, wordpress, and zabbix), Oracle (java-1.8.0-openjdk and java-11-openjdk), Red Hat (java-1.8.0-openjdk, java-11-openjdk, kernel, and kpatch-patch), Scientific Linux (java-1.8.0-openjdk and java-11-openjdk), Slackware (seamonkey), SUSE (apache-commons-io, ImageMagick, kvm, ruby2.5, and sudo), and Ubuntu (edk2, libcaca, ntp, and ruby2.3, ruby2.5, ruby2.7).
Linux.com has published an interview with Thomas Gleixner with a focus on the realtime preemption work. "The approach to funding these kinds of projects reminds me of the Mikado Game, which is popular in Europe, where the first player who picks up the stick and disturbs the pile often is the one who loses. That’s puzzling to me, especially as many companies build key products depending on these technologies and seem to take the availability and sustainability for granted up to the point where such a project fails, or people stop working on it due to lack of funding. Such companies should seriously consider supporting the funding of the Real-Time project."
Security updates have been issued by Debian (xorg-server), Fedora (CImg, gmic, leptonica, mingw-binutils, mingw-glib2, mingw-leptonica, mingw-python3, nodejs, and seamonkey), openSUSE (irssi, kernel, nextcloud-desktop, python-django-registration, and thunderbird), Red Hat (389-ds:1.4, kernel, kernel-rt, perl, and pki-core:10.6), SUSE (kernel, sudo, and xen), and Ubuntu (clamav and openslp-dfsg).
OpenSSH 8.6 is now available. The "ssh-rsa" signature scheme, which uses the SHA-1 hash algorithm, will be disabled by default in the near future. "Note that the deactivation of "ssh-rsa" signatures does not necessarily require cessation of use for RSA keys. In the SSH protocol, keys may be capable of signing using multiple algorithms. In particular, "ssh-rsa" keys are capable of signing using "rsa-sha2-256" (RSA/SHA256), "rsa-sha2-512" (RSA/SHA512) and "ssh-rsa" (RSA/SHA1). Only the last of these is being turned off by default."
Firefox 88 has been released. New features include support for PDF forms with embedded JavaScript and smooth pinch-zooming using a touchpad, and better protection against cross-site privacy leaks. See this article for more information on how Firefox 88 combats window.name privacy abuses.
Firefox 78.10 ESR contains various fixes for stability, functionality, and security.
Security updates have been issued by CentOS (nettle, squid, and thunderbird), Debian (libebml, python-bleach, and python2.7), Fedora (batik, gnuchess, kernel-headers, kernel-tools, ruby, singularity, and xorg-x11-server), Mageia (clamav, kernel, kernel-linus, and python3), openSUSE (chromium, fluidsynth, opensc, python-bleach, and wpa_supplicant), Oracle (gnutls and nettle), Red Hat (dpdk, gnutls and nettle, mariadb:10.3 and mariadb-devel:10.3, and redhat-ds:11), and SUSE (kernel, qemu, and xen).
In the end, Linus decided to hold the 5.12 release for one more week and put out 5.12-rc8 instead. "Ok, so it's been _fairly_ calm this past week, but it hasn't been the kind of dead calm I would have taken to mean 'no rc8 necessary'. So here we are, with an extra rc to make sure things are all settled down."
Version 12.0.0 of the LLVM compiler suite is out. This appears to be a release with a lot of incremental improvements rather than large headline features; see the various sets of release notes in the announcement for details.
The Debian project has voted strongly to retain Jonathan Carter as the project leader. On that other little nagging issue, the project has voted not to issue a statement regarding Richard Stallman's return to the Free Software Foundation board of directors. This, too, was a relatively strong result over the other options. Details can be found on the specific pages for the project leader and general resolution ballots.
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