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The Android system is designed to provide a responsive user experience on systems that, in a relative sense at least, have limited amounts of CPU and memory. Doing so requires a number of techniques, including regular use of a low-memory process killer, that are not seen elsewhere. In a memory-management-track session at the 2019 Linux Storage, Filesystem, and Memory-Management Summit, Suren Baghdasaryan covered a number of issues related to how Android ensures that interactive processes have enough memory to get their jobs done.

"People think that memory encryption sounds really cool; it will make my system more secure so I want it". At least, that is how Dave Hansen characterized the situation at the beginning of a session on the topic during the memory-management track at the 2019 Linux Storage, Filesystem, and Memory-Management Summit. This session, also led by Kirill Shutemov, covered a number of aspects of the memory-encryption problem on Intel processors and beyond. One clear outcome of the discussion was also raised by Hansen at the beginning: users of memory encryption need to think hard about where that extra security is actually coming from.

The splice() system call is, at its core, a write operation; it attempts to implement zero-copy I/O by moving pages from a pipe to a file. At the 2019 Linux Storage, Filesystem, and Memory-Management Summit, Miklos Szeredi described a nascent idea for rsplice() — a "reverse splice" system call. There were not a lot of definitive outcomes from this discussion, but one thing was clear: rsplice() needs a much better description (and some code posted) before the development community can begin to form an opinion on it.

Security updates have been issued by Fedora (libmediainfo, php-horde-horde, and php-horde-turba), SUSE (hostinfo, supportutils, libjpeg-turbo, and openssl), and Ubuntu (dovecot, libpng1.6, and memcached).

The 2019 version of the Linux Storage, Filesystem, and Memory-Management Summit opened with a plenary talk by Brendan Gregg on observing the state of Linux systems using BPF. It is, he said, an exciting time; the BPF-based "superpowers" being added to the kernel are growing in capability and maturity. It is now possible to ask many questions about what is happening in a production Linux system without the need for kernel modifications or even basic debugging information.

Fedora Magazine has announced the release of Fedora 30. "Fedora Editions are targeted outputs geared toward specific “showcase” uses. Since we first started using this concept in the Fedora 21 release, the needs of the community have continued to evolve. As part of Fedora 30, we’re combining cloud and server into the Fedora Server edition. We’re bringing in Fedora CoreOS to replace Fedora Atomic Host as our container-focused deliverable in the Fedora 30 timeframe — stay tuned for that. The Fedora Workstation edition continues to focus on delivering the latest in open source desktop tools. Of course, we produce more than just the editions. Fedora Spins and Labs target a variety of audiences and use cases, including the Internet of Things. And, we haven’t forgotten our alternate architectures, ARM AArch64, Power, and S390x."

Security updates have been issued by CentOS (kernel, openwsman, and ovmf), Debian (gst-plugins-base1.0 and libvirt), Fedora (libX11, poppler, python-urllib3, samba, and wpewebkit), openSUSE (GraphicsMagick), SUSE (atftp, glibc, libssh2_org, and wpa_supplicant), and Ubuntu (wavpack).

Determining the license that any given package uses can be difficult, but it is essential in order to properly comply with that license and, thus, the developer's wishes. There is an enormous amount of "open source" software available these days that is not clearly licensed, which is where the ClearlyDefined project comes in. The project is collecting a curated list of packages, source location, and license information; some of that collection can be automated, but ClearlyDefined is targeting the community to provide curation in the form of cleanups and additions.

The Apache Software Foundation (ASF) and GitHub have announced [ASF, GitHub] that all ASF projects using git have moved to GitHub and the ASF git service has been decommissioned. (Thanks to Paul Wise)

Security updates have been issued by Arch Linux (chromium, libpng, and openssh), Debian (checkstyle, evolution, gst-plugins-base0.10, gst-plugins-base1.0, imagemagick, libpng1.6, monit, and systemd), Fedora (aria2, php-symfony, php-symfony3, php-symfony4, and python-jinja2), openSUSE (ceph, libssh2_org, libvirt, php7, python3, samba, wget, and xerces-c), Red Hat (rh-python35-python), Slackware (bind), SUSE (libssh2_org), and Ubuntu (evince, gst-plugins-base0.10, gst-plugins-base1.0, and mysql-5.7).

Linus has released the 5.1-rc7 kernel prepatch for testing. "But it's all pretty tiny. Plus about 30% of the patches are marked for stable, so on the whole it really does feel like 5.1 is on target for a regular release next weekend."

The 5.0.10, 4.19.37, 4.14.114, 4.9.171, 4.4.179, and 3.18.139 stable kernel updates have all been released; each contains a moderately large set of important fixes.

Adrian Ratiu continues his series on eBPF with part 3, which looks at various ways to write and build eBPF programs. It starts by looking at using "restricted C" with the LLVM eBPF compiler, moves into looking at the BPF Compiler Collection (BCC), then bpftrace, and finally the IOVisor cloud-based eBPF tools. "Not everyone has kernel sources at hand, especially in production, and it's also a bad idea in general to tie eBPF-based tools to a specific kernel source revision. Designing and implementing the interactions between eBPF program's backends, frontends, loaders and data structures can be very complex, error-prone and time consuming, especially in C which is considered a dangerous low-level [language]. In addition to these risks developers are also in a constant danger of re-inventing the wheel for common problems, with endless design variations and implementations. To alleviate all these pains is why the BCC project exists: it provides an easy-to-use framework for writing, loading and running eBPF programs, by writing simple python or lua scripts in addition to the 'restricted C' as exemplified above."

The recently discovered vulnerability in Thunderbolt has restarted discussions about protecting the kernel against untrusted, hotpluggable hardware. That vulnerability, known as Thunderclap, allows a hostile external device to exploit Input-Output Memory Management Unit (IOMMU) mapping limitations and access system memory it was not intended to. Thunderclap can be exploited by USB-C-connected devices; while we have seen USB attacks in the past, this vulnerability is different in that PCI devices, often considered as trusted, can be a source of attacks too. One way of stopping those attacks would be to make sure that the IOMMU is used correctly and restricts the device to accessing the memory that was allocated for it. Lu Baolu has posted an implementation of that approach in the form of bounce buffers for untrusted devices.

Security updates have been issued by Debian (gpac and mercurial), Fedora (kernel-headers and kernel-tools), openSUSE (GraphicsMagick, kauth, lxc, lxcfs, python, qemu, and xmltooling), SUSE (freeradius-server, ImageMagick, libvirt, samba, and wireshark), and Ubuntu (bind9).

Over at Opensource.com, Jason Brock tries out Linux graphics tools, with an eye toward their ability to replace the proprietary tools he uses on a day-to-day basis. Overall, the tools held their own for a variety of tasks (e.g. logo and ad design, publication layout), though the lack of a certain type of tool brought the overall grade down to a B+: "The lack of available wireframing and prototyping applications really brought down the average, but I'd still call it a successful exercise. As I mentioned at the beginning, design is a craft and it relies on collaboration. All of the tools I looked at—Inkscape, LibreDraw, GIMP, and Scribus—can run just as well on Windows or MacOS as they do on any Linux distribution. The ability to create robust artwork and share editable files with stakeholders and colleagues on the platform of their choice means that a serious argument could be made that these tools are even more versatile than their proprietary counterparts."

The release of the 5.1-rc6 kernel prepatch on April 21 indicates that the 5.1 development cycle is getting close to its conclusion. So naturally the time has come to put together some statistics describing where the changes merged for 5.1 came from. It is, for the most part, a fairly typical development cycle.

Security updates have been issued by Debian (putty and systemd), Fedora (kernel, kernel-headers, and kernel-tools), Gentoo (ming and qemu), openSUSE (openexr and slurm), SUSE (ImageMagick, jasper, ntfs-3g_ntfsprogs, openssh, and webkit2gtk3), and Ubuntu (php5 and tcpflow).

The LWN.net Weekly Edition for April 25, 2019 is available.

An April Fools joke that went sour seems to be at least the proximate cause for a rather large upheaval in the Devuan community. For much of April 1 (or March 31 depending on time zone), the Devuan web site looked like it had been taken over by attackers, which was worrisome to many, but it was all a prank. The joke was clever, way over the top, unprofessional, or some combination of those, depending on who is describing it, but the incident and the threads on the devuan-dev mailing list have led to rancor, resignations, calls for resignations, and more.