LWN.net

The 5.6-rc7 kernel prepatch is out fortesting; this may be the last one before the final release."The world around us may be going through strange times, but at leastso far kernel development looks normal."

A new batch of stable kernels has just been released: 5.5.11, 5.4.27, 4.19.112, 4.14.174, 4.9.217, and 4.4.217.As usual, these contain important fixes throughout the kernel tree; usersshould upgrade.

The io_uring subsystem has, in the lastyear, redefined how asynchronous I/O is done on Linux systems. As thissubsystem grows in both capability and users, though, it starts to run intolimitations in the types of operations that can be expressed. That isdriving a number of changes in how operations are programmed for io_uring.One example is the mechanisms considered for carrying a file descriptorbetween operations that was covered here in early March. Another has todo with how I/O buffers are chosen for operations.

The Linux Mint Debian Edition (LMDE) 4 has been released. "LMDE is a Linux Mint project which stands for 'Linux Mint Debian Edition'. Its goal is to ensure Linux Mint would be able to continue to deliver the same user experience, and how much work would be involved, if Ubuntu was ever to disappear. LMDE is also one of our development targets, to guarantee the software we develop is compatible outside of Ubuntu.LMDE aims to be as similar as possible to Linux Mint, but without using Ubuntu. The package base is provided by Debian instead." It is based on Debian 10 ("Buster") with lots of new features, including many improvements from Linux Mint 19.3. More information can be found in the release notes.

Security updates have been issued by Arch Linux (bluez and chromium), Debian (icu, rails, thunderbird, and twisted), Fedora (chromium and webkit2gtk3), Gentoo (bsdiff, cacti, clamav, fribidi, libgit2, pecl-imagick, phpmyadmin, pyyaml, and tomcat), openSUSE (wireshark), Oracle (firefox, icu, python-imaging, thunderbird, and zsh), Scientific Linux (thunderbird), SUSE (firefox, nghttp2, thunderbird, and tomcat), and Ubuntu (twisted).

Author Nick Black has written an extensive book on the creation of textualuser interfaces using the notcurses library; it's available under the Apachelicense [PDF]. "Many people asked how such a thing wasuseful. My usual response was that numerous devices don’t present a bitmapinterface, that X11 GUIs run remotely over SSH are effectively unusable,that plenty of machines don’t have a GUI environment installed, that thereare obvious applications for large outdoor displays, and that Sixel isn’twell-supported across different terminal emulators. It seems impossible inan age of gigatransistor graphics cards, but the text environment stillpresents perceivably less latency than most GUI toolkits."

The kernel's memory-management subsystem goes to great lengths to keep thepages that are actually in use in memory. But sometimes it gets thingswrong, leading to reduced performance or, in the worst cases, flat-outthrashing. We may be about to see a significant improvement, though,thanks to apatch set from Joonsoo Kim changing how anonymous pages (thosecontaining data not backed by files on disk) are managed.As it turns out, all that had to be done was to make use of some work thatalready exists in related parts of the memory-management code.

Here's adetailed blog post on how the Qubes distribution is working to isolatethe graphical interface from the rest of the system. "The upcoming4.1 release changes this protocol to a more flexible form. It will nolonger use direct memory addresses, but an abstract mechanism in which theqube has to explicitly allow access to a particular memory page. In ourcurrent implementation — under Xen — we use the grant tables mechanism,which provides a separate memory allocation API and allows working ongrants and not directly on memory pages. Other implementations will also bepossible: whether for another hypervisor (e.g. KVM) or for a completelydifferent architecture not based on shared memory (e.g. directly sendingframes to another machine)."

Security updates have been issued by Debian (gdal), Fedora (nethack), Mageia (okular, sleuthkit, and webkit2), openSUSE (salt), Oracle (icu, kernel, python-pip, python-virtualenv, and zsh), Red Hat (icu, python-imaging, thunderbird, and zsh), Scientific Linux (icu, python-imaging, and zsh), SUSE (postgresql10), and Ubuntu (apache2).

The LWN.net Weekly Edition for March 19, 2020 is available.

The python-ideas mailing list is typically used to discuss new features orenhancements for the language; ideas that gain traction will get turnedinto Python Enhancement Proposals (PEPs) and eventually make their way topython-dev for wider consideration. Steve Jorgensen recently starteda discussion of just that sort; he was looking for a way to addcustomization to the "pretty-print" module (pprint)so that objects could change the way they are displayed. The subsequentthread went in a few different directions that reflect the nature of themailing list—and the idea itself.

Konstantin Ryabitsev introducesthe "b4" tool for kernel development. Developers and LWN readers willbe familiar with b4 under its previous name: get-lore-mbox. "On top of that, b4 alsointroduces support for cryptographic patch attestation, which makes itpossible to verify that patches (and their metadata) weren't modified intransit between developers. This is still an experimental feature, butinitial tests have been pretty encouraging." See this article for early coverage of theattestation feature.

Drew DeVault complainsabout the complexity of the web and the browsers that work with it."The major projects are open source, and usually when an open-sourceproject misbehaves, we’re able to to fork them to offer an alternative. Buteven this is an impossible task where web browsers are concerned. Thenumber of W3C specifications grows at an average rate of 200 new specs peryear, or about 4 million words, or about one POSIX every 4 to 6 months. Howcan a new team possibly keep up with this on top of implementing theoutrageous scope web browsers already have now?"

Legislation recently proposed in the US Senate is ostensibly meant tocombat "child sexual abuse material" (CSAM), but it does not actually domuch to combat that horrible problem. Its target, instead, is the encryptionof user communications, which the legislation—tellingly—never mentions.The EliminatingAbusive and Rampant Neglect of Interactive Technologies Act of 2020,EARN IT for short, is an attempt to force online service providers(e.g. Facebook, Google, etc.) to follow a set of "best practices"determined by a commission, to combat the scourge of CSAM; the composition ofthat commission makes it clear that end-to-end encryption will not be oneof those practices, but companies that do not follow the best practices will loseliability protection for their users' actions. It is, in brief, anattempt to force providers to either abandon true end-to-end encryption orface ruinous lawsuits—all without "seeming" to be about encryption at all.

Stable kernels 5.5.10, 5.4.26, and 4.19.111 have been released with importantfixes. Users of those series should upgrade.

Security updates have been issued by Debian (libvncserver and twisted), Fedora (libxslt), Red Hat (kernel, kernel-rt, python-flask, python-pip, python-virtualenv, slirp4netns, tomcat, and zsh), Scientific Linux (kernel, python-pip, python-virtualenv, tomcat, and zsh), SUSE (apache2-mod_auth_openidc and skopeo), and Ubuntu (apport and dino-im).

Security updates have been issued by Arch Linux (okular, thunderbird, and webkit2gtk), Debian (webkit2gtk), Fedora (php-horde-Horde-Form), Gentoo (libvorbis, nss, and proftpd), Oracle (firefox and kernel), Red Hat (kernel), Scientific Linux (firefox), SUSE (cni, cni-plugins, conmon, fuse-overlayfs, podman, librsvg, and ovmf), and Ubuntu (ceph, icu, linux, linux-aws, linux-kvm, linux-aws-5.0, linux-gcp, linux-gke-5.0, linux-oracle-5.0, linux-kvm, linux-oracle, linux-raspi2, linux-raspi2-5.3, linux-kvm, linux-raspi2, linux-snapdragon, and linux-lts-xenial, linux-aws).

Over the last decade, the addition of a "flags"argument to all new system calls, even if no flags are actually neededat theoutset, has been widely adopted as a best practice. The result hascertainly been greater API extensibility, but we have also seen a proliferation ofvarious types of flags for related system calls. For calls related tofiles and filesystems, in particular, the available flags have reached apoint where some calls will need as many as three arguments for themrather than just one.

The Free Software Foundation has announcedthe recipients of the 2019 Free Software Awards. A new category was addedthis year; the Award forOutstanding New Free Software Contributor went to Clarissa Lima Borges,"a talented young Brazilian software engineering student whoseOutreachy internship work focused on usability testing for various GNOMEapplications". The Project of social benefitaward went to Let's Encrypt, and the Award for the Advancement ofFree Software was given to Jim Meyering, "a prolific free software programmer, maintainer, and writer".

Stable kernel 4.19.110 has been released. "This fixes a problem in 4.19.109 in the KVM subsystem. If you use KVM,you are strongly encouraged to upgrade. If not, no big deal, you canignore this release."

Security updates have been issued by Debian (graphicsmagick, qemu, and slurm-llnl), Fedora (ansible, couchdb, mediawiki, and python3-typed_ast), Gentoo (atftp, curl, file, gdb, git, gst-plugins-base, icu, libarchive, libgcrypt, libjpeg-turbo, libssh, libvirt, musl, nfdump, ppp, python, ruby-openid, runc, sqlite, squid, sudo, SVG Salamander, systemd, thunderbird, tiff, and webkit-gtk), Mageia (firefox, kernel, and thunderbird), openSUSE (firefox, librsvg, php7, and tomcat), Red Hat (firefox), Slackware (thunderbird), and SUSE (firefox, kernel, salt, and wireshark).

Version 4.4 of The Amnesic Incognito Live System (or Tails) has been released. It has fixed a bunch of security vulnerabilities in Tails 4.3; users are advised to "upgrade as soon as possible". Tails 4.4 brings new versions of the Tor Browser (9.0.6), Thunderbird (68.5.0), and the Linux kernel (5.4.19). It also fixes some problems with WiFi. Tails is a Linux distribution that runs from removable media; it is focused on privacy, security, and anonymity.

The 5.6-rc6 kernel prepatch has beenreleased. "Diffstat looks normal, and the number of commits is right in themiddle of the usual range too. And I don't think any of the commitslook all that strange either - it's all pretty small."

The HypertextTransfer Protocol (HTTP) is a core component of the world-wideweb. Over its evolution it has added features, including encryption, but time has revealed its limitations andthose of the whole protocol stack. At FOSDEM 2020, Daniel Stenberg delivered a talkabout anew version of the protocol called HTTP/3. It is under development andincludes some big changes under the hood. There is no more TCP, forexample; a new transport protocol called QUIC is expected to improve performance and allow newfeatures.

Wired has an article on an open-source tool that is being used to track strains of Covid-19 throughout the world."In the case of the Seattle area teenager, genetic data about his strain of Covid-19 was uploaded to Gisaid, a platform for sharing genomic data. Then researchers at Nextstrain made the connection with the earlier patient.Nextstrain is an open source application that tracks the evolution of viruses and bacteria, including Covid-19, Ebola, and lesser-known outbreaks such as Enterovirus D68 using data sourced largely from Gisaid. Hodcroft and other researchers involved with the project analyze the data shared on Gisaid for mutations and visualize the results. That’s how the team was able to spot the connection between the two Covid-19 cases in Washington."

Psycopg is the database adapter usedby most Python programs needing to work with the PostgreSQL databasemanager. In thisblog post, psycopg maintainer Daniele Varrazzo looks forward to thenext major version. "There is a chance now to rethink how thick theC libpq wrapper should be. We can reduce the C implementation to a minimalwrapper around the libpq (replaceable by a CFFI Python wrapper if compilingC is not available on the client), using it as a foundation to build afamiliar DBAPI blocking interface. A blocking behaviour is not bad initself: it allows to write most of the programs, the ones which don't needcrazy concurrency, in a simple and familiar paradigm; the async layer wouldbe available under the hood to squeeze the best performance in programs whohave embraced an asynchronous pattern and framework."

Security updates have been issued by Arch Linux (firefox, golang-golang-x-crypto, kernel, mbedtls, ppp, and python-django), Debian (slirp and yubikey-val), Fedora (firefox, java-1.8.0-openjdk-aarch32, mbedtls, monit, seamonkey, sympa, and zsh), Gentoo (chromium, e2fsprogs, firefox, groovy, postgresql, rabbitmq-c, ruby, and vim), Mageia (ppp), openSUSE (kernel), and SUSE (glibc, kernel, openstack-manila, php5, and squid).

As expected, the5.5.9,5.4.25,4.19.109,4.14.173,4.9.216, and4.4.216stable kernels have all been released; each contains another set ofimportant fixes.

Back in 2017, Waiman Long posted a patchset placing limits on the number of "negative dentries" stored by thekernel. The better part of three years later, that work continues with,seemingly, no better prospects for getting into the mainline. It would beunderstandable, though, if many people out there don't really know whatnegative dentries are or why kernel developers care about them. That, atleast, can be fixed, even if the underlying problem seems to be moredifficult.

Security updates have been issued by CentOS (kernel), Debian (dojo, firefox-esr, sleuthkit, and wpa), Fedora (cacti, cacti-spine, and python-psutil), Oracle (kernel), Red Hat (kernel), Scientific Linux (kernel), SUSE (ardana-ansible, ardana-cinder, ardana-cobbler, ardana-db, ardana-horizon, ardana-input-model, ardana-monasca, ardana-mq, ardana-nova, ardana-octavia, ardana-osconfig, ardana-tempest, ardana-tls, crowbar-core, crowbar-ha, crowbar-openstack, crowbar-ui, keepalived, openstack-barbican, openstack-ceilometer, openstack-cinder, openstack-dashboard, openstack-dashboard-theme-SUSE, openstack-designate, openstack-heat, openstack-horizon-plugin-designate-ui, openstack-horizon-plugin-ironic-ui, openstack-horizon-plugin-neutron-lbaas-ui, openstack-horizon-plugin-octavia-ui, openstack-ironic, openstack-ironic-python-agent, openstack-keystone, openstack-magnum, openstack-monasca-agent, openstack-neutron, openstack-neutron-fwaas, openstack-neutron-gbp, openstack-neutron-vpnaas, openstack-nova, openstack-octavia, openstack-octavia-amphora-image, openstack-sahara, openstack-swift, python-amqp, python-ironic-lib, python-keystoneauth1, python-keystoneclient, python-keystonemiddleware, python-ovs, supportutils-plugin-suse-openstack-cloud, rubygem-crowbar-client, rubygem-puma, venv-openstack-horizon, ardana-cinder, ardana-cobbler, ardana-designate, ardana-extensions-example, ardana-extensions-nsx, ardana-glance, ardana-heat, ardana-input-model, ardana-ironic, ardana-keystone, ardana-logging, ardana-monasca, ardana-monasca-transform, ardana-mq, ardana-neutron, ardana-nova, ardana-octavia, ardana-osconfig, ardana-tempest, crowbar-core, crowbar-ha, crowbar-openstack, crowbar-ui, keepalived, mariadb, openstack-cinder, openstack-dashboard, openstack-dashboard-theme-SUSE, openstack-heat, openstack-heat-templates, openstack-horizon-plugin-designate-ui, openstack-horizon-plugin-neutron-lbaas-ui, openstack-ironic, openstack-keystone, openstack-monasca-agent, openstack-neutron, openstack-neutron-gbp, openstack-neutron-vsphere, openstack-nova, openstack-octavia, openstack-octavia-amphora-image, openstack-resource-agents, openstack-sahara, openstack-trove, python-cinderlm, python-congressclient, python-designateclient, python-ironic-lib, python-ne tworking-cisco, python-osc-lib, python-oslo.context, python-oslo.rootwrap, python-oslo.serialization, python-oslo.service, python-stevedore, python-taskflow, rubygem-crowbar-client, rubygem-pumavenv-openstack-swift, firefox, ipmitool, kernel, and php72), and Ubuntu (firefox).

The LWN.net Weekly Edition for March 12, 2020 is available.

A recent message tothe debian-project mailing list by Debian project leader (DPL) Sam Hartman isabout a proposal to moderate the mailing list. There have been repeatedattacks on various project members and the distribution itself posted tothe list over the last few years, many from sock-puppet, throwaway email accounts, which spawned a recent discussion onthe debian-private mailing list; Hartman was summarizing that discussionfor those who are not on the private list. But the problems ondebian-project (and other Debian public lists) are kind of just the tip ofthe iceberg; there is an ongoing, persistent effort to roil thedistribution and its community.

Version 3.36 of the GNOME desktop environment is out. "This release brings a new lock screen and a new app for managing shellextensions, among other things. Once again, the shell has received manyperformance improvements.Improvements to core GNOME applications include better support for meterednetworks and parental controls in GNOME Software, a new look for the initialsetup assistant, a redesigned GNOME Clocks, and many more." See the releasenotes for details and screenshots.

For those who are interested in the details of graphics synchronization:Jason Ekstrand describes in detail the value of explicit synchronization,the reason why we can't have it now, and a proposal for eventually makingit possible to go explicit. "Explicit synchronization is the future of graphics and media. Atleast, that seems to be the consensus among all the graphics peopleI've talked to. I had a chat with one of the lead Android graphicsengineers recently who told me that doing explicit sync from the startwas one of the best engineering decisions Android ever made. It'salso the direction being taken by more modern APIs such as Vulkan."

Security updates have been issued by CentOS (qemu-kvm and sudo), Debian (chromium), Mageia (gpac, libseccomp, and tomcat), openSUSE (gd and postgresql10), Oracle (qemu-kvm), Red Hat (chromium-browser), Scientific Linux (qemu-kvm), Slackware (firefox), and SUSE (ipmitool, java-1_7_0-openjdk, librsvg, and tomcat).

The Let's Encrypt project has madereal strides in helping to ensure that every web site can use the encryptedHTTPS protocol; it has provided TLS certificates at no charge that areaccepted by most or all web browsers. Free certificates accepted by thebrowsers are something that was difficult to find prior to the advent of the project in 2014; as of the end of February, theproject has issuedover a billion certificates. But a bug that was recentlyfound in the handling of Certificate AuthorityAuthorization (CAA) by the project put roughly 2.6% of the activecertificates—roughly three million—at risk of immediate revocation. As might beexpected, that caused a bit of panic in some quarters, but it turned outthat the worst outcome was largely averted.

The latest release of Firefox features some login management improvements,the ability to add custom sites to the Facebook Container, better privacyfor web voice and video calls, and better add-on management. See the release notesfor more information.

Security updates have been issued by Debian (libvpx and network-manager-ssh), Fedora (cacti, cacti-spine, and podman), openSUSE (chromium and python-bleach), Oracle (curl), Red Hat (ansible and qemu-kvm), SUSE (gd, ipmitool, and php7), and Ubuntu (runc and sqlite3).

The Linux development community is spread out over the planet andinteracts primarily through email and online systems. It is widelyfelt, though, that there is great value in getting people together inperson occasionally to talk about current issues and get to knoweach other as people. This year, though, the coronavirus pandemic isdisrupting the conference schedule to an extent that won't be known forsome time. But there are longer-term concerns as well, to the point thatthe head organizer for one of the kernel community's most successful eventsis questioning whether it should continue to exist.

LibrePlanet was scheduled for March 14-15 but it has been canceled. "However, just because we won't be holding a conference in person this year doesn't mean that we've given up our fight to "free the future." Instead, LibrePlanet will be a fully free (as in freedom) virtual conference and livestream. We had an extremely exciting program planned, and we're going to try and maintain as much of that schedule as possible with all of the speakers who are willing and able to participate remotely. The resulting livestream will be run on and entirely accessible via free software, so that you can enjoy these amazing talks from the comfort of your home."

The ChemnitzerLinux-Tage that was to take place March 14-15 has been canceled. "Whether we meet later this year or first in March 2021, we will discuss within the organization team in the next few days."

The openSUSE Summit in Dublin, Ireland was scheduled for March 27-28. Theevent has been canceleddue to travel bans. SUSECON isstill scheduled for March 23-27, however it will be a digital event. Thein-person meeting in Dublin has been canceled.

Security updates have been issued by Fedora (seamonkey), Mageia (apache-mod_auth_openidc, binutils, chromium-browser-stable, dojo, firejail, gcc, glib2.0, glibc, http-parser, ilmbase, libarchive, libgd, libsolv, mbedtls, pcre, pdfresurrect, php, proftpd, pure-ftpd, python-bleach, ruby-rake, transfig, weechat, and xen), openSUSE (chromium, ovmf, python-bleach, and yast2-rmt), Oracle (curl, http-parser, kernel, sudo, and xerces-c), Red Hat (chromium-browser and kernel-alt), Scientific Linux (sudo), and SUSE (gimp, kernel, and librsvg).

Linus has put out a high-altitude 5.6-rc5prepatch release. "That said, everything looks mostly fine. I say'mostly', because while nothing in particular looks worrisome, this rc5 isbigger than I'd have liked. In fact, it's not only bigger than rc4 was, butit's bigger than we historically are at this point."

Systemd 245 is out. As usual, the list of new features is long; perhapsthe one that has gained the most attention is systemd-homed:A small new service systemd-homed.service has been added, that may be used to securely manage home directories with built-in encryption. The complete user record data is unified with the home directory, thus making home directories naturally migratable.There is also a new database for holding user and group data and asystemd-repart tool for the management of partitions on storage-devices atboot time.

DNF, the Fedora package manager, is going to be significantly rewritten; itseems it is truly "development not finished" for now."We've managed to drop a lot of redundant code across the whole DNF stack in the past years, but we have reached a point when it's nearly impossible to consolidate the code any further without breaking the API/ABI. Especially with PackageKit being dead, we can't move with the old 'libhif' API in libdnf, because making any bigger changes to PackageKit is clearly out of scope."

System calls on Linux are relatively cheap, though the mitigations forspeculative-execution vulnerabilities have made them more expensive thanthey once were. But even cheap system calls add up if one has to make alarge number of them. Thus, developers have been working on ways to avoidsystem calls for a long time. Currently under discussion is a pair of waysto reduce the number of system calls required to read a file's contents,one of which is rather simpler than the other.

Security updates have been issued by Arch Linux (chromium, opensc, opensmtpd, and weechat), Debian (jackson-databind and pdfresurrect), Fedora (sudo), openSUSE (openfortivpn and squid), Red Hat (virt:8.1 and virt-devel:8.1), Scientific Linux (http-parser and xerces-c), and SUSE (gd, kernel, postgresql10, and tomcat).

Over on the Collabora blog, Julian Bouzas writes about PipeWire, which is a relatively new multimedia server for the Linux desktop and beyond. "PipeWire was originally created to only handle access to video resources and co-exist with PulseAudio. Earlier versions have already been shipping in Fedora for a while, allowing Flatpak applications to access video cameras and to implement screen sharing on Wayland. Eventually, PipeWire has ended up handling any kind of media, to the point of planning to completely replace PulseAudio in the future. The new 0.3 version is marked as a preview for audio support.But why replace PulseAudio? Although PulseAudio already provides a working intermediate layer to access audio devices, PipeWire has to offer more features that PulseAudio was not designed to deliver, starting with a better security model, which allows isolation between applications and secure access from within containers.Another interesting feature of PipeWire is that it unifies the two audio systems used on the desktop, JACK for low-latency professional audio and PulseAudio for normal desktop use-cases. PipeWire was designed to be able to accommodate both use cases, delivering very low latency, while at the same time not wasting CPU resources. This design also makes PipeWire a much more efficient solution than PulseAudio in general, making it a perfect fit for embedded use cases too."

The Positive Technologies blog is reporting on an unfixable flaw the company has found in Intel x86 hardware that has the potential to subvert the hardware root of trust for a variety of processors. "The EPID [Enhanced Privacy ID] issue is not too bad for the time being because the Chipset Key is stored inside the platform in the One-Time Programmable (OTP) Memory, and is encrypted. To fully compromise EPID, hackers would need to extract the hardware key used to encrypt the Chipset Key, which resides in Secure Key Storage (SKS). However, this key is not platform-specific. A single key is used for an entire generation of Intel chipsets. And since the ROM vulnerability allows seizing control of code execution before the hardware key generation mechanism in the SKS is locked, and the ROM vulnerability cannot be fixed, we believe that extracting this key is only a matter of time. When this happens, utter chaos will reign. Hardware IDs will be forged, digital content will be extracted, and data from encrypted hard disks will be decrypted." Intel has said that it is aware of the problem (CVE-2019-0090), but since it cannot be fixed in the ROM, Intel is "trying to block all possible exploitation vectors"; the fix for CVE-2019-0090 only blocks one such vector, according to the blog post.