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Stable kernels 5.5.5, 5.4.21, and 4.19.105 have been released, with the usual set of important fixes.

At this point, most of the kernel work to avoid the year-2038 apocalypse has been completed. Said apocalypse could occur when time counted in seconds since 1970 overflows a 32-bit signed value (i.e. time_t). Work in the GNU C Library (glibc) and other C libraries is well underway as well. But the "fun" is just beginning for distributions, especially those that support 32-bit architectures, as a recent Debian discussion reveals. One of the questions is: how much effort should be made to support 32-bit architectures as they fade from use and 2038 draws nearer?

The Linux Foundation's Core Infrastructure Initiative and Harvard University's Lab for Innovation Science have teamed up on a census of the most critical open-source components in today's production applications. The report [PDF], titled "Vulnerabilities in the core", identified more than 200 projects and details 20 of them. More information can be found in the press release and, of course, the report. "This Census II analysis and report represent important steps towards understanding and addressing structural and security complexities in the modern day supply chain where open source is pervasive, but not always understood. Census II identifies the most commonly used free and open source software (FOSS) components in production applications and begins to examine them for potential vulnerabilities, which can inform actions to sustain the long-term security and health of FOSS. Census I (2015) identified which software packages in the Debian Linux distribution were the most critical to the kernel’s operation and security."

Security updates have been issued by CentOS (firefox, java-1.7.0-openjdk, ksh, and sudo), Debian (php7.0 and python-django), Fedora (cacti, cacti-spine, mbedtls, and thunderbird), openSUSE (chromium, re2), Oracle (firefox, java-1.7.0-openjdk, and sudo), Red Hat (openjpeg2 and sudo), Scientific Linux (java-1.7.0-openjdk and sudo), SUSE (dbus-1, dpdk, enigmail, fontforge, gcc9, ImageMagick, ipmitool, php72, sudo, and wicked), and Ubuntu (clamav, linux, linux-aws, linux-aws-hwe, linux-azure, linux-gcp, linux-gke-4.15, linux-hwe, linux-kvm, linux-oracle, linux-raspi2, linux-snapdragon, linux, linux-aws, linux-kvm, linux-raspi2, linux-snapdragon, linux-aws-5.0, linux-azure, linux-gcp, linux-gke-5.0, linux-oracle-5.0, linux-azure, linux-kvm, linux-oracle, linux-raspi2, linux-raspi2-5.3, linux-lts-xenial, linux-aws, and qemu).

The idea behind kernel address-space layout randomization (KASLR) is to make it harder for attackers to find code and data of interest to use in their attacks by loading the kernel at a random location. But a single random offset is used for the placement of the kernel text, which presents a weakness: if the offset can be determined for anything within the kernel, the addresses of other parts of the kernel are readily calculable. A new "finer-grained" KASLR patch set seeks to remedy that weakness for the text section of the kernel by randomly reordering the functions within the kernel code at boot time.

A bit belatedly, Kees Cook looks at some security-relevant changes in Linux 5.4 in a blog post. He lists a small handful of changes, including: "After something on the order of 8 years, Linux can now draw a bright line between 'ring 0' (kernel memory) and 'uid 0' (highest privilege level in userspace). The 'kernel lockdown' feature, which has been an out-of-tree patch series in most Linux distros for almost as many years, attempts to enumerate all the intentional ways (i.e. interfaces not flaws) userspace might be able to read or modify kernel memory (or execute in kernel space), and disable them. While Matthew Garrett made the internal details fine-grained controllable, the basic lockdown LSM can be set to either disabled, 'integrity' (kernel memory can be read but not written), or 'confidentiality' (no kernel memory reads or writes). Beyond closing the many holes between userspace and the kernel, if new interfaces are added to the kernel that might violate kernel integrity or confidentiality, now there is a place to put the access control to make everyone happy and there doesn’t need to be a rehashing of the age old fight between 'but root has full kernel access' vs 'not in some system configurations'."

Security updates have been issued by Arch Linux (systemd and thunderbird), Debian (clamav, libgd2, php7.3, spamassassin, and webkit2gtk), Fedora (kernel, kernel-headers, and sway), Mageia (firefox, kernel-linus, mutt, python-pillow, sphinx, thunderbird, and webkit2), openSUSE (firefox, nextcloud, and thunderbird), Oracle (firefox and ksh), Red Hat (curl, java-1.7.0-openjdk, kernel, and ruby), Scientific Linux (firefox and ksh), SUSE (sudo and xen), and Ubuntu (clamav, php5, php7.0, php7.2, php7.3, postgresql-10, postgresql-11, and webkit2gtk).

The idea of an ID-shifting virtual filesystem that would remap user and group IDs before passing requests through to an underlying real filesystem has been around for a few years but has never made it into the mainline. Implementations have taken the form of shiftfs and shifting bind mounts. Now there is yet another approach to the problem under consideration; this one involves a theoretically simpler approach that makes almost no changes to the kernel's filesystem layer at all.

Security updates have been issued by Debian (evince, postgresql-9.4, and thunderbird), Fedora (ksh and libxml2), openSUSE (hostapd and nextcloud), Red Hat (chromium-browser, firefox, flash-plugin, and ksh), and SUSE (firefox and thunderbird).

The NetBSD 9.0 release is out. "This is the seventeenth major release of the NetBSD operating system and brings significant improvements in terms of hardware support, quality assurance, security, along with new features and hundreds of bug fixes." Significant new features include Arm64 support, better virtualization support, kernel address-space layout randomization, and more; see the release notes for details.

The 5.6-rc2 kernel prepatch is out for testing. Linus says: "More than half the rc2 patch is actually Documentation updates, because the kvm docs got turned into RST. Another notable chunk is just tooling updates, which is about 50/50 perf updates (much of it due to header file syncing) and - again - kvm".

OpenSSH 8.2 is out. This release removes support for the ssh-rsa key algorithm, which may disrupt connectivity to older servers; see the announcement for a way to check whether a given server can handle newer, more secure algorithms. Also new in this release is support for FIDO/U2F hardware tokens.

The 5.5.4, 5.4.20, 4.19.104, 4.14.171, 4.9.214, and 4.4.214 stable kernels have all been released; each contains a relatively large set of important fixes.

Back in November 2019, Mike Rapoport made the case that there is too much address-space sharing in Linux systems. This sharing can be convenient and good for performance, but in an era of advanced attacks and hardware vulnerabilities it also facilitates security problems. At that time, he proposed a number of possible changes in general terms; he has now come back with a patch implementing a couple of address-space isolation options for the memfd mechanism. This work demonstrates the sort of features we may be seeing, but some of the hard work has been left for the future.

Security updates have been issued by Debian (debian-security-support, postgresql-11, and postgresql-9.6), Fedora (cutter-re, firefox, php-horde-Horde-Data, radare2, and texlive-base), openSUSE (docker-runc), Oracle (kernel), Red Hat (sudo), and Ubuntu (firefox).

Stable-kernel updates are, unsurprisingly, supposed to be stable; that is why the first of the rules for stable-kernel patches requires them to be "obviously correct and tested". Even so, for nearly as long as the kernel community has been producing stable update releases, said community has also been complaining about regressions that make their way into those releases. Back in 2016, LWN did some analysis that showed the presence of regressions in stable releases, though at a rate that many saw as being low enough. Since then, the volume of patches showing up in stable releases has grown considerably, so perhaps the time has come to see what the situation with regressions is with current stable kernels.

Security updates have been issued by Arch Linux (dovecot, firefox, ksh, and webkit2gtk), Debian (firefox-esr and openjdk-8), Mageia (exiv2, flash-player-plugin, python-waitress, and vim and neovim), openSUSE (pcp and rubygem-rack), Oracle (kernel), Red Hat (sudo), and Slackware (libarchive).

The LWN.net Weekly Edition for February 13, 2020 is available.

It seems unlikely that anyone on any "side" of the systemd war that has raged in Debian over the last few years thought that the results of the recent general resolution (GR) vote ended the matter. The vote showed a clear preference for moving ahead with systemd as the preferred init system, though it was far from any kind of landslide—there were definitely plenty of voters who would have preferred a different outcome. It was a complicated GR, with a wide spectrum of options, but at this point, the project as a whole has spoken. Actually implementing some of the changes that the GR enabled may not have the smooth path that some might have hoped for, however.

On the Google Project Zero blog, Jann Horn looks at a number of vulnerabilities in a Samsung Android kernel, some of which are caused by the addition of out-of-tree "security" features. "The Samsung kernel on the A50 contains an extra security subsystem (named 'PROCA', short for 'Process Authenticator', with code in security/proca/) to track process identities. By combining several logic issues in this subsystem (which, on their own, can already cause a mismatch between the tracking state and the actual process state) with a brittle code pattern, it is possible to cause memory unsafety by winning a race condition."