Vue normale

[$] Policy groups for memory management

Par : corbet
14 mai 2026 à 19:02
The kernel's control-group subsystem works well for resource management, Chris Li said at the beginning of his memory-management-track session at the 2026 Linux Storage, Filesystem, Memory Management, and BPF Summit. Control groups work less well for other use cases, though. He was there to present his proposed enhancement, called "policy groups", that would address some of the shortcomings that he has encountered. A consensus on how this feature should look still seems distant, though.

[$] Buffered atomic writes, writethrough, and more

Par : jake
14 mai 2026 à 14:54
In back-to-back sessions at the start of the 2026 Linux Storage, Filesystem, Memory Management, and BPF Summit (which spilled over into a third slot), the atomic-buffered-writes feature was discussed. In the first session, Pankaj Raghav and Andres Freund set the stage with an introduction to the problem, along with a use case for its solution: the PostgreSQL database system. In the second, Ojaswin Mujoo described a potential way forward for the feature using an approach based on writethrough, which effectively means that the kernel immediately writes the data to disk instead of waiting for writeback from the page cache to occur. As might be expected, there was quite a bit of discussion among the assembled filesystems and storage developers during the combined sessions for those tracks.

[$] Keeping COWs in context (a.k.a. anonymous reverse mapping)

Par : corbet
14 mai 2026 à 13:14
The kernel's reverse-mapping machinery is charged with locating the page-table entries that refer to a given page in memory. The reverse mapping of anonymous pages is handled differently than for file-backed pages. The kernel's implementation of reverse mapping for anonymous pages is, according to Lorenzo Stoakes in his proposal for a memory-management-track session at the 2026 Linux Storage, Filesystem, Memory Management, and BPF Summit, "a very broken abstraction", due to its complexity. It also has some performance problems. Stoakes was there to present, in raw form, a proposed replacement that he calls a "COW context".

Security updates for Thursday

Par : jzb
14 mai 2026 à 13:09
Security updates have been issued by AlmaLinux (gimp, jq, and yggdrasil), Debian (nghttp2 and thunderbird), Fedora (chromium, firefox, freerdp, GitPython, kernel, kernel-headers, krb5, nano, nix, nodejs20, php, python-click, python-django5, SDL2_image, and xen), Mageia (dnsmasq, flatpak, kernel, kmod-virtualbox, kernel-linus, perl-Net-CIDR-Lite, perl-XML-LibXML, and redis), SUSE (dnsmasq, firefox, jupyter-jupyterlab, kernel, krb5, libvinylapi3, log4j, Mesa, mozjs60, NetworkManager, OpenImageIO, python-Mako, python-Pillow, and python39), and Ubuntu (dnsmasq and nginx).

[$] LWN.net Weekly Edition for May 14, 2026

Par : corbet
14 mai 2026 à 01:04
Inside this week's LWN.net Weekly Edition:

  • Front: Fedora AI; Forgejo "carrot" disclosure; memory-management maintainership; huge THPs; mshare; 64KB base pages; DAMON; direct map.
  • Briefs: Dirty Frag; Fragnesia; Mythos and curl; killswitch; Debian reproducible builds; KDE investment; Quotes ...
  • Announcements: Newsletters, conferences, security updates, patches, and more.

[$] Friction in Fedora over AI developer desktop initiative

Par : jzb
13 mai 2026 à 16:05

A push by Red Hat employees to create a Fedora "AI Developer Desktop" with support for out-of-tree kernel drivers and AI toolkits has been met with objections from some long-time members of the Fedora community. After more than a month of sometimes heated discussion, the Fedora Council had voted to approve the initiative; however, a last-minute change to vote against the proposal by council member Justin Wheeler has (at least temporarily) sent it back to the drawing board.

Yet another Dirty Frag type vulnerability: Fragnesia

Par : jzb
13 mai 2026 à 15:26

Sam James has sent an announcement to the OSS Security mailing list about another local-privilege-escalation (LPE) exploit in the same class as Dirty Frag, called "Fragnesia". From the disclosure:

This is a separate bug in the ESP/XFRM from dirtyfrag which has received its own patch. However, it is in the same surface and the mitigation is the same as for dirtyfrag.

It abuses a logic bug in the Linux XFRM ESP-in-TCP subsystem to achieve arbitrary byte writes into the kernel page cache of read-only files, without requiring any race condition.

James noted that there is a patch in the works, but it has not yet been pulled into Linus Torvalds's tree nor into any of the stable kernels. A proof of concept exploit is also available.

[$] Managing pages outside of the direct map

Par : corbet
13 mai 2026 à 14:20
When Brendan Jackman proposed a session for the 2026 Linux Storage, Filesystem, Memory Management, and BPF Summit, his topic was "a pagetable library for the kernel". During the actual memory-management-track session, though, he stated that the idea had "fizzled" and he was going to cover related topics instead. What resulted was a session on ways to efficiently manage pages that are not present in the kernel's direct map.

[$] Revisiting mshare

Par : corbet
13 mai 2026 à 13:19
Linux can share memory between processes, but each process (almost always) has its own set of page tables. In situations where vast numbers of processes are sharing a memory region, the combined size of the page tables can exceed that of the shared memory itself. There has, thus, long been an interest in enabling unrelated processes to share page tables referring to shared memory. Anthony Yznaga is the latest developer to try to push this idea (known as "mshare") forward; he described the status of that work in a memory-management-track discussion at the 2026 Linux Storage, Filesystem, Memory Management, and BPF Summit (LSFMM+BPF).

Security updates for Wednesday

Par : jzb
13 mai 2026 à 13:17
Security updates have been issued by AlmaLinux (corosync, freerdp, git-lfs, glib2, jq, kernel-rt, krb5, libpng, libtiff, openexr, and thunderbird), Debian (exim4), Mageia (apache, perl-Gazelle, php, and sed), Slackware (expat), SUSE (assimp-devel, go1.26, libQt6Svg6, python-jupyterlab, raylib, thunderbird, tor, and trivy), and Ubuntu (exim4).

Sovereign Tech Fund invests in KDE

Par : corbet
13 mai 2026 à 13:09
The KDE project has announced that it has been awarded over €1 million from the Sovereign Tech Fund to improve its desktop-environment software. "The investment will be used to strengthen the structural reliability and security of KDE's core infrastructure, including Plasma, KDE Linux, and the frameworks underlying its communication services."

[$] Using dma-bufs for read and write operations

Par : corbet
12 mai 2026 à 17:25
The kernel's dma-buf subsystem provides a way for drivers to share memory buffers, usually in order to support efficient device-to-device I/O. At the 2026 Linux Storage, Filesystem, Memory Management, and BPF Summit, Pavel Begunkov, assisted by Kanchan Joshi, led a joint session of the storage and memory-management tracks to explore ways to make the use of dma-bufs more efficient yet, and to make them available for read and write operations initiated by user space.

[$] Scaling transparent huge pages to 1GB

Par : corbet
12 mai 2026 à 13:24
As a general rule, when developers talk about huge pages, they are referring to PMD-level pages that are 1MB or 2MB in size, depending on the CPU architecture. Most CPUs can support other huge-page sizes, though. On x86 systems, PUD-level huge pages hold 1GB of data. Providing such large pages transparently to processes has generally not been considered as either feasible or desirable, but Usama Arif is trying to change that assessment. At the 2026 Linux Storage, Filesystem, Memory Management, and BPF Summit, he led a session in the memory-management track on how to make transparent huge pages (THPs) truly huge.

Security updates for Tuesday

Par : jzb
12 mai 2026 à 13:17
Security updates have been issued by AlmaLinux (freerdp, glib2, libsoup3, and openexr), Debian (dnsmasq, p7zip, p7zip-rar, python-authlib, and rails), Fedora (chromium, firefox, httpd, and nss), SUSE (java-25-openj9, krb5, libmodsecurity3, and mcphost), and Ubuntu (imagemagick, linux, linux-aws, linux-aws-fips, linux-aws-hwe, linux-azure-4.15, linux-fips, linux-gcp, linux-gcp-4.15, linux-gcp-fips, linux-hwe, linux-kvm, linux-oracle, linux-azure, linux-azure-fips, linux-oracle, linux-azure-5.15, linux-nvidia, linux-nvidia-6.8, linux-nvidia-lowlatency, and linux-raspi).

Stenberg: Mythos finds a curl vulnerability

Par : jzb
11 mai 2026 à 14:35

Daniel Stenberg has published a lengthy article on his thoughts on Anthropic's Mythos, which the company decided was too dangerous for wide public release.

My personal conclusion can however not end up with anything else than that the big hype around this model so far was primarily marketing. I see no evidence that this setup finds issues to any particular higher or more advanced degree than the other tools have done before Mythos. Maybe this model is a little bit better, but even if it is, it is not better to a degree that seems to make a significant dent in code analyzing.

This is just one source code repository and maybe it is much better on other things. I can only tell and comment on what it found here.

But allow me to highlight and reiterate what I have said before: AI powered code analyzers are significantly better at finding security flaws and mistakes in source code than any traditional code analyzers did in the past. All modern AI models are good at this now. Anyone with time and some experimental spirits can find security problems now. The high quality chaos is real.

[$] Providing 64KB base pages with 4KB kernels, two different ways

Par : corbet
11 mai 2026 à 13:35
Some CPU architectures are able to run with a number of different base-page sizes; using a larger size can often result in better performance at the cost of increased memory use. Other architectures are more limited. At the 2026 Linux Storage, Filesystem, Memory Management, and BPF Summit, two sessions in the memory-management track explored options for letting processes run with 64KB page sizes when the underlying kernel does not. The first was focused on letting each process have its own page size, while the second concerned bringing 64KB pages to x86 systems.

Debian to require reproducible builds

Par : corbet
11 mai 2026 à 13:21
Paul Gevers has slipped an interesting bit of news into a "bits from the release team" message:

Aided by the efforts of the Reproducible Builds project, we've decided it's time to say that Debian must ship reproducible packages. Since yesterday, we have enabled our migration software to block migration of new packages that can't be reproduced or existing packages (in testing) that regress in reproducibility.

As Gioele Barabucci pointed out, "reproducible" in this sense is limited to building within an instance of Debian's build environment, which is a tighter requirement than is normally used. It is still a big step forward for reproducible builds.

Security updates for Monday

Par : jzb
11 mai 2026 à 13:10
Security updates have been issued by AlmaLinux (corosync, freeipmi, kernel, and kernel-rt), Debian (corosync, firefox-esr, kernel, lcms2, libpng1.6, linux-6.1, php8.2, php8.4, postorius, pyjwt, and tor), Fedora (dotnet10.0, exim, gnutls, kernel, nextcloud, nodejs22, php, proftpd, prosody, python-pulp-glue, python-requests, rclone, and SDL3_image), Mageia (firefox, nss, rootcerts, openvpn, thunderbird, and vim), Oracle (corosync, freeipmi, gstreamer1-plugins-bad-free, gstreamer1-plugins-base, and gstreamer1-plugins-good, kernel, libpng, and mingw-libtiff), Slackware (kernel and mozilla), SUSE (build, product-composer, c-ares, cairo, copacetic, distribution, firefox, firefox-esr, frr, glibc, go1.25, google-cloud-sap-agent, iproute2, java-11-openj9, java-17-openj9, java-17-openjdk, java-1_8_0-openj9, java-21-openj9, java-21-openjdk, java-25-openjdk, kernel, libexif-devel, libpcp-devel, libtpms, libtree-sitter0_26, Mesa, micropython, mozjs128, nginx, opencc, openCryptoki, php-composer2, podman, postfix, python-pytest, python311-Django, python311-Django4, redis, semaphore, strongswan, terraform-provider-aws, terraform-provider-azurerm, terraform-provider-external, terraform-provider-google, terraform-provider-helm, terraform-provider-kubernetes, terraform-provid, tor, valkey, vim, and wireshark), and Ubuntu (linux-nvidia-tegra, linux-raspi, linux-raspi-5.4, and nasm).
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