lwn.net

Two new stable kernels
Security updates for Thursday
[$] LWN.net Weekly Edition for May 29, 2025
- Front: Glibc security; How we lost the Internet; Encrypted DNS; 6.15 Development statistics; Filesystem stress-testing; BPF verifier; Network access from BPF; OSPM 2025.
- Briefs: AlmaLinux 10.0; FESCo decision overturned; NixOS 25.05; Pocket, Launchpad retired; Quotes; ...
- Announcements: Newsletters, conferences, security updates, patches, and more.
[$] Glibc project revisits infrastructure security
The GNU C Library (glibc) is the core C library for most Linux distributions, so it is a crucial part of the open-source ecosystem—and an attractive target for any attackers looking to carry out supply-chain attacks. With that being the case, securing the project's infrastructure using industry best practices and improving the security of its development practices are a frequent topic among glibc developers. A recent discussion suggests that improvements are not happening as quickly as some would like.
[$] Allowing BPF programs more access to the network
Mahé Tardy led two sessions about some of the challenges that he, Kornilios Kourtis, and John Fastabend have run into in their work on Tetragon (Apache-licensed BPF-based security monitoring software) at the Linux Storage, Filesystem, Memory Management, and BPF Summit. The session prompted discussion about the feasibility of letting BPF programs send data over the network, as well as potential new kfuncs to let BPF firewalls send TCP reset packets. Tardy presented several possible ways that these could be accomplished.
Launchpad mailing lists going away
Canonical's Launchpad software-collaboration platform that is used for Ubuntu development will be shutting down its hosted mailing lists at the end of October. The announcement recommends Discourse or Launchpad Answers as alternatives. Ubuntu's mailing lists are unaffected by the change.
[$] System-wide encrypted DNS
The increasing sophistication of attackers has organizations realizing that perimeter-based security models are inadequate. Many are planning to transition their internal networks to a zero-trust architecture. This requires every communication on the network to be encrypted, authenticated, and authorized. This can be achieved in applications and services by using modern communication protocols. However, the world still depends on Domain Name System (DNS) services where encryption, while possible, is far from being the industry standard. To address this we, as part of a working group at Red Hat, worked on fully integrating encrypted DNS for Linux systems—not only while the system is running but also during the installation and boot process, including support for a custom certificate chain in the initial ramdisk. This integration is now available in CentOS Stream 9, 10, and the upcoming Fedora 43 release.
Security updates for Wednesday
AlmaLinux OS 10.0 released
The goal of AlmaLinux OS is to support our community, and AlmaLinux OS 10 is the best example of that yet. With an unwavering eye on maintaining compatibility with Red Hat Enterprise Linux (RHEL), we have made small improvements to AlmaLinux OS 10 that target specific sections of our userbase.
See the release notes for details.
[$] Verifying the BPF verifier's path-exploration logic
Srinivas Narayana led a remote session about extending Agni to prove the correctness of the BPF verifier's handling of different execution paths as part of the Linux Storage, Filesystem, Memory Management, and BPF Summit. The problem of ensuring the correctness of path exploration is much more difficult than the problem of ensuring the correctness of arithmetic operations (which was the subject of the previous session), however. Narayana's plan to tackle the problem makes use of a mixture of specialized techniques — and may need some assistance from the BPF developers to make it feasible at all.
[$] Cory Doctorow on how we lost the internet
NixOS 25.05 released
Security updates for Tuesday
[$] Development statistics for the 6.15 kernel
Security updates for Monday
The 6.15 kernel has been released
So this was delayed by a couple of hours because of a last-minute bug report resulting in one new feature being disabled at the eleventh hour, but 6.15 is out there now.
Significant changes in 6.15 include smarter timer-ID assignment to make checkpoint/restore operations more reliable, the ability to read status information from a pidfd after the process in question has been reaped, the PIDFD_SELF special pidfd value, nested ID-mapped mounts, zero-copy network-data reception via io_uring, The ability to read epoll events via io_uring, resilient queued spinlocks for BPF programs, guard-page enhancements allowing them to be placed in file-backed memory areas and for user space to detect their presence, the once-controversial fwctl subsystem, the optional sealing of some system mappings, and much more.
See the LWN merge-window summaries (part 1, part 2) and the in-progress KernelNewbies 6.15 page for more information.
[$] Reports from OSPM 2025, day two
[$] Formally verifying the BPF verifier
The BPF verifier is an increasingly complex and security-critical piece of code. When the kinds of people who are apt to work on BPF see a situation like that, they naturally question whether it's possible to use formal verification to ensure that the implementation of the code in question is correct. Santosh Nagarakatte led the first of two extra-long sessions in the BPF track of the 2025 Linux Storage, Filesystem, Memory Management, and BPF Summit about his team's work formally verifying the BPF verifier with a custom tool called Agni.