Kbuild speedups, AF_UNIX fix, and Apple USB4 land

Kernel traffic on 2026-09-16 centered on a large kbuild overhaul claiming much faster builds, with active review from Linus and maintainers, alongside a stable backport for an AF_UNIX use-after-free and continued work on Apple Silicon USB4 support. Several BPF, arm64, networking, and Rust block patches also advanced, including a heated dispute over Landlock integration.

Kbuild series aims at much faster kernel builds

A v2 21-patch kbuild series proposes parallelizing known bottlenecks and reports build time reductions in the 36 to 90 percent range depending on configuration. Linus Torvalds and other maintainers are actively reviewing the changes on linux-kernel. Developers who rebuild frequently should watch whether the approach lands cleanly, given the scale of the claimed wins.

Stable backport sought for AF_UNIX UAF

A one-line fix for CVE-2026-80521, a use-after-free in AF_UNIX garbage collection when unlinking scc_entry in unix_del_edge(), has been requested for backport to four long-term stable kernels. The request went to stable@ with minimal discussion so far. Anyone shipping LTS kernels or AF_UNIX-heavy workloads has a clear interest in seeing the fix propagate.

Initial USB4 and Thunderbolt for Apple M1/M2/M3

A v2 22-patch series adds first-cut USB4/Thunderbolt support for Apple M1, M2, and M3 SoCs, covering ACIO, NHI, and DART pieces plus device-tree nodes. Discussion on linux-kernel involves a small set of participants refining the hardware enablement. This matters for upstream laptop and desktop support on those platforms once the series stabilizes.

BPF LSM xattrs at inode creation

An eight-patch bpf-next series introduces a bpf_inode_init_xattr kfunc so BPF LSM programs can set extended attributes atomically inside inode_init_security. Five participants are iterating on the design. The change would let security policies attach metadata at create time without races that later setattr paths can introduce.

Dispute over BPF interface to Landlock rulesets

A v3 15-patch series offering a BPF interface to apply Landlock rulesets drew objections from the BPF maintainer over LSM kfuncs, stability guarantees, and community friction, with the LSM side pushing back. The thread on bpf remains heated across eight participants. The outcome will shape how far BPF programs can drive Landlock policy without bypassing established LSM boundaries.

arm64 moves toward Generic Entry

Version 18 of a 14-patch series converts arm64 entry code to the generic entry framework already used on x86, RISC-V, and others, shrinking architecture-specific syscall paths. The series is largely from a single author with limited external mail so far. Alignment should ease maintenance and future entry-path features shared across architectures.

In-kernel QUIC infrastructure on net-next

A v15 15-patch set posts core QUIC transport, a socket API, and helpers aimed at in-kernel consumers on netdev. Two participants are carrying the discussion. The work is a prerequisite for native QUIC use inside the stack rather than only via userspace libraries.

Rust block layer soundness fix

A single patch marks the block Operations trait unsafe to close a soundness hole in queue_rq where an ARef could be retained across an error return and enable a use-after-free. Three participants discussed the change on rust-for-linux. Rust drivers using the block mq path need the trait contract clarified to keep unsafe obligations explicit.