Qdisc clamps, VMA locks, and sysctl NAK

Security hardening led kernel discussion, with clamps and capability checks landing against crafted qdisc, Squashfs, ublk, and rmnet inputs. Memory management simplification and a heated sysctl refactor rejection rounded out the day.

Qdisc quantum clamps block size-table DoS

A v2 networking patch series adds missing clamps on quantum and psched_mtu in the change paths of eight qdiscs. The work stops crafted size tables from triggering denial of service while the qdisc lock is held. Packet scheduling code is a common attack surface, so the fix matters for production hosts that accept untrusted traffic shaping configuration.

Linus NAKs sysctl_field macros

Linus Torvalds rejected an RFC converting SCTP sysctls (and related net paths) to a sysctl_field helper, calling the macros and indentation illegible. The author acknowledged the critique and is revising. Core sysctl changes affect every distribution, so readability objections from the top of the tree carry unusual weight.

Per-VMA locks made unconditional

A v6 mm series drops config guards and makes per-VMA locks unconditional, unlocking simplifications in binder and networking. Andrew Morton has picked up the patches. Removing the conditional paths reduces long-term maintenance cost in the virtual memory subsystem.

Squashfs fragment index overflows closed

Two patches harden Squashfs fragment index table sizing against integer overflows. On 32-bit kernels a crafted image could previously produce out of bounds reads. Filesystem image parsers remain a classic vector for untrusted media, so the bounds checks close a concrete information-leak or crash path.

ublk clears VM_MAYWRITE on read-only mmap

A stable-bound fix clears VM_MAYWRITE when mapping the read-only ublk command buffer, blocking later mprotect upgrades. The change matches recent drm and ptp corrections for the same class of error. Userspace block drivers that expose command rings need the mapping flags to stay honest.

Rust irq guard reverted after Syzbot hit

Peter Zijlstra reverted a locking and irq guard change after Syzbot exposed unsafe nested lock patterns inside scoped_guard(spinlock_irq). The larger series on refcounted interrupt disable and SpinLockIrq for Rust remains under discussion. Locking correctness is non-negotiable before more drivers move to Rust.

rmnet config gated by real-netns CAP_NET_ADMIN

A v3 Qualcomm rmnet patch requires CAP_NET_ADMIN inside the real device network namespace for configuration operations. The missing check previously allowed cross-namespace state mutation. Container and multi-tenant setups rely on netns isolation, so the capability gate closes a privilege boundary hole.

prctl control for cache-aware scheduling

An RFC proposes a prctl interface that lets tasks join explicit cache-scheduling groups, decoupling the feature from mm_struct. The design gives finer per-task policy without tying locality decisions to address spaces. Scheduler and performance developers tracking cache-aware placement have a new knobs discussion to follow.