KVM clock cleanup and low-level kernel fixes

Kernel development on 2026-08-02 was led by a large KVM clock overhaul together with targeted security fixes in the network scheduler and BPF helpers. Further patches addressed truncation risks in vmalloc, a contested crypto driver stub, and buffer write-error flag handling.

KVM clock series reaches v7

David Woodhouse posted version 7 of a 36-patch series that cleans up the KVM clock implementation. The work fixes imprecision, discontinuities and migration problems by removing pvclock_gtod_data and adding TSC and guest clock APIs. Virtualization developers should track the series because accurate guest timekeeping remains essential for reliable KVM operation.

Qdisc graft hierarchy validation added

A two-patch net series introduces hierarchy depth tracking inside sch_api.c. The change blocks deep qdisc grafts that could exhaust the kernel stack through recursion. Operators of complex traffic-control configurations gain protection against a concrete stack-overflow vector.

Legacy tulip driver rejects runt frames early

A patch to the xircom_cb driver in the tulip family drops runt frames before the skb copy. The change closes a potential underflow and memory-corruption path discovered by an LLM; Greg Kroah-Hartman noted the work as an intern project. Users of this aging hardware receive a defensive fix even though the driver sees little active development.

BPF kfunc prototypes generated from BTF

An 18-patch bpf-next series refactors kfunc argument classification so that it relies solely on BTF. A bpf_func_proto can now be generated and cached at the moment a call is added. BPF subsystem developers obtain cleaner, more maintainable kfunc handling as a result.

vmalloc nr_pages widened to unsigned long

A memory-management patch widens the nr_pages field of vm_struct to unsigned long. The change follows code inspection that revealed two truncation bugs once allocations reach 4 GiB. Large-memory systems avoid silent overflow that previously occurred at that boundary.

QCE crypto driver stub proposal draws NAK

Eric Biggers proposed replacing the QCE crypto driver with a stub on the grounds that its performance is useless. Krzysztof Kozlowski issued a NAK, citing ongoing maintainer work. The exchange underscores differing views on whether to retire low-value hardware support or keep it while active maintenance continues.

fsverity BPF kfunc dynptr assumptions corrected

A patch fixes crash risks in the bpf_get_fsverity_digest kfunc that arose from unstable dynptr contents and a u64-to-int overflow. Callers of the helper no longer face potential kernel faults from those assumptions. BPF and integrity-checking workloads benefit from the defensive correction.

Buffer write failures retain BH_Uptodate

A 19-patch series stops clearing the BH_Uptodate flag when a write fails and instead records the error with BH_Write_EIO across filesystems and jbd2. The change produces more accurate error-state tracking in the buffer layer. Filesystem developers gain clearer failure semantics without the previous misuse of the uptodate bit.