Kernel races, virtual swap, and stable fixes

Kernel traffic on 2026-08-26 focused on signal and futex race fixes reaching stable trees, plus large memory and device proposals. Maintainers also advanced console conversion and page-attribute hardening.

Signal queue flush race

A patch changes flush_sigqueue() to use list_del_init_careful() after discussion of a race between lockless queue flushing and POSIX timer delivery following non-leader execve. Multiple participants on linux-kernel examined the locking and lifetime issues. The change matters because the race can corrupt signal state in multi-threaded processes that exec.

Virtual swap space v4

Nhat Pham posted the fourth revision of virtual swap patches that introduce a 16 TB virtual device and swap-table indirection for zswap and zero-page backends. The series reworks how swap entries are tracked without a traditional block device. Developers tracking compressed or memory-backed swap will want to review the indirection model.

Futex PI fixes for stable

A batch of futex private-hash and PI-state race fixes, including rejection of cross-mm private futex owners, failed to apply cleanly to the 7.1-stable tree and then moved forward after correction. The work closes races around owner tracking across address spaces. Stable users running older kernels gain protection against those PI-state bugs.

io_uring folio overflow fix

Stable received a backport of an io_uring resource fix that prevents an integer shift overflow on large folios inside io_vec_fill_bvec(). The overflow could produce a buffer overrun when building bio vectors. The change is relevant for anyone running io_uring workloads on kernels with large-folio support.

8250 NBCON conversion v11

Version 11 of the 8250 serial driver conversion to the NBCON console model was posted, and Greg Kroah-Hartman queued it after an earlier revert. The series continues the push to make legacy UART consoles play correctly with modern console locking. Embedded and server platforms that still rely on 8250 hardware are the primary audience.

Collapse rebuild on migration

A 57-patch RFC rebuilds anonymous THP collapse on top of migration primitives so khugepaged can support multi-size THP on architectures with large base pages. Discussion spanned bpf and mm lists with nine participants. The redesign affects page-collapse latency and correctness for large-page workloads.

CXL Type-2 VFIO passthrough

The fourth version of a VFIO PCI series adds passthrough support for CXL Type-2 devices, allowing guests to program virtual HDM decoders and participate in resets. Three participants iterated on the interface. It enables virtualized CXL memory expanders and accelerators without host mediation of every decode.

x86 CPA race and UAF fixes

A five-patch series corrects races, use-after-frees, and an RWX permission check bug in the x86 change-page-attribute path. Seven developers reviewed the locking and TLB interactions. Correct PAT attribute updates are required for secure W^X enforcement and device mappings.