kbuild speedups, ksmbd stable gaps, Squashfs fixes

Kernel traffic centered on a large kbuild series promising substantially faster builds, two critical ksmbd fixes omitted from the 5.15 stable branch, and assorted filesystem and attestation hardening. Security and build-system work dominated the day's low-level discussion.

kbuild series claims major build speedups

A 23-patch kbuild series posted to linux-kernel proposes parallelization and Kconfig caching changes that the author says can cut allmodconfig build times by up to 36 percent. Linus Torvalds and eleven other participants are reviewing the patches across more than 100 messages. Kernel developers and distribution packagers have a direct stake in any accepted improvements to compile throughput.

ksmbd EA alignment OOB write missing from 5.15.y

A request on the stable list notes that the ksmbd out-of-bounds write fix for CVE-2026-31705 (CVSS 9.8) reached six other stable branches yet was never applied to 5.15.y. The single message asks for the EA alignment patch to be backported. Systems still running the 5.15 long-term series therefore remain exposed to a high-severity SMB server flaw.

ksmbd tree-connection UAF also absent from 5.15.y

A companion report flags that the ksmbd use-after-free fix for CVE-2026-89788 (CVSS 9.8) was likewise backported elsewhere but omitted from 5.15.y. The requester seeks inclusion of the tree-connection patch on that branch. The gap leaves another critical remote issue unpatched for remaining 5.15 users.

Squashfs series closes overflow and sanity gaps

The Squashfs maintainer submitted an 18-patch set that corrects arithmetic overflows, variable overflows, and missing sanity checks capable of producing out-of-bounds access or oversized kmalloc calls. Three participants discussed the series over 22 messages. The changes harden the filesystem against crafted images that could trigger memory corruption.

6LoWPAN fragment offset validation

A one-line style patch for ieee802154 6lowpan adds an explicit check that fragment offsets stay inside the datagram size during reassembly. Without the test, forged fragments can mark a datagram complete. Stacks that process 6LoWPAN traffic gain a straightforward defense against this reassembly abuse.

F2FS support for sub-PAGE_SIZE blocks

Google posted a 20-patch series that lets F2FS use block sizes smaller than PAGE_SIZE, primarily to ease Android userdata migration onto 16 KB page kernels. Two participants exchanged 33 messages on the design. Android and embedded maintainers running large-page configurations stand to gain filesystem flexibility from the work.

FPGA DFL AFU read-only mapping fix

A v2 patch for the FPGA DFL AFU driver clears VM_MAYWRITE so that read-only port mappings cannot be upgraded to writable via mprotect. The change closes a guest isolation hole. Virtualization environments that expose this FPGA interface obtain tighter memory protection.

Common attestation subsystem RFC with TDX

An RFC of 20 patches introduces a shared attestation subsystem and CTLV UAPI, starting with Intel TDX and leaving room for other providers. Fifteen reviewers generated more than 200 messages covering validation, nesting, event delivery, and configuration. Confidential-computing developers now have a concrete interface proposal under active scrutiny.