UBUNTU-CVE-2026-97944: Medium severity ubuntu/linux-hwe-edge vulnerability

In the Linux kernel, the following vulnerability has been resolved: x86/cfi: Fix FineIBT hash offset in cfigetfunchash() The switch of the FineIBT preamble from "subl $hash, %r10d" to the shorter "subl $hash, %eax" moved the hash immediate from offset 7 to offset 5 of the preamble. fineibtpreamblehash was updated to match, but the open-coded offset in cfigetfunchash() was missed and it still reads the hash at offset 7. cfigetfunchash() is used by the BPF JIT to give a structops trampoline the CFI hash of the stub function it stands in for. With FineIBT the trampoline now gets the upper half of the real hash followed by the first two bytes of the next instruction, so the first indirect call from the kernel into a structops program, tcpinitcongestioncontrol() calling ->init() of a BPF congestion control for example, fails the FineIBT check and the kernel dies with a CFI failure. Move the FineIBT preamble template and its offset defines above cfigetfunchash() and use fineibtpreamblehash there, so every reader of the preamble shares one definition of its layout. The CFIFINEIBT arm is only built with CONFIGFINEIBT, the only configuration in which cfimode can take that value. cfigetfuncarity() does not need the same treatment: the bhiargs call whose displacement it reads still ends at the function address.