CVE-2026-97944

In the Linux kernel, the following vulnerability has been resolved:

x86/cfi: Fix FineIBT hash offset in cfi get func hash()

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. fineibt preamble hash was updated to match, but the open-coded offset in cfi get func hash() was missed and it still reads the hash at offset 7.

cfi get func hash() is used by the BPF JIT to give a struct ops 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 struct ops program, tcp init congestion control() 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 cfi get func hash() and use fineibt preamble hash there, so every reader of the preamble shares one definition of its layout. The CFI FINEIBT arm is only built with CONFIG FINEIBT, the only configuration in which cfi mode can take that value. cfi get func arity() does not need the same treatment: the bhi args call whose displacement it reads still ends at the function address.