CVE-2026-90358

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

bpf, x86: Fix trampoline stack size for 128-bit arguments

btf_distill_func_proto() accepts a function argument up to 16 bytes, so a
128-bit scalar such as __int128 reaches the x86 trampoline with
arg_size == 16. But the current implementation assumes an __int128
argument only needs one register, so the register save area is
under-allocated and save_args() overwrites adjacent stack slots.

Compute the register count from arg_size for all arguments to fix it.