CVE-2026-31664

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

xfrm: clear trailing padding in build_polexpire()

build_expire() clears the trailing padding bytes of struct

xfrm_user_expire after setting the hard field via memset_after(),

but the analogous function build_polexpire() does not do this for

struct xfrm_user_polexpire.

The padding bytes after the __u8 hard field are left

uninitialized from the heap allocation, and are then sent to

userspace via netlink multicast to XFRMNLGRP_EXPIRE listeners,

leaking kernel heap memory contents.

Add the missing memset_after() call, matching build_expire().