CVE-2026-98854 of/overlay: only treat a positive changeset id as registered

In the Linux kernel, the following vulnerability has been resolved: of/overlay: only treat a positive changeset id as registered ofoverlayfdtapply stores the idralloc return value in ovcs-id before checking it. On failure the stored id is negative, freeoverlaychangeset's "if ovcs-id" check passes...