UBUNTU-CVE-2026-98854: Low severity ubuntu/linux-azure vulnerability

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, idrremove() is called with a negative id and listdel() runs on ovcs->ovcslist, which is not initialized until after the id allocation. An allocation failure at that point dereferences NULL. Make freeoverlaychangeset() treat only a strict-positive id as registered. The rest of the function already copes with a partially-initialized ovcs, so the error path stays a plain goto errfreeovcs.