CVE-2026-64180: Undefined Security Weakness

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

mm/memory_hotplug: fix memory block reference leak on remove

Patch series "mm: Fix memory block leaks and locking", v2.

This series fixes two memory block device reference leaks and one locking issue around the per-memory_block hwpoison counter.

This patch (of 2):

remove_memory_blocks_and_altmaps() looks up each memory block with find_memory_block(), which acquires a reference to the memory block device.

That reference is never dropped on this path, resulting in a leaked device reference when removing memory blocks and their altmaps. Drop the reference after retrieving mem->altmap and clearing mem->altmap, before removing the memory block device.