CVE-2025-40218

/// Technical description

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

mm/damon/vaddr: do not repeat pte_offset_map_lock() until success

DAMON's virtual address space operation set implementation (vaddr) calls

pte_offset_map_lock() inside the page table walk callback function. This

is for reading and writing page table accessed bits. If

pte_offset_map_lock() fails, it retries by returning the page table walk

callback function with ACTION_AGAIN.

pte_offset_map_lock() can continuously fail if the target is a pmd

migration entry, though. Hence it could cause an infinite page table walk

if the migration cannot be done until the page table walk is finished.

This indeed caused a soft lockup when CPU hotplugging and DAMON were

running in parallel.

Avoid the infinite loop by simply not retrying the page table walk. DAMON

is promising only a best-effort accuracy, so missing access to such pages

is no problem.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References