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

Severity: unknown
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-11 · updated 2026-10-21

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.

Affected products

Linux kernel: from 5.15.129 before 5.16; from 6.1.50 before 6.2; from 6.4.13 before 6.5; 6.5 — fixed in 5.16, 6.2, 6.5, 7.3

How to fix

Upgrade to a fixed version: Linux kernel 5.16, 6.2, 6.5, 7.3. Check the vendor advisory for mitigations.

References

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