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

Official 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 packages & fixed versions

Affected products (as reported)

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