# CVE-2026-89759

## Summary

- **CVE ID:** CVE-2026-89759
- **Severity:** UNKNOWN
- **CVSS Score:** 0
- **CWE:** N/A
- **Published:** Sep 11, 2026
- **Last Modified:** Sep 16, 2026

## Description

In the Linux kernel, the following vulnerability has been resolved:

mm/kmemleak: avoid soft lockup when scanning task stacks

Patch series "mm/kmemleak: avoid soft lockup when scanning task", v3.

kmemleak_scan() scans every task stack under one rcu_read_lock() with no
reschedule point, which can trip the soft lockup watchdog on hosts with
very many threads.

That prints the following message, depending on the workload+host
configuration:

      watchdog: BUG: soft lockup - CPU#35 stuck for 22s! [kmemleak:537]
       scan_block
       kmemleak_scan
       kmemleak_scan_thread
       kthread

Patch 1 walks the tasks with find_ge_pid() so the scan reschedules between
tasks

Patches 2-3 let the scan loops stop early once a scan is interrupted.


This patch (of 3):

kmemleak_scan() walks every thread and scans its kernel stack under a
single rcu_read_lock() with no reschedule point.  On a host with very many
threads -- amplified by KASAN/lockdep in debug builds -- this loop can hog
a CPU long enough to trip the soft lockup watchdog:

  watchdog: BUG: soft lockup - CPU#35 stuck for 22s! [kmemleak:537]
   scan_block
   kmemleak_scan
   kmemleak_scan_thread
   kthread

A cond_resched() cannot be added directly: the loop runs inside an RCU
read-side critical section.

Walk the tasks one PID at a time with find_ge_pid(), taking the RCU read
lock only to look up and pin each task.  The stack is then scanned with no
lock held, so cond_resched() runs between tasks and the scan stops early
on scan_should_stop().  This follows the next_tgid()/task_seq_get_next()
iteration pattern and keeps each RCU critical section short.

## Affected Products

- Linux — Linux (c4b28963fd79457315783b3b0f21c01eb88cfdc1)
- Linux — Linux (5.10)
- Linux — Linux (0)
- Linux — Linux (6.12.109)
- Linux — Linux (6.18.50)
- Linux — Linux (7.2.4)
- Linux — Linux (7.3-rc1)

## References

- [CNA](https://git.kernel.org/stable/c/9a1b12c06c192290b8479de48f66f1e75d89c4b7)
- [CNA](https://git.kernel.org/stable/c/3fc8044251de21555fb02c365fa681bab8b0db55)
- [CNA](https://git.kernel.org/stable/c/1838c704bcb4fd3556cf67513c6f97a39099e35c)
- [CNA](https://git.kernel.org/stable/c/5d10d4e19e6daa487f0cd0ea6cba472325de92f9)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.19%
- **EPSS Percentile:** 8.5

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-17._