CVE-2026-89759 is a vulnerability in Linux Kernel
Published on September 11, 2026
mm/kmemleak: avoid soft lockup when scanning task stacks
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.
Products Associated with CVE-2026-89759
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Affected Versions
Linux:- Version c4b28963fd79457315783b3b0f21c01eb88cfdc1 and below 9a1b12c06c192290b8479de48f66f1e75d89c4b7 is affected.
- Version c4b28963fd79457315783b3b0f21c01eb88cfdc1 and below 3fc8044251de21555fb02c365fa681bab8b0db55 is affected.
- Version c4b28963fd79457315783b3b0f21c01eb88cfdc1 and below 1838c704bcb4fd3556cf67513c6f97a39099e35c is affected.
- Version c4b28963fd79457315783b3b0f21c01eb88cfdc1 and below 5d10d4e19e6daa487f0cd0ea6cba472325de92f9 is affected.
- Version 5.10 is affected.
- Before 5.10 is unaffected.
- Version 6.12.109, <= 6.12.* is unaffected.
- Version 6.18.50, <= 6.18.* is unaffected.
- Version 7.2.4, <= 7.2.* is unaffected.
- Version 7.3-rc1, <= * is unaffected.