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Linux Kernel: Potential Deadlock in Scheduling System
published 6 months ago
Summary
A bug in the Linux kernel scheduling system could cause a group of computers to freeze indefinitely. This issue has been fixed to prevent such a situation. Affected systems should be updated to the latest version of the Linux kernel to ensure stability and prevent potential crashes.
What to do
- Update linux kernel to version 6.19.12.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| Linux | linux | kernel |
>= 6.12.0, < 6.19.12 Fix: upgrade to 6.19.12
|
Original advisory text
sched_ext: Fix SCX_KICK_WAIT deadlock by deferring wait to balance callback
In the Linux kernel, the following vulnerability has been resolved:
sched_ext: Fix SCX_KICK_WAIT deadlock by deferring wait to balance callback
SCX_KICK_WAIT busy-waits in kick_cpus_irq_workfn() using
smp_cond_load_acquire() until the target CPU's kick_sync advances. Because
the irq_work runs in hardirq context, the waiting CPU cannot reschedule and
its own kick_sync never advances. If multiple CPUs form a wait cycle, all
CPUs deadlock.
Replace the busy-wait in kick_cpus_irq_workfn() with resched_curr() to
force the CPU through do_pick_task_scx(), which queues a balance callback
to perform the wait. The balance callback drops the rq lock and enables
IRQs following the sched_core_balance() pattern, so the CPU can process
IPIs while waiting. The local CPU's kick_sync is advanced on entry to
do_pick_task_scx() and continuously during the wait, ensuring any CPU that
starts waiting for us sees the advancement and cannot form cyclic
dependencies.
sched_ext: Fix SCX_KICK_WAIT deadlock by deferring wait to balance callback
SCX_KICK_WAIT busy-waits in kick_cpus_irq_workfn() using
smp_cond_load_acquire() until the target CPU's kick_sync advances. Because
the irq_work runs in hardirq context, the waiting CPU cannot reschedule and
its own kick_sync never advances. If multiple CPUs form a wait cycle, all
CPUs deadlock.
Replace the busy-wait in kick_cpus_irq_workfn() with resched_curr() to
force the CPU through do_pick_task_scx(), which queues a balance callback
to perform the wait. The balance callback drops the rq lock and enables
IRQs following the sched_core_balance() pattern, so the CPU can process
IPIs while waiting. The local CPU's kick_sync is advanced on entry to
do_pick_task_scx() and continuously during the wait, ensuring any CPU that
starts waiting for us sees the advancement and cannot form cyclic
dependencies.
References
- https://git.kernel.org/stable/c/415cb193bb9736f0e830286c72a6fa8eb2a9cc5c URL
- https://git.kernel.org/stable/c/c3a7903f65cf4c7fb0477eb0f8b94f326a47fe54 URL
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43326... Vendor Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2026-43326 Vendor Advisory
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git Product
Timeline
Published8 May 2026
Updated16 Jul 2026
First seen16 Jul 2026
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