CVE-2026-93150cgroup/cpuset: Make nr_deadline_tasks an atomic_t

Official description

In the Linux kernel, the following vulnerability has been resolved: cgroup/cpuset: Make nr_deadline_tasks an atomic_t The nr_deadline_tasks variable in the cpuset structure was introduced by commit 6c24849f5515 ("sched/cpuset: Keep track of SCHED_DEADLINE task in cpusets"). It is reported by sashiko [1] that nr_deadline_tasks can currently be modified by inc_dl_tasks_cs() under rq->lock and by cpuset_attach() under cpuset_mutex. So if both updates happen simultaneously, the nr_deadline_tasks variable can be corrupted leading to incorrect operations down the road. Fix that by changing its type to atomic_t so that nr_deadline_tasks are always atomically updated. This fix patch is a low hanging fruit. It can handle some of the races between a concurrent sched_setscheduler() and cpuset_can_attach()/cpuset_attach() calls, but not all of them like the other issue raised by sashiko [2]. This will be handled hopefully in a future follow up patch. [1] https://sashiko.dev/#/patchset/20260626181923.133658-1-longman%40redhat.com [2] https://sashiko.dev/#/patchset/20260630033344.352702-1-longman%40redhat.com

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/4987d336abf3fa575a2d953f69e11154ac9802c3
• https://git.kernel.org/stable/c/642648fa7595241e4d491add5007bc33f11defb5
• https://git.kernel.org/stable/c/e422b32e6a57269ca8164c60674a78bee85cf5fb
• https://git.kernel.org/stable/c/e5965ae3f7c918151b87e5c925b7978afbeaf638
• https://git.kernel.org/stable/c/78d9daf5e13ad1448b7dfebac949936710ec7565
• https://git.kernel.org/stable/c/95220e1f18f6321008f021abc7d6f581f64bcb82