Executive brief
A vulnerability in the Linux kernel's control groups (cgroups) component can cause the system to hang or become unresponsive. This occurs when specific system management tasks, such as mounting or unmounting network and performance monitoring tools, are performed repeatedly. An exploit could lead to a denial-of-service condition, impacting system availability and operational stability.
Technical details
A deadlock vulnerability exists in the Linux kernel cgroup subsystem due to a circular dependency in the 'cgroup_destroy_wq' workqueue. When 'max_active' is set to 1, root destruction work can block behind a CSS (cgroup_subsys_state) offline operation that it is simultaneously waiting for. This specifically manifests when repeatedly mounting/unmounting 'perf_event' and 'net_prio' controllers with 'systemd.unified_cgroup_hierarchy=1'. The fix involves splitting the single workqueue into three dedicated queues (offline, release, and free) to ensure that resource deallocation does not block the completion of offline operations. This is a local denial-of-service vulnerability.
Affected products
- Linux Linux Kernel unaffected
- Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.6
Timeline
- 2025-08-19: other: Patch authored
- 2025-09-25: patched: Patch committed to stable tree
- 2025-10-04: advisory: NVD publication date
References
- https://git.kernel.org/stable/c/05e0b03447cf215ec384210441b34b7a3b16e8b0
- https://git.kernel.org/stable/c/4a1e3ec28e8062cd9f339aa6a942df9c5bcb6811
- https://git.kernel.org/stable/c/79f919a89c9d06816dbdbbd168fa41d27411a7f9
- https://git.kernel.org/stable/c/993049c9b1355c78918344a6403427d53f9ee700
- https://git.kernel.org/stable/c/a0c896bda7077aa5005473e2c5b3c27173313b4c
- https://git.kernel.org/stable/c/cabadd7fd15f97090f752fd22dd7f876a0dc3dc4
- https://git.kernel.org/stable/c/ded4d207a3209a834b6831ceec7f39b934c74802