Description
In the Linux kernel, the following vulnerability has been resolved: cgroup: split cgroup_destroy_wq into 3 workqueues A hung task can occur during [1] LTP cgroup testing when repeatedly mounting/unmounting perf_event and net_prio controllers with systemd.unified_cgroup_hierarchy=1. The hang manifests in cgroup_lock_and_drain_offline() during root destruction. Related case: cgroup_fj_function_perf_event cgroup_fj_function.sh perf_event cgroup_fj_function_net_prio cgroup_fj_function.sh net_prio Call Trace: cgroup_lock_and_drain_offline+0x14c/0x1e8 cgroup_destroy_root+0x3c/0x2c0 css_free_rwork_fn+0x248/0x338 process_one_work+0x16c/0x3b8 worker_thread+0x22c/0x3b0 kthread+0xec/0x100 ret_from_fork+0x10/0x20 Root Cause: CPU0 CPU1 mount perf_event umount net_prio cgroup1_get_tree cgroup_kill_sb rebind_subsystems // root destruction enqueues // cgroup_destroy_wq // kill all perf_event css // one perf_event css A is dying // css A offline enqueues cgroup_destroy_wq // root destruction will be executed first css_free_rwork_fn cgroup_destroy_root cgroup_lock_and_drain_offline // some perf descendants are dying // cgroup_destroy_wq max_active = 1 // waiting for css A to die Problem scenario: 1. CPU0 mounts perf_event (rebind_subsystems) 2. CPU1 unmounts net_prio (cgroup_kill_sb), queuing root destruction work 3. A dying perf_event CSS gets queued for offline after root destruction 4. Root destruction waits for offline completion, but offline work is blocked behind root destruction in cgroup_destroy_wq (max_active=1) Solution: Split cgroup_destroy_wq into three dedicated workqueues: cgroup_offline_wq – Handles CSS offline operations cgroup_release_wq – Manages resource release cgroup_free_wq – Performs final memory deallocation This separation eliminates blocking in the CSS free path while waiting for offline operations to complete. [1] https://github.com/linux-test-project/ltp/blob/master/runtest/controllers
Product status
334c3679ec4b2b113c35ebe37d2018b112dd5013 before cabadd7fd15f97090f752fd22dd7f876a0dc3dc4
334c3679ec4b2b113c35ebe37d2018b112dd5013 before a0c896bda7077aa5005473e2c5b3c27173313b4c
334c3679ec4b2b113c35ebe37d2018b112dd5013 before f2795d1b92506e3adf52a298f7181032a1525e04
334c3679ec4b2b113c35ebe37d2018b112dd5013 before 993049c9b1355c78918344a6403427d53f9ee700
334c3679ec4b2b113c35ebe37d2018b112dd5013 before 4a1e3ec28e8062cd9f339aa6a942df9c5bcb6811
334c3679ec4b2b113c35ebe37d2018b112dd5013 before ded4d207a3209a834b6831ceec7f39b934c74802
334c3679ec4b2b113c35ebe37d2018b112dd5013 before 05e0b03447cf215ec384210441b34b7a3b16e8b0
334c3679ec4b2b113c35ebe37d2018b112dd5013 before 79f919a89c9d06816dbdbbd168fa41d27411a7f9
4.6
Any version before 4.6
5.4.300
5.10.245
5.15.194
6.1.154
6.6.108
6.12.49
6.16.9
6.17
References
git.kernel.org/...c/cabadd7fd15f97090f752fd22dd7f876a0dc3dc4
git.kernel.org/...c/a0c896bda7077aa5005473e2c5b3c27173313b4c
git.kernel.org/...c/f2795d1b92506e3adf52a298f7181032a1525e04
git.kernel.org/...c/993049c9b1355c78918344a6403427d53f9ee700
git.kernel.org/...c/4a1e3ec28e8062cd9f339aa6a942df9c5bcb6811
git.kernel.org/...c/ded4d207a3209a834b6831ceec7f39b934c74802
git.kernel.org/...c/05e0b03447cf215ec384210441b34b7a3b16e8b0
git.kernel.org/...c/79f919a89c9d06816dbdbbd168fa41d27411a7f9
