ghsa-vgcj-37hg-gm6g
Vulnerability from github
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
{
"affected": [],
"aliases": [
"CVE-2025-39953"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-10-04T08:15:48Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\ncgroup: split cgroup_destroy_wq into 3 workqueues\n\nA hung task can occur during [1] LTP cgroup testing when repeatedly\nmounting/unmounting perf_event and net_prio controllers with\nsystemd.unified_cgroup_hierarchy=1. The hang manifests in\ncgroup_lock_and_drain_offline() during root destruction.\n\nRelated case:\ncgroup_fj_function_perf_event cgroup_fj_function.sh perf_event\ncgroup_fj_function_net_prio cgroup_fj_function.sh net_prio\n\nCall Trace:\n\tcgroup_lock_and_drain_offline+0x14c/0x1e8\n\tcgroup_destroy_root+0x3c/0x2c0\n\tcss_free_rwork_fn+0x248/0x338\n\tprocess_one_work+0x16c/0x3b8\n\tworker_thread+0x22c/0x3b0\n\tkthread+0xec/0x100\n\tret_from_fork+0x10/0x20\n\nRoot Cause:\n\nCPU0 CPU1\nmount perf_event umount net_prio\ncgroup1_get_tree cgroup_kill_sb\nrebind_subsystems // root destruction enqueues\n\t\t\t\t// cgroup_destroy_wq\n// kill all perf_event css\n // one perf_event css A is dying\n // css A offline enqueues cgroup_destroy_wq\n // root destruction will be executed first\n css_free_rwork_fn\n cgroup_destroy_root\n cgroup_lock_and_drain_offline\n // some perf descendants are dying\n // cgroup_destroy_wq max_active = 1\n // waiting for css A to die\n\nProblem scenario:\n1. CPU0 mounts perf_event (rebind_subsystems)\n2. CPU1 unmounts net_prio (cgroup_kill_sb), queuing root destruction work\n3. A dying perf_event CSS gets queued for offline after root destruction\n4. Root destruction waits for offline completion, but offline work is\n blocked behind root destruction in cgroup_destroy_wq (max_active=1)\n\nSolution:\nSplit cgroup_destroy_wq into three dedicated workqueues:\ncgroup_offline_wq \u2013 Handles CSS offline operations\ncgroup_release_wq \u2013 Manages resource release\ncgroup_free_wq \u2013 Performs final memory deallocation\n\nThis separation eliminates blocking in the CSS free path while waiting for\noffline operations to complete.\n\n[1] https://github.com/linux-test-project/ltp/blob/master/runtest/controllers",
"id": "GHSA-vgcj-37hg-gm6g",
"modified": "2025-10-04T09:30:21Z",
"published": "2025-10-04T09:30:21Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-39953"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/05e0b03447cf215ec384210441b34b7a3b16e8b0"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4a1e3ec28e8062cd9f339aa6a942df9c5bcb6811"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/79f919a89c9d06816dbdbbd168fa41d27411a7f9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/993049c9b1355c78918344a6403427d53f9ee700"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a0c896bda7077aa5005473e2c5b3c27173313b4c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/cabadd7fd15f97090f752fd22dd7f876a0dc3dc4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ded4d207a3209a834b6831ceec7f39b934c74802"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f2795d1b92506e3adf52a298f7181032a1525e04"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
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