{"id":"CVE-2025-39953","title":"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 contr…","summary":"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 contr…","severity":"medium","cvss":5.5,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","vendor":"linux","product":"linux_kernel","affected":["linux_kernel >= 4.6, < 5.4.300","linux_kernel >= 5.5, < 5.10.245","linux_kernel >= 5.11, < 5.15.194","linux_kernel >= 5.16, < 6.1.154","linux_kernel >= 6.2, < 6.6.108","linux_kernel >= 6.7, < 6.12.49","linux_kernel >= 6.13, < 6.16.9","linux_kernel = 6.17"],"patched":["linux_kernel 6.16.9"],"published":"2025-10-04","updated":"2026-10-15","sourceUpdated":"2026-10-15T02:18:03.110","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2025-39953","references":[{"url":"https://git.kernel.org/stable/c/05e0b03447cf215ec384210441b34b7a3b16e8b0","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/4a1e3ec28e8062cd9f339aa6a942df9c5bcb6811","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/79f919a89c9d06816dbdbbd168fa41d27411a7f9","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/993049c9b1355c78918344a6403427d53f9ee700","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a0c896bda7077aa5005473e2c5b3c27173313b4c","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/cabadd7fd15f97090f752fd22dd7f876a0dc3dc4","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ded4d207a3209a834b6831ceec7f39b934c74802","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/f2795d1b92506e3adf52a298f7181032a1525e04","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-019113.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-457936.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}],"tags":["nvd","cve.org"],"epss":0.00157,"epssPercentile":0.04849,"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-06-10T20:41:56.498338Z"},"ingestedAt":"2026-09-08T15:33:26.996Z","slug":"CVE-2025-39953","body":"## Overview\n\nIn 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 – Handles CSS offline operations\ncgroup_release_wq – Manages resource release\ncgroup_free_wq – 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\n\n## Affected\n\n- `linux_kernel >= 4.6, < 5.4.300`\n- `linux_kernel >= 5.5, < 5.10.245`\n- `linux_kernel >= 5.11, < 5.15.194`\n- `linux_kernel >= 5.16, < 6.1.154`\n- `linux_kernel >= 6.2, < 6.6.108`\n- `linux_kernel >= 6.7, < 6.12.49`\n- `linux_kernel >= 6.13, < 6.16.9`\n- `linux_kernel = 6.17`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 6.16.9`","depth":"sunlit","depthScore":30,"depthScoreParts":{"impact":30.3,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":221563,"id":"CVE-2025-39953","ts":1792035262785,"field":"cvss","old":null,"new":"5.5"},{"seq":221562,"id":"CVE-2025-39953","ts":1792035262785,"field":"severity","old":"none","new":"medium"}]}