{"attribution":"This product uses data from the NVD API but is not endorsed or certified by the NVD.","cve":{"id":"CVE-2026-98163","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","published":"2026-09-26T09:16:38.303","lastModified":"2026-10-19T10:18:16.653","vulnStatus":"Modified","cveTags":[],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ncgroup: Avoid iteration of dying tasks with zero refcount\n\nThe commit 260fbcb92bbea (\"cgroup: Move dying_tasks cleanup from\ncgroup_task_release() to cgroup_task_free()\") extended the lifetime of\ntasks on the dying_tasks list.\nThe iterators have provision to go through dying_tasks because of\ndying threadgroup leaders or explicit CSS_TASK_ITER_WITH_DEAD, however,\nit was expected that such tasks can obtain a new reference (that is\npossible before cgroup_task_release()/put_task_struct_rcu_user()).\nThe tasks after cgroup_task_release() and before cgroup_task_free()\nare subject to race when they may or may not have -\u003eusage count \u003e 0.\n\nThe race window is between css_task_iter_next() invocations\nwhen css_set_lock is released and we may arrive at a new -\u003etask_pos.\nThe iterator should not attempt to resurrect tasks whose -\u003eusage count\ndropped to zero. (When that happens, __put_task_struct_rcu_cb() is\nalready imminent and the returned task_struct would could be used\nafter free.)\n\nAs for the fix, we cannot simply check the signal-\u003elive count of a task\non the dying list because that won't distinguish regular zombies waiting\nto be reaped from RCU remnant tasks that are going to be free'd.\nTherefore add an extra check to rule out -\u003eusage==0 tasks from any\niteration.\n\nThe repeat: loop in css_task_iter_advance() doesn't consider -\u003eusage\ncount, so add a new loop to css_task_iter_next() to skip de-used tasks\non the dying_list.\n\nRough illustration of the possible race\n\n  R (reader of cgroup.procs)         T (thread)                       L (group leader)\n  ---------------------------------  -------------------------------- --------------------------------\n                                                                      L exits, signal-\u003elive \u003e 0\n                                                                      cgroup_task_dead(L)\n                                                                        css_set_skip_task_iters() // skips only cset-\u003etasks\n                                                                        list_add_tail(\u0026L-\u003ecg_list, \u0026cset-\u003edying_tasks)\n  css_task_iter_next()\n    take css_set_lock\n    css_task_iter_advance()\n      leader \u0026\u0026 signal-\u003elive != 0\n      =\u003e it-\u003etask_pos = \u0026L-\u003ecg_list\n    release css_set_lock\n                                     T exits\n                                     --signal-\u003elive == 0\n\t\t\t\t     cgroup_task_dead(T) // css_set_lock\n                                     release_task(T)\n                                       cgroup_task_release(T)\n                                       release_task(L) // zap_leader\n                                         cgroup_task_release(L)\n                                         put_task_struct_rcu_user(L)\n                                         ...RCU...\n                                         put_task_struct(L)\n                                           L-\u003eusage = 0\n                                           /* L still on dying_tasks */\n                                           ...RCU...\n                                           __put_task_struct(L)\n  css_task_iter_next() // another iteration\n    take css_set_lock\n    it-\u003etask_pos = \u0026L-\u003ecg_list\n    get_task_struct(L)\n      =\u003e addition on 0\n    drop css_set_lock\n                                           cgroup_task_free(L)\n                                             css_set_skip_task_iters() // dying skip comes too late\n                                           free_task(L)\n  cgroup_procs_show()\n    task_pid_vnr(L)"}],"affected":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","affectedData":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","programFiles":["kernel/cgroup/cgroup.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","versions":[{"version":"260fbcb92bbeacfcd050410fdc2d24ab15044400","lessThan":"828938118d6c2bb711301748c3e39e4bed6a62f5","versionType":"git","status":"affected"},{"version":"260fbcb92bbeacfcd050410fdc2d24ab15044400","lessThan":"057dac23d329d5c5ed62352f2659a39fd46c6d4a","versionType":"git","status":"affected"}]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","programFiles":["kernel/cgroup/cgroup.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","versions":[{"version":"6.19","status":"affected"},{"version":"0","lessThan":"6.19","versionType":"semver","status":"unaffected"},{"version":"7.2.8","lessThanOrEqual":"7.2.*","versionType":"semver","status":"unaffected"},{"version":"7.3","lessThanOrEqual":"*","versionType":"original_commit_for_fix","status":"unaffected"}]}]}],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":1.8,"impactScore":5.9},{"source":"nvd@nist.gov","type":"Primary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.0,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"HIGH","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":1.0,"impactScore":5.9}]},"weaknesses":[{"source":"nvd@nist.gov","type":"Primary","description":[{"lang":"en","value":"CWE-362"},{"lang":"en","value":"CWE-416"}]}],"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.19","versionEndExcluding":"7.2.8","matchCriteriaId":"03F96438-F355-42FE-99A2-E7C298C7580F"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:7.3:rc1:*:*:*:*:*:*","matchCriteriaId":"11E35E1B-5DB4-4AB9-9706-CD73B799EADF"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:7.3:rc2:*:*:*:*:*:*","matchCriteriaId":"14FD7B9A-4946-4511-8E63-6E13870CD4A8"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:7.3:rc3:*:*:*:*:*:*","matchCriteriaId":"F06EDE17-AD0F-4C81-AF8C-D86B6AF0F622"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/057dac23d329d5c5ed62352f2659a39fd46c6d4a","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/828938118d6c2bb711301748c3e39e4bed6a62f5","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"]}]}}