{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-98385", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-25T10:25:14.345Z", "datePublished": "2026-10-12T05:48:52.248Z", "dateUpdated": "2026-10-24T14:08:42.034Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-24T14:08:42.034Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched/cache: Decouple sched_cache_group from mm to fix UAF\n\nCurrently the sched cache grouping is by mm and the scheduling statistics\nsched_cache_stat lives in the mm structure. This ties the life cycle\nof scheduling stats with mm.\n\nIn account_mm_sched(), the scheduling stats are accessed by\ntask->mm->sc_stat. However, a task may be switching mm on one CPU when\nanother CPU is running account_mm_sched(), and possibly accessing the\nold mm that was freed. This problem was found when running tests with\nKASAN by Hyunwoo:\n\n https://lore.kernel.org/lkml/apPb-Dr4nPYuHQOK@v4bel/\n\nInstead of serializing the mm access by introducing extra acquisition of\nrq lock in the mm free path, extract sched_cache_stat from mm_struct,\nrename it as sched_cache_group and manage its life cycle apart from\nmm_struct with its own ref counting. This allows us in the next patch\naccess sched_cache_group directly from task, and add a refcount\non sched_cache_group when a task links to it. This prevents the use\nafter free issue when accessing stale and released old mm and its\nsched cache stat a task switches to a new mm while account_mm_sched()\nis done elsewhere.\n\nThe other benefit of this restructure is in the future, the grouping of\ntasks to a LLC would have the flexibility to be associated with a user\ndefined grouping, or cgroup, cookie group, numa_group or others instead\nof just with a single mm address space.\n\nRename sched_cache_stat to sched_cache_group and turn it into a refcounted\nobject allocated from mm_struct. The mm_struct now holds a pointer\n(sched_cache_grp) to this object instead of embedding it." } ], "metrics": [ { "cvssV3_1": { "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" }, "scenarios": [ { "lang": "en", "value": "AV:L - An unprivileged local write(2) to an attacker-created pipe reaches anon_pipe_write()->try_to_wake_up()->ttwu_queue()->enqueue_task_fair()->update_curr()->update_se()->account_mm_sched(), while the attacker's execveat(2) frees rq->curr's old mm. No protocol supplies the trigger.\nAC:L - On a qualifying multi-LLC SMP host, CONFIG_SCHED_CACHE and sysctl_sched_cache_user both default enabled. The attacker controls both race sides by repeatedly waking or updating its queued task and execveat()ing its pinned trampoline, and can groom the freed per-CPU slot.\nPR:L - user_check_sched_setscheduler() permits the same-owner SCHED_IDLE/lower-priority sched_setattr() used to force update_curr() without CAP_SYS_NICE; pipe creation, permitted CPU affinity, and execveat() of the attacker's memfd also require no capability.\nUI:N - The attacker creates the pipe and tasks, drives sched_setattr() or write(), and calls execveat() to replace and release its own mm; no other user must mount, open, or approve anything.\nS:U - account_mm_sched() and mm_destroy_sched() are host-kernel scheduler/mm code, and the demonstrated result is UID-0 execution under that same kernel authority, not a guest-to-host or IOMMU boundary crossing.\nC:H - After mm_destroy_sched() frees sc_stat.pcpu_sched, __update_mm_sched() accesses its reclaimed epoch and runtime. The demonstrated reclaim corrupts a futex reference and reaches UID 0 through pipe/page-cache manipulation, enabling unrestricted data reads.\nI:H - The stale pcpu_sched->epoch write changes a reclaimed futex per-CPU reference from 1 to 0; the demonstrated follow-on UAF decrements pipe_buffer.flags, enables page-cache overwrite of /usr/bin/newgrp, and executes as UID 0.\nA:H - __update_mm_sched() and pcpu_sched->runtime += delta_exec access freed per-CPU storage; if reclamation is not steered, these writes can corrupt reused kernel objects and cause an oops or panic." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/linux/mm_types.h", "include/linux/sched.h", "kernel/exit.c", "kernel/sched/fair.c" ], "versions": [ { "version": "df0d98475954d655571979aa061ecb07d7e00392", "lessThan": "852ecb6bc0bc0106f44f74ba3944524732486025", "status": "affected", "versionType": "git" }, { "version": "df0d98475954d655571979aa061ecb07d7e00392", "lessThan": "28f9c0e0a0b94c5d3e1b634db545f6e1f94858c5", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/linux/mm_types.h", "include/linux/sched.h", "kernel/exit.c", "kernel/sched/fair.c" ], "versions": [ { "version": "7.2", "status": "affected" }, { "version": "0", "lessThan": "7.2", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.9", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.2", "versionEndExcluding": "7.2.9" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.2", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/852ecb6bc0bc0106f44f74ba3944524732486025" }, { "url": "https://git.kernel.org/stable/c/28f9c0e0a0b94c5d3e1b634db545f6e1f94858c5" } ], "title": "sched/cache: Decouple sched_cache_group from mm to fix UAF", "x_generator": { "engine": "bippy-1.2.0" } } } }