144 lines
9.1 KiB
JSON
144 lines
9.1 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2026-98385",
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"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"state": "PUBLISHED",
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"assignerShortName": "Linux",
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"dateReserved": "2026-09-25T10:25:14.345Z",
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"datePublished": "2026-10-12T05:48:52.248Z",
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"dateUpdated": "2026-10-24T14:08:42.034Z"
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},
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"containers": {
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"cna": {
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"providerMetadata": {
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"shortName": "Linux",
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"dateUpdated": "2026-10-24T14:08:42.034Z"
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},
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"descriptions": [
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{
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"lang": "en",
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"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."
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}
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],
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"metrics": [
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{
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"cvssV3_1": {
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"version": "3.1",
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"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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"baseScore": 7.8,
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"baseSeverity": "HIGH"
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},
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"scenarios": [
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{
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"lang": "en",
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"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."
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}
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]
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}
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],
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"affected": [
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "unaffected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"include/linux/mm_types.h",
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"include/linux/sched.h",
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"kernel/exit.c",
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"kernel/sched/fair.c"
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],
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"versions": [
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{
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"version": "df0d98475954d655571979aa061ecb07d7e00392",
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"lessThan": "852ecb6bc0bc0106f44f74ba3944524732486025",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "df0d98475954d655571979aa061ecb07d7e00392",
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"lessThan": "28f9c0e0a0b94c5d3e1b634db545f6e1f94858c5",
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"status": "affected",
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"versionType": "git"
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}
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]
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},
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "affected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"include/linux/mm_types.h",
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"include/linux/sched.h",
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"kernel/exit.c",
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"kernel/sched/fair.c"
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],
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"versions": [
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{
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"version": "7.2",
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"status": "affected"
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},
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{
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"version": "0",
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"lessThan": "7.2",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.2.9",
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"lessThanOrEqual": "7.2.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.3",
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"lessThanOrEqual": "*",
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"status": "unaffected",
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"versionType": "original_commit_for_fix"
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}
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]
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}
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],
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"cpeApplicability": [
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{
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"nodes": [
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{
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"operator": "OR",
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"negate": false,
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"cpeMatch": [
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{
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "7.2",
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"versionEndExcluding": "7.2.9"
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},
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{
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "7.2",
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"versionEndExcluding": "7.3"
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}
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]
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}
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]
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}
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],
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"references": [
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{
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"url": "https://git.kernel.org/stable/c/852ecb6bc0bc0106f44f74ba3944524732486025"
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},
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{
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"url": "https://git.kernel.org/stable/c/28f9c0e0a0b94c5d3e1b634db545f6e1f94858c5"
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}
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],
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"title": "sched/cache: Decouple sched_cache_group from mm to fix UAF",
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"x_generator": {
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"engine": "bippy-1.2.0"
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}
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}
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}
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} |