GHSA-984H-V76F-94JC
Vulnerability from github – Published: 2026-10-12 06:31 – Updated: 2026-10-12 06:31In the Linux kernel, the following vulnerability has been resolved:
sched/cache: Decouple sched_cache_group from mm to fix UAF
Currently the sched cache grouping is by mm and the scheduling statistics sched_cache_stat lives in the mm structure. This ties the life cycle of scheduling stats with mm.
In account_mm_sched(), the scheduling stats are accessed by task->mm->sc_stat. However, a task may be switching mm on one CPU when another CPU is running account_mm_sched(), and possibly accessing the old mm that was freed. This problem was found when running tests with KASAN by Hyunwoo:
https://lore.kernel.org/lkml/apPb-Dr4nPYuHQOK@v4bel/
Instead of serializing the mm access by introducing extra acquisition of rq lock in the mm free path, extract sched_cache_stat from mm_struct, rename it as sched_cache_group and manage its life cycle apart from mm_struct with its own ref counting. This allows us in the next patch access sched_cache_group directly from task, and add a refcount on sched_cache_group when a task links to it. This prevents the use after free issue when accessing stale and released old mm and its sched cache stat a task switches to a new mm while account_mm_sched() is done elsewhere.
The other benefit of this restructure is in the future, the grouping of tasks to a LLC would have the flexibility to be associated with a user defined grouping, or cgroup, cookie group, numa_group or others instead of just with a single mm address space.
Rename sched_cache_stat to sched_cache_group and turn it into a refcounted object allocated from mm_struct. The mm_struct now holds a pointer (sched_cache_grp) to this object instead of embedding it.
{
"affected": [],
"aliases": [
"CVE-2026-98385"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-10-12T06:17:00Z",
"severity": null
},
"details": "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-\u003emm-\u003esc_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.",
"id": "GHSA-984h-v76f-94jc",
"modified": "2026-10-12T06:31:17Z",
"published": "2026-10-12T06:31:17Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98385"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/28f9c0e0a0b94c5d3e1b634db545f6e1f94858c5"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/852ecb6bc0bc0106f44f74ba3944524732486025"
}
],
"schema_version": "1.4.0",
"severity": []
}
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