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GHSA-3R69-998R-Q4C2

Vulnerability from github – Published: 2026-10-18 18:32 – Updated: 2026-10-18 18:32

Details

In the Linux kernel, the following vulnerability has been resolved:

sched/cache: Introduce task_struct->sched_cache_grp to fix UAF

Add a sched_cache_grp pointer to task_struct so that scheduler code can access the cache group directly via the task, without going through mm->sched_cache_grp. This decouples the scheduler's hot-path accesses from the mm_struct.

Each task holds its own refcount on the sched_cache_group, separate from the reference held by its mm_struct. The reference is acquired in copy_mm() (fork) and exec_mmap() (exec), and released in exit_mm(). This fixes the use-after-free when account_mm_sched() reaches the group through a task whose mm is being switched, as reported by Hyunwoo:

https://lore.kernel.org/lkml/apPb-Dr4nPYuHQOK@v4bel/

Convert all scheduler code in fair.c and exit.c to use p->sched_cache_grp instead of p->mm->sched_cache_grp.

Keep the fork/exec/exit reference management out of the generic mm paths: add sched_cache_fork(), sched_cache_fork_cleanup(), sched_cache_exec_mmap() and sched_cache_exit_mm() in kernel/sched/cache_sched.c (with empty stubs for !CONFIG_SCHED_CACHE), so fs/exec.c, kernel/fork.c and kernel/exit.c each call one helper instead of open-coding the refcounting under #ifdef. Also add sched_cache_group_get() and task_cache_group_get().

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{
  "affected": [],
  "aliases": [
    "CVE-2026-98866"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-18T16:17:41Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched/cache: Introduce task_struct-\u003esched_cache_grp to fix UAF\n\nAdd a sched_cache_grp pointer to task_struct so that scheduler code\ncan access the cache group directly via the task, without going\nthrough mm-\u003esched_cache_grp.  This decouples the scheduler\u0027s hot-path\naccesses from the mm_struct.\n\nEach task holds its own refcount on the sched_cache_group, separate\nfrom the reference held by its mm_struct.  The reference is acquired\nin copy_mm() (fork) and exec_mmap() (exec), and released in exit_mm().\nThis fixes the use-after-free when account_mm_sched() reaches the group\nthrough a task whose mm is being switched, as reported by Hyunwoo:\n\n  https://lore.kernel.org/lkml/apPb-Dr4nPYuHQOK@v4bel/\n\nConvert all scheduler code in fair.c and exit.c to use\np-\u003esched_cache_grp instead of p-\u003emm-\u003esched_cache_grp.\n\nKeep the fork/exec/exit reference management out of the generic mm\npaths: add sched_cache_fork(), sched_cache_fork_cleanup(),\nsched_cache_exec_mmap() and sched_cache_exit_mm() in\nkernel/sched/cache_sched.c (with empty stubs for !CONFIG_SCHED_CACHE),\nso fs/exec.c, kernel/fork.c and kernel/exit.c each call one helper\ninstead of open-coding the refcounting under #ifdef.  Also add\nsched_cache_group_get() and task_cache_group_get().",
  "id": "GHSA-3r69-998r-q4c2",
  "modified": "2026-10-18T18:32:06Z",
  "published": "2026-10-18T18:32:06Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98866"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9436130e6da72af63289a4acb3aa0c1df07a3928"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b636fef85bda7d1bab9c0a45067ab1508d79d946"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-98866 (GCVE-0-2026-98866)

Vulnerability from cvelistv5 – Published: 2026-10-18 15:51 – Updated: 2026-10-18 15:51

Title

sched/cache: Introduce task_struct->sched_cache_grp to fix UAF

Summary

In the Linux kernel, the following vulnerability has been resolved: sched/cache: Introduce task_struct->sched_cache_grp to fix UAF Add a sched_cache_grp pointer to task_struct so that scheduler code can access the cache group directly via the task, without going through mm->sched_cache_grp. This decouples the scheduler's hot-path accesses from the mm_struct. Each task holds its own refcount on the sched_cache_group, separate from the reference held by its mm_struct. The reference is acquired in copy_mm() (fork) and exec_mmap() (exec), and released in exit_mm(). This fixes the use-after-free when account_mm_sched() reaches the group through a task whose mm is being switched, as reported by Hyunwoo: https://lore.kernel.org/lkml/apPb-Dr4nPYuHQOK@v4bel/ Convert all scheduler code in fair.c and exit.c to use p->sched_cache_grp instead of p->mm->sched_cache_grp. Keep the fork/exec/exit reference management out of the generic mm paths: add sched_cache_fork(), sched_cache_fork_cleanup(), sched_cache_exec_mmap() and sched_cache_exit_mm() in kernel/sched/cache_sched.c (with empty stubs for !CONFIG_SCHED_CACHE), so fs/exec.c, kernel/fork.c and kernel/exit.c each call one helper instead of open-coding the refcounting under #ifdef. Also add sched_cache_group_get() and task_cache_group_get().

Severity

No CVSS data available.

Assigner

Linux CNA under the mitre root

CNA scorecard D 53/100 over 7100 records in the last 180 days details

References

2 references

URL	Tags
https://git.kernel.org/stable/c/9436130e6da72af63…
https://git.kernel.org/stable/c/b636fef85bda7d1ba…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: df0d98475954d655571979aa061ecb07d7e00392 , < 9436130e6da72af63289a4acb3aa0c1df07a3928 (git) Affected: df0d98475954d655571979aa061ecb07d7e00392 , < b636fef85bda7d1bab9c0a45067ab1508d79d946 (git)
Linux	Linux	Affected: 7.2 Unaffected: 0 , < 7.2 (semver) Unaffected: 7.2.10 , ≤ 7.2.* (semver) Unaffected: 7.3-rc5 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/exec.c",
            "include/linux/sched.h",
            "kernel/exit.c",
            "kernel/fork.c",
            "kernel/sched/fair.c"
          ],
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          "vendor": "Linux",
          "versions": [
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          "versions": [
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              "version": "7.2"
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            },
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    "datePublished": "2026-10-18T15:51:27.883Z",
    "dateReserved": "2026-09-25T10:25:14.377Z",
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}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
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Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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