CVE-2025-21771 (GCVE-0-2025-21771)

Vulnerability from cvelistv5 – Published: 2025-02-27 02:18 – Updated: 2026-05-11 21:06
VLAI
Title
sched_ext: Fix incorrect autogroup migration detection
Summary
In the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix incorrect autogroup migration detection scx_move_task() is called from sched_move_task() and tells the BPF scheduler that cgroup migration is being committed. sched_move_task() is used by both cgroup and autogroup migrations and scx_move_task() tried to filter out autogroup migrations by testing the destination cgroup and PF_EXITING but this is not enough. In fact, without explicitly tagging the thread which is doing the cgroup migration, there is no good way to tell apart scx_move_task() invocations for racing migration to the root cgroup and an autogroup migration. This led to scx_move_task() incorrectly ignoring a migration from non-root cgroup to an autogroup of the root cgroup triggering the following warning: WARNING: CPU: 7 PID: 1 at kernel/sched/ext.c:3725 scx_cgroup_can_attach+0x196/0x340 ... Call Trace: <TASK> cgroup_migrate_execute+0x5b1/0x700 cgroup_attach_task+0x296/0x400 __cgroup_procs_write+0x128/0x140 cgroup_procs_write+0x17/0x30 kernfs_fop_write_iter+0x141/0x1f0 vfs_write+0x31d/0x4a0 __x64_sys_write+0x72/0xf0 do_syscall_64+0x82/0x160 entry_SYSCALL_64_after_hwframe+0x76/0x7e Fix it by adding an argument to sched_move_task() that indicates whether the moving is for a cgroup or autogroup migration. After the change, scx_move_task() is called only for cgroup migrations and renamed to scx_cgroup_move_task().
Severity
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 8195136669661fdfe54e9a8923c33b31c92fc1da , < 75bf2f80c046d2ec5a07455891ea0a9fb6d8b5f6 (git)
Affected: 8195136669661fdfe54e9a8923c33b31c92fc1da , < d8b510d0ddc65d8a71e0f9a3acc9ed5f010fc514 (git)
Affected: 8195136669661fdfe54e9a8923c33b31c92fc1da , < d6f3e7d564b2309e1f17e709a70eca78d7ca2bb8 (git)
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Linux Linux Affected: 6.12
Unaffected: 0 , < 6.12 (semver)
Unaffected: 6.12.16 , ≤ 6.12.* (semver)
Unaffected: 6.13.4 , ≤ 6.13.* (semver)
Unaffected: 6.14 , ≤ * (original_commit_for_fix)
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Fix incorrect autogroup migration detection\n\nscx_move_task() is called from sched_move_task() and tells the BPF scheduler\nthat cgroup migration is being committed. sched_move_task() is used by both\ncgroup and autogroup migrations and scx_move_task() tried to filter out\nautogroup migrations by testing the destination cgroup and PF_EXITING but\nthis is not enough. In fact, without explicitly tagging the thread which is\ndoing the cgroup migration, there is no good way to tell apart\nscx_move_task() invocations for racing migration to the root cgroup and an\nautogroup migration.\n\nThis led to scx_move_task() incorrectly ignoring a migration from non-root\ncgroup to an autogroup of the root cgroup triggering the following warning:\n\n  WARNING: CPU: 7 PID: 1 at kernel/sched/ext.c:3725 scx_cgroup_can_attach+0x196/0x340\n  ...\n  Call Trace:\n  \u003cTASK\u003e\n    cgroup_migrate_execute+0x5b1/0x700\n    cgroup_attach_task+0x296/0x400\n    __cgroup_procs_write+0x128/0x140\n    cgroup_procs_write+0x17/0x30\n    kernfs_fop_write_iter+0x141/0x1f0\n    vfs_write+0x31d/0x4a0\n    __x64_sys_write+0x72/0xf0\n    do_syscall_64+0x82/0x160\n    entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nFix it by adding an argument to sched_move_task() that indicates whether the\nmoving is for a cgroup or autogroup migration. After the change,\nscx_move_task() is called only for cgroup migrations and renamed to\nscx_cgroup_move_task()."
          },
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            "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: sched_ext: Se corrige la detecci\u00f3n incorrecta de la migraci\u00f3n de autogrupos. scx_move_task() se llama desde sched_move_task() y le dice al programador BPF que se est\u00e1 confirmando la migraci\u00f3n de cgroup. sched_move_task() se usa tanto en las migraciones de cgroup como de autogrupos y scx_move_task() intent\u00f3 filtrar las migraciones de autogrupos probando el cgroup de destino y PF_EXITING, pero esto no es suficiente. De hecho, sin etiquetar expl\u00edcitamente el hilo que est\u00e1 realizando la migraci\u00f3n de cgroup, no hay una buena manera de diferenciar las invocaciones de scx_move_task() para la migraci\u00f3n de ejecuci\u00f3n al cgroup ra\u00edz y una migraci\u00f3n de autogrupo. Esto provoc\u00f3 que scx_move_task() ignorara incorrectamente una migraci\u00f3n desde un cgroup no ra\u00edz a un autogrupo del cgroup ra\u00edz, lo que activaba la siguiente advertencia: ADVERTENCIA: CPU: 7 PID: 1 en kernel/sched/ext.c:3725 scx_cgroup_can_attach+0x196/0x340 ... Seguimiento de llamadas:  cgroup_migrate_execute+0x5b1/0x700 cgroup_attach_task+0x296/0x400 __cgroup_procs_write+0x128/0x140 cgroup_procs_write+0x17/0x30 kernfs_fop_write_iter+0x141/0x1f0 vfs_write+0x31d/0x4a0 __x64_sys_write+0x72/0xf0 do_syscall_64+0x82/0x160 entry_SYSCALL_64_after_hwframe+0x76/0x7e Solucione el problema agregando un argumento a sched_move_task() que indique si el movimiento es para una migraci\u00f3n de cgroup o de autogroup. Despu\u00e9s del cambio, se llama a scx_move_task() solo para migraciones de cgroup y se le cambia el nombre a scx_cgroup_move_task()."
          }
        ],
        "id": "CVE-2025-21771",
        "lastModified": "2026-06-17T08:44:14.410",
        "metrics": {
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                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 5.5,
                "baseSeverity": "MEDIUM",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
                "version": "3.1"
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              "source": "nvd@nist.gov",
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Analyzed",
        "weaknesses": [
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            "description": [
              {
                "lang": "en",
                "value": "NVD-CWE-noinfo"
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            "source": "nvd@nist.gov",
            "type": "Primary"
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    "redhat_vex": {
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      "current_release_date": "2026-06-29T23:59:25+00:00",
      "cve": "CVE-2025-21771",
      "id": "CVE-2025-21771",
      "initial_release_date": "2025-02-27T00:00:00+00:00",
      "product_status:fixed": "309",
      "product_status:known_affected": "28",
      "product_status:known_not_affected": "170",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: sched_ext: Fix incorrect autogroup migration detection",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-21771.json",
      "version": "3"
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}



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