CVE-2026-99104 (GCVE-0-2026-99104)

Vulnerability from cvelistv5 – Published: 2026-10-28 10:34 – Updated: 2026-10-28 10:34
VLAI
Title
sched_ext: Fix the bypass dispatch claim for schedulers bypassed by an ancestor
Summary
In the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix the bypass dispatch claim for schedulers bypassed by an ancestor scx_bypass() claims bypass dispatch when the scheduler's depth goes from zero to one and releases it when the depth returns to zero, but propagates only the depth to the descendants, not the claim. A descendant that starts bypassing with its ancestor never claims, and one whose own bypass ends under the ancestor's keeps its claim, as its depth does not return to zero. A sub-scheduler enable whose bypass ends under a PM suspend thus leaks its claim: the parent keeps hosting bypass dispatch and the sub-scheduler's next bypass trips the WARN_ON_ONCE() on the claim. A sub-scheduler disable that starts under a PM suspend has no claim, so once the resume lifts the root's bypass its tasks sit on the parent's bypass DSQs with nobody consuming them. Claim for every descendant whose depth goes from zero to one in the propagation and release every scheduler in the subtree whose depth returned to zero once the tasks have moved out of the bypass DSQs. A parent that is bypassing itself when a descendant claims consumes only its own bypass DSQs, empty until it leaves bypass and becomes the host.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 7033 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: aa2a0a19686c90106ade6a7e848ffbb62d55d733 , < f0f18075e45d47bef7ff2eb9512ee4f0c7e5f9c7 (git)
Affected: aa2a0a19686c90106ade6a7e848ffbb62d55d733 , < 5bdeca322a6f8d10acaf67cccab1f69747ee7be3 (git)
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Linux Linux Affected: 7.1
Unaffected: 0 , < 7.1 (semver)
Unaffected: 7.2.13 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
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{
  "containers": {
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          "programFiles": [
            "kernel/sched/ext/ext.c"
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Fix the bypass dispatch claim for schedulers bypassed by an ancestor\n\nscx_bypass() claims bypass dispatch when the scheduler\u0027s depth goes from\nzero to one and releases it when the depth returns to zero, but propagates\nonly the depth to the descendants, not the claim. A descendant that starts\nbypassing with its ancestor never claims, and one whose own bypass ends\nunder the ancestor\u0027s keeps its claim, as its depth does not return to zero.\n\nA sub-scheduler enable whose bypass ends under a PM suspend thus leaks its\nclaim: the parent keeps hosting bypass dispatch and the sub-scheduler\u0027s next\nbypass trips the WARN_ON_ONCE() on the claim. A sub-scheduler disable that\nstarts under a PM suspend has no claim, so once the resume lifts the root\u0027s\nbypass its tasks sit on the parent\u0027s bypass DSQs with nobody consuming them.\n\nClaim for every descendant whose depth goes from zero to one in the\npropagation and release every scheduler in the subtree whose depth returned\nto zero once the tasks have moved out of the bypass DSQs. A parent that is\nbypassing itself when a descendant claims consumes only its own bypass DSQs,\nempty until it leaves bypass and becomes the host."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-28T10:34:23.729Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/f0f18075e45d47bef7ff2eb9512ee4f0c7e5f9c7"
        },
        {
          "url": "https://git.kernel.org/stable/c/5bdeca322a6f8d10acaf67cccab1f69747ee7be3"
        }
      ],
      "title": "sched_ext: Fix the bypass dispatch claim for schedulers bypassed by an ancestor",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-99104",
    "datePublished": "2026-10-28T10:34:23.729Z",
    "dateReserved": "2026-09-25T10:25:14.391Z",
    "dateUpdated": "2026-10-28T10:34:23.729Z",
    "state": "PUBLISHED"
  },
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      "percentile": "0.06732"
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          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Fix the bypass dispatch claim for schedulers bypassed by an ancestor\n\nscx_bypass() claims bypass dispatch when the scheduler\u0027s depth goes from\nzero to one and releases it when the depth returns to zero, but propagates\nonly the depth to the descendants, not the claim. A descendant that starts\nbypassing with its ancestor never claims, and one whose own bypass ends\nunder the ancestor\u0027s keeps its claim, as its depth does not return to zero.\n\nA sub-scheduler enable whose bypass ends under a PM suspend thus leaks its\nclaim: the parent keeps hosting bypass dispatch and the sub-scheduler\u0027s next\nbypass trips the WARN_ON_ONCE() on the claim. A sub-scheduler disable that\nstarts under a PM suspend has no claim, so once the resume lifts the root\u0027s\nbypass its tasks sit on the parent\u0027s bypass DSQs with nobody consuming them.\n\nClaim for every descendant whose depth goes from zero to one in the\npropagation and release every scheduler in the subtree whose depth returned\nto zero once the tasks have moved out of the bypass DSQs. A parent that is\nbypassing itself when a descendant claims consumes only its own bypass DSQs,\nempty until it leaves bypass and becomes the host."
          }
        ],
        "id": "CVE-2026-99104",
        "lastModified": "2026-10-28T11:17:29.733",
        "metrics": {},
        "published": "2026-10-28T11:17:29.733",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/5bdeca322a6f8d10acaf67cccab1f69747ee7be3"
          },
          {
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          }
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-10-29T07:53:30+00:00",
      "cve": "CVE-2026-99104",
      "id": "CVE-2026-99104",
      "initial_release_date": "2026-10-28T00:00:00+00:00",
      "product_status:known_not_affected": "278",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: sched_ext: Fix the bypass dispatch claim for schedulers bypassed by an ancestor",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-99104.json",
      "version": "3"
    }
  }
}



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