FKIE_CVE-2026-98219

Vulnerability from fkie_nvd - Published: 2026-10-06 09:18 - Updated: 2026-10-06 09:18
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: sched_ext: Close the pre-enable ops error claim window scx_alloc_and_add_sched() publishes ops->priv before scx_root_enable_workfn() switches the state to SCX_ENABLING. An error claimed via scx_bpf_error_bstr() from an associated BPF program in that window is consumed by scx_disable_workfn(), which takes the pre-enable shortcut in scx_root_disable(). The shortcut returns without any teardown and restores SCX_DISABLED with an unconditional scx_set_enable_state() xchg racing the enable workfn's own transition. The enable then completes with the claim consumed: the scheduler stays up but can never be disabled again, and bpf_scx_unreg() frees it while still in use, resulting in a use-after-free. Both WARN_ON_ONCE()s fire back to back: WARNING: kernel/sched/ext/ext.c:7522 at scx_root_enable_workfn+0xeec/0x1be0, CPU#3: scx_enable_help/276 WARNING: kernel/sched/ext/ext.c:6398 at scx_root_disable+0xb50/0xdb8, CPU#0: sched_ext_helpe/664 scx_root_enable_workfn() switches to SCX_ENABLING before the scheduler allocation, so ops->priv is never visible while SCX_DISABLED. The allocation failure path restores SCX_DISABLED.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/959c66dc4a915be306c35691095c787c61dc7df9
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c7a1c6e8004ab12a9c9bfdcb603f60f9bf4a3cee
Impacted products
Vendor Product Version
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{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/sched/ext/ext.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "959c66dc4a915be306c35691095c787c61dc7df9",
              "status": "affected",
              "version": "105dcd005be2ac1d5541921db8feb1d0f98d59d5",
              "versionType": "git"
            },
            {
              "lessThan": "c7a1c6e8004ab12a9c9bfdcb603f60f9bf4a3cee",
              "status": "affected",
              "version": "105dcd005be2ac1d5541921db8feb1d0f98d59d5",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/sched/ext/ext.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.1"
            },
            {
              "lessThan": "7.1",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc4",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Close the pre-enable ops error claim window\n\nscx_alloc_and_add_sched() publishes ops-\u003epriv before\nscx_root_enable_workfn() switches the state to SCX_ENABLING. An error\nclaimed via scx_bpf_error_bstr() from an associated BPF program in that\nwindow is consumed by scx_disable_workfn(), which takes the pre-enable\nshortcut in scx_root_disable(). The shortcut returns without any teardown\nand restores SCX_DISABLED with an unconditional scx_set_enable_state() xchg\nracing the enable workfn\u0027s own transition. The enable then completes with\nthe claim consumed: the scheduler stays up but can never be disabled again,\nand bpf_scx_unreg() frees it while still in use, resulting in a\nuse-after-free. Both WARN_ON_ONCE()s fire back to back:\n\n  WARNING: kernel/sched/ext/ext.c:7522 at\n  scx_root_enable_workfn+0xeec/0x1be0, CPU#3: scx_enable_help/276\n\n  WARNING: kernel/sched/ext/ext.c:6398 at scx_root_disable+0xb50/0xdb8,\n  CPU#0: sched_ext_helpe/664\n\nscx_root_enable_workfn() switches to SCX_ENABLING before the scheduler\nallocation, so ops-\u003epriv is never visible while SCX_DISABLED. The allocation\nfailure path restores SCX_DISABLED."
    }
  ],
  "id": "CVE-2026-98219",
  "lastModified": "2026-10-06T09:18:08.730",
  "metrics": {},
  "published": "2026-10-06T09:18:08.730",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/959c66dc4a915be306c35691095c787c61dc7df9"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c7a1c6e8004ab12a9c9bfdcb603f60f9bf4a3cee"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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