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GHSA-RH9V-MPGH-F53X

Vulnerability from github – Published: 2026-10-23 15:31 – Updated: 2026-10-23 15:31

Details

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

sched_ext: Build the cid tables privately and publish them with RCU

The cid tables are visible to the cid kfuncs while being modified: the first enable publishes the global pointers before filling them, ops.init_cids() overrides rewrite them in place, and re-enables rebuild them in place. A racing TRACING or SYSCALL program can read unfilled entries, including uninitialized memory in the kmalloc'd tables, or torn topo updates.

Tie the tables' lifetimes to the root sched instead: each root enable builds a fresh set privately and publishes the per-table __rcu globals once the layout is final, and root disable unpublishes and RCU-frees the set. A non-NULL global is now always a fully built table which stays valid for the reader's RCU read section, and lookups stay two loads. Kfuncs treat NULL as no-mapping, also after the scheduler exits instead of reporting the stale last mapping.

The cid kfuncs are available whether the root scheduler is cid-form or cpu-form, the latter to allow gradual migration to cids. Every root therefore builds and publishes a default mapping.

Every reader must either be gated on scheduler liveness or NULL-check inside an RCU read section. Fix the two kfuncs that were neither: scx_bpf_this_cid() read the table with no RCU or preemption protection and scx_bpf_task_cid() relied on KF_RCU, which doesn't put a sleepable program in an RCU read section. The hotplug callbacks are instead serialized by retiring the tables inside the cpus_read_lock() section that clears scx_root.

v2: Document why every root builds the tables (desc + cid.c comment).

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{
  "affected": [],
  "aliases": [
    "CVE-2026-98942"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-23T13:17:15Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Build the cid tables privately and publish them with RCU\n\nThe cid tables are visible to the cid kfuncs while being modified: the\nfirst enable publishes the global pointers before filling them,\nops.init_cids() overrides rewrite them in place, and re-enables rebuild\nthem in place. A racing TRACING or SYSCALL program can read unfilled\nentries, including uninitialized memory in the kmalloc\u0027d tables, or torn\ntopo updates.\n\nTie the tables\u0027 lifetimes to the root sched instead: each root enable\nbuilds a fresh set privately and publishes the per-table __rcu globals once\nthe layout is final, and root disable unpublishes and RCU-frees the set. A\nnon-NULL global is now always a fully built table which stays valid for the\nreader\u0027s RCU read section, and lookups stay two loads. Kfuncs treat NULL as\nno-mapping, also after the scheduler exits instead of reporting the stale\nlast mapping.\n\nThe cid kfuncs are available whether the root scheduler is cid-form or\ncpu-form, the latter to allow gradual migration to cids. Every root\ntherefore builds and publishes a default mapping.\n\nEvery reader must either be gated on scheduler liveness or NULL-check\ninside an RCU read section. Fix the two kfuncs that were neither:\nscx_bpf_this_cid() read the table with no RCU or preemption protection and\nscx_bpf_task_cid() relied on KF_RCU, which doesn\u0027t put a sleepable program\nin an RCU read section. The hotplug callbacks are instead serialized by\nretiring the tables inside the cpus_read_lock() section that clears\nscx_root.\n\nv2: Document why every root builds the tables (desc + cid.c comment).",
  "id": "GHSA-rh9v-mpgh-f53x",
  "modified": "2026-10-23T15:31:32Z",
  "published": "2026-10-23T15:31:31Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98942"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0e1a74369bdbc357d3d9713734418d914a981553"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3a773220d39ba993dfe5d135f8b610be10794d5d"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-98942 (GCVE-0-2026-98942)

Vulnerability from cvelistv5 – Published: 2026-10-23 12:12 – Updated: 2026-10-26 06:56

Title

sched_ext: Build the cid tables privately and publish them with RCU

Summary

In the Linux kernel, the following vulnerability has been resolved: sched_ext: Build the cid tables privately and publish them with RCU The cid tables are visible to the cid kfuncs while being modified: the first enable publishes the global pointers before filling them, ops.init_cids() overrides rewrite them in place, and re-enables rebuild them in place. A racing TRACING or SYSCALL program can read unfilled entries, including uninitialized memory in the kmalloc'd tables, or torn topo updates. Tie the tables' lifetimes to the root sched instead: each root enable builds a fresh set privately and publishes the per-table __rcu globals once the layout is final, and root disable unpublishes and RCU-frees the set. A non-NULL global is now always a fully built table which stays valid for the reader's RCU read section, and lookups stay two loads. Kfuncs treat NULL as no-mapping, also after the scheduler exits instead of reporting the stale last mapping. The cid kfuncs are available whether the root scheduler is cid-form or cpu-form, the latter to allow gradual migration to cids. Every root therefore builds and publishes a default mapping. Every reader must either be gated on scheduler liveness or NULL-check inside an RCU read section. Fix the two kfuncs that were neither: scx_bpf_this_cid() read the table with no RCU or preemption protection and scx_bpf_task_cid() relied on KF_RCU, which doesn't put a sleepable program in an RCU read section. The hotplug callbacks are instead serialized by retiring the tables inside the cpus_read_lock() section that clears scx_root. v2: Document why every root builds the tables (desc + cid.c comment).

Severity

No CVSS data available.

Assigner

Linux CNA under the mitre root

CNA scorecard D 53/100 over 7067 records in the last 180 days details

References

2 references

URL	Tags
https://git.kernel.org/stable/c/0e1a74369bdbc357d…
https://git.kernel.org/stable/c/3a773220d39ba993d…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: e9b55af47edf6e60c9a47b5604c3e15c5162ec86 , < 0e1a74369bdbc357d3d9713734418d914a981553 (git) Affected: e9b55af47edf6e60c9a47b5604c3e15c5162ec86 , < 3a773220d39ba993dfe5d135f8b610be10794d5d (git)
Linux	Linux	Affected: 7.2 Unaffected: 0 , < 7.2 (semver) Unaffected: 7.2.10 , ≤ 7.2.* (semver) Unaffected: 7.3 , ≤ * (original_commit_for_fix)

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JSON

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/sched/ext/cid.c",
            "kernel/sched/ext/cid.h",
            "kernel/sched/ext/ext.c",
            "kernel/sched/ext/internal.h",
            "kernel/sched/ext/sub.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "0e1a74369bdbc357d3d9713734418d914a981553",
              "status": "affected",
              "version": "e9b55af47edf6e60c9a47b5604c3e15c5162ec86",
              "versionType": "git"
            },
            {
              "lessThan": "3a773220d39ba993dfe5d135f8b610be10794d5d",
              "status": "affected",
              "version": "e9b55af47edf6e60c9a47b5604c3e15c5162ec86",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/sched/ext/cid.c",
            "kernel/sched/ext/cid.h",
            "kernel/sched/ext/ext.c",
            "kernel/sched/ext/internal.h",
            "kernel/sched/ext/sub.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.2"
            },
            {
              "lessThan": "7.2",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.10",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.10",
                  "versionStartIncluding": "7.2",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "7.2",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Build the cid tables privately and publish them with RCU\n\nThe cid tables are visible to the cid kfuncs while being modified: the\nfirst enable publishes the global pointers before filling them,\nops.init_cids() overrides rewrite them in place, and re-enables rebuild\nthem in place. A racing TRACING or SYSCALL program can read unfilled\nentries, including uninitialized memory in the kmalloc\u0027d tables, or torn\ntopo updates.\n\nTie the tables\u0027 lifetimes to the root sched instead: each root enable\nbuilds a fresh set privately and publishes the per-table __rcu globals once\nthe layout is final, and root disable unpublishes and RCU-frees the set. A\nnon-NULL global is now always a fully built table which stays valid for the\nreader\u0027s RCU read section, and lookups stay two loads. Kfuncs treat NULL as\nno-mapping, also after the scheduler exits instead of reporting the stale\nlast mapping.\n\nThe cid kfuncs are available whether the root scheduler is cid-form or\ncpu-form, the latter to allow gradual migration to cids. Every root\ntherefore builds and publishes a default mapping.\n\nEvery reader must either be gated on scheduler liveness or NULL-check\ninside an RCU read section. Fix the two kfuncs that were neither:\nscx_bpf_this_cid() read the table with no RCU or preemption protection and\nscx_bpf_task_cid() relied on KF_RCU, which doesn\u0027t put a sleepable program\nin an RCU read section. The hotplug callbacks are instead serialized by\nretiring the tables inside the cpus_read_lock() section that clears\nscx_root.\n\nv2: Document why every root builds the tables (desc + cid.c comment)."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-26T06:56:52.637Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/0e1a74369bdbc357d3d9713734418d914a981553"
        },
        {
          "url": "https://git.kernel.org/stable/c/3a773220d39ba993dfe5d135f8b610be10794d5d"
        }
      ],
      "title": "sched_ext: Build the cid tables privately and publish them with RCU",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98942",
    "datePublished": "2026-10-23T12:12:14.180Z",
    "dateReserved": "2026-09-25T10:25:14.381Z",
    "dateUpdated": "2026-10-26T06:56:52.637Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
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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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