sched/fair: Fix potential memory corruption in child_cfs_rq_on_list

{
  "id": "f96a0d8f091e752491ef8b73ded94209e94a6686aaa973b76ffec0ca6f2b1eb9",
  "url": "https://osv.dev/vulnerability/CVE-2025-21919",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "sched/fair: Fix potential memory corruption in child_cfs_rq_on_list",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: sched/fair: Fix potential memory corruption in child_cfs_rq_on_list child_cfs_rq_on_list attempts to convert a 'prev' pointer to a cfs_rq. This 'prev' pointer can originate from struct rq's leaf_cfs_rq_list, making the conversion invalid and potentially leading to memory corruption. Depending on the relative positions of leaf_cfs_rq_list and the task group (tg) pointer within the struct, this can cause a memory fault or access garbage data. The issue arises in list_add_leaf_cfs_rq, where both cfs_rq->leaf_cfs_rq_list and rq->leaf_cfs_rq_list are added to the same leaf list. Also, rq->tmp_alone_branch can be set to rq->leaf_cfs_rq_list. This adds a check `if (prev == &rq->leaf_cfs_rq_list)` after the main conditional in child_cfs_rq_on_list. This ensures that the container_of operation will convert a correct cfs_rq struct. This check is sufficient because only cfs_rqs on the same CPU are added to the list, so verifying the 'prev' pointer against the current rq's list head is enough. Fixes a potential memory corruption issue that due to current struct layout might not be manifesting as a crash but could lead to unpredictable behavior when the layout changes.",
    "evidence": "osv:CVE-2025-21919",
    "products": [
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    "severity": "high",
    "structured": {
      "id": "CVE-2025-21919",
      "aliases": [
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      "metrics": [
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      "modified": "2026-10-28T02:30:23.556904013Z",
      "provider": "osv",
      "references": [
        "https://cert-portal.siemens.com/productcert/html/ssa-019113.html",
        "https://cert-portal.siemens.com/productcert/html/ssa-457936.html",
        "https://git.kernel.org/stable/c/000c9ee43928f2ce68a156dd40bab7616256f4dd",
        "https://git.kernel.org/stable/c/3b4035ddbfc8e4521f85569998a7569668cccf51",
        "https://git.kernel.org/stable/c/5cb300dcdd27e6a351ac02541e0231261c775852",
        "https://git.kernel.org/stable/c/9cc7f0018609f75a349e42e3aebc3b0e905ba775",
        "https://git.kernel.org/stable/c/b5741e4b9ef3567613b2351384f91d3f16e59986",
        "https://git.kernel.org/stable/c/e1dd09df30ba86716cb2ffab97dc35195c01eb8f",
        "https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21919.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-21919",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
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      "provider_metadata": {
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
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  "source_id": "core-osv",
  "document_id": 489848,
  "published_at": "2025-04-01T15:40:54.075+00:00"
}