bpf: Fix percpu map update indexing with sparse CPU IDs

{
  "id": "182165dd992c6684dd39afc13e4d709606e90dcd4f64bd14f1ed6b4c0495649a",
  "url": "https://osv.dev/vulnerability/CVE-2026-98149",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "bpf: Fix percpu map update indexing with sparse CPU IDs",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: bpf: Fix percpu map update indexing with sparse CPU IDs Per-CPU array, hash, and cgroup storage map updates without BPF_F_CPU or BPF_F_ALL_CPUS use a value buffer whose per-CPU slots are packed in possible-CPU order. The buffer is sized as: round_up(value_size, 8) * num_possible_cpus() The update paths iterate over possible CPUs, but use the logical CPU ID to calculate the source offset: value + size * cpu This only works when possible CPU IDs are contiguous starting at zero. For example, with a possible CPU mask of 0,2-3, the buffer contains three slots corresponding to CPUs 0, 2, and 3. CPU2 is therefore expected to use slot 1 and CPU3 slot 2. Instead, the current code uses slots 2 and 3 respectively, causing incorrect per-CPU values and an out-of-bounds read from the update buffer for CPU3. The corresponding lookup paths already use a dense offset while iterating over possible CPUs. Do the same for the array, hash, and cgroup storage update paths, advancing the source offset once for each possible CPU. BPF_F_ALL_CPUS continues to use the same value for every CPU.",
    "evidence": "osv:CVE-2026-98149",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "7.2.7",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-98149",
      "aliases": [
        "CVE-2026-98149"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "8eb76cb03f0f6c2bd7b15cf45dcffcd6bd07a360"
                },
                {
                  "fixed": "c16c62c91e5d6737a9fbb0a541b8b34610470a2b"
                },
                {
                  "fixed": "75b0a6db4300e4c2c9e97a0848deaa7acfb42fb7"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98149.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "7.0.0"
                },
                {
                  "fixed": "7.2.7"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98149.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:26.351196160Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/75b0a6db4300e4c2c9e97a0848deaa7acfb42fb7",
        "https://git.kernel.org/stable/c/c16c62c91e5d6737a9fbb0a541b8b34610470a2b",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98149.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-98149",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98149.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-98149",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 493046,
  "published_at": "2026-09-25T10:36:22.182+00:00"
}