bpf: Fix BPF_F_CPU validation for sparse CPU IDs

{
  "id": "f75e954239152d7624cad2d1df6417b437613a8486bba9d4fd26658aa1ae312b",
  "url": "https://osv.dev/vulnerability/CVE-2026-98150",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "bpf: Fix BPF_F_CPU validation for sparse CPU IDs",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: bpf: Fix BPF_F_CPU validation for sparse CPU IDs BPF_F_CPU stores the target CPU ID in the upper 32 bits of the map operation flags. bpf_map_check_op_flags() currently compares that ID with num_possible_cpus(), which is the number of possible CPUs rather than a bound on CPU IDs. On an arm64 QEMU guest with a CPU device-tree hole, the possible CPU mask was 0,2-3. A userspace program using raw bpf() syscalls creates a BPF_MAP_TYPE_PERCPU_ARRAY and performs update and lookup operations for each CPU by setting BPF_F_CPU and the CPU ID in the flags. With the old check, CPU 1 is incorrectly accepted while valid CPU 3 is rejected with -ERANGE. The CPU 1 update then reaches the per-CPU map access path and triggers: Unable to handle kernel paging request at virtual address ... pc : __pi_memcpy_generic+0x5c/0x22c lr : bpf_percpu_array_update+0x2dc/0x2e8 Call trace: __pi_memcpy_generic bpf_map_update_value map_update_elem __sys_bpf Check the CPU ID against nr_cpu_ids and cpu_possible() instead. This rejects CPU IDs outside the valid range and CPUs absent from the possible mask, while allowing valid sparse CPU IDs.",
    "evidence": "osv:CVE-2026-98150",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "7.2.7",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-98150",
      "aliases": [
        "CVE-2026-98150"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "2b421662c7887a0649fe409155a1f101562d0fa9"
                },
                {
                  "fixed": "bdc5941f6eeef90b76a07fd8ca38ac1933ba2195"
                },
                {
                  "fixed": "ed54bf564ac52699cf4def3d0c2125d493e756f9"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98150.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-2026-98150.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:42.439657295Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/bdc5941f6eeef90b76a07fd8ca38ac1933ba2195",
        "https://git.kernel.org/stable/c/ed54bf564ac52699cf4def3d0c2125d493e756f9",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98150.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-98150",
        "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-2026-98150.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-98150",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 510177,
  "published_at": "2026-09-25T10:36:22.774+00:00"
}