bpf: check_cond_jmp_op(): properly infer if register is null

{
  "id": "811a0a4fabcf590624e5d880b97cd21b6f743615b2ed5c55181a2aa4d20af3a3",
  "url": "https://osv.dev/vulnerability/CVE-2026-98134",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "bpf: check_cond_jmp_op(): properly infer if register is null",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: bpf: check_cond_jmp_op(): properly infer if register is null Nicholas Carlini reported a bug when verifier can incorrectly infer that a pointer is non-null. The bug occurs when two pointers are compared and one of them has a type w/o PTR_MAYBE_NULL flag, but which allows a value to be NULL at runtime. Here is an example: // `a` is PTR_TO_MEM | MEM_RDONLY | PTR_UNTRUSTED // `a` is 0 at runtime. // `b` is PTR_TO_MAP_VALUE | PTR_MAYBE_NULL void *a = bpf_rdonly_cast(0, 0); int *b = bpf_map_lookup_elem(...); if (a == b) *b = 42; // verifier does not catch null pointer dereference This happens because of a special case in check_cond_jmp_op(), which attempts to strip PTR_MAYBE_NULL flags from pointer types, when processing comparisons like `rA == rB`, if either rA or rB can't be null. The non-null property is derived based on the absence of PTR_MAYBE_NULL flag on rA's or rB's type. But that is not sufficient for types like PTR_TO_MEM, as in the example. This patch replaces type_may_be_null() call with reg_not_null(), which contains an allowlist of types for which absence of PTR_MAYBE_NULL actually means that the value can't be NULL at runtime. At the moment, the list in the reg_not_null() omits two types for which PTR_MAYBE_NULL is applicable: PTR_TO_XDP_SOCK and PTR_TO_BUF. In order to remain backward compatible, and assuming that only comparison between pointers of the same type makes sense, this commit extends re",
    "evidence": "osv:CVE-2026-98134",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.6.160",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.114",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.57",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.7",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-98134",
      "aliases": [
        "CVE-2026-98134"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "befae75856ab406a3f3fab2aa2118cf3b2dfe3e6"
                },
                {
                  "fixed": "d51cd486930f5bcfd4b55d55ab8e47b03f93d2ed"
                },
                {
                  "fixed": "dfd8f8adda565e08c370c45cf9d6b2511ba9b5c6"
                },
                {
                  "fixed": "9bf96b4347f541604b3caadeabda0773d9ceaf2a"
                },
                {
                  "fixed": "b55c9f019e169ed0d01394f96e172286a8b21b99"
                },
                {
                  "fixed": "d3ef6c097ba078e1f8c7239d76a0ce8b61e75095"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98134.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.6.160"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.114"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.57"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.2.7"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98134.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:23.058196288Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/9bf96b4347f541604b3caadeabda0773d9ceaf2a",
        "https://git.kernel.org/stable/c/b55c9f019e169ed0d01394f96e172286a8b21b99",
        "https://git.kernel.org/stable/c/d3ef6c097ba078e1f8c7239d76a0ce8b61e75095",
        "https://git.kernel.org/stable/c/d51cd486930f5bcfd4b55d55ab8e47b03f93d2ed",
        "https://git.kernel.org/stable/c/dfd8f8adda565e08c370c45cf9d6b2511ba9b5c6",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98134.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-98134",
        "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-2026-98134.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-98134",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 489684,
  "published_at": "2026-09-25T10:36:12.919+00:00"
}