bpf: Fix constant blinding for PROBE_MEM32 stores

{
  "id": "9815122bc14af066c9a58bbf6f7ab28703c5886dbc26d71fd8cef0c9fbdc9151",
  "url": "https://osv.dev/vulnerability/CVE-2026-23417",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "bpf: Fix constant blinding for PROBE_MEM32 stores",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: bpf: Fix constant blinding for PROBE_MEM32 stores BPF_ST | BPF_PROBE_MEM32 immediate stores are not handled by bpf_jit_blind_insn(), allowing user-controlled 32-bit immediates to survive unblinded into JIT-compiled native code when bpf_jit_harden >= 1. The root cause is that convert_ctx_accesses() rewrites BPF_ST|BPF_MEM to BPF_ST|BPF_PROBE_MEM32 for arena pointer stores during verification, before bpf_jit_blind_constants() runs during JIT compilation. The blinding switch only matches BPF_ST|BPF_MEM (mode 0x60), not BPF_ST|BPF_PROBE_MEM32 (mode 0xa0). The instruction falls through unblinded. Add BPF_ST|BPF_PROBE_MEM32 cases to bpf_jit_blind_insn() alongside the existing BPF_ST|BPF_MEM cases. The blinding transformation is identical: load the blinded immediate into BPF_REG_AX via mov+xor, then convert the immediate store to a register store (BPF_STX). The rewritten STX instruction must preserve the BPF_PROBE_MEM32 mode so the architecture JIT emits the correct arena addressing (R12-based on x86-64). Cannot use the BPF_STX_MEM() macro here because it hardcodes BPF_MEM mode; construct the instruction directly instead.",
    "evidence": "osv:CVE-2026-23417",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.12.80",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.21",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.19.11",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-23417",
      "aliases": [
        "CVE-2026-23417"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "6082b6c328b5486da2b356eae94b8b83c98b5565"
                },
                {
                  "fixed": "56af722756ed82fee2ae5d5b4d04743407506195"
                },
                {
                  "fixed": "ccbf29b28b5554f9d65b2fb53b994673ad58b3bf"
                },
                {
                  "fixed": "de641ea08f8fff6906e169d2576c2ac54e562fbb"
                },
                {
                  "fixed": "2321a9596d2260310267622e0ad8fbfa6f95378f"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-23417.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.9.0"
                },
                {
                  "fixed": "6.12.80"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.21"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "6.19.11"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-23417.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:37.522962603Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/2321a9596d2260310267622e0ad8fbfa6f95378f",
        "https://git.kernel.org/stable/c/56af722756ed82fee2ae5d5b4d04743407506195",
        "https://git.kernel.org/stable/c/ccbf29b28b5554f9d65b2fb53b994673ad58b3bf",
        "https://git.kernel.org/stable/c/de641ea08f8fff6906e169d2576c2ac54e562fbb",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23417.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-23417",
        "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/2026/23xxx/CVE-2026-23417.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-23417",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 504524,
  "published_at": "2026-04-02T11:40:57.837+00:00"
}