net: ipv4: fix ARM64 alignment fault in multipath hash seed

{
  "id": "ee8bbfd07a7a9a54db311f5953bbf5f501c535bc43ea535c292ccdc258463d31",
  "url": "https://osv.dev/vulnerability/CVE-2026-23316",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "net: ipv4: fix ARM64 alignment fault in multipath hash seed",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: net: ipv4: fix ARM64 alignment fault in multipath hash seed `struct sysctl_fib_multipath_hash_seed` contains two u32 fields (user_seed and mp_seed), making it an 8-byte structure with a 4-byte alignment requirement. In `fib_multipath_hash_from_keys()`, the code evaluates the entire struct atomically via `READ_ONCE()`: mp_seed = READ_ONCE(net->ipv4.sysctl_fib_multipath_hash_seed).mp_seed; While this silently works on GCC by falling back to unaligned regular loads which the ARM64 kernel tolerates, it causes a fatal kernel panic when compiled with Clang and LTO enabled. Commit e35123d83ee3 (\"arm64: lto: Strengthen READ_ONCE() to acquire when CONFIG_LTO=y\") strengthens `READ_ONCE()` to use Load-Acquire instructions (`ldar` / `ldapr`) to prevent compiler reordering bugs under Clang LTO. Since the macro evaluates the full 8-byte struct, Clang emits a 64-bit `ldar` instruction. ARM64 architecture strictly requires `ldar` to be naturally aligned, thus executing it on a 4-byte aligned address triggers a strict Alignment Fault (FSC = 0x21). Fix the read side by moving the `READ_ONCE()` directly to the `u32` member, which emits a safe 32-bit `ldar Wn`. Furthermore, Eric Dumazet pointed out that `WRITE_ONCE()` on the entire struct in `proc_fib_multipath_hash_set_seed()` is also flawed. Analysis shows that Clang splits this 8-byte write into two separate 32-bit `str` instructions. While this avoids an alignment fault, it ",
    "evidence": "osv:CVE-2026-23316",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.12.77",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.17",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.19.7",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-23316",
      "aliases": [
        "CVE-2026-23316"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                {
                  "fixed": "7e4ad34a8889a6a9e0f6cc7c55d02161fe31a199"
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                {
                  "fixed": "607e923a3c1b2120de430b3dcde25ed8ad213c0a"
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                {
                  "fixed": "4ee7fa6cf78ff26d783d39e2949d14c4c1cd5e7f"
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            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-23316.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
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                  "introduced": "6.11.0"
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            {
              "type": "ECOSYSTEM",
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                {
                  "fixed": "6.18.17"
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            {
              "type": "ECOSYSTEM",
              "events": [
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                  "introduced": "6.19.0"
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                {
                  "fixed": "6.19.7"
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          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-23316.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:52.526419654Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/4bdc94d45d5459f0149085dfc1efe733c8e14f11",
        "https://git.kernel.org/stable/c/4ee7fa6cf78ff26d783d39e2949d14c4c1cd5e7f",
        "https://git.kernel.org/stable/c/607e923a3c1b2120de430b3dcde25ed8ad213c0a",
        "https://git.kernel.org/stable/c/7e4ad34a8889a6a9e0f6cc7c55d02161fe31a199",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23316.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-23316",
        "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-2026-23316.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-23316",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 521060,
  "published_at": "2026-03-25T10:27:11.028+00:00"
}