arm64: gcs: Do not set PTE_SHARED on GCS mappings if FEAT_LPA2 is enabled

{
  "id": "8e643e76982a82b782548da5dd9519fe03c48e97836f5bfc95a93eb6c6e00bc1",
  "url": "https://osv.dev/vulnerability/CVE-2026-23345",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "arm64: gcs: Do not set PTE_SHARED on GCS mappings if FEAT_LPA2 is enabled",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: arm64: gcs: Do not set PTE_SHARED on GCS mappings if FEAT_LPA2 is enabled When FEAT_LPA2 is enabled, bits 8-9 of the PTE replace the shareability attribute with bits 50-51 of the output address. The _PAGE_GCS{,_RO} definitions include the PTE_SHARED bits as 0b11 (this matches the other _PAGE_* definitions) but using this macro directly leads to the following panic when enabling GCS on a system/model with LPA2: Unable to handle kernel paging request at virtual address fffff1ffc32d8008 Mem abort info: ESR = 0x0000000096000004 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x04: level 0 translation fault Data abort info: ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 swapper pgtable: 4k pages, 52-bit VAs, pgdp=0000000060f4d000 [fffff1ffc32d8008] pgd=100000006184b003, p4d=0000000000000000 Internal error: Oops: 0000000096000004 [#1] SMP CPU: 0 UID: 0 PID: 513 Comm: gcs_write_fault Tainted: G M 7.0.0-rc1 #1 PREEMPT Tainted: [M]=MACHINE_CHECK Hardware name: QEMU QEMU Virtual Machine, BIOS 2025.02-8+deb13u1 11/08/2025 pstate: 03402005 (nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--) pc : zap_huge_pmd+0x168/0x468 lr : zap_huge_pmd+0x2c/0x468 sp : ffff800080beb660 x29: ffff800080beb660 x28: fff00000c2058180 x27: ffff800080beb898 x26: fff00000c2058180 x25: ffff800080beb820 x24: 00c800010b600f41 x23: ffffc1",
    "evidence": "osv:CVE-2026-23345",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.18.17",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.19.7",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-23345",
      "aliases": [
        "CVE-2026-23345"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "6497b66ba6945f142902c7e8fce86e47016ead1c"
                },
                {
                  "fixed": "ca1684dd297bf0725c1d487cff80e615497accf6"
                },
                {
                  "fixed": "1df3ef7e612d6ccbae5a48e1121553c47c2123d6"
                },
                {
                  "fixed": "8a85b3131225a8c8143ba2ae29c0eef8c1f9117f"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-23345.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.17"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "6.19.7"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-23345.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:31.073922021Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/1df3ef7e612d6ccbae5a48e1121553c47c2123d6",
        "https://git.kernel.org/stable/c/8a85b3131225a8c8143ba2ae29c0eef8c1f9117f",
        "https://git.kernel.org/stable/c/ca1684dd297bf0725c1d487cff80e615497accf6",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23345.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-23345",
        "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-2026-23345.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-23345",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 497913,
  "published_at": "2026-03-25T10:27:32.432+00:00"
}