KVM: VMX: Fix crash due to uninitialized current_vmcs

{
  "id": "2420974ff30f635a255f57dec908f1da8310b821d48359cfefb1fe55afdacb3d",
  "url": "https://osv.dev/vulnerability/CVE-2023-53756",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "KVM: VMX: Fix crash due to uninitialized current_vmcs",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: KVM: VMX: Fix crash due to uninitialized current_vmcs KVM enables 'Enlightened VMCS' and 'Enlightened MSR Bitmap' when running as a nested hypervisor on top of Hyper-V. When MSR bitmap is updated, evmcs_touch_msr_bitmap function uses current_vmcs per-cpu variable to mark that the msr bitmap was changed. vmx_vcpu_create() modifies the msr bitmap via vmx_disable_intercept_for_msr -> vmx_msr_bitmap_l01_changed which in the end calls this function. The function checks for current_vmcs if it is null but the check is insufficient because current_vmcs is not initialized. Because of this, the code might incorrectly write to the structure pointed by current_vmcs value left by another task. Preemption is not disabled, the current task can be preempted and moved to another CPU while current_vmcs is accessed multiple times from evmcs_touch_msr_bitmap() which leads to crash. The manipulation of MSR bitmaps by callers happens only for vmcs01 so the solution is to use vmx->vmcs01.vmcs instead of current_vmcs. BUG: kernel NULL pointer dereference, address: 0000000000000338 PGD 4e1775067 P4D 0 Oops: 0002 [#1] PREEMPT SMP NOPTI ... RIP: 0010:vmx_msr_bitmap_l01_changed+0x39/0x50 [kvm_intel] ... Call Trace: vmx_disable_intercept_for_msr+0x36/0x260 [kvm_intel] vmx_vcpu_create+0xe6/0x540 [kvm_intel] kvm_arch_vcpu_create+0x1d1/0x2e0 [kvm] kvm_vm_ioctl_create_vcpu+0x178/0x430 [kvm] kvm_vm_ioctl+0x53f/0x790 [kvm] __x64_sys_ioctl+0x8a",
    "evidence": "osv:CVE-2023-53756",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.10.175",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.15.103",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.16",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.2.3",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2023-53756",
      "aliases": [
        "CVE-2023-53756"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "ceef7d10dfb6284d512c499292e6daa35ea83f90"
                },
                {
                  "fixed": "6baebcecf09acd19e2bab1c2911dcdba5d48a1dc"
                },
                {
                  "fixed": "6e7bc50f97c9855da83f1478f722590defd45ff2"
                },
                {
                  "fixed": "b2de2b4d4e007f9add46ea8dc06f781835e3ea9f"
                },
                {
                  "fixed": "3ba95cc671c025d0d2a1c7d5e2930f0ff0980cf4"
                },
                {
                  "fixed": "93827a0a36396f2fd6368a54a020f420c8916e9b"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2023-53756.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "4.18.0"
                },
                {
                  "fixed": "5.10.175"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.11.0"
                },
                {
                  "fixed": "5.15.103"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.16.0"
                },
                {
                  "fixed": "6.1.16"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.2.3"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2023-53756.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:49.980194892Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/3ba95cc671c025d0d2a1c7d5e2930f0ff0980cf4",
        "https://git.kernel.org/stable/c/6baebcecf09acd19e2bab1c2911dcdba5d48a1dc",
        "https://git.kernel.org/stable/c/6e7bc50f97c9855da83f1478f722590defd45ff2",
        "https://git.kernel.org/stable/c/93827a0a36396f2fd6368a54a020f420c8916e9b",
        "https://git.kernel.org/stable/c/b2de2b4d4e007f9add46ea8dc06f781835e3ea9f",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/53xxx/CVE-2023-53756.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2023-53756",
        "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/2023/53xxx/CVE-2023-53756.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2023-53756",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 518546,
  "published_at": "2025-12-08T01:19:17.081+00:00"
}