{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-68093",
  "modified": "2026-10-07T17:22:01Z",
  "upstream": [
    "CVE-2026-68093"
  ],
  "published": "2026-08-10T12:08:00Z",
  "summary": "KVM: SVM: Bump asid_generation on CPU online to avoid ASID collision after hotplug",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SVM: Bump asid_generation on CPU online to avoid ASID collision after hotplug\n\nIf a vCPU stays scheduled out (or blocked) while the last pCPU it ran\non goes through a hotplug cycle (online->offline->online), and the vCPU\nthen resumes execution on the same pCPU, then it is possible for it to\nrun with an ASID that has now been assigned to a different vCPU,\nresulting in stale TLB translations being used.\n\nsvm_enable_virtualization_cpu() resets asid_generation to 1 and sets\nnext_asid to max_asid + 1 on every CPU online event, including hotplug\ncycles.  Because next_asid starts beyond the pool boundary, the first\ncall to new_asid() after an online event always wraps the pool,\nincrementing asid_generation to 2 and assigning ASIDs starting from\nmin_asid.\n\nConsider two vCPUs from different VMs, vCPU-A pinned to CPU-X holding\nasid_generation=2 and ASID=N from before the hotplug event:\n\n  1. CPU-X goes offline and back online: asid_generation resets to 1,\n     next_asid = max_asid + 1.\n\n  2. One or more vCPUs migrate to CPU-X and call new_asid(), wrapping\n     the pool and consuming ASIDs starting from min_asid.  Eventually\n     vCPU-B from a different VM is assigned asid_generation=2, ASID=N\n     \u2014 the same ASID that vCPU-A held before the hotplug.\n\n  3. vCPU-A enters pre_svm_run() on CPU-X: current_vmcb->cpu is\n     unchanged so the migration branch is skipped.  Its saved\n     asid_generation=2 matches sd->asid_generation=2, so the generation\n     check silently passes and vCPU-A continues running with ASID=N \u2014\n     the same ASID just freshly assigned to vCPU-B.\n\nBoth vCPUs from different VMs now run on CPU-X with the same ASID,\ncausing them to share NPT TLB entries and producing stale translations.\n\nThe collision manifests as a KVM internal error (Suberror: 1, emulation\nfailure).  The NPT page fault reports a faulting GPA far outside the\nVM's physical memory range \u2014 a sign of stale TLB translations being\nused.  KVM falls back to instruction emulation, which fails on\nFPU/XSave instructions (XRSTOR, STMXCSR) that the emulator does not\nimplement.\n\nFix this by incrementing asid_generation instead of resetting it to 1\nin svm_enable_virtualization_cpu().  On module load, asid_generation\nstarts at 0 (memset) and the increment produces 1, identical to the\nold behaviour.  On subsequent hotplug cycles the generation advances\nbeyond any value a vCPU previously observed on this CPU, so the\ngeneration check in pre_svm_run() reliably forces new_asid() on every\nvCPU after every hotplug cycle.",
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
      "versions": [
        "1:6.1.47-1+rpt4"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-2712",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v6",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v8",
            "binary_version": "1:6.1.47-1+rpt4"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.1.47-1+rpt4": {
            "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e",
            "upstream_version": "6.1.47",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.1.183",
            "compiled_filter": false
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-68093"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/2028b81321dc757b6875b99c10d908e349c141e2"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/60283726f2845bd78b95efbd0e50b93944780477"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/7508916b4b55d6f5ecc68cd09774dabd3a6b4440"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/0f33b1c457c2199ed130b92cc2ff363a3f7b9415"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/6b542d116acecb83a1ca34e8eace304cff6a4ec9"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/25f744ffa0c8e799e06250ce2e618367b166b0d4"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-19T16:47:12Z"
  }
}