CVE-2026-98283 (GCVE-0-2026-98283)

Vulnerability from cvelistv5 – Published: 2026-10-06 08:45 – Updated: 2026-10-07 06:49
VLAI
Title
KVM: PPC: Book3S HV: fix use-after-free in kvmhv_emulate_tlbie_all_lpid()
Summary
In the Linux kernel, the following vulnerability has been resolved: KVM: PPC: Book3S HV: fix use-after-free in kvmhv_emulate_tlbie_all_lpid() kvmhv_emulate_tlbie_all_lpid() iterates the nested-guest IDR and drops mmu_lock before calling kvmhv_emulate_tlbie_lpid(), but does not hold a reference on the kvm_nested_guest pointer obtained from the IDR. A concurrent vCPU issuing a single-LPID tlbie (is=2, ric=2) can race through kvmhv_flush_nested() -> kvmhv_remove_nested() -> idr_remove / --refcnt -> kvmhv_release_nested() -> kfree(gp) in that window, leaving the iterating vCPU with a dangling pointer. The subsequent mutex_lock(&gp->tlb_lock) and accesses to gp->shadow_pgtable, gp->shadow_lpid and gp->l1_host all touch freed memory. The free path is fully L1-controlled. Fix this by incrementing gp->refcnt inside the loop before dropping mmu_lock, mirroring what kvmhv_get_nested() does, and releasing the reference with kvmhv_put_nested() after the per-guest work completes. This is the same get/put discipline already used at every other call site that drops mmu_lock while holding a nested-guest pointer.
Severity
8.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 54/100 over 6633 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: e3b6b4661527e821ffbe3db83952fdb1e6e47c49 , < 4d8f7b1f586375df8bce23a0909566ad5e852259 (git)
Affected: e3b6b4661527e821ffbe3db83952fdb1e6e47c49 , < e37fba1ba69385cff2d0e60b371ee19e7d1852d1 (git)
Affected: e3b6b4661527e821ffbe3db83952fdb1e6e47c49 , < 24b634852413229bb8340d908b115c3365f3a247 (git)
Affected: e3b6b4661527e821ffbe3db83952fdb1e6e47c49 , < fbf69b7d0555ee83c871f58750770f74b7179ad1 (git)
Affected: e3b6b4661527e821ffbe3db83952fdb1e6e47c49 , < ec2d7a52b3996ae81131617b4afc0af31583c1b4 (git)
Affected: e3b6b4661527e821ffbe3db83952fdb1e6e47c49 , < 51938dfa8a51a4f85328413fca9b6e21f9d2d088 (git)
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Linux Linux Affected: 4.20
Unaffected: 0 , < 4.20 (semver)
Unaffected: 6.1.189 , ≤ 6.1.* (semver)
Unaffected: 6.6.158 , ≤ 6.6.* (semver)
Unaffected: 6.12.112 , ≤ 6.12.* (semver)
Unaffected: 6.18.54 , ≤ 6.18.* (semver)
Unaffected: 7.2.8 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc4 , ≤ * (original_commit_for_fix)
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{
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      "cpeApplicability": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: PPC: Book3S HV: fix use-after-free in kvmhv_emulate_tlbie_all_lpid()\n\nkvmhv_emulate_tlbie_all_lpid() iterates the nested-guest IDR and drops\nmmu_lock before calling kvmhv_emulate_tlbie_lpid(), but does not hold a\nreference on the kvm_nested_guest pointer obtained from the IDR.  A\nconcurrent vCPU issuing a single-LPID tlbie (is=2, ric=2) can race\nthrough kvmhv_flush_nested() -\u003e kvmhv_remove_nested() -\u003e idr_remove /\n--refcnt -\u003e kvmhv_release_nested() -\u003e kfree(gp) in that window, leaving\nthe iterating vCPU with a dangling pointer.  The subsequent\nmutex_lock(\u0026gp-\u003etlb_lock) and accesses to gp-\u003eshadow_pgtable,\ngp-\u003eshadow_lpid and gp-\u003el1_host all touch freed memory.  The free path\nis fully L1-controlled.\n\nFix this by incrementing gp-\u003erefcnt inside the loop before dropping\nmmu_lock, mirroring what kvmhv_get_nested() does, and releasing the\nreference with kvmhv_put_nested() after the per-guest work completes.\nThis is the same get/put discipline already used at every other\ncall site that drops mmu_lock while holding a nested-guest pointer."
        }
      ],
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          "cvssV3_1": {
            "baseScore": 8.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The trigger is the H_TLB_INVALIDATE hcall made by code running inside an L1 guest on the POWER KVM-HV host, via kvmppc_pseries_do_hcall -\u003e kvmhv_do_nested_tlbie -\u003e kvmhv_emulate_priv_tlbie -\u003e kvmhv_emulate_tlbie_all_lpid. No network protocol carries the input; the attacker needs code execution in a local guest.\nAC:L - The L1 controls both sides of the race: one vCPU issues tlbie is=3 (all-LPID walk), another issues is=2 ric=2 after zeroing its own partition-table entry so kvmhv_flush_nested() calls kvmhv_remove_nested() and kfree(gp). Contention on gp-\u003etlb_lock widens the window and the attempt can be repeated. The only outside requirement is the VMM enabling KVM_CAP_PPC_NESTED_HV.\nPR:L - The attacker needs kernel/hypervisor-mode code in a nested-enabled L1 guest, which an ordinary tenant owns, but holds no privilege on the L0 host. The nesting_enabled() check is the only gate before kvmhv_do_nested_tlbie().\nUI:N - The L1 guest issues every hcall and controls every partition-table entry involved. No host operator or other user has to do anything.\nS:C - A guest-controlled vulnerability corrupts memory in the L0 host kernel (the kfree\u0027d kvm_nested_guest object), which crosses the guest-to-host boundary.\nC:H - After the free, kvmhv_emulate_tlbie_lpid() reads gp-\u003eshadow_pgtable, gp-\u003eshadow_lpid and gp-\u003el1_host from the dangling object. A reclaimed object lets the guest steer host page-table walks and host data reads.\nI:H - The freed gp is used for mutex_lock(\u0026gp-\u003etlb_lock), kvmppc_free_pgtable_radix() on gp-\u003eshadow_pgtable, and kvmhv_flush_nested()/kvmhv_put_nested() refcount writes. With a reclaimed object, these become host-kernel write and free primitives the guest controls.\nA:H - Using the freed kvm_nested_guest in the host can oops or panic the L0 host kernel, taking down every guest on the machine. The L1 can trigger it again at will."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-07T06:49:54.642Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/4d8f7b1f586375df8bce23a0909566ad5e852259"
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        {
          "url": "https://git.kernel.org/stable/c/e37fba1ba69385cff2d0e60b371ee19e7d1852d1"
        },
        {
          "url": "https://git.kernel.org/stable/c/24b634852413229bb8340d908b115c3365f3a247"
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        },
        {
          "url": "https://git.kernel.org/stable/c/51938dfa8a51a4f85328413fca9b6e21f9d2d088"
        }
      ],
      "title": "KVM: PPC: Book3S HV: fix use-after-free in kvmhv_emulate_tlbie_all_lpid()",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98283",
    "datePublished": "2026-10-06T08:45:44.593Z",
    "dateReserved": "2026-09-25T10:25:14.335Z",
    "dateUpdated": "2026-10-07T06:49:54.642Z",
    "state": "PUBLISHED"
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      "date": "2026-10-08",
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      "percentile": "0.02526"
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: PPC: Book3S HV: fix use-after-free in kvmhv_emulate_tlbie_all_lpid()\n\nkvmhv_emulate_tlbie_all_lpid() iterates the nested-guest IDR and drops\nmmu_lock before calling kvmhv_emulate_tlbie_lpid(), but does not hold a\nreference on the kvm_nested_guest pointer obtained from the IDR.  A\nconcurrent vCPU issuing a single-LPID tlbie (is=2, ric=2) can race\nthrough kvmhv_flush_nested() -\u003e kvmhv_remove_nested() -\u003e idr_remove /\n--refcnt -\u003e kvmhv_release_nested() -\u003e kfree(gp) in that window, leaving\nthe iterating vCPU with a dangling pointer.  The subsequent\nmutex_lock(\u0026gp-\u003etlb_lock) and accesses to gp-\u003eshadow_pgtable,\ngp-\u003eshadow_lpid and gp-\u003el1_host all touch freed memory.  The free path\nis fully L1-controlled.\n\nFix this by incrementing gp-\u003erefcnt inside the loop before dropping\nmmu_lock, mirroring what kvmhv_get_nested() does, and releasing the\nreference with kvmhv_put_nested() after the per-guest work completes.\nThis is the same get/put discipline already used at every other\ncall site that drops mmu_lock while holding a nested-guest pointer."
          }
        ],
        "id": "CVE-2026-98283",
        "lastModified": "2026-10-07T07:17:08.070",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 8.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "CHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
                "version": "3.1"
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              "impactScore": 6.0,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
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        "published": "2026-10-06T09:18:18.333",
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          },
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          },
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/e37fba1ba69385cff2d0e60b371ee19e7d1852d1"
          },
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          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/fbf69b7d0555ee83c871f58750770f74b7179ad1"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-10-08T16:48:39Z",
      "cve": "CVE-2026-98283",
      "id": "CVE-2026-98283",
      "initial_release_date": "2026-10-08T16:48:39Z",
      "product_status:known_affected": "208",
      "product_status:known_not_affected": "139",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-98283",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-98283.json",
      "version": "2"
    }
  }
}



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