CVE-2025-39939 (GCVE-0-2025-39939)

Vulnerability from cvelistv5 – Published: 2025-10-04 07:31 – Updated: 2026-10-15 22:02
VLAI
Title
iommu/s390: Fix memory corruption when using identity domain
Summary
In the Linux kernel, the following vulnerability has been resolved: iommu/s390: Fix memory corruption when using identity domain zpci_get_iommu_ctrs() returns counter information to be reported as part of device statistics; these counters are stored as part of the s390_domain. The problem, however, is that the identity domain is not backed by an s390_domain and so the conversion via to_s390_domain() yields a bad address that is zero'd initially and read on-demand later via a sysfs read. These counters aren't necessary for the identity domain; just return NULL in this case. This issue was discovered via KASAN with reports that look like: BUG: KASAN: global-out-of-bounds in zpci_fmb_enable_device when using the identity domain for a device on s390.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-15 21:54 UTC
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6971 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 64af12c6ec3afd7d44bc8b2044eee59f98059087 , < 17a58caf3863163c4a84a218a9649be2c8061443 (git)
Affected: 64af12c6ec3afd7d44bc8b2044eee59f98059087 , < b3506e9bcc777ed6af2ab631c86a9990ed97b474 (git)
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Linux Linux Affected: 6.15
Unaffected: 0 , < 6.15 (semver)
Unaffected: 6.16.9 , ≤ 6.16.* (semver)
Unaffected: 6.17 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Show details on NVD website
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              ]
            }
          ],
          "descriptions": [
            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\niommu/s390: Fix memory corruption when using identity domain\n\nzpci_get_iommu_ctrs() returns counter information to be reported as part\nof device statistics; these counters are stored as part of the s390_domain.\nThe problem, however, is that the identity domain is not backed by an\ns390_domain and so the conversion via to_s390_domain() yields a bad address\nthat is zero\u0027d initially and read on-demand later via a sysfs read.\nThese counters aren\u0027t necessary for the identity domain; just return NULL\nin this case.\n\nThis issue was discovered via KASAN with reports that look like:\nBUG: KASAN: global-out-of-bounds in zpci_fmb_enable_device\nwhen using the identity domain for a device on s390."
            }
          ],
          "metrics": [
            {
              "cvssV3_1": {
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "scenarios": [
                {
                  "lang": "en",
                  "value": "AV:L - The vulnerable code is s390 PCI/IOMMU infrastructure reached through local interfaces only \u2014 `pci_enable_device()` on driver bind and the debugfs `/sys/kernel/debug/pci/\u003cdev\u003e/statistics` file. There is no network-facing path to `zpci_get_iommu_ctrs()`.\nAC:L - Once a device uses the identity domain, the out-of-bounds access is fully deterministic \u2014 no race to win and no attacker-uninfluenceable memory layout \u2014 corrupting the same fixed 40-byte region on every `zpci_fmb_enable_device()` call and leaking it on every statistics read. Passthrough mode is a supported, documented runtime option on s390, not an obscure debug-only Kconfig.\nPR:L - The corrupting write happens automatically during normal `pci_enable_device()` at boot/driver bind with no attacker action at all, and the disclosure file is created world-readable (`S_IFREG | S_IRUGO | S_IWUSR`), so an unprivileged local user on a system with a traversable debugfs can harvest the leaked kernel global memory. No capability check gates `zpci_get_iommu_ctrs()` itself.\nUI:N - No victim action is needed; the counter reset fires on device enable and the OOB read happens on a plain file read. Nothing requires a second user to mount, open, or configure anything.\nS:U - The corruption and disclosure are confined to kernel `.data` within the kernel\u0027s own security authority \u2014 the bug mislocates statistics counters and does not alter IOMMU translation or bypass the DMA isolation boundary. Standard kernel-internal memory corruption is Unchanged scope.\nC:H - `pci_sw_counter_show()` reads 40 bytes past the end of `s390_identity_domain` and prints them verbatim to userspace, disclosing adjacent kernel global data such as `blocking_domain`\u0027s `ops`/`owner` function-pointer and structure pointers \u2014 a direct kernel address leak defeating KASLR and exposing kernel state.\nI:H - Five `atomic64_set()` calls zero 40 bytes of adjacent kernel global memory, overwriting live control structures \u2014 at +16 past the object this lands exactly on an `iommu_domain`\u0027s `const struct iommu_domain_ops *ops` field, nulling a function-pointer table. This is genuine kernel memory corruption of security-relevant control data, as the commit subject states.\nA:H - Zeroing adjacent globals (e.g. `blocking_domain.ops`) produces NULL-pointer dereferences in `__iommu_attach_device()` when the blocking/release domain is later attached, and KASAN reports a `global-out-of-bounds` BUG in `zpci_fmb_enable_device`. Both result in a kernel oops/panic."
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-08-05T12:06:14.864Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
          },
          "references": [
            {
              "url": "https://git.kernel.org/stable/c/17a58caf3863163c4a84a218a9649be2c8061443"
            },
            {
              "url": "https://git.kernel.org/stable/c/b3506e9bcc777ed6af2ab631c86a9990ed97b474"
            }
          ],
          "title": "iommu/s390: Fix memory corruption when using identity domain",
          "x_generator": {
            "engine": "bippy-1.2.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2025-39939",
        "datePublished": "2025-10-04T07:31:02.521Z",
        "dateReserved": "2025-04-16T07:20:57.148Z",
        "dateUpdated": "2026-10-15T22:02:33.574Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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