{"id":"CVE-2025-39939","state":"PUBLISHED","title":"iommu/s390: Fix memory corruption when using identity domain","description":"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'd initially and read on-demand later via a sysfs read.\nThese counters aren't 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.","publishedAt":"2025-10-04T07:31:02.521Z","updatedAt":"2026-10-15T22:02:33.574Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"64af12c6ec3afd7d44bc8b2044eee59f98059087","status":"affected","lessThan":"17a58caf3863163c4a84a218a9649be2c8061443","versionType":"git"},{"version":"64af12c6ec3afd7d44bc8b2044eee59f98059087","status":"affected","lessThan":"b3506e9bcc777ed6af2ab631c86a9990ed97b474","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/iommu/s390-iommu.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.15","versionType":"semver"},{"version":"6.16.9","status":"unaffected","lessThanOrEqual":"6.16.*","versionType":"semver"},{"version":"6.17","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/iommu/s390-iommu.c"]}],"references":["https://git.kernel.org/stable/c/17a58caf3863163c4a84a218a9649be2c8061443","https://git.kernel.org/stable/c/b3506e9bcc777ed6af2ab631c86a9990ed97b474"],"weaknesses":[],"ingestedAt":"2026-10-29T20:09:09.358Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2025/39xxx/CVE-2025-39939.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-39939","state":"PUBLISHED","datePublished":"2025-10-04T07:31:02.521Z","dateUpdated":"2026-10-15T22:02:33.574Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2025-04-16T07:20:57.148Z"},"containers":{"cna":{"title":"iommu/s390: Fix memory corruption when using identity domain","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'd initially and read on-demand later via a sysfs read.\nThese counters aren't 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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"64af12c6ec3afd7d44bc8b2044eee59f98059087","status":"affected","lessThan":"17a58caf3863163c4a84a218a9649be2c8061443","versionType":"git"},{"version":"64af12c6ec3afd7d44bc8b2044eee59f98059087","status":"affected","lessThan":"b3506e9bcc777ed6af2ab631c86a9990ed97b474","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/iommu/s390-iommu.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.15","versionType":"semver"},{"version":"6.16.9","status":"unaffected","lessThanOrEqual":"6.16.*","versionType":"semver"},{"version":"6.17","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/iommu/s390-iommu.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/17a58caf3863163c4a84a218a9649be2c8061443"},{"url":"https://git.kernel.org/stable/c/b3506e9bcc777ed6af2ab631c86a9990ed97b474"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The vulnerable code is s390 PCI/IOMMU infrastructure reached through local interfaces only — `pci_enable_device()` on driver bind and the debugfs `/sys/kernel/debug/pci/<dev>/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 — no race to win and no attacker-uninfluenceable memory layout — 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's own security authority — 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`'s `ops`/`owner` function-pointer and structure pointers — 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 — at +16 past the object this lands exactly on an `iommu_domain`'s `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":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:06:14.864Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"6.16.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"6.17"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2025-39939","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-15T21:54:54.159629Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-15T22:02:33.574Z"}}]}}}