From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-68347][MODERATE REGULAR] iommu/amd: Fix IRQ unsafe locking in gdom allocation [ Upstream Date: Mon, 10 Aug 2026 19:28:24 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-68347 X-AL-KERNEL-Priority: MODERATE REGULAR X-AL-KERNEL-Severity: MODERATE REGULAR X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 3 X-AL-KERNEL-ActionableScore-Lower: 2 X-AL-KERNEL-Commit: e0c78cdf35af3ada05f9309f4641e9f83c945dbd List-Id: CVE: CVE-2026-68347 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: iommu/amd: Fix IRQ unsafe locking in gdom allocation [ Upstream Commit: e0c78cdf35af3ada05f9309f4641e9f83c945dbd Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e0c78cdf35af3ada05f9309f4641e9f83c945dbd Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68347 Analysis date: Mon, 10 Aug 2026 19:28:24 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline Moderate / manual review recommended Manual review required: YES Summary: AMD IOMMU nested-domain gdom allocation used IRQ-unsafe xarray locking in paths that can interact with hardirq-safe IOTLB flush handling, allowing a local virtualization or device-assignment control process to potentially trigger a host deadlock or lockup. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68347 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68347 The original announcement does not normally provide a security severity estimate, CVSS assessment, or enough information to determine whether the reported kernel bug represents a practically relevant security issue. This report was generated by AL-KERNEL, an AI-assisted Linux kernel vulnerability analysis system developed by Alexander Larkin. It combines an autonomous classifier with LLM-assisted technical analysis and a separate ActionableScore mechanism. The purpose of this report is to prioritize Linux kernel CVEs before manual review, identify cases that require prompt investigation, and support automatic closure of issues that are unlikely to have meaningful security impact. Published priority for this report: MODERATE REGULAR Manual review required: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-68347 MODERATE CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-667;*CWE-833;CWE-821;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'AMD IOMMU nested domain allocation can create a hardirq unsafe lock ordering problem because the gdom xarray lock is taken without irqsave while related IOTLB flush paths may be reached from hardirq safe contexts. A local user or service that can drive iommufd or a QEMU based nested IOMMU setup may trigger a host lockup or deadlock during nested domain allocation, invalidation, or free operations. For the CVSS the PR:L is used because reliable triggering requires local execution with access to the virtualization or device assignment control path, but it does not necessarily require full host root in delegated VM or service account deployments. The issue is not network reachable by itself and packet traffic is not the direct attack vector. Impact is denial of service only through host hang or lockup, with no concrete evidence of information disclosure, memory corruption, or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline Moderate / manual review recommended (with actual score 3) SKIP CVE-2026-68347 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: 757d2b1fdf5b7d6eead5963a49b5780617987ab8 YES NO NO unknown MAYBE LOCK HARDWARE MEMORY DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 3 * Final recommended bucket: **Borderline Moderate / manual review recommended**:: ## 2. Signal breakdown Triggered signals: * Reliable kernel crash / strong DoS: +1 The lock ordering issue can plausibly lead to a host lockup or deadlock in AMD IOMMU nested-domain paths. * Availability impact realistic: +1 The affected path is host IOMMU code used by virtualization and device assignment. A deadlock here can affect the host, not only one guest process. * Local low-privileged or delegated service trigger: +1 in paranoid score Typical triggering is through iommufd / QEMU / VFIO-like device-assignment control paths. This is not ordinary remote reachability, but in delegated VM-service deployments the triggering process may be less than full host root. Negative / limiting signals: * Hard or timing-dependent condition: -1 conservative The issue is an IRQ-safe vs IRQ-unsafe lock ordering problem. The real deadlock depends on interrupt timing and concurrent IOMMU flush/allocation/free activity. * Rare / configuration-dependent subsystem: -1 conservative/paranoid The affected code is AMD IOMMU nested-domain handling, not a broad default kernel path. Not awarded: * No generic memory corruption bonus. The patch fixes locking mode and GFP context, not UAF, OOB write, double free, type confusion, or arbitrary write. * No privilege escalation bonus. The supplied patch and call path support host DoS, not LPE. * No confidentiality or integrity impact. There is no supported leak, overwrite, or policy-bypass primitive. * No remote/network trigger. Network traffic is not the direct attack vector. ## 3. Reachability analysis The likely trigger is local access to virtualization or device-assignment control paths, such as a QEMU process using iommufd with AMD IOMMU nested-domain support. In typical deployments this is not available to an arbitrary unprivileged user, but it may be reachable by a VM service account, containerized management process, or reduced-capability root process that is allowed to manage assigned devices. Namespaces do not automatically make this unprivileged, but delegated device-management setups can lower practical privilege from full host root to PR:L-like service access. The path is not network reachable by itself. Realistic exploitation requires AMD IOMMU nested-domain support and concurrent IOMMU invalidation/free/allocation activity sufficient to expose the unsafe lock ordering. Call-site confidence: high, because the provided trace and diff show the relevant iommufd ioctl path, AMD IOMMU nested allocation path, IOTLB flush path, and free path. ## 4. Severity interpretation This behaves like a Moderate host DoS issue with manual-review relevance, not an Important-class memory corruption vulnerability. The evidence supports a lock-ordering deadlock or host lockup, but not UAF, object reuse, attacker-controlled overwrite, information disclosure, or privilege escalation. The paranoid score is raised only to 3 because the affected subsystem is security-sensitive host virtualization / IOMMU infrastructure and may be reachable by delegated VM-management processes. It should not be treated as Strong Important based on the current patch evidence. ## 5. One-sentence report phrase AMD IOMMU nested-domain gdom allocation used IRQ-unsafe xarray locking in paths that can interact with hardirq-safe IOTLB flush handling, allowing a local virtualization or device-assignment control process to potentially trigger a host deadlock or lockup. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Reason: the issue is DoS-only from the supplied evidence, but it affects AMD IOMMU nested virtualization and iommufd-related host device-management paths, so product-specific exposure should be checked before auto-closing. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: iommu/amd: Fix IRQ unsafe locking in gdom allocation [ Upstream Commit: e0c78cdf35af3ada05f9309f4641e9f83c945dbd Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e0c78cdf35af3ada05f9309f4641e9f83c945dbd Changed files: drivers/iommu/amd/nested.c Diff excerpt: Not included in this email. See the upstream URL for the full patch. Full patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e0c78cdf35af3ada05f9309f4641e9f83c945dbd ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68347 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68347 The original CVE announcement normally does not include a security-level estimate. In particular, it may not contain a CVSS assessment, an impact level, or enough information to determine whether the reported bug is a practically relevant security issue. One purpose of this parallel CVE list is to provide that missing technical and prioritization information. The original goal of the AL-KERNEL project was to prioritize Linux kernel CVE analysis automatically before manual review. The system can also help identify non-security issues that may be suitable for automatic closure. This report was generated by AL-KERNEL, an AI-assisted Linux kernel vulnerability analysis system developed by Alexander Larkin. The first analysis stage combines an autonomous classifier with additional LLM-based analysis. The autonomous classifier runs locally on a CPU and is based on a backpropagation neural network. Together, these mechanisms produce a technical vulnerability description, identify likely weakness types, estimate CVSS severity, and provide input for ActionableScore. Two CVSS estimates are retained because incomplete kernel vulnerability information often permits more than one defensible interpretation: Conservative CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.5 The conservative vector represents a lower-impact interpretation. The Best/paranoid vector intentionally represents a plausible upper-bound interpretation and should not automatically be treated as demonstrated real-world impact. CVSS may also need to be adjusted for a particular Linux deployment, because actual reachability, privileges, enabled kernel configuration, hardware, namespaces, exposed device nodes, and other environmental conditions can differ significantly between systems. A separate ActionableScore mechanism evaluates practical remediation urgency. Its analysis may include reachability, attack prerequisites, subsystem exposure, memory-corruption characteristics, denial-of-service reliability, and possible confidentiality, integrity, or privilege-escalation impact. Conservative ActionableScore: 2 Paranoid ActionableScore: 3 The final base severity is taken directly from the second tab-separated field of the AL-KERNEL classification result. ActionableScore does not replace or independently override that final AL-KERNEL decision, and if ActionableScore adjusted impact level of ALKERNEL, then you would see self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7. For an AL-KERNEL result of MODERATE, this report uses the following additional presentation split: ActionableScore below 5 -> MODERATE REGULAR ActionableScore 5 or more -> MODERATE 7.0 The distinction between MODERATE REGULAR and MODERATE 7.0 makes it possible to identify Moderate issues that should receive manual analysis and fixes before lower-priority MODERATE REGULAR issues. In many cases, MODERATE REGULAR fixes may wait for a later rebase or routine update. There is one override in which MODERATE REGULAR becomes MODERATE 7.0 even when the ActionableScore is below 5. When the AL-KERNEL result contains the KPANIC flag, a MODERATE result is always presented as MODERATE 7.0. The KPANIC flag selected with few regexps without usage of AI at all, so it helps to detect cases when Kernel Crash happens and similar (to filter False-Negative results from the LLM usage). KPANIC indicates that a reliable kernel crash, kernel panic, or similarly serious kernel availability impact was identified by the classification workflow. AL-KERNEL base severity for this report: MODERATE KPANIC detected for this report: NO Published priority for this report (same as in Subject): MODERATE REGULAR These results are intended to support engineering triage. They are machine-generated estimates, and cases marked for manual review should be validated by a human security engineer before final disposition. For more info read docs linked from here: https://kernelcve.org/ (and you can submit you own patch there to generate such a report for non-existant CVE-id yet). Note that in many cases this AI tool selects higher severity, than real is (means you can expect Importants instead of Moderate 7.0 or Moderates 7.0 instead of regular Moderates). If you see such cases, please use reply email interface to add additional manual analyses info to this particular CVE. And please, please, let me know when you see Lows instead of Importants or Important instead of Low (because particular for such cases I need to tune this AI tool to make it better for this one and next similar). My contact email for such notifications is alexanjelausa@gmail.com (and both send reply to CVE record itself too and see "reply" button below for howto reply).