From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-72290][LOW] KVM: s390: pci: Fix GISC refcount leak on AIF enable failure Date: Sat, 15 Aug 2026 03:27:09 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-72290 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 1 X-AL-KERNEL-ActionableScore-Lower: 0 X-AL-KERNEL-Commit: 3882224b0e714f34de91e5f28307c5d3fccfe8f8 List-Id: CVE: CVE-2026-72290 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: KVM: s390: pci: Fix GISC refcount leak on AIF enable failure Commit: 3882224b0e714f34de91e5f28307c5d3fccfe8f8 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3882224b0e714f34de91e5f28307c5d3fccfe8f8 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72290 Analysis date: Sat, 15 Aug 2026 03:27:09 -0400 ActionableScore: 1 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72290 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72290 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: LOW Manual review required: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-72290 LOW 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:H/UI:N/S:U/C:N/I:N/A:H';*CWE-772;CWE-404;**CWE-400;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'KVM s390 PCI AIF enable can leak a GISC reference when kvm_s390_gisc_register() succeeds but a later setup step fails before interrupt forwarding is fully enabled. Repeated failed enable attempts may leave stale GISC references and can degrade or exhaust resources related to guest interrupt forwarding. For the CVSS the PR:H is selected because reliable triggering normally requires host side control of KVM VM setup and s390 PCI passthrough configuration. The issue is not network reachable and is triggered through local virtualization control paths. Impact is denial of service through resource leakage, with no concrete UAF, OOB access, information disclosure, or privilege escalation primitive visible from the patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) YES VIRT INIT SIMPLEFIX LEAK HARDWARE LINUS NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 ActionableScoreLower=0 1. ActionableScore * Conservative score: 0 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate / Low-like**:: 2. Signal breakdown * Real lifetime/refcount bug: +1. `kvm_s390_gisc_register()` succeeds, but the error unwind path missed `kvm_s390_gisc_unregister()`, leaving a leaked GISC reference. * Availability impact realistic in paranoid interpretation: +1. Repeated failed AIF enable attempts could accumulate leaked references and degrade or exhaust interrupt-forwarding resources. * Requires admin/root/CAP-level control: -2. Reliable triggering normally requires host-side KVM VM management and s390 PCI interrupt forwarding or passthrough configuration. * Rare and difficult-to-reach subsystem/configuration: -1. This is limited to KVM on s390 with PCI AIF paths, not a broad default kernel interface. * No remote reachability, no local unprivileged trigger, no UAF, no OOB access, no arbitrary write, no demonstrated LPE primitive. 3. Reachability analysis The bug is reachable through local host virtualization control paths, not through guest packet/data input or the network. A normal unprivileged local user should not be able to trigger it unless they are delegated unusually broad KVM and PCI device-management access. Containers or namespaces do not normally lower this to PR:L unless the environment intentionally exposes host KVM device-management capabilities. Call-site confidence: medium. The commit message clearly describes the failed unwind path and missing unregister, but the full caller context is not included in the provided diff. 4. Severity interpretation This behaves like a low-end resource lifetime leak rather than an Important-class kernel vulnerability. The theoretical impact is DoS through resource exhaustion after repeated failures. There is no evidence of memory corruption, privilege escalation, information disclosure, guest-to-host escape, or attacker-controlled object reuse. 5. One-sentence report phrase A missing `kvm_s390_gisc_unregister()` in the KVM s390 PCI AIF enable error path can leak GISC references after setup failures, potentially causing resource-exhaustion DoS in privileged host-side virtualization configurations. 6. Manual review recommendation NO MANUAL CHECK NEEDED. This is a privileged, rare-configuration refcount leak with no concrete memory corruption or security-boundary bypass primitive, so it can be handled as low-priority/autoclose unless product-specific s390 KVM PCI exposure is unusually broad. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: KVM: s390: pci: Fix GISC refcount leak on AIF enable failure Commit: 3882224b0e714f34de91e5f28307c5d3fccfe8f8 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3882224b0e714f34de91e5f28307c5d3fccfe8f8 Commit description: kvm_s390_gisc_register() registers the guest ISC before pinning the guest interrupt forwarding pages and allocating the AISB bit. If any of the later setup steps fails, the function unwinds the pinned pages and other local state, but does not unregister the GISC reference. Add the missing kvm_s390_gisc_unregister() to the error unwind path. Fixes: 3c5a1b6 ("KVM: s390: pci: provide routines for enabling/disabling interrupt forwarding") Cc: stable@vger.kernel.org Signed-off-by: Haoxiang Li Reviewed-by: Matthew Rosato Tested-by: Matthew Rosato Acked-by: Claudio Imbrenda Reviewed-by: Christian Borntraeger Signed-off-by: Claudio Imbrenda Message-ID: <20260624061910.2794734-1-haoxiang_li2024@163.com> Signed-off-by: Christian Borntraeger Signed-off-by: Greg Kroah-Hartman Changed files: arch/s390/kvm/pci.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=3882224b0e714f34de91e5f28307c5d3fccfe8f8 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72290 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72290 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:L/PR:H/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.4 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: 0 Paranoid ActionableScore: 1 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: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW 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).