From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98474][MODERATE REGULAR] s390/pci: Fix missing device lock in zpci_report_status() Date: Sat, 24 Oct 2026 04:17:11 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98474 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: 4 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 743a8458978d13d84a1cf74bcd29b9959a75d3a0 List-Id: CVE: CVE-2026-98474 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: s390/pci: Fix missing device lock in zpci_report_status() Commit: 743a8458978d13d84a1cf74bcd29b9959a75d3a0 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=743a8458978d13d84a1cf74bcd29b9959a75d3a0 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98474 Analysis date: Sat, 24 Oct 2026 04:17:11 -0400 ActionableScore: 4 ActionableScore lower bound: unknown Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: Missing device locking permits s390 zPCI recovery reporting to dereference a stale PCI driver while formatting diagnostic status, potentially crashing the kernel. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98474 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98474 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-2026-98474 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98474 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=MODERATE RESULT=DIFF (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H';CWE-362;*CWE-416;*CWE-672;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.3';DESCR 'A race in s390 zPCI status reporting can access pdev error state and the attached driver while device detach or recovery changes that state. The driver pointer may become stale before driver name formatting, creating a possible read side use after free or invalid pointer dereference and a kernel crash. For the CVSS the PR:L value in the paranoid vector assumes a restricted service account or delegated device manager can initiate driver detach or recovery operations. Normal unprivileged local users cannot directly trigger this path, and the base vector therefore uses PR:H. AC:H applies because exploitation depends on winning a race between PCI recovery reporting and a driver state transition. The issue is local to s390 zPCI and is not directly network reachable. Availability impact is supported. Limited confidentiality impact is retained only as a worst case because stale string data could enter a diagnostic report, while no write primitive or supported privilege escalation path is present. Automated impact decision path. The original SimpleNet classifier selected MODERATE. The primary LLM estimated paranoid CVSS 5.3 and the production ActionableScore returned 4 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were V41_INHERITED_KPANIC_PROMOTION_BLOCKED and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 1.9 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) MAYBE PRINTF-TTY SIMPLEFIX HARDWARE LINUS V41_INHERITED_KPANIC_PROMOTION_BLOCKED MANUAL_REVIEW_REQUIRED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 PrimitiveClass=CLASS_B RealUAF=YES HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES RequiresHostUID0=UNKNOWN AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 1. * Conservative score: 4. Real-UAF floor 4 applied: 1 -> 4. * Raw paranoid score: 1. * Paranoid score: 4. Same floor applied; no separate disclosure point is justified. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown * +2: Real read-side lifetime violation. Without the device lock, `pdev->dev.driver` can change during driver detach/recovery, and the saved `pci_driver` is subsequently dereferenced for `driver->name`. * +1: Plausible kernel crash from dereferencing a stale or invalid driver pointer. * -2: The vulnerable path is specific to uncommon s390 zPCI hardware and PCI recovery/status-reporting activity. * No confidentiality point: the report consumes `driver->name`, but no attacker-visible diagnostic disclosure path is shown. * No structured-object leverage: only `error_state` and the driver name are formatted; no write, callback, refcount mutation, controlled reclaim, or attacker-shaped replacement is shown. * No extra availability point: it would duplicate the same possible crash. * No authorization, B4-PENDING, B5-R, shared-backing, or active-state cross-boundary primitive is present. 3. Reachability analysis The call site is PCI error recovery on s390 zPCI. Normal unprivileged triggering is not shown. The hints suggest either host-level device management or a delegated device manager, but do not establish the complete privilege requirement, so `HostAdminRequired` and UID-0 requirements remain unknown. This is host-global device state, not a user/net-namespace-scoped capability path. Winning a detach/recovery race is required, but the evidence does not quantify it sufficiently for a separate timing penalty. 4. Primitive and severity reading This is a constrained CLASS_B read-side UAF/stale-object race involving an active `pci_driver`, not fixed buffer storage. The stale use is shallow diagnostic formatting during recovery, with crash as the supported effect. No post-lifetime write or useful exploitation primitive remains after excluding the fault. Therefore it is not an Important candidate, and downgrade remains permissible after review. 5. One-sentence report phrase Missing device locking permits s390 zPCI recovery reporting to dereference a stale PCI driver while formatting diagnostic status, potentially crashing the kernel. 6. Manual review advice MANUAL CHECK RECOMMENDED Confirm driver-unregister concurrency, diagnostic report exposure, and the actual privilege needed to induce recovery or detach. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: s390/pci: Fix missing device lock in zpci_report_status() Commit: 743a8458978d13d84a1cf74bcd29b9959a75d3a0 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=743a8458978d13d84a1cf74bcd29b9959a75d3a0 Commit description: When pdev is non-NULL, zpci_report_status() accesses the device's driver. To get a consistent state matching the recovery, the device lock needs to be held. Do so by expanding the existing device lock critical section. The lock only needs to be held when the pdev is non-NULL, so extract the pdev-specific reporting into a helper function which also adds a lockdep assertion to detect calls without the device lock held. Cc: stable@vger.kernel.org Fixes: 4ec6054 ("s390/pci: Report PCI error recovery results via SCLP") Signed-off-by: Niklas Schnelle Reviewed-by: Benjamin Block Reviewed-by: Farhan Ali Signed-off-by: Heiko Carstens Signed-off-by: Greg Kroah-Hartman Changed files: arch/s390/pci/pci_event.c arch/s390/pci/pci_report.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=743a8458978d13d84a1cf74bcd29b9959a75d3a0 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98474 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98474 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:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H The Best / paranoid CVSS score: 5.3 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: unknown Paranoid ActionableScore: 4 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).