From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-43398][MODERATE REGULAR] drm/amdgpu: add upper bound check on user inputs in wait ioctl Date: Sat, 01 Aug 2026 12:21:43 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-43398 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: b1d10508da559da2e0ca9cca6505094a7df948e1 List-Id: CVE: CVE-2026-43398 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: drm/amdgpu: add upper bound check on user inputs in wait ioctl Commit: b1d10508da559da2e0ca9cca6505094a7df948e1 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b1d10508da559da2e0ca9cca6505094a7df948e1 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43398 Analysis date: Sat, 01 Aug 2026 12:21:43 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Ordinary Moderate / Borderline local DoS, not Important Manual review required: NO Summary: `amdgpu_userq_wait_ioctl accepted unbounded user supplied handle counts, allowing a local DRM device user to request excessive kernel allocations and potentially trigger OOM based denial of service.` ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-43398 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43398 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-43398 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-770;**CWE-400;CWE-789;BEST CVSS score: '5.5';DESCR 'amdgpu_userq_wait_ioctl accepted user controlled handle counters without an upper bound. Very large num_syncobj_handles, num_bo_write_handles, or num_bo_read_handles values can drive large kernel allocations in the wait ioctl path and may trigger OOM on the host. For the CVSS the PR:L value is used because reliable triggering requires a local process with access to the AMDGPU DRM device, but it does not normally require full root privileges. The issue is not network reachable and is exposed through a local device ioctl. Impact is denial of service through memory exhaustion. No concrete UAF, OOB write, arbitrary write, or information leak primitive is indicated by the patch context, so confidentiality and integrity remain unaffected.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Borderline local DoS, not Important (with actual score 3) MAYBE SIMPLEFIX HARDWARE INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 3 * Final recommended bucket: **Ordinary Moderate / Borderline local DoS, not Important**:: ## 2. Signal breakdown Triggered signals: * Local unprivileged trigger: +1 A local process with access to the AMDGPU DRM device can call the wait ioctl. This usually does not require full root privileges on systems exposing render or video device nodes to users. * Availability impact realistic: +1 Huge user supplied handle counts can drive large kernel allocations through memdup_user and related wait ioctl handling, potentially causing OOM. Paranoid-only signal: * Reliable kernel crash / strong DoS: +1 Counted only in the paranoid score because the commit explicitly says huge values can lead to OOM. This is still resource exhaustion, not memory corruption. Not counted: * No generic memory corruption. The patch only adds upper bound validation before allocation. * No UAF, double free, OOB write, arbitrary write, type confusion, or information leak is shown. * No privilege escalation plausibility beyond generic OOM impact. * No high-control API bonus. DRM ioctls expose kernel objects, but this patch does not show attacker control over object lifetime, callbacks, refcounts, DMA ownership, or memory layout relevant to exploitation. * No remote reachability. ## 3. Reachability analysis The bug is reachable locally through `amdgpu_userq_wait_ioctl()` when AMDGPU user queues are enabled and the caller has access to the DRM device. In typical desktop or GPU compute deployments, such access may be available to non-root users through `render` or `video` group permissions. Containers can matter if GPU device nodes are passed through, but this is still a local device-interface attack rather than a network attack. The path is hardware and configuration dependent because it requires AMDGPU and userq support. Exploitation conditions are realistic for local DoS if an untrusted user can access the relevant device node, but the demonstrated primitive is only excessive allocation leading to OOM. ## 4. Severity interpretation This behaves like an ordinary Moderate local resource exhaustion issue, not an Important-class kernel vulnerability. The realistic impact is local denial of service via memory exhaustion. Theoretical exploitation beyond DoS is not supported by the patch because there is no concrete memory corruption, stale pointer, object confusion, controlled overwrite, or disclosure primitive. ## 5. One-sentence report phrase `amdgpu_userq_wait_ioctl accepted unbounded user supplied handle counts, allowing a local DRM device user to request excessive kernel allocations and potentially trigger OOM based denial of service.` ## 6. Manual review recommendation NO MANUAL CHECK NEEDED Reason: this is a local resource exhaustion validation fix with no evidence of memory corruption, privilege escalation, information disclosure, or network reachability. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/amdgpu: add upper bound check on user inputs in wait ioctl Commit: b1d10508da559da2e0ca9cca6505094a7df948e1 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b1d10508da559da2e0ca9cca6505094a7df948e1 Commit description: Huge input values in amdgpu_userq_wait_ioctl can lead to a OOM and could be exploited. So check these input value against AMDGPU_USERQ_MAX_HANDLES which is big enough value for genuine use cases and could potentially avoid OOM. v2: squash in Srini's fix Signed-off-by: Sunil Khatri Reviewed-by: Christian König Signed-off-by: Alex Deucher (cherry picked from commit fcec012 ) Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman Changed files: drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.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=b1d10508da559da2e0ca9cca6505094a7df948e1 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-43398 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43398 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: Not available 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).