From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-89814][MODERATE REGULAR] drm/amdgpu: clamp the isolation index for rings outside a partition Date: Wed, 16 Sep 2026 08:29:54 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-89814 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: 964de255497ffd7cb8a86e405b8ac6d927e7e177 List-Id: CVE: CVE-2026-89814 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: drm/amdgpu: clamp the isolation index for rings outside a partition Commit: 964de255497ffd7cb8a86e405b8ac6d927e7e177 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=964de255497ffd7cb8a86e405b8ac6d927e7e177 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89814 Analysis date: Wed, 16 Sep 2026 08:29:54 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-89814 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89814 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-2026-89814 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-89814 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-129;CWE-125;*CWE-787;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'An invalid isolation array index can occur when an AMDGPU ring is not assigned to an XCP partition and ring xcp_id retains AMDGPU_XCP_NO_PARTITION. This value is approximately zero inverted and was used directly to index adev isolation during SDMA submission and VM flush processing, producing an out of bounds pointer and triggering UBSAN. In the isolation enforcement path the pointer was formed before the ring type check. In the VM flush path the invalid pointer can reach later isolation state accesses, so the impact may extend beyond a diagnostic warning to a kernel crash or memory corruption. For the CVSS the PR:L value is selected because a local unprivileged process may submit GPU workloads when it has access to the AMDGPU render node. The issue is not directly network reachable. The base impact is denial of service. The paranoid impact uses C:H I:H A:H because an out of bounds kernel pointer used by later VM flush logic may provide a memory corruption path, although reliable privilege escalation is not demonstrated and requires manual source review.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) SKIP CVE-2026-89814 UNKNOWN SKIP No affected files built, so skip this CVE NO - - unknown MAYBE KASAN OOB SIMPLEFIX HARDWARE MEMORY DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 2 * Conservative score: 2 * Raw paranoid score: 3 * Paranoid score: 3 * No floor or cap was applied. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown Conservative signals: * +1 Local unprivileged trigger. A process with access to the AMDGPU render node can normally submit SDMA workloads without host-admin-equivalent privilege. * +1 Weak or indirect corruption candidate. `AMDGPU_XCP_NO_PARTITION`, represented by an all-ones sentinel, is used as an unchecked index and creates an out-of-bounds `struct amdgpu_isolation` pointer. * +1 Broad and realistically exercised exposure. AMDGPU is broadly deployed, and SDMA submission is an ordinary GPU data-plane operation on affected hardware. * -1 No attacker-controlled payload or target. The invalid index is a fixed sentinel associated with the selected ring. The supplied evidence does not show that the attacker can direct the pointer toward a chosen kernel object. * Total: 1 + 1 + 1 - 1 = 2. Paranoid-only signal: * +1 Plausible strong DoS. The VM-flush path creates the invalid pointer without the early ring-type return present in the isolation-enforcement path. A later dereference can plausibly cause a kernel fault, although the supplied context directly demonstrates only an out-of-bounds UBSAN report. * Total: 2 + 1 = 3. Important signals not awarded: * No strong OOB write was established. * No attacker-selected destination or data was established. * No disclosure path was established from an OOB read. * No controlled replacement, reclaim, type confusion, callback influence, or arbitrary read/write was demonstrated. * No UAF, repeated release, refcount mutation, or lifetime violation exists. * No confidentiality or integrity points were awarded merely because the previous CVSS analysis used `C:H/I:H`. * No extra availability point was awarded for the same potential kernel fault. * Remote reachability was not established. * Hardware rarity penalty was not applied because AMD GPUs are not inherently rare, although only affected AMDGPU devices are exposed. 3. Reachability analysis An ordinary local process can potentially reach the path by opening an accessible AMDGPU render node and submitting work that uses an SDMA ring outside an XCP partition. DRM master, KMS control, compositor status, and host-administrator privilege are not normally required for render-node command submission. The complete trigger remains dependent on an affected AMD GPU, the AMDGPU driver, a ring retaining `AMDGPU_XCP_NO_PARTITION`, and the relevant SDMA or VM-flush path. These are device and driver prerequisites, not evidence of physical-only or rare hardware. No capability namespace governs ordinary render-node access. Access is based on the device node and its file permissions or an already supplied DRM file descriptor. Therefore namespace-scoped privilege is not part of the demonstrated trigger. There is no race or narrow timing requirement. The invalid index follows directly from the persistent sentinel value. No direct network trigger is present. 4. Primitive and severity interpretation The exact primitive is creation of an out-of-bounds pointer by indexing `adev->isolation[]` with the fixed `AMDGPU_XCP_NO_PARTITION` sentinel. In `amdgpu_device_enforce_isolation()`, the old code formed the invalid pointer before checking whether the ring type made isolation relevant. For an SDMA ring, the function can return without consuming the pointer, so this instance can be limited to undefined pointer arithmetic and an UBSAN report. In `amdgpu_vm_flush()`, the pointer is created on the active VM-flush path. Later use of `isolation` is plausible from normal function semantics, but the supplied context does not show the subsequent accesses or prove whether they are reads, writes, or only comparisons. Consequently, a concrete exploitable OOB write cannot be assigned. This is not stale storage, UAF, or a lifetime-management defect. It is an invalid-index and invalid-pointer issue whose established symptom is UBSAN detection and whose plausible practical consequence is a kernel fault or GPU workload failure. It is therefore CLASS_C rather than CLASS_A or CLASS_B. ImportantCandidate is NO because no independently useful corruption primitive beyond the possible crash has been established. AutoDowngradeAllowed is YES because there is no unresolved controlled corruption, ownership violation, lifetime primitive, or security-boundary bypass. Manual review remains recommended to inspect every later `isolation` dereference in `amdgpu_vm_flush()` and determine whether any write occurs before treating the issue as conclusively crash-only. The likely operational severity is ordinary Moderate or Low-like, with a borderline score retained because the vulnerable path is locally reachable below host-admin privilege and executes in the kernel. 5. One-sentence report phrase A local process with AMDGPU render-node access can submit SDMA work that uses the no-partition sentinel as an out-of-bounds isolation-array index, triggering UBSAN and potentially causing a kernel fault, but no controlled write or privilege-escalation primitive is established. 6. Manual review recommendation MANUAL CHECK RECOMMENDED Review the complete `amdgpu_vm_flush()` function and all accesses through `isolation` to determine whether the invalid pointer can be dereferenced for a write or only produces a warning or fault. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/amdgpu: clamp the isolation index for rings outside a partition Commit: 964de255497ffd7cb8a86e405b8ac6d927e7e177 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=964de255497ffd7cb8a86e405b8ac6d927e7e177 Commit description: adev->isolation[] has one slot per partition, but a ring that is not assigned to one keeps AMDGPU_XCP_NO_PARTITION, which is ~0, so indexing the array with it is out of bounds. SDMA submissions hit this on both the isolation enforcement and the VM flush path and trip UBSAN. Fall back to the first slot the way the cleaner shader path already does, and stop taking the address before the ring type check that makes it relevant. Cc: stable@vger.kernel.org Signed-off-by: Xiang Liu Reviewed-by: Hawking Zhang Signed-off-by: Alex Deucher Signed-off-by: Greg Kroah-Hartman Changed files: drivers/gpu/drm/amd/amdgpu/amdgpu_device.c drivers/gpu/drm/amd/amdgpu/amdgpu_vm.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=964de255497ffd7cb8a86e405b8ac6d927e7e177 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-89814 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89814 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:L/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:H/I:H/A:H The Best / paranoid CVSS score: 7 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).