From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-89827][MODERATE REGULAR] drm/amdgpu: avoid force-completing uninitialized UVD rings Date: Wed, 16 Sep 2026 12:29:40 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-89827 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: 2 X-AL-KERNEL-ActionableScore-Lower: 1 X-AL-KERNEL-Commit: 967a179463d3227dfaf9200fd654c1f5a26a11e8 List-Id: CVE: CVE-2026-89827 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: drm/amdgpu: avoid force-completing uninitialized UVD rings Commit: 967a179463d3227dfaf9200fd654c1f5a26a11e8 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=967a179463d3227dfaf9200fd654c1f5a26a11e8 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89827 Analysis date: Wed, 16 Sep 2026 12:29:40 -0400 ActionableScore: 2 ActionableScore lower bound: 1 Actionable bucket: Ordinary Moderate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-89827 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89827 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-2026-89827 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-89827 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-908;CWE-665;CWE-754;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'The AMDGPU UVD resume path can call amdgpu_fence_driver_force_completion for a decode ring whose fence driver was never initialized for an SR-IOV VF. Using this incomplete ring state can violate fence driver assumptions and may cause a warning or a host kernel crash during GPU resume or recovery. For the CVSS the PR:L value is used for the paranoid score because a restricted tenant or process with access to an assigned VF may be able to influence GPU workloads and recovery without having full host administrative privileges. Reliable triggering still depends on an SR-IOV VF configuration and on reaching the UVD resume or reset path, so AC:H is appropriate. The issue is not directly network reachable. The demonstrated impact is denial of service against the host, while the available code does not establish a UAF, information leak, or write primitive that would justify confidentiality or integrity impact.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) SKIP CVE-2026-89827 UNKNOWN SKIP No affected files built, so skip this CVE NO - - unknown MAYBE INIT SIMPLEFIX HARDWARE - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ActionableScoreLower=1 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 1 * Conservative score: 1 * Raw paranoid score: 2 * Paranoid score: 2 * No floor or cap was applied. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown Conservative signals: * +1 Weak or indirect corruption candidate. `amdgpu_uvd_resume()` passes a UVD ring with an uninitialized fence driver to a helper that expects initialized fence state. * No crash point was awarded conservatively. The patch establishes invalid-state processing but does not document an observed Oops, panic, or host crash. Paranoid signals: * +1 Weak or indirect corruption candidate for the same uninitialized fence-driver use. * +1 Realistic kernel crash or strong DoS. Calling fence completion code with uninitialized synchronization and fence state can defensibly cause a host kernel fault during resume or recovery, although that consequence is not demonstrated in the commit. Not awarded: * No UAF or post-lifetime access is established. * No repeated release, refcount mutation, double free, controlled reclaim, arbitrary write, information disclosure, or callback control is established. * No confidentiality or integrity point was awarded. * No remote-reachability point was awarded. * No guest-to-host corruption point was awarded because the evidence does not show that a guest controls a useful host-memory primitive. * No local-unprivileged point was awarded because the complete below-host-admin trigger is unresolved. * No hardware rarity penalty was applied. SR-IOV UVD is specialized, but the evidence does not establish rare physical hardware or physical access. * No extra availability point was awarded beyond the paranoid crash point. Repeated-release checks: * First lifetime-ending release: absent. * Exact reference surviving a release: absent. * Second lifetime or refcount mutation: absent. * Concrete repeated release or refcount +1: not awarded. * Paranoid repeated-refcount leverage +1: not awarded. * FLOOR 5: not applicable. 3. Reachability analysis The affected configuration uses an AMDGPU SR-IOV virtual function for which the UVD decode ring is intentionally not initialized. A host administrator normally provisions SR-IOV and assigns a VF, so prior privileged setup exists. That does not prove that host administration is required for the later vulnerable resume or recovery trigger. A guest, tenant process, or delegated graphics service may submit workloads through an assigned VF, but the supplied evidence does not show whether such an actor can independently force the relevant UVD resume or GPU recovery path. The complete trigger may instead require host-controlled reset, suspend, resume, or device recovery. Therefore `HostAdminRequired` remains `UNKNOWN`. No user-namespace or namespace-scoped capability path is established. An ordinary logged-in user, DRM master, compositor, or display service is not shown to reach the complete SR-IOV VF recovery operation. This is not a timing race, and no network trigger is established. 4. Primitive and severity interpretation The exact primitive is an operation on an incompletely initialized UVD ring and fence-driver state. This is invalid active driver state rather than stale storage, UAF, double release, or demonstrated memory corruption. The patch-supported consequence is that force completion is incorrectly attempted for a fence driver that was never initialized. A warning, invalid dereference, synchronization failure, or host crash is technically plausible. The evidence does not establish that attacker-controlled data are consumed as pointers, callbacks, indices, or writable destinations. This is `CLASS_C` because the demonstrated mechanics are invalid-state and potential DoS behavior without an independently useful corruption primitive. Stronger outcomes such as host privilege escalation or guest escape would require additional evidence of controlled host-memory corruption. `ImportantCandidate=NO` because neither Class A nor meaningful unresolved Class B leverage is present. `AutoDowngradeAllowed=YES` because no lifetime, ownership, authorization, or controlled-corruption primitive would be lost by treating this as an ordinary Moderate issue. Operational severity is likely Low to Moderate and depends on whether a VF tenant can induce the affected recovery path. 5. One-sentence report phrase An AMDGPU SR-IOV VF resume can invoke fence completion on an uninitialized UVD decode ring, potentially causing invalid host driver state or a kernel crash, but no UAF, controlled corruption, or guest-to-host privilege primitive is established. 6. Manual review recommendation MANUAL CHECK RECOMMENDED Confirm whether an assigned VF guest or below-host-admin process can independently trigger the affected resume or recovery path, and inspect `amdgpu_fence_driver_force_completion()` for the exact consequence of receiving an uninitialized fence driver. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/amdgpu: avoid force-completing uninitialized UVD rings Commit: 967a179463d3227dfaf9200fd654c1f5a26a11e8 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=967a179463d3227dfaf9200fd654c1f5a26a11e8 Commit description: uvd_v7_0_sw_init() does not initialize the UVD decode ring for an SR-IOV VF. However, amdgpu_uvd_resume() unconditionally force-completes the decode ring when restoring its fence sequence. Skip fence completion when the fence driver is not initialized. Fixes: 0a33b11 ("drm/amdgpu: mark force completed fences with -ECANCELED") Cc: stable@vger.kernel.org Signed-off-by: Bob Zhou Acked-by: Leo Liu Acked-by: Frank Min Signed-off-by: Alex Deucher Signed-off-by: Greg Kroah-Hartman Changed files: drivers/gpu/drm/amd/amdgpu/amdgpu_uvd.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=967a179463d3227dfaf9200fd654c1f5a26a11e8 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-89827 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89827 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:N/I:N/A:H The Best / paranoid CVSS score: 4.7 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: 1 Paranoid ActionableScore: 2 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).