From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-93176][MODERATE 7.0] drm/amd/display: Fix dangling pointer in plane reset function [ Upstream Date: Thu, 17 Sep 2026 22:10:20 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-93176 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 80c0f51aced43d6eaf72f95a2833b0a77cf7880d List-Id: CVE: CVE-2026-93176 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: drm/amd/display: Fix dangling pointer in plane reset function [ Upstream Commit: 80c0f51aced43d6eaf72f95a2833b0a77cf7880d Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=80c0f51aced43d6eaf72f95a2833b0a77cf7880d Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93176 Analysis date: Thu, 17 Sep 2026 22:10:20 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review Manual review required: YES Summary: A dangling pointer in the AMDGPU DRM plane reset path can leave `plane->state` referencing freed memory after allocation failure, creating a local UAF risk with likely kernel crash impact and unresolved exploitation potential. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-93176 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93176 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 7.0 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-2026-93176 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-93176 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:H/I:H/A:H';*CWE-416;CWE-825;CWE-459;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A use after free risk exists in the AMDGPU display plane reset path because amdgpu_dm_plane_drm_plane_reset freed the old drm plane state before allocating the replacement state. If kzalloc failed, the function returned while plane state still pointed to freed memory, leaving a dangling pointer that later DRM atomic or display code could dereference or free again. For the CVSS the PR:L is used for the paranoid score because a local user with access to DRM or KMS control paths may be able to influence modeset, display reset, hotplug, resume, or recovery behavior without full administrator privileges. The issue is not network reachable. Impact is at least local denial of service through a kernel crash. In the worst defensible case it may allow confidentiality and integrity impact because the bug is a real kernel use after free condition rather than a pure NULL dereference or resource leak.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) SKIP CVE-2026-93176 UNKNOWN SKIP No affected files built, so skip this CVE NO - - unknown MAYBE UAF HARDWARE KPANIC - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 PrimitiveClass=CLASS_B RealUAF=YES HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=NO ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO ## 1. ActionableScore * Raw conservative score: 3 * Conservative score: 4 * Raw paranoid score: 4 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**:: Conservative floor applied: 3 -> 4 because a real dangling pointer / UAF is established and host-admin-equivalent privilege is not positively established. Paranoid floor applied: 4 -> 5 because the stale pointer remains installed as the live `plane->state` of an active DRM object, so later DRM atomic/display paths may consume freed structured state rather than only faulting in a narrow destructor. ## 2. Signal breakdown Conservative signals: * +2 Real UAF / lifetime violation. `plane->state` is destroyed before allocating replacement state. If allocation fails, the pointer remains dangling. * +1 Reliable kernel crash / strong DoS. Later use or destruction of the stale DRM plane state can plausibly fault or double-use freed memory. * +0 Local unprivileged trigger not awarded. Complete below-host-admin trigger path is not established from the supplied patch. * +0 Remote reachability not awarded. This is a local DRM/KMS display path. * +0 Controlled reclaim not demonstrated. * +0 Arbitrary write not demonstrated. * +0 Concrete repeated release/refcount signal not awarded. The patch establishes a dangling pointer, but does not show a concrete second `put` or refcount mutation on the same exact reference. * +0 Extra availability not awarded. The crash/DoS effect is already counted once. Paranoid additional signal: * +1 Weak active structured stale-object concern. The stale object is a `dm_plane_state` / `drm_plane_state` associated with a live `drm_plane`, and later DRM atomic/display processing may interpret freed memory as valid structured state. This is not enough for CLASS_A, but it is enough to avoid automatic downgrade. Non-awarded material signals: * Strong LPE leverage +2 not awarded because controlled reclaim, attacker-shaped replacement contents, callback control, or directed kernel write is not shown. * Structured stale-object exploitation leverage is not separately awarded beyond the paranoid weak concern because exact post-free field consumption is not visible. * Confidentiality and integrity bonuses are not awarded because no disclosure path, protected object modification, arbitrary write, or demonstrated privilege escalation is established. * Race/timing penalty not applied. This is an ordered allocation-failure lifetime bug, not a narrow race. * Hardware rarity penalty not applied. AMDGPU/display is hardware-specific, but not rare or physical-only in the required sense. Repeated release/refcount checklist: * First release can end lifetime: yes, `atomic_destroy_state()` can free the old plane state. * Exact same reference survives: yes, `plane->state` is not updated on allocation failure. * Second operation is a real lifetime/refcount mutation: not established by the supplied diff. * Concrete repeated release/refcount +1 awarded: no. * Paranoid repeated-refcount +1 awarded: no. * FLOOR 5 applied: yes, only for paranoid scoring due to live active structured state. ## 3. Reachability analysis The likely trigger requires a local actor able to reach the AMDGPU DRM/KMS plane reset path and cause or coincide with `kzalloc_obj()` failure. The supplied patch does not prove that an ordinary unprivileged user can directly invoke the complete vulnerable operation. For DRM/KMS roles: * Ordinary logged-in user: possible indirect influence through graphics workloads or compositor-mediated display operations, but complete reachability is not proven here. * DRM master / compositor / display server: more plausible trigger role because these actors manage modeset and display state. * Delegated graphics/display service: plausible in desktop or containerized graphics deployments, but exact privilege boundary is deployment-specific. * Host administrator: may trigger display reset paths, but host-admin-equivalent privilege is not positively established as required. HostAdminRequired is therefore UNKNOWN, not YES. NamespaceScopedPrivilege is NO because no namespace-scoped capability path is established or relevant from the supplied evidence. No network trigger is present. No prior host setup beyond having AMDGPU DRM/display functionality is established. No special rare hardware penalty is applied. The main practical constraint is allocation failure at the vulnerable point. ## 4. Primitive and severity interpretation The exact primitive is a dangling pointer / use-after-free candidate in `amdgpu_dm_plane_drm_plane_reset()`. The old plane state is freed first, then allocation of the replacement state may fail, leaving `plane->state` pointing to freed memory. This is an active structured object case, not fixed stale storage. The stale pointer remains attached to a live DRM plane object and may later be consumed by DRM atomic or AMDGPU display code. This is not merely a NULL dereference and not a pure resource leak. It is also not proven CLASS_A because the patch does not establish controlled reclaim, arbitrary read/write, function-pointer control, or demonstrated LPE. PrimitiveClass is CLASS_B. Demonstrated consequence is local kernel memory lifetime corruption with likely crash/DoS. Speculative consequence is privilege escalation if freed plane-state memory can be reclaimed and later interpreted in a useful way, but that is not established by this patch alone. ImportantCandidate is YES because the issue is a real kernel UAF in live DRM state with unresolved exploitation leverage. AutoDowngradeAllowed is NO because automatic closure would discard a meaningful active-object lifetime primitive that still needs manual review. Likely operational severity is Actionable Moderate, with Strong Important review justified if downstream analysis confirms below-host-admin reachability and useful post-free state consumption. ## 5. One-sentence report phrase A dangling pointer in the AMDGPU DRM plane reset path can leave `plane->state` referencing freed memory after allocation failure, creating a local UAF risk with likely kernel crash impact and unresolved exploitation potential. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: real kernel UAF in active DRM display state, host-admin requirement unresolved, and later structured-state consumption may matter for exploitation beyond crash. ## 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/amd/display: Fix dangling pointer in plane reset function [ Upstream Commit: 80c0f51aced43d6eaf72f95a2833b0a77cf7880d Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=80c0f51aced43d6eaf72f95a2833b0a77cf7880d Changed files: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.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=80c0f51aced43d6eaf72f95a2833b0a77cf7880d ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-93176 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93176 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:L/UI:N/S:U/C:L/I:L/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: 4 Paranoid ActionableScore: 5 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: YES Published priority for this report (same as in Subject): MODERATE 7.0 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).