From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-46311][MODERATE 7.0] drm/amdgpu/userq: fix access to stale wptr mapping Date: Sat, 01 Aug 2026 09:21:35 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-46311 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: 6 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 336a9186f3a4b65bbd865d93936605ac8a1a3991 List-Id: CVE: CVE-2026-46311 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: drm/amdgpu/userq: fix access to stale wptr mapping Commit: 336a9186f3a4b65bbd865d93936605ac8a1a3991 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=336a9186f3a4b65bbd865d93936605ac8a1a3991 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46311 Analysis date: Sat, 01 Aug 2026 09:21:35 -0400 ActionableScore: 6 ActionableScore lower bound: 4 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum**:: Treat as Actionable Moderate for triage. Escalate toward Important if manual review confirms stale BO reuse can affect another process, privileged GPU memory, command submission state, or host memory mappings. Manual review required: YES Summary: A local AMDGPU user can race user queue creation with unmapping and remapping the wptr BO at the same GPU virtual address, causing stale mapping or unintended BO use in a GART pinned queue object and requiring manual review for possible DoS or limited privilege impact. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46311 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46311 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-2026-46311 MODERATE 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-362;*CWE-416;CWE-367;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'An access race in amdgpu usermode queue creation can leave the wptr mapping stale because the VM page directory object and the selected wptr BO were not locked together while the mapping was looked up and used. A local GPU user can race queue creation with unmapping the wptr object and mapping another BO at the same GPU virtual address, causing the queue to pin or use an unintended or stale BO. For the CVSS the PR:L is used because practical triggering requires local access to the DRM render or GPU device interface, not full administrator privileges. The issue is not network reachable and requires local code execution on a system with affected AMDGPU user queues enabled. Impact is at least local denial of service and in worst case may allow confidentiality or integrity impact because the bug is a race on GPU VM mapping objects with a plausible stale pointer or wrong object use primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5) MAYBE INIT HARDWARE KPANIC MEMORY - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=6 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 6 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: Treat as Actionable Moderate for triage. Escalate toward Important if manual review confirms stale BO reuse can affect another process, privileged GPU memory, command submission state, or host memory mappings. ## 2. Signal breakdown Conservative signals: * Local unprivileged trigger: +1. A local user with access to the AMDGPU DRM render or GPU device interface can plausibly create queues and manipulate BO mappings. * Memory corruption, weak/indirect corruption candidate: +1. The bug is stale mapping or wrong BO selection, not a proven arbitrary write or controlled UAF reclaim. * Real lifetime or stale pointer concern: +1. The commit explicitly describes unmapping the wptr object while queue creation is in progress. * Privileged device or DMA-adjacent object management path: +1. The affected code pins a BO and maps it through GART for GPU queue operation. * Hard or unreliable race: -1. Exploitation requires winning a race between queue creation and unmap/remap at the same GPU virtual address. * Integrity impact plausible: +1. Wrong BO selection may let the queue use an unintended object, but the exact corruption or cross-object effect is not demonstrated. Conservative total: 4. Paranoid additional signals: * Weak LPE concern: +1. The race can cause an unintended BO to be pinned and used as the queue write pointer object, which is a plausible object-selection primitive in a privileged GPU VM path. * Confidentiality impact plausible: +1. If the stale or substituted BO can belong to another sensitive mapping context, limited data exposure is technically plausible, though not proven. Paranoid total: 6. Not awarded: * Remote reachable: +0. No network path. * Strong LPE plausibility: +0. No demonstrated reclaim, arbitrary write, callback control, or reliable type confusion. * Strong memory corruption primitive: +0. The patch shows stale mapping and wrong BO use, but not a controlled kernel heap overwrite. * Reliable kernel crash: +0. The commit frames this as a security issue, but does not provide a crash trace. Call-site confidence: medium. The changed function and relevant object lifetime operations are visible, but broader ioctl entry points and queue submission consequences are not included. ## 3. Reachability analysis The likely attacker is a local user or local process with access to AMDGPU usermode queue creation and GPU memory mapping interfaces. This usually does not require full host root if render nodes or GPU device access are delegated to users. Namespaces and containers may matter. If a container or sandbox exposes the GPU render node, the attacker may be reduced-privilege rather than fully privileged. This supports PR:L style reasoning rather than PR:H. The path is not remotely reachable. It requires affected AMDGPU hardware and user queue support. The realistic trigger requires racing queue creation with unmapping and remapping another BO at the same GPU virtual address. ## 4. Severity interpretation This is stronger than an ordinary Moderate correctness bug because the patch fixes a security-relevant stale mapping race in GPU VM object selection. The realistic evidence supports a local race with possible wrong BO use, stale mapping access, and DoS or limited object confusion. The theoretical worst case includes confidentiality or integrity impact if the wrong BO can be selected in a way that crosses object ownership or queue state boundaries. However, the patch does not demonstrate arbitrary write, controlled kernel memory reuse, or a reliable privilege escalation chain. Therefore the conservative result is borderline manual-review severity, while the paranoid result is Actionable Moderate. ## 5. One-sentence report phrase A local AMDGPU user can race user queue creation with unmapping and remapping the wptr BO at the same GPU virtual address, causing stale mapping or unintended BO use in a GART pinned queue object and requiring manual review for possible DoS or limited privilege impact. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Manual review is required because the commit explicitly calls this a security issue and the primitive is a race on GPU VM mapping lifetime and object identity. The visible patch does not prove full LPE, but it is strong enough to avoid auto-close. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/amdgpu/userq: fix access to stale wptr mapping Commit: 336a9186f3a4b65bbd865d93936605ac8a1a3991 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=336a9186f3a4b65bbd865d93936605ac8a1a3991 Commit description: Use drm_exec to take both locks i.e vm root bo and wptr_obj bo to access the mapping data properly. This fixes the security issue of unmap the wptr_obj while a queue creation is in progress and passing other bo at same address. Signed-off-by: Sunil Khatri Reviewed-by: Christian König Signed-off-by: Alex Deucher (cherry picked from commit 1fc6c8a ) Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman Changed files: drivers/gpu/drm/amd/amdgpu/mes_userqueue.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=336a9186f3a4b65bbd865d93936605ac8a1a3991 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46311 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46311 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: 6 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).