From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-43400][MODERATE REGULAR] drm/amdgpu: add upper bound check on user inputs in signal ioctl Date: Sat, 01 Aug 2026 12:12:08 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-43400 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: 6fff5204d8aa26b1be50b6427f833bd3e8899c4f List-Id: CVE: CVE-2026-43400 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: drm/amdgpu: add upper bound check on user inputs in signal ioctl Commit: 6fff5204d8aa26b1be50b6427f833bd3e8899c4f Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6fff5204d8aa26b1be50b6427f833bd3e8899c4f Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43400 Analysis date: Sat, 01 Aug 2026 12:12:08 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-43400 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43400 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-2026-43400 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-400;CWE-789;CWE-770;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'amdgpu_userq_signal_ioctl accepted user supplied handle counts without an upper bound and used those counts to size memdup_user allocations for syncobj and BO handle arrays. A local process with access to the AMDGPU DRM device could pass very large counts and force excessive kernel memory allocation, causing memory pressure or an out of memory condition. For the CVSS the PR:L is used because reliable triggering requires local code execution with access to the DRM device node, but not full administrative privileges. The issue is not network reachable and does not provide a concrete memory corruption primitive. Impact is denial of service through resource exhaustion, with no supported confidentiality or integrity impact from the patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 3) MAYBE SIMPLEFIX HARDWARE MEMORY DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 1. ActionableScore * Conservative score: 2 * Paranoid score: 3 * Final recommended bucket: **Ordinary Moderate / Low-like**:: 2. Signal breakdown * Local unprivileged trigger: +1. A local process with access to the AMDGPU DRM device node can call amdgpu_userq_signal_ioctl. This is PR:L rather than PR:H in typical desktop or GPU compute setups where render device access may be delegated. * Reliable kernel crash / strong DoS: +1. The commit explicitly says huge input values can lead to OOM and could be exploited. * Availability impact realistic: +1 only for paranoid scoring. If repeated or large allocations can reliably pressure system memory, the impact can become system-wide OOM. This is not counted in the conservative score to avoid double-counting the DoS signal. * No generic memory corruption: +0. The patch only adds upper-bound validation before memdup_user allocations. It does not show UAF, OOB write, double free, type confusion, refcount misuse, or arbitrary write. * No confidentiality or integrity impact: +0. The visible primitive is resource exhaustion only. * No high-control device API bonus: +0. This is a GPU ioctl, but the patch does not show attacker influence over object lifetime, callbacks, DMA mappings, page ownership, or allocator reuse beyond oversized allocation counts. 3. Reachability analysis A local user or process with access to the AMDGPU DRM node can potentially trigger the path if amdgpu_userq is enabled. This is not network reachable. Containers or delegated GPU access may make the bug reachable by less trusted workloads, but the requirement remains local device access. The realistic exploit condition is memory pressure or OOM through oversized handle-count allocations, not memory corruption or privilege escalation. 4. Severity interpretation This behaves like an ordinary Moderate or Low-like resource-exhaustion issue. Theoretical impact is local DoS via OOM. There is no evidence of a stronger primitive such as controlled overwrite, stale pointer reuse, page-cache corruption, or privilege escalation. Paranoid scoring reaches 3 because system-wide OOM is plausible, but this should not be treated as an Important-class kernel vulnerability. 5. One-sentence report phrase amdgpu_userq_signal_ioctl lacked upper bounds on user supplied handle counts, allowing a local process with AMDGPU DRM access to request excessive kernel allocations and potentially cause OOM based denial of service. 6. Manual review recommendation NO MANUAL CHECK NEEDED. This is a validation-only resource exhaustion fix with no concrete memory corruption, confidentiality, integrity, or privilege escalation primitive shown by the patch. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/amdgpu: add upper bound check on user inputs in signal ioctl Commit: 6fff5204d8aa26b1be50b6427f833bd3e8899c4f Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6fff5204d8aa26b1be50b6427f833bd3e8899c4f Commit description: Huge input values in amdgpu_userq_signal_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. Signed-off-by: Sunil Khatri Reviewed-by: Christian König Signed-off-by: Alex Deucher (cherry picked from commit be267e1 ) 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=6fff5204d8aa26b1be50b6427f833bd3e8899c4f ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-43400 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43400 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:L 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).