From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-46276][LOW] drm/amdgpu: fix zero-size GDS range init on RDNA4 Date: Sat, 01 Aug 2026 09:27:47 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-46276 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 1 X-AL-KERNEL-ActionableScore-Lower: 0 X-AL-KERNEL-Commit: 1f5d33e7b0a9a2a140f46e22fb52eede323c5946 List-Id: CVE: CVE-2026-46276 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: drm/amdgpu: fix zero-size GDS range init on RDNA4 Commit: 1f5d33e7b0a9a2a140f46e22fb52eede323c5946 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1f5d33e7b0a9a2a140f46e22fb52eede323c5946 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46276 Analysis date: Sat, 01 Aug 2026 09:27:47 -0400 ActionableScore: 1 ActionableScore lower bound: 0 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-2026-46276 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46276 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: LOW 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-2026-46276 LOW CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';CWE-617;CWE-754;*CWE-20;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.4';DESCR 'amdgpu TTM initialization can pass a zero size on chip resource range to drm_mm_init on RDNA4 hardware where GDS GWS and OA resources are absent. With CONFIG_DRM_DEBUG_MM enabled this reaches DRM_MM_BUG_ON and can crash the kernel during amdgpu module load or device probe. For the CVSS the PR:H is used because reliable triggering requires administrative control over driver loading or device probing on a host with the affected AMD GPU and debug MM configuration. The issue is not network reachable and does not provide a visible memory corruption primitive. Impact is denial of service through a local kernel crash only.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) SKIP CVE-2026-46276 SKIP No affected files built, so skip this CVE NO - - unknown MAYBE DANGER HARDWARE DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 ActionableScoreLower=0 1. ActionableScore * Conservative score: 0 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate / Low-like**:: 2. Signal breakdown * Reliable kernel crash / strong DoS: +1. The commit describes a kernel crash during amdgpu modprobe when `CONFIG_DRM_DEBUG_MM` is enabled and RDNA4 zero-size GDS/GWS/OA resources reach `DRM_MM_BUG_ON`. * Availability impact realistic: +0. The crash is real, but it is already counted as DoS and is limited to a specific debug configuration and hardware path. * Requires admin/root/CAP in typical deployments: -2. Reliable triggering requires loading/probing the amdgpu driver or controlling the affected device initialization path. * Legacy / non-default execution mode: -1. `CONFIG_DRM_DEBUG_MM` is explicitly described as rarely enabled. * Physical-only or rare hardware-only condition: -2. The issue depends on RDNA4 hardware such as RX 9070 XT and absent on-chip GDS/GWS/OA resources. * Generic memory corruption: +0. The patch shows a zero-size range reaching an assertion, not UAF, OOB write, double free, type confusion, or attacker-controlled corruption. * Privilege escalation plausible: +0. No LPE primitive is visible. * Confidentiality impact plausible: +0. * Integrity impact plausible: +0. 3. Reachability analysis The bug is triggered during amdgpu module load or device probe on affected RDNA4 hardware with `CONFIG_DRM_DEBUG_MM` enabled. In normal deployments, this requires administrator-level control over driver loading or hardware probing, so local unprivileged users are not a realistic trigger. Namespaces or containers do not materially lower the privilege requirement unless they somehow allow delegated host GPU driver reprobe control, which is not typical. The path is not network reachable and the relevant debug configuration is uncommon. 4. Severity interpretation This behaves like a local privileged debug-configuration DoS, not an actionable memory corruption issue. The theoretical impact is a kernel crash through an assertion in `drm_mm_init(mm, 0, 0)`. Realistic exploitation evidence does not show arbitrary memory corruption, information disclosure, integrity impact, or privilege escalation. This should remain in the ordinary Moderate or Low-like handling bucket. 5. One-sentence report phrase A zero-size RDNA4 GDS/GWS/OA resource range can reach `DRM_MM_BUG_ON` during amdgpu initialization and crash debug kernels, but triggering requires affected AMD hardware, `CONFIG_DRM_DEBUG_MM`, and privileged driver load or probe control. 6. Manual review recommendation NO MANUAL CHECK NEEDED. This is a configuration-specific local privileged crash with no supported memory corruption or privilege escalation primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/amdgpu: fix zero-size GDS range init on RDNA4 Commit: 1f5d33e7b0a9a2a140f46e22fb52eede323c5946 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1f5d33e7b0a9a2a140f46e22fb52eede323c5946 Commit description: RDNA4 (GFX 12) hardware removes the GDS, GWS, and OA on-chip memory resources. The gfx_v12_0 initialisation code correctly leaves adev->gds.gds_size, adev->gds.gws_size, and adev->gds.oa_size at zero to reflect this. amdgpu_ttm_init() unconditionally calls amdgpu_ttm_init_on_chip() for each of these resources regardless of size. When the size is zero, amdgpu_ttm_init_on_chip() forwards the call to ttm_range_man_init(), which calls drm_mm_init(mm, 0, 0). drm_mm_init() immediately fires DRM_MM_BUG_ON(start + size <= start) -- trivially true when size is zero -- crashing the kernel during modprobe of amdgpu on an RX 9070 XT. Guard against this by returning 0 early from amdgpu_ttm_init_on_chip() when size_in_page is zero. This skips TTM resource manager registration for hardware resources that are absent, without affecting any other GPU type. DRM_MM_BUG_ON() only asserts if CONFIG_DRM_DEBUG_MM is enabled in the kernel config. This is apparently rarely enabled as these chips have been in the market for over a year and this issue was only reported now. Link: https://lore.kernel.org/all/bug-221376-2300@https.bugzilla.kernel.org%2F/ Link: https://bugzilla.kernel.org/show_bug.cgi?id=221376 Oops-Analysis: http://oops.fenrus.org/reports/bugzilla.korg/221376/report.html Assisted-by: GitHub Copilot:Claude Sonnet 4.6 linux-kernel-oops-x86. Signed-off-by: Arjan van de Ven Cc: Alex Deucher Cc: "Christian König" Cc: amd-gfx@lists.freedesktop.org Cc: dri-devel@lists.freedesktop.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Alex Deucher (cherry picked from commit 5719ce5 ) Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman Changed files: drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.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=1f5d33e7b0a9a2a140f46e22fb52eede323c5946 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46276 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46276 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:L/PR:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.4 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: 0 Paranoid ActionableScore: 1 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: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW 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).