From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-31765][MODERATE REGULAR] drm/amdgpu: Change AMDGPU_VA_RESERVED_TRAP_SIZE to 64KB Date: Sat, 01 Aug 2026 13:22:37 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-31765 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: 6b2614a0ff05a2d2836311425091c8feca6f0c21 List-Id: CVE: CVE-2026-31765 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: drm/amdgpu: Change AMDGPU_VA_RESERVED_TRAP_SIZE to 64KB Commit: 6b2614a0ff05a2d2836311425091c8feca6f0c21 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6b2614a0ff05a2d2836311425091c8feca6f0c21 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-31765 Analysis date: Sat, 01 Aug 2026 13:22:37 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline manual-review Moderate / not Important Manual review required: NO Summary: AMDGPU/KFD on 64K PAGE_SIZE systems can crash during local ROCm/KFD VM initialization because the reserved trap VA area is smaller than the computed CWSR TBA/TMA allocation, allowing a local GPU user to trigger a kernel DoS without evidence of privilege escalation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-31765 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-31765 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-2026-31765 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-131;CWE-682;**CWE-476;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'AMDGPU/KFD can crash on 64K PAGE_SIZE systems because the reserved trap VA area was only 8KB while the CWSR TBA/TMA allocation was derived from 2 * PAGE_SIZE and could become 128KB. A local user with access to the KFD or ROCm GPU device path can trigger the issue during VM acquisition or GPU runtime initialization, for example by running rocminfo or related compute tests. For the CVSS the PR:L is used because reliable triggering does not require full administrator privileges when the user already has normal access to the GPU device node. The issue is not network reachable and requires local code execution on a system with the affected AMDGPU/KFD configuration. Impact is denial of service via kernel crash. No concrete UAF, OOB write, arbitrary write, or information leak primitive is visible from the patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual-review Moderate / not Important (with actual score 3) MAYBE OOB NULLPTR INIT KERNEL_PANIC_PLUS_UAF HARDWARE TEST 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: **Borderline manual-review Moderate / not Important** ## 2. Signal breakdown Conservative scoring: * Local unprivileged trigger: +1 A normal local user with access to the KFD or ROCm GPU device path can trigger the crash by running rocminfo or similar GPU compute initialization paths. * Reliable kernel crash / strong DoS: +1 The commit includes a concrete Oops / NULL pointer dereference during kfd_ioctl_acquire_vm. * Rare AND configuration-dependent exposure: -1 The issue depends on AMDGPU/KFD with 64K PAGE_SIZE systems. This is not a broadly default x86 desktop/server configuration. * Availability impact realistic: +1 The crash is host-kernel level and appears reproducible on affected systems through ordinary ROCm/KFD initialization. Paranoid delta: * Do not subtract rare configuration dependency in the paranoid interpretation: +1 relative to conservative If the evaluated product commonly ships 64K PAGE_SIZE kernels with AMDGPU/KFD enabled, the rarity penalty should not be applied. Not counted: * No generic memory corruption bonus. The visible primitive is NULL / invalid pointer dereference, not UAF, OOB write, double free, type confusion, or arbitrary write. * No privilege escalation bonus. The patch and trace do not show attacker-controlled reclaim, overwrite, callback control, or a concrete LPE path. * No confidentiality or integrity impact. There is no visible information leak or write primitive. * No network reachability. This is a local ioctl / GPU runtime initialization path. Call-site confidence: high. The trace shows the ioctl path through KFD VM acquisition and the patch directly adjusts the mismatched reserved VA and allocation sizing constants. ## 3. Reachability analysis The bug is triggerable by a local user who can access the AMDGPU/KFD compute device interface, commonly via render, video, or ROCm-related device permissions. It does not normally require full root or CAP_SYS_ADMIN if the user already has access to the GPU device node. Namespaces and containers may matter if GPU device nodes are passed into containers. In that case, a containerized or reduced-privilege user with GPU access may still be able to trigger the host kernel crash. The path is not network reachable. It requires local code execution and an affected AMDGPU/KFD setup on a 64K PAGE_SIZE kernel. The practical exposure is therefore narrower than a common local syscall bug, but realistic on systems using ROCm or AMD GPU compute with this page-size configuration. ## 4. Severity interpretation This behaves like an ordinary-to-borderline Moderate local DoS issue, not an Important-class memory corruption vulnerability. The demonstrated impact is a kernel crash caused by a size mismatch between the reserved trap VA area and the KFD CWSR TBA/TMA allocation size on 64K page systems. Theoretical memory corruption potential is weak because an allocation/reservation mismatch exists in GPU VM setup, but the actual observed failure is an invalid pointer / NULL dereference during mutex handling. There is no evidence of controlled overwrite, stale object reuse, page-cache corruption, UAF reclaim, or privilege escalation. ## 5. One-sentence report phrase AMDGPU/KFD on 64K PAGE_SIZE systems can crash during local ROCm/KFD VM initialization because the reserved trap VA area is smaller than the computed CWSR TBA/TMA allocation, allowing a local GPU user to trigger a kernel DoS without evidence of privilege escalation. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Reason: the issue is a local low-privilege kernel crash path in a GPU ioctl/runtime initialization flow, and device-node access may be delegated to non-root users or containers. However, no concrete memory corruption or LPE primitive is visible, so it does not require Important-class escalation based on the provided patch alone. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/amdgpu: Change AMDGPU_VA_RESERVED_TRAP_SIZE to 64KB Commit: 6b2614a0ff05a2d2836311425091c8feca6f0c21 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6b2614a0ff05a2d2836311425091c8feca6f0c21 Commit description: Currently, AMDGPU_VA_RESERVED_TRAP_SIZE is hardcoded to 8KB, while KFD_CWSR_TBA_TMA_SIZE is defined as 2 * PAGE_SIZE. On systems with 4K pages, both values match (8KB), so allocation and reserved space are consistent. However, on 64K page-size systems, KFD_CWSR_TBA_TMA_SIZE becomes 128KB, while the reserved trap area remains 8KB. This mismatch causes the kernel to crash when running rocminfo or rccl unit tests. Kernel attempted to read user page (2) - exploit attempt? (uid: 1001) BUG: Kernel NULL pointer dereference on read at 0x00000002 Faulting instruction address: 0xc0000000002c8a64 Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries CPU: 34 UID: 1001 PID: 9379 Comm: rocminfo Tainted: G E 6.19.0-rc4-amdgpu-00320-gf23176405700 #56 VOLUNTARY Tainted: [E]=UNSIGNED_MODULE Hardware name: IBM,9105-42A POWER10 (architected) 0x800200 0xf000006 of:IBM,FW1060.30 (ML1060_896) hv:phyp pSeries NIP: c0000000002c8a64 LR: c00000000125dbc8 CTR: c00000000125e730 REGS: c0000001e0957580 TRAP: 0300 Tainted: G E MSR: 8000000000009033 CR: 24008268 XER: 00000036 CFAR: c00000000125dbc4 DAR: 0000000000000002 DSISR: 40000000 IRQMASK: 1 GPR00: c00000000125d908 c0000001e0957820 c0000000016e8100 c00000013d814540 GPR04: 0000000000000002 c00000013d814550 0000000000000045 0000000000000000 GPR08: c00000013444d000 c00000013d814538 c00000013d814538 0000000084002268 GPR12: c00000000125e730 c000007e2ffd5f00 ffffffffffffffff 0000000000020000 GPR16: 0000000000000000 0000000000000002 c00000015f653000 0000000000000000 GPR20: c000000138662400 c00000013d814540 0000000000000000 c00000013d814500 GPR24: 0000000000000000 0000000000000002 c0000001e0957888 c0000001e0957878 GPR28: c00000013d814548 0000000000000000 c00000013d814540 c0000001e0957888 NIP [c0000000002c8a64] __mutex_add_waiter+0x24/0xc0 LR [c00000000125dbc8] __mutex_lock.constprop.0+0x318/0xd00 Call Trace: 0xc0000001e0957890 (unreliable) __mutex_lock.constprop.0+0x58/0xd00 amdgpu_amdkfd_gpuvm_alloc_memory_of_gpu+0x6fc/0xb60 [amdgpu] kfd_process_alloc_gpuvm+0x54/0x1f0 [amdgpu] kfd_process_device_init_cwsr_dgpu+0xa4/0x1a0 [amdgpu] kfd_process_device_init_vm+0xd8/0x2e0 [amdgpu] kfd_ioctl_acquire_vm+0xd0/0x130 [amdgpu] kfd_ioctl+0x514/0x670 [amdgpu] sys_ioctl+0x134/0x180 system_call_exception+0x114/0x300 system_call_vectored_common+0x15c/0x2ec This patch changes AMDGPU_VA_RESERVED_TRAP_SIZE to 64 KB and KFD_CWSR_TBA_TMA_SIZE to the AMD GPU page size. This means we reserve 64 KB for the trap in the address space, but only allocate 8 KB within it. With this approach, the allocation size never exceeds the reserved area. Fixes: 34a1de0 ("drm/amdkfd: Relocate TBA/TMA to opposite side of VM hole") Reviewed-by: Christian König Suggested-by: Felix Kuehling Suggested-by: Christian König Signed-off-by: Donet Tom Signed-off-by: Alex Deucher (cherry picked from commit 31b8de5 ) Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman Changed files: drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h drivers/gpu/drm/amd/amdkfd/kfd_priv.h 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=6b2614a0ff05a2d2836311425091c8feca6f0c21 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-31765 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-31765 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:N/I:N/A:H 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).