From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-80582][MODERATE 7.0] drm/shmem_helper: Check VMA boundaries for PMD mappings Date: Wed, 26 Aug 2026 12:07:28 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-80582 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: 12803e89a1e593fd1e784dfe7453f5e392ccaff2 List-Id: CVE: CVE-2026-80582 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: drm/shmem_helper: Check VMA boundaries for PMD mappings Commit: 12803e89a1e593fd1e784dfe7453f5e392ccaff2 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=12803e89a1e593fd1e784dfe7453f5e392ccaff2 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80582 Analysis date: Wed, 26 Aug 2026 12:07:28 -0400 ActionableScore: 6 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A local DRM shmem huge fault can install a PMD mapping that extends outside the VMA boundary, allowing a user with access to the affected DRM mmap path to trigger a kernel crash and requiring manual review for possible MM mapping confidentiality or integrity side effects. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80582 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80582 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-2026-80582 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:L/I:L/A:H';CWE-119;*CWE-20;CWE-754;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.6';DESCR 'drm shmem helper can install a PMD huge page mapping that extends outside the VMA when the fault address is PMD aligned with the physical address but the VMA does not cover the full PMD range. This violates VMA boundary assumptions and can later hit VM_BUG_ON_VMA in copy_pmd_range, causing a local kernel crash during operations such as fork or page table copy. For the CVSS the PR:L is used because a local user with access to an affected DRM mmap path or render node may be able to create the mapping and trigger the follow up MM path, while no administrator privileges are inherently required on systems exposing such devices to users. The issue is not network reachable. Impact is at least denial of service and the paranoid score keeps C:L and I:L because an out of VMA PMD mapping is a page table boundary violation that may affect access semantics, but the patch does not show a strong arbitrary write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) SKIP CVE-2026-80582 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE SIMPLEFIX HARDWARE LINUS KPANIC MEMORY - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=6 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 6 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Local unprivileged trigger: +1. A local user with access to an affected DRM mmap path or render node may be able to fault a GEM shmem mapping without full administrator privileges. * Memory corruption, weak/indirect corruption candidate: +1. The issue is an invalid PMD level mapping that can extend outside the VMA boundary. This is a page table mapping invariant violation, but the patch does not show arbitrary write, type confusion, controlled reclaim, or callback control. * Reliable kernel crash / strong DoS: +1. The commit states that the resulting mapping can trigger VM_BUG_ON_VMA() if it reaches copy_pmd_range(). * Memory layout invariant restoration: +1. The fix restores consistency between the PMD sized mapping range and the VMA boundaries before installing a huge PMD mapping. Paranoid additional signals: * Confidentiality impact plausible: +1. A PMD mapping beyond the intended VMA boundary may affect access semantics for neighboring virtual ranges, so limited confidentiality impact is technically plausible. * Integrity impact plausible: +1. The same out of VMA PMD mapping may also affect write or permission semantics in adjacent mappings, but this remains unproven from the patch. Not awarded: * Remote reachable: +0. No network path is involved. * Strong LPE plausibility: +0. No attacker controlled reclaim, arbitrary write, refcount takeover, type confusion, or controlled overwrite is shown. * Strong memory corruption primitive: +0. This is a mapping boundary violation, not a demonstrated arbitrary kernel memory corruption primitive. ## 3. Reachability analysis The likely trigger is local access to a DRM GEM shmem mmap path that can use PMD mappings. This may be reachable by ordinary users on systems exposing DRM render nodes, especially desktop, workstation, or GPU accelerated container environments. It is not network reachable. Namespaces and containers may matter if GPU devices or render nodes are passed through to a container. In that case the practical privilege level may remain close to PR:L rather than PR:H, because the attacker does not need full host root if the device node is delegated. The path depends on CONFIG_ARCH_SUPPORTS_PMD_PFNMAP, PMD mappable folios, and an affected DRM shmem helper user. This is configuration dependent, but not rare enough to auto close because DRM render nodes are commonly exposed to local users. Call-site confidence: medium. The patch shows the fault insertion site and the commit identifies copy_pmd_range() as the later failure point, but the exact affected DRM drivers and user visible trigger paths are not fully shown in the input. ## 4. Severity interpretation This is stronger than an ordinary Moderate because it touches MM page table mapping boundaries and can create a PMD mapping outside the VMA. The demonstrated realistic impact is local DoS through VM_BUG_ON_VMA() or kernel crash. Theoretical impact is higher because an out of VMA PMD mapping is a memory management boundary violation and could plausibly affect confidentiality or integrity of adjacent mappings. However, the patch does not demonstrate a direct privilege escalation primitive, arbitrary write, object reuse, or controlled memory corruption. Therefore the conservative score stays Borderline, while the paranoid score reaches Actionable Moderate. ## 5. One-sentence report phrase A local DRM shmem huge fault can install a PMD mapping that extends outside the VMA boundary, allowing a user with access to the affected DRM mmap path to trigger a kernel crash and requiring manual review for possible MM mapping confidentiality or integrity side effects. ## 6. Manual review recommendation MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK. Reason: this is an MM page table boundary issue in a locally reachable DRM path, and while the proven impact is DoS, the PMD mapping outside VMA semantics justify manual review before auto closing. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/shmem_helper: Check VMA boundaries for PMD mappings Commit: 12803e89a1e593fd1e784dfe7453f5e392ccaff2 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=12803e89a1e593fd1e784dfe7453f5e392ccaff2 Commit description: In the ->huge_fault handler do not install a PMD huge page mapping if the huge page exceeds the boundaries of the VMA. All other ->huge_fault handlers have similar checks and the resulting mapping will trigger a VM_BUG_ON_VMA() if it ever reaches copy_pmd_range(). Cc: Pedro Demarchi Gomes Cc: Boris Brezillon Cc: stable@vger.kernel.org Fixes: fc3bbf3 ("drm/shmem-helper: Fix huge page mapping in fault handler") Signed-off-by: Christian A. Ehrhardt Reviewed-by: Boris Brezillon Link: https://patch.msgid.link/20260622215718.1532689-1-lk@c--e.de Signed-off-by: Boris Brezillon Signed-off-by: Greg Kroah-Hartman Changed files: drivers/gpu/drm/drm_gem_shmem_helper.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=12803e89a1e593fd1e784dfe7453f5e392ccaff2 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80582 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80582 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:H The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 6.6 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).