From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74420][MODERATE REGULAR] drm/gpusvm: Reject VMAs with VM_IO or VM_PFNMAP when creating SVM ranges [ Upstream Date: Sun, 16 Aug 2026 05:40:55 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74420 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: 353f26c74660bcbd8d82cd76622748e14a5a5db3 List-Id: CVE: CVE-2026-74420 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: drm/gpusvm: Reject VMAs with VM_IO or VM_PFNMAP when creating SVM ranges [ Upstream Commit: 353f26c74660bcbd8d82cd76622748e14a5a5db3 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=353f26c74660bcbd8d82cd76622748e14a5a5db3 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74420 Analysis date: Sun, 16 Aug 2026 05:40:55 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Ordinary Moderate / Low-like. Autoclose candidate unless product exposure makes GPU SVM broadly reachable Manual review required: NO Summary: A local user with access to a GPUSVM-capable DRM GPU interface can create an SVM range over VM_IO or VM_PFNMAP memory, causing repeated get_pages() failures and a potential infinite loop in the driver page-fault handler, resulting in denial of service. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74420 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74420 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-2026-74420 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-20;*CWE-835;**CWE-400;BEST CVSS score: '5.5';DESCR 'GPUSVM can create an SVM range for a VMA that is marked VM_IO or VM_PFNMAP even though such mappings are not backed by normal struct page objects. When the GPU page fault path later tries to resolve pages for that range, get_pages can repeatedly fail and the driver page fault handler can enter an infinite loop. For the CVSS the PR:L is used because a local user process with access to the DRM GPU interface or render node is typically needed to create or fault such an SVM mapping. The issue is not network reachable and is triggered through a local GPU memory management path. Impact is denial of service through a stuck page fault path or kernel side CPU consumption. No direct confidentiality or integrity impact is assigned because the observed primitive is repeated fault handling failure rather than UAF, OOB access, or arbitrary write.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like. Autoclose candidate unless product exposure makes GPU SVM broadly reachable (with actual score 3) SKIP CVE-2026-74420 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: 99624bdff8670795b678eafa6509aaad3a5c0175 YES NO NO unknown MAYBE SIMPLEFIX HARDWARE INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 3 * Final recommended bucket: **Ordinary Moderate / Low-like. Autoclose candidate unless product exposure makes GPU SVM broadly reachable**:: ## 2. Signal breakdown Conservative signals: * Local unprivileged trigger: +1 A local process with access to the DRM GPU interface or render node can plausibly create or fault an SVM mapping. * Reliable kernel crash / strong DoS: +1 The commit explicitly says repeated get_pages() failures can lead to an infinite loop in a driver page-fault handler. Paranoid-only signal: * Availability impact realistic: +1 If the infinite loop occurs in a kernel driver fault path, it may cause persistent GPU driver hang or CPU consumption beyond a transient failed operation. Signals not awarded: * Generic memory corruption: +0 The patch shows validation of unsupported VMA flags, not UAF, OOB access, double free, type confusion, or arbitrary write. * Privilege escalation plausible: +0 No reclaim, overwrite, stale callback, refcount takeover, or object confusion primitive is shown. * Local high-control API bonus: +0 GPU object configuration alone is not enough. The patch does not show attacker control over lifetime, callbacks, DMA ownership, or exploitable memory layout. * Remote reachable: +0 This is a local DRM/GPUSVM path, not a network path. * Rare configuration penalty: 0 GPUSVM is feature and hardware dependent, but reachable through ordinary local GPU interfaces when enabled. ## 3. Reachability analysis The likely trigger is a local user process that can access a DRM GPU device and create or fault GPUSVM SVM ranges over VM_IO or VM_PFNMAP VMAs. This typically maps to PR:L rather than PR:H because render nodes are commonly exposed to non-root users in desktop, compute, or containerized GPU environments. Namespaces and containers may matter if GPU devices are passed through or exposed to workloads. A container with access to the relevant DRM device node could potentially reach the same path, but this is still local device access rather than a remote attack. The path is not universally default-enabled because it depends on GPUSVM-capable DRM driver support and access to suitable VMAs. Realistic impact is denial of service through a stuck GPU page-fault path or kernel-side CPU loop. Call-site confidence: medium. The patch directly rejects bad VMA types in drm_gpusvm_range_find_or_insert(), and the commit describes the downstream page-fault loop, but the full driver-specific fault-handler call chain is not included. ## 4. Severity interpretation This behaves like an ordinary Moderate local DoS issue, with a borderline Actionable Moderate interpretation only if the affected product broadly exposes GPUSVM-capable GPU devices to untrusted users or containers. The theoretical risk is limited because the patch does not support a memory corruption primitive. The realistic evidence supports repeated page resolution failure leading to an infinite loop, not confidentiality loss, integrity loss, or privilege escalation. ## 5. One-sentence report phrase A local user with access to a GPUSVM-capable DRM GPU interface can create an SVM range over VM_IO or VM_PFNMAP memory, causing repeated get_pages() failures and a potential infinite loop in the driver page-fault handler, resulting in denial of service. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED Reason: this is a validation-only fix with a concrete DoS failure mode and no supported memory corruption, privilege escalation, confidentiality, integrity, or network-reachable primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/gpusvm: Reject VMAs with VM_IO or VM_PFNMAP when creating SVM ranges [ Upstream Commit: 353f26c74660bcbd8d82cd76622748e14a5a5db3 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=353f26c74660bcbd8d82cd76622748e14a5a5db3 Changed files: drivers/gpu/drm/drm_gpusvm.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=353f26c74660bcbd8d82cd76622748e14a5a5db3 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74420 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74420 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: Not available 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).