From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-99004][MODERATE REGULAR] drm/imagination: Size page table preallocation by device address Date: Mon, 26 Oct 2026 14:40:32 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-99004 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: 2 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 51b56bad96fd20127034f660b337c00317c65151 List-Id: CVE: CVE-2026-99004 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: drm/imagination: Size page table preallocation by device address Commit: 51b56bad96fd20127034f660b337c00317c65151 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=51b56bad96fd20127034f660b337c00317c65151 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99004 Analysis date: Mon, 26 Oct 2026 14:40:32 -0400 ActionableScore: 2 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: A low-privilege DRM mapping can underflow the Imagination MMU table count and induce excessive allocation leading to host OOM panic, without evidence of memory corruption or authorization bypass. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99004 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99004 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-2026-99004 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-99004 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=MODERATE RESULT=DIFF (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC) 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-191;**CWE-400;CWE-770;BEST CVSS score: '5.5';DESCR 'An incorrect page table count in the Imagination DRM MMU path can make an unsigned index difference underflow when a device virtual mapping crosses a page table boundary. The resulting huge preallocation request can exhaust system memory and trigger an OOM panic, providing a local denial of service without evidence of an OOB access, UAF, information leak, or write primitive. For the CVSS the PR:L value reflects that an attacker needs local process access to the affected DRM render or device interface, while administrative privileges are not necessarily required when the render node is available. The issue is not directly network reachable and affects systems using the vulnerable Imagination GPU driver with an accessible mapping interface. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 5.5 and the production ActionableScore returned 2 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to MODERATE because the CVSS score, vector or bug class threshold rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH and V41_INHERITED_KPANIC_PROMOTION_BLOCKED and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 5.5 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) MAYBE OOB DANGER SIMPLEFIX HARDWARE LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH V41_INHERITED_KPANIC_PROMOTION_BLOCKED MANUAL_REVIEW_REQUIRED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES RequiresHostUID0=NO AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 2. * Conservative score: 2; no floor or cap applied. * Raw paranoid score: 2. * Paranoid score: 2; no defensible additional corrupt or boundary signal. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 Local low-privilege trigger: supplied triage evidence identifies access through an affected DRM render/device mapping interface without host-administrator powers. * +1 Reliable kernel crash/strong DoS: the unsigned table-index subtraction can underflow, request a huge MMU-page preallocation, exhaust system memory, and trigger an OOM panic. * No additional resource-exhaustion or Availability point: that would double-count the same OOM-panic outcome. * No corruption point: the patch shows an incorrect allocation count, not an OOB read/write, UAF, stale pointer, or corrupted active object. * NEW52/B5-R does not apply: there is no retry-accumulated index, confirmed heap OOB write, or later consumption of corrupted descriptors. * No authorization, confidentiality, integrity, LPE, remote-reachability, or arbitrary-write signal is shown. * No hardware rarity penalty: affected Imagination GPU hardware is required, but the evidence does not establish rare hardware or attacker physical access. 3. Reachability analysis A local process with permission to use the affected DRM render/device mapping interface can supply a mapping crossing a page-table boundary. The supplied summary supports below-host-admin access through a render node, so host UID 0 and host-admin capabilities are not required for that deployment. No namespace capability is involved or shown. An affected GPU and driver are prerequisites; no boot option, race, retry loop, or prior privileged configuration is evidenced. Exact device-node permission and ioctl call-site details are not included. 4. Primitive and severity reading The primitive is arithmetic underflow in page-table preallocation accounting, producing an excessive allocation request and possible host OOM panic. It is resource-exhaustion/DoS behavior, classified CLASS_C, rather than memory corruption. No post-allocation OOB operation or protected-state consumption is shown. Consequently there is no Important-preserving Class B/A primitive, and automatic downgrade remains allowed. 5. One-sentence report phrase A low-privilege DRM mapping can underflow the Imagination MMU table count and induce excessive allocation leading to host OOM panic, without evidence of memory corruption or authorization bypass. 6. Manual review advice MANUAL CHECK RECOMMENDED Confirm affected render-node permissions and whether product OOM policy makes the exhaustion reliably host-fatal. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/imagination: Size page table preallocation by device address Commit: 51b56bad96fd20127034f660b337c00317c65151 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=51b56bad96fd20127034f660b337c00317c65151 Commit description: Commit 0a82240 ("drm/imagination: Fix page count for page table for map() interface") passed the device address to pvr_mmu_op_context_create(), but the preallocation is still sized from device_addr + sgt_offset with an exclusive end. The offset into the object's pages has no place in a device-virtual range, and the exclusive end allocates one table too many when the range ends on a table boundary. Count the tables from device_addr and the inclusive end of the range. The new calculation does not take page table indices into account. This fixes another issue with the previous implementation, where the difference between start and end indices could underflow when a mapping crossed a page table boundary. This would lead to the driver preallocating a huge number of MMU pages, exhausting system memory and triggering an out of memory panic. Fixes: 0a82240 ("drm/imagination: Fix page count for page table for map() interface") Fixes: ff5f643 ("drm/imagination: Add GEM and VM related code") Signed-off-by: Gyeyoung Baek Reviewed-by: Brajesh Gupta Reviewed-by: Alessio Belle Cc: stable@vger.kernel.org [Alessio: add paragraph to point out OOM bug being fixed, cc stable] Link: https://patch.msgid.link/20261001-pvr-fixes-a-v2-2-f58254e5dfb8@gmail.com Signed-off-by: Alessio Belle Signed-off-by: Greg Kroah-Hartman Changed files: drivers/gpu/drm/imagination/pvr_mmu.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=51b56bad96fd20127034f660b337c00317c65151 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99004 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99004 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: unknown Paranoid ActionableScore: 2 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).