From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98949][MODERATE 7.0] drm/imagination: Fix reference and vm_bo handling in remap() [ Upstream Date: Mon, 26 Oct 2026 20:17:16 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98949 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: 4 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: 521cf8403a185a9d5790fe324bb43ba7ea85f51c List-Id: CVE: CVE-2026-98949 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: drm/imagination: Fix reference and vm_bo handling in remap() [ Upstream Commit: 521cf8403a185a9d5790fe324bb43ba7ea85f51c Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=521cf8403a185a9d5790fe324bb43ba7ea85f51c Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98949 Analysis date: Mon, 26 Oct 2026 20:17:16 -0400 ActionableScore: 4 ActionableScore lower bound: 3 Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: A local DRM render client can repeatedly leak GEM references and create mismatched GPUVA ownership links through partial-overlap remaps, with plausible memory exhaustion but no shown UAF, OOB write, or privilege-boundary compromise. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98949 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98949 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-2026-98949 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98949 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=MODERATE_KPANIC RESULT=SAME V39_AEGIS_ONE_STEP_UP=MODERATE->MODERATE_KPANIC (final reconciliation agrees; DECISION: both 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-401;*CWE-664;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'A local DRM client can trigger the issue by submitting GPU VM mappings that partially overlap an existing mapping and cause pvr_vm_gpuva_remap to create retained prev or next parts. Each split leaked an unnecessary GEM reference and could retain shmem after the client closed, while the retained mappings were also linked to the new objects vm_bo instead of the original mappings vm_bo and triggered a drm_gpuva_link warning. For the CVSS the PR:L value reflects that an attacker needs local access to the Imagination DRM render interface and a process context able to issue the relevant VM map operations. The demonstrated primitive is persistent resource retention and incorrect GPUVA ownership metadata. There is no supported UAF, OOB access, arbitrary write, information disclosure, or direct remote attack path. Base availability impact is low, while sustained repeatable splitting could plausibly exhaust host memory in the paranoid case. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 5.5 and the production ActionableScore returned 4 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage LOW to MODERATE_KPANIC because the CVSS score, vector or bug class threshold rule was applied. KP and FD specialist checks stage MODERATE_KPANIC to MODERATE because KP specialist did not establish a qualifying panic. final reconciliation stage MODERATE to MODERATE_KPANIC because the cross model evidence reconciliation rule was applied. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE and DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 3.3 and ActionableScore 2 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) MAYBE LOCK WARNONLY LEAK HARDWARE LINUS TEST INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=3 PrimitiveClass=CLASS_B RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES RequiresHostUID0=NO AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 3. * Conservative score: 3; no floor or cap applied. * Raw paranoid score: 4. * Paranoid score: 4; no floor or cap applied. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown * +1 Local unprivileged trigger: supplied evidence grounds access through the local Imagination DRM render interface without host-administrator powers. * +1 Concrete persistent reference/resource leak: each partial-overlap split took an unnecessary GEM reference that was never dropped; testing retained about 32 MiB of shmem after close. * +1 Weak/indirect structured-state corruption: retained split mappings belonging to BO_A were linked into BO_B's `vm_bo`, violating the GPUVA object/ownership association and triggering `drm_WARN_ON(obj != vm_bo->obj)`. * Paranoid +1 strong resource-exhaustion concern: repeated attacker-invoked splitting can accumulate persistent GEM/shmem references and plausibly cause host memory pressure. This is not counted as a confirmed kernel crash. Not awarded: no UAF, OOB access, arbitrary write, controlled reclaim, disclosure, authorization bypass, or demonstrated later dangerous consumption of the mismatched GPUVA link. NEW52/B5-R and NEW53/B3-PENDING do not apply. 3. Reachability analysis The grounded actor is a local process with access to the relevant DRM render node and VM-map ioctl. This supports below-host-admin reachability and no host UID 0 requirement. No namespace capability is identified. Imagination GPU/device availability is required, but the evidence does not establish rare physical access or justify a hardware penalty. Repeated map/split operations appear attacker-invocable without a timing race. 4. Primitive and severity reading The patch proves two defects: a repeatable persistent GEM-reference leak and an active GPUVA ownership/link mismatch. The mismatch is CLASS_B object-state corruption, but only the warning and malformed association are shown; no later privileged consumer, stale lifetime use, cross-boundary effect, or useful write primitive is established. Thus it is not an Important candidate and may be downgraded after review. Likely operational severity is Moderate, driven primarily by repeatable memory retention. 5. One-sentence report phrase A local DRM render client can repeatedly leak GEM references and create mismatched GPUVA ownership links through partial-overlap remaps, with plausible memory exhaustion but no shown UAF, OOB write, or privilege-boundary compromise. 6. Manual review advice MANUAL CHECK RECOMMENDED Confirm whether later GPUVA list walkers consume the mismatched link before relying on an ordinary-Moderate disposition. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/imagination: Fix reference and vm_bo handling in remap() [ Upstream Commit: 521cf8403a185a9d5790fe324bb43ba7ea85f51c Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=521cf8403a185a9d5790fe324bb43ba7ea85f51c Changed files: drivers/gpu/drm/drm_gpuvm.c drivers/gpu/drm/imagination/pvr_vm.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=521cf8403a185a9d5790fe324bb43ba7ea85f51c ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98949 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98949 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:L 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: 3 Paranoid ActionableScore: 4 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).