From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-99269][LOW] sched_ext: Wait for SCX_OPSS_DISPATCHING before moving tasks off DSQs [ Upstream Date: Tue, 03 Nov 2026 22:40:22 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-99269 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 2 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: cc2839946328c1618b3870d521b32bb9483d49d0 List-Id: CVE: CVE-2026-99269 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: sched_ext: Wait for SCX_OPSS_DISPATCHING before moving tasks off DSQs [ Upstream Commit: cc2839946328c1618b3870d521b32bb9483d49d0 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cc2839946328c1618b3870d521b32bb9483d49d0 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99269 Analysis date: Tue, 03 Nov 2026 22:40:22 -0400 ActionableScore: 2 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: A sched_ext dispatch race permits concurrent DSQ/runqueue operations on a task and may cause inconsistent scheduler state, stalls, or a kernel crash. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99269 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99269 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: LOW 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-2026-99269 LOW https://www.kernelcve.org/list/?q=CVE-2026-99269 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=LOW RESULT=DIFF TEMP_DISTANCE_MERGE_SKIP=AEGIS_NO_POSITIVE_SEVERITY_EVIDENCE (final Legacy and Aegis differ; FINAL: LOW, Aegis: MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-362;CWE-662;BEST CVSS score: '4.7';DESCR 'A race in sched_ext allows DSQ consume and move paths to operate on a task while the dispatching CPU is still running ops.dequeue and SCX_OPSS_DISPATCHING remains set. Concurrent DSQ and runqueue transitions can leave inconsistent scheduler state and may cause warnings, scheduling stalls, or a kernel crash. The patch does not establish UAF, OOB access, or an arbitrary write primitive. For the CVSS the PR:L value is selected because a local unprivileged workload may influence scheduling transitions after a sched_ext policy is active, although loading or replacing that policy normally requires elevated privileges. AC:H reflects the race window and the dependence on a sched_ext policy and workload that exercise the affected paths. The issue is local and is not directly network reachable. Availability impact is high while confidentiality and integrity remain none based on the demonstrated primitive. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 4.7 and the production ActionableScore returned 2 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were final reconciliation stage LOW to LOW because KP specialist did not establish a qualifying panic and the cross model evidence reconciliation 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 KPANIC_UNSUPPORTED_REMOVED and V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED. The independent weaker Aegis shadow evaluated CVSS 0.0 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 LOW.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) MAYBE SIMPLEFIX LEAK HARDWARE LINUS KPANIC_UNSUPPORTED_REMOVED V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES RequiresHostUID0=UNKNOWN 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 additional technically supported primitive. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 weak/indirect active-state corruption concern: DSQ consume/move code can operate on a task concurrently with `ops.dequeue()`, before `SCX_OPSS_DISPATCHING` is cleared, potentially producing inconsistent task, DSQ, runqueue, or `p->scx.flags` state. * +1 reliable crash/strong-DoS concern: inconsistent scheduler state plausibly supports scheduling stalls, warnings, or a kernel fault. No separate Availability point is awarded. * No race penalty: the patch establishes concurrency but not a specifically narrow, one-shot, or externally uncontrollable race. * No UAF, OOB write, arbitrary write, controlled reclaim, callback influence, information disclosure, or authorization bypass is shown. * B5-R does not apply: there is no retry-accumulated heap OOB write or later consumption of OOB-corrupted descriptors. * No active-state-retirement bonus: the fix adds waiting synchronization, but does not show replacement across a formal retirement protocol or semantic domain. * No confidentiality or protected-state integrity impact is established. 3. Reachability analysis A local workload may influence scheduling transitions after a sched_ext scheduler is active, but loading or replacing the policy generally involves elevated setup. The supplied evidence does not establish whether an unprivileged actor can independently complete the vulnerable sequence, which capability namespace governs all setup, or whether the required policy is already provisioned. Thus host-admin and namespace-scoped privilege remain unknown. No network, hardware, or authorization path is involved. 4. Primitive and severity reading The primitive is a synchronization failure allowing concurrent operations on active structured scheduler state. It is not a lifetime violation: no object is shown freed, reused, or accessed after lifetime end. The demonstrated concern is inconsistent state and possible host availability loss, without a separately useful corruption primitive. This supports CLASS_C, not an Important candidate. Auto-downgrade remains allowed because no material non-crash leverage or unresolved trust-boundary corruption chain is shown. 5. One-sentence report phrase A sched_ext dispatch race permits concurrent DSQ/runqueue operations on a task and may cause inconsistent scheduler state, stalls, or a kernel crash. 6. Manual review advice MANUAL CHECK RECOMMENDED Confirm practical trigger privileges, policy prerequisites, and whether stress testing demonstrates a host-wide crash rather than WARN-only recovery. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: sched_ext: Wait for SCX_OPSS_DISPATCHING before moving tasks off DSQs [ Upstream Commit: cc2839946328c1618b3870d521b32bb9483d49d0 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cc2839946328c1618b3870d521b32bb9483d49d0 Changed files: kernel/sched/ext/ext.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=cc2839946328c1618b3870d521b32bb9483d49d0 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99269 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99269 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:H/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.7 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: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW 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).