From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-90183][LOW] blk-iolatency: clear delay state when freeing policy data [ Upstream Date: Thu, 17 Sep 2026 16:24:10 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-90183 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: 02f1b90ab33ef99c89dd96a385b432ff57abc64d List-Id: CVE: CVE-2026-90183 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: blk-iolatency: clear delay state when freeing policy data [ Upstream Commit: 02f1b90ab33ef99c89dd96a385b432ff57abc64d Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=02f1b90ab33ef99c89dd96a385b432ff57abc64d Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90183 Analysis date: Thu, 17 Sep 2026 16:24:10 -0400 ActionableScore: 2 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90183 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90183 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-2026-90183 LOW https://www.kernelcve.org/list/?q=CVE-2026-90183 CHECK WITH IMPACT FROM ORIG NN LOW 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-459;CWE-404;**CWE-400;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'blk iolatency can leave a cgroup delay state active after io.latency policy data is freed. A group that was throttled only as collateral can keep blkg use_delay set and blkcg congestion_count elevated, so blk_cgroup_congested returns true for tasks in that cgroup and descendants. This can reduce readahead to one page, skip async readahead, and add swap allocation throttling, causing persistent local performance degradation or DoS until the cgroup is removed. For the CVSS the PR:L is used for the paranoid score because a local user or service with delegated cgroup io controller control may be able to create the needed sibling pressure and policy teardown, while typical host wide configuration remains administrative. The issue is not network reachable and does not indicate memory corruption or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) YES INIT NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 2 * Conservative score: 2. No floor or cap applied. * Raw paranoid score: 2 * Paranoid score: 2. No floor or cap applied. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown Positive signals: * +1 Concrete persistent kernel accounting/state leak. `blkg->use_delay` and `blkcg->congestion_count` can remain set/elevated after policy data is freed, with no remaining owner able to clear the state. * +1 Persistent local availability degradation. Affected cgroup tasks and descendants may suffer reduced readahead, skipped async readahead, and swap allocation throttling until the cgroup is removed. Negative or non-awarded signals: * 0 No RealUAF. The patch does not show use-after-free, stale dereference, double free, or repeated lifetime/refcount mutation. * 0 No memory corruption primitive. The issue is stale throttling/accounting state, not an overwrite, UAF, OOB access, or type confusion. * 0 No confidentiality or integrity signal. The bug affects performance/throttling state only. * 0 No remote reachability. Trigger is through local block cgroup/io.latency policy behavior, not network input. * 0 No host-admin penalty applied. Host-wide io.latency configuration is commonly administrative, but supplied evidence does not prove host-admin-equivalent privilege is always required because delegation/service management may exist. * 0 No Important-grade resource exhaustion. The impact is persistent and annoying, but appears scoped to the affected cgroup hierarchy rather than a direct host-wide crash or memory corruption path. 3. Reachability analysis The trigger requires a blk-iolatency setup where one sibling misses its latency target and peers are scaled down, causing a peer with `min_lat_nsec == 0` to receive delay state. The stale state becomes persistent when the policy data is freed without clearing the delay. An ordinary local user trigger is not established. A host administrator or cgroup manager can configure io.latency and policy teardown. A delegated service or user with write access to the relevant cgroup io controller files may also be able to trigger the condition, but the supplied data does not prove the complete trigger is reachable by an unprivileged user. No namespace-scoped capability path is established. No special hardware beyond use of the block IO controller is indicated. This is not a race requiring narrow timing. It is an ordered state-cleanup bug. 4. Primitive and severity interpretation The exact primitive is a persistent stale block-cgroup throttling/accounting state. It is not an active structured UAF and not fixed stale storage. No cleanup/destructor stale dereference is shown. No concrete repeated release/refcount operation exists. The demonstrated consequence is local performance degradation or denial of service for tasks in the affected cgroup and descendants. The speculative consequence is broader operational slowdown if the affected cgroup hosts important workloads, but the patch does not support memory corruption, privilege escalation, or cross-boundary compromise. PrimitiveClass is CLASS_C because the behavior is invalid persistent state causing DoS-like throttling without an independently useful corruption primitive. ImportantCandidate is NO because there is no UAF, no authorization bypass, no COW/ownership violation, no controlled corruption, and no plausible LPE primitive. AutoDowngradeAllowed is YES because automatic closure would not discard a meaningful unresolved kernel corruption or security-boundary primitive. 5. One-sentence report phrase blk-iolatency can leave stale cgroup delay state after io.latency policy data is freed, causing persistent local throttling and performance degradation for the affected cgroup hierarchy without evidence of memory corruption or privilege escalation. 6. Manual review recommendation NO MANUAL CHECK NEEDED Reason: this is a local persistent resource/accounting cleanup issue with DoS-like performance impact only, no UAF, no memory corruption, no network reachability, and no privilege-escalation primitive. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: blk-iolatency: clear delay state when freeing policy data [ Upstream Commit: 02f1b90ab33ef99c89dd96a385b432ff57abc64d Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=02f1b90ab33ef99c89dd96a385b432ff57abc64d Changed files: block/blk-iolatency.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=02f1b90ab33ef99c89dd96a385b432ff57abc64d ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90183 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90183 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:H/PR:H/UI:N/S:U/C:N/I:N/A:L 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).