From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53265][MODERATE 7.0] dm cache policy smq: check allocation under invalidate lock [ Upstream Date: Thu, 25 Jun 2026 10:57:28 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53265 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: c242c7af2aecf0b538b8623bdb86b8b441da38d9 List-Id: CVE: CVE-2026-53265 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: dm cache policy smq: check allocation under invalidate lock [ Upstream Commit: c242c7af2aecf0b538b8623bdb86b8b441da38d9 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c242c7af2aecf0b538b8623bdb86b8b441da38d9 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53265 Analysis date: Thu, 25 Jun 2026 10:57:28 -0400 ActionableScore: 5 ActionableScore lower bound: 3 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A check-then-act race in dm-cache SMQ invalidation can let concurrent invalidators operate on a stale allocation state, corrupting policy queues or hash tables and potentially causing a local kernel crash or storage cache malfunction. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53265 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53265 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-2026-53265 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';CWE-362;CWE-367;CWE-415;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'dm cache policy smq has a check then act race in smq_invalidate_mapping because e allocated was tested before mq lock was taken. Two concurrent invalidators can both observe the entry as allocated, after which one thread removes it from SMQ queues and the hash table and returns it to the free list while the second thread continues with a stale predicate. This can corrupt policy queues or the hash table and can trigger a double free style failure for the same entry, leading at least to a local kernel crash or storage cache malfunction. For the CVSS the PR:L is used for the paranoid score because a local user or service with access to the cached block device or delegated storage management may be able to trigger concurrent invalidation paths, while full device mapper setup is normally administrative. The issue is not network reachable. Impact is at least denial of service. Limited confidentiality or integrity impact is defensible for manual review because the patch context describes kernel data structure corruption, but a reliable privilege escalation primitive is not proven.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) YES DISK RACE UAF IMPROVEONLY LINUS LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=3 ## 1. ActionableScore * Conservative score: 3 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Generic memory corruption, weak or indirect corruption candidate: +1. The stale unlocked `e->allocated` check can lead to queue or hash table corruption, but no attacker-controlled overwrite target or payload is shown. * Real lifetime corruption: +1. The same SMQ entry can be logically freed twice into the policy allocator or reused after removal from queues. * Reliable kernel crash / strong DoS: +1. The commit explicitly mentions corruption and hitting the allocation check in `free_entry()`. * Important filesystem/storage path: +1. This is in device-mapper cache policy metadata handling. * Hard or unreliable race / special timing required: -1. Two concurrent invalidators must hit the same cache block window. * Requires admin/root/storage-management privileges in typical deployments: -2. Creating and managing dm-cache mappings is normally privileged. Paranoid additional interpretation: * Local unprivileged or reduced-privilege trigger concern: +1. In some deployments, a user or service with write access to a cached block device, delegated storage management, or discard-generating workload may influence invalidation paths without full host-root authority. * Weak LPE concern: +1. Queue/hash corruption and double-free-style behavior are memory-corruption-relevant, but no reclaim, type confusion, callback overwrite, or controlled write primitive is demonstrated. * Constrained or metadata-only corruption: -1. The affected object is an internal SMQ policy entry and the corruption appears mostly structural/bookkeeping rather than attacker-payload-controlled. ## 3. Reachability analysis The bug is local and not network reachable. The direct affected path is `smq_invalidate_mapping()` in the dm-cache SMQ policy, reached during cache block invalidation. In normal deployments, configuring dm-cache and forcing low-level cache invalidation is administrative, so the conservative privilege model is high privilege. A paranoid model uses lower privilege because real systems may expose cached block devices to services, containers, or users that can generate discard or invalidation-like storage activity while not having full host-root privileges. The race requires concurrency on the same mapping, so exploitability is timing-dependent. ## 4. Severity interpretation This behaves stronger than an ordinary Moderate crash because the patch fixes a check-then-act race that can corrupt kernel storage-policy data structures and can produce double-free-style behavior. However, the realistic evidence still points mainly to local DoS or storage-cache malfunction, not a proven privilege escalation primitive. Theoretical memory corruption potential exists, but there is no demonstrated attacker-controlled reclaim, arbitrary write, type confusion, or callback corruption. Therefore the conservative bucket is borderline manual review, while the paranoid bucket is Actionable Moderate. ## 5. One-sentence report phrase A check-then-act race in dm-cache SMQ invalidation can let concurrent invalidators operate on a stale allocation state, corrupting policy queues or hash tables and potentially causing a local kernel crash or storage cache malfunction. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the issue is a race with kernel metadata corruption and double-free-style behavior in a storage subsystem. Even though practical LPE is not proven, the corruption class is strong enough that it should not be auto-closed. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: dm cache policy smq: check allocation under invalidate lock [ Upstream Commit: c242c7af2aecf0b538b8623bdb86b8b441da38d9 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c242c7af2aecf0b538b8623bdb86b8b441da38d9 Changed files: drivers/md/dm-cache-policy-smq.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=c242c7af2aecf0b538b8623bdb86b8b441da38d9 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53265 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53265 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:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 5.8 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: 5 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 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).