From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-89997][MODERATE 7.0] dm: fix resume-vs-remove race Date: Wed, 16 Sep 2026 07:23:25 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-89997 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: 9757367bcf1d5d2c50b94d005abca21f3eedd7c3 List-Id: CVE: CVE-2026-89997 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: dm: fix resume-vs-remove race Commit: 9757367bcf1d5d2c50b94d005abca21f3eedd7c3 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9757367bcf1d5d2c50b94d005abca21f3eedd7c3 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89997 Analysis date: Wed, 16 Sep 2026 07:23:25 -0400 ActionableScore: 5 ActionableScore lower bound: 3 Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review Manual review required: YES Summary: A resume-vs-remove race in device mapper can skip target postsuspend handling, leaving dm-integrity reboot notifier state registered after the target is freed and creating a local host-admin-triggered UAF with kernel crash risk and unresolved exploitation leverage. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-89997 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89997 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-2026-89997 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-89997 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-362;*CWE-416;*CWE-672;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A race in device mapper can occur when resume ioctl and remove ioctl are issued at the same time. The mapped device may be resumed after it was suspended in __dm_destroy, so the active table can be destroyed without calling the target postsuspend callback. Some dm targets rely on postsuspend as part of their removal lifetime rules. In dm-integrity this can leave a reboot notifier registered after the target object is freed, creating a use after free condition. For the CVSS the PR:L is used for the higher risk interpretation because device mapper control is normally administrative, but it may be reachable by a delegated local storage service account or a reduced capability root context in some deployments. The issue is not network reachable. Impact is at least local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to kernel use after free, so it should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 4) YES DISK INIT RACE UAF HARDWARE LINUS BOOT DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=3 PrimitiveClass=CLASS_B RealUAF=YES HostAdminRequired=YES NamespaceScopedPrivilege=NO ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO ## 1. ActionableScore * Raw conservative score: 3 * Conservative score: 3 * Raw paranoid score: 4 * Paranoid score: 5 * Applied paranoid floor/cap: manual-review safety floor for active structured UAF with stale notifier registration, 4 -> 5 * Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**:: ## 2. Signal breakdown Conservative signals: * +2: Real UAF / lifetime violation. The commit explicitly states that skipping `postsuspend` can leave the `dm-integrity` reboot notifier registered after the target object is freed. * +1: Reliable kernel crash / strong DoS. A stale reboot notifier callback after object free can realistically lead to kernel fault or crash. * +1: Secondary registration / notifier staleness. The bug leaves an active notifier-chain registration associated with an object whose target lifetime has ended. * +1: Active structured stale object. The stale object is not just passive metadata. It remains reachable through a kernel notifier chain and may be consumed later. * -2: Host-admin-equivalent privilege. Device-mapper resume/remove ioctls are normally controlled through host administrative device-mapper management privileges. Paranoid additional signal: * +1: Attacker-influenced repeatable lifetime manipulation. A caller with device-mapper control can attempt concurrent resume/remove operations repeatedly against the affected mapped device lifecycle. Not awarded: * Controlled reclaim not demonstrated. * Arbitrary read/write not demonstrated. * Confidentiality or integrity impact not awarded as a direct signal. * Concrete repeated release/refcount mutation not established. This is a stale notifier/UAF case, not a visible second `put` or `release` on the exact same dangling reference. * Extra availability point not awarded because the crash/DoS is already counted. * Remote reachability not established. * Namespace-scoped privilege not established. Repeated-release/refcount check: * First release can end lifetime: yes, target/table destruction can free target state. * Exact same reference survives to second lifetime mutation: not established. * Second operation is real lifetime/refcount mutation: not established. * +1 Concrete repeated release/refcount awarded: no. * Paranoid repeated-refcount leverage +1 awarded: no. * FLOOR 5 from repeated-release rule applied: no. ## 3. Reachability analysis The trigger is local control-plane activity through device-mapper ioctls: resume and remove issued concurrently for the same mapped device. This is not packet-driven and not remotely reachable by itself. The complete trigger normally requires host-level device-mapper administration, effectively host root or equivalent `CAP_SYS_ADMIN` over device-mapper control. Device-mapper block devices are not meaningfully namespace-scoped in the way required to claim `NamespaceScopedPrivilege=YES`. Prior setup is likely required: an affected mapped device and a target such as `dm-integrity` must exist. This setup is also normally administrative. No special physical hardware is required beyond normal block/device-mapper use. The race requires concurrent resume-vs-remove timing, but the same privileged actor can repeat attempts. Therefore I did not apply a hard-race penalty. ## 4. Primitive and severity interpretation The exact primitive is a race-induced lifecycle violation in device mapper. `dm_resume()` could proceed while the mapped device is being destroyed, allowing the table to be destroyed without the target `postsuspend` callback. For `dm-integrity`, this can leave a reboot notifier registered after the target object is freed, creating a real UAF. This is an active structured-object UAF rather than fixed stale storage. The stale state remains registered in a notifier chain and can be consumed later by kernel notifier traversal. It is stronger than a simple immediate NULL dereference, but the supplied patch does not establish controlled reclaim, arbitrary kernel read/write, callback hijack, or demonstrated local privilege escalation. Primitive class is `CLASS_B`: a real kernel lifetime/UAF primitive exists and exploitation-leverage analysis is required. It is not `CLASS_A` because no controlled replacement, directed corruption, arbitrary write, or demonstrated LPE is supplied. `ImportantCandidate=YES` because a stale active notifier registration after free is meaningful unresolved kernel lifetime corruption, even though the normal trigger is host-admin-gated. `AutoDowngradeAllowed=NO` because automatically treating this as ordinary crash-only cleanup would discard the unresolved UAF/notifier-chain primitive. Likely operational severity is Actionable Moderate. It may become an Important-class issue only if additional evidence shows below-host-admin reachability, controlled reclaim/reuse, or a practical privilege-escalation chain. ## 5. One-sentence report phrase A resume-vs-remove race in device mapper can skip target postsuspend handling, leaving dm-integrity reboot notifier state registered after the target is freed and creating a local host-admin-triggered UAF with kernel crash risk and unresolved exploitation leverage. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the patch establishes a real UAF involving an active notifier-chain registration. Even though normal reachability appears host-admin-gated, the stale callback registration makes this unsafe to automatically downgrade without checking target-specific lifetime behavior and possible delegated storage-management exposure. ## 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: dm: fix resume-vs-remove race Commit: 9757367bcf1d5d2c50b94d005abca21f3eedd7c3 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9757367bcf1d5d2c50b94d005abca21f3eedd7c3 Commit description: If the user issues the resume ioctl and the remove ioctl at the same time, it may be possible that the device is resumed after it is suspended in __dm_destroy. The result is that the table is destroyed without calling the postsuspend method. Dm targets expect that they may be removed only after the postsuspend method method was called. If we break this expectation, it can cause misbehavior in various targets. For example - in the dm-integrity target, the reboot notifier is not unregistered, leading to use-after-free. Fix this bug by refusing to resume if the device is being destroyed. Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman Changed files: drivers/md/dm.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=9757367bcf1d5d2c50b94d005abca21f3eedd7c3 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-89997 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89997 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:H/I:H/A:H The Best / paranoid CVSS score: 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: 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).