From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-80963][LOW] dm-stats: fix a crash if allocation of per-cpu data fails Date: Fri, 11 Sep 2026 19:56:28 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-80963 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: 1 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: c3f211b7a277dd404b4e7d23095be964b5b46a27 List-Id: CVE: CVE-2026-80963 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: dm-stats: fix a crash if allocation of per-cpu data fails Commit: c3f211b7a277dd404b4e7d23095be964b5b46a27 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c3f211b7a277dd404b4e7d23095be964b5b46a27 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80963 Analysis date: Fri, 11 Sep 2026 19:56:28 -0400 ActionableScore: 1 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-2026-80963 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80963 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-2026-80963 LOW https://www.kernelcve.org/list/?q=CVE-2026-80963 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:N/I:N/A:H';**CWE-476;CWE-703;CWE-754;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'A NULL pointer dereference can occur in dm-stats cleanup when allocation of per CPU statistics data fails and dm_stat_free later dereferences s stat_percpu for a CPU where the pointer was never initialized. The issue is in the error handling path for partial allocation failure, so reliable triggering normally requires local control of device mapper statistics plus memory pressure or allocation failure conditions. For the CVSS the PR:L is used in the paranoid score because delegated device mapper control or reduced admin contexts can make the trigger available to a less privileged local actor. The issue is not network reachable. Impact is denial of service via kernel crash only, with no evidence of UAF, out of bounds write, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) YES DANGER NULLPTR DISK SIMPLEFIX LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=YES NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: -1 * Conservative score: 1 * Raw paranoid score: -1 * Paranoid score: 1 * Applied floor/cap: raw score clamped from -1 to 1 as a nonzero ordinary kernel DoS triage score. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown Positive signals: * +1 Reliable kernel crash / strong DoS: allocation failure in dm_kvzalloc can send control flow to dm_stat_free, which dereferences s->stat_percpu[cpu] while it is NULL and crashes. * +0 Weak corruption concern: this is a NULL pointer dereference in cleanup, not an independently useful corruption primitive. Negative signals: * -2 Host-admin-equivalent privilege required: device-mapper statistics management is normally reached through privileged device-mapper control operations requiring host administrative privileges. Material non-awarded signals: * RealUAF not awarded: no stale post-lifetime object use is established. * Concrete repeated release/refcount not awarded: the patch adds a NULL check before freeing per-cpu storage, but there is no first release followed by a second lifetime mutation on the same dangling reference. * Controlled reclaim not demonstrated. * Arbitrary write not demonstrated. * Information disclosure not demonstrated. * Privilege escalation not demonstrated. * Remote reachability not established. * Extra availability point not awarded because the same NULL dereference crash is already counted once. * C/I impact not awarded because the evidence supports DoS only. 3. Reachability analysis Triggering requires local ability to configure or create dm-stats state and to reach the allocation failure path during per-cpu statistics setup. In normal Linux deployments, device-mapper control is host-admin-equivalent and not namespace-scoped for an ordinary unprivileged user. The failure also depends on an allocation failure condition, but this is an ordered error path rather than a race. No network trigger, special hardware, or guest-to-host boundary is involved. 4. Primitive and severity interpretation The primitive is an invalid NULL pointer dereference in dm_stat_free after partial initialization failure. The affected storage is not a freed active structured object and not a UAF. The stale-use and repeated-release exceptions do not apply. Demonstrated consequence is kernel crash / DoS. Speculative consequences beyond DoS are not supported by the patch. ImportantCandidate=NO because there is no memory corruption, ownership violation, authorization bypass, refcount mutation through a dangling object, or meaningful unresolved exploitation primitive. AutoDowngradeAllowed=YES because this is a constrained host-admin-triggered cleanup crash. 5. One-sentence report phrase A dm-stats cleanup error can dereference a NULL per CPU statistics pointer after allocation failure, causing a local host-admin-triggered kernel crash without evidence of UAF, information disclosure, or privilege escalation. 6. Manual review recommendation NO MANUAL CHECK NEEDED Reason: crash-only NULL dereference in a privileged device-mapper cleanup path, with no established corruption or security-boundary primitive. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: dm-stats: fix a crash if allocation of per-cpu data fails Commit: c3f211b7a277dd404b4e7d23095be964b5b46a27 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c3f211b7a277dd404b4e7d23095be964b5b46a27 Commit description: If "dm_kvzalloc(percpu_alloc_size, cpu_to_node(cpu))" fails, the code jumps to the "out" label and calls dm_stat_free. dm_stat_free does "for_each_possible_cpu(cpu) { dm_kvfree(s->stat_percpu[cpu][0].histogram, s->histogram_alloc_size);", which crashes with NULL pointer dereference if s->stat_percpu[cpu] is NULL. This commit fixes the bug by testing s->stat_percpu[cpu] for NULL before using it. Reported-by: Junzhe Yu Signed-off-by: Mikulas Patocka Fixes: fd2ed4d ("dm: add statistics support") Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman Changed files: drivers/md/dm-stats.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=c3f211b7a277dd404b4e7d23095be964b5b46a27 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80963 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80963 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: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: 1 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).