From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-80729][MODERATE 7.0] mm/huge_memory: initialise workingset state before folio split Date: Thu, 03 Sep 2026 04:56:49 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-80729 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: 4 X-AL-KERNEL-Commit: d858f7c9fc514f1d9d3be7d00b2dd4e2f2383b55 List-Id: CVE: CVE-2026-80729 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: mm/huge_memory: initialise workingset state before folio split Commit: d858f7c9fc514f1d9d3be7d00b2dd4e2f2383b55 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d858f7c9fc514f1d9d3be7d00b2dd4e2f2383b55 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80729 Analysis date: Thu, 03 Sep 2026 04:56:49 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate at minimum Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80729 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80729 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-80729 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-80729 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-664;CWE-459;**CWE-400;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A folio split path in mm huge_memory can create memcg charged page cache xa_nodes without installing the required workingset and shadow_nodes list_lru state in the xa_state. Reclaim may later observe this inconsistent list_lru state and hit VM_WARN_ON(!css_is_dying()), which can become a local denial of service on systems configured to panic on warnings or under severe reclaim pressure. For the CVSS the PR:L is used because a local user process is needed to drive memory mappings, page cache activity, folio split behavior, and reclaim conditions. The issue is not directly network reachable and does not show a concrete UAF, OOB write, information leak, or arbitrary write primitive. Impact is primarily availability loss and the paranoid score raises only availability to high while keeping confidentiality and integrity as none.';NO MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) SKIP CVE-2026-80729 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE DANGER SIMPLEFIX SYZBOT MEMORY DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH INCREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN5 DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 1. ActionableScore * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: 2. Signal breakdown * Local unprivileged trigger: +1. A local user can plausibly drive page cache activity, folio split paths, and reclaim pressure. * Memory layout invariant restoration: +1. The patch restores consistency between xa_state, workingset update callback, and shadow_nodes list_lru state. * Availability impact realistic: +1. Reclaim can hit VM_WARN_ON(!css_is_dying()), and this can become DoS on panic_on_warn systems or under severe reclaim disruption. * Important filesystem/storage path: +1. The affected path is page cache and MM reclaim related. * Paranoid broad core-MM exposure: +1. Page cache, XArray, memcg, and reclaim are core kernel paths, even though the exact trigger requires specific folio split conditions. * No generic memory corruption signal. The patch does not show UAF, OOB write, double free, arbitrary write, or attacker-controlled object reuse. * No LPE signal. There is no supported privilege escalation primitive. * No C/I impact signal. The described failure is warning or availability loss, not disclosure or unauthorized modification. 3. Reachability analysis This is local, not network reachable. The likely trigger requires a local process that can create suitable page cache and memory pressure conditions so that __folio_split() allocates page-cache xa_nodes and later reclaim walks the affected list_lru state. No administrative capability is clearly required for the general memory pressure and page cache activity, so PR:L is the practical CVSS-style interpretation. Containers may make triggering easier or harder depending on memcg, filesystem, and large folio configuration, but the issue does not directly cross a namespace security boundary. 4. Severity interpretation This behaves like an actionable Moderate, not an Important-class vulnerability. The technically relevant issue is an MM/page-cache accounting and lifetime-state inconsistency, but the demonstrated consequence is VM_WARN_ON during reclaim rather than a concrete memory corruption primitive. Theoretical severity increases on panic_on_warn systems, but there is no evidence of controlled reclaim, stale object reuse, write-after-free, type confusion, or privilege escalation. 5. One-sentence report phrase A folio split path in mm huge_memory can leave memcg charged page cache xa_nodes without the required workingset and shadow_nodes list_lru state, causing reclaim to hit VM_WARN_ON and potentially producing local denial of service on panic_on_warn or heavy reclaim systems. 6. Manual review recommendation MANUAL CHECK RECOMMENDED. The issue is not a strong memory corruption or LPE candidate, but it affects core MM/page-cache reclaim state and reaches ActionableScore 5 only under the paranoid interpretation, so it should not be silently auto-closed without at least lightweight human review. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: mm/huge_memory: initialise workingset state before folio split Commit: d858f7c9fc514f1d9d3be7d00b2dd4e2f2383b55 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d858f7c9fc514f1d9d3be7d00b2dd4e2f2383b55 Commit description: xas_try_split() adds __GFP_ACCOUNT for page-cache xa_nodes, but __folio_split() leaves the xa_state's xa_lru unset. That lets a live, memcg-charged xa_node exist without being linked into the mapping's shadow_nodes list_lru; when reclaim later walks the list_lru it trips VM_WARN_ON(!css_is_dying()). Use mapping_set_update() to install both the workingset update callback and the shadow_nodes list_lru on the xa_state. Link: https://lore.kernel.org/20260725101419.3938406-1-matt@readmodwrite.com Fixes: 58729c0 ("mm/huge_memory: add buddy allocator like (non-uniform) folio_split()") Signed-off-by: Matt Fleming Reported-by: syzbot+c5b060ce82921a2fd500@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=c5b060ce82921a2fd500 Reviewed-by: Zi Yan Acked-by: David Hildenbrand (Arm) Cc: Baolin Wang Cc: Barry Song Cc: Dave Chinner Cc: Dev Jain Cc: Kairui Song Cc: Lance Yang Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Muchun Song Cc: Nico Pache Cc: Roman Gushchin Cc: Ryan Roberts Cc: Shakeel Butt Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman Changed files: mm/huge_memory.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=d858f7c9fc514f1d9d3be7d00b2dd4e2f2383b55 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80729 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80729 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:L/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: 4 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).