From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-80720][MODERATE REGULAR] iomap: add a separate bio_set for iomap_split_ioend [ Upstream Date: Fri, 28 Aug 2026 07:21:42 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-80720 X-AL-KERNEL-Priority: MODERATE REGULAR X-AL-KERNEL-Severity: MODERATE REGULAR X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 3 X-AL-KERNEL-ActionableScore-Lower: 2 X-AL-KERNEL-Commit: cfc686a1174aa904dcad9b9a7c5e46b484d27e4e List-Id: CVE: CVE-2026-80720 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: iomap: add a separate bio_set for iomap_split_ioend [ Upstream Commit: cfc686a1174aa904dcad9b9a7c5e46b484d27e4e Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cfc686a1174aa904dcad9b9a7c5e46b484d27e4e Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80720 Analysis date: Fri, 28 Aug 2026 07:21:42 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Ordinary Moderate / Low-like storage DoS, not an Important candidate Manual review required: NO Summary: `iomap_split_ioend can deadlock because split bios may be allocated from the same bioset as the original ioend bios, allowing local filesystem I/O on affected storage setups to cause an I/O hang or DoS without evidence of memory corruption or privilege escalation.` ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80720 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80720 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 REGULAR 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-2026-80720 MODERATE 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-833;**CWE-400;CWE-667;BEST CVSS score: '4.7';DESCR 'iomap can deadlock during iomap_split_ioend because bio_split used iomap_ioend_bioset for bios that may already be allocated from the same bioset. If the bioset mempool is exhausted, splitting can wait for resources that cannot be freed until the current I/O completion path progresses, causing a filesystem I/O hang or broader local DoS. For the CVSS the PR:L is used because a local user may be able to trigger the affected writeback or append path by writing to an affected mounted filesystem, but reliable triggering depends on storage and filesystem configuration. The issue is not network reachable. Impact is denial of service through I/O deadlock. No confidentiality or integrity impact is supported because the patch only separates allocation pools and does not show a memory corruption primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like storage DoS, not an Important candidate (with actual score 3) SKIP CVE-2026-80720 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE DEADLOCK DISK INIT LINUS MEMORY DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 3 * Final recommended bucket: **Ordinary Moderate / Low-like storage DoS, not an Important candidate** ## 2. Signal breakdown Conservative signals: * Local unprivileged trigger: +1 A local user may be able to contribute to the affected path by writing to a mounted filesystem that uses iomap and can reach the relevant split bio path. * Reliable kernel crash / strong DoS: +1 The commit describes a real deadlock when `iomap_split_ioend()` splits bios that already came from `iomap_ioend_bioset` and the bioset is exhausted. * Hard or unreliable race / special timing required: -1 Triggering depends on bioset exhaustion and a specific storage or filesystem path involving split bios and zone append limits. It is not a simple deterministic syscall crash. * Important filesystem/storage path: +1 The bug is in iomap writeback or I/O completion infrastructure, which is used by important filesystem and block I/O paths. Paranoid extra signal: * Availability impact realistic: +1 In the worst reasonable case, the deadlock can cause a persistent filesystem I/O hang or broader storage stall, not merely a transient warning. No memory corruption signals are awarded. The patch separates allocation pools to avoid a mempool deadlock. It does not show UAF, OOB write, double free, stale pointer reuse, type confusion, page-cache corruption, or ownership/COW bypass. ## 3. Reachability analysis The likely trigger is local I/O activity against an affected mounted filesystem using iomap paths where `iomap_split_ioend()` may split bios due to zone append limits. A normal local user with write access to such a filesystem may be able to generate the I/O pattern, so PR:L is reasonable for CVSS-style thinking. Reliable triggering still depends on storage configuration and bioset pressure. This is not network reachable by itself. Namespaces or containers do not materially improve reachability unless the container has write access to an affected host-backed filesystem and can generate the relevant I/O workload. The affected path is in storage/writeback infrastructure, but the specific deadlock condition is configuration-dependent. ## 4. Severity interpretation This behaves like an ordinary Moderate or Low-like local DoS, not an Important-class vulnerability. The realistic impact is a filesystem or storage I/O hang caused by allocation-pool self-deadlock. There is no evidence of privilege escalation, confidentiality impact, integrity impact, or memory corruption. Theoretical severity is bounded because the fix addresses resource-pool separation, not object lifetime, pointer validity, page ownership, or attacker-controlled writes. ## 5. One-sentence report phrase `iomap_split_ioend can deadlock because split bios may be allocated from the same bioset as the original ioend bios, allowing local filesystem I/O on affected storage setups to cause an I/O hang or DoS without evidence of memory corruption or privilege escalation.` ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This can be handled as a non-urgent storage DoS unless the affected product relies heavily on iomap with zone append workloads where a persistent I/O hang would be operationally critical. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: iomap: add a separate bio_set for iomap_split_ioend [ Upstream Commit: cfc686a1174aa904dcad9b9a7c5e46b484d27e4e Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cfc686a1174aa904dcad9b9a7c5e46b484d27e4e Changed files: fs/iomap/ioend.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=cfc686a1174aa904dcad9b9a7c5e46b484d27e4e ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80720 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80720 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: Not available 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: 2 Paranoid ActionableScore: 3 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 REGULAR 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).