From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74572][MODERATE REGULAR] btrfs: zoned: fix deadlock between metadata writeback and transaction commit [ Upstream Date: Sat, 15 Aug 2026 14:25:31 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74572 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: 18577e77c2c8adaadf1f7c6e9bcd1c0b14e5dcdd List-Id: CVE: CVE-2026-74572 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: btrfs: zoned: fix deadlock between metadata writeback and transaction commit [ Upstream Commit: 18577e77c2c8adaadf1f7c6e9bcd1c0b14e5dcdd Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=18577e77c2c8adaadf1f7c6e9bcd1c0b14e5dcdd Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74572 Analysis date: Sat, 15 Aug 2026 14:25:31 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Ordinary Moderate / Low-like, not an Important candidate Manual review required: NO Summary: A zoned btrfs lock inversion between metadata writeback and transaction commit can deadlock filesystem operations, causing a local denial of service on affected zoned btrfs deployments. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74572 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74572 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-2026-74572 MODERATE CHECK WITH IMPACT FROM ORIG NN NONE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-667;*CWE-833;**CWE-400;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'A deadlock in zoned btrfs can occur when metadata writeback holds zoned_meta_io_lock and then enters a zone finish path that waits for the running transaction to commit. At the same time the transaction committer may need the same lock while writing tree extents, creating a lock inversion between writeback and commit. For the CVSS the PR:L because a local user with write access to the mounted zoned btrfs filesystem may be able to generate metadata writeback and transaction commit activity, although administrative privileges are normally required to create or mount the affected filesystem. The issue is not network reachable and requires a zoned btrfs deployment. Impact is denial of service through a filesystem hang or stuck commit path, with no supported evidence of memory corruption, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like, not an Important candidate (with actual score 3) SKIP CVE-2026-74572 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 YES NO NO unknown MAYBE DEADLOCK DISK SKIP INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: **2** * Paranoid score: **3** * Final recommended bucket: **Ordinary Moderate / Low-like, not an Important candidate** ## 2. Signal breakdown * **Local unprivileged trigger: +1** A local user with write access to an already mounted affected zoned btrfs filesystem may be able to generate metadata writeback and transaction commit activity. * **Reliable kernel crash / strong DoS: +1** The described failure is a deadlock between metadata writeback and transaction commit, causing a filesystem hang or stuck commit path. * **Availability impact realistic: +1** The hang can persist and block filesystem progress, so the availability impact is stronger than a transient warning. * **Important filesystem/storage path: +1** The affected code is in btrfs metadata writeback and transaction commit handling. * **Hard or timing-dependent condition: -1** The issue requires a specific lock ordering and transaction/writeback interleaving. It is reported as occasionally reproducible with fstests. * **Rare AND difficult-to-reach configuration: -1** The bug requires zoned btrfs and the tree-log block group zone activation path, which is not a broad default deployment. No memory corruption, UAF, OOB write, stale pointer reuse, page-cache corruption, or privilege escalation primitive is supported by the patch. ## 3. Reachability analysis The bug is locally reachable through filesystem activity on a mounted zoned btrfs filesystem. Creating or mounting such a filesystem normally requires administrative privileges, but once mounted, a local user with write permission may be able to help trigger metadata writeback and transaction commits. Containers only matter if they are given access to the mounted filesystem and can generate sufficient writeback activity. There is no network reachability. The configuration is specialized because it depends on zoned btrfs behavior and zone activation failure in the tree-log path. ## 4. Severity interpretation This behaves like an **ordinary Moderate / Low-like availability issue**, not an Important-class vulnerability. The realistic impact is denial of service through filesystem deadlock. Theoretical impact does not extend to confidentiality, integrity, or privilege escalation based on the provided patch and commit message. The paranoid score is slightly higher only because a local workload may repeatedly exercise the affected writeback and commit path once the filesystem is available. ## 5. One-sentence report phrase A zoned btrfs lock inversion between metadata writeback and transaction commit can deadlock filesystem operations, causing a local denial of service on affected zoned btrfs deployments. ## 6. Manual review recommendation **NO MANUAL CHECK NEEDED** This is a DoS-only deadlock in a specialized filesystem configuration, with no evidence of memory corruption, privilege escalation, information disclosure, or network exposure. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: btrfs: zoned: fix deadlock between metadata writeback and transaction commit [ Upstream Commit: 18577e77c2c8adaadf1f7c6e9bcd1c0b14e5dcdd Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=18577e77c2c8adaadf1f7c6e9bcd1c0b14e5dcdd Changed files: fs/btrfs/zoned.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=18577e77c2c8adaadf1f7c6e9bcd1c0b14e5dcdd ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74572 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74572 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:H The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.5 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).