From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-93269][LOW] ext4: fix circular lock dependency in ext4_ext_migrate [ Upstream Date: Thu, 24 Sep 2026 18:35:46 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-93269 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: 2 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 452950461241dfed8b1d32e94b227db38c99c5af List-Id: CVE: CVE-2026-93269 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: ext4: fix circular lock dependency in ext4_ext_migrate [ Upstream Commit: 452950461241dfed8b1d32e94b227db38c99c5af Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=452950461241dfed8b1d32e94b227db38c99c5af Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93269 Analysis date: Thu, 24 Sep 2026 18:35:46 -0400 ActionableScore: 2 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-2026-93269 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93269 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-2026-93269 LOW https://www.kernelcve.org/list/?q=CVE-2026-93269 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-667;**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 lock inversion in ext4 extent migration can occur when EXT4_IOC_MIGRATE holds s_writepages_rwsem and releases a temporary inode while orphan cleanup holds sb_internal and attempts writeback. The two execution paths can wait on each other and deadlock, stalling ext4 filesystem operations and potentially making the affected filesystem unavailable. For the CVSS the PR:L rating is used because a local process must be able to invoke migration on an accessible writable ext4 file. The issue is not network reachable and no memory corruption or privilege escalation primitive is indicated. The base impact is limited availability loss. The paranoid score treats availability as high if the deadlock affects a critical filesystem.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) YES WRITE OOB DEADLOCK DANGER DISK RACE HARDWARE LINUS SYZBOT 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=2 PrimitiveClass=NONE RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 2 * Conservative score: 2 * Raw paranoid score: 2 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate**:: The conservative and paranoid scores are identical because the patch establishes a lock-order deadlock and filesystem availability impact, but does not establish a lifetime violation, memory corruption, authorization bypass, or a distinct higher-impact consequence. 2. Signal breakdown Positive signals: * +1 Reliable strong DoS. The documented lock inversion can produce a real deadlock between `s_writepages_rwsem` and `sb_internal`, blocking the involved ext4 operations. * +1 Important filesystem path. The affected paths include ext4 extent migration, inode eviction, orphan cleanup during mount, and writeback synchronization. A deadlock can make the affected filesystem or mount operation unavailable. No double-counting was applied. The second point represents the operational importance of the affected ext4 filesystem and writeback path, not another instance of the same deadlock. Important non-awarded signals: * No Real UAF. `iput(tmp_inode)` is moved after releasing a lock. The inode is not used after destruction through a stale pointer. * No concrete repeated release or refcount mutation exists. There is one `iput(tmp_inode)` in the corrected cleanup sequence, not two lifetime operations on a dangling reference. * No controlled reclaim, object replacement, arbitrary kernel write, OOB access, type confusion, or callback control is demonstrated. * No confidentiality or integrity impact is established. * No remote reachability is established. The trigger is a local filesystem ioctl and mount or orphan-cleanup interaction. * No local unprivileged trigger point is awarded. The visible patch does not establish the exact permission checks governing the complete `EXT4_IOC_MIGRATE` operation. * No host-admin penalty is applied. The supplied code does not positively establish that host-admin-equivalent privilege is required for the entire trigger. * No hard-race penalty is applied. The scenario requires concurrent execution during orphan cleanup, but the supplied evidence does not establish that the timing is materially one-shot, externally uncontrollable, or impractically unreliable. * No extra Availability point is awarded. The filesystem deadlock is already counted as the reliable DoS consequence. 3. Reachability analysis The direct trigger path begins with a local caller of `EXT4_IOC_MIGRATE`, which executes `ext4_ext_migrate()`. The deadlock additionally requires concurrent orphan cleanup during an ext4 mount, where `ext4_evict_inode()` holds or requests the freeze-protection lock and proceeds toward writeback. The supplied diff does not include the `EXT4_IOC_MIGRATE` ioctl dispatch and permission checks. Therefore, it does not positively establish whether an ordinary file owner, a delegated capability holder, or a host administrator can complete the full trigger. `HostAdminRequired=UNKNOWN` is appropriate. No evidence establishes that the complete operation can be performed inside an attacker-created user or mount namespace. `NamespaceScopedPrivilege=UNKNOWN` is appropriate. The required orphan-cleanup condition is not a normal packet or remote input path. It may depend on mounting an ext4 filesystem with pending orphan cleanup and overlapping that work with extent migration. This is a local operational concurrency condition, not a demonstrated remote or cross-namespace attack path. 4. Primitive and severity interpretation The primitive is a lock-order inversion: `EXT4_IOC_MIGRATE` -> obtains `s_writepages_rwsem` in write mode -> calls `iput(tmp_inode)` -> inode eviction requests `sb_internal` Concurrent orphan cleanup: `ext4_evict_inode` -> holds or requests `sb_internal` -> calls ext4 writeback -> waits for `s_writepages_rwsem` in read mode This is a deadlock and filesystem availability defect, not a memory-lifetime defect. The temporary inode is not an active stale structured object after free. The patch does not show a post-free dereference, repeated refcount mutation, stale object reuse, corruption of ext4 metadata, cross-file ownership violation, or attacker-controlled write. PrimitiveClass is `NONE` because no meaningful corruption, lifetime, ownership, authorization, or similar security primitive is established. The demonstrated consequence is denial of service through blocked ext4 mount, writeback, or filesystem operations. Privilege escalation, data disclosure, integrity impact, and kernel memory corruption are speculative and unsupported. `ImportantCandidate=NO` because the patch establishes a constrained lock dependency with an availability consequence only. `AutoDowngradeAllowed=YES` because no unresolved corruption or security-boundary primitive would be discarded by handling this as an ordinary Moderate issue. Likely operational severity is Moderate or lower depending on whether the affected ext4 filesystem is critical. Systems that rely on the affected filesystem for boot, service data, or persistent storage may prioritize the fix operationally, but that does not create an Important-class exploitation primitive. 5. One-sentence report phrase An ext4 lock inversion between extent migration and orphan cleanup can deadlock filesystem writeback and mount related operations, causing local denial of service without demonstrated memory corruption or privilege escalation. 6. Manual review recommendation NO MANUAL CHECK NEEDED The patch directly documents a lock dependency deadlock with an availability-only consequence. No UAF, repeated release, corruption, authorization bypass, remote attack path, or unresolved exploitation primitive is established. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ext4: fix circular lock dependency in ext4_ext_migrate [ Upstream Commit: 452950461241dfed8b1d32e94b227db38c99c5af Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=452950461241dfed8b1d32e94b227db38c99c5af Changed files: fs/ext4/migrate.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=452950461241dfed8b1d32e94b227db38c99c5af ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-93269 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93269 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: unknown Paranoid ActionableScore: 2 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).