From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-93229][LOW] nfsd: add missing read barrier to rpc_status_get dumpit seqcount retry Date: Thu, 24 Sep 2026 11:59:35 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-93229 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: 0 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: f501f2f4ec1d2dfe39e21c98630314074a9b30b0 List-Id: CVE: CVE-2026-93229 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: nfsd: add missing read barrier to rpc_status_get dumpit seqcount retry Commit: f501f2f4ec1d2dfe39e21c98630314074a9b30b0 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f501f2f4ec1d2dfe39e21c98630314074a9b30b0 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93229 Analysis date: Thu, 24 Sep 2026 11:59:35 -0400 ActionableScore: 0 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-2026-93229 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93229 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-2026-93229 LOW https://www.kernelcve.org/list/?q=CVE-2026-93229 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:N';CWE-362;CWE-667;CWE-366;BEST CVSS score: '0';DESCR 'A missing read memory barrier in the nfsd RPC status netlink dump path can allow field reads to be reordered past the sequence counter retry check on weakly ordered architectures such as ARM and POWER. The resulting dump can contain an internally inconsistent snapshot when an RPC request status is modified concurrently. The issue affects diagnostic status accuracy and does not demonstrate a memory safety primitive, privilege escalation, information disclosure, integrity impact, or denial of service. Access to this control plane status interface is typically restricted to an administrative context. The issue is local and is not directly network reachable through NFS request traffic.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) YES DISK SIMPLEFIX NETWORK HARDWARE LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=0 PrimitiveClass=NONE RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 0 * Conservative score: 0 * Raw paranoid score: 0 * Paranoid score: 0 * Final recommended bucket: **Ordinary Moderate**:: No floor or cap was applied. 2. Signal breakdown * +0 No memory corruption primitive. The patch fixes ordering of reads relative to a seqcount style retry check. * +0 No UAF, stale object use, refcount misuse, OOB access, invalid free, or ownership violation is established. * +0 No confidentiality signal. The patch supports an inconsistent diagnostic snapshot, not disclosure of otherwise inaccessible data. * +0 No integrity signal. The netlink dump reads status fields and does not modify protected state. * +0 No availability signal. No crash, lockup, resource exhaustion, or service interruption is shown. * +0 No remote reachability. NFS request traffic does not directly invoke the netlink dump path. * +0 No local unprivileged trigger is established. The exact Generic Netlink access policy and capability namespace checks are not included in the supplied context. * +0 No privilege penalty was applied. Host-admin-equivalent access is not positively established from the supplied patch. * +0 No race difficulty penalty was applied. Weak-memory reordering on ARM or POWER is a relevant condition, but the score is already zero because no security-impacting primitive exists. Important non-awarded signals: * Controlled reclaim, arbitrary write, structured stale-object leverage, and privilege escalation are not demonstrated. * No repeated release or refcount mutation exists. * No crash-only UAF exists because no object lifetime violation is present. * No direct information disclosure path is established. The output may be internally inconsistent, but it remains an intended status-reporting interface. * No manual-review preserving Class B primitive exists. 3. Reachability analysis The affected function is nfsd_nl_rpc_status_get_dumpit, a local Generic Netlink status-dump control-plane path. It is not reached by ordinary incoming NFS RPC traffic, so the issue is not remotely triggerable through the NFS service. The supplied material does not show the Generic Netlink policy, capability checks, or the user namespace against which any capability is evaluated. Therefore host-admin privilege cannot be positively confirmed, and below-host-admin reachability also cannot be confirmed. HostAdminRequired and NamespaceScopedPrivilege are both UNKNOWN. The defect requires concurrent modification of an NFS server request status while a status dump is being generated, and it is relevant on weakly ordered architectures such as ARM and POWER. No special hardware beyond such architecture is required, but the result is limited to an inconsistent diagnostic snapshot. 4. Primitive and severity interpretation The exact primitive is a missing read memory barrier in a hand-written seqcount-like read-side protocol. Without smp_rmb, reads of request-status fields may be reordered after the second rq_status_counter check. The reader can therefore observe matching sequence-counter values while reporting fields that do not belong to one coherent point in time. This is neither active structured-object lifetime misuse nor fixed stale storage. No object is freed, released, replaced, dereferenced after lifetime end, or mutated through stale storage. There is no concrete repeated release or refcount operation. The demonstrated consequence is inaccurate or internally inconsistent RPC status reporting through the diagnostic Netlink dump. A speculative consequence would be operational confusion for an administrator or monitoring tool. The patch does not support kernel crash, DoS, unauthorized state modification, information disclosure beyond the intended interface, authorization bypass, or privilege escalation. PrimitiveClass is NONE. ImportantCandidate is NO because no corruption, lifetime, ownership, semantic reinterpretation, or security-boundary primitive remains unresolved. AutoDowngradeAllowed is YES because this is a correctness issue with no demonstrated security-relevant primitive. 5. One-sentence report phrase A missing read memory barrier in the nfsd RPC status Netlink dump path can produce an internally inconsistent diagnostic status snapshot on weakly ordered architectures, without demonstrating memory corruption, disclosure, privilege escalation, or denial of service. 6. Manual review recommendation NO MANUAL CHECK NEEDED The patch fixes diagnostic snapshot consistency only. No concrete kernel-security primitive or meaningful unresolved exploitation path is established. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: nfsd: add missing read barrier to rpc_status_get dumpit seqcount retry Commit: f501f2f4ec1d2dfe39e21c98630314074a9b30b0 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f501f2f4ec1d2dfe39e21c98630314074a9b30b0 Commit description: The hand-rolled seqcount-like protocol in nfsd_nl_rpc_status_get_dumpit() is missing a read memory barrier (smp_rmb) before its second counter check. The standard kernel read_seqcount_retry() includes smp_rmb() to ensure that all data reads complete before the counter is re-checked. Without this barrier, on weakly-ordered architectures (ARM, POWER), the CPU may reorder field reads past the second counter check, making the retry logic ineffective: it could observe a consistent counter pair while reading fields that have been concurrently modified by the writer. Add smp_rmb() before the second counter check to order the field reads ahead of it, matching the barrier semantics of the standard seqcount read-side. The begin-side smp_load_acquire() already pairs with the smp_store_release() in nfsd_dispatch(); with the smp_rmb() now ordering the field reads, the retry check no longer needs acquire semantics and reads the counter with a plain READ_ONCE(), as read_seqcount_retry() does. Fixes: bd9d6a3 ("NFSD: add rpc_status netlink support") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Jeff Layton [ cel: Use READ_ONCE instead of smp_load_acquire() ] Link: https://patch.msgid.link/20260611-nfsd-testing-v2-2-5b90e276f2d9@kernel.org Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman Changed files: fs/nfsd/nfsctl.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=f501f2f4ec1d2dfe39e21c98630314074a9b30b0 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-93229 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93229 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:H/UI:N/S:U/C:N/I:N/A:N The Best / paranoid CVSS score: 0 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: 0 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).