From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-89994][MODERATE 7.0] dmaengine: fsl-edma: tracing: no ptr dereference during log output Date: Wed, 16 Sep 2026 08:50:36 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-89994 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 4 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: ef02cd3807f39ae1dbc924788d8fa6a85334c435 List-Id: CVE: CVE-2026-89994 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: dmaengine: fsl-edma: tracing: no ptr dereference during log output Commit: ef02cd3807f39ae1dbc924788d8fa6a85334c435 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ef02cd3807f39ae1dbc924788d8fa6a85334c435 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89994 Analysis date: Wed, 16 Sep 2026 08:50:36 -0400 ActionableScore: 4 ActionableScore lower bound: 3 Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-89994 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89994 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: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-89994 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-89994 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H';*CWE-416;CWE-825;**CWE-476;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.1';DESCR 'The fsl edma trace event stores a pointer to struct fsl_edma_engine in the ring buffer and dereferences it later while formatting the trace output. The referenced engine object may already be freed or otherwise invalid at that time, resulting in a use after free read or a NULL pointer dereference and a kernel crash. Event injection provides a direct local trigger and avoids the need to win a narrow race window. For the CVSS the PR:L in the paranoid score represents systems where tracefs or event injection access is delegated to a restricted service account, container root, or another partially privileged local user. The typical configuration requires administrative tracing privileges and is represented by PR:H in the base score. The issue is not network reachable. Impact is at least local denial of service. Limited confidentiality impact is plausible if stale or reused object data affects the printed offset, but no write primitive or supported privilege escalation path is visible.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) SKIP CVE-2026-89994 UNKNOWN SKIP No affected files built, so skip this CVE NO - - unknown MAYBE TRACE SIMPLEFIX LINUS KPANIC MEMORY - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=3 PrimitiveClass=CLASS_B RealUAF=YES HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 3 * Conservative score: 3 * Raw paranoid score: 4 * Paranoid score: 4 * No floor or cap was applied. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown Conservative signals: * +2 Real UAF / lifetime violation. The trace record retains `struct fsl_edma_engine *` beyond the guaranteed lifetime of the engine and later dereferences it in `TP_printk`. * +1 Reliable kernel crash. The commit provides a direct trace-event injection sequence that causes an invalid pointer dereference. * Total: 3. Paranoid additional signal: * +1 Confidentiality plausible. A stale `edma->membase` value is read and influences a value printed into the trace buffer. This is only a limited and transformed potential disclosure, not a substantial kernel read primitive. * Total: 4. Not awarded: * No strong or structured stale-object leverage. The stale path consumes only `membase` for pointer arithmetic and does not traverse pointers, invoke callbacks, or modify the object. * No controlled reclaim, attacker-shaped replacement object, arbitrary write, directed read, or privilege-escalation primitive is demonstrated. * No remote-reachability point. Triggering occurs through local tracefs controls. * No extra Availability point. The same kernel crash is counted only once. * No Integrity point. The vulnerable operation performs a stale read, not a write. * No repeated-release/refcount point. There is no second `put`, `free`, `release`, or refcount mutation through the stale pointer. * FLOOR 5 was not applied because this is a shallow trace-formatting dereference with crash as the demonstrated result and no meaningful post-lifetime mutation or reuse leverage. 3. Reachability analysis The demonstrated trigger writes to the trace-event `inject` control and then reads the trace buffer. These tracefs operations are normally tightly permissioned, but the supplied evidence does not establish whether host-admin privilege is mandatory in every affected deployment or whether tracing access has been delegated. Therefore `HostAdminRequired=UNKNOWN`, with no speculative privilege penalty. Tracefs permissions are not shown to be obtainable through an attacker-created user or network namespace, so `NamespaceScopedPrivilege=UNKNOWN`. The path is local and not network-triggerable. The affected trace event and fsl-edma code must be present. Event injection may avoid dependence on a naturally occurring device-removal timing window, but availability of the tracepoint can depend on kernel configuration or module loading. No rare-hardware penalty is applied because the supplied reproducer uses event injection and does not establish that physical DMA hardware is required for the crash. This is not scored as a hard race. Injection supplies a direct trigger without requiring the attacker to win a narrow timing window. 4. Primitive and severity interpretation The exact primitive is a stale post-lifetime pointer read. A ring-buffer record stores an engine pointer, and later trace formatting dereferences `edma->membase` after the engine may have been destroyed. The engine is an active structured kernel object, but the vulnerable use is shallow and constrained. Only one field is read for log formatting. There is no broader active-object processing, callback dispatch, refcount mutation, or object traversal. This is `CLASS_B` because a genuine lifetime violation exists. It is not `CLASS_A` because controlled reclaim, directed corruption, arbitrary read or write, and privilege escalation are not established. It is not reduced to `CLASS_C` because the commit directly identifies a potentially freed object being dereferenced. The demonstrated consequence is a local kernel crash. A limited transformed disclosure through the printed offset is a defensible paranoid concern, but meaningful sensitive-data exposure is not established. `ImportantCandidate=NO` because the stale operation lacks independently useful exploitation leverage beyond the crash and limited possible trace disclosure. `AutoDowngradeAllowed=YES` because this is a constrained stale-read path without repeated lifetime mutation, controlled replacement, authorization bypass, or unresolved strong corruption primitive. Likely operational severity is ordinary-to-borderline Moderate, with manual confirmation of tracefs privilege boundaries and disclosure behavior recommended. 5. One-sentence report phrase A trace record can dereference an expired fsl edma engine pointer while formatting log output, allowing a local tracefs user to crash the kernel and potentially expose a limited value derived from stale memory. 6. Manual review recommendation MANUAL CHECK RECOMMENDED Confirm whether affected deployments delegate trace-event injection or trace-buffer access below host-admin privilege and whether stale `membase` values can disclose useful kernel information. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: dmaengine: fsl-edma: tracing: no ptr dereference during log output Commit: ef02cd3807f39ae1dbc924788d8fa6a85334c435 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ef02cd3807f39ae1dbc924788d8fa6a85334c435 Commit description: The fsl edma events store a pointer to a struct fsl_edma_engine in the ringbuffer and dereference it when a log entry is printed. At this time, the pointer may no longer be valid. Event injection can be used to trigger a crash: $ cd /sys/kernel/tracing $ echo 'value = 0' > events/fsl_edma/edma_writeb/inject $ cat trace The log output needs only edma->membase. Add a membase field at the end of the event and use the new field for log output. Keep the existing fields for backward compatibility. Fixes: 11102d0 ("dmaengine: fsl-edma: add trace event support") Cc: stable@vger.kernel.org Reviewed-by: Steven Rostedt Signed-off-by: Martin Kaiser Reviewed-by: Frank Li Link: https://patch.msgid.link/20260718130024.341243-1-martin@kaiser.cx Signed-off-by: Vinod Koul Signed-off-by: Greg Kroah-Hartman Changed files: drivers/dma/fsl-edma-trace.h 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=ef02cd3807f39ae1dbc924788d8fa6a85334c435 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-89994 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89994 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:L/PR:H/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:L/I:N/A:H The Best / paranoid CVSS score: 6.1 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: 3 Paranoid ActionableScore: 4 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: YES 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).