From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-93205][MODERATE REGULAR] iommu/arm-smmu-v3: Manage teardown with devm Date: Thu, 24 Sep 2026 13:13:16 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-93205 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: unknown X-AL-KERNEL-Commit: 981686f4137760a16a03c5193f11d85133533f93 List-Id: CVE: CVE-2026-93205 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: iommu/arm-smmu-v3: Manage teardown with devm Commit: 981686f4137760a16a03c5193f11d85133533f93 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=981686f4137760a16a03c5193f11d85133533f93 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93205 Analysis date: Thu, 24 Sep 2026 13:13:16 -0400 ActionableScore: 3 ActionableScore lower bound: unknown 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-2026-93205 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93205 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: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-93205 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-93205 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:H/UI:N/S:U/C:H/I:H/A:H';*CWE-416;*CWE-664;CWE-362;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '6.4';DESCR 'An ARM SMMU v3 teardown ordering flaw can free the IOPF queue before the event queue IRQ is released. A later event queue interrupt can then access the freed IOPF queue and cause a kernel use-after-free. Triggering requires removal reset or unbind of an ARM SMMU device while IOPF support and the relevant IRQ path are active. For the CVSS the PR:H is used because reliable triggering normally requires administrative control over device lifecycle operations. The issue is not directly network reachable. Impact is at least a local denial of service through a kernel crash. In the worst case the confirmed kernel use-after-free may provide confidentiality or integrity impact and should be reviewed manually. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) YES INIT UAF HARDWARE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=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: 3 * Paranoid score: 3 * Final recommended bucket: **Borderline / manual review recommended**:: The supplied patch establishes a real teardown UAF, but does not establish attacker-controlled replacement, post-free contents, repeated lifetime mutation, arbitrary read or write, privilege escalation, or a direct below-host-admin trigger. 2. Signal breakdown Positive signals: * +2 Real UAF / active lifetime violation. `arm_smmu_device_remove()` can free `evtq.iopf` before devm releases the event queue IRQ. The commit explicitly states that the IRQ handler uses the freed IOPF queue. * +1 Reliable kernel crash / strong DoS. A later IRQ handler access to freed kernel memory can cause an Oops or kernel crash. Negative signals: * No host-admin penalty applied. Device removal, reset, unbind, and the relevant IOPF setup are not fully resolved in the supplied context. Host-admin-equivalent control may be required for reliable triggering, but this is not established sufficiently to apply a negative score. * No hard-race penalty applied. The unsafe ordering is concrete. The patch does not establish that the IRQ timing window is exceptionally narrow, externally uncontrollable, or non-repeatable. * No rare-hardware penalty applied. ARM SMMU v3 and IOPF are platform and configuration dependent, but the supplied evidence does not establish a physical-only or genuinely rare attacker requirement. Important non-awarded signals: * Controlled reclaim or controlled object replacement is not demonstrated. * Arbitrary or directed kernel write is not demonstrated. * Attacker-controlled post-free queue contents are not demonstrated. * Structured stale-object exploitation leverage is not awarded. The visible evidence establishes a teardown IRQ access, but not meaningful attacker influence over reused queue fields, callbacks, pointers, offsets, or object replacement. * Weak LPE concern is not awarded merely because the bug is a UAF. * No additional Availability point is awarded because the same stale IRQ access already accounts for the crash or DoS consequence. * Confidentiality and integrity points are not awarded. A UAF alone does not establish disclosure or unauthorized modification. * The later Tegra241 CMDQV CMD_SYNC UAF mentioned in the commit message is explicitly a subsequent issue and is not scored as part of this patch. 3. Reachability analysis The immediate vulnerable sequence is: `arm_smmu_device_remove()` `-> iopf_queue_free(evtq.iopf)` `-> remove returns` `-> devm later unwinds IRQ resources` `-> event queue IRQ handler accesses evtq.iopf` The visible patch does not establish that an ordinary local user can initiate the full removal or teardown sequence. Typical device unbind, reset, driver reload, and platform-device lifecycle operations are often administrative operations, but the exact interface and capability checks for this platform-specific SMMU lifecycle are not included. Therefore HostAdminRequired is UNKNOWN rather than YES. Namespace-scoped reachability is also unresolved. The affected ARM SMMU device is platform-owned hardware state. The patch provides no evidence that a user or network namespace can create, remove, reset, or otherwise fully control the affected SMMU instance and its IRQ teardown sequence. There is no direct network path. Firmware or device events may contribute to the IRQ timing, but no attacker-controlled firmware or external-device input path is established by the supplied evidence. The affected path requires ARM SMMU v3 operation with an allocated IOPF queue and event queue IRQ activity. These are relevant deployment prerequisites, but they are not scored as a negative hardware penalty because the evidence does not establish that they are rare or impossible for a relevant attacker environment. 4. Primitive and severity interpretation The exact primitive is a real post-free access to an `iopf_queue` from an event queue IRQ handler after `arm_smmu_device_remove()` frees that queue. This is a kernel lifetime violation and therefore CLASS_B. The stale object is an active queue used by IRQ processing, but the demonstrated stale use occurs in a teardown ordering path. The patch does not show that an attacker can reclaim the freed queue with attacker-shaped data, force a replacement object at the same address, control fields consumed by the IRQ handler after reuse, or cause a callback or function pointer dispatch. This is not a repeated release or refcount case. The patch does not show a first `put` followed by a second lifetime-mutating `put`, free, or refcount operation on the same dangling reference. Therefore the concrete repeated release or refcount signal and the related FLOOR 5 rule do not apply. The demonstrated consequence is kernel crash or denial of service. A stronger confidentiality, integrity, or privilege-escalation consequence is theoretically possible for some kernel UAF classes, but it is not supported by a concrete mechanism in the supplied patch. The issue should receive manual review because it is a real IRQ-context UAF in IOMMU driver state, but it is not currently a strong Important candidate. AutoDowngradeAllowed is YES because the available evidence supports a constrained teardown UAF with crash or DoS impact and does not establish meaningful unresolved exploitation leverage beyond the stale dereference. 5. One-sentence report phrase An ARM SMMU v3 teardown ordering flaw can free an IOPF queue before its event queue IRQ handler is released, allowing a later IRQ to access freed memory and cause a local kernel crash or denial of service. 6. Manual review recommendation MANUAL CHECK RECOMMENDED Reason: the patch directly establishes a kernel IRQ-context use-after-free, but the supplied context does not establish attacker-controlled reuse, arbitrary memory access, a below-host-admin trigger, or a practical privilege-escalation path. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: iommu/arm-smmu-v3: Manage teardown with devm Commit: 981686f4137760a16a03c5193f11d85133533f93 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=981686f4137760a16a03c5193f11d85133533f93 Commit description: arm_smmu_device_remove() manually frees the IOPF queue, destroys the vmid_map and disables the device, while the IRQs and queues are devm managed. devm unwinds only after remove() returns, so the cleanup runs in the wrong order. The IOPF queue is freed before the event-queue IRQ whose handler uses it. Manage all of it with devm so the unwind order is correct. Free the IOPF queue and vmid_map via devm actions, and disable the device from one registered after arm_smmu_device_reset(). This is also a prerequisite for fixing a Tegra241 CMDQV CMD_SYNC use-after-free in the subsequent patch. Cc: stable@vger.kernel.org Suggested-by: Jason Gunthorpe Reviewed-by: Nicolin Chen Signed-off-by: Shameer Kolothum Reviewed-by: Jason Gunthorpe Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman Changed files: drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.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=981686f4137760a16a03c5193f11d85133533f93 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-93205 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93205 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:H/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 6.4 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: 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).