From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53164][MODERATE REGULAR] iommu/dma: Do not try to iommu_map a 0 length region in swiotlb Date: Thu, 25 Jun 2026 04:53:44 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53164 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: 4 X-AL-KERNEL-ActionableScore-Lower: 1 X-AL-KERNEL-Commit: ab61c990a87d084f5565ee70340543e3a5394697 List-Id: CVE: CVE-2026-53164 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: iommu/dma: Do not try to iommu_map a 0 length region in swiotlb Commit: ab61c990a87d084f5565ee70340543e3a5394697 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ab61c990a87d084f5565ee70340543e3a5394697 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53164 Analysis date: Thu, 25 Jun 2026 04:53:44 -0400 ActionableScore: 4 ActionableScore lower bound: 1 Actionable bucket: Borderline manual review recommended / Ordinary Moderate unless deployment uses panic_on_warn or delegated storage passthrough Manual review required: YES Summary: A zero length SWIOTLB middle mapping can cause iommu_map failure followed by error unwind from the wrong offset, corrupting DMA mapping state and later triggering WARN_ON during mapping destruction on affected Thunderbolt NVMe passthrough paths. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53164 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53164 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-2026-53164 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';CWE-754;CWE-755;CWE-703;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.8';DESCR 'A zero length middle segment in iommu_dma_iova_link_swiotlb can make the IOMMU mapping path reject an iommu_map request and then run error unwind from the wrong offset. This corrupts DMA mapping state and later triggers WARN_ON during mapping destruction. The known trigger involves forced SWIOTLB with oddly aligned buffers, often seen with some Thunderbolt NVMe drives and smartctl style passthrough commands. For the CVSS the PR:L is used in the paranoid score because a local low privileged process may be able to reach a delegated storage management path in some deployments, although reliable triggering usually needs passthrough access or device management rights. The issue is not reachable over an IP network and is local or hardware adjacent in practice. Impact is at least denial of service via WARN_ON or crash when panic_on_warn is enabled, with limited confidentiality or integrity impact kept only for paranoid triage because DMA mapping state is corrupted.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended / Ordinary Moderate unless deployment uses panic_on_warn or delegated storage passthrough (with actual score 3) YES SIMPLEFIX DMAorINTERRUPT HARDWARE MEMORY DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 YES NO guess ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=1 ## 1. ActionableScore * Conservative score: 1 * Paranoid score: 4 * Final recommended bucket: **Borderline manual review recommended / Ordinary Moderate unless deployment uses panic_on_warn or delegated storage passthrough**:: ## 2. Signal breakdown Paranoid score signals: * +1 Firmware-mediated external influence. The known trigger involves specific Thunderbolt NVMe devices, forced SWIOTLB, and oddly aligned buffers. * +1 Weak/indirect corruption candidate. The wrong unwind offset can corrupt DMA/IOMMU mapping bookkeeping, but the patch does not show UAF, OOB write, arbitrary write, or attacker-controlled payload. * +1 Privileged kernel/device-management memory corruption path. The corrupted state is in the trusted IOMMU/DMA mapping path. * +1 Availability impact realistic. The observed failure is WARN_ON during mapping destruction, with stronger DoS relevance when panic_on_warn is enabled or if the broken mapping path disrupts device I/O. * +1 Important filesystem/storage path. The issue is in DMA mapping for storage I/O, observed with NVMe passthrough. * -1 Corruption primitive constrained. The corruption appears to be metadata/bookkeeping state with no demonstrated attacker-controlled overwrite target or payload. Conservative score signals: * +1 Weak DMA mapping state corruption. * +1 Availability concern from WARN_ON or possible panic_on_warn. * -1 Constrained metadata-only corruption. * -1 to -2 Typical triggering requires privileged storage passthrough or device-management access, often root or CAP_SYS_RAWIO-like privileges. ## 3. Reachability analysis The realistic trigger is local and hardware-adjacent, not IP-network reachable. It is reported with Thunderbolt NVMe devices that force SWIOTLB and with oddly aligned passthrough buffers from smartctl-like commands. In typical deployments, issuing NVMe passthrough commands requires administrative or storage-management privileges. A paranoid interpretation keeps PR lower only for environments where storage management is delegated to a reduced-privilege service, container, or operator account. ## 4. Severity interpretation This behaves more like an ordinary Moderate or borderline actionable Moderate than an Important-class vulnerability. The patch describes corrupted DMA mapping state, which deserves manual attention, but it does not demonstrate a strong memory corruption primitive such as UAF, OOB write, arbitrary write, reclaim control, or page ownership violation. Realistic impact is mainly WARN_ON or local DoS, with higher concern only in panic_on_warn or delegated device-management environments. ## 5. One-sentence report phrase A zero length SWIOTLB middle mapping can cause iommu_map failure followed by error unwind from the wrong offset, corrupting DMA mapping state and later triggering WARN_ON during mapping destruction on affected Thunderbolt NVMe passthrough paths. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Manual review is recommended because the bug affects IOMMU/DMA mapping state in a storage path, but it should not be auto-escalated to Important without evidence of a concrete memory corruption primitive beyond constrained mapping bookkeeping corruption. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: iommu/dma: Do not try to iommu_map a 0 length region in swiotlb Commit: ab61c990a87d084f5565ee70340543e3a5394697 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ab61c990a87d084f5565ee70340543e3a5394697 Commit description: iommu_dma_iova_link_swiotlb() processes a mapping that is unaligned in three parts, the head, middle and trailer. If the middle is empty because there are no aligned pages it will call down to iommu_map() with a 0 size which the iommupt implementation will fail as illegal. It then tries to do an error unwind and starts from the wrong spot corrupting the mapping so the eventual destruction triggers a WARN_ON. Check for 0 length and avoid mapping and use offset not 0 as the starting point to unlink. This is frequently triggered by using some kinds of thunderbolt NVMe drives that trigger forced SWIOTLB for unaligned memory. NVMe seems to pass in oddly aligned buffers for the passthrough commands from smartctl that hit this condition. Cc: stable@vger.kernel.org Fixes: 433a762 ("dma-mapping: Implement link/unlink ranges API") Reported-by: Mark Lord Signed-off-by: Jason Gunthorpe Reviewed-by: Christoph Hellwig Reviewed-by: Leon Romanovsky Reviewed-by: Samiullah Khawaja Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/0-v1-8536728bc89f+469-swiotlb_warn_jgg@nvidia.com Signed-off-by: Greg Kroah-Hartman Changed files: drivers/iommu/dma-iommu.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=ab61c990a87d084f5565ee70340543e3a5394697 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53164 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53164 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:N/I:N/A:L The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 5.8 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: 1 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: 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).