From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-90012][MODERATE 7.0] spi: Fix DMA mapping ownership on partial map failure Date: Wed, 16 Sep 2026 13:16:39 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-90012 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: 5 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: cc8354213ad6bd5fb8cc05a3fa3701188d086626 List-Id: CVE: CVE-2026-90012 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: spi: Fix DMA mapping ownership on partial map failure Commit: cc8354213ad6bd5fb8cc05a3fa3701188d086626 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cc8354213ad6bd5fb8cc05a3fa3701188d086626 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90012 Analysis date: Wed, 16 Sep 2026 13:16:39 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90012 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90012 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-2026-90012 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-90012 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:L/UI:N/S:U/C:L/I:L/A:H';CWE-755;CWE-763;**CWE-476;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A DMA mapping ownership bug in the SPI core can occur when __spi_map_msg sees a partial mapping failure. If RX mapping fails after TX mapping succeeds, tx_sg_mapped can remain set even though TX was already unmapped. If TX mapping fails on a later transfer, mappings from earlier transfers can remain active and later spi_unmap_msg may use a NULL or stale DMA device or release the same mapping twice. This can trigger a kernel oops through a NULL device dereference and may create limited DMA resource ownership risk. For the CVSS the PR:L is used because reliable triggering normally requires local ability to submit SPI transfers or control a local service or device node that can reach the SPI controller. The issue is not network reachable. Impact is at least local denial of service via kernel crash, with conservative limited confidentiality or integrity impact in the paranoid score due to stale device and double unmap behavior.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate (with actual score 5) SKIP CVE-2026-90012 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE NULLPTR DMAorINTERRUPT HARDWARE KPANIC MEMORY - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 PrimitiveClass=CLASS_B RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=REQUIRED AutoDowngradeAllowed=NO 1. ActionableScore * Raw conservative score: 4 * Conservative score: 4. No floor or cap changed it. * Raw paranoid score: 5 * Paranoid score: 5. No floor or cap changed it. * Final recommended bucket: **Actionable Moderate**:: 2. Signal breakdown Conservative signals: * +1 Constrained kernel DMA ownership primitive. The patch establishes inconsistent DMA mapping ownership state where mappings may be released using a NULL or stale device, or the same mapping may be unmapped again. * +1 Active state retirement and unwind bypass. The old error paths returned directly or manually unmapped only part of the state instead of unwinding all active mappings through the normal message unmap path. * +1 Concrete resource or mapping management defect. Earlier DMA mappings can remain active after a later transfer mapping failure, with mapping flags and owner devices out of sync. * +1 Reliable kernel crash or strong DoS. The commit explicitly states that using a NULL device in dma_unmap_sg_attrs can trigger an oops. Paranoid additional signal: * +1 Unresolved DMA ownership corruption leverage. The stale device and double unmap behavior affects DMA/IOMMU ownership state, which is stronger than a pure NULL dereference even though no controlled corruption primitive is demonstrated. Non-awarded signals: * RealUAF not awarded. The evidence shows stale DMA owner state and possible stale device use, but not a directly established heap object use-after-free. * Concrete repeated release/refcount signal not awarded. dma_unmap is a mapping release operation, but the supplied control flow does not establish a classic object lifetime refcount put/free on the exact same dangling object. * First release can end lifetime: not established for a kernel object lifetime reference. * Exact same object reference survives for second lifetime mutation: not established in the repeated-refcount sense. * Second operation mutates lifetime/refcount: not established. It mutates DMA mapping/IOMMU ownership state instead. * FLOOR 5 was not applied as a UAF floor because RealUAF=NO. The paranoid score reaches 5 through DMA ownership risk, not a UAF floor. * Controlled reclaim not demonstrated. * Arbitrary write not demonstrated. * Confidentiality and integrity impact not directly awarded. The limited C/I concern belongs only to paranoid interpretation of DMA ownership risk, not a demonstrated read/write primitive. * Remote reachability not established. * Race penalty not applied. This is an ordered partial failure and unwind bug, not a proven hard timing race. * Extra availability not awarded. The oops is already counted once. 3. Reachability analysis The vulnerable path is in the SPI core during DMA mapping of a spi_message. Triggering requires the ability to submit SPI transfers that use DMA and to hit a partial mapping failure sequence, for example RX mapping failure after TX mapping success or TX mapping failure after earlier transfers were mapped. Below-host-admin reachability is plausible on systems exposing SPI through spidev, device-specific user interfaces, or local services, but the supplied evidence does not prove the complete trigger chain for an ordinary unprivileged user. Therefore HostAdminRequired is UNKNOWN rather than YES or NO. Namespace scoping is not relevant from the supplied patch. SPI devices and DMA mapping ownership are not shown to be controllable through attacker-created namespaces. NamespaceScopedPrivilege=NO. Prior setup exists in the practical sense that an SPI controller/device and DMA-capable transfer path must be present, but this is not scored as a rare hardware penalty. SPI is hardware-specific, but the prompt does not establish rare or physical-only attacker requirements. No network trigger is supported. 4. Primitive and severity interpretation The exact primitive is a DMA mapping ownership and unwind inconsistency. The old code updated cur_tx_dma_dev and cur_rx_dma_dev only after all transfers were mapped. On partial failure, already-created mappings and per-transfer mapped flags could remain inconsistent with the recorded owner devices. This is not a demonstrated heap UAF. It is also not merely passive bookkeeping, because later spi_unmap_msg may actively call DMA unmap code using a NULL or stale device or may release the same DMA mapping twice. PrimitiveClass=CLASS_B because a real kernel ownership/lifetime-management primitive exists in DMA mapping state, but controlled reclaim, arbitrary read/write, callback control, or demonstrated LPE is not established. The demonstrated consequence is kernel oops / DoS through NULL device dereference. The speculative consequence is limited DMA ownership or IOMMU state corruption from stale-device or double-unmap behavior. That unresolved device-memory ownership aspect justifies Actionable Moderate and required manual review, but not a Strong Important score. ImportantCandidate=NO because the patch does not establish controlled memory corruption, privilege escalation, security-boundary bypass, or a strong exploitation primitive. AutoDowngradeAllowed=NO because treating this as an ordinary crash-only NULL dereference would discard the unresolved DMA ownership and double-unmap aspect. 5. One-sentence report phrase A partial DMA mapping failure in the SPI core can leave DMA owner devices and per-transfer mapping flags inconsistent, allowing later cleanup to unmap with a NULL or stale device or double-unmap a mapping, causing a local kernel oops and requiring manual review due to unresolved DMA ownership risk. 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is not only a NULL dereference. The patch establishes stale DMA owner state and possible double unmap of DMA mappings, which is an ownership primitive that should not be automatically closed as ordinary DoS without subsystem review. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: spi: Fix DMA mapping ownership on partial map failure Commit: cc8354213ad6bd5fb8cc05a3fa3701188d086626 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cc8354213ad6bd5fb8cc05a3fa3701188d086626 Commit description: If RX mapping fails after TX mapping succeeds, __spi_map_msg() unmaps TX but leaves tx_sg_mapped set. If TX mapping fails on a later transfer, mappings created for earlier transfers remain active. In both cases, cur_{tx,rx}_dma_dev have not yet been updated because they are assigned only after every transfer has been mapped. The subsequent spi_unmap_msg() may therefore unmap the TX mapping again or release earlier mappings using a NULL or stale device. Using a NULL device can trigger an oops. An empty SG table does not prevent the NULL dereference because dma_unmap_sg_attrs() accesses the device before checking the entry count. Publish both mapping devices before mapping starts and unwind all failures through __spi_unmap_msg(). This clears the mapping flags and releases each mapping once with the device that created it. Publishing the devices before the loop also refreshes them when no transfer needs mapping. No mapping flag is set in that case, so current users do not use the pointers as mapping owners. Fixes: e289df8 ("spi: Rework per message DMA mapped flag to be per transfer") Cc: stable@vger.kernel.org Signed-off-by: Honghui Jiang Reviewed-by: Andy Shevchenko Link: https://patch.msgid.link/20260814031419.43378-2-jiang_hh2019@163.com Signed-off-by: Mark Brown Signed-off-by: Greg Kroah-Hartman Changed files: drivers/spi/spi.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=cc8354213ad6bd5fb8cc05a3fa3701188d086626 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90012 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90012 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:H 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: 4 Paranoid ActionableScore: 5 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).