From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-90008][IMPORTANT] scsi: megaraid_sas: Limit NVMe request size to the PRP chain frame Date: Wed, 16 Sep 2026 14:41:12 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-90008 X-AL-KERNEL-Priority: IMPORTANT X-AL-KERNEL-Severity: IMPORTANT X-AL-KERNEL-Base-Severity: IMPORTANT X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 7 X-AL-KERNEL-ActionableScore-Lower: 6 X-AL-KERNEL-Commit: 4bb34769ef44ab3770b89e4055de6af4a458bec9 List-Id: CVE: CVE-2026-90008 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: YES Patch: scsi: megaraid_sas: Limit NVMe request size to the PRP chain frame Commit: 4bb34769ef44ab3770b89e4055de6af4a458bec9 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4bb34769ef44ab3770b89e4055de6af4a458bec9 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90008 Analysis date: Wed, 16 Sep 2026 14:41:12 -0400 ActionableScore: 7 ActionableScore lower bound: 6 Actionable bucket: Strong Important candidate Manual review required: YES Summary: An out-of-bounds write in megaraid_sas PRP list construction can overrun the command DMA frame during large NVMe I/O, causing kernel crash or corruption of neighbouring in-flight command metadata. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90008 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90008 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: IMPORTANT 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-2026-90008 IMPORTANT https://www.kernelcve.org/list/?q=CVE-2026-90008 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:H/I:H/A:H';*CWE-787;CWE-119;CWE-131;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'An out-of-bounds write can occur in megaraid_sas when megasas_make_prp_nvme builds an NVMe PRP list in cmd sg_frame without bounding the number of entries against the DMA pool buffer size. Large I/O requests on NVMe drives with a large MDTS can require more PRP entries than the chain frame can hold, causing the list to run past the end of the frame. If the next page is unmapped this causes a kernel page fault and denial of service. If the adjacent DMA pool entry is mapped, the overrun can silently corrupt another in-flight command PRP list, which makes this a memory corruption candidate rather than a pure crash bug. For the CVSS the PR:L is used because a local user able to generate large file or block I/O may be able to reach the vulnerable path without full administrative privileges. The issue is not network reachable. Impact is at least local denial of service and in the paranoid case may include confidentiality and integrity impact due to corruption of DMA command metadata.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate (with actual score 7) SKIP CVE-2026-90008 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE DANGER DMAorINTERRUPT HARDWARE KPANIC MEMORY KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHERTHAN5 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=7 ActionableScoreLower=6 PrimitiveClass=CLASS_A RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO ## 1. ActionableScore * Raw conservative score: 6 * Conservative score: 6 * Raw paranoid score: 7 * Paranoid score: 7 * Final recommended bucket: **Strong Important candidate**:: No floor or cap was applied. ## 2. Signal breakdown Conservative signals: * +2 Strong corruption primitive: `megasas_make_prp_nvme()` can write PRP entries past `cmd->sg_frame`, which is a fixed DMA pool buffer. * +1 Reliable kernel crash / strong DoS: the report shows a supervisor write page fault in kernel mode when the overrun reaches an unmapped page. * +1 Local below-host-admin trigger: large file or block I/O can realistically reach the PRP construction path once the affected storage stack exists. * +1 Important storage path: this is in the SCSI/NVMe storage command submission path and can affect in-flight I/O metadata. * +1 DMA descriptor corruption: the commit explicitly states that if the next page is mapped, the overrun can corrupt a neighbouring pool entry, another in-flight command's PRP list. Paranoid additional signal: * +1 Local high-control data-plane aspect: a local user can influence I/O size, alignment, and request pattern, which affects PRP list length and the chance of hitting adjacent in-flight command metadata. Non-awarded signals: * RealUAF not awarded: this is an out-of-bounds write, not a stale lifetime use. * Arbitrary kernel write not awarded: target selection is constrained to adjacent DMA pool memory. * Controlled reclaim not demonstrated. * Remote reachability not established. * Race/timing penalty not applied: this is not a timing race. * Hardware penalty not applied: megaraid_sas hardware is device-specific but not proven rare or physical-attacker-only. * Extra availability point not awarded: the observed crash is already counted. * Confidentiality and integrity are not separately scored as demonstrated consequences, but the active DMA metadata corruption keeps this in CLASS_A and requires review. ## 3. Reachability analysis The vulnerable path is reached through normal block I/O submitted to an NVMe device behind `megaraid_sas`. The trigger depends on a device reporting a large MDTS and on large enough requests after the block layer default increased to 4 MiB. A host administrator is needed to have the affected hardware and storage stack configured, but the complete runtime trigger does not necessarily require host-admin privileges. A normal local user with access to files on the affected filesystem may generate large reads or writes that enter this path. Direct raw block-device access would be more privileged, but file I/O is enough to keep `HostAdminRequired=NO`. This is not namespace-scoped. No network trigger is established. No special race is required. The main environmental prerequisite is affected MegaRAID/NVMe hardware and a request size large enough to exceed the PRP chain frame capacity. ## 4. Primitive and severity interpretation The exact primitive is an out-of-bounds kernel write while building an NVMe PRP list into `cmd->sg_frame`. The buffer size is `instance->max_chain_frame_sz`, but the old limit used firmware-derived `max_io_size` without ensuring that the PRP entries fit in the chain frame. This is active DMA command metadata, not passive bookkeeping. The commit explicitly distinguishes two outcomes: immediate kernel page fault when the overrun reaches unmapped memory, or silent corruption of a neighbouring DMA pool entry when it is mapped. The neighbouring entry may be another in-flight command's PRP list, making this an active descriptor corruption primitive. PrimitiveClass is CLASS_A because the patch establishes a real OOB write into kernel DMA command metadata with possible corruption of another active command descriptor. RealUAF is NO. The demonstrated consequence is kernel crash. The unresolved consequence is whether corrupted PRP metadata can be steered into stronger integrity or confidentiality impact through misdirected device I/O. That possibility is not proven as arbitrary read/write, but it is strong enough to require manual review and prevent automatic downgrade. ImportantCandidate=YES because this is not a pure DoS-only NULL dereference or resource leak. AutoDowngradeAllowed=NO because automatic closure would discard a concrete kernel OOB write affecting active DMA/storage metadata. Likely operational severity: Strong Important candidate, especially on systems where untrusted local users can generate large I/O on affected storage. ## 5. One-sentence report phrase An out-of-bounds write in megaraid_sas PRP list construction can overrun the command DMA frame during large NVMe I/O, causing kernel crash or corruption of neighbouring in-flight command metadata. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: concrete OOB write into DMA command metadata is established, and the commit explicitly notes silent corruption of another in-flight PRP list. ## 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: scsi: megaraid_sas: Limit NVMe request size to the PRP chain frame Commit: 4bb34769ef44ab3770b89e4055de6af4a458bec9 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4bb34769ef44ab3770b89e4055de6af4a458bec9 Commit description: megasas_make_prp_nvme() builds a command's PRP list in cmd->sg_frame, a DMA pool buffer of instance->max_chain_frame_sz bytes, spending one entry per NVMe page of the transfer plus one per page of the buffer for the chain pointer. The loop runs until the transfer is described and never checks the buffer bound. max_hw_sectors comes straight from the MDTS the firmware reports for the drive. On drives with a large MDTS the only thing keeping the list inside the buffer was the block layer default of 1280 KiB, which needs 320 entries, which fit into a 4 KiB frame as that holds 512. But since commit 9b8b848 ("block: Increase BLK_DEF_MAX_SECTORS_CAP") that default is 4 MiB, and such a transfer needs 1025 entries, so the list runs a full page past the end of the frame: sd 1:0:1:0: [sdb] tag#630 page boundary ptr_sgl: 0x00000000ba62d13f BUG: unable to handle page fault for address: ff663bcb81e7c000 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page RIP: 0010:megasas_build_and_issue_cmd_fusion+0xeaa/0x1870 [megaraid_sas] If the page after the frame happens to be mapped, the overrun does not fault but silently corrupts the neighbouring pool entry, which is another in-flight command's PRP list. Cap max_hw_sectors at what the chain frame can describe, less one page for transfers that do not start on a page boundary and so need one entry more. This is the megaraid_sas counterpart of commit 04631f5 ("scsi: mpt3sas: Limit NVMe request size to 2 MiB"), but derives the limit from max_chain_frame_sz rather than hardcoding it. Cc: stable@vger.kernel.org Fixes: 9b8b848 ("block: Increase BLK_DEF_MAX_SECTORS_CAP") Reported-by: Lukasz Magiera Closes: https://lore.kernel.org/all/GPhsSM0vkgyIrs0DIZ62qeUZX7X4RxwQXVKiuvMx-lHQVSPDxpztUyQOGS0xikqvJ-Z94hMV-dW_5KN_0CX2hsfV7kTf_t0MTf6vdAAaSEc=@magik.net/ Reported-by: Mira Limbeck Closes: https://lore.kernel.org/all/d171cc76-bf25-48ce-b482-d344669dfc24@proxmox.com/ Suggested-by: Martin K. Petersen Link: https://lore.kernel.org/all/yq17bmzd5jr.fsf@ca-mkp.ca.oracle.com/ Signed-off-by: Thomas Lamprecht Closes: https://lore.kernel.org/linux-scsi/20260827182106.535D61F000E9@smtp.kernel.org Link: https://patch.msgid.link/20260827175743.734593-1-t.lamprecht@proxmox.com Signed-off-by: Martin K. Petersen (Oracle) Signed-off-by: Greg Kroah-Hartman Changed files: drivers/scsi/megaraid/megaraid_sas_base.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=4bb34769ef44ab3770b89e4055de6af4a458bec9 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90008 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90008 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:L/I:L/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 7 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: 6 Paranoid ActionableScore: 7 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: IMPORTANT KPANIC detected for this report: YES Published priority for this report (same as in Subject): IMPORTANT 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).