From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-93237][MODERATE 7.0] LoongArch: Add DIRECT_MAP_PHYSMEM_END definition Date: Thu, 24 Sep 2026 13:19:48 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-93237 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: unknown X-AL-KERNEL-Commit: ab275a23b4d9f04ca6c2f5f6a3246194e045a761 List-Id: CVE: CVE-2026-93237 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: LoongArch: Add DIRECT_MAP_PHYSMEM_END definition Commit: ab275a23b4d9f04ca6c2f5f6a3246194e045a761 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ab275a23b4d9f04ca6c2f5f6a3246194e045a761 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93237 Analysis date: Thu, 24 Sep 2026 13:19:48 -0400 ActionableScore: 5 ActionableScore lower bound: unknown Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-93237 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93237 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-2026-93237 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-93237 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-190;CWE-682;*CWE-787;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'An incorrect physical memory search limit on LoongArch can allow get_free_mem_region or mhp_get_pluggable_range to select a ZONE_DEVICE range outside the vmemmap covered physical address space. The resulting address wraparound in vmemmap_populate can map the memmap range into low memory and silently corrupt kernel page tables. The direct observed impact includes crashes and failures during device memory initialization, while page table corruption may also permit confidentiality or integrity impact if an attacker can influence the affected allocation path. For the CVSS the PR:L value is used for the paranoid score because access to accelerator or device memory management may be delegated to a local user or service account in some deployments. Exploitation still requires a vulnerable LoongArch CPU configuration with fewer physical address bits, a compatible ZONE_DEVICE driver, and a triggering device memory operation, so AC:H is appropriate. The issue is not network reachable. Impact is at least a local denial of service and in the worst defensible case may include privilege escalation through page table corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) SKIP CVE-2026-93237 UNKNOWN SKIP No affected files built, so skip this CVE NO - - unknown MAYBE READ OOB INIT LEAK KERNEL_PANIC_PLUS_UAF HARDWARE LINUS KPANIC MEMORY KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 PrimitiveClass=CLASS_B RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO 1. ActionableScore * Raw conservative score: 1 * Conservative score: 5 * Raw paranoid score: 1 * Paranoid score: 5 * Applied manual-review safety floor: 1 -> 5 because the patch establishes concrete corruption of active kernel page tables, while trigger reachability and resulting exploitation leverage remain unresolved. * Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**:: 2. Signal breakdown * +1 Constrained kernel overwrite. An out-of-range ZONE_DEVICE region makes `vmemmap_populate()` wrap the memmap mapping into low memory and corrupt page tables. The destination and payload are not shown to be attacker-selectable. * +1 Privileged kernel/device-management memory corruption path. The corrupted objects are active MMU page tables, not passive diagnostics or bookkeeping. * +1 Reliable kernel crash / strong DoS. The supplied evidence documents a crash in `memmap_init_zone_device()`, and page-table corruption independently supports fatal kernel failure. * -2 Rare hardware-only exposure. Exploitation requires affected LoongArch hardware with `cpu_pabits` smaller than the compile-time physical-space limit and a path creating a suitable ZONE_DEVICE region. * No additional Availability point was awarded because the documented crash and fatal consequences of page-table corruption are the same availability effect. * No strong corruption or LPE bonus was awarded because attacker-directed target selection, attacker-controlled contents, arbitrary write, controlled page-table modification, or a practical privilege-escalation chain is not established. * No Confidentiality or Integrity bonus was awarded. Page-table corruption is concrete, but useful unauthorized access or modification by an attacker is not demonstrated. * No remote-reachability, local-unprivileged-trigger, or namespace bonus was awarded. * This is not a UAF, repeated release, refcount mutation, or RCU lifetime defect. UAF floors and repeated-release rules do not apply. 3. Reachability analysis The vulnerable operation occurs while selecting and populating a physical range for ZONE_DEVICE or memory-hotplug use. The documented instance involves amdkfd during device-memory initialization, but the supplied context does not show whether an ordinary user, delegated accelerator service, VMM, or only a host administrator can initiate the complete range-allocation and population sequence. The prior analysis suggests delegated device access as a possibility, but it does not establish that such access reaches `get_free_mem_region()` or `vmemmap_populate()` below host-admin privilege. Therefore `HostAdminRequired` remains `UNKNOWN`, with no privilege penalty beyond the hardware restriction and no local-user bonus. No user-namespace capability path is identified. `NamespaceScopedPrivilege` is therefore `UNKNOWN`. The issue is not network reachable. It requires affected LoongArch hardware, a physical-address-width mismatch, and a compatible ZONE_DEVICE or memory-hotplug path. There is no race requirement. 4. Primitive and severity interpretation The exact primitive is an incorrectly bounded physical-range search followed by address wraparound during vmemmap population. This installs mappings in low memory and silently corrupts active kernel page tables. This is broader than a warning, invalid read, or ordinary device-local failure. It is a concrete Class B kernel-corruption primitive affecting high-value MMU state. It is not Class A because the evidence does not establish attacker-controlled contents, directed target selection, arbitrary kernel read or write, controlled semantic reinterpretation, or a demonstrated privilege-escalation chain. The demonstrated consequences are device-memory initialization failure and kernel crash. Potential confidentiality, integrity, or privilege-escalation consequences remain speculative unless manual analysis proves that a below-host-admin actor can trigger the allocation and meaningfully influence the resulting mappings. `ImportantCandidate=YES` because active page-table corruption is too significant to classify automatically as an ordinary crash-only issue while reachability and exploitation leverage remain unresolved. `AutoDowngradeAllowed=NO` because automatic closure would discard a concrete high-value kernel-corruption primitive requiring call-path and attacker-control analysis. 5. One-sentence report phrase An incorrect LoongArch physical-memory search limit can make vmemmap population wrap into low memory and corrupt active kernel page tables, causing a kernel crash and requiring manual analysis of device-path reachability and possible exploitation leverage. 6. Manual review recommendation MANUAL CHECK REQUIRED Determine who can invoke the complete ZONE_DEVICE allocation path on affected systems, whether accelerator users can retrigger it, which page-table entries are overwritten, and whether the resulting mappings provide controlled access rather than only a crash. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: LoongArch: Add DIRECT_MAP_PHYSMEM_END definition Commit: ab275a23b4d9f04ca6c2f5f6a3246194e045a761 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ab275a23b4d9f04ca6c2f5f6a3246194e045a761 Commit description: get_free_mem_region() and mhp_get_pluggable_range() bound their search to DIRECT_MAP_PHYSMEM_END. LoongArch does not define it, so the fallback in include/linux/mm.h applies: under CONFIG_SPARSEMEM_VMEMMAP it is (1ULL << MAX_PHYSMEM_BITS) - 1, a compile-time constant that does not adapt to the CPU's physical address space bits (cpu_pabits, probed from CPUCFG1). The vmemmap window only covers physical space below 2^(cpu_pabits+1) (i.e. VMEMMAP_SIZE), so on CPUs with fewer physical address bits than MAX_PHYSMEM_BITS the fallback allows get_free_mem_region() to return a ZONE_DEVICE region outside the vmemmap window; vmemmap_populate() then wraps the memmap range around and maps it into low memory, silently corrupting the page tables. The same search also picked the top-of- address-space region that crashed memmap_init_zone_device() with amdkfd on Loongson-3C6000 in 6.16 [1]; the commit 2969b42 ("LoongArch/mm: align vmemmap to maximal folio size") keeps that region in bounds on current Loongson-3C6000 configs, but CPUs with smaller cpu_pabits (e.g. the Loongson-2K series) are still affected. Define DIRECT_MAP_PHYSMEM_END as the vmemmap-covered physical range, (1ULL << (cpu_pabits + 1)) - 1, capped at (1ULL << MAX_PHYSMEM_BITS) - 1 under CONFIG_SPARSEMEM, similar to the commit f3336b4 ("riscv: mm: Define DIRECT_MAP_PHYSMEM_END"). [1] https://lore.kernel.org/amd-gfx/20250814032153.227285-1-jeffbai@aosc.io/ Cc: stable@vger.kernel.org # v6.13+ Signed-off-by: Han Gao Signed-off-by: Huacai Chen Signed-off-by: Greg Kroah-Hartman Changed files: include/linux/mm.h arch/loongarch/include/asm/pgtable.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=ab275a23b4d9f04ca6c2f5f6a3246194e045a761 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-93237 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93237 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: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: unknown 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).