CVE-2026-93230 in Linux
Summary
by MITRE • 09/24/2026
In the Linux kernel, the following vulnerability has been resolved:
mm/hugetlb: initialize gigantic bootmem hugepage struct pages earlier
Gigantic bootmem HugeTLB pages are currently initialized from hugetlb_init(), but page_alloc_init_late() runs earlier and walks pageblocks to determine zone contiguity.
If a bootmem HugeTLB region is marked noinit, set_zone_contiguous() can observe still-uninitialized struct pages through __pageblock_pfn_to_page(). This may not trigger an immediate failure, but it can make set_zone_contiguous() compute the wrong zone contiguity state. If extra poisoned-page checks are added in this path, such as PF_POISONED_CHECK() in page_zone_id(), it can also trigger an early boot panic.
Initialize gigantic bootmem HugeTLB struct pages from page_alloc_init_late(), before zone contiguity is evaluated, so later page allocator setup only sees valid struct page state. This also makes the initialization order more natural, as struct pages should be initialized before later code inspects them.
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Analysis
by VulDB Data Team • 09/24/2026
The Linux kernel's memory management subsystem relies on a precise sequence of initialization routines to ensure that data structures are in a consistent and safe state before they are accessed by other components. A specific ordering issue was identified within the HugeTLB subsystem, where gigantic bootmem hugepage struct pages were initialized too late in the boot process. The function hugetlb_init() is responsible for setting up these large memory regions, but it executes after page_alloc_init_late(). This later routine walks through pageblocks to determine zone contiguity, a critical metric used by the kernel's buddy allocator to manage physical memory efficiently. Because of this timing discrepancy, there exists a window where set_zone_contiguous() can inspect struct pages that have not yet been properly initialized if the corresponding HugeTLB region is marked as noinit.
This race condition in initialization order leads to undefined behavior within the zone contiguity calculation logic. When set_zone_contiguous() accesses uninitialized memory via __pageblock_pfn_to_page(), it may compute an incorrect state regarding whether a memory zone is contiguous or fragmented. While this error might not always result in an immediate system crash, it corrupts internal kernel assumptions about memory layout. This corruption can lead to suboptimal memory allocation decisions, potential fragmentation issues later during runtime, and instability under heavy memory pressure. Furthermore, if the kernel configuration includes additional safety checks such as PF_POISONED_CHECK() within page_zone_id(), accessing these uninitialized pages triggers an immediate early boot panic, preventing the system from starting successfully.
From a vulnerability classification perspective, this issue represents a classic initialization race condition that compromises data integrity and system stability. It aligns with CWE-362, which describes concurrent execution issues where shared resources are accessed without proper synchronization or ordering guarantees. In terms of attack surface and operational impact, while not directly exploitable for remote code execution in the traditional sense, it constitutes a denial-of-service vector through early boot failure. This maps to ATT&CK technique T1499, Endpoint Denial of Service, specifically under the sub-technique of resource exhaustion or system instability caused by software flaws. The vulnerability affects systems relying on gigantic HugeTLB pages for high-performance computing or large memory applications, where proper zone contiguity is essential for performance and stability.
The resolution involves reordering the initialization sequence to ensure that gigantic bootmem HugeTLB struct pages are initialized from page_alloc_init_late(), prior to the evaluation of zone contiguity. This change ensures that when set_zone_contiguous() inspects the memory layout, all relevant struct pages contain valid state information. By aligning the initialization order with logical dependencies, the kernel avoids reading garbage data or uninitialized memory regions. This fix not only prevents potential boot panics but also restores correct behavior for zone contiguity calculations, ensuring that the buddy allocator operates on accurate metadata. System administrators and developers should apply this patch to maintain system stability, particularly in environments where gigantic pages are configured with noinit attributes or when strict poisoning checks are enabled during development and testing phases.