CVE-2026-80868 in Linux
Summary
by MITRE • 09/04/2026
In the Linux kernel, the following vulnerability has been resolved:
ntfs3: Allocate iomap inline_data using alloc_page
This fixes a BUG reported in iomap_write_end_inline: iomap_inline_data_valid checks that the inline_data fits within a page. If the inline_data is allocated with kmemdup there's no guarantee that it's page-aligned, so the check sometimes fails. Allocate it with alloc_page to ensure it's page-aligned.
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Analysis
by VulDB Data Team • 09/05/2026
The ntfs3 filesystem driver in the Linux kernel contained a memory allocation flaw within its handling of inline data structures during write operations. Specifically, the function iomap_write_end_inline relies on the helper routine iomap_inline_data_valid to verify that the allocated inline_data buffer fits entirely within a single page boundary. This validation is critical because subsequent memory access patterns assume strict alignment and size constraints relative to page boundaries. The vulnerability arose from the use of kmemdup for allocating this specific data structure. While kmemdup is efficient for general-purpose kernel memory allocation, it does not guarantee that the returned pointer will be aligned to a page boundary or that the allocated block will respect the physical page limits required by the iomap subsystem logic.
This lack of alignment guarantees led to intermittent failures in the validation check within iomap_inline_data_valid. When inline data exceeded certain size thresholds or when memory fragmentation resulted in non-aligned allocations, the kernel would detect an invalid state and trigger a BUG condition. This typically manifests as a kernel panic or oops, causing immediate system instability and potential denial of service for systems relying on ntfs3 mounted volumes. The issue is particularly relevant during file write operations where inline data expansion occurs, affecting userspace applications that interact with NTFS-formatted storage devices through the Linux VFS layer.
From a vulnerability classification perspective, this defect aligns with CWE-120 Buffer Copy without Checking Size of Input in C and related memory management errors such as CWE-789 Uncontrolled Memory Allocation. The root cause is a failure to ensure proper alignment constraints required by lower-level kernel subsystems, which falls under the broader category of improper resource validation. In terms of attack vector classification via MITRE ATT&CK for Enterprise or ICS, this represents an availability impact resulting from software errors rather than malicious exploitation in most cases, though it could potentially be leveraged in local denial-of-service scenarios if triggered by crafted filesystem images or specific workload patterns that force inline data allocation near page boundaries.
The resolution involves replacing the kmemdup call with alloc_page for the iomap_inline_data structure. The alloc_page function explicitly guarantees that the returned memory is aligned to a page boundary and corresponds to a single physical page, thereby satisfying the assumptions made by iomap_inline_data_valid. This change ensures that the inline data buffer remains within valid bounds during write operations, preventing the validation failure and subsequent kernel panic. System administrators should apply this patch or update their Linux kernels to versions containing this fix to maintain stability when using ntfs3 drivers with large files or specific allocation patterns. Regular monitoring of system logs for BUG messages related to iomap can help identify affected systems prior to remediation.