CVE-2024-38604 in Linux
Summary
by MITRE • 06/19/2024
In the Linux kernel, the following vulnerability has been resolved:
block: refine the EOF check in blkdev_iomap_begin
blkdev_iomap_begin rounds down the offset to the logical block size before stashing it in iomap->offset and checking that it still is inside the inode size.
Check the i_size check to the raw pos value so that we don't try a zero size write if iter->pos is unaligned.
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Analysis
by VulDB Data Team • 10/05/2025
The vulnerability identified as CVE-2024-38604 resides within the Linux kernel's block device subsystem, specifically in the blkdev_iomap_begin function that handles iomap operations for block devices. This flaw represents a subtle but significant issue in how the kernel manages file system operations and memory mapping for block devices, potentially affecting the integrity of file system operations and data access patterns. The vulnerability stems from an inadequate check during the end-of-file boundary validation process, creating a potential vector for data corruption or access violations when processing file operations near file boundaries.
The technical implementation of this vulnerability involves the improper handling of logical block size alignment within the block device iomap subsystem. When blkdev_iomap_begin processes file operations, it rounds down the offset to the logical block size before storing it in iomap->offset and subsequently validates that this adjusted offset remains within the inode size boundaries. However, the function fails to properly account for the original position value when performing the i_size check, leading to scenarios where aligned offsets might incorrectly pass validation while the actual raw position value falls outside acceptable boundaries. This misalignment creates a condition where zero-sized write operations could be attempted against file positions that should be rejected due to boundary constraints.
The operational impact of this vulnerability extends beyond simple data access issues, potentially enabling attackers to exploit boundary condition checks in file system operations. When iter->pos contains an unaligned value that gets rounded down during offset processing, the system may incorrectly permit operations that should be rejected based on the original position. This creates a window where zero-sized write attempts could be executed against file positions that are technically outside the valid file size range, potentially leading to data corruption, access violations, or other undefined behaviors in the block device subsystem. The vulnerability affects systems running Linux kernels that include the problematic code path, particularly those handling file operations on block devices where precise boundary checking is crucial.
Mitigation strategies for CVE-2024-38604 involve applying the official kernel patches that correct the i_size validation logic to use the raw position value rather than the rounded offset value. System administrators should prioritize updating their Linux kernel versions to include the patched implementation that properly aligns the EOF validation with the original position parameter. The fix addresses the underlying CWE-129 weakness related to improper validation of array indices and input boundaries, ensuring that file system operations respect the actual file size constraints regardless of block alignment considerations. Additionally, monitoring systems should be configured to detect unusual file access patterns or zero-sized operations that might indicate exploitation attempts. Organizations should also implement regular kernel updates and security assessments to maintain protection against similar boundary condition vulnerabilities in the block device subsystem, following established security practices outlined in the ATT&CK framework for kernel-level threats and file system manipulation techniques.