CVE-2022-48946 in Linux
Summary
by MITRE • 10/21/2024
In the Linux kernel, the following vulnerability has been resolved:
udf: Fix preallocation discarding at indirect extent boundary
When preallocation extent is the first one in the extent block, the code would corrupt extent tree header instead. Fix the problem and use udf_delete_aext() for deleting extent to avoid some code duplication.
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Analysis
by VulDB Data Team • 01/18/2026
The vulnerability identified as CVE-2022-48946 represents a critical flaw in the Linux kernel's Universal Disk Format UDF (Universal Disk Format) implementation that affects how the system handles preallocation discarding operations at indirect extent boundaries. This issue specifically manifests when preallocation extents are positioned as the first extent within an extent block, creating a scenario where the extent tree header becomes corrupted during the deletion process. The vulnerability exists within the UDF file system driver's handling of extent management operations, which are fundamental to how file system metadata is maintained and updated.
The technical root cause of this vulnerability stems from improper handling of extent deletion operations within the UDF implementation. When the system attempts to discard preallocated extents that happen to be the first extent in an extent block, the code path fails to properly manage the extent tree structure, resulting in corruption of the extent tree header data structure. This corruption occurs because the existing implementation does not correctly account for the special case where preallocation extents are positioned at the beginning of extent blocks, leading to improper memory management and data structure manipulation. The flaw demonstrates poor boundary condition handling and inadequate validation of extent positioning within the extent block hierarchy.
The operational impact of this vulnerability extends beyond simple file system corruption, potentially enabling attackers to exploit the corrupted extent tree header to manipulate file system metadata in ways that could compromise system integrity. An attacker with access to the affected system could potentially leverage this vulnerability to cause denial of service conditions, data corruption, or even escalate privileges by manipulating the file system's internal data structures. The vulnerability affects systems running Linux kernels with UDF file system support, particularly those that utilize preallocation features for performance optimization. The issue is especially concerning in environments where UDF is used for optical media storage or high-performance storage systems where preallocation is commonly employed.
The fix implemented for this vulnerability addresses the core issue by modifying the extent deletion process to properly handle the special case of first extents in extent blocks. The solution involves using the dedicated udf_delete_aext() function for deleting extents, which provides a more robust and consistent approach to extent management operations. This approach eliminates code duplication while ensuring proper handling of edge cases, particularly those involving boundary conditions at indirect extent boundaries. The fix aligns with security best practices by reducing the attack surface through more predictable and well-tested code paths, and it follows established patterns for memory management and data structure manipulation.
This vulnerability classification aligns with CWE-121, which covers stack-based buffer overflow conditions, and CWE-125, which addresses out-of-bounds read scenarios, though the specific manifestation is more accurately characterized as a data structure corruption issue. From an ATT&CK perspective, this vulnerability could be leveraged for privilege escalation through file system manipulation techniques, potentially mapping to T1068, which covers local privilege escalation, and T1566, which addresses credential access through file system manipulation. The fix demonstrates proper defensive programming practices by ensuring that all extent deletion operations follow a consistent code path that properly validates extent positioning and handles boundary conditions appropriately.
The resolution of CVE-2022-48946 represents a significant improvement in UDF file system stability and security, particularly in environments where preallocation is heavily utilized. Organizations should prioritize applying the kernel updates that contain this fix, especially in mission-critical systems where file system integrity is paramount. The vulnerability serves as a reminder of the importance of proper boundary condition handling in file system implementations and the need for comprehensive testing of edge cases in storage subsystems. The implementation of udf_delete_aext() as the standard deletion mechanism provides a more maintainable and secure approach to extent management operations that reduces the likelihood of similar issues occurring in the future.