CVE-2024-42295 in Linux
Summary
by MITRE • 08/17/2024
In the Linux kernel, the following vulnerability has been resolved:
nilfs2: handle inconsistent state in nilfs_btnode_create_block()
Syzbot reported that a buffer state inconsistency was detected in nilfs_btnode_create_block(), triggering a kernel bug.
It is not appropriate to treat this inconsistency as a bug; it can occur if the argument block address (the buffer index of the newly created block) is a virtual block number and has been reallocated due to corruption of the bitmap used to manage its allocation state.
So, modify nilfs_btnode_create_block() and its callers to treat it as a possible filesystem error, rather than triggering a kernel bug.
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Analysis
by VulDB Data Team • 02/01/2026
The vulnerability identified as CVE-2024-42295 affects the Linux kernel's nilfs2 filesystem implementation and represents a critical issue in how the kernel handles buffer state inconsistencies during block creation operations. This flaw resides in the nilfs_btnode_create_block() function which is responsible for managing the creation of new blocks within the nilfs2 filesystem's B-tree node structure. The vulnerability was discovered through automated testing by syzbot, which detected an unexpected buffer state inconsistency that would typically trigger a kernel panic or bug report. The nilfs2 filesystem, designed for journaling and providing atomic file system operations, employs a bitmap-based allocation system to track block usage and manage virtual block numbers, making it susceptible to corruption scenarios that can lead to inconsistent states.
The technical flaw stems from the improper handling of virtual block numbers that have been reallocated due to bitmap corruption within the filesystem's allocation management system. When the nilfs_btnode_create_block() function encounters a scenario where the argument block address represents a virtual block number that has already been reallocated, the system should recognize this as a legitimate filesystem error condition rather than an internal kernel bug. The function's current implementation fails to distinguish between genuine kernel-level inconsistencies and recoverable filesystem corruption states, causing the kernel to panic when encountering valid but problematic allocation scenarios. This behavior violates the principle of graceful error handling and system resilience, as the kernel should be able to recover from filesystem corruption rather than crashing entirely.
The operational impact of this vulnerability extends beyond simple system crashes to potentially compromise data integrity and availability in systems utilizing nilfs2 filesystems. When triggered, the vulnerability can cause unexpected kernel panics that result in system downtime and potential data loss, particularly in environments where continuous operation is critical. The flaw affects systems running Linux kernels that include the nilfs2 filesystem implementation and could be exploited by attackers who can manipulate filesystem allocation states to trigger the condition, or could occur naturally due to hardware failures or power interruptions during filesystem operations. The vulnerability particularly impacts systems where nilfs2 is used as the primary filesystem, such as embedded systems, network attached storage devices, or any environment where the nilfs2 journaling filesystem is deployed, as these systems may experience the corruption scenarios that trigger the specific code path.
The resolution for this vulnerability involves modifying the nilfs_btnode_create_block() function and its callers to properly handle allocation state inconsistencies as filesystem errors rather than kernel-level bugs. This change aligns with the principle of fault tolerance and graceful degradation, ensuring that the filesystem can continue operating even when encountering corrupted allocation states. The fix implements proper error handling that recognizes the legitimate scenario of virtual block number reallocation due to bitmap corruption and treats it as a recoverable filesystem condition. This approach follows established security practices for filesystem implementations and aligns with the common security principle that operating systems should not crash due to corrupted data in storage systems, but should instead handle such conditions gracefully. The mitigation strategy ensures that systems using nilfs2 filesystems maintain operational stability even when facing allocation corruption scenarios, thereby reducing the attack surface and improving overall system reliability.
This vulnerability maps to CWE-122 in the Common Weakness Enumeration, which covers "Heap Overflow" and related buffer management issues, though the specific manifestation here involves buffer state inconsistencies rather than traditional overflow conditions. The issue also relates to ATT&CK technique T1490, which covers "Inhibit System Recovery" through filesystem corruption or damage, as the kernel panic behavior could be leveraged to disrupt system availability. From a security perspective, this vulnerability represents a denial-of-service risk that could be amplified in environments where filesystem stability is critical, and the fix ensures that the system maintains its resilience against filesystem corruption scenarios while preserving the integrity of the underlying data structures.