CVE-2025-38701 in Linux
Summary
by MITRE • 09/04/2025
In the Linux kernel, the following vulnerability has been resolved:
ext4: do not BUG when INLINE_DATA_FL lacks system.data xattr
A syzbot fuzzed image triggered a BUG_ON in ext4_update_inline_data() when an inode had the INLINE_DATA_FL flag set but was missing the system.data extended attribute.
Since this can happen due to a maiciouly fuzzed file system, we shouldn't BUG, but rather, report it as a corrupted file system.
Add similar replacements of BUG_ON with EXT4_ERROR_INODE() ii ext4_create_inline_data() and ext4_inline_data_truncate().
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Analysis
by VulDB Data Team • 02/10/2026
The vulnerability identified as CVE-2025-38701 represents a critical flaw in the Linux kernel's ext4 file system implementation that could lead to system instability and potential denial of service conditions. This issue manifests when the ext4_update_inline_data() function encounters an inode with the INLINE_DATA_FL flag set but without the corresponding system.data extended attribute. The flaw stems from inadequate error handling within the file system's inline data management routines, where the kernel's defensive programming approach of using BUG_ON() instead of proper error reporting mechanisms creates a path for system crashes when encountering malformed file system structures.
The technical root cause of this vulnerability lies in the improper handling of file system metadata consistency checks within the ext4 implementation. When an inode is marked with the INLINE_DATA_FL flag, the ext4 subsystem expects the presence of a system.data extended attribute to maintain file system integrity. However, due to fuzzing activities or other malformed conditions, this assumption can be violated, leading to a kernel panic. The vulnerability specifically affects the ext4_update_inline_data() function which lacks proper validation before attempting to access the expected extended attribute, resulting in a kernel BUG_ON() macro triggering a system crash instead of gracefully handling the inconsistency.
This vulnerability impacts the overall operational stability of Linux systems relying on ext4 file systems, particularly those exposed to untrusted file system inputs or fuzzing attacks. The potential for denial of service exists when maliciously crafted file system images trigger the BUG_ON condition, causing system crashes that could be exploited in targeted attacks against file system services or in environments where system availability is critical. The flaw also represents a broader concern for file system robustness and fault tolerance, as it demonstrates inadequate error handling for edge cases in extended attribute management.
The fix implemented for this vulnerability addresses the core issue by replacing BUG_ON() calls with EXT4_ERROR_INODE() macros in three key functions: ext4_update_inline_data(), ext4_create_inline_data(), and ext4_inline_data_truncate(). This change ensures that when inline data inconsistencies are detected, the system properly reports corrupted file system conditions rather than crashing the kernel. The solution aligns with the principle of graceful degradation and follows established patterns for error handling in the Linux kernel's file system subsystem. The fix also demonstrates proper adherence to CWE-248 standards for uncaught exceptions and maintains consistency with ATT&CK framework techniques related to system stability and denial of service conditions, as it prevents attackers from exploiting file system inconsistencies to cause system crashes.
The mitigation strategy for this vulnerability involves updating to the patched kernel version containing the corrected implementation, which provides proper error handling for inline data file system inconsistencies. System administrators should prioritize applying this patch, particularly in environments where ext4 file systems are used with untrusted inputs or where the risk of fuzzing attacks is significant. The fix also emphasizes the importance of proper extended attribute validation and error reporting in file system implementations, serving as a model for similar vulnerabilities in other file system components that may exhibit similar patterns of improper error handling.