CVE-2025-40325 in Linux
Summary
by MITRE • 04/18/2025
In the Linux kernel, the following vulnerability has been resolved:
md/raid10: wait barrier before returning discard request with REQ_NOWAIT
raid10_handle_discard should wait barrier before returning a discard bio which has REQ_NOWAIT. And there is no need to print warning calltrace if a discard bio has REQ_NOWAIT flag. Quality engineer usually checks dmesg and reports error if dmesg has warning/error calltrace.
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Analysis
by VulDB Data Team • 05/24/2026
The vulnerability identified as CVE-2025-40325 resides within the Linux kernel's md/raid10 subsystem, specifically addressing a race condition in discard request handling that could lead to data integrity issues and system instability. This flaw manifests when the raid10_handle_discard function processes discard bio requests with the REQ_NOWAIT flag, creating a scenario where the subsystem fails to properly synchronize with underlying storage operations before acknowledging the discard request. The issue stems from inadequate barrier synchronization mechanisms that should ensure all pending operations complete before returning control to the requesting process, potentially allowing data inconsistencies in RAID10 array configurations.
The technical implementation flaw occurs in the md/raid10 driver's discard handling logic where the function does not enforce proper barrier completion before returning discard requests marked with REQ_NOWAIT. This flag typically indicates that the request should be processed without waiting for completion, but in the context of RAID10 arrays, this optimization can lead to race conditions when underlying storage devices are still processing previous operations. The vulnerability represents a classic case of insufficient synchronization primitives in concurrent storage operations, where the absence of proper memory barriers or completion waiting mechanisms creates a window for data corruption or inconsistent array states.
The operational impact of this vulnerability extends beyond simple performance degradation to potentially compromise data integrity within RAID10 storage configurations. When discard requests are processed without proper barrier synchronization, there exists a risk that subsequent read or write operations might access stale data or encounter inconsistent array states, particularly in high-concurrency environments where multiple storage operations occur simultaneously. System administrators may observe subtle data corruption issues or unexpected behavior in applications relying on consistent storage state, while the warning calltrace generation in dmesg creates false positives that can obscure legitimate error conditions.
The resolution addresses this issue by implementing mandatory barrier waiting before returning discard requests with the REQ_NOWAIT flag, ensuring that all pending operations complete before acknowledging the discard request. This change eliminates the need for warning calltrace generation when processing such requests, as the synchronization mechanism now properly handles the concurrent access patterns. The fix aligns with security best practices for storage subsystems and follows established patterns for preventing race conditions in concurrent I/O operations. This vulnerability demonstrates the importance of proper synchronization in storage drivers and represents a CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization) type issue, where inadequate locking or barrier mechanisms create security and reliability concerns.
Mitigation strategies should focus on applying the kernel patch that implements proper barrier synchronization before discard request completion, ensuring that all RAID10 arrays are updated to versions containing this fix. System administrators should monitor dmesg output for any remaining warning messages that might indicate incomplete patch application or other related storage subsystem issues. The fix also emphasizes the need for comprehensive testing of storage subsystems under concurrent workloads to identify potential race conditions, aligning with ATT&CK technique T1490 (Inhibit System Recovery) by preventing potential data corruption that could lead to system recovery failures. Organizations should implement regular kernel update procedures to ensure all storage subsystem vulnerabilities are addressed promptly, particularly in mission-critical environments where data integrity is paramount.