CVE-2024-35808 in Linux
Summary
by MITRE • 05/17/2024
In the Linux kernel, the following vulnerability has been resolved:
md/dm-raid: don't call md_reap_sync_thread() directly
Currently md_reap_sync_thread() is called from raid_message() directly without holding 'reconfig_mutex', this is definitely unsafe because md_reap_sync_thread() can change many fields that is protected by 'reconfig_mutex'.
However, hold 'reconfig_mutex' here is still problematic because this will cause deadlock, for example, commit 130443d60b1b ("md: refactor idle/frozen_sync_thread() to fix deadlock").
Fix this problem by using stop_sync_thread() to unregister sync_thread, like md/raid did.
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Analysis
by VulDB Data Team • 07/21/2025
The vulnerability described in CVE-2024-35808 resides within the Linux kernel's md (multiple device) subsystem, specifically affecting the device mapper raid implementation. This issue manifests in the md/dm-raid module where improper synchronization mechanisms lead to potential race conditions and system instability. The problem occurs during the processing of RAID messages where the md_reap_sync_thread() function is invoked directly from raid_message() without proper locking mechanisms, creating a dangerous scenario that violates fundamental concurrency control principles.
The technical flaw stems from the direct invocation of md_reap_sync_thread() without acquiring the reconfig_mutex lock that protects critical data structures within the RAID subsystem. This function modifies numerous fields that are safeguarded by the reconfig_mutex, making the direct call pattern inherently unsafe and susceptible to data corruption. The vulnerability represents a classic concurrency violation where unprotected access to shared resources can lead to inconsistent states and unpredictable behavior. According to CWE-362, this constitutes a race condition vulnerability where multiple threads access shared data concurrently without proper synchronization, potentially leading to system crashes or data integrity issues.
The operational impact of this vulnerability extends beyond simple system instability to potentially compromise data integrity in RAID configurations. When the md_reap_sync_thread() function executes without proper mutex protection, it can modify critical RAID metadata structures while other threads may be accessing the same data, leading to memory corruption or inconsistent RAID state management. This type of vulnerability is particularly dangerous in production environments where RAID arrays are actively used for data storage and redundancy. The potential for deadlock scenarios further compounds the risk, as the fix must carefully balance the need for proper synchronization with avoiding circular dependency issues that could render the system unresponsive.
The proposed solution addresses this by implementing stop_sync_thread() to properly unregister the sync_thread, following patterns established in the md/raid subsystem. This approach avoids the direct function call while maintaining proper synchronization through established kernel mechanisms. The fix references commit 130443d60b1b which documented similar deadlock issues in the md subsystem, indicating that this vulnerability is part of a broader class of synchronization problems that require careful handling of thread management and resource cleanup. The mitigation strategy aligns with ATT&CK technique T1486, which involves data destruction through system resource manipulation, though in this case the primary risk is system instability rather than direct data corruption. Organizations should prioritize updating their Linux kernel implementations to address this vulnerability, particularly those running RAID configurations that may be exposed to concurrent access patterns that trigger the problematic code path.