CVE-2024-43820 in Linux
Summary
by MITRE • 08/17/2024
In the Linux kernel, the following vulnerability has been resolved:
dm-raid: Fix WARN_ON_ONCE check for sync_thread in raid_resume
rm-raid devices will occasionally trigger the following warning when being resumed after a table load because DM_RECOVERY_RUNNING is set:
WARNING: CPU: 7 PID: 5660 at drivers/md/dm-raid.c:4105 raid_resume+0xee/0x100 [dm_raid]
The failing check is: WARN_ON_ONCE(test_bit(MD_RECOVERY_RUNNING, &mddev->recovery));
This check is designed to make sure that the sync thread isn't registered, but md_check_recovery can set MD_RECOVERY_RUNNING without the sync_thread ever getting registered. Instead of checking if MD_RECOVERY_RUNNING is set, check if sync_thread is non-NULL.
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Analysis
by VulDB Data Team • 01/21/2026
The vulnerability identified as CVE-2024-43820 affects the Linux kernel's device mapper raid implementation and represents a false positive warning condition that can occur during raid device resumption operations. This issue manifests specifically within the dm-raid subsystem where device mapper raid devices may occasionally trigger kernel warnings when being resumed after table load operations. The warning originates from a problematic check in the raid_resume function located at drivers/md/dm-raid.c line 4105, creating a situation where legitimate operational states are incorrectly flagged as potential issues.
The technical flaw stems from an improper conditional check within the kernel's raid management code where the system verifies whether MD_RECOVERY_RUNNING is set using the WARN_ON_ONCE macro. This particular check is intended to ensure that sync threads are not registered when they shouldn't be, but the implementation contains a logical error that fails to account for legitimate scenarios where md_check_recovery can set MD_RECOVERY_RUNNING without actually registering a sync_thread. The fundamental issue lies in the assumption that MD_RECOVERY_RUNNING being set necessarily indicates an invalid sync thread registration state, when in fact this flag can be set during normal recovery operations without corresponding thread registration.
The operational impact of this vulnerability manifests as spurious kernel warnings that can clutter system logs and potentially obscure genuine operational issues that administrators might encounter when monitoring system health. While the warning itself does not indicate a functional failure or security compromise, it creates noise in system monitoring and debugging processes, potentially leading to confusion during troubleshooting activities. The warning appears specifically during resume operations of dm-raid devices after table loading, suggesting that the issue is triggered by specific sequence of operations rather than general system instability. This false positive behavior can complicate security monitoring and incident response procedures where system administrators rely on clean warning logs to identify actual problems requiring attention.
The fix implemented addresses the root cause by modifying the conditional check from testing the MD_RECOVERY_RUNNING bit to verifying whether the sync_thread pointer is non-NULL. This change aligns the validation logic with the actual operational requirements of the raid subsystem, ensuring that warnings are only triggered when there are legitimate concerns about sync thread registration rather than when the system is operating normally. This modification follows established kernel development practices for avoiding false positives in diagnostic checks and aligns with the principle of only warning about conditions that actually represent problematic states rather than merely anomalous but harmless situations. The solution effectively resolves the issue by using a more accurate indicator of the actual condition being validated.
This vulnerability relates to CWE-704 in the Common Weakness Enumeration which covers incorrect type conversion or cast, and also connects to ATT&CK technique T1562.001 which involves disabling or modifying system protection mechanisms. While not directly a security vulnerability, the improper warning generation can impact system integrity monitoring and may interfere with automated security tools that rely on clean system log analysis. The fix demonstrates proper kernel development methodology for ensuring diagnostic checks accurately reflect actual system conditions rather than creating spurious alerts that could mask real security issues or operational problems in monitoring systems. The resolution maintains system stability while eliminating the misleading warning messages that could otherwise complicate system administration and security operations.