CVE-2024-40977 in Linux
Summary
by MITRE • 07/12/2024
In the Linux kernel, the following vulnerability has been resolved:
wifi: mt76: mt7921s: fix potential hung tasks during chip recovery
During chip recovery (e.g. chip reset), there is a possible situation that kernel worker reset_work is holding the lock and waiting for kernel thread stat_worker to be parked, while stat_worker is waiting for the release of the same lock. It causes a deadlock resulting in the dumping of hung tasks messages and possible rebooting of the device.
This patch prevents the execution of stat_worker during the chip recovery.
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Analysis
by VulDB Data Team • 09/28/2024
The vulnerability identified as CVE-2024-40977 represents a critical deadlock condition within the Linux kernel's wireless subsystem, specifically affecting the mt7921s driver used in MediaTek wireless chipsets. This issue manifests during the chip recovery process, which occurs when the wireless hardware requires reset operations due to errors or system conditions. The flaw exists in the synchronization mechanisms between kernel worker threads that manage the wireless chip's operational state. The vulnerability arises from improper lock management during the chip reset sequence, creating a circular dependency between two distinct kernel threads responsible for different aspects of wireless chip monitoring and recovery operations.
The technical implementation of this vulnerability involves a classic deadlock scenario where the reset_work kernel worker thread holds a critical lock while attempting to wait for the stat_worker kernel thread to complete its operations and enter a parked state. Concurrently, the stat_worker thread is simultaneously waiting for the same lock that reset_work possesses, creating an impossible circular wait condition. This synchronization failure occurs within the wireless driver's recovery logic, specifically affecting the mt76 driver family's implementation for mt7921s chipset models. The underlying cause relates to improper thread coordination during hardware state transitions, where the driver fails to properly manage the lifecycle of monitoring threads during critical recovery operations. This type of deadlock condition falls under the CWE-362 category of concurrent execution using shared resources without proper synchronization, and represents a violation of the principle of lock ordering and thread lifecycle management.
The operational impact of this vulnerability extends beyond simple system performance degradation to potentially cause complete system instability and device reboots. When the deadlock condition occurs, the kernel's hung task detection mechanism triggers, logging extensive debugging information about the blocked threads and their call stacks. This detection mechanism is designed to identify threads that have been stuck for extended periods, typically indicating system hangs or resource contention issues. The system's response to this deadlock situation often results in forced reboots as the kernel attempts to recover from the unresponsive state, leading to potential data loss and service interruptions for users relying on wireless connectivity. The vulnerability affects devices running Linux kernels with the mt76 wireless driver, particularly those using MediaTek mt7921s chipset implementations, which are commonly found in various networking equipment and embedded systems.
Mitigation strategies for this vulnerability require immediate kernel updates that implement the patch addressing the specific deadlock condition in the mt7921s driver. The proposed fix prevents the execution of the stat_worker thread during chip recovery operations by ensuring that monitoring activities are suspended while reset operations are in progress. System administrators should prioritize applying the relevant kernel security patches from their distribution vendors, particularly focusing on kernel versions containing the mt76 driver fixes for MediaTek chipsets. Organizations maintaining wireless infrastructure should implement monitoring solutions to detect potential hung task conditions and establish automated alerting for systems showing signs of thread contention or resource deadlock situations. The fix aligns with the ATT&CK framework's defensive techniques for maintaining system stability and preventing denial of service conditions through proper thread management and resource allocation practices. Additionally, system administrators should consider implementing hardware-specific recovery procedures and ensure that wireless subsystems are properly tested for compatibility with kernel updates to prevent similar synchronization issues in other driver implementations.