CVE-2024-36932 in Linux
Summary
by MITRE • 05/30/2024
In the Linux kernel, the following vulnerability has been resolved:
thermal/debugfs: Prevent use-after-free from occurring after cdev removal
Since thermal_debug_cdev_remove() does not run under cdev->lock, it can run in parallel with thermal_debug_cdev_state_update() and it may free the struct thermal_debugfs object used by the latter after it has been checked against NULL.
If that happens, thermal_debug_cdev_state_update() will access memory that has been freed already causing the kernel to crash.
Address this by using cdev->lock in thermal_debug_cdev_remove() around the cdev->debugfs value check (in case the same cdev is removed at the same time in two different threads) and its reset to NULL.
Cc :6.8+ # 6.8+
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Analysis
by VulDB Data Team • 05/30/2024
This vulnerability exists within the linux kernel's thermal subsystem where a use-after-free condition can occur during concurrent operations involving debugfs character device management. The flaw specifically affects the thermal_debugfs object handling mechanism that manages debugfs interfaces for thermal zone monitoring. When the thermal_debug_cdev_remove() function executes, it operates outside of the cdev->lock protection context, creating a race condition scenario where this removal function can execute simultaneously with thermal_debug_cdev_state_update() function. This parallel execution creates a situation where the thermal_debugfs object structure gets freed by the removal function while the state update function is still referencing it, leading to memory access violations that result in kernel crashes.
The technical implementation of this vulnerability stems from improper synchronization mechanisms within the kernel's device management framework. The cdev->lock mechanism that should protect critical sections during concurrent access is not being utilized in the thermal_debug_cdev_remove() function, despite being available and required for safe operations. This design flaw allows for a classic race condition where multiple threads can simultaneously attempt to access and modify the same debugfs object structure. The vulnerability specifically manifests when the thermal_debug_cdev_state_update() function performs a NULL check on the cdev->debugfs value and then proceeds to access the structure, while the thermal_debug_cdev_remove() function has already freed that same structure in parallel execution. This creates a scenario where the kernel attempts to dereference freed memory, resulting in immediate system instability and potential denial of service conditions.
The operational impact of this vulnerability extends beyond simple system crashes to potentially compromise the entire system stability and availability. Since thermal management is critical for hardware protection and system reliability, a crash in this subsystem can lead to uncontrolled hardware shutdowns or overheating conditions that may cause permanent damage to system components. The vulnerability affects kernel versions 6.8 and later, making it particularly concerning for systems that rely on the latest kernel security updates. Attackers could potentially exploit this race condition to cause persistent system instability, especially in environments where thermal monitoring is continuously active and under heavy concurrent load. The vulnerability also represents a significant concern for embedded systems and server environments where thermal management is critical for maintaining system integrity and preventing hardware failures.
The mitigation strategy for this vulnerability involves implementing proper locking mechanisms around the critical sections of the thermal_debug_cdev_remove() function. By ensuring that cdev->lock is properly utilized during the removal process, the kernel can guarantee that no concurrent access occurs to the debugfs object structure during its destruction phase. This fix aligns with established security best practices and follows the principle of least privilege by ensuring that all shared resource access is properly synchronized. The solution addresses the underlying CWE-362 weakness category related to race conditions and improper locking mechanisms. Additionally, this fix contributes to the broader ATT&CK framework by preventing potential privilege escalation paths through kernel memory corruption vulnerabilities. System administrators should prioritize applying this kernel patch to maintain system stability and prevent potential exploitation scenarios that could lead to unauthorized system access or service disruption. The fix also demonstrates proper adherence to kernel development practices that emphasize thread safety and concurrent access protection in device driver implementations.