Overview
CVE-2025-40224 identifies a vulnerability within the cgbc-hwmon driver of the Linux kernel. This flaw stems from a missing NULL check after a memory allocation attempt using devm_kzalloc(). If the memory allocation fails, the subsequent dereferencing of the NULL pointer could result in a kernel crash, leading to a denial-of-service condition. A patch has been released to address this issue, adding the necessary NULL check to ensure proper error handling.
Technical Details
The cgbc-hwmon driver is responsible for monitoring hardware components. The vulnerability lies in how the driver handles memory allocation for sensor data. Specifically:
- The driver uses
devm_kzalloc()to allocate memory. - Before the patch, there was no check to verify if the allocation succeeded (i.e., if the returned pointer is NULL).
- If
devm_kzalloc()fails, it returns a NULL pointer. - The driver then attempts to dereference this NULL pointer without validation, leading to a kernel panic.
The patch introduces a simple but crucial check: after the devm_kzalloc() call, the code now verifies if the returned pointer is NULL. If it is, the driver returns -ENOMEM, indicating a memory allocation failure, preventing the kernel crash.
CVSS Analysis
Currently, a CVSS score is not available (N/A) for CVE-2025-40224. However, while a specific CVSS score is absent, the potential for a kernel crash definitely suggests a notable severity level. The impact of a kernel crash is significant, potentially leading to system instability and denial of service.
Possible Impact
The primary impact of this vulnerability is a denial-of-service (DoS) condition. A successful exploitation (i.e., triggering the memory allocation failure and subsequent NULL pointer dereference) can cause the Linux kernel to crash, rendering the system unusable until it is rebooted. This vulnerability could be triggered by a specially crafted input that stresses memory allocation within the driver.
Mitigation and Patch Steps
The recommended mitigation is to update your Linux kernel to a version that includes the fix for CVE-2025-40224. The fix has been applied to stable kernel branches. Check your Linux distribution’s security advisories and apply the appropriate kernel update. You can also manually patch your kernel using the provided commit links.
Specifically, apply the following patches:
- Patch commit a09a5aa8bf258ddc99a22c30f17fe304b96b5350
- Patch commit 240b82b86a091c1aa49d951d4467425420a081a0
If upgrading the kernel is not immediately possible, consider disabling the cgbc-hwmon driver as a temporary workaround, if it is not critical for your system’s functionality. However, this should only be considered a temporary measure until a proper update can be applied.
References
https://git.kernel.org/stable/c/240b82b86a091c1aa49d951d4467425420a081a0
https://git.kernel.org/stable/c/a09a5aa8bf258ddc99a22c30f17fe304b96b5350
