Overview
CVE-2025-40227 identifies a memory leak vulnerability found in the Data Access Monitoring (DAMON) subsystem of the Linux kernel. The vulnerability arises from the improper deallocation of memory used for testing online DAMON parameters commit inputs. This article provides a detailed analysis of the vulnerability, its potential impact, and the steps taken to mitigate it.
Technical Details
The issue stems from the fact that the damon_ctx (DAMON context) used for testing online DAMON parameters commit inputs was only deallocated when the test failed. This meant that every successful online DAMON parameters commit would result in a memory leak, as the allocated damon_ctx remained in memory without being released. This behavior, if left unchecked, could lead to resource exhaustion and system instability over time.
The faulty logic has been corrected by ensuring that the damon_ctx is always deallocated, regardless of whether the test for the online DAMON parameters commit input succeeds or fails.
CVSS Analysis
As of the time of writing, CVE-2025-40227 has a CVSS score of N/A. This is likely due to the fact that it is a memory leak, which, while potentially impactful, doesn’t immediately lead to remote code execution or other critical security issues. However, the cumulative effect of the memory leak over time can significantly degrade system performance.
Possible Impact
While not immediately critical, the memory leak caused by CVE-2025-40227 can lead to:
- Resource Exhaustion: The continuous allocation of memory without deallocation eventually leads to the system running out of available memory.
- System Instability: As memory becomes scarce, the kernel may start terminating processes, or the system may become unresponsive.
- Performance Degradation: Reduced available memory leads to increased swapping, which significantly slows down system performance.
Mitigation or Patch Steps
The vulnerability has been addressed in the Linux kernel. The fix involves ensuring that the damon_ctx is always deallocated. Users are advised to update their kernel to a version that includes the fix. The fix can be identified by the following commit IDs:
Specific steps to take:
- Check your Kernel Version: Determine the version of the Linux kernel running on your system.
- Apply the Patch: If your kernel version is vulnerable, apply the appropriate patch from the upstream Linux kernel repository or your distribution’s security updates. Follow your distribution’s recommended update procedure.
- Reboot: After applying the patch, reboot your system to ensure the changes are applied.
