Overview
CVE-2025-40228 describes a vulnerability discovered in the Linux kernel’s DAMON (Data Access Monitoring) sysfs interface. This vulnerability arises from a missing allocation failure check during the creation of a damon_ctx object used for validating DAMON parameters. Without this check, a failed allocation could lead to a null pointer dereference and potentially other unexpected behavior. The fix addresses the memory leak and the lack of allocation failure handling.
Technical Details
The DAMON sysfs interface allows userspace to dynamically update DAMON parameters. To ensure the validity of these parameters, the kernel dynamically allocates a damon_ctx object to perform a test commit. The vulnerability lies in the fact that the allocation of this damon_ctx object was not checked for failure. If the allocation failed (due to insufficient memory, for example), the code would continue to use the uninitialized pointer, leading to a potential memory access violation.
The provided patch specifically addresses this issue by adding an explicit check for allocation failure after the damon_ctx object is allocated. If the allocation fails, the function now returns an error, preventing the subsequent use of the invalid pointer.
CVSS Analysis
Currently, the CVE record indicates a severity of N/A and a CVSS score of N/A. This suggests that the vulnerability’s impact and exploitability are still being assessed. However, the potential for a memory access violation indicates a potential for denial-of-service or, in some scenarios, potentially escalating to more severe consequences. The actual CVSS score may change as more information becomes available.
Possible Impact
While the CVSS score is currently N/A, the potential impact of CVE-2025-40228 could include:
- Denial of Service (DoS): A failed memory allocation followed by an invalid memory access could cause the kernel to crash, leading to a system-wide denial of service.
- Unpredictable Behavior: Using an uninitialized pointer can lead to unpredictable system behavior, making debugging difficult.
Mitigation or Patch Steps
The recommended mitigation is to apply the patch associated with this CVE. This patch adds the necessary allocation failure check to the DAMON sysfs interface.
To apply the patch:
- Identify the affected kernel version.
- Obtain the patch from the kernel Git repository (see references below).
- Apply the patch to your kernel source code.
- Recompile and reinstall the kernel.
- Reboot the system to use the patched kernel.
Alternatively, upgrading to a kernel version that includes the fix is also a viable option.
