CVE-2024-43905 - Linux Kernel Security Patch: Resolving a Vulnerability in drm/amd/pm Module for Vega10_hwmgr

The Linux kernel, which acts as the core of the Linux operating system, has faced a critical vulnerability in the drm/amd/pm module, specifically when managing power for Vega10 GPU architectures. The vulnerability, assigned as CVE-2024-43905, allows malicious users or applications to exploit a null pointer dereference, which may result in a system crash, disruption of service, or even data corruption. This long-read post will outline the technical details of the vulnerability, provide a code snippet that demonstrates fixed code, and share some references to the original vulnerability report and patch.

The Vulnerability

The vulnerability exploits a lack of proper error checking and handling in the vega10_hwmgr function within the drm/amd/pm module. A null pointer dereference occurs when the function tries to use a pointer before checking if it's safe to do so.

In this case, the vega10_hwmgr function doesn't verify if the Vega10 GPU's hardware manager is appropriately initialized or not. If the hardware manager isn't correctly initialized, a null pointer dereference can lead to unexpected behavior or a crash of the system.

Furthermore, exploiting this vulnerability allows an attacker to cause a denial-of-service (DoS) condition by intentionally causing the vega10_hwmgr function to access a null pointer. This can be effectively mitigated by modifying the function to properly check for null pointers before accessing them.

The Patch

The solution lies in adding null pointer checks to the vega10_hwmgr function before using its pointer. The updated code snippet below demonstrates the proper way to handle this situation by checking the return value of the vega10_hwmgr function and handling the null pointer case accordingly:

struct vega10_smumgr *smu_data = hwmgr->smu_backend;

if (!smu_data) {
    pr_err("%s: Failed to initialize smu_data for Vega10 GPU.\n", __func__);
    return -EINVAL;
}

/* Continue processing with the smu_data pointer */

In the code snippet above, the vega10_hwmgr function checks if smu_data is NULL or not, indicating a failure to initialize the hardware manager. If the check returns true, then the function prints an error message and immediately returns an error code, thus effectively preventing the null pointer dereference and any subsequent consequences.

Original References

For those interested in further technical and historical details about this vulnerability, the original bug report and associated patch can be found in the following links:

1. Bug Report – LKML
2. Vulnerability Summary – CVE.Mitre.org
3. Patch – Linux Kernel Git

Conclusion

In conclusion, the CVE-2024-43905 vulnerability in the Linux kernel's drm/amd/pm module for Vega10 GPUs has been effectively resolved by adding proper null pointer checking and handling to the vega10_hwmgr function. Users and administrators are advised to ensure they are running the most up-to-date version of the Linux kernel to avoid any potential exploitation of this vulnerability.

Timeline

Published on: 08/26/2024 11:15:04 UTC
Last modified on: 08/27/2024 13:41:03 UTC