CVE-2024-57849 - Linux Kernel s390/cpum_sf: Handle CPU Hotplug Remove During Sampling Vulnerability

A vulnerability, identified as CVE-2024-57849, has been discovered and resolved in the Linux kernel. The security issue concerns the handling of CPU hotplug removal during sampling in the s390/cpum_sf subsystem. Left unpatched, this vulnerability could lead to a use-after-free situation, which could result in unauthorized access to sensitive information, system crashes, or other potential issues.

Code Snippet

if (test_bit(PMU_F_RESERVED, cpum_sf_pmu->flags)) {
  // SDBs are present and contain valid data
  process_active_sdb(sdb, cpum_sf_pmu);
} else {
  // SDBs have been freed, skip processing
}

In the original code, the driver would attempt to process SDBs without checking if they have been freed or not, leading to potential use-after-free issues. The patched code adds a check for the PMU_F_RESERVED bit, ensuring that only valid and allocated SDBs are processed.

Original References

1. Linux Kernel Git Commit fixing the issue
2. s390/cpum_sf Documentation

Exploit Details

The vulnerability occurs when a CPU hotplug removal event takes place while the system is sampling data. The driver attempts to read and process the remaining samples from the SDBs, even though they might have already been freed and reassigned, leading to potential issues such as use-after-free vulnerabilities or accessing invalid sample data.

The exploit requires specific timing and conditions to take advantage of the issue, making it relatively difficult to establish a practical, targeted attack. However, an attacker could still exploit this vulnerability to compromise sensitive information or cause system instability if successful.

Recommendations

To mitigate the security risks associated with CVE-2024-57849, it is crucial to update the Linux kernel with the latest security patches. The Linux kernel developers have already addressed this issue in recent kernel updates.

Furthermore, as a general best practice, always ensure that your system is up-to-date with the latest security updates and patches available to minimize the risk of vulnerabilities being exploited by attackers. Regularly monitor security advisories and stay informed about emerging threats to safeguard your systems and data.

Timeline

Published on: 01/11/2025 15:15:07 UTC
Last modified on: 01/20/2025 06:28:34 UTC