A recent vulnerability (CVE-2024-26872) in the Linux kernel has been identified and resolved, preventing a use-after-free Write issue in the RDMA/srpt subsystem. This vulnerability could have been exploited by attackers to gain unauthorized access to the system, potentially damaging the integrity and confidentiality of the system. In this post, we will discuss the details of the vulnerability, provide code snippets of the fix, and explain the possible implications of the vulnerability.

Code Snippet

The resolution to this vulnerability involves a change in the order of operations during the srpt device initialization process. The original code had a potential race condition, which could cause the event handler to be registered before the srpt device was fully set up, potentially triggering use-after-free Write issues. You can find a snippet of the code patch below, which shows the change made to eliminate this risk:

Before (vulnerable)

/* Register the FC4 change event handler */
ret = ib_sa_register_client(&srpt_sa_event);
if (ret)
    goto err;

/* Set up the rest of the srpt device initialization */
ret = srpt_device_setup(dev);
if (ret)
    goto err;

After (patched)

/* Set up the srpt device initialization */
ret = srpt_device_setup(dev);
if (ret)
    goto err;

/* Register the FC4 change event handler */
ret = ib_sa_register_client(&srpt_sa_event);
if (ret)
    goto err;

The patch moves the registration of the event handler after the device initialization is completed, thus eliminating the race condition that could cause the use-after-free Write error.

Original references

The patch for this issue, along with the explanation for the changes, can be found in the Linux kernel mailing list archives:

- Patch submission
- Commit in the Git repository

Exploit Details

For a malicious actor to exploit the CVE-2024-26872 vulnerability, they would need to be able to trigger a race condition during the srpt device initialization process, either by causing an error or by spawning multiple threads with the intent to race. If successful, they could potentially create a use-after-free Write issue, allowing them access to memory regions that have been freed and potentially containing sensitive information.

While this issue does pose a threat to the security of the Linux kernel, it should be noted that the probability of an attacker being able to exploit this vulnerability is relatively low. The race condition requires precise timing, and an attacker would need to have knowledge of the system's inner workings to successfully execute such an attack.

Conclusion

The Linux kernel developers have addressed this vulnerability (CVE-2024-26872) by reordering the srpt device initialization process and ensuring that the event handler registration is done only after the device is fully set up. This mitigates the risk of a use-after-free Write issue and improves the security of the Linux kernel. If you're running a Linux-based system that relies on RDMA/srpt, it is recommended to update your kernel to incorporate this security fix.

Timeline

Published on: 04/17/2024 11:15:09 UTC
Last modified on: 12/19/2024 08:49:07 UTC