Preventing Use-After-Free in cgroup v1

CVE-2024-43853

What is CVE-2024-43853?

A Use-After-Free (UAF) vulnerability exists in the Linux kernel's cgroup/cpuset component. This vulnerability can be triggered during the reading of the /proc/cpuset file, leading to potential instability or security risks. The bug manifests when the cpuset is initialized and a race condition occurs during the mounting and unmounting of cgroups. Specifically, it arises when a reference to a cgroup that is slated for deallocation is retained, posing a risk for unauthorized access or manipulation. The fix involved employing an RCU (Read-Copy-Update) lock in the proc_cpuset_show() function to ensure that the cgroup cannot be freed while it is being accessed, thus mitigating the UAF risk.

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