CVE-2024-50138 is a vulnerability identified in the Linux kernel related to the use of spinlocks within the Berkeley Packet Filter (BPF) ring buffer implementation. Specifically, the function __bpf_ringbuf_reserve, which is called from a tracepoint context where preemption is disabled, improperly uses the standard spinlock_t type. This can lead to a "sleep in atomic" warning in the real-time (RT) variant of the kernel. The issue arises because spinlock_t may invoke sleeping functions, which are not allowed when preemption is disabled, causing kernel warnings and potentially destabilizing the system. The vulnerability is demonstrated by kernel logs showing a BUG triggered by calling a sleeping function from an invalid atomic context, with detailed call traces indicating the problem occurs during BPF ring buffer reservation. The recommended fix is to replace spinlock_t with raw_spinlock_t in this context, as raw_spinlock_t does not have the sleeping behavior and is safe to use when preemption is disabled. This vulnerability affects Linux kernel versions identified by the commit hashes provided and was published on November 5, 2024. No known exploits are reported in the wild at this time, and no CVSS score has been assigned yet.

For European organizations, this vulnerability primarily affects systems running Linux kernels with real-time capabilities or those utilizing BPF extensively, such as in performance monitoring, security tracing, or network packet filtering. The improper locking can cause kernel warnings and potentially lead to system instability or crashes in environments where real-time guarantees are critical, such as telecommunications, industrial control systems, or financial trading platforms. While it does not directly allow privilege escalation or remote code execution, the resulting instability could cause denial of service conditions or disrupt critical services. Organizations relying on Linux-based infrastructure for critical operations may experience degraded reliability or unexpected downtime if this vulnerability is triggered. The impact is more pronounced in environments using the RT kernel variant or heavy BPF usage, which are common in advanced monitoring and security tooling.

To mitigate this vulnerability, European organizations should prioritize updating their Linux kernels to versions where this issue is patched, specifically those that replace spinlock_t with raw_spinlock_t in the BPF ring buffer code. Kernel updates should be tested and deployed promptly, especially in real-time or performance-sensitive environments. Additionally, organizations should audit their use of BPF programs and tracepoints to identify any that might invoke __bpf_ringbuf_reserve and assess the risk of triggering this bug. For systems where immediate kernel updates are not feasible, consider disabling or limiting BPF tracepoints or features that rely on the affected ring buffer code to reduce exposure. Monitoring kernel logs for "sleep in atomic" warnings can help detect attempts to trigger this issue. Finally, ensure that system and kernel debugging tools are configured to capture detailed traces to facilitate rapid diagnosis if instability occurs.