CVE-2025-38104 is a vulnerability identified in the Linux kernel's AMDGPU driver, specifically related to the handling of RLCG (Register Level Control Group) register access in virtualized environments using SR-IOV (Single Root I/O Virtualization). The vulnerability arises from the use of a mutex to serialize access to GPU registers in the amdgpu_virt_rlcg_reg_rw function. This mutex acquisition occurs in contexts where sleeping is disallowed, such as when holding a spinlock, leading to a priority inversion problem and triggering kernel bugs like "BUG: Invalid wait context." The root cause is that the mutex can cause a thread to sleep while it is in a critical section that requires non-blocking synchronization primitives. The fix involves replacing the mutex with a spinlock to avoid priority inversion and ensure safe, non-blocking register access. This vulnerability affects Linux kernel versions containing the specified commits and impacts systems using AMD GPUs with virtualization features enabled, particularly those leveraging SR-IOV for GPU virtualization. The issue manifests as kernel instability, including potential kernel panics or deadlocks, due to improper synchronization in GPU register access paths. The vulnerability is significant in environments where multiple virtual functions or threads concurrently access GPU registers, such as cloud or virtualized data centers using AMD GPUs. Although no known exploits are currently reported in the wild, the vulnerability could be leveraged to cause denial of service or system instability in affected systems. The detailed kernel stack traces and context information indicate the problem arises during GPU TLB flush operations and GPU initialization sequences involving virtualized GPU register access.

For European organizations, especially those operating data centers, cloud services, or virtualization platforms using Linux with AMD GPUs and SR-IOV enabled, this vulnerability poses a risk of system instability and denial of service. The impact includes potential kernel crashes or deadlocks that could disrupt critical workloads, affecting availability of services relying on GPU acceleration or virtualization. Industries such as cloud providers, research institutions, financial services, and media companies that utilize GPU virtualization for compute-intensive tasks could experience operational interruptions. Additionally, organizations using Linux-based virtual desktop infrastructure (VDI) or GPU-accelerated virtual machines may face degraded performance or outages. While the vulnerability does not directly expose confidentiality or integrity risks, the availability impact can be significant, especially in multi-tenant environments where resource sharing is critical. The lack of known exploits reduces immediate risk, but the complexity of the bug and its presence in kernel code used widely across Europe necessitate prompt patching to maintain system reliability and service continuity.

1. Apply the official Linux kernel patches that replace the mutex with a spinlock in the amdgpu driver as soon as they become available from trusted Linux distribution vendors or the upstream kernel. 2. For organizations running custom or out-of-tree kernel modules, ensure that the amdgpu driver is updated to the fixed version to prevent priority inversion issues. 3. In virtualized environments, consider temporarily disabling SR-IOV GPU virtualization features if patching is delayed, to reduce exposure to the vulnerability. 4. Monitor kernel logs for signs of "BUG: Invalid wait context" or related kernel warnings that may indicate attempts to exploit or trigger the bug. 5. Implement robust kernel crash and recovery mechanisms to minimize downtime in case of kernel panics. 6. Coordinate with hardware vendors and Linux distribution maintainers to receive timely updates and verify compatibility of patches with existing infrastructure. 7. Conduct thorough testing of updated kernels in staging environments before deployment to production to ensure stability and performance are maintained.