CVE-2023-52484 addresses a vulnerability in the Linux kernel specifically related to the ARM System Memory Management Unit (SMMU) version 3 implementation. The vulnerability manifests as a soft lockup triggered by the function arm_smmu_mm_invalidate_range (renamed in recent kernels to arm_smmu_mm_arch_invalidate_secondary_tlbs). This function is involved in invalidating translation lookaside buffers (TLBs) for memory management. The issue arises when the SMMU issues a large number of per-page TLB invalidation commands without proper batching or threshold checks, leading to excessive CPU lockup. The lockup is observed as a watchdog bug where a CPU core becomes unresponsive for an extended period (e.g., 26 seconds), effectively causing a denial of service on that CPU core. The root cause is that the SMMU's TLB invalidation logic does not respect the maximum number of TLB invalidation operations (MAX_TLBI_OPS) as the CPU MMU code does. The fix involves cloning the CMDQ_MAX_TLBI_OPS constant from the CPU MMU code and replacing multiple per-page invalidations with a single per-address space identifier (ASID) invalidation when the number of invalidations exceeds this threshold. This change aligns the SMMU behavior with the CPU MMU's approach, preventing the soft lockup. The vulnerability affects Linux kernel versions prior to the patch and is particularly relevant for systems using ARM architecture with SMMU v3 and Shared Virtual Addressing (SVA) features. While no known exploits are reported in the wild, the issue can cause system instability or denial of service in affected environments. The vulnerability does not require user interaction or authentication to trigger if the system is running workloads that cause the SMMU to perform extensive TLB invalidations, such as virtualization or advanced memory management scenarios.

For European organizations, the impact of CVE-2023-52484 can be significant in environments running ARM-based Linux systems, especially those utilizing virtualization, containerization, or advanced memory management features that rely on SMMU v3 and SVA. The soft lockup can lead to CPU core hangs, resulting in degraded system performance, application crashes, or complete denial of service on critical infrastructure. This is particularly concerning for sectors relying on ARM-based servers, embedded systems, or edge computing devices, such as telecommunications, automotive, industrial control, and cloud service providers. The instability could disrupt services, cause data processing delays, or impact real-time systems. Since the vulnerability affects kernel-level memory management, it could indirectly affect confidentiality and integrity if system crashes lead to improper handling of sensitive data or system states. However, the primary impact is on availability. European organizations deploying ARM-based Linux systems in data centers or critical infrastructure must be aware of this vulnerability to avoid unexpected outages and maintain service continuity.

1. Apply the official Linux kernel patches that address CVE-2023-52484 as soon as they become available for your distribution or kernel version. Monitor vendor advisories for updated kernel releases. 2. For organizations using custom or embedded Linux kernels, backport the patch that clones CMDQ_MAX_TLBI_OPS and modifies the TLB invalidation logic in the arm_smmu driver to prevent soft lockups. 3. Test kernel updates in staging environments that replicate production workloads involving SMMU and SVA to ensure stability before deployment. 4. Monitor system logs for watchdog soft lockup messages or CPU stalls related to arm_smmu functions to detect potential exploitation or triggering of the vulnerability. 5. Limit or control workloads that cause extensive TLB invalidations on affected systems until patches are applied, such as reducing aggressive memory mapping/unmapping operations or tuning virtualization configurations. 6. Collaborate with hardware vendors to ensure firmware and platform support for updated kernel versions and SMMU behavior. 7. Maintain robust backup and recovery procedures to mitigate potential downtime caused by system instability.