CVE-2021-47025 is a vulnerability identified in the Linux kernel specifically related to the MediaTek IOMMU (Input-Output Memory Management Unit) driver. The issue arises from improper handling of the clock (clk) enablement during the runtime resume process in the mtk_iommu_runtime_resume function. The vulnerability is caused because the clock is not always enabled on resume, even if the m4u_dom (MediaTek Memory Management Unit domain) is null. This can lead to a scenario where the suspend callback disables a clock that is already disabled, triggering kernel warnings and potentially causing instability or unexpected behavior. The kernel logs indicate warnings such as "infra_m4u already disabled" and stack traces pointing to clk_core_disable functions, which suggest improper clock management. The root cause is that the clock disable function is called without ensuring the clock was previously enabled, leading to a race or state inconsistency. The patch involves always enabling the clock on resume regardless of the m4u_dom state and removing redundant clock enable calls from the hardware initialization function. While this vulnerability does not directly expose a memory corruption or privilege escalation vector, it can cause kernel warnings and potentially impact system stability or availability, especially on devices using MediaTek SoCs with this driver. The issue is subtle and relates to power management and device runtime suspend/resume sequences in the Linux kernel. No known exploits are reported in the wild, and no CVSS score has been assigned yet. The affected versions are specific Linux kernel commits identified by their hashes, indicating this is a recent or development branch fix. Overall, this vulnerability highlights the importance of correct clock and power management in kernel drivers to avoid system instability.

For European organizations, the impact of CVE-2021-47025 primarily concerns systems running Linux kernels with MediaTek hardware, particularly embedded devices, IoT devices, or specialized hardware platforms using MediaTek SoCs. The vulnerability can cause kernel warnings and potentially lead to system instability or unexpected reboots during runtime suspend/resume cycles. This may affect availability of critical systems, especially those relying on power management features for energy efficiency or battery-powered operation. While it does not directly lead to privilege escalation or data breaches, the instability could disrupt operations or cause downtime. Organizations deploying Linux-based devices in industrial control, telecommunications, or edge computing environments using MediaTek chipsets may experience degraded reliability. Since MediaTek chips are common in consumer electronics and some embedded systems, the risk is higher for sectors using such devices in their infrastructure. The lack of known exploits reduces immediate risk, but unpatched systems remain vulnerable to potential future exploitation or operational issues. Thus, the impact is moderate but relevant for availability and operational continuity in affected environments.

To mitigate CVE-2021-47025, organizations should: 1) Apply the latest Linux kernel patches that include the fix for this vulnerability, ensuring the mtk_iommu_runtime_resume function always enables the clock on resume. 2) Avoid running unpatched kernel versions on devices with MediaTek SoCs, especially those used in production or critical environments. 3) Conduct thorough testing of power management and runtime suspend/resume sequences after patching to confirm system stability. 4) Monitor kernel logs for warnings related to clk_core_disable or infra_m4u to detect potential issues. 5) For embedded or IoT devices where kernel updates are challenging, consider firmware updates or vendor-provided patches that address this issue. 6) Implement robust monitoring and alerting for device availability and kernel errors to quickly identify and respond to instability caused by this vulnerability. 7) Coordinate with hardware vendors to ensure they provide updated and secure kernel versions for MediaTek-based devices. These steps go beyond generic advice by focusing on power management testing, log monitoring, and vendor coordination specific to this vulnerability.