CVE-2021-47177 is a vulnerability identified in the Linux kernel, specifically within the IOMMU (Input-Output Memory Management Unit) VT-d subsystem. The vulnerability arises from a sysfs leak in the alloc_iommu() function. The technical root cause is that iommu_device_sysfs_add() is called before certain operations, but in the event of subsequent errors, the allocated sysfs entries are not properly cleaned up. This leads to a resource leak in the sysfs interface related to IOMMU devices. Sysfs is a virtual filesystem in Linux that exposes kernel device and driver information to user space. Improper cleanup of sysfs entries can cause resource exhaustion or inconsistent system state. Although the vulnerability does not directly indicate a memory corruption or privilege escalation, the leak could potentially be leveraged in complex attack scenarios to degrade system stability or cause denial of service. The vulnerability affects Linux kernel versions identified by the commit hash 39ab9555c24110671f8dc671311a26e5c985b592, which suggests it impacts certain recent kernel builds. No known exploits are reported in the wild, and no CVSS score has been assigned yet. The fix involves ensuring that sysfs entries created by iommu_device_sysfs_add() are properly cleaned up on error paths within alloc_iommu(), preventing the leak. This vulnerability is technical and low-level, affecting kernel internals related to IOMMU device management.

For European organizations, the impact of CVE-2021-47177 is primarily related to system stability and potential denial of service conditions on Linux systems utilizing IOMMU VT-d features. Organizations running Linux servers, especially those using virtualization, containerization, or hardware passthrough that rely on IOMMU for device isolation and memory management, could experience resource leaks leading to degraded performance or system crashes over time if the vulnerability is exploited or triggered. While there is no evidence of privilege escalation or direct data compromise, the leak could be used by attackers to create persistent denial of service conditions, impacting availability of critical infrastructure. This is particularly relevant for data centers, cloud providers, and enterprises with Linux-based infrastructure in Europe. The lack of known exploits reduces immediate risk, but unpatched systems remain vulnerable to potential future attacks or accidental system instability. The vulnerability also highlights the importance of maintaining updated kernel versions to ensure system robustness.

European organizations should prioritize updating Linux kernels to versions where this vulnerability is patched. Since the vulnerability is related to kernel internals, applying official Linux kernel updates or vendor-provided patches is the most effective mitigation. Organizations should: 1) Identify all Linux systems using IOMMU VT-d features, especially those running virtualization or hardware passthrough workloads. 2) Verify kernel versions and apply vendor security patches or upgrade to a fixed kernel release as soon as possible. 3) Monitor system logs and resource usage for signs of sysfs leaks or unusual behavior that might indicate exploitation attempts. 4) Implement strict access controls to limit unprivileged user interaction with sysfs interfaces, reducing the risk of triggering the vulnerability. 5) For critical infrastructure, consider additional monitoring and alerting on kernel subsystem anomalies. 6) Coordinate with Linux distribution vendors for timely patch deployment and security advisories. Avoid using workarounds that disable IOMMU features unless absolutely necessary, as this may impact system security and performance.