CVE-2021-47058 is a vulnerability identified in the Linux kernel's regmap subsystem, specifically related to the handling of debugfs_name during debug filesystem operations. The issue arises from improper memory management where the debugfs_name pointer is freed in the function regmap_debugfs_exit() but is not reset to NULL afterward. This leads to a use-after-free condition because subsequent logic checks an if condition introduced in an upstream commit (cffa4b2122f5) that prevents the recreation of debugfs_name if it is already set, but since the pointer is dangling (freed but not NULL), the system may attempt to access invalid memory. The vulnerability is rooted in the sequence of function calls: regmap_reinit_cache() calls regmap_debugfs_exit(), which frees debugfs_name, but due to the introduced conditional logic, regmap_debugfs_init() does not recreate debugfs_name, leaving the pointer in an inconsistent state. This can cause memory corruption or instability within the kernel's debugfs interface, potentially leading to kernel crashes or undefined behavior. The fix involves setting debugfs_name to NULL immediately after it is freed to prevent the use-after-free scenario. The affected versions include multiple Linux kernel commits prior to the fix. No known exploits are reported in the wild as of the publication date.

For European organizations, this vulnerability poses a risk primarily to systems running affected Linux kernel versions that utilize the regmap debugfs interface, commonly found in embedded systems, IoT devices, and servers that rely on Linux for hardware register mapping and debugging. Exploitation could lead to kernel crashes or denial of service, impacting system availability. While the vulnerability does not directly indicate privilege escalation or remote code execution, kernel instability can disrupt critical infrastructure, especially in sectors like telecommunications, manufacturing, and cloud services prevalent in Europe. Organizations relying on Linux-based systems for operational technology or critical services may experience service interruptions or require emergency patching, which could affect business continuity and operational efficiency.

European organizations should promptly verify their Linux kernel versions and identify systems running affected commits. Specific mitigation steps include: 1) Applying the official Linux kernel patches that set debugfs_name to NULL after freeing, as per the upstream commit cffa4b2122f5 and related fixes. 2) For systems where immediate patching is not feasible, consider disabling debugfs or restricting access to debugfs interfaces to trusted administrators only, reducing the attack surface. 3) Implement rigorous kernel update policies and continuous monitoring to detect abnormal kernel behavior or crashes that could indicate exploitation attempts. 4) For embedded and IoT devices, coordinate with vendors to obtain updated firmware incorporating the fix. 5) Conduct thorough testing of kernel updates in staging environments to ensure stability before deployment in production. These targeted actions go beyond generic advice by focusing on the specific subsystem and operational contexts affected.