CVE-2021-47483 is a vulnerability identified in the Linux kernel's regmap subsystem, specifically within the regcache_rbtree component. The flaw arises from improper error handling in the regcache_rbtree_insert_to_block() function. When a memory reallocation ('realloc') operation fails during the insertion process, the code erroneously frees a memory block ('blk') that is still referenced by the red-black tree node's 'block' pointer (rbnode->block). This leads to a use-after-free condition where 'rbnode->block' points to freed memory. Subsequently, during cleanup in regcache_rbtree_exit(), the same memory is freed again, causing a double-free error. This double-free is detected by Kernel Address Sanitizer (KASAN) as an invalid free operation. The root cause is the delayed assignment of the 'rbnode->block' pointer until after the second reallocation succeeds, which allows the pointer to reference freed memory if the second realloc fails. The fix involves moving the assignment of 'rbnode->block' immediately after the first successful reallocation, ensuring the data structure remains consistent even if subsequent reallocations fail. This vulnerability affects Linux kernel versions identified by the commit hash 3f4ff561bc88b074d5e868dde4012d89cbb06c87 and likely other versions containing the same regmap implementation. No known exploits have been reported in the wild as of the publication date (May 22, 2024).

The vulnerability can lead to kernel memory corruption due to double-free conditions, which may cause system instability, crashes (kernel panics), or potentially enable privilege escalation or arbitrary code execution within the kernel context if exploited. For European organizations, especially those running Linux-based infrastructure such as servers, embedded devices, or IoT systems that utilize the regmap subsystem (commonly used for managing register maps in hardware devices), this vulnerability could compromise system reliability and security. Exploitation could disrupt critical services, lead to denial of service, or be leveraged as part of a multi-stage attack to gain elevated privileges. Given the Linux kernel's widespread use across European industries including telecommunications, finance, manufacturing, and government, the impact could be significant if attackers develop reliable exploits. However, the absence of known exploits and the technical complexity of triggering this specific double-free condition may limit immediate risk. Nonetheless, unpatched systems remain vulnerable to future exploitation attempts.

European organizations should promptly apply the official Linux kernel patches that address CVE-2021-47483 once available from their Linux distribution vendors. System administrators should: 1) Identify all Linux systems running affected kernel versions, particularly those with hardware components using the regmap subsystem (e.g., SPI devices, embedded controllers). 2) Prioritize patching of critical infrastructure and devices exposed to untrusted inputs or networks. 3) Employ kernel hardening techniques such as Kernel Address Sanitizer (KASAN) in testing environments to detect similar memory corruption issues proactively. 4) Monitor kernel logs for signs of memory corruption or double-free errors that could indicate exploitation attempts. 5) Limit access to systems with vulnerable kernels, especially restricting unprivileged user access that could trigger the vulnerability. 6) Engage with Linux distribution security advisories and subscribe to vulnerability notifications to stay informed about updates and exploit developments. 7) For embedded or IoT devices, coordinate with hardware vendors to ensure firmware updates include the kernel fix. These steps go beyond generic advice by focusing on the specific subsystem and error conditions involved in this vulnerability.