CVE-2021-47253 is a vulnerability identified in the Linux kernel specifically related to the Direct Rendering Manager (DRM) subsystem for AMD graphics hardware. The issue arises in the handling of the DMUB (Display Microcontroller Unit Block) hardware initialization during system suspend and resume cycles. The vulnerability is caused by a memory leak due to repeated allocation of memory for the DMUB hardware initialization without proper deallocation or checks to prevent reallocation if memory was already allocated. Specifically, during the resume process, the function dm_resume calls dm_dmub_hw_init, which in turn calls dc_dmub_srv_create that uses kzalloc to allocate memory. Because this allocation occurs on every suspend/resume cycle without verifying if the memory was previously allocated, it leads to a memory leak. The patch for this vulnerability involves modifying the code to allocate memory for the DC wrapper to DMUB only if it has not been allocated before, thus preventing unnecessary repeated allocations and the resulting memory leak. This vulnerability does not appear to have an associated CVSS score and there are no known exploits in the wild at the time of publication. The vulnerability affects Linux kernel versions identified by the commit hash 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, indicating a specific code revision. The issue is primarily a resource management flaw rather than a direct security bypass or privilege escalation vector.

For European organizations, the impact of CVE-2021-47253 is primarily related to system stability and resource exhaustion rather than direct compromise or data breach. Systems running vulnerable Linux kernel versions with AMD graphics hardware that undergo frequent suspend/resume cycles could experience gradual memory leaks leading to degraded performance, increased system crashes, or potential denial of service due to exhaustion of kernel memory resources. This could affect workstations, servers, or embedded devices using Linux with AMD GPUs, particularly in environments where uptime and reliability are critical, such as financial institutions, manufacturing control systems, or public sector infrastructure. While the vulnerability does not directly expose confidentiality or integrity risks, the availability impact could disrupt business operations or critical services. The absence of known exploits reduces immediate risk, but unpatched systems remain vulnerable to potential future exploitation or stability issues.

To mitigate CVE-2021-47253, European organizations should prioritize updating their Linux kernel to the patched version that includes the fix preventing the memory leak in the DMUB hardware initialization. Specifically, kernel updates incorporating the commit identified by hash 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 should be applied. Organizations should audit their Linux systems to identify those running AMD GPU drivers and verify kernel versions. For systems where immediate patching is not feasible, monitoring kernel memory usage and system logs for signs of memory leaks or instability during suspend/resume cycles can help detect exploitation or impact. Additionally, organizations should review power management policies to minimize unnecessary suspend/resume cycles on critical systems until patches are applied. For embedded or specialized devices, coordination with hardware vendors or Linux distribution maintainers to obtain updated firmware or kernel versions is recommended. Finally, maintaining robust backup and recovery procedures ensures resilience against potential availability disruptions caused by this vulnerability.