CVE-2021-47649 is a vulnerability identified in the Linux kernel's udmabuf driver, which is responsible for user-space DMA buffer management. The issue arises from improper validation of the 'ubuf->pagecount' parameter, which is derived from user-space input. Specifically, if a user creates a udmabuf with a list size of zero, the 'ubuf->pagecount' becomes zero. This leads to a call to kmalloc_array() with a zero size, which returns a ZERO_PTR (null pointer). Subsequently, this can cause a general protection fault (GPF) in the function sg_alloc_append_table_from_pages(), as the code does not handle the zero pointer correctly. The root cause is the lack of validation on 'ubuf->pagecount' before it is passed to kmalloc_array(). The vulnerability was reported by Syzbot, an automated kernel fuzzer, and has been addressed by adding validation to ensure 'ubuf->pagecount' is not zero before memory allocation. This flaw could potentially be triggered by a local user with the ability to create udmabuf devices, leading to kernel crashes or denial of service. There is no indication that this vulnerability allows privilege escalation or arbitrary code execution. No known exploits are reported in the wild, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2021-47649 primarily concerns system stability and availability. Since the vulnerability can cause kernel crashes (general protection faults), it can be exploited to trigger denial of service conditions on affected Linux systems. This is particularly relevant for servers, embedded devices, and infrastructure running Linux kernels with the vulnerable udmabuf driver enabled. Organizations relying on Linux-based systems for critical services, including cloud providers, telecommunications, and industrial control systems, may experience service interruptions if this vulnerability is exploited. However, the requirement for local user access to create udmabuf devices limits the attack surface to insiders or compromised accounts. The vulnerability does not appear to compromise confidentiality or integrity directly, but availability degradation could impact business operations and service level agreements. Given the widespread use of Linux in European IT environments, especially in enterprise servers and embedded systems, the potential for disruption exists but is mitigated by the need for local access and the absence of known remote exploits.

To mitigate CVE-2021-47649, European organizations should: 1) Apply the latest Linux kernel patches that include the fix validating 'ubuf->pagecount' before memory allocation. Regularly update kernel versions to incorporate security fixes. 2) Restrict access to device creation interfaces related to udmabuf to trusted users only, minimizing the risk of local exploitation. 3) Implement strict user privilege management and monitoring to detect and prevent unauthorized attempts to create udmabuf devices. 4) Employ kernel hardening techniques such as SELinux or AppArmor policies to limit the capabilities of user-space processes interacting with kernel drivers. 5) Monitor system logs for kernel faults or crashes that may indicate exploitation attempts. 6) For embedded or specialized Linux systems, verify if the udmabuf driver is enabled and consider disabling it if not required. These steps go beyond generic advice by focusing on access control, patch management, and proactive monitoring tailored to the nature of this vulnerability.