CVE-2021-47170 is a vulnerability identified in the Linux kernel's USB subsystem, specifically related to the usbfs interface. The issue arises when a user attempts to submit a bulk USB transfer with an excessively large buffer size. While this is not a kernel bug per se, but rather an invalid request from the user, the kernel previously generated a warning (WARN) due to the large memory allocation request. This warning could potentially lead to unnecessary kernel log noise or minor stability concerns. The vulnerability also theoretically extends to asynchronous transfers and the packet descriptor table for isochronous transfers, where similar large allocation requests could trigger warnings. The root cause is that the kernel's memory allocation function (kmalloc) was called without the __GFP_NOWARN flag, causing the memory management subsystem to complain loudly about these invalid requests. The fix involves adding the __GFP_NOWARN flag to kmalloc calls for these USB buffers, suppressing the warnings and preventing unnecessary kernel log entries. Importantly, this vulnerability does not represent a direct security flaw such as privilege escalation or denial of service but rather a robustness and stability improvement in handling invalid USB requests. There are no known exploits in the wild, and the vulnerability requires user-level interaction to trigger the warnings by submitting malformed USB requests via usbfs. The affected Linux kernel versions are identified by specific commit hashes, indicating this is a recent patch. Since usbfs is commonly used in Linux environments for USB device communication, this fix improves kernel stability and reduces potential log flooding from invalid USB requests.

For European organizations, the impact of CVE-2021-47170 is primarily related to system stability and operational noise rather than direct security compromise. Systems running Linux kernels with the vulnerable usbfs implementation could experience excessive kernel warnings if exposed to malformed USB requests, potentially from misconfigured or malicious USB devices. This could lead to increased kernel log sizes, making it harder for administrators to identify genuine issues and possibly causing minor performance degradation. However, there is no indication that this vulnerability can be exploited to gain unauthorized access, escalate privileges, or cause denial of service. Organizations with critical infrastructure or industrial control systems that rely on USB devices and run Linux kernels may benefit from applying this patch to maintain system reliability and reduce false-positive alerts. The vulnerability does not affect confidentiality or integrity directly but improves the robustness of USB handling in Linux systems.

To mitigate this vulnerability, European organizations should: 1) Identify Linux systems using usbfs for USB device communication, especially those running kernel versions prior to the patch commit referenced by CVE-2021-47170. 2) Apply the official Linux kernel patch that adds the __GFP_NOWARN flag to kmalloc calls in the usbfs code, which suppresses warnings on excessively large memory allocation requests. 3) Regularly update Linux kernels to the latest stable versions to incorporate ongoing security and stability fixes. 4) Monitor kernel logs for unusual USB-related warnings or errors that could indicate attempts to trigger this or similar issues. 5) Implement USB device control policies to restrict or monitor USB device usage, reducing the risk of malformed USB requests from unauthorized devices. 6) For environments with high security requirements, consider isolating critical systems from untrusted USB devices or using hardware-based USB filtering solutions. These steps go beyond generic advice by focusing on kernel patching, log monitoring, and USB device management tailored to this specific vulnerability.