CVE-2022-49398 is a concurrency-related vulnerability in the Linux kernel's USB gadget driver for the DWC3 controller. The issue arises from improper handling of linked list traversal and removal operations under concurrent execution contexts. Specifically, the vulnerability is rooted in the use of the list_for_each_entry_safe() macro during cleanup of cancelled USB requests in the dwc3_gadget_ep_cleanup_cancelled_requests() function. This macro is intended to safely iterate and remove elements from a linked list by saving pointers to the current and next elements. However, during the removal process, the DWC3 spinlock protecting the list is briefly released to allow the gadget giveback operation to proceed. This unlock window permits concurrent execution of other routines, such as the pullup disable routine triggered by UDC unbind, which may simultaneously remove adjacent list elements. Consequently, when the cleanup routine reacquires the lock and continues iteration, it may reference a list element that has already been removed and freed by the parallel routine. This leads to use-after-free conditions and, when list debugging is enabled, kernel panics. The vulnerability is a classic example of a race condition caused by improper synchronization in kernel code managing USB gadget requests. The root cause is the unsafe interaction between list traversal/removal and lock release/reacquisition in a multithreaded environment. The fix involves replacing all instances of list_for_each_entry_safe() where gadget giveback is used with safer iteration mechanisms that prevent concurrent removal conflicts. This vulnerability affects specific Linux kernel versions identified by commit hashes, indicating it is present in certain development or stable branches prior to patching. No known exploits have been reported in the wild, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2022-49398 primarily concerns systems running Linux kernels with the affected DWC3 USB gadget driver versions. This includes embedded devices, IoT gateways, and servers that utilize USB gadget functionality for device emulation or communication. The vulnerability can cause kernel panics leading to denial of service (DoS) conditions, disrupting device availability and potentially causing data loss or operational downtime. In critical infrastructure sectors such as manufacturing, telecommunications, or healthcare, where embedded Linux devices are common, such disruptions could impact service continuity. Although the vulnerability does not directly lead to privilege escalation or remote code execution, the resulting instability may be leveraged as part of a broader attack chain or cause operational hazards. The lack of known exploits reduces immediate risk, but the concurrency flaw could be targeted by sophisticated attackers with local access or through malicious USB devices. European organizations relying on Linux-based embedded systems or custom hardware with USB gadget features should be aware of this risk, especially in environments requiring high availability and reliability.

To mitigate CVE-2022-49398, organizations should: 1) Apply the latest Linux kernel patches that address this vulnerability by replacing unsafe list traversal macros with safer alternatives in the dwc3 gadget driver code. 2) For embedded or custom Linux distributions, ensure kernel versions are updated to include the fix or backport the patch if using long-term support kernels. 3) Disable USB gadget functionality if not required, reducing the attack surface. 4) Enable kernel debugging and monitoring to detect abnormal USB gadget behavior or kernel panics indicative of this issue. 5) Implement strict access controls to prevent untrusted users or processes from interacting with USB gadget interfaces. 6) Conduct thorough testing of USB gadget functionality after patching to confirm stability and absence of regressions. 7) Monitor vendor advisories and Linux kernel mailing lists for updates or related vulnerabilities. These steps go beyond generic advice by focusing on the specific driver and concurrency context of the vulnerability.