CVE-2022-48869 is a use-after-free vulnerability identified in the Linux kernel's USB gadgetfs driver. The flaw arises due to a race condition between the mounting and unmounting operations of the gadgetfs filesystem. Specifically, the functions gadgetfs_fill_super() and gadgetfs_kill_sb() can execute concurrently without proper synchronization. gadgetfs_fill_super() is responsible for setting up the filesystem superblock during mount, while gadgetfs_kill_sb() handles cleanup during unmount. The race condition allows gadgetfs_kill_sb() to deallocate the_device structure while gadgetfs_fill_super() is still accessing it, leading to a use-after-free scenario. This was detected by the syzbot fuzzer and researcher Gerald Lee, with kernel address sanitizer (KASAN) logs confirming multiple use-after-free errors in atomic operations and reference counting within the driver code. The root cause is the lack of mutual exclusion between these two functions, which can be resolved by introducing a mutex to serialize their execution. Exploitation of this vulnerability could potentially allow an attacker with the ability to mount and unmount gadgetfs filesystems concurrently to trigger memory corruption, possibly leading to privilege escalation or denial of service. However, exploitation requires local access and the ability to perform these filesystem operations. The vulnerability affects Linux kernel versions prior to the patch that introduces the mutex synchronization. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2022-48869 depends largely on the deployment of Linux systems utilizing the gadgetfs USB gadget filesystem. This vulnerability could be leveraged by a local attacker or malicious process to cause memory corruption, potentially leading to system crashes (denial of service) or privilege escalation, which could compromise system integrity and confidentiality. Organizations relying on Linux servers, embedded devices, or IoT systems that expose USB gadget functionality are at higher risk. In critical infrastructure sectors such as manufacturing, telecommunications, and government, where Linux-based embedded systems are common, exploitation could disrupt operations or facilitate lateral movement within networks. Given the requirement for local access and specific filesystem operations, remote exploitation is unlikely without prior compromise. Nonetheless, the vulnerability poses a risk to endpoint security and could be a stepping stone for attackers to escalate privileges or destabilize systems. European organizations with stringent security and compliance requirements should prioritize patching to maintain system integrity and prevent potential exploitation.

1. Apply the official Linux kernel patches that introduce mutex-based serialization between gadgetfs_fill_super() and gadgetfs_kill_sb() to eliminate the race condition. Monitor Linux kernel updates and deploy them promptly. 2. Audit and restrict access to USB gadget filesystem mounting and unmounting operations to trusted users and processes only, minimizing the risk of malicious exploitation. 3. Employ kernel hardening techniques such as Kernel Address Space Layout Randomization (KASLR) and Kernel Page Table Isolation (KPTI) to reduce the impact of potential kernel memory corruption. 4. Utilize security modules like SELinux or AppArmor to enforce strict policies around USB gadget filesystem usage and limit the capabilities of processes that can interact with gadgetfs. 5. Implement continuous monitoring and anomaly detection on Linux systems to identify unusual mounting/unmounting activity or kernel crashes indicative of exploitation attempts. 6. For embedded and IoT devices, ensure firmware updates include the patched kernel and verify update mechanisms are secure and reliable. 7. Conduct regular security assessments and penetration testing focusing on local privilege escalation vectors to detect and remediate similar vulnerabilities proactively.