CVE-2024-46785 is a vulnerability identified in the Linux kernel's eventfs subsystem, specifically related to the handling of SRCU (Sleepable Read-Copy Update) protected list variables. The root cause is a null pointer dereference triggered when the variable 'ei_child' is set to LIST_POISON1, indicating that the list element has been removed by the eventfs_remove_rec function. Accessing the member 'ei_child->is_freed' after the list removal leads to a kernel panic due to an invalid memory access. The vulnerability can be reproduced by concurrently executing two loops: one rapidly adding and removing kprobe events via the debugfs interface, and another listing the kprobe events directory. This causes a race condition that triggers the null pointer dereference and consequent kernel crash. The kernel panic logs show an 'Unable to handle kernel paging request' error, with detailed ARM64 architecture-specific memory abort information, confirming the invalid memory access. The vulnerability affects multiple Linux kernel versions as indicated by the affected commit hashes. No known exploits are currently reported in the wild. The issue was reported by Chi Zhiling and has been addressed by replacing the unsafe list removal with the safer list_del_rcu() function, which is appropriate for SRCU-protected lists, preventing the use-after-free condition. This vulnerability is a denial-of-service (DoS) type, causing system instability and crashes when triggered. It requires local access to the debugfs tracing interface, which is typically restricted to privileged users, limiting the attack surface to authorized users or processes. However, on systems where debugfs is exposed or accessible to untrusted users, this vulnerability could be exploited to cause kernel panics and system outages.

For European organizations, the impact of CVE-2024-46785 primarily involves potential denial-of-service conditions on Linux-based systems. Many European enterprises, government agencies, and critical infrastructure operators rely heavily on Linux servers and embedded devices. A kernel panic induced by this vulnerability would cause system crashes, leading to service interruptions, potential data loss, and operational downtime. This could affect cloud service providers, telecommunications infrastructure, financial institutions, and industrial control systems that utilize Linux kernels vulnerable to this flaw. Although exploitation requires local access and interaction with debugfs, insider threats or compromised accounts could leverage this vulnerability to disrupt services. Additionally, development and testing environments that enable debugfs for tracing might be more exposed. The vulnerability does not directly lead to privilege escalation or remote code execution but can be leveraged as part of a broader attack chain to degrade system availability. Organizations with high availability requirements or those operating critical services should prioritize patching to avoid service disruptions. The lack of known exploits reduces immediate risk, but the vulnerability's presence in widely deployed Linux kernels necessitates proactive mitigation.

1. Apply the official Linux kernel patches that replace the unsafe list removal with list_del_rcu() in the eventfs subsystem to eliminate the null pointer dereference and race condition. 2. Restrict access to the debugfs filesystem, especially the tracing and kprobe interfaces, to trusted and authorized users only. Consider mounting debugfs with restrictive permissions or disabling it entirely in production environments where tracing is not required. 3. Implement kernel lockdown features and mandatory access controls (e.g., SELinux, AppArmor) to limit the ability of unprivileged users to interact with kernel tracing interfaces. 4. Monitor system logs for kernel panics or unusual activity related to debugfs and tracing events to detect potential exploitation attempts. 5. For environments requiring tracing, use controlled and isolated test systems rather than production servers to minimize risk. 6. Educate system administrators and security teams about the vulnerability and ensure timely deployment of kernel updates across all Linux systems. 7. Employ system integrity monitoring tools to detect unauthorized changes or suspicious kernel module activities that could indicate exploitation attempts.