CVE-2023-53094 is a vulnerability identified in the Linux kernel specifically related to the serial driver for the Freescale LPUART (Low Power Universal Asynchronous Receiver/Transmitter) hardware. The issue arises from a race condition during the shutdown of the RX DMA (Direct Memory Access) process. The vulnerability occurs because the DMA completion interrupt can be triggered while the DMA shutdown sequence is still in progress. This leads to a situation where a timer function (lpuart_timer_func) attempts to access a NULL pointer (sport->dma_rx_desc) due to the timer being restarted after the DMA descriptors have been freed. The kernel then encounters a NULL pointer dereference, causing a potential kernel panic or system crash. The root cause is the improper synchronization between the timer deletion (del_timer_sync()) and the DMA shutdown sequence. The fix involves folding the del_timer_sync() call into the lpuart_dma_rx_free() function after dmaengine_terminate_sync() to ensure that the timer cannot be restarted after the DMA descriptors have been freed, thus preventing the race condition and subsequent NULL pointer dereference. This vulnerability affects specific Linux kernel versions identified by their commit hashes, indicating it is present in certain kernel builds prior to the fix. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet.

For European organizations, this vulnerability can have significant implications, particularly for those relying on Linux-based systems in embedded environments or industrial control systems where Freescale LPUART hardware is used. The kernel NULL pointer dereference can lead to system crashes or denial of service (DoS), impacting availability of critical systems. This is especially concerning for sectors such as manufacturing, telecommunications, transportation, and critical infrastructure where Linux is commonly deployed on specialized hardware. Although the vulnerability does not directly lead to privilege escalation or data leakage, the resulting instability and potential downtime can disrupt operations, cause financial losses, and affect service continuity. Additionally, systems that require high availability or real-time processing may be particularly vulnerable to the effects of unexpected kernel panics. Since no known exploits exist yet, the immediate risk is moderate, but the potential for future exploitation remains if attackers develop techniques to trigger the race condition remotely or via local access.

European organizations should prioritize updating their Linux kernel to versions that include the fix for CVE-2023-53094. Specifically, they should ensure that their kernel source or distribution vendor has integrated the patch that folds del_timer_sync() into lpuart_dma_rx_free() after dmaengine_terminate_sync(). For embedded or specialized systems where kernel updates are less frequent, organizations should coordinate with hardware vendors or system integrators to obtain patched firmware or kernel images. Additionally, organizations should audit their systems to identify any usage of the Freescale LPUART serial driver and assess exposure. Implementing monitoring for kernel panics or unusual system reboots can help detect attempts to trigger this vulnerability. Where possible, restricting access to systems with vulnerable kernels and limiting local user privileges can reduce the risk of exploitation. Finally, organizations should maintain robust backup and recovery procedures to minimize downtime in case of crashes caused by this vulnerability.