CVE-2023-52456: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-52456 is a vulnerability in the Linux kernel's UART driver handling RS485 communication, discovered in late 2023. The vulnerability affects Linux kernel versions from 5.9.0 up to (excluding) 6.7.2, including versions 5.10.x, 5.15.x, 6.1.x, and 6.6.x. The issue was officially published on February 23, 2024, and received a CVSS v3.1 base score of 5.5 (Medium) (NVD).

The vulnerability occurs in the serial IMX driver when using the serial port as RS485 port. The tx statemachine, which controls the RTS pin to drive the RS485 transceiver TX_EN pin, can enter a deadlock state. This happens when the TTY port is closed during an ongoing transmission, such as during a userland application crash. The imx_uart_shutdown function disables the interface and the Transmission Complete interrupt, causing the tx statemachine to never transition out of the SEND state (Kernel Patch).

When exploited, this vulnerability results in the tx statemachine becoming deadlocked, with the TX_EN remaining low, rendering the RS485 interface unusable. This creates a denial of service condition specifically affecting RS485 communication capabilities (NVD).

The issue has been fixed in the Linux kernel through a patch that modifies the imx_uart_stop_tx function to check for both incomplete transmission AND whether TC interrupts are enabled before attempting retrigger. This ensures proper state machine handling and transition to WAIT_AFTER_SEND state. The fix has been backported to multiple kernel versions (Kernel Patch).