Vulnerability CVE-2023-52456
Published: 2024-02-23

Description:
In the Linux kernel, the following vulnerability has been resolved:

serial: imx: fix tx statemachine deadlock

When using the serial port as RS485 port, the tx statemachine is used to
control the RTS pin to drive the RS485 transceiver TX_EN pin. When the
TTY port is closed in the middle of a transmission (for instance during
userland application crash), imx_uart_shutdown disables the interface
and disables the Transmission Complete interrupt. afer that,
imx_uart_stop_tx bails on an incomplete transmission, to be retriggered
by the TC interrupt. This interrupt is disabled and therefore the tx
statemachine never transitions out of SEND. The statemachine is in
deadlock now, and the TX_EN remains low, making the interface useless.

imx_uart_stop_tx now checks for incomplete transmission AND whether TC
interrupts are enabled before bailing to be retriggered. This makes sure
the state machine handling is reached, and is properly set to
WAIT_AFTER_SEND.

 References:
https://git.kernel.org/stable/c/6e04a9d30509fb53ba6df5d655ed61d607a7cfda
https://git.kernel.org/stable/c/ff168d4fdb0e1ba35fb413a749b3d6cce918ec19
https://git.kernel.org/stable/c/63ee7be01a3f7d28b1ea8b8d7944f12bb7b0ed06
https://git.kernel.org/stable/c/763cd68746317b5d746dc2649a3295c1efb41181
https://git.kernel.org/stable/c/9a662d06c22ddfa371958c2071dc350436be802b
https://git.kernel.org/stable/c/78d60dae9a0c9f09aa3d6477c94047df2fe6f7b0
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