Re: [PATCH v4 5/5] serial/8250: Only use fifo after the port is initialized in console_write

[Jiri Slaby]

On 16. 03. 22, 15:36, Wander Lairson Costa wrote:
> The serial driver set the value of uart_8250_port.fcr in the function
> serial8250_config_port, but only writes the value to the controller
> register later in the initalization code.
>
> That opens a small window in which is not safe to use the fifo for
> console write.
>
> Make sure the port is initialized correctly before reading the FCR
> cached value.
>
> Unfortunately, I lost track of who originally reported the issue. If
> s/he is reading this, please speak up so I can give you the due credit.
>
> Signed-off-by: Wander Lairson Costa <wander@xxxxxxxxxx>
> ---
>   drivers/tty/serial/8250/8250_port.c | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
> index 4acf620be241..7e2227161555 100644
> --- a/drivers/tty/serial/8250/8250_port.c
> +++ b/drivers/tty/serial/8250/8250_port.c
> @@ -3416,6 +3416,7 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s,
>   		!(up->capabilities & UART_CAP_MINI) &&
>   		up->tx_loadsz > 1 &&
>   		(up->fcr & UART_FCR_ENABLE_FIFO) &&
> +		test_bit(TTY_PORT_INITIALIZED, &port->state->port.iflags) &&

Cannot be port->state be NULL sometimes here?

>   		/*
>   		 * After we put a data in the fifo, the controller will send
>   		 * it regardless of the CTS state. Therefore, only use fifo


--
js
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