Re: [PATCH] serial: digicolor: fix use-after-free on driver unbind

[Baruch Siach <baruch@tkos.co.il>]

Hi Junrui,

On Mon, Dec 22 2025, Junrui Luo wrote:
> The digicolor_uart_console_write() function accesses the global
> digicolor_ports[] array to retrieve the uart port pointer, which
> can lead to a use-after-free if the console write occurs after
> the port has been removed via unbind.
>
> digicolor_uart_remove() leaves a dangling pointer in the array.
>
> Fix by clearing the array entry in digicolor_uart_remove() and
> adding a NULL check in digicolor_uart_console_write().

Thanks for the patch.

Is this .write/.remove callbacks race actually possible? Can you refer
me to similar fixes in other drivers?

> Reported-by: Yuhao Jiang <danisjiang@gmail.com>

Where can I find this report?

Thanks,
baruch

> Reported-by: Junrui Luo <moonafterrain@outlook.com>
> Fixes: 5930cb3511df ("serial: driver for Conexant Digicolor USART")
> Signed-off-by: Junrui Luo <moonafterrain@outlook.com>
> ---
>  drivers/tty/serial/digicolor-usart.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/tty/serial/digicolor-usart.c b/drivers/tty/serial/digicolor-usart.c
> index d2482df5cb9b..5861be2072c4 100644
> --- a/drivers/tty/serial/digicolor-usart.c
> +++ b/drivers/tty/serial/digicolor-usart.c
> @@ -397,6 +397,9 @@ static void digicolor_uart_console_write(struct console *co, const char *c,
>  	unsigned long flags;
>  	int locked = 1;
>  
> +	if (!port)
> +		return;
> +
>  	if (oops_in_progress)
>  		locked = uart_port_trylock_irqsave(port, &flags);
>  	else
> @@ -508,6 +511,7 @@ static void digicolor_uart_remove(struct platform_device *pdev)
>  	struct uart_port *port = platform_get_drvdata(pdev);
>  
>  	uart_remove_one_port(&digicolor_uart, port);
> +	digicolor_ports[port->line] = NULL;
>  }
>  
>  static const struct of_device_id digicolor_uart_dt_ids[] = {
>
> ---
> base-commit: ea1013c1539270e372fc99854bc6e4d94eaeff66
> change-id: 20251222-fixes-74e6b26513d1
>
> Best regards,

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