Subject: [PATCH 3/4] tty/serial: at91: prevent null dereference in tasklet function

From: [email-masked] (Greg KH)
Date: Tue, 7 Jan 2014 17:11:37 -0800

On Tue, Jan 07, 2014 at 11:45:08AM +0100, Nicolas Ferre wrote:
> From: Marek Roszko <[email-masked]>
> 
> Something asks a tasklet to be scheduled when the uart port is closed.

What is that something?  Shouldn't you track that down and find the real
problem here?

> Need to supress the kernel panic for now by checking if the port is NULL or
> not.
> 
> Signed-off-by: Marek Roszko <[email-masked]>
> Acked-by: Leilei Zhao <[email-masked]>
> Cc: <[email-masked]> # v3.12
> Signed-off-by: Nicolas Ferre <[email-masked]>
> ---
>  drivers/tty/serial/atmel_serial.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
> index c421d11b3d4c..6e68486c83cb 100644
> --- a/drivers/tty/serial/atmel_serial.c
> +++ b/drivers/tty/serial/atmel_serial.c
> @@ -1360,6 +1360,10 @@ static void atmel_tasklet_func(unsigned long data)
>  	unsigned int status;
>  	unsigned int status_change;
>  
> +	if(!port->state || !port->state->port.tty)
> +		/* uart has been closed */
> +		return;

Did you really test this?

How about running it through checkpatch?

thanks,

greg k-h