linux-kernel - Re: [PATCH 3/4] tty/serial: at91: prevent null dereference in tasklet function

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Date:	Tue, 7 Jan 2014 17:11:37 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Nicolas Ferre <nicolas.ferre@...el.com>
Cc:	Leilei Zhao <leilei.zhao@...el.com>, mark.roszko@...il.com,
	mdeneen@...il.com, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH 3/4] tty/serial: at91: prevent null dereference in
 tasklet function

On Tue, Jan 07, 2014 at 11:45:08AM +0100, Nicolas Ferre wrote:
> From: Marek Roszko <mark.roszko@...il.com>
> 
> 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 <mark.roszko@...il.com>
> Acked-by: Leilei Zhao <leilei.zhao@...el.com>
> Cc: <stable@...r.kernel.org> # v3.12
> Signed-off-by: Nicolas Ferre <nicolas.ferre@...el.com>
> ---
>  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
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