linux-kernel - Re: [PATCH] tty: serial: fsl

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Message-ID: <2971e87a-bf8e-f42e-cf8d-f90d9db9499f@suse.cz>
Date:   Mon, 6 Apr 2020 06:27:52 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     Michael Walle <michael@...le.cc>, linux-kernel@...r.kernel.org,
        linux-serial@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Colin Ian King <colin.king@...onical.com>,
        NXP Linux Team <linux-imx@....com>
Subject: Re: [PATCH] tty: serial: fsl_lpuart: make coverity happy

On 03. 04. 20, 19:49, Michael Walle wrote:
> Coverity reports the following:
> 
>   var_compare_op: Comparing chan to null implies that chan might be null.
> 
>   1234        if (chan)
>   1235                dmaengine_terminate_all(chan);
>   1236
> 
>   Dereference after null check (FORWARD_NULL)
>   var_deref_op: Dereferencing null pointer chan.
> 
>   1237        dma_unmap_sg(chan->device->dev, &sport->rx_sgl, 1, DMA_FROM_DEVICE);
> 
> Technically, this is correct. But lpuart_dma_rx_free() is guarded by
> lpuart_dma_rx_use which is only true if there is a dma channel, see
> lpuart_rx_dma_startup(). In any way, this looks bogus. So remove
> the superfluous "if (chan)" check and make coverity happy.
> 
> Fixes: a092ab25fdaa ("tty: serial: fsl_lpuart: fix DMA mapping")
> Signed-off-by: Michael Walle <michael@...le.cc>
> Reported-by: Colin Ian King <colin.king@...onical.com>

Acked-by: Jiri Slaby <jslaby@...e.cz>

> ---
>  drivers/tty/serial/fsl_lpuart.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
> index 4cb04d8bf034..83d803729d23 100644
> --- a/drivers/tty/serial/fsl_lpuart.c
> +++ b/drivers/tty/serial/fsl_lpuart.c
> @@ -1210,9 +1210,7 @@ static void lpuart_dma_rx_free(struct uart_port *port)
>  					struct lpuart_port, port);
>  	struct dma_chan *chan = sport->dma_rx_chan;
>  
> -	if (chan)
> -		dmaengine_terminate_all(chan);
> -
> +	dmaengine_terminate_all(chan);
>  	dma_unmap_sg(chan->device->dev, &sport->rx_sgl, 1, DMA_FROM_DEVICE);
>  	kfree(sport->rx_ring.buf);
>  	sport->rx_ring.tail = 0;
> 

thanks,
-- 
js
suse labs