Re: [PATCH] ASoC: davinci-mcasp: Fix dma_chan refcnt leak when getting dma type

[Peter Ujfalusi]

On 25/04/2020 15.48, Xiyu Yang wrote:
> davinci_mcasp_get_dma_type() invokes dma_request_chan(), which returns a
> reference of the specified dma_chan object to "chan" with increased
> refcnt.
> 
> When davinci_mcasp_get_dma_type() returns, local variable "chan" becomes
> invalid, so the refcount should be decreased to keep refcount balanced.
> 
> The reference counting issue happens in one exception handling path of
> davinci_mcasp_get_dma_type(). When chan device is NULL, the function
> forgets to decrease the refcnt increased by dma_request_chan(), causing
> a refcnt leak.
> 
> Fix this issue by calling dma_release_channel() when chan device is
> NULL.
> 
> Signed-off-by: Xiyu Yang <xiyuyang19@xxxxxxxxxxxx>
> Signed-off-by: Xin Tan <tanxin.ctf@xxxxxxxxx>
> ---
>  sound/soc/ti/davinci-mcasp.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/sound/soc/ti/davinci-mcasp.c b/sound/soc/ti/davinci-mcasp.c
> index 734ffe925c4d..7a7db743dc5b 100644
> --- a/sound/soc/ti/davinci-mcasp.c
> +++ b/sound/soc/ti/davinci-mcasp.c
> @@ -1896,8 +1896,10 @@ static int davinci_mcasp_get_dma_type(struct davinci_mcasp *mcasp)
>  				PTR_ERR(chan));
>  		return PTR_ERR(chan);
>  	}
> -	if (WARN_ON(!chan->device || !chan->device->dev))
> +	if (WARN_ON(!chan->device || !chan->device->dev)) {
> +		dma_release_channel(chan);
>  		return -EINVAL;
> +	}

If we get a channel then chan->device and chan->device->dev never NULL,
it can not be.
I think the reason why this is here is that static checkers tends to
scream at us.

Acked-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx>

>  
>  	if (chan->device->dev->of_node)
>  		ret = of_property_read_string(chan->device->dev->of_node,
> 

- PÃter

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