Re: [PATCH RFC] dmaengine: fsl-edma: check channel acquisition before use

[Frank Li]

On Fri, Sep 11, 2026 at 02:09:02PM +0800, Slavin Liu wrote:
> dma_get_slave_channel() can return NULL when acquiring a channel fails,
> for example if fsl_edma_alloc_chan_resources() cannot request an IRQ.
> fsl_edma3_xlate() dereferences that return value to update privatecnt.
>
> Acquire and check the channel before publishing its source ID and
> request parameters. A NULL-only check after the existing source-ID
> assignment would leave the failed request marked as in use, causing
> fsl_edma_srcid_in_use() to reject a subsequent request for that source.
> The channel resource-allocation callback does not consume these request
> parameters, so set them only after acquisition succeeds. The existing
> scoped mutex release and successful-channel return are preserved.
>
> Detected by static analysis and reviewed with AI-assisted source auditing.
>
> Fixes: 72f5801a4e2b ("dmaengine: fsl-edma: integrate v3 support")
> Assisted-by: LLM
> Signed-off-by: Slavin Liu <bolin.liu@xxxxxxxxxx>
> ---

Next time, remove RFC for such patch

Reviewed-by: Frank Li <Frank.Li@xxxxxxx>

>  drivers/dma/fsl-edma-main.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma/fsl-edma-main.c b/drivers/dma/fsl-edma-main.c
> index d9fb717b5b53..6934ac882697 100644
> --- a/drivers/dma/fsl-edma-main.c
> +++ b/drivers/dma/fsl-edma-main.c
> @@ -326,13 +326,16 @@ static struct dma_chan *fsl_edma3_xlate(struct of_phandle_args *dma_spec,
>  		if ((dma_spec->args[2] & FSL_EDMA_ODD_CH) && !(i & 0x1))
>  			continue;
>
> +		chan = dma_get_slave_channel(chan);
> +		if (!chan)
> +			return NULL;
> +
>  		fsl_chan->srcid = dma_spec->args[0];
>  		fsl_chan->priority = dma_spec->args[1];
>  		fsl_chan->is_rxchan = dma_spec->args[2] & FSL_EDMA_RX;
>  		fsl_chan->is_remote = dma_spec->args[2] & FSL_EDMA_REMOTE;
>  		fsl_chan->is_multi_fifo = dma_spec->args[2] & FSL_EDMA_MULTI_FIFO;
>
> -		chan = dma_get_slave_channel(chan);
>  		chan->device->privatecnt++;
>  		return chan;
>  	}