dmaengine: fsl-edma: use struct_size() helper

Make use of the struct_size() helper instead of an open-coded version,
in order to avoid any potential type mistakes or integer overflows that,
in the worst scenario, could lead to heap overflows.

Signed-off-by: Yu Liao <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Vinod Koul <[email protected]>

Author: yuliao0214

drivers/dma/fsl-edma.c

@@ -270,9 +270,8 @@ static int fsl_edma_probe(struct platform_device *pdev)
 	struct device_node *np = pdev->dev.of_node;
 	struct fsl_edma_engine *fsl_edma;
 	const struct fsl_edma_drvdata *drvdata = NULL;
-	struct fsl_edma_chan *fsl_chan;
 	struct edma_regs *regs;
-	int len, chans;
+	int chans;
 	int ret, i;
 
 	if (of_id)
@@ -288,8 +287,8 @@ static int fsl_edma_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	len = sizeof(*fsl_edma) + sizeof(*fsl_chan) * chans;
-	fsl_edma = devm_kzalloc(&pdev->dev, len, GFP_KERNEL);
+	fsl_edma = devm_kzalloc(&pdev->dev, struct_size(fsl_edma, chans, chans),
+				GFP_KERNEL);
 	if (!fsl_edma)
 		return -ENOMEM;