dmaengine: mcf-edma: Use struct_size()

[PATCH] dmaengine: mcf-edma: Use struct_size()

Posted by Christophe JAILLET 2 years, 9 months ago

Use struct_size() instead of hand writing it.
This is less verbose and more informative.

'mcf_chan' is now unused and can be removed. In fact, it is shadowed by
another variable in the 'for' loop below. Keep this one.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
It will also help scripts when __counted_by macro will be added.
See [1].

[1]: https://lore.kernel.org/all/6453f739.170a0220.62695.7785@mx.google.com/
---
 drivers/dma/mcf-edma.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/mcf-edma.c b/drivers/dma/mcf-edma.c
index ebd8733f72ad..28304dd8763a 100644
--- a/drivers/dma/mcf-edma.c
+++ b/drivers/dma/mcf-edma.c
@@ -180,9 +180,8 @@ static int mcf_edma_probe(struct platform_device *pdev)
 {
 	struct mcf_edma_platform_data *pdata;
 	struct fsl_edma_engine *mcf_edma;
-	struct fsl_edma_chan *mcf_chan;
 	struct edma_regs *regs;
-	int ret, i, len, chans;
+	int ret, i, chans;
 
 	pdata = dev_get_platdata(&pdev->dev);
 	if (!pdata) {
@@ -191,8 +190,8 @@ static int mcf_edma_probe(struct platform_device *pdev)
 	}
 
 	chans = pdata->dma_channels;
-	len = sizeof(*mcf_edma) + sizeof(*mcf_chan) * chans;
-	mcf_edma = devm_kzalloc(&pdev->dev, len, GFP_KERNEL);
+	mcf_edma = devm_kzalloc(&pdev->dev, struct_size(mcf_edma, chans, chans),
+				GFP_KERNEL);
 	if (!mcf_edma)
 		return -ENOMEM;
 
-- 
2.34.1

Re: [PATCH] dmaengine: mcf-edma: Use struct_size()

Posted by Vinod Koul 2 years, 5 months ago

On Sat, 06 May 2023 18:22:06 +0200, Christophe JAILLET wrote:
> Use struct_size() instead of hand writing it.
> This is less verbose and more informative.
> 
> 'mcf_chan' is now unused and can be removed. In fact, it is shadowed by
> another variable in the 'for' loop below. Keep this one.
> 
> 
> [...]

Applied, thanks!

[1/1] dmaengine: mcf-edma: Use struct_size()
      commit: 923b138388928ade722cba86c55145f3dfac1cab

Best regards,
-- 
~Vinod

Re: [PATCH] dmaengine: mcf-edma: Use struct_size()

Posted by Dan Carpenter 2 years, 9 months ago

On Sat, May 06, 2023 at 06:22:06PM +0200, Christophe JAILLET wrote:
> Use struct_size() instead of hand writing it.
> This is less verbose and more informative.
> 
> 'mcf_chan' is now unused and can be removed. In fact, it is shadowed by
> another variable in the 'for' loop below. Keep this one.
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
> It will also help scripts when __counted_by macro will be added.
> See [1].
> 
> [1]: https://lore.kernel.org/all/6453f739.170a0220.62695.7785@mx.google.com/

Of course, the main selling point of struct_size() for me is that it
protects you against integer overflows.  Open coding the math might end
up giving you a size which is smaller than expected but struct_size()
will give you ULONG_MAX in that same situation.  The allocation will
fail as expected.  #Safe.

Even when the open coded math is safe, this is easier to audit in an
automated way.

regards,
dan carpenter