Re: [PATCH] dmaengine: fsl-edma: use struct_size() in kzalloc()

From: Gustavo A. R. Silva
Date: Sun Jan 06 2019 - 15:38:50 EST

On 1/6/19 1:40 PM, Angelo Dureghello wrote:
On Fri, Jan 04, 2019 at 03:25:45PM -0600, Gustavo A. R. Silva wrote:
One of the more common cases of allocation size calculations is finding the
size of a structure that has a zero-sized array at the end, along with memory
for some number of elements for that array. For example:

struct foo {
int stuff;
void *entry[];

instance = kzalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);

Instead of leaving these open-coded and prone to type mistakes, we can now
use the new struct_size() helper:

instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
drivers/dma/fsl-edma-common.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/dma/fsl-edma-common.c b/drivers/dma/fsl-edma-common.c
index 8876c4c1bb2c..fe529100674f 100644
--- a/drivers/dma/fsl-edma-common.c
+++ b/drivers/dma/fsl-edma-common.c
@@ -339,9 +339,7 @@ static struct fsl_edma_desc *fsl_edma_alloc_desc(struct fsl_edma_chan *fsl_chan,
struct fsl_edma_desc *fsl_desc;
int i;
- fsl_desc = kzalloc(sizeof(*fsl_desc) +
- sizeof(struct fsl_edma_sw_tcd) *
- sg_len, GFP_NOWAIT);
+ fsl_desc = kzalloc(struct_size(fsl_desc, tcd, sg_len), GFP_NOWAIT);
if (!fsl_desc)
return NULL;

Tested-by: Angelo Dureghello <angelo@xxxxxxxx>

Thanks, Angelo.