Patchwork dmaengine: fsl-edma: use struct_size() in kzalloc()

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Submitter Gustavo A. R. Silva
Date Jan. 4, 2019, 9:25 p.m.
Message ID <20190104212545.GA16927@embeddedor>
Download mbox | patch
Permalink /patch/693223/
State New
Headers show

Comments

Gustavo A. R. Silva - Jan. 4, 2019, 9:25 p.m.
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@embeddedor.com>
---
 drivers/dma/fsl-edma-common.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)
Angelo Dureghello - Jan. 6, 2019, 7:40 p.m.
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@embeddedor.com>
> ---
>  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@sysam.it>

  
> -- 
> 2.20.1
>
Gustavo A. R. Silva - Jan. 6, 2019, 8:33 p.m.
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@embeddedor.com>
>> ---
>>   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@sysam.it>
> 

Thanks, Angelo.

--
Gustavo
Vinod Koul - Jan. 7, 2019, 12:41 p.m.
On 04-01-19, 15:25, 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.

Applied, thanks

Patch

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;