2019-01-04 18:45:15

by Gustavo A. R. Silva

Subject: [PATCH] dmaengine: st_fdma: use struct_size() in kzalloc()

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 <[email protected]>
---
drivers/dma/st_fdma.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/dma/st_fdma.c b/drivers/dma/st_fdma.c
index 07c20aa2e955..df6b73028ecb 100644
--- a/drivers/dma/st_fdma.c
+++ b/drivers/dma/st_fdma.c
@@ -243,8 +243,7 @@ static struct st_fdma_desc *st_fdma_alloc_desc(struct st_fdma_chan *fchan,
struct st_fdma_desc *fdesc;
int i;

- fdesc = kzalloc(sizeof(*fdesc) +
- sizeof(struct st_fdma_sw_node) * sg_len, GFP_NOWAIT);
+ fdesc = kzalloc(struct_size(fdesc, node, sg_len), GFP_NOWAIT);
if (!fdesc)
return NULL;

--
2.20.1

2019-01-07 08:52:14

by Patrice CHOTARD

Subject: Re: [PATCH] dmaengine: st_fdma: use struct_size() in kzalloc()

Hi Gustavo

On 1/4/19 7:43 PM, 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 <[email protected]>
> ---
> drivers/dma/st_fdma.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/dma/st_fdma.c b/drivers/dma/st_fdma.c
> index 07c20aa2e955..df6b73028ecb 100644
> --- a/drivers/dma/st_fdma.c
> +++ b/drivers/dma/st_fdma.c
> @@ -243,8 +243,7 @@ static struct st_fdma_desc *st_fdma_alloc_desc(struct st_fdma_chan *fchan,
> struct st_fdma_desc *fdesc;
> int i;
>
> - fdesc = kzalloc(sizeof(*fdesc) +
> - sizeof(struct st_fdma_sw_node) * sg_len, GFP_NOWAIT);
> + fdesc = kzalloc(struct_size(fdesc, node, sg_len), GFP_NOWAIT);
> if (!fdesc)
> return NULL;
>
>


Acked-by: Patrice Chotard <[email protected]>

Thanks

2019-01-09 22:02:27

by Gustavo A. R. Silva

Subject: Re: [PATCH] dmaengine: st_fdma: use struct_size() in kzalloc()

On 1/7/19 2:50 AM, Patrice CHOTARD wrote:
> Hi Gustavo
>
> On 1/4/19 7:43 PM, 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:
>>

[..]

>>
>> Signed-off-by: Gustavo A. R. Silva <[email protected]>
>> ---
>> drivers/dma/st_fdma.c | 3 +--
>> 1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/drivers/dma/st_fdma.c b/drivers/dma/st_fdma.c
>> index 07c20aa2e955..df6b73028ecb 100644
>> --- a/drivers/dma/st_fdma.c
>> +++ b/drivers/dma/st_fdma.c
>> @@ -243,8 +243,7 @@ static struct st_fdma_desc *st_fdma_alloc_desc(struct st_fdma_chan *fchan,
>> struct st_fdma_desc *fdesc;
>> int i;
>>
>> - fdesc = kzalloc(sizeof(*fdesc) +
>> - sizeof(struct st_fdma_sw_node) * sg_len, GFP_NOWAIT);
>> + fdesc = kzalloc(struct_size(fdesc, node, sg_len), GFP_NOWAIT);
>> if (!fdesc)
>> return NULL;
>>
>>
>
>
> Acked-by: Patrice Chotard <[email protected]>
>

Thanks, Patrice.

--
Gustavo