[PATCH] dm-switch: use struct_size() in kzalloc()

[PATCH] dm-switch: use struct_size() in kzalloc()

[Gustavo A. R. Silva]

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/md/dm-switch.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/md/dm-switch.c b/drivers/md/dm-switch.c
index fae35caf3672..8a0f057b8122 100644
--- a/drivers/md/dm-switch.c
+++ b/drivers/md/dm-switch.c
@@ -61,8 +61,7 @@ static struct switch_ctx *alloc_switch_ctx(struct dm_target *ti, unsigned nr_pat
 {
 	struct switch_ctx *sctx;
 
-	sctx = kzalloc(sizeof(struct switch_ctx) + nr_paths * sizeof(struct switch_path),
-		       GFP_KERNEL);
+	sctx = kzalloc(struct_size(sctx, path_list, nr_paths), GFP_KERNEL);
 	if (!sctx)
 		return NULL;
 
-- 
2.20.1

Re: [PATCH] dm-switch: use struct_size() in kzalloc()

[Gustavo A. R. Silva]

Hi all,

Friendly ping:

Who can take this?

Thanks
--
Gustavo

On 1/8/19 10:02 AM, 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/md/dm-switch.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/md/dm-switch.c b/drivers/md/dm-switch.c
> index fae35caf3672..8a0f057b8122 100644
> --- a/drivers/md/dm-switch.c
> +++ b/drivers/md/dm-switch.c
> @@ -61,8 +61,7 @@ static struct switch_ctx *alloc_switch_ctx(struct dm_target *ti, unsigned nr_pat
>  {
>  	struct switch_ctx *sctx;
>  
> -	sctx = kzalloc(sizeof(struct switch_ctx) + nr_paths * sizeof(struct switch_path),
> -		       GFP_KERNEL);
> +	sctx = kzalloc(struct_size(sctx, path_list, nr_paths), GFP_KERNEL);
>  	if (!sctx)
>  		return NULL;
>  
> 

Re: dm-switch: use struct_size() in kzalloc()

[Mike Snitzer]

On Thu, Feb 21 2019 at 10:27am -0500,
Gustavo A. R. Silva <gustavo@embeddedor.com> wrote:

> Hi all,
> 
> Friendly ping:
> 
> Who can take this?

I've picked it up for 5.1:
https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-5.1&id=042f96ad4c5a369307df2a840fd943a4b080c3d1

Thanks,
Mike

Re: dm-switch: use struct_size() in kzalloc()

[Gustavo A. R. Silva]

On 2/21/19 9:40 AM, Mike Snitzer wrote:
> On Thu, Feb 21 2019 at 10:27am -0500,
> Gustavo A. R. Silva <gustavo@embeddedor.com> wrote:
> 
>> Hi all,
>>
>> Friendly ping:
>>
>> Who can take this?
> 
> I've picked it up for 5.1:
> https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-5.1&id=042f96ad4c5a369307df2a840fd943a4b080c3d1
> 

Great. :)

Thank you, Mike.

--
Gustavo