2019-01-08 16:47:23

by Gustavo A. R. Silva

Subject: [PATCH] dm-switch: 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/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

2019-02-21 15:28:17

by Gustavo A. R. Silva

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

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 <[email protected]>
> ---
> 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;
>
>

2019-02-21 15:42:00

by Mike Snitzer

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

On Thu, Feb 21 2019 at 10:27am -0500,
Gustavo A. R. Silva <[email protected]> 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

2019-02-21 15:44:36

by Gustavo A. R. Silva

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

On 2/21/19 9:40 AM, Mike Snitzer wrote:
> On Thu, Feb 21 2019 at 10:27am -0500,
> Gustavo A. R. Silva <[email protected]> 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