2019-01-09 17:37:34

by Gustavo A. R. Silva

Subject: [PATCH] s390/hypfs: 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]>
---
arch/s390/hypfs/hypfs_diag0c.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/s390/hypfs/hypfs_diag0c.c b/arch/s390/hypfs/hypfs_diag0c.c
index cebf05150cc1..9c398bf0ddc6 100644
--- a/arch/s390/hypfs/hypfs_diag0c.c
+++ b/arch/s390/hypfs/hypfs_diag0c.c
@@ -54,8 +54,7 @@ static void *diag0c_store(unsigned int *count)
if (!cpu_vec)
goto fail_put_online_cpus;
/* Note: Diag 0c needs 8 byte alignment and real storage */
- diag0c_data = kzalloc(sizeof(struct hypfs_diag0c_hdr) +
- cpu_count * sizeof(struct hypfs_diag0c_entry),
+ diag0c_data = kzalloc(struct_size(diag0c_data, entry, cpu_count),
GFP_KERNEL | GFP_DMA);
if (!diag0c_data)
goto fail_kfree_cpu_vec;
--
2.20.1

2019-01-10 07:21:11

by Heiko Carstens

Subject: Re: [PATCH] s390/hypfs: Use struct_size() in kzalloc()

On Wed, Jan 09, 2019 at 11:35:41AM -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 <[email protected]>
> ---
> arch/s390/hypfs/hypfs_diag0c.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)

Applied, thanks!