[PATCH] IB/core: Use struct_size() in kzalloc()

[PATCH] IB/core: 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/infiniband/core/sa_query.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/infiniband/core/sa_query.c b/drivers/infiniband/core/sa_query.c
index 97e6d7b69abf..7925e45ea88a 100644
--- a/drivers/infiniband/core/sa_query.c
+++ b/drivers/infiniband/core/sa_query.c
@@ -2342,9 +2342,7 @@ static void ib_sa_add_one(struct ib_device *device)
 	s = rdma_start_port(device);
 	e = rdma_end_port(device);
 
-	sa_dev = kzalloc(sizeof *sa_dev +
-			 (e - s + 1) * sizeof (struct ib_sa_port),
-			 GFP_KERNEL);
+	sa_dev = kzalloc(struct_size(sa_dev, port, e - s + 1), GFP_KERNEL);
 	if (!sa_dev)
 		return;
 
-- 
2.20.1

Re: [PATCH] IB/core: Use struct_size() in kzalloc()

[Jason Gunthorpe]

On Fri, Jan 04, 2019 at 12:15:58PM -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/infiniband/core/sa_query.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)

Applied to for-next, thanks

Jason