[PATCH net-next] mlxsw: spectrum: acl: Use struct_size() in kzalloc()

[PATCH net-next] mlxsw: spectrum: acl: 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;
    struct boo entry[];
};

size = sizeof(struct foo) + count * sizeof(struct boo);
instance = kzalloc(size, 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)

Notice that, in this case, variable alloc_size is not necessary, hence
it is removed.

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_keys.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_keys.c b/drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_keys.c
index df78d23b3ec3..cb3e663b1d37 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_keys.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_keys.c
@@ -236,12 +236,10 @@ mlxsw_afk_key_info_create(struct mlxsw_afk *mlxsw_afk,
 			  struct mlxsw_afk_element_usage *elusage)
 {
 	struct mlxsw_afk_key_info *key_info;
-	size_t alloc_size;
 	int err;
 
-	alloc_size = sizeof(*key_info) +
-		     sizeof(key_info->blocks[0]) * mlxsw_afk->max_blocks;
-	key_info = kzalloc(alloc_size, GFP_KERNEL);
+	key_info = kzalloc(struct_size(key_info, blocks, mlxsw_afk->max_blocks),
+			   GFP_KERNEL);
 	if (!key_info)
 		return ERR_PTR(-ENOMEM);
 	err = mlxsw_afk_picker(mlxsw_afk, key_info, elusage);
-- 
2.20.1

Re: [PATCH net-next] mlxsw: spectrum: acl: Use struct_size() in kzalloc()

[Ido Schimmel]

On Mon, Feb 25, 2019 at 01:01:32PM -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;
>     struct boo entry[];
> };
> 
> size = sizeof(struct foo) + count * sizeof(struct boo);
> instance = kzalloc(size, 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)
> 
> Notice that, in this case, variable alloc_size is not necessary, hence
> it is removed.
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

Reviewed-by: Ido Schimmel <idosch@mellanox.com>

Thanks

Re: [PATCH net-next] mlxsw: spectrum: acl: Use struct_size() in kzalloc()

[David Miller]

From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Mon, 25 Feb 2019 13:01:32 -0600

> 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;
>     struct boo entry[];
> };
> 
> size = sizeof(struct foo) + count * sizeof(struct boo);
> instance = kzalloc(size, 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)
> 
> Notice that, in this case, variable alloc_size is not necessary, hence
> it is removed.
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

Applied, thanks.

Re: [PATCH net-next] mlxsw: spectrum: acl: Use struct_size() in kzalloc()

[Jiri Pirko]

Mon, Feb 25, 2019 at 08:01:32PM CET, gustavo@embeddedor.com 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;
>    struct boo entry[];
>};
>
>size = sizeof(struct foo) + count * sizeof(struct boo);
>instance = kzalloc(size, 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)
>
>Notice that, in this case, variable alloc_size is not necessary, hence
>it is removed.
>
>This code was detected with the help of Coccinelle.
>
>Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

Acked-by: Jiri Pirko <jiri@mellanox.com>