[PATCH net-next] openvswitch: meter: Use struct_size() in kzalloc()

[PATCH net-next] openvswitch: meter: 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[];
};

instance = kzalloc(sizeof(struct foo) + count * sizeof(struct boo), 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>
---
 net/openvswitch/meter.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/openvswitch/meter.c b/net/openvswitch/meter.c
index c038e021a591..43849d752a1e 100644
--- a/net/openvswitch/meter.c
+++ b/net/openvswitch/meter.c
@@ -206,8 +206,7 @@ static struct dp_meter *dp_meter_create(struct nlattr **a)
 			return ERR_PTR(-EINVAL);
 
 	/* Allocate and set up the meter before locking anything. */
-	meter = kzalloc(n_bands * sizeof(struct dp_meter_band) +
-			sizeof(*meter), GFP_KERNEL);
+	meter = kzalloc(struct_size(meter, bands, n_bands), GFP_KERNEL);
 	if (!meter)
 		return ERR_PTR(-ENOMEM);
 
-- 
2.20.1

Re: [PATCH net-next] openvswitch: meter: Use struct_size() in kzalloc()

[David Miller]

From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Tue, 15 Jan 2019 15:19:17 -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[];
> };
> 
> instance = kzalloc(sizeof(struct foo) + count * sizeof(struct boo), 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>

Applied.