[PATCH net-next] cxgb4: smt: use struct_size() in kvzalloc()

[PATCH net-next] cxgb4: smt: use struct_size() in kvzalloc()

[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 = kvzalloc(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 = kvzalloc(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/net/ethernet/chelsio/cxgb4/smt.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/chelsio/cxgb4/smt.c b/drivers/net/ethernet/chelsio/cxgb4/smt.c
index 7b2207a2a130..eaf1fb74689c 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/smt.c
+++ b/drivers/net/ethernet/chelsio/cxgb4/smt.c
@@ -47,8 +47,7 @@ struct smt_data *t4_init_smt(void)
 
 	smt_size = SMT_SIZE;
 
-	s = kvzalloc(sizeof(*s) + smt_size * sizeof(struct smt_entry),
-		     GFP_KERNEL);
+	s = kvzalloc(struct_size(s, smtab, smt_size), GFP_KERNEL);
 	if (!s)
 		return NULL;
 	s->smt_size = smt_size;
-- 
2.20.1

Re: [PATCH net-next] cxgb4: smt: use struct_size() in kvzalloc()

[David Miller]

From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Wed, 30 Jan 2019 18:27:44 -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 = kvzalloc(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 = kvzalloc(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.