[PATCH net-next] net/sched: use struct_size() helper

[PATCH net-next] net/sched: use struct_size() helper

[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 = alloc(size, GFP_KERNEL)

Instead of leaving these open-coded and prone to type mistakes, we can
now use the new struct_size() helper:

size = struct_size(instance, entry, count);
instance = alloc(size, GFP_KERNEL)

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 net/sched/act_pedit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
index 2b372a06b432..3663d3b615a4 100644
--- a/net/sched/act_pedit.c
+++ b/net/sched/act_pedit.c
@@ -406,7 +406,7 @@ static int tcf_pedit_dump(struct sk_buff *skb, struct tc_action *a,
 	struct tcf_t t;
 	int s;
 
-	s = sizeof(*opt) + p->tcfp_nkeys * sizeof(struct tc_pedit_key);
+	s = struct_size(opt, keys, p->tcfp_nkeys);
 
 	/* netlink spinlocks held above us - must use ATOMIC */
 	opt = kzalloc(s, GFP_ATOMIC);
-- 
2.20.1

Re: [PATCH net-next] net/sched: use struct_size() helper

[David Miller]

From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Thu, 7 Feb 2019 19:02:52 -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 = alloc(size, GFP_KERNEL)
> 
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
> 
> size = struct_size(instance, entry, count);
> instance = alloc(size, GFP_KERNEL)
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

Applied.