Linux Ethernet Bridging - Feb 2019 - [Bridge] [PATCH net-next] bridge: use struct_size() helper

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);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo at embeddedor.com>
---
 net/bridge/br_multicast.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 1fb885a33c66..4a048fd1cbea 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1018,8 +1018,7 @@ static int br_ip6_multicast_mld2_report(struct net_bridge
*br,
 		if (!nsrcs)
 			return -EINVAL;
 
-		grec_len = sizeof(*grec) +
-			   sizeof(struct in6_addr) * ntohs(*nsrcs);
+		grec_len = struct_size(grec, grec_src, ntohs(*nsrcs));
 
 		if (!ipv6_mc_may_pull(skb, len + grec_len))
 			return -EINVAL;
-- 
2.20.1

From: "Gustavo A. R. Silva" <gustavo at embeddedor.com>
Date: Thu, 7 Feb 2019 18:58:56 -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);
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo at embeddedor.com>
Applied.