[PATCH net-next] ipvs: Use struct_size() helper

["Gustavo A. R. Silva" <gustavo@xxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxx>
---
 net/netfilter/ipvs/ip_vs_ctl.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index 7d6318664eb2..bcd9112f47d9 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -2734,8 +2734,7 @@ do_ip_vs_get_ctl(struct sock *sk, int cmd, void __user 
*user, int *len)
                int size;
 
                get = (struct ip_vs_get_services *)arg;
-               size = sizeof(*get) +
-                       sizeof(struct ip_vs_service_entry) * get->num_services;
+               size = struct_size(get, entrytable, get->num_services);
                if (*len != size) {
                        pr_err("length: %u != %u\n", *len, size);
                        ret = -EINVAL;
@@ -2776,8 +2775,7 @@ do_ip_vs_get_ctl(struct sock *sk, int cmd, void __user 
*user, int *len)
                int size;
 
                get = (struct ip_vs_get_dests *)arg;
-               size = sizeof(*get) +
-                       sizeof(struct ip_vs_dest_entry) * get->num_dests;
+               size = struct_size(get, entrytable, get->num_dests);
                if (*len != size) {
                        pr_err("length: %u != %u\n", *len, size);
                        ret = -EINVAL;
-- 
2.20.1