[PATCH][next] tipc: Use size_add() in calls to struct_size()

[Gustavo A. R. Silva]

If, for any reason, the open-coded arithmetic causes a wraparound,
the protection that `struct_size()` adds against potential integer
overflows is defeated. Fix this by hardening call to `struct_size()`
with `size_add()`.

Fixes: e034c6d23bc4 ("tipc: Use struct_size() helper")
Signed-off-by: Gustavo A. R. Silva <gustavo...@kernel.org>
---
 net/tipc/link.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/tipc/link.c b/net/tipc/link.c
index e33b4f29f77c..d0143823658d 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -1446,7 +1446,7 @@ u16 tipc_get_gap_ack_blks(struct tipc_gap_ack_blks **ga, 
struct tipc_link *l,
                p = (struct tipc_gap_ack_blks *)msg_data(hdr);
                sz = ntohs(p->len);
                /* Sanity check */
-               if (sz == struct_size(p, gacks, p->ugack_cnt + p->bgack_cnt)) {
+               if (sz == struct_size(p, gacks, size_add(p->ugack_cnt, 
p->bgack_cnt))) {
                        /* Good, check if the desired type exists */
                        if ((uc && p->ugack_cnt) || (!uc && p->bgack_cnt))
                                goto ok;
@@ -1533,7 +1533,7 @@ static u16 tipc_build_gap_ack_blks(struct tipc_link *l, 
struct tipc_msg *hdr)
                        __tipc_build_gap_ack_blks(ga, l, ga->bgack_cnt) : 0;
 
        /* Total len */
-       len = struct_size(ga, gacks, ga->bgack_cnt + ga->ugack_cnt);
+       len = struct_size(ga, gacks, size_add(ga->bgack_cnt, ga->ugack_cnt));
        ga->len = htons(len);
        return len;
 }
-- 
2.34.1