[PATCH batadv-next 2/2] batman-adv: tt: replace open-coded overflow check with helper

The commit 6043a632dd06 ("batman-adv: reject oversized global TT response
buffers") introduced an open-coded check to ensure that the allocated
buffer size can be stored in a u16. The check_add_overflow() helper can
perform the addition and overflow check in one step, so use that instead.

Signed-off-by: Sven Eckelmann <[email protected]>
---
 net/batman-adv/translation-table.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index 8ab93458..72c0057b 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -840,9 +840,9 @@ batadv_tt_prepare_tvlv_global_data(struct batadv_orig_node *orig_node,
 	u16 num_vlan = 0;
 	u16 num_entries = 0;
 	u16 tvlv_len = 0;
-	unsigned int change_offset;
 	struct batadv_tvlv_tt_vlan_data *tt_vlan;
 	struct batadv_orig_node_vlan *vlan;
+	size_t change_offset;
 	u8 *tt_change_ptr;
 
 	spin_lock_bh(&orig_node->vlan_list_lock);
@@ -857,14 +857,11 @@ batadv_tt_prepare_tvlv_global_data(struct batadv_orig_node *orig_node,
 	if (*tt_len < 0)
 		*tt_len = batadv_tt_len(num_entries);
 
-	if (change_offset > U16_MAX || *tt_len > U16_MAX - change_offset) {
+	if (check_add_overflow(*tt_len, change_offset, &tvlv_len)) {
 		*tt_len = 0;
 		goto out;
 	}
 
-	tvlv_len = *tt_len;
-	tvlv_len += change_offset;
-
 	*tt_data = kmalloc(tvlv_len, GFP_ATOMIC);
 	if (!*tt_data) {
 		*tt_len = 0;

-- 
2.47.3