[PATCH batadv 5/8] batman-adv: tt: reject oversized local TVLV buffers

[Sven Eckelmann <sven@narfation.org>]

The commit 3a359bf5c61d ("batman-adv: reject oversized global TT response
buffers") added a check to ensure that a global return buffer size can be
stored in an u16. The same buffer handling also exists for the local data
buffer but was not touched.

A similar check should be also be in place for the local TVLV buffer. It
doesn't have the similar attack surface because it is only generated from
locally discovered MAC addresses but the dynamic nature could still cause
temporarily to large buffers.

Cc: stable@kernel.org
Fixes: 7ea7b4a14275 ("batman-adv: make the TT CRC logic VLAN specific")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
 net/batman-adv/translation-table.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index 05cddcf994f6..06548dae1039 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -877,12 +877,12 @@ batadv_tt_prepare_tvlv_local_data(struct batadv_priv *bat_priv,
 {
 	struct batadv_tvlv_tt_vlan_data *tt_vlan;
 	struct batadv_meshif_vlan *vlan;
+	size_t change_offset;
 	u16 num_vlan = 0;
 	u16 vlan_entries = 0;
 	u16 total_entries = 0;
 	u16 tvlv_len;
 	u8 *tt_change_ptr;
-	int change_offset;
 
 	spin_lock_bh(&bat_priv->meshif_vlan_list_lock);
 	hlist_for_each_entry(vlan, &bat_priv->meshif_vlan_list, list) {
@@ -900,8 +900,10 @@ batadv_tt_prepare_tvlv_local_data(struct batadv_priv *bat_priv,
 	if (*tt_len < 0)
 		*tt_len = batadv_tt_len(total_entries);
 
-	tvlv_len = *tt_len;
-	tvlv_len += change_offset;
+	if (check_add_overflow(*tt_len, change_offset, &tvlv_len)) {
+		tvlv_len = 0;
+		goto out;
+	}
 
 	*tt_data = kmalloc(tvlv_len, GFP_ATOMIC);
 	if (!*tt_data) {

-- 
2.47.3