[PATCH 4/5] batman-adv: Fix incorrect offset in batadv_tt_tvlv_ogm_handler_v1()

[Simon Wunderlich]

From: Remi Pommarel <r...@triplefau.lt>

Since commit 4436df478860 ("batman-adv: Add flex array to struct
batadv_tvlv_tt_data"), the introduction of batadv_tvlv_tt_data's flex
array member in batadv_tt_tvlv_ogm_handler_v1() put tt_changes at
invalid offset. Those TT changes are supposed to be filled from the end
of batadv_tvlv_tt_data structure (including vlan_data flexible array),
but only the flex array size is taken into account missing completely
the size of the fixed part of the structure itself.

Fix the tt_change offset computation by using struct_size() instead of
flex_array_size() so both flex array member and its container structure
sizes are taken into account.

Cc: sta...@vger.kernel.org
Fixes: 4436df478860 ("batman-adv: Add flex array to struct batadv_tvlv_tt_data")
Signed-off-by: Remi Pommarel <r...@triplefau.lt>
Signed-off-by: Sven Eckelmann <s...@narfation.org>
Signed-off-by: Simon Wunderlich <s...@simonwunderlich.de>
---
 net/batman-adv/translation-table.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/net/batman-adv/translation-table.c 
b/net/batman-adv/translation-table.c
index 760d51fdbdf6..7d5de4cbb814 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -3959,23 +3959,21 @@ static void batadv_tt_tvlv_ogm_handler_v1(struct 
batadv_priv *bat_priv,
        struct batadv_tvlv_tt_change *tt_change;
        struct batadv_tvlv_tt_data *tt_data;
        u16 num_entries, num_vlan;
-       size_t flex_size;
+       size_t tt_data_sz;
 
        if (tvlv_value_len < sizeof(*tt_data))
                return;
 
        tt_data = tvlv_value;
-       tvlv_value_len -= sizeof(*tt_data);
-
        num_vlan = ntohs(tt_data->num_vlan);
 
-       flex_size = flex_array_size(tt_data, vlan_data, num_vlan);
-       if (tvlv_value_len < flex_size)
+       tt_data_sz = struct_size(tt_data, vlan_data, num_vlan);
+       if (tvlv_value_len < tt_data_sz)
                return;
 
        tt_change = (struct batadv_tvlv_tt_change *)((void *)tt_data
-                                                    + flex_size);
-       tvlv_value_len -= flex_size;
+                                                    + tt_data_sz);
+       tvlv_value_len -= tt_data_sz;
 
        num_entries = batadv_tt_entries(tvlv_value_len);
 
-- 
2.39.5