[PATCH net 1/1] batman-adv: reject oversized global TT response buffers

From: Ruide Cao <[email protected]>

batadv_tt_prepare_tvlv_global_data() builds the allocation length for a
global TT response in 16-bit temporaries. When a remote originator
advertises a large enough global TT, the TT payload length plus the VLAN
header offset can exceed 65535 and wrap before kmalloc().

The full-table response path still uses the original TT payload length when
it fills tt_change, so the wrapped allocation is too small and
batadv_tt_prepare_tvlv_global_data() writes past the end of the heap object
before the later packet-size check runs.

Fix this by rejecting TT responses whose TVLV value length cannot fit in
the 16-bit TVLV payload length field.

Fixes: 7ea7b4a14275 ("batman-adv: make the TT CRC logic VLAN specific")
Reported-by: Yifan Wu <[email protected]>
Reported-by: Juefei Pu <[email protected]>
Co-developed-by: Yuan Tan <[email protected]>
Signed-off-by: Yuan Tan <[email protected]>
Suggested-by: Xin Liu <[email protected]>
Tested-by: Ren Wei <[email protected]>
Signed-off-by: Ruide Cao <[email protected]>
Signed-off-by: Ren Wei <[email protected]>
---
 net/batman-adv/translation-table.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index 6e95e883c2bf..05cddcf994f6 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -798,8 +798,8 @@ batadv_tt_prepare_tvlv_global_data(struct batadv_orig_node *orig_node,
 {
 	u16 num_vlan = 0;
 	u16 num_entries = 0;
-	u16 change_offset;
-	u16 tvlv_len;
+	u16 tvlv_len = 0;
+	unsigned int change_offset;
 	struct batadv_tvlv_tt_vlan_data *tt_vlan;
 	struct batadv_orig_node_vlan *vlan;
 	u8 *tt_change_ptr;
@@ -816,6 +816,11 @@ 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) {
+		*tt_len = 0;
+		goto out;
+	}
+
 	tvlv_len = *tt_len;
 	tvlv_len += change_offset;
 
-- 
2.34.1