[v2,1/2] batman-adv: Only read OGM tvlv_len after buffer len check
Commit Message
Multiple batadv_ogm_packet can be stored in an skbuff. The functions
batadv_iv_ogm_send_to_if()/batadv_iv_ogm_receive() use
batadv_iv_ogm_aggr_packet() to check if there is another additional
batadv_ogm_packet in the skb or not before they continue processing the
packet.
The length for such an OGM is BATADV_OGM_HLEN +
batadv_ogm_packet->tvlv_len. The check must first check that at least
BATADV_OGM_HLEN bytes are available before it accesses tvlv_len (which is
part of the header. Otherwise it might try read outside of the currently
available skbuff to get the content of tvlv_len.
Fixes: 0b6aa0d43767 ("batman-adv: tvlv - basic infrastructure")
Reported-by: syzbot+355cab184197dbbfa384@syzkaller.appspotmail.com
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
v2:
* change __be16 pointer parameter to const const struct batadv_ogm_packet
net/batman-adv/bat_iv_ogm.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)
Comments
Hi,
On 23/08/2019 14:34, Sven Eckelmann wrote:
> Multiple batadv_ogm_packet can be stored in an skbuff. The functions
> batadv_iv_ogm_send_to_if()/batadv_iv_ogm_receive() use
> batadv_iv_ogm_aggr_packet() to check if there is another additional
> batadv_ogm_packet in the skb or not before they continue processing the
> packet.
>
> The length for such an OGM is BATADV_OGM_HLEN +
> batadv_ogm_packet->tvlv_len. The check must first check that at least
> BATADV_OGM_HLEN bytes are available before it accesses tvlv_len (which is
> part of the header. Otherwise it might try read outside of the currently
> available skbuff to get the content of tvlv_len.
>
> Fixes: 0b6aa0d43767 ("batman-adv: tvlv - basic infrastructure")
> Reported-by: syzbot+355cab184197dbbfa384@syzkaller.appspotmail.com
> Signed-off-by: Sven Eckelmann <sven@narfation.org>
Acked-by: Antonio Quartulli <a@unstable.cc>
@@ -277,17 +277,23 @@ static u8 batadv_hop_penalty(u8 tq, const struct batadv_priv *bat_priv)
* batadv_iv_ogm_aggr_packet() - checks if there is another OGM attached
* @buff_pos: current position in the skb
* @packet_len: total length of the skb
- * @tvlv_len: tvlv length of the previously considered OGM
+ * @ogm_packet: potential OGM in buffer
*
* Return: true if there is enough space for another OGM, false otherwise.
*/
-static bool batadv_iv_ogm_aggr_packet(int buff_pos, int packet_len,
- __be16 tvlv_len)
+static bool
+batadv_iv_ogm_aggr_packet(int buff_pos, int packet_len,
+ const struct batadv_ogm_packet *ogm_packet)
{
int next_buff_pos = 0;
- next_buff_pos += buff_pos + BATADV_OGM_HLEN;
- next_buff_pos += ntohs(tvlv_len);
+ /* check if there is enough space for the header */
+ next_buff_pos += buff_pos + sizeof(*ogm_packet);
+ if (next_buff_pos > packet_len)
+ return false;
+
+ /* check if there is enough space for the optional TVLV */
+ next_buff_pos += ntohs(ogm_packet->tvlv_len);
return (next_buff_pos <= packet_len) &&
(next_buff_pos <= BATADV_MAX_AGGREGATION_BYTES);
@@ -315,7 +321,7 @@ static void batadv_iv_ogm_send_to_if(struct batadv_forw_packet *forw_packet,
/* adjust all flags and log packets */
while (batadv_iv_ogm_aggr_packet(buff_pos, forw_packet->packet_len,
- batadv_ogm_packet->tvlv_len)) {
+ batadv_ogm_packet)) {
/* we might have aggregated direct link packets with an
* ordinary base packet
*/
@@ -1704,7 +1710,7 @@ static int batadv_iv_ogm_receive(struct sk_buff *skb,
/* unpack the aggregated packets and process them one by one */
while (batadv_iv_ogm_aggr_packet(ogm_offset, skb_headlen(skb),
- ogm_packet->tvlv_len)) {
+ ogm_packet)) {
batadv_iv_ogm_process(skb, ogm_offset, if_incoming);
ogm_offset += BATADV_OGM_HLEN;