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batman-adv: Only read OGM tvlv_len after buffer len check 

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: ef26157747 ("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>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
This commit is contained in:
Sven Eckelmann 2019-08-22 08:55:36 +02:00 committed by Simon Wunderlich
parent 3ee1bb7aae
commit a15d56a607
1 changed files with 13 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
net/batman-adv/bat_iv_ogm.c
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@ -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;