Commit a15d56a6 authored by Sven Eckelmann's avatar Sven Eckelmann Committed by Simon Wunderlich
Browse files

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: ef261577 ("batman-adv: tvlv - basic infrastructure")
Reported-by: default avatar <syzbot+355cab184197dbbfa384@syzkaller.appspotmail.com>
Signed-off-by: default avatarSven Eckelmann <sven@narfation.org>
Acked-by: default avatarAntonio Quartulli <a@unstable.cc>
Signed-off-by: default avatarSimon Wunderlich <sw@simonwunderlich.de>
parent 3ee1bb7a

net/batman-adv/bat_iv_ogm.c

+13 −7
Original line number Diff line number Diff line
@@ -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;

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