Subject: batctl: tcpdump: Fix missing sanity check for batman-adv header
From: Sven Eckelmann <[email-masked]>
Date: Sat, 27 Jan 2024 13:48:59 +0100

parse_eth_hdr() is assuming that every ETH_P_BATMAN ethernet packet has a
valid, minimal batman-adv header (packet_type, version, ttl) attached. But
it doesn't actually check if the received buffer has enough bytes to access
the two bytes packet_type + version. So it is possible that it tries to
read outside of the received data.

Fixes: 3bdfc388e74b ("implement simple tcpdump, first only batman packets")
Signed-off-by: Sven Eckelmann <[email-masked]>
Origin: upstream, https://git.open-mesh.org/batctl.git/commit/7ae3bdb59a7501197e12d3a7ab0d9924341e9ca8

--- a/tcpdump.c
+++ b/tcpdump.c
@@ -1068,6 +1068,9 @@ static void parse_eth_hdr(unsigned char
 			dump_vlan(packet_buff, buff_len, read_opt, time_printed);
 		break;
 	case ETH_P_BATMAN:
+		/* check for batman-adv packet_type + version */
+		LEN_CHECK(buff_len, sizeof(*eth_hdr) + 2, "BAT HEADER")
+
 		batman_ogm_packet = (struct batadv_ogm_packet *)(packet_buff + ETH_HLEN);
 
 		if ((read_opt & COMPAT_FILTER) &&