Subject: batctl: tcpdump: Add missing ICMPv6 Neighbor Advert length check
From: Sven Eckelmann <[email-masked]>
Date: Sat, 27 Jan 2024 13:49:02 +0100

dump_ipv6() is doing a length check for the original ICMPv6 header length.
But the neighbor advertisement (which is also handled by this function) is
accessed without doing an additional length check. So it is possible that
it tries to read outside of the received data.

Fixes: 35b37756f4a3 ("add IPv6 support to tcpdump parser")
Cc: Marco Dalla Torre <[email-masked]>
Signed-off-by: Sven Eckelmann <[email-masked]>
Origin: upstream, https://git.open-mesh.org/batctl.git/commit/da75747d435ca8a32a74895655a1d5bff8b7709b

--- a/tcpdump.c
+++ b/tcpdump.c
@@ -611,6 +611,8 @@ static void dump_ipv6(unsigned char *pac
 			       nd_nas_target, buff_len);
 			break;
 		case ND_NEIGHBOR_ADVERT:
+			LEN_CHECK((size_t)buff_len - (size_t)(sizeof(struct ip6_hdr)),
+				  sizeof(*nd_advert), "ICMPv6 Neighbor Advertisement");
 			nd_advert = (struct nd_neighbor_advert *)icmphdr;
 			inet_ntop(AF_INET6, &(nd_advert->nd_na_target),
 				  nd_nas_target, 40);