Subject: [PATCH 15/28] bridge: fix igmpv3 / mldv2 report parsing

From: Linus Lüssing <[email-masked]>
Date: Fri, 11 Sep 2015 18:39:48 +0200

[ Upstream commit c2d4fbd2163e607915cc05798ce7fb7f31117cc1 ]

With the newly introduced helper functions the skb pulling is hidden in
the checksumming function - and undone before returning to the caller.

The IGMPv3 and MLDv2 report parsing functions in the bridge still
assumed that the skb is pointing to the beginning of the IGMP/MLD
message while it is now kept at the beginning of the IPv4/6 header,
breaking the message parsing and creating packet loss.

Fixing this by taking the offset between IP and IGMP/MLD header into
account, too.

Fixes: 9afd85c9e455 ("net: Export IGMP/MLD message validation code")
Reported-by: Tobias Powalowski <[email-masked]>
Tested-by: Tobias Powalowski <[email-masked]>
Signed-off-by: Linus Lüssing <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/bridge/br_multicast.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index ff667e1..9ba383f 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -980,7 +980,7 @@ static int br_ip4_multicast_igmp3_report(struct net_bridge *br,
 
 	ih = igmpv3_report_hdr(skb);
 	num = ntohs(ih->ngrec);
-	len = sizeof(*ih);
+	len = skb_transport_offset(skb) + sizeof(*ih);
 
 	for (i = 0; i < num; i++) {
 		len += sizeof(*grec);
@@ -1035,7 +1035,7 @@ static int br_ip6_multicast_mld2_report(struct net_bridge *br,
 
 	icmp6h = icmp6_hdr(skb);
 	num = ntohs(icmp6h->icmp6_dataun.un_data16[1]);
-	len = sizeof(*icmp6h);
+	len = skb_transport_offset(skb) + sizeof(*icmp6h);
 
 	for (i = 0; i < num; i++) {
 		__be16 *nsrcs, _nsrcs;
-- 
2.1.0