linux-kernel - [PATCH net] bridge: fix igmpv3 / mldv2 report parsing

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Message-Id: <1441989588-26312-1-git-send-email-linus.luessing@c0d3.blue>
Date:	Fri, 11 Sep 2015 18:39:48 +0200
From:	Linus Lüssing <linus.luessing@...3.blue>
To:	netdev@...r.kernel.org
Cc:	"David S. Miller" <davem@...emloft.net>,
	Stephen Hemminger <stephen@...workplumber.org>,
	bridge@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Tobias Powalowski <tobias.powalowski@...glemail.com>,
	Linus Lüssing <linus.luessing@...3.blue>
Subject: [PATCH net] bridge: fix igmpv3 / mldv2 report parsing

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 <tobias.powalowski@...glemail.com>
Tested-by: Tobias Powalowski <tobias.powalowski@...glemail.com>
Signed-off-by: Linus Lüssing <linus.luessing@...3.blue>
---
 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 66efdc2..480b3de 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1006,7 +1006,7 @@ 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);
@@ -1067,7 +1067,7 @@ 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;
-- 
1.7.10.4

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