bridge: mcast: Fix MLD2 Report IPv6 payload length check

Commit e57f61858b7c ("net: bridge: mcast: fix stale nsrcs pointer in
igmp3/mld2 report handling") introduced a bug in the IPv6 header payload
length check which would potentially lead to rejecting a valid MLD2 Report:

The check needs to take into account the 2 bytes for the "Number of
Sources" field in the "Multicast Address Record" before reading it.
And not the size of a pointer to this field.

Fixes: e57f61858b7c ("net: bridge: mcast: fix stale nsrcs pointer in igmp3/mld2 report handling")
Acked-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 83490bf..4c4a93a 100644 (file)
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1007,7 +1007,7 @@ static int br_ip6_multicast_mld2_report(struct net_bridge *br,
                nsrcs_offset = len + offsetof(struct mld2_grec, grec_nsrcs);
 
                if (skb_transport_offset(skb) + ipv6_transport_len(skb) <
-                   nsrcs_offset + sizeof(_nsrcs))
+                   nsrcs_offset + sizeof(__nsrcs))
                        return -EINVAL;
 
                _nsrcs = skb_header_pointer(skb, nsrcs_offset,