[PATCHv2 net] bonding: fix ICMPv6 header handling when receiving IPv6 messages

[Hangbin Liu <liuhangbin@gmail.com>]

Currently, we get icmp6hdr via function icmp6_hdr(), which needs the skb
transport header to be set first. But there is no rule to ask driver set
transport header before netif_receive_skb() and bond_handle_frame(). So
we will not able to get correct icmp6hdr on some drivers.

Fix this by checking the skb length manually and getting icmp6 header based
on the IPv6 header offset.

Reported-by: Liang Li <liali@redhat.com>
Fixes: 4e24be018eb9 ("bonding: add new parameter ns_targets")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
v2: use skb_header_pointer() to get icmp6hdr as Jay suggested.
---
 drivers/net/bonding/bond_main.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index e84c49bf4d0c..4599cf340201 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -3231,12 +3231,16 @@ static int bond_na_rcv(const struct sk_buff *skb, struct bonding *bond,
 		       struct slave *slave)
 {
 	struct slave *curr_active_slave, *curr_arp_slave;
-	struct icmp6hdr *hdr = icmp6_hdr(skb);
+	const struct icmp6hdr *hdr, _hdr;
 	struct in6_addr *saddr, *daddr;
 
 	if (skb->pkt_type == PACKET_OTHERHOST ||
 	    skb->pkt_type == PACKET_LOOPBACK ||
-	    hdr->icmp6_type != NDISC_NEIGHBOUR_ADVERTISEMENT)
+	    ipv6_hdr(skb)->nexthdr != NEXTHDR_ICMP)
+		goto out;
+
+	hdr = skb_header_pointer(skb, sizeof(struct ipv6hdr), sizeof(_hdr), &_hdr);
+	if (!hdr || hdr->icmp6_type != NDISC_NEIGHBOUR_ADVERTISEMENT)
 		goto out;
 
 	saddr = &ipv6_hdr(skb)->saddr;
-- 
2.38.1