ipv6: Correct comparisons and calculations using skb->tail and skb-transport_header

This corrects an regression introduced by "net: Use 16bits for *_headers
fields of struct skbuff" when NET_SKBUFF_DATA_USES_OFFSET is not set. In
that case skb->tail will be a pointer whereas skb->transport_header
will be an offset from head. This is corrected by using wrappers that
ensure that comparisons and calculations are always made using pointers.

Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 2 deletions

diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index bfa6cc36ef2a..72c8bfe06bb4 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -1409,8 +1409,9 @@ static void mld_sendpack(struct sk_buff *skb)
         idev = __in6_dev_get(skb->dev);
         IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_OUT, skb->len);
 
-        payload_len = (skb->tail - skb->network_header) - sizeof(*pip6);
-        mldlen = skb->tail - skb->transport_header;
+        payload_len = (skb_tail_pointer(skb) - skb_network_header(skb)) -
+                sizeof(*pip6);
+        mldlen = skb_tail_pointer(skb) - skb_transport_header(skb);
         pip6->payload_len = htons(payload_len);
 
         pmr->mld2r_cksum = csum_ipv6_magic(&pip6->saddr, &pip6->daddr, mldlen,