ipv4: 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, 2 insertions, 1 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index ba4186e1dca9..1f58594d5a85 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2989,7 +2989,8 @@ struct sk_buff *tcp_tso_segment(struct sk_buff *skb,
                 swap(gso_skb->truesize, skb->truesize);
         }
 
-        delta = htonl(oldlen + (skb->tail - skb->transport_header) +
+        delta = htonl(oldlen + (skb_tail_pointer(skb) -
+                                skb_transport_header(skb)) +
                       skb->data_len);
         th->check = ~csum_fold((__force __wsum)((__force u32)th->check +
                                 (__force u32)delta));