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>

3 files changed, 5 insertions, 3 deletions

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 562efd91f457..5d0d379b0152 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -503,7 +503,8 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
         iph = ip_hdr(skb_in);
 
         if ((u8 *)iph < skb_in->head ||
-            (skb_in->network_header + sizeof(*iph)) > skb_in->tail)
+            (skb_network_header(skb_in) + sizeof(*iph)) >
+            skb_tail_pointer(skb_in))
                 goto out;
 
         /*
diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index d8c232794bcb..450f625361e4 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -363,7 +363,7 @@ static struct sk_buff *igmpv3_newpack(struct net_device *dev, int size)
 static int igmpv3_sendpack(struct sk_buff *skb)
 {
         struct igmphdr *pig = igmp_hdr(skb);
-        const int igmplen = skb->tail - skb->transport_header;
+        const int igmplen = skb_tail_pointer(skb) - skb_transport_header(skb);
 
         pig->csum = ip_compute_csum(igmp_hdr(skb), igmplen);
 
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));