net, ipv4, ipv6: Correct assignment of skb->network_header to skb->tail

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 however skb->network_header is now
an offset.

This patch corrects the problem by adding a wrapper to return skb tail as
an offset regardless of the value of NET_SKBUFF_DATA_USES_OFFSET. It seems
that skb->tail that this offset may be more than 64k and some care has been
taken to treat such cases as an error.

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

2 files changed, 22 insertions, 3 deletions

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 37deedd48bcc..688517c7ff17 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -676,6 +676,8 @@ static void netpoll_neigh_reply(struct sk_buff *skb, struct netpoll_info *npinfo
 
                 spin_lock_irqsave(&npinfo->rx_lock, flags);
                 list_for_each_entry_safe(np, tmp, &npinfo->rx_np, rx) {
+                        unsigned long tail_offset;
+
                         if (!ipv6_addr_equal(daddr, &np->local_ip.in6))
                                 continue;
 
@@ -700,7 +702,12 @@ static void netpoll_neigh_reply(struct sk_buff *skb, struct netpoll_info *npinfo
                         hdr->saddr = *saddr;
                         hdr->daddr = *daddr;
 
-                        send_skb->transport_header = send_skb->tail;
+                        tail_offset = skb_tail_offset(skb);
+                        if (tail_offset > 0xffff) {
+                                kfree_skb(send_skb);
+                                continue;
+                        }
+                        skb_set_network_header(send_skb, tail_offset);
                         skb_put(send_skb, size);
 
                         icmp6h = (struct icmp6hdr *)skb_transport_header(skb);
diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index 795498fd4587..d2ede89662be 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -2642,6 +2642,7 @@ static struct sk_buff *fill_packet_ipv4(struct net_device *odev,
         __be16 *svlan_tci = NULL;                /* Encapsulates priority and SVLAN ID */
         __be16 *svlan_encapsulated_proto = NULL; /* packet type ID field (or len) for SVLAN tag */
         u16 queue_map;
+        unsigned long tail_offset;
 
         if (pkt_dev->nr_labels)
                 protocol = htons(ETH_P_MPLS_UC);
@@ -2708,7 +2709,12 @@ static struct sk_buff *fill_packet_ipv4(struct net_device *odev,
                 *vlan_encapsulated_proto = htons(ETH_P_IP);
         }
 
-        skb->network_header = skb->tail;
+        tail_offset = skb_tail_offset(skb);
+        if (tail_offset > 0xffff) {
+                kfree_skb(skb);
+                return NULL;
+        }
+        skb_set_network_header(skb, tail_offset);
         skb->transport_header = skb->network_header + sizeof(struct iphdr);
         skb_put(skb, sizeof(struct iphdr) + sizeof(struct udphdr));
         skb_set_queue_mapping(skb, queue_map);
@@ -2775,6 +2781,7 @@ static struct sk_buff *fill_packet_ipv6(struct net_device *odev,
         __be16 *svlan_tci = NULL;                /* Encapsulates priority and SVLAN ID */
         __be16 *svlan_encapsulated_proto = NULL; /* packet type ID field (or len) for SVLAN tag */
         u16 queue_map;
+        unsigned long tail_offset;
 
         if (pkt_dev->nr_labels)
                 protocol = htons(ETH_P_MPLS_UC);
@@ -2822,7 +2829,12 @@ static struct sk_buff *fill_packet_ipv6(struct net_device *odev,
                 *vlan_encapsulated_proto = htons(ETH_P_IPV6);
         }
 
-        skb->network_header = skb->tail;
+        tail_offset = skb_tail_offset(skb);
+        if (tail_offset > 0xffff) {
+                kfree_skb(skb);
+                return NULL;
+        }
+        skb_set_network_header(skb, tail_offset);
         skb->transport_header = skb->network_header + sizeof(struct ipv6hdr);
         skb_put(skb, sizeof(struct ipv6hdr) + sizeof(struct udphdr));
         skb_set_queue_mapping(skb, queue_map);