netpoll: fix rx_hook() interface by passing the skb

Right now skb->data is passed to rx_hook() even if the skb
has not been linearised and without giving rx_hook() a way
to linearise it.

Change the rx_hook() interface and make it accept the skb
and the offset to the UDP payload as arguments. rx_hook() is
also renamed to rx_skb_hook() to ensure that out of the tree
users notice the API change.

In this way any rx_skb_hook() implementation can perform all
the needed operations to properly (and safely) access the
skb data.

Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 21 insertions, 15 deletions

diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index f3c7c24bec1c..fbfdb9d8d3a7 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -24,7 +24,8 @@ struct netpoll {
         struct net_device *dev;
         char dev_name[IFNAMSIZ];
         const char *name;
-        void (*rx_hook)(struct netpoll *, int, char *, int);
+        void (*rx_skb_hook)(struct netpoll *np, int source, struct sk_buff *skb,
+                            int offset, int len);
 
         union inet_addr local_ip, remote_ip;
         bool ipv6;
@@ -41,7 +42,7 @@ struct netpoll_info {
         unsigned long rx_flags;
         spinlock_t rx_lock;
         struct semaphore dev_lock;
-        struct list_head rx_np; /* netpolls that registered an rx_hook */
+        struct list_head rx_np; /* netpolls that registered an rx_skb_hook */
 
         struct sk_buff_head neigh_tx; /* list of neigh requests to reply to */
         struct sk_buff_head txq;
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index fc75c9e461b8..8f971990677c 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -636,8 +636,9 @@ static void netpoll_neigh_reply(struct sk_buff *skb, struct netpoll_info *npinfo
 
                         netpoll_send_skb(np, send_skb);
 
-                        /* If there are several rx_hooks for the same address,
-                           we're fine by sending a single reply */
+                        /* If there are several rx_skb_hooks for the same
+                         * address we're fine by sending a single reply
+                         */
                         break;
                 }
                 spin_unlock_irqrestore(&npinfo->rx_lock, flags);
@@ -719,8 +720,9 @@ static void netpoll_neigh_reply(struct sk_buff *skb, struct netpoll_info *npinfo
 
                         netpoll_send_skb(np, send_skb);
 
-                        /* If there are several rx_hooks for the same address,
-                           we're fine by sending a single reply */
+                        /* If there are several rx_skb_hooks for the same
+                         * address, we're fine by sending a single reply
+                         */
                         break;
                 }
                 spin_unlock_irqrestore(&npinfo->rx_lock, flags);
@@ -756,11 +758,12 @@ static bool pkt_is_ns(struct sk_buff *skb)
 
 int __netpoll_rx(struct sk_buff *skb, struct netpoll_info *npinfo)
 {
-        int proto, len, ulen;
-        int hits = 0;
+        int proto, len, ulen, data_len;
+        int hits = 0, offset;
         const struct iphdr *iph;
         struct udphdr *uh;
         struct netpoll *np, *tmp;
+        uint16_t source;
 
         if (list_empty(&npinfo->rx_np))
                 goto out;
@@ -820,7 +823,10 @@ int __netpoll_rx(struct sk_buff *skb, struct netpoll_info *npinfo)
 
                 len -= iph->ihl*4;
                 uh = (struct udphdr *)(((char *)iph) + iph->ihl*4);
+                offset = (unsigned char *)(uh + 1) - skb->data;
                 ulen = ntohs(uh->len);
+                data_len = skb->len - offset;
+                source = ntohs(uh->source);
 
                 if (ulen != len)
                         goto out;
@@ -834,9 +840,7 @@ int __netpoll_rx(struct sk_buff *skb, struct netpoll_info *npinfo)
                         if (np->local_port && np->local_port != ntohs(uh->dest))
                                 continue;
 
-                        np->rx_hook(np, ntohs(uh->source),
-                                       (char *)(uh+1),
-                                       ulen - sizeof(struct udphdr));
+                        np->rx_skb_hook(np, source, skb, offset, data_len);
                         hits++;
                 }
         } else {
@@ -859,7 +863,10 @@ int __netpoll_rx(struct sk_buff *skb, struct netpoll_info *npinfo)
                 if (!pskb_may_pull(skb, sizeof(struct udphdr)))
                         goto out;
                 uh = udp_hdr(skb);
+                offset = (unsigned char *)(uh + 1) - skb->data;
                 ulen = ntohs(uh->len);
+                data_len = skb->len - offset;
+                source = ntohs(uh->source);
                 if (ulen != skb->len)
                         goto out;
                 if (udp6_csum_init(skb, uh, IPPROTO_UDP))
@@ -872,9 +879,7 @@ int __netpoll_rx(struct sk_buff *skb, struct netpoll_info *npinfo)
                         if (np->local_port && np->local_port != ntohs(uh->dest))
                                 continue;
 
-                        np->rx_hook(np, ntohs(uh->source),
-                                       (char *)(uh+1),
-                                       ulen - sizeof(struct udphdr));
+                        np->rx_skb_hook(np, source, skb, offset, data_len);
                         hits++;
                 }
 #endif
@@ -1062,7 +1067,7 @@ int __netpoll_setup(struct netpoll *np, struct net_device *ndev, gfp_t gfp)
 
         npinfo->netpoll = np;
 
-        if (np->rx_hook) {
+        if (np->rx_skb_hook) {
                 spin_lock_irqsave(&npinfo->rx_lock, flags);
                 npinfo->rx_flags |= NETPOLL_RX_ENABLED;
                 list_add_tail(&np->rx, &npinfo->rx_np);