netpoll: fix incorrect access to skb data in __netpoll_rx

__netpoll_rx() doesnt properly handle skbs with small header

pskb_may_pull() or pskb_trim_rcsum() can change skb->data, we must
reload it.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index adf84dd..5262251 100644 (file)
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -558,13 +558,14 @@ int __netpoll_rx(struct sk_buff *skb)
        if (skb_shared(skb))
                goto out;
 
-       iph = (struct iphdr *)skb->data;
        if (!pskb_may_pull(skb, sizeof(struct iphdr)))
                goto out;
+       iph = (struct iphdr *)skb->data;
        if (iph->ihl < 5 || iph->version != 4)
                goto out;
        if (!pskb_may_pull(skb, iph->ihl*4))
                goto out;
+       iph = (struct iphdr *)skb->data;
        if (ip_fast_csum((u8 *)iph, iph->ihl) != 0)
                goto out;
 
@@ -579,6 +580,7 @@ int __netpoll_rx(struct sk_buff *skb)
        if (pskb_trim_rcsum(skb, len))
                goto out;
 
+       iph = (struct iphdr *)skb->data;
        if (iph->protocol != IPPROTO_UDP)
                goto out;