[NET]: Fix UDP checksum issue in net poll mode.

In net poll mode, the current checksum function doesn't consider the
kind of packet which is padded to reach a specific minimum length. I
believe that's the problem causing my test case failed. The following
patch fixed this issue.

Signed-off-by: Aubrey.Li <aubreylee@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 0 deletions

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index da1019451cc..4581ece48bb 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -471,6 +471,13 @@ int __netpoll_rx(struct sk_buff *skb)
         if (skb->len < len || len < iph->ihl*4)
                 goto out;
 
+        /*
+         * Our transport medium may have padded the buffer out.
+         * Now We trim to the true length of the frame.
+         */
+        if (pskb_trim_rcsum(skb, len))
+                goto out;
+
         if (iph->protocol != IPPROTO_UDP)
                 goto out;