[UDP]: Avoid repeated counting of checksum errors due to peeking

Currently it is possible for two processes to peek on the same socket
and end up incrementing the error counter twice for the same packet.

This patch fixes it by making skb_kill_datagram return whether it
succeeded in unlinking the packet and only incrementing the counter
if it did.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 3 deletions

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index d0283b7fcec5..f50de5d5218d 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -899,9 +899,8 @@ out:
         return err;
 
 csum_copy_err:
-        UDP_INC_STATS_USER(UDP_MIB_INERRORS, is_udplite);
-
-        skb_kill_datagram(sk, skb, flags);
+        if (!skb_kill_datagram(sk, skb, flags))
+                UDP_INC_STATS_USER(UDP_MIB_INERRORS, is_udplite);
 
         if (noblock)
                 return -EAGAIN;