[NET]: Do not dereference iov if length is zero

When msg_iovlen is zero we shouldn't try to dereference
msg_iov.  Right now the only thing that tries to do so
is skb_copy_and_csum_datagram_iovec.  Since the total
length should also be zero if msg_iovlen is zero, it's
sufficient to check the total length there and simply
return if it's zero.

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

1 files changed, 3 insertions, 0 deletions

diff --git a/net/core/datagram.c b/net/core/datagram.c
index cb056f476126..029b93e246b4 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -450,6 +450,9 @@ int skb_copy_and_csum_datagram_iovec(struct sk_buff *skb,
         __wsum csum;
         int chunk = skb->len - hlen;
 
+        if (!chunk)
+                return 0;
+
         /* Skip filled elements.
          * Pretty silly, look at memcpy_toiovec, though 8)
          */