[2.6.20.21 review 34/35] Fix datagram recvmsg NULL iov handling regression.

[Willy Tarreau <w@1wt.eu>]

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commit ef8aef55ce61fd0e2af798695f7386ac756ae1e7 in mainline

Subject: [2.6.20.21 review 34/35] [PATCH] [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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
 net/core/datagram.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

Index: 2.6/net/core/datagram.c
===================================================================
--- 2.6.orig/net/core/datagram.c
+++ 2.6/net/core/datagram.c
@@ -444,6 +444,9 @@ int skb_copy_and_csum_datagram_iovec(str
 	__wsum csum;
 	int chunk = skb->len - hlen;
 
+	if (!chunk)
+		return 0;
+
 	/* Skip filled elements.
 	 * Pretty silly, look at memcpy_toiovec, though 8)
 	 */

--