3.6-stable review patch.  If anyone has any objections, please let me know.

------------------


From: Cyrill Gorcunov <redacted>

[ Upstream commit cacb6ba0f36ab14a507f4ee7697e8332899015d2 ]

We've observed that in case if UDP diag module is not
supported in kernel the netlink returns NLMSG_DONE without
notifying a caller that handler is missed.

This patch makes __inet_diag_dump to return error code instead.

So as example it become possible to detect such situation
and handle it gracefully on userspace level.

Signed-off-by: Cyrill Gorcunov <redacted>
CC: David Miller <davem@davemloft.net>
CC: Eric Dumazet <redacted>
CC: Pavel Emelyanov <redacted>
Acked-by: Pavel Emelyanov <redacted>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/inet_diag.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c

@@ -883,13 +883,16 @@ static int __inet_diag_dump(struct sk_bu
 		struct inet_diag_req_v2 *r, struct nlattr *bc)
 {
 	const struct inet_diag_handler *handler;
+	int err = 0;
 
 	handler = inet_diag_lock_handler(r->sdiag_protocol);
 	if (!IS_ERR(handler))
 		handler->dump(skb, cb, r, bc);
+	else
+		err = PTR_ERR(handler);
 	inet_diag_unlock_handler(handler);
 
-	return skb->len;
+	return err ? : skb->len;
 }
 
 static int inet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)