From: Jiri Olsa <jolsa@redhat.com>
Date: Thu, 16 Sep 2010 14:15:39 -0400
Subject: [net] ipv4: prevent chained skb destined to UFO device
Message-id: <1284646539-8644-1-git-send-email-jolsa@redhat.com>
Patchwork-id: 28258
O-Subject: [PATCH RHEL5] BZ 633450 ipv4 - ufo: prevent generation of chained skb
	destined to UFO device
Bugzilla: 633450
RH-Acked-by: Jarod Wilson <jarod@redhat.com>
RH-Acked-by: Neil Horman <nhorman@redhat.com>
RH-Acked-by: David S. Miller <davem@redhat.com>
RH-Acked-by: Thomas Graf <tgraf@redhat.com>

Bugzilla: 633450
Bug 633450 - [RHEL5] connectathon test panics KVM guests on RHEL6 host
https://bugzilla.redhat.com/show_bug.cgi?id=633450

Description:
============
RHEL5 is missing 1st chunk of the upstream commit, resulting in a single
skb to be queued twice in the socket write queue and causing lockup during
the socket write queue iteration later.

As virtio_net is one of the few drivers using UFO, this was caught
on the KVM connectathon test (RHEL6 as the host).

Upstream status:
================
- [IPv4] UFO: prevent generation of chained skb destined to UFO device
  commit be9164e769d57aa10b2bbe15d103edc041b9e7de
  Author: Kostya B <bkostya@hotmail.com>

Brew:
=====
https://brewweb.devel.redhat.com/taskinfo?taskID=2764898

Tested:
=======
The connectathon 'general' tests will finish correctly.

wbr,
jirka


diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index fe8464d..59f1023 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -745,23 +745,15 @@ static inline int ip_ufo_append_data(struct sock *sk,
 		skb->ip_summed = CHECKSUM_HW;
 		skb->csum = 0;
 		sk->sk_sndmsg_off = 0;
-	}
 
-	err = skb_append_datato_frags(sk,skb, getfrag, from,
-			       (length - transhdrlen));
-	if (!err) {
-		/* specify the length of each IP datagram fragment*/
+		/* specify the length of each IP datagram fragment */
 		skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
 		skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
 		__skb_queue_tail(&sk->sk_write_queue, skb);
-
-		return 0;
 	}
-	/* There is not enough support do UFO ,
-	 * so follow normal path
-	 */
-	kfree_skb(skb);
-	return err;
+
+	return skb_append_datato_frags(sk, skb, getfrag, from,
+				       (length - transhdrlen));
 }
 
 /*