2.6.23-stable review patch.  If anyone has any objections, please let us
know.

------------------
From: Ilpo J?rvinen <[EMAIL PROTECTED]>

[TCP] MTUprobe: fix potential sk_send_head corruption

[ Upstream commit: 6e42141009ff18297fe19d19296738b742f861db ]

When the abstraction functions got added, conversion here was
made incorrectly. As a result, the skb may end up pointing
to skb which got included to the probe skb and then was freed.
For it to trigger, however, skb_transmit must fail sending as
well.

Signed-off-by: Ilpo J?rvinen <[EMAIL PROTECTED]>
Signed-off-by: David S. Miller <[EMAIL PROTECTED]>
Cc: Herbert Xu <[EMAIL PROTECTED]>
Signed-off-by: Greg Kroah-Hartman <[EMAIL PROTECTED]>

---
 include/net/tcp.h     |    3 +++
 net/ipv4/tcp_output.c |    1 -
 2 files changed, 3 insertions(+), 1 deletion(-)

--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1256,6 +1256,9 @@ static inline void tcp_insert_write_queu
                                                  struct sock *sk)
 {
        __skb_insert(new, skb->prev, skb, &sk->sk_write_queue);
+
+       if (sk->sk_send_head == skb)
+               sk->sk_send_head = new;
 }
 
 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1287,7 +1287,6 @@ static int tcp_mtu_probe(struct sock *sk
 
        skb = tcp_send_head(sk);
        tcp_insert_write_queue_before(nskb, skb, sk);
-       tcp_advance_send_head(sk, skb);
 
        TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
        TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;

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