From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Date: Mon, 19 Jul 2010 01:16:18 +0000 (+0000)
Subject: tcp: fix crash in tcp_xmit_retransmit_queue
X-Git-Tag: v2.6.34.2~173
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=49dcc8eb452542c4ba40d8caa6a2a544c44ede7a;p=karo-tx-linux.git

tcp: fix crash in tcp_xmit_retransmit_queue

commit 45e77d314585869dfe43c82679f7e08c9b35b898 upstream.

It can happen that there are no packets in queue while calling
tcp_xmit_retransmit_queue(). tcp_write_queue_head() then returns
NULL and that gets deref'ed to get sacked into a local var.

There is no work to do if no packets are outstanding so we just
exit early.

This oops was introduced by 08ebd1721ab8fd (tcp: remove tp->lost_out
guard to make joining diff nicer).

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Reported-by: Lennart Schulte <lennart.schulte@nets.rwth-aachen.de>
Tested-by: Lennart Schulte <lennart.schulte@nets.rwth-aachen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 3ef4adee64a3..a5cf575f1363 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2206,6 +2206,9 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
 	int mib_idx;
 	int fwd_rexmitting = 0;
 
+	if (!tp->packets_out)
+		return;
+
 	if (!tp->lost_out)
 		tp->retransmit_high = tp->snd_una;