[055/165] tcp: fix crash in tcp_xmit_retransmit_queue

From: Greg KH
Date: Fri Jul 30 2010 - 15:08:19 EST

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


From: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxx>

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@xxxxxxxxxxx>
Reported-by: Lennart Schulte <lennart.schulte@xxxxxxxxxxxxxxxxxxx>
Tested-by: Lennart Schulte <lennart.schulte@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

net/ipv4/tcp_output.c | 3 +++
1 file changed, 3 insertions(+)

--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2037,6 +2037,9 @@ void tcp_xmit_retransmit_queue(struct so
int mib_idx;
int fwd_rexmitting = 0;

+ if (!tp->packets_out)
+ return;
if (!tp->lost_out)
tp->retransmit_high = tp->snd_una;

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