[PATCH net-next 1/8] tcp: exit if nothing to retransmit on RTO timeout

[Yuchung Cheng]

Previously TCP only warns if its RTO timer fires and the
retransmission queue is empty, but it'll cause null pointer
reference later on. It's better to avoid such catastrophic failure
and simply exit with a warning.

Signed-off-by: Yuchung Cheng <ych...@google.com>
Signed-off-by: Eric Dumazet <eduma...@google.com>
Reviewed-by: Neal Cardwell <ncardw...@google.com>
Reviewed-by: Soheil Hassas Yeganeh <soh...@google.com>
---
 net/ipv4/tcp_timer.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 71a29e9c0620..e7d09e3705b8 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -443,10 +443,8 @@ void tcp_retransmit_timer(struct sock *sk)
                 */
                return;
        }
-       if (!tp->packets_out)
-               goto out;
-
-       WARN_ON(tcp_rtx_queue_empty(sk));
+       if (!tp->packets_out || WARN_ON_ONCE(tcp_rtx_queue_empty(sk)))
+               return;
 
        tp->tlp_high_seq = 0;
 
-- 
2.20.1.97.g81188d93c3-goog