4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Yuchung Cheng ycheng@google.com
[ Upstream commit b2b7af861122a0c0f6260155c29a1b2e594cd5b5 ]
TCP loss probe timer may fire when the retranmission queue is empty but has a non-zero tp->packets_out counter. tcp_send_loss_probe will call tcp_rearm_rto which triggers NULL pointer reference by fetching the retranmission queue head in its sub-routines.
Add a more detailed warning to help catch the root cause of the inflight accounting inconsistency.
Reported-by: Rafael Tinoco rafael.tinoco@linaro.org Signed-off-by: Yuchung Cheng ycheng@google.com Signed-off-by: Eric Dumazet edumazet@google.com Signed-off-by: Neal Cardwell ncardwell@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/tcp_output.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
--- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2263,14 +2263,18 @@ void tcp_send_loss_probe(struct sock *sk skb = tcp_write_queue_tail(sk); }
+ if (unlikely(!skb)) { + WARN_ONCE(tp->packets_out, + "invalid inflight: %u state %u cwnd %u mss %d\n", + tp->packets_out, sk->sk_state, tp->snd_cwnd, mss); + inet_csk(sk)->icsk_pending = 0; + return; + } + /* At most one outstanding TLP retransmission. */ if (tp->tlp_high_seq) goto rearm_timer;
- /* Retransmit last segment. */ - if (WARN_ON(!skb)) - goto rearm_timer; - if (skb_still_in_host_queue(sk, skb)) goto rearm_timer;