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tcp: fix NULL ref in tail loss probe

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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>
This commit is contained in:
Yuchung Cheng 2018-12-05 14:38:38 -08:00 committed by David S. Miller
parent 41727549de
commit b2b7af8611
1 changed files with 7 additions and 4 deletions
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11
net/ipv4/tcp_output.c
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@ -2497,15 +2497,18 @@ void tcp_send_loss_probe(struct sock *sk)
goto rearm_timer;
}
skb = skb_rb_last(&sk->tcp_rtx_queue);
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;