From b2b7af861122a0c0f6260155c29a1b2e594cd5b5 Mon Sep 17 00:00:00 2001 From: Yuchung Cheng Date: Wed, 5 Dec 2018 14:38:38 -0800 Subject: tcp: fix NULL ref in tail loss probe 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 Signed-off-by: Yuchung Cheng Signed-off-by: Eric Dumazet Signed-off-by: Neal Cardwell Signed-off-by: David S. Miller --- net/ipv4/tcp_output.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) (limited to 'net') diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 318690234758..5aa600900695 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -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; -- cgit v1.2.3-59-g8ed1b