Commit 04c03114 authored Feb 15, 2019 by Eric Dumazet Committed by David S. Miller Feb 17, 2019

tcp: clear icsk_backoff in tcp_write_queue_purge()



soukjin bae reported a crash in tcp_v4_err() handling
ICMP_DEST_UNREACH after tcp_write_queue_head(sk)
returned a NULL pointer.

Current logic should have prevented this :

  if (seq != tp->snd_una  || !icsk->icsk_retransmits ||
      !icsk->icsk_backoff || fastopen)
      break;

Problem is the write queue might have been purged
and icsk_backoff has not been cleared.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: soukjin bae <soukjin.bae@samsung.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent e928b5d6

net/ipv4/tcp.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -2528,6 +2528,7 @@ void tcp_write_queue_purge(struct sock *sk)
		sk_mem_reclaim(sk);
		tcp_clear_all_retrans_hints(tcp_sk(sk));
		tcp_sk(sk)->packets_out = 0;
		inet_csk(sk)->icsk_backoff = 0;
		}

		int tcp_disconnect(struct sock *sk, int flags)
		@@ -2576,7 +2577,6 @@ int tcp_disconnect(struct sock *sk, int flags)
		tp->write_seq += tp->max_window + 2;
		if (tp->write_seq == 0)
		tp->write_seq = 1;
		icsk->icsk_backoff = 0;
		tp->snd_cwnd = 2;
		icsk->icsk_probes_out = 0;
		tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;

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