tcp: clear icsk_backoff in tcp_write_queue_purge()

[ Upstream commit 04c03114be82194d4a4858d41dba8e286ad1787c ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 0c828aac7e0445998604e8ddf7f5da4888addd36..d0c2dbe94e21d6b1bdee35e0e200ec2af01fdc23 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1622,6 +1622,7 @@ static inline void tcp_write_queue_purge(struct sock *sk)
        tcp_clear_all_retrans_hints(tcp_sk(sk));
        tcp_init_send_head(sk);
        tcp_sk(sk)->packets_out = 0;
+       inet_csk(sk)->icsk_backoff = 0;
 }
 
 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index fd14501ac3afa8845a8896074b8a5a69d971945c..00ae9a1d44edae7e19dc52f0df8a06d8ed502937 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2347,7 +2347,6 @@ 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;