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 c3f4f6a9e6c3a34074dbc9149a5ed0b53eb26159..fed2a78fb8cb66587e3461cfa5336e7a1d928211 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1526,6 +1526,7 @@ static inline void tcp_write_queue_purge(struct sock *sk)
                sk_wmem_free_skb(sk, skb);
        sk_mem_reclaim(sk);
        tcp_clear_all_retrans_hints(tcp_sk(sk));
+       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 9de77d946f5a819e8be2758da8ba0f59fe2eefd9..2ededb32b7545f304c4a0dc9966fab33efd3746d 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2292,7 +2292,6 @@ 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->packets_out = 0;