From: Eric Dumazet <edumazet@google.com>
Date: Fri, 15 Feb 2019 21:36:20 +0000 (-0800)
Subject: tcp: clear icsk_backoff in tcp_write_queue_purge()
X-Git-Tag: v3.18.136~10
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=191d1615f20622f3ab0179d5db92ec30aca3340c;p=thirdparty%2Fkernel%2Fstable.git

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 bca27ae031e2a..3eb375704dd70 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1379,6 +1379,7 @@ 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 e2a545f3db687..eb6b60691330d 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2258,7 +2258,6 @@ int tcp_disconnect(struct sock *sk, int flags)
 	tp->srtt_us = 0;
 	if ((tp->write_seq += tp->max_window + 2) == 0)
 		tp->write_seq = 1;
-	icsk->icsk_backoff = 0;
 	tp->snd_cwnd = 2;
 	icsk->icsk_probes_out = 0;
 	tp->packets_out = 0;