[9610] tcp: clear tp->packets_out when purging write queue

Clear tp->packets_out when purging the write queue, otherwise
tcp_rearm_rto() mistakenly assumes TCP write queue is not empty.
This results in NULL pointer dereference.

Also, remove the redundant `tp->packets_out = 0` from
tcp_disconnect(), since tcp_disconnect() calls
tcp_write_queue_purge().

Change-Id: If7e959a4adf6a830ff551bcf2452f15dcb7ccdab
Fixes: a27fd7a8ed38 (tcp: purge write queue upon RST)
Reported-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Reported-by: Sami Farin <hvtaifwkbgefbaei@gmail.com>
Tested-by: Sami Farin <hvtaifwkbgefbaei@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index f99d17c9540ba2ad8f4f1356fb81d9c6d736d0a3..71082ba003d7360b7ec2b99c377134fb9ab7a5c8 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1617,6 +1617,7 @@ static inline void tcp_write_queue_purge(struct sock *sk)
        sk_mem_reclaim(sk);
        tcp_clear_all_retrans_hints(tcp_sk(sk));
        tcp_init_send_head(sk);
+       tcp_sk(sk)->packets_out = 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 38b9a6276a9de826293ce918c23e0ac0302e6a83..4dda8d301802e107e7da0fc717f428e30a548fe4 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2354,7 +2354,6 @@ int tcp_disconnect(struct sock *sk, int flags)
        icsk->icsk_backoff = 0;
        tp->snd_cwnd = 2;
        icsk->icsk_probes_out = 0;
-       tp->packets_out = 0;
        tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
        tp->snd_cwnd_cnt = 0;
        tp->window_clamp = 0;